WO2008142206A1

WO2008142206A1 - Method for producing circuit boards comprising electronic, optical and functional features

Info

Publication number: WO2008142206A1
Application number: PCT/FI2008/050287
Authority: WO
Inventors: Tommi Stenroos; Torolf Pelin; Tomi Dahlberg
Original assignee: PINTAVISION Oy
Current assignee: PINTAVISION Oy
Priority date: 2007-05-24
Filing date: 2008-05-20
Publication date: 2008-11-27
Anticipated expiration: 2009-11-24
Also published as: FI20070409A0; FI20070409A7

Abstract

An object of this invention is a method for producing circuit boards having electronic, optical and functional features, wherein the surface of the base plate (1) of the circuit board is provided with metallization (7, 8), an insulating protective layer upon the metallization, the next conductive layer (9, 10) upon the protective layer, etc., until the needed number of layers has been deposited one upon the other. The base plate (1) is produced of a plate preform, the handling of which in the production of a circuit board is performed from the processing location in the middle of the plate preform, such as a hole (2).

Description

Method for producing circuit boards comprising electronic, optical and functional features

An object of this invention is a method for producing circuit boards, wherein the surface of the base plate of the circuit board is provided with a conductivity layer (metallization), an (electrically) insulating protective layer upon the metallization, the next metallization layer upon the protective layer, etc., until the needed number of metallization and insulation layers has been deposited one upon the other. Conductivity layers can be made by gas phase-coating or by printing technique processes. Typically, by means of the method according the invention light carrying/translucent layers made of optical polymer or polymer coating and light channels created by superimposed layers can be placed onto the circuit board so that the refractive index of material used in every layer or light channel is constant and thus known such as the other optical features of materials. Due to the refractive index, known as constant, and the other optical features light transmission, reflectivity, conductivity and orientation of these layers or light channels are also known and constant. The protective layer placed onto the electronic metallization layer may have, besides insulating and optical function, also one or many other functional features, such as the hardness of a surface, the anti-contamination of a surface, the self-purification of a surface, the antistaticity of a surface, the antiphobicity of a surface, the hydrophobicity of a surface or the other useful feature for a circuit board. The optical or functional features may be the features of the insulating layer or be formed of separate layer. In addition, by the described method passive and/or active components of optics, opto-electronics and electronics can be produced.

One of the most common production method for circuit boards is that a thin metal layer, such as a copper layer, is provided onto the non-conducting base plate by metallizing, upon which is printed a protective lacquer shaped of a desired metal pattern, which protects this conducting metal pattern for the next handling phase.

After this the base plate with its circuit boards are submersed in an etching basin, wherein the uncovered metal areas are etched away. If several circuit board layers are preferably produced onto the base plate one upon the other, a new nonconducting (protective) layer is produced onto the completed first circuit board layer, upon which the next metal layer is provided, onto which is printed the protective lacquer layer shaped like the desired metal pattern of the next circuit board layer and the etching is performed to remove metal from this circuit board layer. The result of these phases is the second metallic circuit board layer. If further circuit board layers are desired onto the same base plate, the aforementioned procedures will be repeated so many times that the desired number of the circuit board layers is produced onto the same base plate. The known production method with various variations as described takes a lot of time and is expensive. It is also known in the art that the conductive metal conductors can be deposited onto the non-conductive base plate. Metal is deposited by various known method, such as by various vacuum vaporization methods by covering with so-called masks the areas that are preferably not to be deposited with metal. Otherwise, the production of circuit boards with several layers is performed in the same way as with the etching method by alternating conductive layers and insulating layers. Also the method based on the vacuum vaporization and the etching is expensive and slow as implemented separately.

One may also desire to produce light carrying/translucent layers and light channels to the multilayer circuit boards in particular. Light channels are produced by embedding glass into the circuit board. The use of glass in producing light layers and light channels is considered laborious and problematic due to the difficult process. In the light layers (surface structures, such as lenses, prisms or diffractive structure, are needed to control the progress of light in the light layers) and, channels are important to know the light transmission, reflectivity and orientation in the material. This is best achieved, if the refractive index of used materials and the other features are well known constants. Alternatively, circuit boards can be produced by the other known techniques, such as MID technique (moulded inconnected devices) and the exposure technique.

This invention describes a new type of production method of circuit boards, where, as basis, a known patent FI-117621 and the production of multilayer pieces by means of a multi-phase process enabled by the patent, are exploited. The production method according to the invention is more affordable than the above described methods, because it is characterized in that the base plate is produced of a standard- size plate preform, the handling of which in the production of a circuit board is performed from the processing location in the middle of the plate preform, such as a hole, and from the alignment points on the outer edge of the plate preform. The alignment points on the outer edge may also be located in an auxiliary worktop as described in the patent FI-117621. Thus the handling of the base plate of the circuit board from a working phase and a work place to another takes place without touching with hands to the base plate, whereupon all conducting, metallization layers and non-conductive coating layers protecting the metallization as well as light carrying layers and light channels will remain clean throughout the whole production and coating process and after that regardless of the number of the process phases. At the same time the method ensures the production of the nearest possible high quality of the end product. In addition, the production and coating process, as a whole, is from the beginning to the end - from the production of the plate preform to the packed circuit board - also faster than the other known production and coating processes for circuit boards, because the phases of the production process for circuit boards are in a chain. While producing optical layers and light channels, the optical polymers and polymer coatings are exploited, for example PMMA, the refractive index and the other optical features of which are constant and thus known. Examples of various embodiments of the invention are described in the dependent claims of the patent claim set.

Next, the invention will be described via examples with reference to the attached drawings in which:

Figure 1 illustrates a base plate of a circuit board in an axonometric view,

Figure 2 illustrates the same base plate of a circuit board as in Fig. 1 with the difference that in Fig. 2 two masks of circuit boards has been placed upon the base plate in order to deposit metal,

Figure 3 illustrates the spreading of the protective coating by the "spin-coating" method,

Figure 4 illustrates the cutting of the circuit boards out of the base plate by laser cutting,

Figure 5 illustrates optical data transfer through the circuit board from a microcircuit to another microcircuit,

Figure 6 illustrates an optical surface structure point in the base plate, where the light ray changes its direction 90° and

Figure 7 illustrates a multilayer circuit board, which has both light carrying layers and light carrying channels.

Figure 8 illustrates the production of the conductors by tampo technique. The square base plate illustrated in Fig. 1 is comprised of a non-conductive plastic or fiberglass plate with a handling hole 2a of the plate in the middle and alignment points 2b on the outer edge. The handling of the base plate, i.e. the creation of layers of a circuit board/circuit boards produced onto the base plate is usually taken place with pins that fit to the hole or grippers, a suction system that fits around the hole and/or by means of alignment points 2b on the outer edge of the base plate so that neither to the base plate and to the surfaces of the layers of the primary circuit board/boards are neither touched with hands nor mechanically. Thus the surfaces of a circuit board/circuit boards will remain clean throughout whole processes, since the working phases of the forming of a circuit board/circuit boards are in chain from the processing of raw material to the packing of completed circuit boards. When the whole production process is located to a clean room, also the purity problems caused by environment are minimized. The end products that have as good quality as possible are created due to these features of the processes.

In Fig. 2 the base plate 1 is moved to a vacuum vaporization chamber, where masks 3, 4 are placed upon the upper surface. The masks are so-called negative masks, i.e. the desired conducting pattern for the circuit board is formed to the openings of the masks in the vacuum vaporization chamber. Masks 3, 4 are attached in place with support poles 5 fixed to the masks. When sufficient negative pressure is provided in the vacuum vaporization chamber, the vacuum vaporization is performed with suitable metal/alloy, for example with copper. Evaporated metal/alloy is attached onto the surface of the base plate through the holes in the mask, whereby a conductive pattern in the shape of holes in the mask is created onto the surface of the base plate. Thus the first conductive metal pattern of the circuit layer is immediately completed.

After the metallization the base plate is moved to the "spin-coating" station shown in Fig. 4, where the plate is rotated first slowly and small amount of protective lacquer 6 is concurrently sprayed near to the handling hole 2a. After this the base plate is rotated with a great speed, whereby the protective lacquer is spread uniformly throughout the whole surface of the plate by forming a thin and uniform protective film onto the circuit boards 7, 8 due to the centrifugal force created by the rotating motion. Finally, the protective film is dried, for example by UV drying.

In Fig. 5, after forming the protective layer as referred in Fig. 3, the masking and the vacuum vaporization of the next conductive layer is performed if desired, in which case the next layer's circuit board patterns 9, 10 are obtained upon the protective film formed in Fig. 3. The sufficient number of the masking/conductivity and protective layer work phases are repeated, until the board/boards have a desired number of layers. After this, if necessary, the whole base plate can still be coated with protective lacquer/hard- coating, for example, with so-called "hard-coating" lacquer layer or with another functional coating such as with ceramic layer-producing sol gel or nano-coating. Also this/these layer/layers is/are done by "spin-coating" method when thin, maximally uniform layers are desired.

By using optical, light carrying polymer or polymer coating to form the protective layer/layers, for example PMMA, the refractive index of which is known as constant, e.g. 1.497, and the other features, e.g. 92.0% of light transmission per mm, a light carrying/translucent layer or a light channel will be formed into the circuit board, the optical behavior of which is known when all the refractive indexes of the layer/layers and the other optical features are known. The thickness of the base plate may vary in range of 0.1 - 2.5 mm.

The light channels can be produced by the form in the stamper or alternatively, by engraving with laser. The channels may be filled with polymer having a different refractive index, which may be in solid or in liquid form.

The base plate is moved after production process phases, which have been dealt above, to the drilling station, where the required holes 11 are drilled mechanically or by a laser device. As the final work phase is the cutting of the completed circuit boards out of the base plate and transferring those for packing in the packing machine. The cutting out is performed, for example, by laser cutting device 12 moved above the base plate.

According to the simplified example of the invention, the shape of the base plate is square-like, although its shape may as well be some other polygon shaped or round as well.

Metallization of a circuit board/circuit boards can be performed, if desired, onto the both sides of the base plate either by without turning the base plate (the metallization and the coating from underneath) and/or by turning the base plate during the process (the metallization and the coating of the both sides from above).

The conductivity and/or the metallization handling may also be taken place, besides the vacuum vaporization, by means of laser printing, tampo or silk screen printing, laser ablation, so-called laser based lift method, or transfer film or by the other metallization suitable for the method according to the invention. The "spin-coating" method may refer also to the spreading of the protective lacquer/coating material onto the base plate first by some other spreading method that is described in Fig. 3 so that after the spreading the base plate is rotated according to the method for creating a thin, uniform layer.

Besides the "spin-coating" method, the protective lacquer/coating material may also be spread onto the base plate by tampo, silk color, offset or laser printing technique, vacuum vaporization, laser ablation, the other thin-film technique or by means of transfer film.

The protective layer of the metallization may have, besides the protection of the metallization, one or more functional tasks, such as light guiding of the coating layer, transparency, light directing, preventing the light reflection, light absorption, hardness of a surface, anti-contamination of a surface, the self-purification of a surface, the antistaticity of a surface, the antiphobicity of a surface, the hydrophobicity of a surface, or other useful feature for a circuit board. r The circuit board may have, in addition to the metallization layer/layers and the protective layer/layers of metallization, optical layers and/or functional layers besides that the optical and functional features may be in the protective layer/layers of metallization as shown in Figs. 5-7. Several base plates passed through the production process are also possible to connect to each other e.g. by laminating, as shown in Fig. 7. The connecting may also take place after the completed circuit boards have been cut out of the base plate.

In Fig. 5, a microcircuit 13 is attached onto the upper surface of the circuit board. The microcircuit has also optical activity, i.e. it emits light ray to another microcircuit 14. The microcircuits are in electric contact to the metal conductors 7, 9 in the circuit board as well.

In Fig. 6 there is in the first lower surface of the base plate an optical surface structure point 15, which changes part of light ray 16 90° degrees, in which case this turned ray meets the microcircuit 17 on the upper surface of the circuit board. The optical surface structure point may also be in some other layer of the circuit board and the conversion angle may be some other than 90°. In Fig. 7, the circuit board is formed of two base plates connected to each other, of which have both conductive metallization and light carrying layers 18 and light carrying channels 19. The optical surface structure point may also locate above or below of the microcircuit (light source) in the base plate or the coating. Thus the function of the surface structure is to turn light to so wide angles that it can propagate more efficiently in light channel and/or layer.

In Fig. 8 the conductors are produced by using tampo printing. The desired conductor pattern is etched to a tampo printing plate 8a. Conductive materials, for example electrically conductive polymer or particular materials are used as printed materials. Conductive material is transferred by means of a pillow 8b, 8c onto the surface 8d of the base plate and the desired conductor pattern is completed 8e for the next phase. Alternatively, conductive patterns may be produced of conductive material by means of the other well known printing techniques, e.g. the silk screen printing.

The characteristics of the production process in accordance with the invention described above expand the use possibilities of the method according to the invention in the production of circuit boards and the use possibilities of the circuit boards, because the optical and functional features can be included to the circuits boards so that the production thereof is inexpensive and fast when compared to the other manufacturing methods.

Claims

1. A method for producing circuit boards, wherein the surface of the base plate (1) of the circuit board is provided with a conductivity layer (metallization) (7, 8) of the circuit board, an insulating protective layer upon the metallization, the next metallization layer (9, 10) upon the protective layer, etc., until the required number of layers has been deposited one upon the other, characterized in that the base plate (1) is produced of a plate preform, the handling of which in the production of a circuit board is performed from the processing location in the middle of the plate preform, such as a hole (2a) and/or from alignment points (2b) in the outer edge of the base plate or in an auxiliary worktop attached to the outer edge.

2. A method according to claim 1, characterized in that the masking is performed for the metallization of the circuit board, wherein a negative, shape of the circuit board, mask (3, 4) is utilized, after which the metallization is performed by vacuum vaporization so that the metallization is created at the place of the holes in the mask.

3. A method according to claim 1, characterized in that the conductivity layer of the circuit board is produced by means of the tampo printing (3) or some other known printing technical method.

4. A method according to claim 1, characterized in that the metallization of the circuit board is produced by laser printing, laser ablation, laser based lift method, silk screen printing, by means of a transfer film or by the other metallization method suitable for as a part of the method.

5. A method according to claim 1 or 2, 3 or 4, characterized in that the metallization is protected with lacquer (6), color or another coating, which is provided onto the surface by "spin-coating" method, wherein lacquer, color or coating spreads from the centre point or onto the base plate spread by another means due to the centrifugal force in a direction of the radius outwards onto the whole surface of the base plate.

6. A method according to claim 1 or 2 or 3 or 4, characterized in that the metallization is protected with a protective layer (6), which is obtained by tampo, silk color, offset or laser printing technique, vacuum vaporization, laser ablation, the other thin-film technique or by means of a transfer film or by the other coating method suitable for as a part of the method.

7. A method according to claim 5 or 6, characterized in that the protective layer of the metallization has, besides the protection of the metallization, one or more functional tasks, such as light guiding of the coating layer, transparency, light directing, prevention of the light reflection, light absorption, hardness of a surface, anti-contamination of a surface, self-purification of a surface, antistaticity of a surface, antiphobicity of a surface, hydrophobicity of a surface or other useful feature for the circuit board.

8. A method according to any of preceding claim, characterized in that the topmost protective layer or the protective layers are implemented with a hard "hard- coating" lacquer layer, a liquid functional coating, tampo, silk color, offset or laser printing technique, vacuum vaporization, laser ablation, other thin-film technique, by means of a transfer film or by other coating method suitable as forming a part of the method.

9. A method according to any of preceding claim, characterized in that the needed perforations (11) are performed after metallization and coating of the protective layers by drilling, milling, die-cutting or laser cutting.

10. A method according to any of preceding claim, characterized in that the circuit boards are cut out of the base plate after the perforation by milling, die- cutting or laser cutting (12).

11. A method according to any of preceding claim, characterized in that the optical and functional features are the features of the protective layer of the metallization, the base plate and/or a separate coating layer, that several base plates passed through the production process are connected to each other e.g. by laminating, and that the connecting takes place after the completed circuit boards have been cut out of the base plate.

12. A method according to any of preceding claim, characterized in that the optical light channels are provided into the base plate, with which optical data transfer buses are provided to the circuit board, by means of which data can be transferred between microcircuits and modules.

13. A method according to any of preceding claim, characterized in that the light channels are produced of plastic, such as PMMA, of which refractive index and light transmission capability are constant and known.

14. A method according to any of preceding claim, characterized in that several base plates produced of optical plastic are connected one upon the other, in which case are get both light carrying layers and light carrying channels (Fig. 7).

15. A method according to any of preceding claim, characterized in that the optical surface structure point is provided onto the surface of the base plate, by means of which the light carrying layer changes the angle of the light ray 90^° to the light carrying channel.

16. A method according to any of preceding claim, characterized in that passive and/or active components of optics, opto-electronics and electronics are produced by the described method.

17. A method according to any of preceding claim, characterized in that the thickness of the base plate is produced of 0.1 - 2.5 mm optical plastic.