WO2025093594A1 - Electronic device that is highly reliable for a long time - Google Patents

Abstract

The invention relates to an electronic device comprising at least one printed circuit board, electronic components, electrically conductive elements and an electrically insulating housing made of polymer material. According to the invention, all the electronic components and at least some of the electrically conductive elements are partially or completely embedded in the at least one printed circuit board. Furthermore, the electrically insulating housing made of polymer material completely encapsulates without dielectric tracking the at least one printed circuit board and all the electrically conductive elements that are not already embedded in the at least one printed circuit board. The polymer material consists in its entirety or in part of a polymer of the family of the polyetherketones (PEK), of the polyaryletherketones (PAEK) or of the polyetheretherketones (PEEK).

Description

DESCRIPTION

TITLE: Highly reliable electronic device over a long period of time.

The present invention relates to a highly reliable electronic device over a long period of time.

It finds particularly interesting applications in so-called "harsh environment" fields such as aerospace, automotive, railways, medical devices (implantable or non-implantable) and all other fields for which the guarantee of a critical function performed by an electronic device must be ensured over a long period.

The unmet need can be characterized by certain characteristics of the mission profile of such a device, i.e. by the sequential description, during the lifetime of the product, of the external constraints that it may undergo. These external constraints are globally represented by an external action, i.e. the product of a duration and an exchange energy between the device and its environment. The exchange energy is characterized by the evolution of its intensity over time and by its nature, which can be mechanical, thermal, electromagnetic, chemical or mixed (simultaneous combination of several constraints of different natures, for example mechanical and thermal at the same time).

The electronic device is also characterized by internal constraints also characterized by an action that depends on the design and its use (therefore on the mission profile). The internal action can be modulated by design choices and manufacturing processes.

It is the accumulation of internal and external actions, possibly coupled, as well as design choices and manufacturing processes, which impact the reliability of an electronic device.

It is well known to those skilled in the art that the choice and sizing of electronic components respond to the same intrinsic problem and we will not deal with this in the present invention. We will simply recall that the most reliable components are chosen according to the mission profiles mentioned above, and that their intrinsic lifetimes/reliabilities are all the higher as the margins between certain critical technological thresholds and the maximum intensities of the constraints envisaged are increased. Furthermore, the manufacturing processes of these components are also keys to their intrinsic reliability and such processes require qualification and validation guaranteed by tests. In electronics, most components meeting such requirements have generally been developed for automotive applications, but they are not the only ones. This comes from the fact that automotive components meet both a requirement for operation at a high maximum temperature (greater than or equal to 125°C) and a requirement for guaranteed qualification of their intrinsic reliability.

In the context of this invention, we are particularly interested in an electronic device whose components are assembled and interconnected with each other by and on a printed circuit board (or PCB for "printed circuit board" in English) and encapsulated in a case. The printed circuit allows both to connect the electronic components with each other via a network of electrically conductive elements and to assemble them mechanically and/or thermally. There are different PCB technologies and processes depending on the environments and applications targeted. Examples include (1) the most common PCBs, based on copper conductors and an electrical and thermal insulating support made of glass fiber reinforced epoxy (FR.4) or (2) very high voltage power electronics PCBs based on copper conductors and an electrical insulating support made of alumina, which is also a relatively good thermal conductor or (3) low voltage power electronics PCBs, based on copper insulated on an aluminum substrate allowing excellent thermal conduction or (4) flexible copper-based PCBs insulated on a polyimide substrate and covered with an insulating protective layer or (5) many other PCB technologies. PCBs contribute to controlling the reliability of the electronic device with regard to internal or external actions of a mechanical and/or thermal and/or electrical and/or chemical nature.

To enhance control over internal or external electromagnetic or chemical actions, a PCB encapsulation box is sometimes also used. It is known in particular to those skilled in the art that, when developing a highly reliable electronic device over a long period, it must be placed in a hermetic box in order to protect it from internal or external chemical and electrochemical actions.

This hermetic enclosure essentially prevents the migration of pollutants or solvents to the electronic components on the PCB inside the enclosure. State-of-the-art hermetic enclosures are made of glass, ceramic, metal, or a combination of these three families of materials. The hermeticity of these enclosures is tested with a gas, typically helium, either to qualify the process according to a so-called "type" test or to control each product according to a so-called "series" test. There is a standardized test that is based on injecting helium into the enclosure during its manufacture and detecting leaks. When leaks are below a certain threshold, sufficient hermeticity is guaranteed to protect the electronic device over a long period of time.

The purpose of hermeticity is multiple. It is to prevent the penetration of pollutants or solvents into the enclosure because, over time, these pollutants and/or solvents can condense and become liquid. The presence of substances in the liquid phase, particularly those containing oxygen, accelerates oxidation-reduction phenomena that can become fatal for the electronic device. Note that these pollutants or solvents may also already be present in the enclosure when they are included, for example, in the PCB substrate or on its surface. Therefore, the use of a hermetic enclosure must be combined with precautions for cleaning, drying, and absorption of pollutants or these solvents in order to eliminate electrochemical problems regardless of the source of contamination.

Hermetic ceramic packages are known, for example aluminum oxide, or other crystals, which have the advantage of being electrically insulating and perfectly hermetic to liquids and gases. The disadvantages that explain their near absence outside of niche applications and in particular in the sectors of active implantable medical devices, or aeronautics (beyond sealed feedthrough insulators), are:

- extreme mechanical fragility,

- difficulty in shaping,

- a high cost.

The major drawback of glasses and ceramics, which are electrical insulating materials, is their extreme fragility and mass. As a result, almost all hermetic electronic device enclosures are made of metal, almost exclusively titanium, which offers an optimum in terms of cost/robustness/handling. Since titanium is also biocompatible, it is also found as a case for all highly reliable long-term active implantable medical devices (such as pacemakers or neurostimulators).

Hermetic titanium packages are known with sealed feedthroughs such as platinum/iridium alloy conductors coated with an alumina-type ceramic insulator and associated with a titanium flange. This represents almost all high-reliability electronic devices and, in any case, all long-term active implantable medical devices (>24 months) implanted in recent years. Titanium has the advantage of guaranteeing complete hermeticity to gas and liquid over the long term. The only disadvantage of titanium for certain applications, in particular for the transmission of energy and/or signals, is that it is electrically conductive and acts as an electromagnetic shield. Therefore, when one wishes to transmit energy and/or an electromagnetic signal, one must necessarily provide a device placed outside the titanium package. Typically, an antenna is placed in an epoxy header (for example) and connected to the electronics via a sealed feedthrough.

In all applications, the use of an electrically conductive hermetic enclosure poses two distinct problems. The first is that its mass is significant compared to that of the bare PCB and that it imposes a dead volume in order not to short-circuit the components placed inside. The second is that the enclosure cannot provide an electrical protection function from the environment by direct electrical isolation (users or other objects in contact). However, the trend in a critical system that requires maximizing the availability of the service provided, and using highly reliable electronic devices over a long period with double electrical insulation. We speak of an "isolated" or "IT" type grounding architecture. Thus, whatever the first fault of electrical origin, it remains confined inside the device without impacting the environment (in particular ATEX-explosive atmosphere zone) or users (in particular for implantable medical or isolated current sensors).

When an insulating box is used to control internal and external actions of chemical and electrochemical origin, then it cannot be used to control internal or external actions of chemical origin. electromagnetic. It is then possible to use electrostatic screens or electromagnetic shields on the PCB itself, which makes it possible to separate the functionalities while maximizing reliability.

To ensure an electrical insulation function, it is known to those skilled in the art to use an insulating polymer casing. This casing can perform a dual function of electrical insulation, mechanical protection, and chemical protection. When targeting an implantable application or one in contact with the skin, it must also be biocompatible.

Polymer materials are commonly used to produce PCB encapsulations, due to their ease of implementation, particularly by machining and molding. These materials are mainly elastomers, for example silicones, thermosets, for example epoxy resins or thermoplastics, for example polyetherketones (PEK). Attempts have been made for a long time to use such polymers to encapsulate a highly reliable electronic device. Systematically, the electronic devices produced have shown degraded long-term reliability due to defects of electrochemical origin. They can be used for electronic devices without the need for a guarantee of long-term reliability in a harsh chemical environment. The long-term disadvantages are as follows:

- long-term non-hermeticity due to chemical absorption phenomena by diffusion, in particular of water, which ends up causing defects by corrosion or growth of electrochemical origin,

- degradation of thermal, UV, oxidation, humidity origin, leading to the loss of original mechanical properties, and/or electrical insulation and/or the release of encapsulated particles etc.

In fact, none of these materials are able to successfully pass the helium hermeticity test. The transport of gas in the volume of a polymer material is done by chemical diffusion according to a law called Fick's law. This is a diffusion phenomenon, i.e. the migration speed varies according to the gradient of the concentration rate of the substance. When the polymer is placed in a solvent (for example water), we end up finding water molecules throughout the volume, which is characterized by a mass gain rate of the order of a few % to several tens of %. It should be noted that the material is not necessarily porous in the "mechanical" sense of the term, since penetration only occurs by chemical diffusion in gaseous form and not in liquid form. Thus, only gaseous compounds are potentially internalized and/or released. In any case, the solvent may end up in liquid form in the housing after a second condensation step. This phenomenon is accelerated by the passage of the ambient temperature below the dew point (which depends on the humidity level, for example for water approximately 5000 ppm for a temperature of 0°C and 50 OOOppm for a temperature of 37°C). Then, a few "liquid" molecular layers (from three, or approximately 1 nm) are sufficient to create an environment conducive to electrochemical phenomena. These phenomena occur mainly at the interfaces between two materials, areas subject to electrical leakage lines.

We know the document by Nathaniel Dahan, "The application of PEEK to the packaging of implantable electronic devices" Department of Medical Physics and Bioengineering University College of London, 2013, relating to studies to eliminate or slow diffusion through a polymer, either by altering its composition or by adding a conformal coating on (or inside) the housings. These tests made it possible to slow the diffusion phenomenon by a few months, but not enough to envisage a long-term application of more than two years.

Other studies have involved trying to live with the penetration of a solution, by adding a desiccant and/or a conformal coating on the printed circuit (for example a parylene), by controlling the cleaning of contaminating ions on the surface which are necessary to start the oxidation-reduction phenomena (chloride or bromide), by using electrodes made of gold or other noble metal (e.g. "electroless nickel immersion gold" in English, ENIG), by reducing the voltage gradients by moving the tracks away etc. Again, the electrochemical phenomena are slowed down but not sufficiently for a long-term application.

Thus, with the aim of reducing the electrochemical phenomena of electronic devices used in harsh environments (humidity, temperature, etc.), silicone or parylene coatings are traditionally used. The advantage of silicone coating is its low cost of purchase and removal (cold casting). Its disadvantage is its "lack of adhesion" to the printed circuit board or on electrically conductive components or elements. The silicone will become charged with solvent (water) and over the long term a film of solvent (water) will eventually form on the surface of the printed circuit board, which is called an electrical creepage line. The product's lifespan is greatly improved because the silicone has transformed electrical conduction in the volume into surface conduction. But over the long term, this does not sufficiently solve the problem.

For parylene, the observation is the same. The deposition process is different since parylene is sublimated then deposited by adsorption on the surface of the PCB. It is then condensed then polymerized to form a very thin and very uniform layer, which penetrates into all the corners of the electronic PCB and its components. Apart from the fact that the process is very expensive (because the deposition is very long when the thickness is significant), the observation is the same as for silicone... In addition to the problem of adhesion to the surface (difficulty adhering to metals, delamination by delamination), parylene presents a fragility when it is too thick: it cracks. In the long term, the failure rate by electrochemical phenomena is always too high for critical applications including implantable medical applications or in the transport sector (aeronautics, automotive, railway, etc.).

Despite all these attempts, electrochemical phenomena still appear, the action of which reduces reliability over a long period. The main electrochemical phenomena causing defects are the corrosion of electrically conductive elements (tracks/electrodes), the appearance of short circuits by dendritic growth between electrically conductive elements (tracks/electrodes), the appearance of functionally unacceptable parasitic signals (leakage currents), etc.

The present invention aims to increase the intrinsic reliability of electronic devices, including active implantable medical devices or biomedical diagnostic systems or electric current or magnetic field sensors, or other applications, over a long period.

Another aim of the invention is to increase the safety of people and property over a long period, in particular by guaranteeing electrical and/or chemical insulation through the absence of release of toxic substances. The invention also aims to reduce the cost and mass of highly reliable electronic devices, which is important to promote the development of such solutions in all areas ranging from transport (automobile, aeronautics, rail, etc.) to medicine.

At least one of the goals is achieved with an electronic device comprising at least one printed circuit board (or PCB), electronic components, electrically conductive elements and an electrically insulating housing made of polymer material.

According to the invention, all the electronic components and at least some of the electrically conductive elements are partially or totally buried in said at least one printed circuit, and the electrically insulating housing made of polymer material completely encapsulates and without electrical creepage lines said at least one printed circuit and all the electrically conductive elements which are not already partially or totally buried in said at least one printed circuit.

With the electronic device according to the invention, two envelopes are put in place, a first envelope of the printed circuit around the electronics and a second envelope which is the electrically insulating housing made of polymer material.

The first envelope is the fact of burying the electronics in the printed circuit board in such a way as to eliminate any electrical leakage line ("creepage" in English) and any clearance line ("clearance" in English). By burying, we mean the fact that the same material used as a support for the printed circuit board is also used as an insulation layer for the surface of the printed circuit board, leaving the components inside and in direct contact between the support and the insulation layer. Using the same material as the support means using a layer whose adhesion is free from surface defects (non-adhesion, delamination, etc.). The support for the printed circuit board is, for example, a fiberglass-reinforced epoxy type FR.4.

With the burial according to the invention, two electrically conductive elements of a component (track or electrode) or between components cannot be connected by a direct electrically conductive line whether in air or along a surface. In other words, for each pair of conductors in an electrical circuit, there is neither a clearance line nor an electrical creepage line.

These electrical creepage and clearance lines, when they are on the surface of a printed circuit, transform into electrical conduction lines in the presence of pollutants and/or solvents such as condensed water vapor. They can thus cause defects in the printed circuit. The electrochemical phenomena causing the defects appear in the long term with a higher probability in the presence of a polarization voltage (DC component, for "Direct Current" in English). These phenomena originate on the surface of the printed circuits and can become negligible in the absence of a DC component. The DC component can be functional (at the terminals of a capacitor, a DC power supply, etc.) or parasitic (self-generated by battery effect in the presence of a metal/metal junction).

The first envelope makes the electronics robust against surface defects but does not necessarily provide the function of mechanical protection or high-voltage double electrical insulation (or even simple insulation when one wishes to access a potential of one of the electronic components or one of the electrically conductive elements using metallized vias), nor of a biocompatible barrier in the case of medical devices. To the extent that the first envelope considerably reduces the risks of an electrical malfunction of the printed circuit due to pollutants and/or solvents, the invention provides a second envelope making it possible to provide electrical insulation and/or a biocompatible barrier and/or mechanical protection and/or a chemical barrier making the assembly compatible with a harsh environment. But advantageously according to the invention, instead of using a titanium envelope, an electrically insulating housing made of polymer material is used. Titanium has the advantage of being perfectly hermetic but the disadvantage of being electrically conductive (blocking of electromagnetic signals transmitted between the inside and the outside). Many electrically insulating polymer materials (possibly biocompatible) are known. They have the advantage of allowing the passage of electromagnetic signals but the disadvantage of being less hermetic than titanium. But this disadvantage is largely offset by the fact that the printed circuit board has become a volumetric object capable of protecting buried components from any substances that might pass through the polymer insulating material. The electronic device according to the invention allows for a sealed but non-hermetic case according to current standards. The migration of a gaseous substance by a diffusion process according to Fick's law is accepted. Thus, current helium tests become obsolete for this type of "non-hermetic" sealed case.

Another advantage of replacing the titanium case with an electrically insulating case is also to allow for a more isotropic radiation pattern of the antennas contained in the electronic device since the case does not act as an electromagnetic "screen".

With the absence of an electrical creepage line, synonymous with continuity of material all around the buried electronics, the latter is completely isolated from its chemical environment, thus guaranteeing an absence of particulate release and possible initial electrical insulation.

According to an advantageous characteristic of the invention, only the components and tracks likely to develop a voltage with a DC component beyond their electrochemical potential during use are buried in the printed circuit. A threshold of 1.5V, corresponding in particular to the electrochemical potential of gold, can be set as a decision criterion for an acceptable DC component level.

Alternatively, all electronic components and at least some of the electrically conductive elements may be buried in the printed circuit board, regardless of their constituent material. Preferably, electrically conductive elements whose potentials must be accessible outside the electronic device are not completely buried.

With burial, we ensure that no pairs of electrically conductive elements are exposed, i.e. without clearance. This means, for example, that all capacitors, diodes, transistors, voltage regulators, DC power supplies, etc. are buried. A component without a DC component, for example an inductor coil carrying an alternating current, may not be completely buried. This is for reasons of integration and space reduction, but also because of the potentials electrochemical properties intrinsic to different metals, it is however preferable to bury it as well.

According to an advantageous characteristic of the invention, the printed circuit may be a rigid-flexible printed circuit comprising a rigid part and a flexible part. The partially or totally buried electrically conductive element may be arranged inside the rigid part or inside the flexible part or between the two parts.

By "totally encapsulate" according to the invention, it is meant that all the electrically conductive elements, said at least one printed circuit and the electronic components are located inside the housing without any electrical creepage distance. When electrical access from the outside of the housing is necessary, one (or more) electrical connections can be provided to electrically connect to the outside via a sealed feedthrough. In all cases, it is possible to identify the presence of an electrical creepage distance between the inside and the outside of the electrically insulating housing by placing such a device in a solvent bath (water for example), for a time sufficient for diffusion phenomena to occur, then by measuring the insulation resistance between all the electrically conductive elements and an electrode immersed in the solvent bath. The presence of an electrical creepage distance between the inside and the outside is then synonymous with ionic type electrical conduction. The order of magnitude of a "good insulation resistance", synonymous with the absence of electrical creepage, for a device of the order of a few cm2 in surface area is several megaOhms, or even gigaOhms. Such an insulation resistance measurement operation can be carried out in the same way but between two electrically conductive elements emerging from the housing via sealed feedthroughs. The absence of creepage between each of the two conductive elements is then measured. Finally, mastery of the process presented in the invention aims to ensure, by design, the absence of electrical creepage between each pair of conductive elements supposed to be insulated from each other. Not all tests are feasible, neither in series tests nor even in type tests, so it is important to master the manufacturing process. According to one embodiment, the electronic device according to the invention may comprise at least one sealed feedthrough through a wall of the electrically insulating housing, this sealed feedthrough comprising:

- at least one electrically conductive connection having at least one part buried in the flexible part of the rigid-flexible printed circuit, this flexible part being covered with at least one electrically insulating protective finishing layer made of polymer material,

- an extension of the flexible part which surrounds the electrically conductive connection at least through the wall of the electrically insulating housing, this extension serving as an electrically insulating flange and without electrical creepage line at the interface between this flange and the electrically conductive connection.

With the invention, a part of the flexible PCB is used as a constituent element of the sealed feedthrough.

The flexible PCB allows for a sealed feedthrough as the insulating protective layer can serve as a flange that can be assembled to the insulating polymer case, for example by laser welding. This assembly can be done for example by a technique called clustering, which consists of simultaneously heating a part of the electrically insulating case and a part of the flexible PCB in order to weld them. Preferably, the heating will be carried out by a laser, which requires that the two parts to be welded (the electrically insulating case and the flexible flange of the flexible PCB) are capable of absorbing the energy of said laser.

The advantage of this technique is that it provides a relatively low-cost, highly compact sealed feedthrough. It should be noted that, after this bonding process, the insulating protective layers of the flexible PCB become an integral part of the electrically insulating enclosure.

Thus, in a preferred embodiment, it is possible to assemble the sealed feedthrough with the housing while ensuring perfect continuity of material. The advantage of using identical polymer materials makes it possible to ensure good welding between the housing and the flange, for example by ultrasound, or friction, or electromagnetic heating, or even in a preferred solution by laser welding.

The electronic device according to the invention may comprise at least one other printed circuit, the two printed circuits being electrically connected to the by means of an electrically conductive element buried inside a portion of the flexible part.

In other words, a flexible printed circuit is used to extract a potential from the buried PCB, in particular by connecting it for example to a metallized via. We can say that the electrically conductive element is partially buried since the metallized via is buried, protected by the insulators of the flexible printed circuit but remains accessible for a connection outside the PCB. This allows access to the partially buried electrically conductive element to connect two separate PCBs located inside the electronic device. After connecting the two PCBs together via these flexible PCBs, either the partially buried connection is kept, or preferably additional protection is added at the connection level, so that the assembly constitutes a new fully buried flexible-rigid PCB. The only case where we would want to keep a partially buried electrically conductive element is when the potential must be accessible outside the electrically insulating case. We will then use a sealed feedthrough to ensure the absence of electrical creepage.

According to one embodiment, the electronic device may comprise at least one sealed feedthrough through a wall of the electrically insulating housing, this sealed feedthrough comprising:

- at least one electrically conductive connection having at least one part buried in said at least one printed circuit,

- an electrically insulating flange made of polymer material made around the electrically conductive connection and without electrical creepage at the interface between this flange and the electrically conductive connection; the electrically insulating flange made of polymer material being a part of the electrically insulating housing made of polymer material.

The assembly of the electrically insulating polymeric flange of the sealed bushing and the remainder of the electrically insulating polymeric housing is described later. It is preferable that the polymeric material of the electrically insulating flange be of the same chemical nature as the polymeric material of the remainder of the electrically insulating housing. To ensure the absence of electrical creepage between an electrically conductive connection of the sealed bushing and the electrically insulating flange made of polymer material, conventional techniques of injection or compression of the polymer under high pressure, or chemical adhesion between compatible materials, are used. When the device is subjected to significant mechanical action, there are two strategies concerning the flange material. The first consists of using a rigid material, which prohibits any deformation below a certain force. This first solution is used with "conventional" high-reliability sealed bushings whose insulator is either glass or ceramic. The second solution consists of using a material with a certain flexibility, capable of absorbing the mechanical action without prohibiting mechanical deformation. This second solution is frequently used for relatively short-term reliability applications. They are sealed but not hermetic. In the long term, the problem is also the appearance of electrical creepage lines resulting from the mechanical action. Preferably, we will see that we can use a thermoplastic material which can both absorb mechanical actions and guarantee deformation without the appearance of electrical leakage lines.

Ideally, the flange of the at least one watertight feedthrough is made of the same material as the housing to facilitate its assembly, for example by laser welding. Thus, the watertight feedthrough is part of the watertight housing.

One or more sealed feedthroughs can be provided. A sealed feedthrough can be connected to an electrode, either directly or via an insulated cable.

Preferably, the sealed feedthroughs are produced separately. A sealed feedthrough may be composed of at least one electrically conductive connection and an insulating polymer flange. The production of the sealed feedthrough may be carried out using a method that guarantees the absence of electrical creepage with a very high reliability rate. In a preferred embodiment, this production is carried out by overmolding or thermoforming around the conductor with the insulating material. The overmolding conditions are defined such that long-term reliability is guaranteed for a given mission profile (temperature, pressure, mechanical stresses, etc.). In a preferred embodiment, the material used for the flange is the same material as that used for the housing. In another preferred embodiment, the connection Electrically conductive can be flexible, either made of an extremely thin track, or made of a multi-stranded conductor.

It is observed that compared to a conventional sealed feedthrough based on ceramic as an insulator and a metal flange for example, the flange here is both the object ensuring sealing, electrical insulation and material continuity. An additional function of absorbing external mechanical action is provided by the sealed feedthrough. The ceramic part has been eliminated, which reduces manufacturing costs and improves the long-term robustness of the device.

Advantageously and in addition to all of the above, at least one second conductive element may be provided in the same sealed feedthrough or in another sealed feedthrough. The two conductors may constitute a dipole capable of supporting a DC electrical voltage and conducting a DC electrical current.

According to the invention, at least one of the electrically conductive elements is contained in a multi-strand conductor covered with at least one electrically insulating protective sheath made of polymer material. This solution can be used either at the sealed feedthrough, in which case the protective sheath is also the flange and a part of the electrically insulating housing, or extend a sealed feedthrough to the outside of the electronic device. It will then be ensured that the electrically insulating protective sheath made of polymer material of the cable is assembled with the electrically insulating flange made of polymer material of the sealed feedthrough without introducing an electrical creepage distance, according to a method which is described later.

According to the invention, at least one of the electronic components of the device is a self-inductive coil intended to receive or emit information and/or energy by magnetic coupling with a device located outside the electrically insulating housing made of polymer material; the self-inductive coil being buried in said at least one printed circuit.

According to the invention, the electrically insulating housing made of polymer material contains at least one hole passing through the electrically insulating housing made of polymer material from one side to the other; the hole being made in such a way that it does not introduce any electrical creepage line. The production of this hole is made possible by the housing assembly techniques described below. The addition of a hole The ability to seal the device completely in a sealed enclosure is an attractive feature for many applications. This feature is more difficult to achieve with a titanium enclosure, so it is not found in currently available products. For example, an active implantable medical device can be easily fixed in a human body using sutures on the patient's tissue through these holes. This has a considerable advantage in holding the device in position. Such a hole can also be used in the electrically insulating enclosure to pass a high-voltage electrical conductor into the device, while ensuring its insulation. This allows, for example, the creation of a galvanically isolated current sensor. Such a hole can also be used to pass chemical or biological substances through the electronic device, for example, to perform in vivo or in vitro biomedical diagnostics.

A hole is made without introducing any electrical creepage path between the inside and the outside of the case at the level of this hole. To do this, we ensure continuity of material or a weld without discontinuity of material. We can also carry out a bonding with chemical adhesion without creepage path. The electrical creepage path can be characterized by the possibility for an ionic (charged) substance to follow the line under the action of a continuous electric field. Avoiding any electrical creepage path amounts to ensuring electrical insulation even in the presence of pollutants and/or solvents.

According to the invention, said at least one printed circuit comprises at least two substantially identical self-inductive coils buried in said at least one printed circuit. They can also be buried respectively in two rigid printed circuits, connected to each other by flexible PCBs as described above. The interest of these two substantially identical self-inductive coils is understood in the production of certain energy transfer systems or magnetic sensors. In combination with the presence of a hole from one side to the other, which can pass through at least one of the two self-inductive coils, it is possible for example to produce a biomedical diagnostic system with the Néel Effect® as described for example in US-20180188206-A1 or US- 20240036125-A1.

By "substantially identical" we mean a difference in inductance between these at least two self-inductive coils of less than 5%, 2% or even 1%. Electrical current measurements, particularly differential measurements, can be made by passing the object to be measured through the hole or by placing it near one of the two coils. In this way, an alternating or transient component of an electrical current can be measured using conventional Rogowski-type technology (air transformer). However, it is also possible to measure the direct current (DC) component of said electrical current.

According to the invention, said at least one printed circuit comprises a superparamagnetic composite material; the superparamagnetic composite material being completely buried in said at least one printed circuit. This type of material is particularly useful for producing DC magnetic field sensors or DC electric current sensors, according to the technology called Néel Effect® and described in US-20180080961-A1 or US-20200011900-A1. The invention makes it possible to produce this type of sensor with great advantages in terms of compactness and high reliability.

According to the invention, at least one of the electronic components is a planar self-inductive coil completely buried in the printed circuit and produced by an arrangement of the tracks of the printed circuit. The advantage of producing planar self-inductive coils in PCB is well known to those skilled in the art: this allows for excellent reproducibility and repeatability as well as extreme compactness. Such advantages are particularly useful for controlling, for example, resonance frequencies specific to multiple applications when the self-inductive coil is coupled with a resonance capacitor, or for producing a pair of substantially identical self-inductive coils.

According to the invention, said at least one printed circuit can itself be made of a material identical to the material of the electrically insulating housing. Initially, it is considered to reuse conventional PCB technologies (for example in epoxy matrix) and to add encapsulation in an epoxy housing. But the present invention aims to use the best possible material to perform all the functions and this advantage can be achieved by preferentially using a PEK housing as described below. The insulating part of the printed circuit can then be made entirely or partly of PEK, which in fact makes it possible to have an electronic device in which the printed circuit and the electrically insulating housing are one. The solution according to the invention makes it possible to make any purely mechanical implantable device "intelligent" since it is now possible to integrate remote communication means and radiofrequency power supply means. Any implantable device is, for example, a knee, femur, vertebrae or any other type of prosthesis. There is no electrical contact between the buried electronics and the external environment of the housing. This solution also makes it possible to make a purely mechanical structure (for example, an airplane wing or a car bumper) "intelligent" by integrating remotely powered sensors and electronics directly into said structure.

According to an advantageous characteristic of the invention, the polymer material may consist in whole or in part of a polymer from the family of polyetherketones (PEK), polyaryletherketones (PAEK) or polyetheretherketones (PEEK).

The use of a PEK polymer allows for all functions such as electrical insulation, mechanical retention and absorption of mechanical actions, sealing, shaping with or without holes and biocompatibility. A PEK polymer also has a proven level of reliability superior to other solutions in terms of high melting temperature, thermoplastic behavior, ductility, hardness, elasticity over a certain deformation range, etc. In particular, PEK allows for a minimum material thickness, which improves the level of integration, without degrading the other characteristics necessary for insulation. The polymer can be a polyetherketone, a polyaryletherketone (PAEK) or a polyetheretherketone (PEEK).

According to the state of the art, for a given and repeatable geometry and design, the characteristic time constant of the probability of a defect appearing ("time to failure" in English), follows the Arrhenius law. This empirical law contains parameters (proportional factor or exponential factor of an activation energy) which depend on the design choices. The speed of appearance of defects varies exponentially with the temperature. Thus, it is possible during a qualification step to accelerate the aging process by increasing the temperature. We then understand the double interest of using high-temperature materials such as PEK polymers. They both improve reliability because they are less subject to aging effects and allow accelerated aging tests to be carried out during design development and qualification if the design is repeatable.

With a polymer flange of the sealed feedthrough as described above, it is thus possible to assemble the flange of each of the sealed feedthroughs on the electrically insulating housing, for example by laser welding, eliminating any electrical creepage path. For this, one can either use polymer materials capable of absorbing the laser energy (naturally or through the addition of specific fillers), or use a combination of two substantially identical polymer materials, only one of which is capable of absorbing the laser energy, as described below. The flange of the sealed feedthrough can then be welded to the electrically insulating housing either by clustering (simultaneous heating of the two parts in a given volume), or by transparency (heating on a surface, at the interface between the two parts).

With an electrically insulating protective topcoat made of polymer as described above, it is also possible to ensure a perfect connection between the flexible printed circuit and the electrically insulating housing, for example by laser welding between the electrically insulating protective topcoat and the insulating housing. It is understood that it is then possible to use such a flexible printed circuit as a sealed feedthrough. Again, the process can be based either on the clustering technique or on the transparency welding technique depending on the mechanical configuration of the device.

With an electrically insulating polymer sheath as described above, it is possible to ensure a perfect connection between the electrically insulating protective sheath and the electrically insulating housing or the flange of a sealed feedthrough, for example by laser welding. Again, the process can be based either on the cluster technique or on the transparency welding technique depending on the mechanical configuration of the device.

With an insulator of at least part of the polymer printed circuit as described above, the printed circuit itself is able to produce the electrically insulating housing made of polymer material. This technology is ultra-compact since there is only one single object, PCB and housing. The layer The finishing of such a case can be carried out by laser welding of polymer sheets from the polyetherketone (PEK) family, a polyaryletherketone (PAEK) or a polyetheretherketone (PEEK), using the so-called clustering technique.

The assemblies described above can be combined in a single device and made sequentially, for example starting with the rigid printed circuit, then the flexible one, then the sealed feedthrough, then the electrically insulating housing, then the cable sheath. This provides an extremely versatile technology capable of producing very diverse forms of electronic devices with high long-term reliability.

According to the invention, the electrically insulating housing made of polymer material may comprise at least one part made of epoxy resin. Such a material has the advantage of being simple to implement. The resin can be used either to bond two parts of the electrically insulating housing made of polymer material, or to coat an electrically conductive element in order to constitute an electrochemical barrier. In this case, it is preferable not to place electrically conductive elements on the same surface, for example a PCB, which would generate electrical leakage lines. This solution has the advantage of its simplicity of implementation but is not the best because epoxy is a thermoset polymer material which is not capable of absorbing mechanical actions in the very long term.

According to the invention, the polymer material may comprise silicone or ultra-high-molecular-weight polyethylene (UHMWPE). The latter has a lower melting temperature than PEK (<136°C) and may be lower than the maximum temperature acceptable for embedded electronics. Note that, on the other hand, UHMWPE is less reliable than PEK over the very long term.

According to the invention, the electrically insulating housing may comprise at least two distinct parts whose polymer materials are of substantially the same chemical composition but one of which is charged with a substance enabling it to have a laser energy absorption rate of at least 10 times greater than the other, or even 100 times greater than the other, or even 1000 times greater than the other part. By "substantially the same composition" we can mean here the same chemical composition, except that a charge is added to one of the two parts.

The mass loading rate of the absorbent substance may be less than or equal to 1%, or even less than 0.1%, or even less than 100 ppm.

This charge rate of the material must be lower than the rate beyond which there is electrical percolation, because the material would then become electrically resistant, or even electrically conductive and no longer electrically insulating. The plastic mechanical properties would also be altered.

A polymer material from the polyetherketone (PEK) family, or more precisely polyaryletherketone (PAEK) with a low carbon content, is intended to:

- the preservation of exceptional chemical, mechanical and thermal properties,

- the conservation of “insulating” type electrical properties, and

- the significant increase in the absorption of an electromagnetic wave in the infrared or near infrared band which facilitates welding operations.

Preferably, the absorbing substance is pure, amorphous carbon, in the form known as "carbon black." Colored pigments may also be used, as is known to those skilled in the art. However, carbon black allows the absorption rate of a laser to be increased with a minimal mass loading rate, thereby reducing the exceptional intrinsic performance of PEK.

The electrically insulating polymer housing can be made by overmolding. Indeed, in order to ensure the material continuity of the electrically insulating polymer housing necessary for the absence of electrical creepage, it is possible to proceed by overmolding, taking care not to exceed the maximum temperature that the buried electronics can withstand, of the order of 175°C for a few minutes. The electrically insulating polymer housing can also be made by 3D printing. But preferably, the electrically insulating housing is made by welding several assemblies, for example two parts or two half-shells. Each of the parts can be made without discontinuity of material by injection under pressure using molds or by compression at low temperature. One of the two parts can be transparent to the laser, i.e. it does not absorb the energy of a laser beam. This is for example the case of a polymer from the family of polyetherketones (PEK), polyaryletherketones (PAEK) or polyetheretherketones (PEEK) called "natural", for wavelengths of the order of lpm and in any case less than 2pm. Thus, the laser beam can pass through this part of the housing without heating it. Obviously, preferably the other part of the housing is able to absorb the power of the laser beam. This is the case, for example, of a polymer from the family of polyetherketones (PEK), polyaryletherketones (PAEK) or polyetheretherketones (PEEK) called "charged", for wavelengths of the order of lpm. Thus, it is possible to achieve a perfect laser weld at the interface between the two parts, one called "natural" and the other called "charged".

The considerable interest of this technique is to allow laser welding in inaccessible places, for example at the interface between the two superimposed parts at the edge of the device for a sealed crossing, or at the edge of a hole inside the case.

The other laser welding technique involves using two substantially identical and absorbent parts and heating them simultaneously in their volume under the action of a laser. This technique, called clustering, allows for excellent welding in the volume but close to the external surface of the assembled parts.

Preferably, in all cases, the lower part will therefore be the loaded part and it will be possible to preferentially design the flanges of the sealed polymer crossing, and/or the electrically insulating protective finishing layer and/or the insulating sheath of the multi-strand conductor in loaded polymer with a view to assembling them by laser welding.

Preferably, the insulating housing can be made by simultaneous injection or compression of the two materials, one "natural" transparent to the laser and the other "charged", absorbing to the laser in order to constitute localized welding zones with one of the two techniques. For example, it may be interesting to place a transparent zone outside a sealed crossing flange, or either flexible PCB protection, or a cable protection sheath (themselves being absorbent).

Generally, all or part of the polymer material elements are assembled by laser welding.

For example, the device may be biocompatible for application as an active implantable medical device. This means that, for example, an electrically insulating housing made of polymer material and the electrically conductive elements of any sealed feedthroughs are biocompatible.

An application of this device is thus provided for transcutaneous energy transfer, the active implantable medical device being capable of capturing electromagnetic energy supplied by an extracorporeal source without any percutaneous connection.

An application of the device according to the invention is also provided for contactless measurement of a mass of superparamagnetic material in the context of rapid in vivo or in vitro biomedical diagnosis.

An application of the device according to the invention is also provided for measuring a DC magnetic field or DC electric current, in which a contactless measurement of at least the static component of a magnetic field is carried out.

Other advantages and characteristics of the invention will appear on examining the detailed description of a non-limiting embodiment, and the appended drawings, in which:

[Fig. 1] Figure 1 is a schematic sectional view of an electronic device comprising electronic components and electrically conductive elements completely buried in a printed circuit and an electrically insulating housing composed of two assembled parts, one natural which is transparent to the laser and the other charged which absorbs the energy of the laser according to the invention, [Fig. 2] Figure 2 is a schematic perspective view of electrical creepage lines and clearance lines on a typical printed circuit board,

[Fig. 3] Figure 3 is a schematic sectional view illustrating an electrically conductive element and a sealed feedthrough both partially buried in the printed circuit according to the invention, the insulating flange of the sealed feedthrough being welded from the outside onto the electrically insulating housing without electrical leakage lines,

[Fig. 4] Figure 4 is a schematic sectional view of a Flex PCB used as a sealed feedthrough according to the invention, and

[Fig. 5] Figure 5 is a schematic sectional view of a device provided with holes according to the invention.

The embodiments which will be described below are in no way limiting; it will be possible in particular to implement variants of the invention comprising only a selection of characteristics described below isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection comprises at least one preferably functional characteristic without structural details, or with only a part of the structural details if this part only is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

In particular, all the variants and embodiments described are intended to be combined with each other in all combinations where there is no technical obstacle to this.

In the figures, elements common to several figures retain the same reference.

Although the invention is not limited thereto, we will now describe an electronic device equipped with a casing based on insulating material from the polyetherketone (PEK) family or more precisely polyaryletherketones (PAEK).

In Figure 1, the electronic device 1 according to the invention can be seen overall. The printed circuit 2 is not only a substrate on which electronic components are installed, but a volume material in which electronic components 3 and electrically conductive elements 4 are buried.

Printed circuit board 2 is for example based on FR4 type glass fiber reinforced epoxy, but it could be made of PAEK. This same material is used both as a mechanical support for the printed circuit board and also as an insulation layer for the surface of the printed circuit board, leaving the electronic components and conductive elements inside and in direct contact between the support and the insulation layer. Using the same material for the insulation and the support ensures during the lamination operation a bond between the layers free of surface defects, and therefore free of electrical leakage lines. Lamination is used for assembly in the volume. It can be completed on the surface by a laser welding clustering technique.

In the example of Figure 1, all the electronic components and all the conductive elements are buried in the volume of the printed circuit 2. But we can consider burying only part of these conductive elements.

The technology for burying elements in a printed circuit board is known to those skilled in the art and was initially developed to increase the degree of integration of electronics, but its function has been diverted here since it makes it possible to eliminate any electrical creepage and any clearance lines as defined in Figure 2. The absence of electrical creepage lines is obtained when there is continuity of material all around an electrical conductor. When there is an interface between two different materials, chemical adhesion must be ensured to avoid this electrical creepage line, including after absorption of a solvent. This adhesion is all the better when the two materials are of substantially identical chemical natures. The mechanical behavior of the material must also be taken into account to avoid delamination phenomena when the electronic device is subjected to mechanical stresses, in particular bending. There are then two complementary solutions, one which consists of mechanically reinforcing the substrate and the other which consists of making the substrate flexible. The first is used in rigid PCBs with a thermoset substrate, the second in flexible PCBs with a thermoplastic substrate, and both in rigid-flexible printed circuits or flex-rigid PCBs. A minimum of mechanical rigidity can be maintained at the level of the electrical components to avoid breaking the electrical welds of components on electrically conductive elements.

In Figure 1, there is also a housing 5 which completely encloses, without discontinuity of material, the printed circuit 2. A space 52, for example with air, may exist between the housing 5 and the printed circuit 2, in particular when the printed circuit is held by pads. This space may not exist totally or partially when the housing is for example obtained by overmolding. The housing 5 is made of a biocompatible insulating material such as polyetherketone (PEK) or more precisely a polyaryletherketone (PAEK) which is a thermoplastic polymer that a person skilled in the art knows how to machine, extrude or inject. The assembly comprising the printed circuit, the electronic components and the electrically conductive elements can be covered by overmolding with PEK at a temperature above the glass transition temperature and for a duration allowing the integrity of the electronics of the printed circuit to be preserved.

The function of the housing 5 is to provide a second insulation and/or a biocompatible or chemically resistant character that the printed circuit 2 does not necessarily possess, to serve as a barrier against any pollutant, to guarantee electrical insulation between the printed circuit and a user or equipment, and to allow any transmission of electromagnetic energy (radiofrequency communication and/or energy transfer) between the inside and the outside of the housing.

According to the invention, the electrically insulating housing comprises at least two distinct parts 5A and 5B, the polymer materials of which are of substantially the same chemical composition, but one of which is charged with a substance enabling it to have a laser energy absorption rate at least 10 times greater than the other, or even 100 times greater than the other, or even 1000 times greater than the other part.

According to the invention, this result can be achieved without modifying the other intrinsic properties of the polymer material when the mass loading rate of the absorbent substance is less than or equal to 1%, or even less than 0.1%, or even less than 100 ppm.

According to the invention, the absorbent substance is carbon black which has a very high absorption power. It also has the advantage of being the simplest absorbent element already present in the composition of most polymers, particularly PAEK. Carbon-filled PAEKs are renowned for their biocompatibility. However, care must be taken not to overfill the composite at the risk of degrading these electrical, mechanical, or chemical properties. Carbon black allows this objective to be achieved with a minimal loading rate.

The design of an electrically insulating housing from two parts 5A and 5B, for example a white one (called natural and transparent to the laser) and a black one (charged, absorbing the laser), whose chemical, electrical and mechanical properties are substantially identical but whose rate of absorption of the energy of a laser is substantially different, advantageously makes it possible to produce a robust housing free from electrical creepage lines. This technique is known to those skilled in the art, it consists of plating the absorbing part 5B inside the transparent part 5A, then illuminating the interface using a laser beam. The laser beam passes through the transparent part without heating and is absorbed at the interface 5C between the two parts 5A and 5B. The beam is generally of low power (<lkW) and continuous so that the energy diffuses sufficiently at the interface, thus producing a weld bead perfectly free from electrical creepage lines.

In Figure 2 is illustrated a conventional printed circuit which is a flat insulating substrate 6 on which electrically conductive elements 7 are mounted. Pollutants and/or condensed water vapor can settle on the surface of the flat insulating substrate 6 and create by their presence unwanted conduction lines between electrically conductive elements 7, called electrical creepage lines. To reduce this phenomenon, barriers 8 and spacings 9 can be made on a substrate to extend the length of the electrical creepage lines 10 and clearance lines 11. A clearance line represents the shortest distance path in the air between two conductors. An electrical creepage line represents the shortest distance path along a surface between two conductors.

Barriers 8 and spacings 9 are not sufficient to prevent the long-term occurrence of defects in the presence of pollutants and/or solvents such as water and a polarization voltage. The solution of the present The invention is to bury all the components, active and passive, and electrically conductive elements inside the printed circuit. The same material is used all around the components and electrically conductive elements. Thus, electrical creepage lines and clearance lines are eliminated. For each pair of conductors in an electrical circuit, there is neither clearance line nor electrical creepage line. The addition of a simple conformal coating on the surface makes it possible to eliminate clearance lines but not electrical creepage lines due to poor long-term adhesion phenomena at the interface with the insulating flat substrate 6. Using the same material as the insulating flat substrate 6 to act as a coating makes it possible to eliminate both clearance lines and electrical creepage lines. It is in this sense that we speak of continuity of material, for example FR4, at the level of the printed circuit 2 as illustrated in Figure 1. In this case, the continuity of material of the printed circuit 2 protects the electrically conductive elements 4 and the buried electronic components 3 from all electrochemical phenomena. But since this material of the printed circuit 2 is generally not biocompatible, and/or since double electrical insulation must be ensured, the continuity of material of the printed circuit 2 alone is not sufficient to guarantee long-term reliability. Continuity of material is also required at the level of the housing 5 of Figure 1, but with a different material, for example PAEK, an electrical insulator, not very sensitive to chemical attacks and biocompatible. Then, the continuity of material of the housing 5 protects users from all electrical risks and/or particulate releases. It should be noted that when PEK material is immersed in a solvent, for example water, for a very long time, it will become charged with water molecules in gaseous form by a process called Fick diffusion. The material is waterproof but not airtight. However, the absence of electrical leakage lines ensures that the insulation performance of water-charged PEK is maintained and thus the absence of electrochemical phenomena.

When you want to access an electrical potential located inside the PCB, for example at the level of an electronic component, you must be able to remove an electrically conductive element without introducing an electrical creepage line. For this, you can use a sealed feedthrough. The sealed feedthrough 12 of Figure 3 is made during the manufacture of the printed circuit 2 (it could also be assembled a posteriori on a flexible part of the printed circuit). In this process, the sealed feedthrough becomes a component that is partially buried in the printed circuit 2 since its electrically conductive element remains accessible to the outside. In this case, the sealed feedthrough 12 generally has a shape allowing it to be soldered at the electrical potential to which access is desired, for example by the CMS (surface mounted component) soldering process. The electrically conductive connection 13 extends from the track 4 to one end outside the housing 51 via the printed circuit 2 and the flange 14. All the electrically conductive elements remain completely inside, encapsulated in, the housing. Only the electrically conductive connection passes through the housing.

The flange 14 is partially contained in the printed circuit 2 and does not need to contain both an insulating area and a fixing area since the PEK polymer material is used for both purposes. For example, through laser welding between the insulating flange and the sealed housing. The flange then becomes part of the insulating housing. It is understood that the choice of materials and manufacturing processes is one of the keys to the success of the operation in order to guarantee the elimination of electrical creepage lines. This is why the choice of material 14 among PEK and more particularly PAEK is important and forms part of the invention.

In Figure 3, the housing 51 is made of two substantially identical materials but one (51B) being charged to absorb the laser energy and the other (51A) being transparent as in Figure 1. It can be assembled by laser welding by transparency by applying a laser beam from the outside to the inside, from right to left in Figure 3.

In order to now guarantee the continuity of material at the housing 51, the electrically conductive connection 13 is surrounded by the flange 14 whose material is identical to that of the housing 51B (charged). For example a PEK and more precisely a PAEK. The biocompatible sealed feedthrough 12 can be assembled to the housing 51A according to a method known to those skilled in the art so that the latter has continuity of material. The assembly is preferably carried out by laser welding between the flange 14 and the housing 51A using the transparency welding technique. Advantageously, it is possible to provide for loading the material of the flange 14 with carbon black as described previously, taking care to use for the material of the housing 51A a PEK and more precisely a natural PAEK (unfilled). Thus the welding would be carried out by the technique of laser welding by transparency on the entire periphery of the flange of shape for example circular and at the interface with the housing 51A so that there cannot be an electrical creepage line. In Figure 3, the laser can be applied from the right (outside) to the left (towards the inside of the housing) by targeting a lateral flank 14A of the flange 14, this flank being obtained by making a step of the flange in the thickness of the side wall of the housing. A part of the flange extends at least to the external end of the housing. We are thus able, using the same welding technique, to assemble without electrical creepage both the two parts of the insulating housing 51A and 51B and the sealed feedthrough 12. In practice, we start by welding the sealed feedthrough then the housing.

When at least one second conductor is required, for example to connect the electronic device to a bipolar cable, then either this second conductor is placed in the same flange 14 as the first conductor 13, or a second sealed feedthrough is preferably placed near the sealed feedthrough 12 in order to facilitate assembly of the cable.

It may be necessary to extract a conductive element from the PCB without necessarily removing it from the waterproof enclosure. For example, to connect two PCBs together. Preferably, a metallized via is used to bring out the potential on at least one of the two sides of the PCB. It is then interesting to be able to both "close" the metallized hole which risks being subject to electrochemical phenomena and to deport the electrically conductive element without introducing creepage lines. For this, a flexible PCB is preferably used which is placed on at least one of the two sides of the PCB. The via located on the other side of the PCB will then be made blind thanks to the addition of a protective finishing layer over its entire surface. This layer can be assembled by conventional lamination or by laser clustering. A flexible PCB is generally covered with an electrically insulating protective finishing layer. This Flexible PCB can then be used to interconnect another PCB which is also inside the enclosure. We will then preferentially use another interface PCB allowing the two flexible PCBs to be soldered together. At the location of the solder, there is then an electrical creepage line. For example, this solder can be overmolded with an insulator, for example a heat-cured epoxy resin. The solder can preferably be encapsulated inside a small PEK box which is welded onto the flexible PCB by laser clustering, for example. We then have a flexible-rigid PCB composed of several flexible parts and several rigid parts, but completely free of electrical creepage line.

The sealed via can be buried in a flexible PCB and then the assembly can be carried out in the same way as described above. This technique makes the buried PCB easier to produce because the introduction of a clearance area for the sealed via requires additional operations during PCB manufacturing. Whereas adding a sealed via to the flexible part of a rigid-flex PCB can be done retrospectively.

Figure 4 shows an exemplary embodiment in which the printed circuit or PCB is a rigid-flexible printed circuit. It consists of a rigid printed circuit 2A associated with a flexible printed circuit 2B. The electronic components and the electrically conductive elements can be arranged in the rigid printed circuit, in the flexible printed circuit or between the two.

The flexible printed circuit 2B is covered on each side with an electrically insulating protective finishing layer 15. Preferably, this is made of PEK or PAEK loaded to be able to absorb the energy of a laser.

In Figure 4, the sealed feedthrough is constituted by an electrically conductive connection 16 and an extension of the flexible printed circuit 2B, this extension being the part of the flexible printed circuit 2B (and its finishing layer) not directly attached to the rigid printed circuit 2A and passing through the housing 51. The housing 51 also comprises an extension 51C towards the outside which frames the extension of the flexible printed circuit 2B.

The electrically insulating protective finishing layer 15 is made of the same material as the extension 51C placed on either side, for example a loaded PAEK, in order to be able to weld it onto the housing using the laser clustering technique. For this purpose, provision is made to load the areas 17 and 18 of the extension 51C which are directly in contact with the protective finishing layer 15 of the flexible printed circuit 2B with carbon black. In Figure 5, a device according to the invention is provided containing holes in the housing. The housing is of the same nature as the housing 5, in two materials 22B, 22A, charged and uncharged, but with holes 19 and 20. These holes can allow fixing or the passage of an external element, of an electrical, mechanical, chemical or biological nature.

At least two substantially identical self-inductive coils (not shown) are embedded in the printed circuit 23, which may be a rigid printed circuit or a rigid-flexible printed circuit. The coils are used as magnetic sensors. They can then be used to measure an amount of superparamagnetic material for a biomedical diagnostic application by passing a sample whose amount of magnetic material is representative of the amount of an analyte to be measured through a hole. Advantageously, a hole passes through at least one of the two coils to place the sample therein. The differential measurement relies on the fact that the other coil does not contain superparamagnetic material, which improves the signal-to-noise ratio of the measurement.

The device of Figure 5 may include all the features as described in the other figures. A hole is for example 1 mm in diameter and passes through the entire height of the housing. The holes 19 and 20 pass through the housing 22A, 22B and the printed circuit 23 (of the same nature as the printed circuit 2, or 2A-2B, but with through holes) without damaging the electronic components 24.

Studs 25, 26 are part of the housing and are made inside the housing, between two facing walls. These studs are drilled in the middle so that a hole exists through the entire housing. The housing is then made by assembling two PAEK half-shells 22A, 22B. In order to ensure the absence of a creepage line, continuity of material is guaranteed by welding the two PAEK half-shells, for example with a laser using the transparency welding technique applied from the outside to the inside (on the top in the case of this figure 5). It is then preferable for the lower part of the housing to be made of loaded PAEK while the upper part is natural (unloaded). Thus the welding is carried out at the interface between the two parts of the housing. Note that it is not possible to achieve such a waterproof geometry with a titanium case, since transparent welding is impossible, which explains why current titanium cases do not have a fixing system or hole for all other applications. The present invention aims to eliminate this problem and thus develop electronic devices with high long-term reliability requiring the use of a through hole.

Other applications that may benefit from the present invention include the ability to change the nature of a medical device casing to enable it to transmit energy and/or information (implantable pacemakers and defibrillators, mechanical cardiac assistance devices such as LVAD (Left Ventricle Assist Devices), total heart, implantable cardiac monitor (Implantable Loop Recorder), intramedullary limb lengthening system, implantable pumps, artificial kidney, cochlear implant, neurostimulator, implantable human-machine interface, etc.) but also the ability to make a purely mechanical prosthesis intelligent by adding medical device functionalities to it.

Of course, the invention is not limited to the examples just described. Numerous modifications can be made to these examples without departing from the scope of the present invention as described.

Claims

1. Electronic device comprising at least one printed circuit, electronic components, electrically conductive elements and an electrically insulating housing made of polymer material, characterized in that: - all the electronic components and at least some of the electrically conductive elements are partially or totally buried in said at least one printed circuit, and - the electrically insulating housing made of polymer material completely encapsulates and without electrical creepage lines said at least one printed circuit and all the electrically conductive elements which are not already partially or totally buried in said at least one printed circuit; said polymer material being made in whole or in part of a polymer from the family of polyetherketones (PEK), polyaryletherketones (PAEK) or polyetheretherketones (PEEK). 2. Device according to claim 1, characterized in that the printed circuit is a rigid-flexible printed circuit comprising a rigid part and a flexible part. 3. Device according to claim 2, characterized in that it comprises at least one sealed crossing through a wall of the electrically insulating housing, this sealed crossing comprising: - at least one electrically conductive connection having at least one part buried in the flexible part of the rigid-flexible printed circuit, this flexible part being covered with at least one electrically insulating protective finishing layer made of polymer material, - an extension of the flexible part which surrounds the electrically conductive connection at least through the wall of the electrically insulating housing, this extension serving as an electrically insulating flange and without electrical creepage line at the interface between this flange and the electrically conductive connection. 4. Device according to claim 2 or 3, characterized in that it comprises at least one other printed circuit, the two printed circuits being electrically connected by means of an electrically conductive element buried inside a part of the flexible part. 5. Device according to claim 1 or 2, characterized in that it comprises at least one sealed passage through a wall of the electrically insulating housing, this sealed passage comprising: - at least one electrically conductive connection having at least one part buried in said at least one printed circuit, - an electrically insulating flange made of polymer material made around the electrically conductive connection and without electrical creepage at the interface between this flange and the electrically conductive connection; the electrically insulating flange made of polymer material being a part of the electrically insulating housing made of polymer material. 6. Device according to any one of the preceding claims, characterized in that at least one of the electrically conductive elements is contained in a multi-strand conductor covered with at least one electrically insulating protective sheath made of polymer material. 7. Device according to any one of the preceding claims, characterized in that at least one of the electronic components is a self-inductive coil intended to receive or emit information and/or energy by magnetic coupling with a device located outside the electrically insulating housing made of polymer material; the self-inductive coil being buried in said at least one printed circuit. 8. Device according to any one of the preceding claims, characterized in that the electrically insulating housing made of polymer material contains at least one hole passing through the electrically insulating housing made of polymer material from one side to the other; the hole being made in such a way that it does not introduce any electrical leakage line. 9. Device according to any one of the preceding claims, characterized in that said at least one printed circuit comprises at least two substantially identical self-inductive coils buried in said at least one printed circuit. 10. Device according to any one of the preceding claims, characterized in that said at least one printed circuit comprises a superparamagnetic composite material; the superparamagnetic composite material being completely buried in said at least one printed circuit. 11. Device according to any one of the preceding claims, characterized in that at least one of the electronic components is a planar self-inductive coil completely buried in the printed circuit and produced by an arrangement of the tracks of the printed circuit. 12. Device according to any one of the preceding claims, characterized in that said at least one printed circuit is made of a material identical to the material of the electrically insulating housing. 13. Device according to any one of the preceding claims, characterized in that the electrically insulating housing made of polymer material comprises at least one part made of epoxy resin. 14. Device according to any one of the preceding claims, characterized in that the electrically insulating housing comprises at least two separate parts whose polymer materials are of substantially the same chemical composition but one of which is charged with a substance enabling it to have a laser energy absorption rate at least 10 times greater than the other, or even 100 times greater than the other, or even 1000 times greater than the other part. 15. Device according to claim 14, characterized in that the mass loading rate of the absorbent substance is less than or equal to 1%, or even less than 0.1%, or even less than 100 ppm. 16. Device according to claim 14 or 15, characterized in that the absorbent substance is carbon black. 17. Device according to any one of the preceding claims, characterized in that all or part of the elements made of polymer material are assembled by laser welding. 18. Device according to any one of the preceding claims, characterized in that it is biocompatible for application as an active implantable medical device. 19. Application of the device of claim 18 for transcutaneous energy transfer, the active implantable medical device being capable of capturing electromagnetic energy supplied by an extracorporeal source without any percutaneous connection. 20. Application of the device of any one of claims 1 to 18 for contactless measurement of a mass of superparamagnetic material in the context of rapid biomedical diagnosis in vivo or in vitro. 21. Industrial or medical application of the device of any one of claims 1 to 18 for a measurement of magnetic field or electric current, in which a contactless measurement of at least the static component of a magnetic field is carried out.