JPS622591A - Manufacture of metal base hybrid integrated circuit board - 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 manufacturing method for forming a hybrid integrated circuit pattern using a composite foil of different metals, and more specifically, relates to a manufacturing method for forming a hybrid integrated circuit pattern using a composite foil of different types of metals, and more specifically, to a manufacturing method for forming a hybrid integrated circuit pattern using a composite foil of different metals. The present invention relates to a method for manufacturing a metal-based hybrid integrated circuit board for high power use.

(Conventional technology) Ceramic substrates have traditionally been widely used as substrates for hybrid integrated circuits, but in recent years, metal-based substrates have been used in some areas due to their superior heat dissipation, thermal conductivity, and workability. It has already come to be used in large quantities.

When mounting a semiconductor bare chip on this metal base substrate, so-called wire bonding using an aluminum wire or gold wire is essential from the bare chip that has been bonded. In particular, since aluminum wire is inexpensive and essential for wire bonding of power devices, it has been necessary to form so-called bonding pads on the circuit for ultrasonic wire bonding of this aluminum wire.

Methods for forming this bonding pad include plating and adhesion of metal pellets, but a new method uses a substrate made of composite metal foil of aluminum and copper, and forms an aluminum bonding pad by etching. A method has been used to
Publication No. 32 Akira This aluminum bonding pad is characterized by the fact that it is possible to form a large number of aluminum pads at a desired location with good reproducibility by etching, and because ultrasonic sanding with an aluminum wire results in an aluminum-aluminum bond. It has a wide range of work and is highly reliable.

(Problems to be Solved by the Invention) In recent years, there has been a demand for higher-density packaging of hybrid integrated circuit boards, and there has been a strong demand for circuit boards on which power elements can be integrated. In particular, in substrates for power modules such as inverters, in addition to the above-mentioned heat dissipation, high thermal conductivity, and wire bonding properties, even the 18 μm or 65 μm thick copper foil normally used for printed circuit boards lacks current capacity. Therefore, a thicker conductor was required.

However, it has been difficult to meet the above requirements with a metal-based substrate. For example, although copper foil for large currents is commercially available, this foil is thick and etching, which is the process of forming a circuit, takes time, resulting in high costs.
It is difficult to form high-density circuits (Special Publication No. 54-8510
The drawbacks were that the wire bonding pad was difficult to form.

Therefore, metal-based substrates made by laminating composite metal foils of aluminum and copper mentioned above are attracting attention, but in order to form high-density circuits, the copper foils must be thin, and they have the disadvantage that large currents cannot flow through them. was.

The present invention aims to solve this drawback and improve the ability of a large current to flow through a heterogeneous composite foil-covered metal base board.By plating locally on the circuit pattern, a metal base that enables the flow of a large current. A method of manufacturing a hybrid integrated circuit board is provided.

(Means for Solving the Problems) That is, the present invention provides circuit formation on a metal substrate in which composite foils of different metals are laminated on at least one main surface of a metal plate with an insulating layer having good thermal conductivity interposed therebetween. , step 1 of masking the surface of the metal base substrate where the metal is exposed; a step of providing a plating resist and an etching resist in areas other than the areas to be thickly plated; and removing the upper layer metal by selective etching with an etching agent; A step of thickly plating the substrate, a step of removing the plating resist and etching resist, a step of providing an etching resist in the portion that will become the finished product circuit pattern, etching it with an etching agent, and then removing the etching resist. This is a method for manufacturing a metal paste hybrid laminated circuit board characterized by comprising the following steps.

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

FIG. 1 shows a circuit board manufactured by the manufacturing method of the present invention, in which a copper foil 3 and an aluminum foil 4 made of a dissimilar metal composite foil 11 are etched on a base metal plate 1 with a thermally conductive insulating layer 2 interposed therebetween. FIG. 2 is a cross-sectional view showing the circuit pattern made by the above process and a thick plated portion 5 that becomes a large current carrying conductor.

Next, in the process of manufacturing the circuit board shown in FIG. 1, first, a base metal plate 1, a thermally conductive insulating layer 2, and a dissimilar metal composite foil-covered metal base board (FIG. 2), which becomes the dissimilar metal composite foil 11, are used. , a polyvinyl chloride film 9 is placed on the exposed surface of the base metal plate 1.
Mask with. In order to obtain an aluminum pad 4' for wire bonding during mounting using this base board, a plating resist/etching resist 9 is applied to the aluminum foil 4 at a portion corresponding to the desired circuit pattern, and the aluminum foil is etched with an etching agent. 4 by selective etching (FIG. 3). Next, a thick steel plated portion 5 is formed on the etched exposed surface of the copper foil 3 (FIG. 4), and the resist 9 is removed.

Further, to form a circuit pattern on the copper foil 3, which is the underlying metal of the dissimilar metal composite foil 11, it is covered again with an etching resist 10 (FIG. 5), and then etched with an etching agent to form a circuit, and finally the above-mentioned Etching resist 10
The circuit board shown in FIG. 1 is manufactured by removing the polyvinyl chloride 8 and peeling off the polyvinyl chloride 8.

Note that FIG. 6 is one of the application examples of mounting the power element 6 and thick aluminum wire 7 using the circuit board of FIG. 1 manufactured by the manufacturing method of the present invention.

The base metal plate 1 of the dissimilar metal composite foil-clad metal base substrate used in the present invention is preferably made of aluminum, copper, aluminum alloy, copper alloy, alumite, etc., which have good thermal conductivity, but the present invention is not limited thereto. .

The good heat conductive insulating layer 2 is made of a thermosetting resin such as epoxy resin, polyimide resin, and phenol resin, and a good heat conductive inorganic powder such as alumina powder, boron nitride powder, etc.
A blend of beryllia powder, magnesia powder, quartz powder, etc. is good in terms of heat conduction.

Next, the dissimilar metal composite foil 11 includes an aluminum foil 4 and a copper foil 3.
Foils made by rolling and pressure bonding, aluminum foil plated with copper, or aluminum foil plated with nickel and copper sequentially are used.

Further, the thick plating on the copper foil of the present invention is performed by electrolytic plating. This thick plating is for carrying large current.
The plating thickness is more than 65μm, preferably 45μm including the fabric.
μm~300μm1 More preferably 50μm~150
It is μm. If the plating thickness is less than 35 μm, a large current carrying capacity cannot be obtained, and although there is no particular upper limit, the upper limit is about 600 μm in terms of cost.

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 aqueous solution and sulfuric acid/hydrogen peroxide-based etching agents.

As a selective etching agent for partially aluminum, a solution prepared by adding various additives to an inorganic strong alkaline aqueous solution such as a caustic soda aqueous solution or a caustic potassium aqueous solution is used.

Furthermore, when etching aluminum and copper non-selectively, an etching agent such as a ferric chloride aqueous solution or a cupric chloride aqueous solution is used.

The plating and etching resist used in the present invention preferably has both acid resistance and alkali resistance, but when plating is carried out in an alkaline bath, it may be alkali resistant. Examples of such resists include some commercially available plating resists and dry films.

(Example) Examples of the present invention are shown below, but the present invention is not limited thereto.

Example 1 A composite metal foil consisting of a 40 μm aluminum foil (upper layer) and a 10 μm copper foil (lower layer) was laminated onto a 1.5 mm aluminum plate via a filler epoxy resin insulating layer (80 μm) as a metal-based highly thermally conductive substrate. HITT
A 7° rate (trade name manufactured by Denki Kagaku Kogyo Co., Ltd.) was used (second
figure).

First, the base aluminum plate of the HITT plate is laminated with a polyvinyl chloride film coated with an adhesive on the back side. Next, a plating resist/etching resist was printed on a desired portion of the aluminum foil of the composite metal foil, and after drying, selective etching was performed using a caustic soda-based etching solution to expose the underlying steel foil (FIG. 3).

Next, electrolytic plating was performed in a copper sulfate bath to give a copper thickness of 70 μm (
Figure 4). The resist ink on the obtained substrate was peeled off, an etching resist was printed (FIG. 5), and the aluminum was etched with a caustic soda-based etching solution, and then the copper was etched with an ammonium persulfate-based etching solution to form the entire circuit. Finally, the resist was removed and the film on the back surface was peeled off to produce a hybrid integrated circuit board (FIG. 1).

(Effects of the Invention) Since the metal-based hybrid integrated circuit board manufactured by the manufacturing method of the present invention has thick conductors due to thick plating,
In addition to being able to flow a large current, it has the advantage of being able to wire-bond semiconductor pellets directly because it has an aluminum binding pad.

In addition, by using thick plating, it can be used instead of a heat solder, so it is also possible to directly solder the power element.

Furthermore, fine patterns are also possible, and it has the feature that high-density packaging hybrid integrated circuit boards can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a circuit board manufactured by the manufacturing method of the present invention, and FIGS. 2 to 5 are sectional views of the manufacturing process of FIG. 1. Further, FIG. 6 shows a sectional view of an application example using the circuit board of FIG. 1.

Claims (4)

[Claims] (1) When forming a circuit on a metal substrate made by laminating dissimilar metal composite foils on at least one main surface of a metal plate with an insulating layer having good thermal conductivity interposed therebetween, the surface of the metal base substrate where the metal is exposed is a step of masking, a step of providing a plating resist and an etching resist in areas other than the areas to be thickly plated, a step of removing the upper layer metal by selective etching with an etchant, a step of further thickly plating the substrate, and a step of applying the plating resist to the plated resist. A metal-based hybrid integrated circuit board comprising the steps of: removing the etching resist; providing an etching resist on a portion that will become a finished product circuit pattern; etching with an etching agent; and then removing the etching resist. manufacturing method. (2) A method for producing a metal-based hybrid integrated circuit board according to claim 1, wherein the dissimilar metal composite foil is made of aluminum and copper. (3) A method for manufacturing a metal-based hybrid integrated circuit board according to claim 1 or 2, wherein the upper layer metal is aluminum. (4) The method for manufacturing a metal-based hybrid integrated circuit board according to claim 1, wherein the thick plating is copper plating.