JPS61284991A - Circuit formation for aluminum/copper composite lined 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 (Field of Industrial Application) The present invention relates to a circuit forming method by etching in the production of a hybrid integrated circuit board, and particularly to a circuit forming method for an aluminum/copper composite foil-covered board.

(Prior art) Recently, aluminum/copper composite foil-clad substrates have been used to form circuits in which both aluminum and copper metals are exposed, and the aluminum parts are used as wire bonding posts for semiconductors, and the net parts are used for soldering and circuits. A substrate for a hybrid integrated circuit using this method has been developed (Japanese Unexamined Patent Publication No. 58-48432). In this case, for example, as shown in FIGS. 4 and 5, when the board has aluminum 5 as the top layer, the circuit is formed by selectively etching the aluminum by covering the required portions of the aluminum 5 with an alkali-resistant resist 3 in the finished product pattern. Then, the copper 2 was selectively etched to form an acid-resistant resist 9 on the required portions of the finished product pattern.

(Problems to be Solved by the Invention) However, in the above method, when there is a joint between the aluminum pattern and the copper pattern, as shown in the comparative example shown in FIG.
b) and FIG. 5 (bJ), the acid-resistant resist 9 for forming a copper circuit is provided so as to overlap the aluminum 5. However, since there is a step between the copper 2 and the aluminum 5,
The printing method has the drawback that the acid-resistant resist 9 is printed on the joint 10 between the copper pattern and the aluminum pattern, but the resist ink often does not enter and the joint 10 is cut by etching. This phenomenon is shown in Figure 4 (b).
And the top layer metal foil (
This is likely to occur when the lower layer metal foil (steel 2 in the figure) is surrounded by aluminum 5) in Figures 4 and 5, or when the top layer metal foil is thick.
Even when forming a pattern using a dry film, the film is not laminated well on the stepped portions, and etching creates defective portions 6, resulting in the joining portions 10 being cut or becoming thinner.

The present invention solves these drawbacks, and by providing an etching resist on the circuit pattern surface with no steps, it prevents defects from occurring in the aluminum/copper composite bonding area, and improves the semiconductor function after mounting. The present invention provides a method for forming a circuit without any problems.

(Means for Solving the Problems) That is, the present invention provides a manufacturing method for forming a circuit pattern using aluminum/m composite foil cladding, in which a resist is provided over the entire final circuit pattern portion, and the aluminum/m composite foil cladding portion is 3. A first step of removing the resist, a second step of removing the resist, and a third step of applying the resist to a part of the final circuit pattern.
and a fourth step of selectively etching only the uppermost metal foil of the final circuit pattern with an etching agent.

Hereinafter, circuit pattern formation according to the present invention will be explained with reference to the drawings. FIG. 3 shows the substrate material before circuit pattern formation, with a composite foil made of aluminum 5 and steel 2 bonded to the upper layer of the substrate base material 7 and the insulating layer 4. In the present invention, using this substrate material, resist 8 is first applied to the entire desired circuit pattern portion in the order of (a), (b), (C) and (dl) shown in FIGS. 1 and 2. A metal circuit pattern of the aluminum/copper composite 1 is formed by etching with an etching agent.Then, the resist 8 is removed, and a resist film is applied to the uppermost layer of the circuit pattern where a desired metal foil pattern portion is to be formed. An alkali resist 3 is provided.In this case, it is preferable to form the alkali-resistant resist 3 to be larger than the desired pattern width, since the edges of the pattern will be protected during etching with the next etching agent, improving pattern accuracy.Next, the top layer By selectively etching only the metal foil with an etching agent, a circuit of the underlying metal foil is formed.Furthermore, by removing the alkali-resistant resist 3, aluminum 5 and copper 2 are removed.
A circuit can be formed in which both metals are exposed.

Further, in the substrate materials shown in FIGS. 1 and 2, the aluminum 5 of the aluminum/copper composite 1 is the top layer, but there is no problem even if the copper 2 is the top layer. It may be selected depending on the purpose.

The aluminum/copper composite foil used in the present invention may be a Clara r foil in which an aluminum foil and a copper foil are bonded together, a foil in which copper is plated on an aluminum foil, or an aluminum foil in which zinc and copper are sequentially plated. The circuit forming method of the present invention is not limited to any thickness as long as it is the aluminum/copper composite described above, but is preferably effective when the aluminum layer or copper layer that is the topmost metal layer is thick. , for example, the thickness is 25 μm or more. One of the reasons why such a thick metal foil is desired is the development of large current circuits based on the power generation of hybrid integrated circuits.

Further, the base material of the substrate in the present invention is not particularly limited, and paper phenol resin, glass epoxy resin, and metal plate having an insulating layer, which are generally used for printed circuit boards, can be used.

Furthermore, the etching agent used in the present invention is one that does not have selective etching properties for both aluminum and copper, and
Either of the two types of etching agents that are selective to aluminum and copper may be used. The usage of the acid-resistant, alkali-resistant resist, the acid-resistant resist, and the alkali-resistant resist is determined by the combination with the etching agent, and the type thereof does not matter.

(Example) Examples and comparative examples of the present invention are shown below.

Example 1 Aluminum layer thickness is 503 m1 Copper layer thickness is 10 μm
An aluminum/copper composite foil having a thickness of 1.0 m was laminated with a glass epoxy presol rig (total thickness: 1.6Ww1) to obtain a substrate with the aluminum surface as the top layer.

An acid-resistant etching resist was printed on the aluminum surface of the substrate in the pattern shown in FIG.
A circuit pattern with aluminum on the top and copper on the bottom was formed by etching with iron solution.

After peeling off the acid-resistant etching resist, as shown in FIG. After printing and drying an alkaline etching resist, only aluminum was selectively etched using a potential etching solution. Next, the resist ink was removed from the surface to obtain a completed circuit pattern as shown in FIG. 2(d) with a highly reliable joint between the aluminum pattern and the copper pattern. After making 100 samples, there were no defects in the aluminum and copper joints. The end face of the pattern at the joint between aluminum and steel had no side etching caused by the final aluminum etching, and the underlying copper was not exposed.

Example 2 The same aluminum/steel gold foil as in Example 1 was laminated onto a 1.5 mm thick aluminum plate with the aluminum side facing up via lath epoxy prepreg with a thickness of 100 μm, and the desired aluminum/@ composite foil-clad substrate was formed. Obtained.

The back side of the substrate was protected with &IJ vinyl chloride film, and then an alkali-resistant etching resist was printed on the aluminum surface of the substrate in the pattern shown in Figure 2 (a), and after drying, the top layer was removed with a sodium chloride etching solution. Only the aluminum was etched. Thereafter, selective etching of only copper was performed using an ammonium persulfate aqueous solution and the resist was removed to form a circuit pattern having copper under the aluminum.

Next, the width of the aluminum part on the circuit pattern is 0.0 mm wider than the pattern width formed to form the desired circuit pattern.
As shown in Figure 2 (C1), an alkali-resistant etching resist was printed with a pattern width 5 mm larger, and after drying, only the aluminum was selectively etched with a sodium chloride etching solution.Then, the liquid resist was removed from the surface, and the aluminum pattern was printed. Figure 2 (d
A finished product pattern of 1 was obtained. After making 100 samples, there were no defects in the aluminum and copper joints. Also, as in Example 1, there was no etch, and the copper in the lower layer was not exposed.

Example 3 Using the same substrate as in Example 2, using the pattern in Figure 2 (bl) instead of the pattern in Figure 2 (C), and using the same steps as in Example 2, 100 samples were made. did.

There were no defects at the joint between the aluminum pattern and the steel pattern. However, the end face of the pattern at the joint between copper and aluminum was side-etched by the final aluminum etching, so that about 50 μm of the underlying steel was exposed.

Comparative Example The same aluminum/copper composite foil-clad substrate as in Example 2 was used, except that an aluminum/copper composite foil in which the aluminum had a thickness of 40 μm and the steel had a thickness of 10 μm was used with the aluminum side facing up.

A polyvinyl chloride film was laminated on the back side of the substrate, and an alkali-resistant etching resist was screen printed on the finished aluminum pattern shown in FIG. 5(a).

After drying, only the aluminum was selectively etched using a porous aluminum etching agent. After removing the resist, an acid-resistant resist was screen printed so as to overlap the aluminum pattern and the copper pattern as shown in FIGS. 4(b) and 5(b). Next, selective etching of only the steel was performed using an aqueous ammonium persulfate solution, and the resist was peeled off to obtain the finished product pattern shown in FIG. 5(c). However, when 100 samples were prepared, more than 80 samples had defects as shown in FIG. 4(C), and some of the samples had been etched more than necessary due to copper etching. This is because the resist printing in FIG. 4 (bJ) was not successful due to the 40μ aluminum step.

(Effects of the Invention) As shown in the above Examples and Comparative Examples, the method according to the present invention can be used to form a circuit using aluminum/copper composite foil. This solves the problem of unsatisfactory reliability and yield due to poor etching resist formation. The circuit pattern obtained by the present invention allows for flexible circuit formation using aluminum and copper, such as wire bonding semiconductor pellets to aluminum circuits using aluminum wires, and using copper surfaces in areas where soldering is required. It is useful as a substrate for hybrid integrated circuits.

Furthermore, in the highly reliable circuit of the aluminum pattern and steel pattern joint obtained by the present invention, the thickness and solder-repelling properties of aluminum can be used to position semiconductor pellets and external leads when soldering. ■
It has the advantage of using copper patterns only in the areas that require soldering and aluminum patterns everywhere else, and can omit the overcoating of solder resist, which is generally done.It is used for hybrid integrated circuits with high current capacity and high reliability of aluminum-copper bonding. Substrates can be obtained in high yield.

[Brief explanation of the drawing]

FIGS. 1(a), (b) and (C) are cross-sectional views of the present invention, and FIGS. 2(a), (b), (c) and (d) are cross-sectional views of the present invention.
) represents a plan view of the invention. FIG. 3 shows a cross-sectional view of the base material before circuit pattern formation. Furthermore, FIGS. 4(a), (bl and (C)) are sectional views of the conventional example, and FIGS. 5(a), (b) and (C) are plan views of the conventional example.

Claims (4)

[Claims] (1) In the manufacturing method of forming a circuit pattern using aluminum/copper composite foil, the first step is to provide a resist over the entire final circuit pattern and etch the aluminum/copper composite foil with an etching agent. Aluminum/ Circuit formation method for copper composite foil-clad substrates. (2) The circuit forming method according to claim 1, wherein the resist in the third step is provided with a width larger than the circuit pattern width. (3) The circuit forming method according to claim 1 or 2, wherein the etching agent used in the first step does not selectively etch both aluminum and copper. (4) The first step consists of two types of etching agents that selectively etch only the upper layer of the aluminum/copper composite foil, and then selectively etch only the lower layer of the aluminum/copper composite foil. A circuit forming method according to claim 1 or 2, characterized in that: