JPH11312862A - Method for treating circuit pattern surface in printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a method for treating the surface of circuit pattern in a printed wiring board by which the dispersion among different kinds of metals can be prevented, even in a mixed circuit pattern made of different kinds of metals such as solder and gold, etc., and easy manufacture and reduction in cost. SOLUTION: This method is used to form other different kinds of metals, such as solder and gold, etc., on a circuit pattern which require surface treatment with other metal in a printed wiring board, in which circuit patterns 2 and 2' and a solder resist 4 are formed on a substrate 1. Furthermore, it consists of a step for forming solders 3 and 3' in a circuit pattern requiring surface treatment, a step for forming a solder resist 4' over the solder resist excluding a circuit pattern in which other kinds of metals such as gold and so on are formed, a step for removing the solder on the circuit pattern which is not covered with the solder resist 4', a step for forming different kinds of metal 5 such as gold, etc., on the surface of the circuit pattern 2' having no solder, by plating, etc., and a step for etching through laser beam the solder resist on the circuit pattern 2, on which the solder is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for finishing a surface of a circuit pattern formed on a printed wiring board with a dissimilar metal such as solder and gold.

[0002]

2. Description of the Related Art Conventionally, a circuit pattern formed on a printed wiring board has been coated with preliminary solder for soldering electric components. As a result, the oxidation of the circuit pattern is prevented, and the electric component can be easily soldered to the circuit pattern.

By the way, in recent years, in order to easily solder a small, high-precision electrical component of a surface type, a noble metal is used to prevent rust and smooth a part of the surface of a circuit pattern of a solder portion. For example, plating of gold is performed. However, in a certain type of printed wiring board, for example, a printed wiring board mounted on a spacecraft, a mixed circuit pattern in which a solder portion and a gold portion are finished is applied to a circuit pattern on one printed wiring board. May be required.

[0004]

Therefore, conventionally, gold plating is first performed on the surface of all the circuit patterns, and then, the gold is formed only on the circuit pattern to be the solder surface, and the gold is formed on the gold surface. Had gone. But,
According to this method, there is a disadvantage that gold diffuses into the solder and the strength of the solder is reduced. Therefore, in the surface finishing of the circuit pattern, it is necessary to perform the gold processing and the solder processing separately.

Therefore, the portion to be plated with gold is masked with a masking agent, the unmasked portion is solder-finished, and after removing the mask, the solder-finished portion is used for masking which can withstand gold plating. A gold plating process was performed by masking with a tape of No. 1 to form a gold surface on a circuit pattern other than soldering, and after the completion of the process, the masking tape was peeled off.

In this method, since the circuit pattern on the printed wiring board in recent years has a fine shape, the work of attaching the tape is very troublesome, and the time required for peeling off the tape after the gold plating process is reduced. However, there is a problem that the manufacturing cost becomes extremely high.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to prevent the diffusion of dissimilar metals even in a mixed circuit pattern of dissimilar metals such as solder and gold. Another object of the present invention is to provide a circuit pattern surface treatment method for a printed wiring board which can be manufactured easily and can reduce the cost.

[0008]

A first object of the present invention is to provide a circuit pattern surface treatment method for a printed wiring board which achieves the above-mentioned object. The first means is to form a circuit pattern and a solder resist on a substrate. In a method of forming another dissimilar metal such as solder and gold on a circuit pattern requiring surface treatment with another metal on the printed wiring board, a step of forming solder on the circuit pattern requiring surface treatment, A step of forming a solder resist by overlapping the solder resist except for a circuit pattern forming another dissimilar metal, a step of removing solder of the circuit pattern not covered by the solder resist, and Forming a dissimilar metal such as gold on the surface of the removed circuit pattern by plating or the like; and forming a solder layer on the circuit pattern on which the solder is formed. Characterized in that comprising the step of etching the strike by the laser beam.

The second means is to form another dissimilar metal such as solder and gold on a circuit pattern requiring surface treatment with another metal on a printed wiring board having a circuit pattern and a solder resist formed on a substrate. In the method, a step of forming solder on a circuit pattern requiring the surface treatment and an effect of preventing corrosion of solder at the time of plating the different metal except for a circuit pattern forming another different metal such as gold. A step of printing a strip mask, a step of removing solder of the circuit pattern that is not covered by the strip mask, and forming a dissimilar metal such as gold on the surface of the circuit pattern from which the solder has been removed by plating or the like. And a step of removing the strip mask formed on the solder surface.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a method for treating a circuit pattern surface on a printed wiring board according to the present invention will be described below with reference to FIG. First, the circuit patterns 2 and 2 'and the solder resist 4 are formed on the substrate 1 in the same manner as a normal printed wiring board. '(FIG. 1
a).

In this state, a solder resist 4 'is further formed on the solder resist 4 except for the solder 3' in the circuit pattern 2 'for forming gold (FIG. 1b). Next, the substrate 1 is immersed in a chemical that dissolves the solder 3 ', and the solder 3' not covered with the solder resist 4 is removed (FIG. 3c).

Next, the substrate 1 from which the solder 3 'has been removed is placed in a gold plating layer, and the circuit pattern 2' is plated with gold to form gold 5 (FIG. 1d). Thus, the gold 5 is formed only on the surface of the circuit pattern 2 '. Next, solder 3
Laser light is applied to the solder resist 4 'in the portion of the circuit pattern 2 where the
By exposing (FIG. 1e), a circuit pattern 2 'whose surface is formed only with gold 5 and a circuit pattern 2 whose surface is formed only with solder 3 can be manufactured.

Next, a second embodiment shown in FIG. 2 will be described. First, circuit patterns 2 and 2 'and a solder resist 4 are formed on a substrate 1 in the same manner as a normal printed wiring board (FIG. 2A). Next, solders 3 and 3 'are formed on the surfaces of the circuit patterns 2 and 2' requiring surface treatment (FIG. 2b), and gold is plated except for the portions of the solder 3 'in the circuit pattern 2' for forming gold. Then, a strip mask 6 for preventing corrosion of solder is printed (FIG. 2C).

The strip mask 6 comprises a rubber-based masking agent 6a and a resin-based masking agent 6b. First, a rubber-based masking agent 6a is printed on the solder 3, and then the resin-based masking agent 6b is printed.
Print. After the printing of the strip mask 6 is completed, the substrate 1 is immersed in a chemical for dissolving the solder 3 to remove the solder 3 'not covered by the strip mask 6 (FIG. 2D).

Next, the substrate 1 from which the solder 3 'has been removed is put in a gold plating layer, and the circuit pattern 2' is plated with gold to form gold 5 (FIG. 1e). Thus, the gold 5 is formed only on the surface of the circuit pattern 2 '. Next, the strip mask 6 can be easily peeled off by peeling it off from the rubber-based mask 6a (FIG. 2f). At the time of the peeling, a rubber-based mask 6 is applied to the portion of the solder 3.
If a remains, the surface of the solder 3 is cleaned by removing it with a solvent, so that a circuit pattern 2 'having a surface formed only of gold 5 and a circuit pattern 2 formed of only the solder 3 are produced. it can.

In the above embodiment, the solder and gold are formed separately on the surface of the circuit pattern. However, the metal formed on the surface is not limited to the above-mentioned materials. Of course, it can be applied to the case of a different kind of metal such as solder, gold, silver, nickel and the like.

[0017]

As described above, according to the present invention, after a portion of the circuit pattern where the solder is left is covered with a solder resist or a strip mask, the solder where the solder is exposed is removed, and then the solder is removed. A different metal such as gold is formed on the surface of the formed circuit pattern, and the solder resist on the circuit pattern on which the solder is formed is etched by laser light to expose the solder, or the strip mask is removed. It is possible to prevent the diffusion of dissimilar metals and to expose only the respective metal on the surface of each circuit pattern. Therefore, it is possible to prevent the deterioration in strength due to the diffusion and to provide the circuit pattern at a low cost because the manufacturing is simple. This has the effect of, for example,

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a manufacturing process in a method for surface treating a circuit pattern on a printed wiring board according to the present invention.

FIG. 2 is an explanatory diagram showing a manufacturing process according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2, 2 'Circuit pattern 3, 3' Solder 4 Solder resist 4a Hole 5 Gold 6 Strip mask

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiaki Goto 6-9-9 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture Inside Eight Industry Co., Ltd. (72) Tatsumi Takahashi 6, Tsunashima-Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture 7-9-9 Inside Eight Industry Co., Ltd.

Claims (2)

[Claims] 1. A method for forming another dissimilar metal such as solder and gold on a circuit pattern requiring surface treatment with another metal on a printed wiring board having a circuit pattern and a solder resist formed on a substrate, A step of forming solder on a circuit pattern requiring processing, a step of forming a solder resist on the solder resist except for a circuit pattern forming another dissimilar metal such as gold, and a step of forming a solder resist. Removing the solder of the circuit pattern, forming a dissimilar metal such as gold on the surface of the circuit pattern from which the solder has been removed by plating or the like; and soldering the solder resist on the circuit pattern on which the solder is formed. Etching the surface of the printed circuit board with a laser beam. 2. A method of forming another dissimilar metal such as solder and gold on a circuit pattern requiring surface treatment with another metal on a printed wiring board having a circuit pattern and a solder resist formed on a substrate. A step of forming solder on a circuit pattern requiring processing, and a step of printing a strip mask having an effect of preventing corrosion of solder at the time of plating the different metal except for a circuit pattern forming another different metal such as gold. Removing the solder of the circuit pattern that is not covered by the strip mask; forming a dissimilar metal such as gold on the surface of the circuit pattern from which the solder has been removed by plating or the like; Removing the strip mask formed on the printed circuit board.