JPH02267994A - Printed wiring board - Google Patents

Abstract

PURPOSE:To prevent the deterioration of solderability of a printed board for high density surface mounting by performing solder plating after forming a copper through hole. CONSTITUTION:After forming a copper through hole 7, a plating resist 8 for soldering is formed and then, solder plating 6 is performed. After peeling off the plating resist 8, a resist pattern 9 for etching is formed. Etching is performed and a conductor is formed by peeling off the resist pattern 9. After that, as to a manufacturing process, coating of a solder resist and the like step are performed in the same manner as the ordinary way of manufacture. The deterioration of soldering properties is thus prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure and manufacturing method of a printed wiring board.

[Conventional technology]

As described in the June 1985 Special Issue of Electronic Technology, many high-density printed wiring boards use small-diameter through-holes, and the surface plating is performed using the solder plating method rather than the manufacturing method. has been done. In addition, the solder plated surface has problems with adhesion to the solder resist, so
This solder plating is often peeled off to expose the copper surface, and then a solder resist is applied.

[Problem to be solved by the invention]

A method called solder stripping has been widely used for surface treatment of surface mounting patterns and small-diameter through holes used in high-density printed wiring boards (hereinafter referred to as printed circuit boards). As a result, processing liquid remains in the small diameter through-hole, making it more likely to corrode, and soldering to one component increases the number of repetitions, making the copper surface more susceptible to deterioration due to heat. . There is also a method of applying solder to the copper surface by adding a method called a solder coating method, but it is complicated and there is also the problem that solder is difficult to adhere to small-diameter through holes.

An object of the present invention is to provide a structure and manufacturing method for a printed circuit board that has excellent rust prevention and solderability for desired conductor parts such as pads for surface mounting and small-diameter through holes.

[Means to solve the problem]

In order to achieve this objective, the surface of the conductor was structured to be coated with solder as needed. Moreover, the surface of the conductor that does not require soldering is a copper surface. In addition, the manufacturing method of printed circuit boards that includes applying solder is to perform through-hole plating using the conventional method, then pattern solder plating to the areas where solder should be applied, including small-diameter through holes, etc. A conductor pattern is formed using a photoresist as an etching resist, and thereafter, a conventional manufacturing method is appropriately used to apply a solder resist and final finish the conductor pattern.

[Effect]

Since the small-diameter through-hole has a small hole diameter, it is difficult to clean the processing liquid. Especially when applying solder resist? When the solder resist is applied to the small-diameter through-hole in R, the cleaning performance is significantly deteriorated. In some cases, it is impossible to prevent solder resist from getting into small-diameter through-holes, so a conductor surface that is less susceptible to cleaning is required. Copper is susceptible to this effect, while solder is less so.

Furthermore, in surface mount assembly, soldering is repeated, so if the surface is a copper surface, the solderability deteriorates due to the influence of heat, but if the surface is a solder surface, the deterioration is less.

The solder surface has poor adhesion to the solder resist, which tends to deteriorate further when heat is applied, and the surface of the conductor pattern to which the solder resist is applied is superior to the copper surface.

Copper surfaces and solder surfaces each have their advantages and disadvantages, and this poses a major problem, especially when selecting the surface treatment for high-density printed circuit boards for surface mounting.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

Figure 2 shows the structure of a conventional printed circuit board, with Q
A through hole 1 with a diameter of, for example, φ0.9, and a through hole 2 with a small diameter, for example, φ0.3 are provided, and conductor patterns such as signal lines 3 and pads 4 for surface mounting are arranged on both sides of the hole 1. Solder resist 5 on the part
is coated. In the case of FIG. 1, the surfaces of the conductive patterns 3.4 and the through holes 1 and 2 are roughened copper surfaces.

FIG. 1 shows an embodiment of the invention. The surfaces of the normal through-hole 1, the small-diameter through-hole 2, the signal pattern 3, and the surface mounting pad 4 can be selected as a copper surface or a solder surface 6.

The solder resist 5 is applied in an appropriate shape.

Although the copper surface is shown in FIG. 2, the solder surface may also be used.

Further, in FIG. 1, the normal through hole 1 is formed on a copper surface, but it may be formed on a solder surface if necessary. Similarly, the surface mounting pad represents a solder surface, but it goes without saying that it may also be combined with a copper surface.

3 to 6 show examples of the present invention, in which, as shown in FIG. 3, after forming a copper through hole 7, a plating resist 8 for applying solder is formed, and as shown in FIG. 4, solder plating is performed. 6
After removing the plating resist 8, a resist pattern 9 for etching is formed as shown in FIG. 5, etching is performed as shown in FIG. 6, and the resist pattern 9 is removed to form a conductor. In the subsequent manufacturing method, solder resist coating and the like are performed in accordance with conventional methods.

〔Effect of the invention〕

As described above, the present invention has the effect that the solderability of printed boards for high-density surface mounting is less likely to deteriorate, and corrosion caused by residual foreign matter in small-diameter through holes can be easily prevented. In addition, void prevention during etching of small-diameter through-holes can be achieved by a double layer of solder plating and etching resist, thereby suppressing the occurrence of defects. In addition, pads for surface mounting can be selected from a range of uniform and plating thickness for solder plating, and when soldering,
This solder plating can be effectively used when a uniform amount of solder is required.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a pudding 1-board according to an embodiment of the present invention;
Figure 2 is a cross-sectional view of the structure of a conventional printed board, and Figures 3-
FIG. 6 is a cross-sectional view of one embodiment of the present invention during the printed board manufacturing process. 1... Normal through hole, 2... Small diameter through hole, 3... A number line, 4... Pad for surface mounting. 5...Solder resist, 6...Solder plating. District 7

Claims (1)

[Claims] 1. In a printed wiring board that has a desired conductor pattern and through holes on both sides of an insulating plate, the surface of the conductor pattern and through hole is treated with solder on the surface of the hole diameter of the desired small diameter through hole, and the conductor pattern and through hole are surface treated with solder. 1. A printed wiring board characterized in that the surfaces of the through holes except for small-diameter through holes are subjected to a copper surface treatment, and the conductor pattern and the through holes are subjected to a normal surface treatment of a solder resist.