JPH01290291A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To obtain a printed wiring board whose adjoining patterns and so forth are completely covered by a method wherein the printed wiring board to which first solder resist ink is applied is mechanically polished to make the surface smooth and then second solder resist ink is applied. CONSTITUTION:The surface of a board 2 to which solder resist ink 4 is applied is mechanically polished to have the surfaces of lands 2a, foot prints 2b, patterns 2c and the solder resist ink 4 uniformly on the same smooth level. Therefore, overlaps of the solder resist ink 4 on the lands 2a and the foot prints 2b are eliminated and the top surfaces of the patterns 2c which is to be covered with ink are exposed. With this constitution, if second solder resist ink is applied after the polishing, the exposed patterns are completely covered.

Description

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

[Conventional technology]

FIG. 3 is a sectional view showing a conventional process for applying a solder resist to a printed wiring board using a screen printing method.

Before explaining the process, we will explain the components in Figure 3.
1 is a screen plate, 1a is its opening, and 1b is a clearance part. 4 is a solder resist ink, which is applied onto the substrate 2 through the opening 1a. Clearance part 1
b is a portion provided in alignment with a portion of the substrate 2 to which the solder resist ink 4 is not applied, such as the land 2a, the footprint 2b, and the through hole 2d. This clearance portion 1b functions to prevent the solder resist ink 4 from being applied onto the substrate 2 through the plate. 2C
is a pattern, and 3 is a squeegee.

Solder resist ink is applied in the following steps. That is, as shown in FIG. 3(a), the screen plate l is placed on the substrate 2.
Solder resist ink 4 placed on top and printed on the plate
When spread out with the squeegee 3 moving in the direction of the arrow,
The same ink 4 passes through the opening 1a into the pattern 2c of the substrate 2.
It is extruded and applied to other areas. FIG. 3(b) shows the state after the solder resist ink 4 has been applied, and the lands 2a, footprints 2b, etc. are not covered with the solder resist ink 4, and the pattern 2c is covered with the solder resist ink 4. completely covered.

In this manner, when the solder resist ink 4 is applied to the substrate 2, the exposed lands 2a, through holes 2d, and footprints 2b are coated with solder in a secondary process. This solder serves as surface protection and preliminary solder until parts are mounted.

(Problems to be Solved by the Invention) As described above, since the conventional solder resist ink 4 is applied onto the substrate 2 through the screen plate 1, the expansion and contraction of the screen plate l and the gap between the screen plate 1 and the substrate 2 are caused. Due to misalignment between the two due to the gap, misalignment between the screen plate l and the substrate 2, and the flow of fluid ink, as shown in FIG. ), pattern 2c was often exposed (indicated by reference numeral 7).

When such a phenomenon occurs, preliminary solder during component mounting becomes insufficient. Further, in the footprint 2b, the area in which soldering can be performed is particularly reduced, making it impossible to perform highly reliable soldering. Furthermore, if adjacent patterns 2C, lands 2a, etc. are exposed to each other, solder bridges are likely to occur between them during component mounting.

This invention was made to solve the above-mentioned problems, and when applying solder resist to a printed circuit board, there is a risk that solder resist ink may cover lands or footprints, or that patterns may be exposed. The purpose of the present invention is to obtain a method for manufacturing a printed wiring board that is free of .

[Means to solve the problem]

In the method for manufacturing a printed wiring board according to the present invention, after applying the first solder resist ink to the printed wiring board, the surface is mechanically polished to make it smooth, and then the printed wiring board is coated on the smoothed printed wiring board. This method is characterized by applying a second solder resist ink.

[Effect]

In this invention, after the first solder resist ink is applied to the printed circuit board, the surface is mechanically polished to make it smooth, thereby removing the solder resist ink covering the footprints and runts. can do. Furthermore, since the solder resist ink is applied twice after polishing, the exposed pattern H1 is completely covered.

〔Example〕

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

In the figure, the same reference numerals as in FIG. 3 indicate the same or corresponding parts.

First, for the first application of the solder resist ink 4, a screen plate 8 with a clearance amount f (?&description) of zero (absence) is used. That is, land 2a and footprint 2b
Printing is carried out using a screen plate 8 having a clearance portion 8b having the same shape as . In addition, 8a is an open "1 part.

FIG. 1(b) shows a state in which one coating 1ji has been completed. Since the clearance portion 8b has the same shape as the land 2a or the footprint 2b, the solder resist ink 4 is sufficiently applied between the land 2a and the pattern 2c and between the pattern 2C and the footprint 2b,
No exposure of C can be seen at all. However, in this case, the flowed ink 4 or the blurred ink 4 adheres to the land 2a and the footprint 2b.

Next, the surface of the substrate 2 coated with the solder resist ink 4 is mechanically polished to about #320.
), the surfaces of the land 2a, footprint 2b, pattern 2c, and solder resist ink 4 are made uniformly smooth and flat.

By this operation, the fogging of the solder resist ink 4 on the land 2a and the footprint 2b shown in FIG. 1(b) is removed. The upper surface of pattern 2C, which should be covered with ink, is then exposed.

Next, in FIG. 1(d), the solder resist ink 4 is applied twice [1], but as for the screen plate 9 used twice 11, the dimension g of the clearance part 9b is the same as that on the corresponding substrate 2. The dimension obtained by adding the relief amount f on both sides to the dimension e of the land 2a and footprint 2b (g=e+2
Use f). When the runt 2a is circular, the diameter of the clearance portion (φg) is the sum of the diameter of the land (φe) and the clearance m (2f ). In addition,
9a is an opening. In this example, the escape lif is 0.
．． I use something about 15mm.

In FIG. 1(e), 10 indicates the solder resist ink 4 applied for the second time, and the exposed pattern 2c in FIG. 1(c) is completely covered. At this time, since the surface of the substrate 2 is completely smooth as shown in FIG. 1(C), the second printing can be performed with high precision without being affected by the unevenness of the surface of the substrate 2.

The above embodiment is an example in which solder resist ink is applied to a high-density printed wiring board, but even in this case, the first
As shown in Figure (C), since the surface of the substrate 2 is completely smooth during the second printing, a sufficient amount of solder resist ink 4 can be uniformly applied to the edge portions of the pattern 2c and on the pattern 2c.

In the conventional solder resist ink 4, as shown in Fig. 2, there is a difference in ink Jγ at the edge part of the pattern 2C and the upper part of the pattern 2C, and when the pattern 2C is wide, the ink is not absorbed in the upper part due to the influence of the edge. Variations were seen in J'X. Variations in the thickness of the solder resist ink 4 appear as variations in insulation resistance between adjacent patterns and non-uniformity in electromagnetic properties. Affects characteristics.

However, as in this invention, solder resist ink 4
By uniformly applying the solder resist ink 4, problems caused by variations in the thickness of the solder resist ink 4 can be eliminated.

(Effects of the Invention) As described above, according to the present invention, the printed wiring board to which the first solder resist ink has been applied is smoothed by mechanical polishing, and then the second solder resist ink is applied. It is possible to obtain a printed wiring board in which adjacent patterns, etc. are completely covered with solder resist ink without covering lands, footprints, etc. with solder resist ink.

[Brief explanation of the drawing]

FIGS. 1(a) to (e) are cross-sectional views showing the solder resist coating process according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the solder resist ink coating process on a pattern using a conventional solder resist ink coating method. 3(a) and 3(b) are sectional views showing the conventional solder resist ink coating process, and FIG. 4 shows defects caused by the conventional solder resist ink coating method. FIG. 2 is the board, 2a is the land, 2b is the footprint, 2C
2d is a pattern, 2d is a through hole, 4 is a solder resist ink, 8 and 9 are screen plates, 8a and 9a are openings, 8b and 9b are clearance parts, and 10 is the solder resist ink applied for the second time. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] When applying solder resist to a printed wiring board, after applying the first solder resist to the printed wiring board, the surface is mechanically polished to make it smooth, and then a second coat of solder resist is applied on the smoothed printed wiring board. A method for manufacturing a printed wiring board, which comprises applying a solder resist.