JPS62176187A - Manufacture of large current capacity circuit board which facilitates wire bonding - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a circuit formation on a 14-grade gold 14-complex gold foil-covered board, and more specifically, a method that allows a large current to flow through the circuit pattern, and This invention relates to a method for manufacturing a large current power module substrate that can also be wire sanded.

(Prior art) Conventionally, in order to manufacture a board that has the functions of both wire sanding and general purpose use, thick copper foil of 70 μm (2 ounces) or 105 μm (6 ounces) was used. It was necessary to form a circuit and plate the circuit with a noble metal or a base metal such as N1, or to bond a wire-bondable metal piece such as an Aj piece onto a thick copper foil.

However, etching thick copper foil takes time, plating is expensive and it is difficult to obtain a uniform plated surface, and joining metal pieces is only possible when there are many Ta.

In contrast, a more sophisticated method has been used in which a substrate laminated with a composite metal foil of aluminum and copper is used, and an aluminum bonding pad is formed by etching (Japanese Unexamined Patent Publication No. 58-48432). ). The characteristics of this aluminum bonding pad are that it is possible to form a large number of aluminum pads at the same time in a desired location with good reproducibility by etching, and because ultra-shinba bonding using aluminum wire creates an aluminum-aluminum bond, The scope of work is wide and reliability is high.

(Problems to be Solved by the Invention) In recent years, there has been a strong demand for substrates on which power elements can be integrated. In particular, power module substrates such as inverters are becoming increasingly high output, and it has become important to have high thermal conductivity and wire bonding properties as well as the ability to carry large currents.

However, since the copper foil used in the above-mentioned InuKame diversion is thick, etching takes time and costs are high, and it is difficult to form high-quality circuits (Special Publications Publication No. 54-8).
510) and difficulty in forming a wire bonding pad.

Therefore, it is possible to use a board made by laminating composite metal foil of aluminum and copper as described above, but in this board for high-density circuits, the copper foil is too thin to carry a large current, so thick copper is partially attached. A manufacturing method for plating was devised.

That is, to give one example, an aluminum foil 3 is placed on the base 1.
A plating/etching resist ink 4 was formed by screen printing on the aluminum/copper foil clad substrate shown in FIG. 6, which had the upper layer and the copper foil 2 as the lower layer (FIG. 7). Next, after only the aluminum foil 3 is selectively etched (
(Fig. 8), and the thickness of copper plating 5 is 70 μm (Fig. 9).
After the resist 4t is peeled off, the etching resist ink 6 is completely printed (FIG. 10), aluminum etching and copper etching are performed (FIG. 11), and finally the resist ink 6 is peeled off.

However, while the thickness of the resist 4 formed by screen printing in the above manufacturing method is as thin as 10 to 20 μm,
Since the thickness of the thick steel plating 5 is as thick as 70 μm, it is made into a shape with protrusions on both sides of the rectangular shape shown in FIG. There was a drawback that wires were easily broken at these positions during etching.

In order to solve this problem, it was necessary to prevent the plated copper from appearing on both sides 9111 of the door in Figure 9. As for how to solve this problem, it is clear that the resist should be as thick as possible, preferably as thick as possible than the plated surface, and that the resist wall should be as close to vertical as possible. became.

As a result, it was possible to form a thick resist film at one time, and the walls of the mesh resist were nearly vertical, thereby completing an easy manufacturing method using a dry film.

(Means for Solving the Problems) In other words, the invention is to form an elastane register in a desired portion of a composite foil-clad insulating substrate using a heterogeneous metal composite, and selectively apply only the upper metal foil of the dissimilar metal composite foil. The process of etching the
After peeling off the etching layer l-', a dry film is attached to the selectively etched surface of the insulating substrate to form a desired pattern, and the exposed upper layer gold of the dissimilar metal composite foil is selectively etched to form a desired pattern. A wire-pondable wire-pondable wire-plating method comprising a step of thickly plating copper on the etched portion, and a step of etching the lower metal foil of the dissimilar metal composite foil after peeling off the dry film. This is a method for manufacturing circuit boards.

The present invention will be explained in more detail below with reference to the drawings.

FIG. 5 shows a 1v board of circuit #5 manufactured by the manufacturing method of the present invention, which consists of an insulating base 1 on which an insulating layer 5 is provided, and a copper foil 2 which is a lower layer of a different metal Enokidai foil. This is a cross section showing a circuit, a circuit made of aluminum foil 3 which is the upper layer of the composite foil, and a copper circuit formed by thick copper plating 5.

The process of manufacturing the circuit board shown in FIG. 5 begins with the process of manufacturing the circuit board shown in FIG. Using a metal composite Nabari insulating substrate, an eratin register is formed in a desired pattern on the aluminum foil 3, which is the upper layer metal of the Heterogeneous Sparrow M edge foil. This resist can be formed by screen printing method (using resist ink) or photo method (dry film or liquid photoresist).
But that's fine.

Next, the aluminum foil 3 is selectively etched using an aluminum selective etching agent. After peeling off the etching resist, a plating dry film 7 with a resist thickness of 60 μm or more is laminated at a desired location, and then the dry film 7' where thick copper plating 5 is to be applied is developed and removed using a photo method. (Fig. 1), then complete selective etching of aluminum (Fig. 2). Next, thick copper plating 5 is performed (FIG. 6), and after the dry film 7 is removed from the IJ as shown in FIG. 4, the copper foil 2 is selectively etched to produce the circuit board shown in FIG. 5.

In addition, in the present invention, as an alternative method, as the next step of the work shown in FIG. 4, etching resist is formed on the entire pattern by screen printing method or photo method, and then copper etching is performed, and then the etching resist is peeled off. The circuit board shown in FIG. 5 can also be created by this method.

According to the method according to the present invention described above, as shown in FIG. Therefore, patterns with high positional accuracy can be formed. In addition, there are no protrusions on both ends of the thick copper plating 5 o'clock as shown in Figure 9, and there is no process that is likely to cause wire breakage as shown in Figures 10 to 11, so reliability is high. A circuit can be formed.

The insulating base of the dissimilar metal foil-clad insulating substrate used in the present invention includes:
Paper phenolic resin, glass epoxy resin, etc. are available, but thermally conductive metal plates such as aluminum, copper, aluminum foil, copper alloy, and alumite may also be insulated for strength reasons. In particular, thermosetting epoxy resins, polyimide resins, and phenol resins that contain inorganic powders with good thermal conductivity, such as alumina powder, boron nitride powder, beryllia powder, magnesia powder P, and quartz powder, etc. Polydactyly has good thermal conductivity and is preferable as a resin for insulating the metal plate.

Plating-resistant dry film used in the present invention? ``i, resistance''
R-resolved copper plating properties and copper etching resistance are required.

Generally, the thickness of the resist depends on the thickness of the copper to be thickly plated, but a resist thickness of at least 60 .mu.m is required, and at most 600 .mu.m. If the resist is thicker than this, exposure and development will not go well, and it is not practical to use a resist that requires more than one person's supervision.

Next, the material that can be applied to the substrate used in the present invention is aluminum foil and 7-3 pieces of copper rolled and pressed together. There are foils plated with nickel on aluminum foil, foils with J1 shell plating on aluminum foil, and foils with aluminum vapor-deposited on copper foils. Here, the aluminum part is necessary to serve as a wire bonding pad when mounting a semiconductor bare chip. There are also alternatives to aluminum such as nickel, gold, and silver.

Further, the thick copper plating on the @@ foil of the present invention is performed by electrolytic plating. This thick copper plating is for carrying a large current, and the plating thickness, including the fabric, is preferably 65 μm or more, preferably 45 to 300 μm, and more preferably 50 to 150 μm.
It is. If the plating thickness is less than 65 μm, it will not be possible to obtain a Taisei distribution area, and there is no upper limit, but from a cost perspective
The limit is around μm.

The selective etching agent for copper used in the present invention includes, but is not particularly limited to, peroxide-based etching agents such as ammonium persulfate bath solution and sulfuric acid/hydrogen peroxide-based etching agents.

On the other hand, as a selective etching agent for aluminum, a solution prepared by adding various additives to an inorganic strong alkaline bath solution such as a caustic soda bath solution or a caustic potash bath solution is used.

Next, there are two methods for thick copper plating: Seishin Rikiji plating in a shukuchu bath and birophosphate steel plating in an alkaline bath, but I am not particularly satisfied with either method.

■The main point is that the plating is thick, so it can be plated quickly and uniformly.

(Example) The process of the present invention will be briefly explained with reference to an example, but the invention is not limited to this.

Example 1 As a metal-based highly thermally conductive substrate, a composite metal foil consisting of a 40 μm aluminum foil 3 (upper layer) and a 10 μm copper foil 2 (lower layer) was used as a filler.
A HITT plate (manufactured by Kamekikagaku Kogyo Co., Ltd., trade name) was used, which was laminated on the substrate 1 of a 6.0 mm aluminum plate with a 6.0 μm (80 μm) interposed therebetween. The surface of the substrate was coated with an adhesive and laminated with a protective film 9 made of polysalt or vinyl film. A slightly alkali-resistant etching resist ink was printed on the aluminum oil 3 by screen printing and dried. Then, selective etching was performed using a caustic soda-based etching agent to expose the lower copper foil 2.

A bath development type dry film 7 (Fig. 1) with a thickness of 50 μm, Riston 1220 (manufactured by DuPont, trade name), was coated with a hot roll laminator.
The aluminum foil 3 was exposed using a mask film and developed at 20°C in chlorocene (Fig. 1).Then, the aluminum foil 3 was selectively etched with a caustic powder yarn etching agent, which is a selective etching agent for aluminum. (Fig. 2). After degreasing and pickling the dry film-covered substrate, it was heated to 4 A/d in an acidic steel plating bath at 35°C.
Electrolytic copper plating was carried out under the conditions of 80 minutes and 80 minutes (Fig. 6).The thickness of the copper foil 2 after plating was about 90μ.

Next, the dry film 7 was peeled off with methylene chloride (Fig. 4) and etched at 52°C using sulfuric acid/hydrogen peroxide etching gL to obtain a pattern having a sharp cross section as shown in Fig. 5. Incidentally, the total copper oil thickness of the served pattern was about 80 μm.

Example 2 Using the same substrate as in Example 1, the circuit board shown in FIG. 4 was obtained through the same steps. Etching resist ink was formed on the entire pattern by arrow screen printing. After drying,
The excess copper foil was etched using a Makoto/perverted hydrogen etching tool, and then the etching resist was removed using chlorocene to obtain the circuit board shown in FIG. 5. The thickness of the rolled copper foil body was approximately 90 μm.

Comparative Example Using the same substrate as in Example 1, screen printing was performed six times to form an etching and plating resist similar to that shown in FIG. The resist thickness was 60 μm. Next, selective etching of aluminum was performed in the same manner as in Example 1. Example 1
It has the same plating treatment as the ft. Town m after thick plating
L has a shape similar to that of Figure 9, with arrowheads at both ends. Next, an etching resist was formed by screen printing in the same manner as in Figure 10, but the resist could not be printed between the protrusions at both ends of the thick plated part and the aluminum foil, so the circuit was etched using aluminum etching and copper etching. Some of the copper foil and aluminum foil required above are also etched, and ten circuits are #
'r# did.

(Effects of the Invention) As explained above, 2!11 The circuit board for wire bonding, which can be wire bonded and manufactured by the manufacturing method of the present invention, can be used for thick plating using a mesh resist formed by the screen printing method. There is no such problem with thick plated parts, and sharp and highly detailed patterns can be formed, so the defect rate is low and the circuit is characterized by low reliability.

[Brief explanation of drawings]

1 to 4 are process cross-sectional views of the manufacturing method of the present invention.
The figure is a complete hX cross-sectional view of the present invention. Further, FIGS. 6 to 11 show process side views of the conventional manufacturing method. No. 1...Base, 2...Copper foil, 3...Aluminum foil,
4°"・Plating and etching resist, 5.. Fast-applying plating, 6."Etching resist, RO"・Dry film, B...Insulating layer, S...Protective film. Patent applicant 1 Keikagaku Kogyo Co., Ltd. Tsuma 5

Claims (4)

[Claims] (1) Forming an etching resist on a desired portion of the dissimilar metal composite foil-covered insulating substrate, selectively etching only the upper metal foil of the dissimilar metal composite foil, and after peeling off the etching resist, etching the insulating substrate a step of laminating a dry film on the selectively etched surface of the foil to form a desired pattern; and a step of selectively etching the exposed upper layer metal of the dissimilar metal composite foil and plating the etched portion with thick copper. . A method for producing a large current circuit board capable of wire bonding, comprising the steps of: after peeling off the dry film, etching a lower metal foil of the dissimilar metal composite foil. (2) The method for manufacturing a large current circuit board according to claim 1, wherein the dissimilar metal composite foil is made of aluminum and copper. (3) The method for manufacturing a large current circuit board according to claim 1 or 2, wherein the upper metal foil of the dissimilar metal composite foil is aluminum. (4) The method for producing a large current circuit board according to claim 1, wherein the insulating layer provided on at least one main surface of the insulating substrate metal plate has good thermal conductivity.