JPH0373593A - Manufacture of flexible printed wiring board - Google Patents

Abstract

PURPOSE:To easily form solder resist having high reliability by coating with resist ink by a roll coating method or a dipping method. CONSTITUTION:A part not required to protect with solder resist (e.g. soldering land 4, etc.,) is covered with mask 5, both side surfaces and a through hole 2 of a wiring board 1 are then coated with resist ink 6 by a roll coating method or a dipping method, and the mask 5 is then removed. Thus, the resist ink of desired thickness can be formed on both side faces of the board 1, and the ink can be sufficiently filled in the hole 2. The edges of a copper foil 2a of the hole part and a signal wiring pattern 3 as well as the foil 2a of the inner wall of the hole can be sufficiently coated therewith.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of forming a solder resist for protecting a double-sided flexible wiring board.

<Prior Art> Methods for forming the above-mentioned solder resist include -S, such as a film coverlay method and an ink coverlay method.

The film coverlay method involves sandwiching a flexible wiring board between two films that have been processed into a predetermined pattern and coated with an adhesive on one side, and then bonding the two films together by thermocompression. This is a method of forming a solder resist. Figure 2 shows the structure of a flexible wiring board that employs this film coverlay method. Through hole 2
, an adhesive layer 22 is applied to both sides of the base material film 1 on which the signal wiring pattern 3 and the soldering land 4 are formed.
A film 21 is formed through the adhesive layer 22, and the 'd4fi2a of the through hole 2 and the signal wiring pattern 3 are covered with this adhesive layer 22.

Note that during soldering, the land 4 is open to the outside.

Further, the ink coverlay method is a method of forming an ink resist layer 31 by applying resist ink to both sides of the base material film 1 by a printing method, as shown in FIG.

<Problems to be Solved by the Invention> By the way, according to the film coverlay method, the through-hole 2 portion 1Fi2a and the signal wiring pattern 3 can be completely covered, and the reliability is high. A mold is required, which not only increases production costs but also requires a long time to manufacture the mold.Furthermore, it is necessary to use a thermocompression press to press the film 21, and the pressing process is difficult. The problem is that it is complicated and takes a lot of time.

On the other hand, although the conventional ink coverlay method has the advantage that the processing process is relatively simple, since almost no resist ink adheres to the Ii4 foil 2a on the inner wall surface of the through-hole, There is a high possibility that cracks will occur in the copper foil 2a in the through-hole area or wire breakage will occur due to foil surface treatment, thermal history, etc. Most of the time, it is exposed, and as a result, there is a drawback that it lacks reliability, such as the risk of short circuits due to solder debris during mounting.

The present invention was made in view of the above-mentioned problems, and it is an object of the present invention to provide a method by which a highly reliable solder resist can be easily formed.

<Means for Solving the Problems> As shown in FIG. 1 corresponding to the embodiment, the present invention covers parts that do not require protection with solder resist (for example, lands 4 for soldering) with a mask 5. (b) Next, the resist ink 6 is applied to both surfaces of the wiring board 1 and its through holes 2 by a roll coater method or a dipping method (C), and then the mask 5 is removed.

(Function) By applying the resist ink using a roll coater method or a dipping method, a resist ink layer of a desired thickness can be formed on both sides of the wiring board 1, and the through holes 2 can be sufficiently filled with the resist ink. As a result, the copper foil 2a in the through-hole portion, the edge portion of the signal wiring pattern 3, and the copper foil 2a on the inner wall surface of the through-hole portion
It becomes possible to sufficiently cover the

<Example> FIG. 1 is a diagram illustrating the procedure of a manufacturing method according to an example of the present invention.

First, as shown in (a), a signal wiring pattern 3 and a soldering land 4 are formed on the base material film 1 in the previous process, and a copper foil 2a is formed in the through hole 2. has been done.

Note that the signal wiring pattern 3 and the soldering land 4 are both formed of #l foil.

Now, for soldering, land 4 is covered with mask 5 (
b). The material of this mask 5 has poor wettability with respect to the resist ink applied in the next step, and
Use a material that can be easily removed with a solution that is not corrosive to copper, etc.

Next, the resist ink 6 is simultaneously applied to both sides of the base material film 1 by a roll coater method or a dipping method (C). At this time, since the mask 5 has poor wettability with the resist ink 6, The entire surface is not covered with resist ink, and a portion is exposed to the outside.

After drying the applied resist ink 6, by removing the mask 5 with a solution, the copper foil 2a of the through hole 2 and the signal wiring pattern 3 are completely covered with the resist ink 6, as shown in (2). coated with
By soldering, a flexible printed wiring board with only the lands 4 open to the outside is obtained.

<Effects of the Invention> According to the present invention, a solder resist is formed by applying resist ink using a roll coater method or a dipping method, so it is relatively easy to use without using an expensive film coverlay or its mold. A highly reliable solder resist can be obtained through a process that is easy to use. Therefore, it is possible to manufacture a flexible printed wiring board with high reliability comparable to that of a film coverlay at low cost and in a short delivery time.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the procedure of a manufacturing method according to an embodiment of the present invention. FIG. 2 is a sectional view showing an example of a tentative structure of flexible printed wiring in which a solder resist is formed by a film coverlay method. FIG. 3 is a cross-sectional view showing an example of the structure of a flexible printed wiring board on which a solder resist is formed by a conventional ink coverlay method. 1... Base material film 2... Through hole 2a... Copper foil 3... Signal wiring pattern 4... Land for soldering 5... Mask 6... Resist ink

Claims (1)

[Claims] A method of forming a solder resist to protect a flexible printed wiring board with circuits formed on both sides, in which parts that do not require protection with solder resist are covered with a mask, and then the ink resist is applied using a roll coater method or a dipping method. A method for manufacturing a flexible printed wiring board, characterized in that the mask is removed after coating both sides of the wiring board and the through holes thereof.