JPH0418789A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To enable a chrome layer to be etched and concurrently a tin plating layer to be formed by the use of an electroless tin plating solution so as to simplify a manufacturing process by a method wherein a copper circuit is formed on the chrome layer provided onto the surface of an insulating layer, then the disused part of the chrome layer is removed with an electroless tin plating solution, and concurrently a tin plating layer is provided onto the surface of the copper circuit. CONSTITUTION:A chrome layer 2 and a copper layer 1 are formed on a polyimide film 3 (insulating layer) as thick as 3nm and 10mum respectively through a magnetron sputtering method to form a board used for a flexible wiring board, and a photoresist 4 of required pattern is provided onto the surface of the copper layer 1. In succession, the copper layer 1 is etched with a copper etching solution kept at a temperature of 40 deg.C to form a copper circuit la. Then, the photoresist is removed with acetone, then a tin plating layer 5 is formed as thick as 0.3-0.6mum on the surface of the copper circuit la by the use of an electroless tin plating solution kept at a temperature of 60 deg.C, and concurrently the chrome layer 2 is etched.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for efficiently manufacturing a high-density printed wiring board.

[Traditional technique! [xIli] For flexible wiring boards to support high-density packaging, it is preferable to use a substrate material with a chromium layer as an underlayer to improve the tonal properties of the insulating layer and copper layer17 <Used.

Conventionally, such printed wiring boards are produced by etching a first copper layer to form a copper circuit, and then etching a chromium layer as a C1 underlayer along the copper circuit using an etching process for W.
After etching, 'I'-flll attachment is manufactured by going through three main steps of forming a tin plating layer on the surface of the copper circuit for the purpose of improving the properties.
There are 1.

This 1) Kyoto, chromium layer work, Nchingun night moss,
Acid, 1'1 [processing, soting solution (0,1-3mat/,
Hydrochloric acid aqueous solution of Q (For convenience, this will be referred to as Solution A), or Mao Zzingir, which is prepared by dissolving 115 g of ceric ammonium nitrate and 30 ml of 70% perchloric acid in 10,100O of water.
(For convenience 1-1, refer to this as B 1), or alkali + 11 processing/soching solution (potassium ferricyanide 1
40g and 90g of hydroxide. Water 10100O
An etching solution (for convenience, this will be referred to as solution C) dissolved in water at 2°C is used.

[Problem to be solved by the invention] However, in the conventional manufacturing method as described in ■--, when A and A are used as the coating solution for the chromium layer, If the film thickness is less than 5 nm, there is a problem in that the chromium layer is not completely removed, probably because a chromium oxide film is formed. On the other hand, when liquid C is used as an etching liquid, etching is possible regardless of the thickness of the chromium layer. There is a problem with not liking it.

Furthermore, when considering the reduction of processes in order to improve productivity and economy, it would be more rational if the copper layer and chromium layer could be etched at the same time with the same etching solution, but currently the copper layer No etching solution has been developed that can etch both the copper layer and the chromium layer. Even if such an etching solution were available, while etching the chromium layer, the etching solution would be Since the layer is further etched, the copper circuit may be over-etched, causing problems such as adversely affecting pattern accuracy (etching factor, bit width, etc.).

This invention was made in view of the above,
The object of the present invention is to provide a method for manufacturing a printed circuit board and a wiring board that can efficiently form a high-density fine circuit having a chromium layer as an underlayer.

[Means for Solving the Problems] The present invention provides a method for manufacturing a printed wiring board in which a circuit having a laminated structure of a chromium layer, a copper layer, and a tin plating layer is formed on ten insulating layers. A copper circuit is formed on the rolled chromium layer-F, and then an unnecessary portion of the chromium layer is removed by etching using an electroless tin plating solution, and at the same time, a tin plating layer is provided on the surface of the copper circuit. In particular, the above tasks have been achieved.

[Operations] In the present invention, an electroless tin plating solution (generally containing stannic chloride as a main component and also containing sulfur compounds, fluoride compounds, etc.), which has not been considered as an etching solution in the past, is used. The chromium layer is then etched. That is, in the present invention, instead of reducing the number of steps by forming and etching the copper layer and the chlorine layer at the same time, the copper circuit is formed first, and then the process is performed in two steps. Etching of the chromium layer and tin plating are carried out simultaneously in one process in an effort to streamline the process. In addition, the present invention
As described above, the copper layer and the chromium layer are formed separately, and the etching of the copper layer does not proceed depending on the electroless tin plating solution, so that over-etching of the copper layer due to etching of the chromium layer does not occur.

If the thickness of the chromium layer of the present invention is in the range of 0.5 to 1100 nm (which sufficiently covers the thickness range of a normal underlayer), there will be no particular problem, or high-precision etching can be performed.
It is desirable that the film thickness be ~5 nm. As the electroless tin plating solution to be used, an acidic plating solution containing stannic chloride as a main component is more preferable.

On the other hand, the thickness of the copper layer and the method of forming the circuit are not particularly limited, and the copper circuit may be formed by a semi-additive method instead of the subtract method.

In addition, as an insulating layer when forming a high-density microcircuit, polyimide film, fluorine film (so-called Teflon film), polyethylene film, polypropylene film, etc. are preferably used, among which #i is used. A polyimide film is particularly preferable from the viewpoints of properties, chemical resistance, one-dimensional stability, and the like.

[Example] Example FIGS. 1(a) to 1(c) show production J of the first embodiment of the present invention.

FIG.

First, add chromium 15 to polyimide film 3 (insulating layer) soil.
A substrate for a flexible printed wiring board was prepared by forming a copper layer of 3 nm 2 and a copper layer of 10 μm 1 by magnetron sputtering, and as shown in FIG. Ta.

Subsequently, the copper layer 1 was etched with a copper etching solution (ferric chloride aqueous solution) at a temperature of 40° C. to form a copper circuit 1a shown in FIG. 1(b). Next, after removing the photoresist with acetone (Fig. 1(b)), the temperature was 60°C.
Using an electroless tin plating solution (Enplate-TlN421 Special, manufactured by Meldex), a tin plating layer 5 of 03 to 06 μm is provided on the surface of the copper circuit 1a, and at the same time, the chromium layer 2 is etched (the copper circuit 1a is etched). A flexible printed wiring board as shown in FIG. 1(C) without 1-] (which becomes a resist) was obtained.

Then, when we measured the insulation resistance value between patterns for the flexible printed wiring board sample prepared by C5, we found that
It showed the same value as the one without the chromium layer as the underlayer (the specifications such as the patterning method were the same as in Example 1).

Example 2 First, 3n layers of chromium were formed on the polyimide film (insulating layer).
A substrate for a flexible printed wiring board was prepared by forming a copper layer of 1 m and a copper layer of 0.1 μm in thickness by magnetron sputtering, and then forming a 10 μm copper layer on the other 1 m by electrolytic copper plating.

After providing a photoresis I in a desired pattern on the surface of the copper layer of this substrate, a copper etching solution (
The copper layer was etched with a ferric chloride aqueous solution to form a copper circuit. Next, after removing the photoresist with acetone, the temperature is 80°C! ! ! ! Using electrolytic tin plating (Enplate-TIN421 manufactured by Special Meltex Co., Ltd.), a tin plating layer of 03 to 06 μm was provided on the surface of the copper circuit, and at the same time, the chromium layer was etched.

When the insulation resistance value between the patterns was measured for the produced flexible printed wiring board sample, it was found that the insulation resistance value between the patterns was equivalent to that of the 2t one with a chromium layer as the base layer (the specifications such as pattern dimensions are the same as in Example 2). The value was shown.

Example 3 First, a 3n chromium layer was placed on the polyimide film (insulating layer).
A substrate for a flexible printed wiring board was prepared by forming a copper layer of 01 μm in thickness and a copper layer of 01 μm in thickness by magnetrin sputtering. A so-called reverse pattern that exposes the part of the copper layer of the board that will become the circuit of the desired pattern shape)
A photoresist was prepared, and copper plating was applied to the portions corresponding to the circuit by electrolytic copper plating until the total thickness was 10 μm. In Table 9, the photoresist was removed by 1≦ with acetone, and the entire copper layer was flash-etched to a depth of 02 μm using a copper etching solution (ferric chloride aqueous solution) at 40°C. Completely removed unnecessary parts. Furthermore, using an electroless tin plating solution (ENBLEH-TIN421 Special made by Meltex Co., Ltd.) at 60°C, 03 to 0 was applied to the surface of the copper circuit.
After a 6 μm tin plating layer was provided, a chromium layer was etched on the same surface.

Then, the insulation resistance (m) between the patterns was measured for the prepared flexible printed wiring board sample.
It showed the same value as the one without the chromium layer as the base layer (specifications such as pattern dimensions are the same as in Example 3).

Comparative Example FIGS. 2(a) to 2(d) are cross-sectional views schematically showing manufacturing steps according to a comparative example.

First, a polyimide film 103 (insulating layer), a chromium layer 3 nm thick, 02, and a copper layer 1 m thick 101 were formed by magnetron sputtering to prepare a substrate for a flexible printed wiring board, as shown in Figure 1 (a). Next, a photoresist 104 having a desired batten shape was provided on the surface of the copper layer 101. Subsequently, the copper layer 10 was etched using a copper etching solution (ferric chloride aqueous solution) at a temperature of 40.degree. C. to form a copper circuit 101a as shown in FIG. 1(b). Then, after removing the photoresist by acetone (
Figure 1 (b)), chromium etching at 40°C for 7 nights (140 g of potassium ferricyanide and 90 g of hydroxide, dissolved in 1000 ml of water), the chromium layer was etched as shown in Figure 2 (C). +02 was etched (the copper circuit 10]a became an etching resist).

After that, 60℃ electroless tin plating solution (ENBRAY 1・T
Using IN421 Special (manufactured by Meltex),
Tin hole layer 1 with a thickness of 0.3 to 06 μm on the surface of the copper circuit 101a
05 was installed, and a 12-frame L xyple printed wiring board as shown in FIG. 1(d) was obtained.

In the method of this comparative example, it appears that the chromium layer edging step (Fig. 2 (C)) is increased by one inch compared to the method of the example, but in reality, the chromium layer edging process (Fig. 2 (C)) is increased by one inch. In addition to the layer edging process, there are problems with washing and drying the culm, dropping the culm, and treating wastewater, making it significantly inferior in terms of productivity and economy compared to the production method according to the present invention.

In addition, in the example described in -17, the method for manufacturing a flexible printed wiring board using a resist is explained, and it goes without saying that the method of the present invention can also be applied to a rigid printed wiring board. However, depending on the pattern density, an etching resist for the copper circuit may be formed by a method such as printing.

[Effects of the Invention] Above J: In the present invention, etching and tin plating of the chromium layer are simultaneously performed using an electroless tin plating solution. Problems such as environmental pollution caused by wastewater treatment of etching solution can also be solved.

That is, according to the present invention, it is possible to significantly improve the productivity and economy in manufacturing printed wiring boards that have a laminated structure of a chromium layer, a copper layer, and a tin plating layer. For example, λ is TAB (Tape Automat) used when surface mounting l-SI etc.
It is possible to efficiently manufacture a flexible printed wiring board for ED bonding.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(c) show the manufacture of the first embodiment of the present invention.
A schematic cross-sectional view of the culm, Figure 2 (a) = Cd)
FIG. 3 is a cross-sectional view schematically showing the manufacturing process of a comparative example. [Explanation of symbols of main parts] 1... Copper layer 1a... Copper circuit 2... Chrome layer 3... Polyimide film 4... Photoresist 5...Tin plating layer] 2

Claims (1)

[Claims] A method for manufacturing a printed wiring board in which a circuit having a laminated structure of a chromium layer, a copper layer, and a tin plating layer is formed on an insulating layer, wherein a copper circuit is formed on a chromium layer provided on the surface of the insulating layer. , and then removing unnecessary portions of the chromium layer by etching using an electroless tin plating solution, and at the same time providing a tin plating layer on the surface of the copper circuit.