HK1133989B - Circuit carrier and process for producing thereof - Google Patents

Description

Circuit carrier and method for producing the same

Technical Field

The invention relates to a circuit carrier and a method for producing the same.

Background

Such circuit carriers are preferably used in the field of high-power electronics, in particular in the field of high-temperature applications in the engine compartment of motor vehicles.

The operation of each electrical or electronic circuit is associated with the generation of waste heat, which must be removed as quickly as possible in order to avoid damaging the operation or destroying the circuit. Especially high power electronic devices exhibit a very large amount of waste heat when in operation. Higher ambient temperatures in excess of 100 c (e.g., about 150 c in certain areas of the engine compartment of an automobile) make this difficult in high temperature applications. In order to achieve the fastest possible removal of waste heat, the electrical or electronic circuit is arranged on a circuit carrier, the metallic carrier material of which can act as a heat sink for the circuit.

The dielectric material layer is mostly formed much thinner than the layer formed from the metallic material, and serves to electrically insulate the individual conductor tracks arranged on the dielectric material layer from the metallic carrier material. Furthermore, a dielectric material can be selected which is distinguished by a very low thermal resistance, so that the waste heat of the electrical or electronic components arranged on the dielectric material layer can be dissipated as quickly as possible via the metallic carrier element.

The dielectric layer may have many pores after its fabrication. It may be necessary for different reasons that these pores are sealed with a sealing material. The presence of, for example, pores impairs the electrical insulating properties of the layer of dielectric material, which can be problematic especially in humid working environments. As a result of the moisture penetrating into the pores, an electrical short circuit may occur between the conductor tracks and the metallic carrier material.

The problem of pore formation occurs to a different extent depending on the production method. In particular, methods in which a layer of dielectric material is applied to a metallic support material by thermal spraying are associated with the problem of forming fine pores.

Such processes are described, for example, in GB 990023, GB 1461031 and EP 115412 a 2. Although the thermal spraying method is in itself very well suited for applying dielectric materials to metallic carrier materials, the problem arises that the sprayed dielectric material layer has a large number of pores, which may significantly reduce the electrical insulating ability of the dielectric material layer. The presence of fine pores is particularly problematic in humid environments.

For example, EP 48992 a2 describes a method in which a resin for sealing fine pores is applied to a layer of dielectric material after thermal spraying of the layer of dielectric material. Sealing of the pores by applying an epoxy resin is likewise known from DE 19529627C 1. Sealing of the pores by means of a ceramic glaze which melts in a temperature range between 600 ℃ and 800 ℃ is also described.

The use of resin materials is disadvantageous in that it involves a relatively complicated process, since the resin must be hardened in a suitable mold (for example by polymerization, see EP 48992 a 2). The application of ceramic glazes from the ceramic industry, which is additionally described in DE 19529627C 1, is disadvantageous for ceramic glazes which melt at the temperatures specified above and contain lead to a large extent and therefore no longer permits use in most countries. It has also been demonstrated that such ceramic glazes are often themselves porous, so that a film applied to a layer of dielectric material may itself be porous. In which case the occurrence of short circuits cannot be ruled out at all.

Disclosure of Invention

It is an object of the present invention to provide a circuit carrier and a method for producing the same, which avoid the above-mentioned disadvantages of the prior art.

The object is achieved by a circuit carrier comprising a metallic carrier layer on which a dielectric layer is arranged at least in regions, which dielectric layer has a multiplicity of pores, which pores are sealed with glass at least on the side of the dielectric layer facing away from the carrier layer, wherein the surface of the side of the dielectric layer facing away from the carrier layer is substantially free of glass outside the region of the pores sealed with glass. The object is also achieved by a method for producing the circuit carrier, in which a layer of dielectric material is applied to a metallic carrier material, wherein glass is applied to the circuit carrier during or after the application of the layer of dielectric material.

The use of glass as a sealing material according to the invention has the advantage over the use of resins that the glass does not have to be hardened in a separate process step.

In particular, it can be provided that the glass is applied in a thermal spraying method. This is preferably done simultaneously with the thermal ejection of a layer of dielectric material, shortly called dielectric layer. In both cases the hardening of the glass is carried out automatically by cooling.

It is also possible to provide that the glass is painted or overprinted (for example by screen printing) onto the layer of dielectric material. In this case, the hardening can be carried out in an oven.

The use of glass has the advantage over the application of ceramic glazes described in the prior art that the glass does not have to contain lead and that it has no pores after application.

It is particularly advantageously provided that the surface of the side of the dielectric layer facing away from the carrier layer is substantially free of glass. This can be achieved by removing the glass from the surface of the dielectric layer or, in the case of a thermal spray method, by selecting suitable process parameters.

The conductor tracks can be applied to the encapsulated dielectric layer in a known manner. The finished circuit carrier can have electrical and/or electronic components. To produce the conductor tracks, a conductive paste can be applied to the dielectric layer and subsequently baked. The application of the paste can preferably be carried out in a screen printing or spraying method.

For example, a ceramic material, preferably aluminum oxide (Al), can be used for the dielectric layer₂O₃) Or aluminum nitride (AlN).

For example, it is possible to provide glasses made of bismuth trioxide, aluminum oxide, silicon dioxide or boron trioxide or mixtures of two or more of the aforementioned components. In one possible embodiment, it can be provided that the glass used is made of 55% bismuth trioxide, 21% aluminum oxide, 14% silicon dioxide and 10% boron trioxide. Is suitable forThe glass of (D) may be obtained, for example, from the company Ferro Corporation, 1000Lakeside Avenue, Cleveland, Ohio44114-7000, USA) ((S)www.ferro.com) Thus obtaining the product.

The desired sealing of the pores can be achieved with a quantity of sealing material (glass) of about 5% to 30% of the total quantity of dielectric material and sealing material (glass).

The metallic carrier layer can be made of aluminum or copper, for example.

If plasma spraying is chosen as the thermal spraying method, it should be noted that most sealing materials in powder form are selected with such a particle size and melting temperature that the sealing material can be sprayed onto the metallic carrier material without burning up to the necessary spraying temperature, for example 2100 ℃.

For example, Al having a particle size of 5 μm to 60 μm (typically 5.6 μm or 22.5 μm) and a melting temperature of 2050 ℃ can be used₂O₃And (3) powder.

In all exemplary embodiments, it is preferably provided that the layer made of metallic carrier material simultaneously serves as a mechanically rigid carrier for all components of the circuit carrier.

Drawings

Further advantages and details of embodiments of the invention emerge from the figures and the associated description. Wherein:

FIG. 1 shows a schematic representation of an apparatus for carrying out the method according to the invention;

fig. 2a, 2b, 2c show a top view, a side view and a detail of a circuit carrier by means of the method device according to the invention.

Detailed Description

Fig. 1 shows the thermal spraying of a layer 3 of dielectric material onto a layer 2 of a metallic carrier material of a circuit carrier 1. A plasma gun 13 having a cathode 14 and an anode 15 is schematically depicted. The arrow 16 indicates the transport of plasma gas. An arc is formed between the cathode 14 and the anode 15 by high frequency ignition, which results in ionization of the plasma gas. The plasma thus generated leaves the burner at a high velocity (about 300 to 700m/s) and a temperature of about 15000 to 20000 ℃. The material to be applied to the layer 2, indicated by the arrow 18, is introduced into the plasma beam by means of an introduction device 17, whereupon it is melted by the plasma beam and accelerated to a high speed. The molten material impinges at high speed on the metallic carrier layer 2 (beam 19) and is deposited there as a layer 3 of dielectric material (dielectric layer 3 for short). In a preferred embodiment, the mixture of sealing material (glass 9) and dielectric material is jointly introduced into the plasma beam by means of an introduction device 17.

Fig. 2a shows a top view of a circuit carrier 1, on whose dielectric material layer 3 printed conductors 4 and electrical or electronic components 5 are arranged. In this embodiment, the metallic carrier layer 2 is made of aluminum, which is cleaned and roughened by means of a sand blasting technique before thermal spraying. Holes 8 are provided at the four corners of the metallic carrier layer 2, through which the circuit carrier 1 can be screwed in later on. Also visible in fig. 2a are a twenty-quadrupole multi-head connector 6 and a nine-pole multi-head connector 7. The described electrical or electronic components 5 relate to microcontrollers, regulators, trigger circuits, high-power transistors and resistors.

The printed conductor 4 is printed after the thermal spraying of the dielectric layer 3 and then sintered at a temperature between 400 ℃ and 530 ℃. Next to the printed conductor tracks 4, a solder paste layer is applied by means of stencil printing (schablonendrack), in which an electrical or electronic component 5 is inserted.

The component 5 and the multi-head connectors 6, 7 are provided to be soldered to the circuit carrier 1 at the same time.

In order to obtain the desired heat dissipation of the electrical or electronic components 5, all electrical or electronic components 5 are mounted directly (i.e. without an intermediate carrier) on the circuit carrier 1 (on the dielectric layer 3 of the circuit carrier).

Fig. 2b shows the layer structure of the circuit carrier 1 according to the invention. The figure is of course not to scale. The thickness of the carrier layer, e.g. of metal, may be 2 to 10mm, typically 1 to 5mm, while the dielectric layer 3 typically has a thickness of 30 μm to 70 μm.

Fig. 2c shows a detailed view of the circuit carrier 1 depicted in fig. 2a and 2b in the region of the dielectric layer 3. Pores 20 are visible, which are arranged in the dielectric layer 3 and which are sealed by means of the glass 9. It can also be seen that the surface of the dielectric layer 3 is substantially free of glass outside the area of the pores 20.

Claims (15)

1. Circuit carrier, comprising a metallic carrier layer, on which a dielectric layer is arranged at least in places, which dielectric layer has a plurality of pores, which pores (20) are sealed with glass (9) at least on the side of the dielectric layer (3) facing away from the carrier layer (2), characterized in that: the surface of the side of the dielectric layer (3) facing away from the carrier layer (2) is free of glass (9) outside the region of the pores (20) sealed with glass (9).

2. The circuit carrier of claim 1, wherein: printed conductors (4, 4') are arranged on the dielectric layer (3).

3. The circuit carrier of claim 1 or 2, wherein: an electrical and/or electronic component (5) is arranged on the circuit carrier (1).

4. The circuit carrier of claim 1 or 2, wherein: the material of the dielectric layer (3) is a ceramic material.

5. A circuit carrier as claimed in claim 4, characterized in that the material of the dielectric layer (3) is aluminum oxide or aluminum nitride.

6. The circuit carrier of claim 1 or 2, wherein: the glass (9) is made of bismuth trioxide, aluminium oxide, silicon dioxide or boron trioxide or a mixture of two or more of the above-mentioned components.

7. The circuit carrier of claim 6, wherein: the glass is made of 55% of bismuth trioxide, 21% of alumina, 14% of silicon dioxide and 10% of boron trioxide.

8. The circuit carrier of claim 1 or 2, wherein: the amount of glass (9) is 5% to 30% of the total amount of dielectric material and glass (9).

9. Method for manufacturing a circuit carrier according to one of claims 1 to 8, in which method a layer of dielectric material is applied to a metallic carrier material, characterized in that: during or after the application of the layer of dielectric material, glass (9) is applied to the circuit carrier (1).

10. The method of claim 9, wherein: the dielectric material layer is applied to the metallic carrier layer (2) by a screen printing method.

11. The method according to claim 9 or 10, characterized in that: the glass (9) is painted or overprinted onto the layer of dielectric material.

12. The method of claim 9, wherein: the dielectric material layer is thermally sprayed onto a carrier layer (2) of metal.

13. The method of claim 12, wherein: the dielectric material layer is thermally sprayed together with the glass (9) onto a carrier layer (2) of metal.

14. The method according to claim 9 or 10, characterized in that: in order to produce the conductor tracks (4, 4'), a conductive paste is applied to the dielectric layer (3) and subsequently baked.

15. The method of claim 14, wherein: an electrically conductive paste is applied to the dielectric layer (3) by screen printing or spraying and is subsequently baked.