JPS62198194A - Manufacture of thick film printed board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a method for manufacturing a thick film printed circuit board for thick film ICs and the like.

[Prior art and its problems]

As is well known, in order to manufacture this type of thick film printed circuit board, first a thick film conductor pattern is printed on the board in a predetermined pattern using screen printing and then dried. After baking, an overcoat material is printed on the substrate so as to cover and protect the conductor pattern, leaving openings for mounting specified chip components, leads, etc. on the thick film conductor pattern. On the other hand, in this case, in order to increase the mounting density of the printed circuit board, strict tolerances are prescribed for the dimensional accuracy of the opening. By the way, thick film paste is used to print thick films using the screen printing method, but in this case, the biggest problem with the dimensional accuracy of the openings is sag of the paste material during the overcoat printing process. . To explain this regarding the conventional example shown in FIG.
After printing the thick film conductor pattern 2 on top, drying and baking it, the prescribed dimension A set on the conductor pattern 2 is then
The overcoat 4 is thickly printed using a paste material while the openings of the overcoat 4 are covered with the mask 3.During this printing, the overcoat 4 that passes through the mesh of the printing screen sag occurs. The pattern shape of the overcode 4 is slightly distorted, and the overcode 4 exceeds the boundary of the opening designated on the conductive pattern 2 and sags into the opening area. As a result, the area of the opening is narrowed, making it difficult to ensure the specified dimension A. Note that dimension B in the figure is the width of intrusion into the opening area due to sagging of the overcoat 4. As a countermeasure for this, conventionally, the amount of sagging that occurs when printing the overcoat 4 is estimated, and the dimensions of the mask 3 are set in advance to be smaller than the specified dimensions of the opening, taking this amount of sag into account.
A method has been adopted in which by selecting a large circumference, the sag of the overcoat is compensated for and an opening having the prescribed dimension A is formed and secured. However, the sag of the overcoat on the lever changes depending on conditions such as the printing process and variations in the viscosity of the paste material, so even if the above method is adopted, the opening may expand beyond the specified size or the opening may be Problems such as variations in dimensions remain.

[Purpose of the invention]

The present invention has been made in view of the above points, and is a thick film printing method that solves the problems in the prior art described above and makes it possible to form openings of specified dimensions with high accuracy at specified locations on a conductor pattern. The purpose of the present invention is to provide a method for manufacturing a substrate.

[Key points of the invention]

In order to achieve the above object, the present invention prints a thick film conductor pattern on a substrate, and furthermore, coats a layer of overcoat in a designated opening area on the conductor pattern with a thickness of overcoat according to the prescribed dimensions of the opening. After overlapping and double printing thick film conductors with a thickness corresponding to the thickness of the upper layer, the openings are masked and an overcoat is printed. This prevents the overcoat from sagging at the opening and ensures an opening with high dimensional accuracy that meets the specified dimensions.

[Embodiments of the invention]

1 and 2 show different embodiments of the present invention, and first, a method for manufacturing a thick film printed circuit board according to the present invention will be explained with reference to FIGS. 1a) to 1C. That is, in the first step, as shown in FIG. ta1, a predetermined thick film conductor pattern 2 is printed on a substrate 1, and then the conductor pattern 2 is dried. Next, as shown in the figure, overlay the upper layer thick film conductor indicated by reference numeral 5 on top of the conductor pattern 2 while masking the specified opening part on the conductor pattern 2 according to the specified dimension A. to print twice. Further, the layer thickness of the thick film conductor 5 is selected to be equal to or slightly thicker than the layer thickness of the overcoat to be printed in the next step. Note that in the printing process of the upper layer thick film conductor 5, paste sag naturally occurs in the thick film conductor 5, causing the shape of the pattern to be slightly distorted, but this sagging occurs outward from the opening area. I will do it. Next, as shown in Fig. Te1, an overcoat 4 is printed with the opening portion covered with a mask 3. As a result, the overcoat 4 covers the sagging portions generated around the conductor pattern 2 and the upper thick film conductor 5 printed in the previous process. Moreover, in this case, the region of the opening that has been I-certified is already filled with the upper layer thick film conductor 5, and there is a step corresponding to the thickness of the thick film conductor 5 between it and the conductor pattern 2. In addition, as shown in FIG. 3, the opening is prevented from sagging of the overcoat 4 that enters the opening area, thus forming an opening with high dimensional accuracy according to the specified dimension A. You will be able to do that. Figure 2 (al, (bl) shows another embodiment;
The difference from the illustrated embodiment is that the upper thick film conductor 5 is crossed over the conductor pattern 2 and printed twice.゛By adopting this method, even if the dimensional accuracy of the conductor pattern 2, especially the end dimension of the opening, is somewhat rough, it is possible to obtain an advantage of being able to accurately secure an opening with the specified dimensions at a specified location. . [Effects of the Invention] As described above, according to the present invention, a thick film conductor pattern is printed on a substrate, and furthermore, a thick film conductor pattern is printed on the conductor pattern at a designated opening portion according to the prescribed dimensions of the opening. After overlapping and double-printing a thick film conductor with a thickness corresponding to the layer thickness of the overcoat, the openings are masked and the overcoat is printed, thereby preventing intrusion into the opening area during the overcoat printing process. It is possible to prevent the paste material from sagging and ensure the formation of an opening with high dimensional accuracy.

[Brief explanation of drawings]

Figure 1 (al~(C1) is a manufacturing process diagram of a thick film printed circuit board according to an embodiment of the present invention, and Figures 2 (4) and (b) are partial cross sections of a thick film printed circuit board of an embodiment different from that in Figure 1. Figure, and (8
FIG. 1 is a plan view of a pattern of thick film conductors printed in upper and lower layers, and FIG. 3 is an explanatory diagram of a conventional method of manufacturing a thick film printed circuit board. In each figure, l: substrate, 2: conductor pattern, 3: mask, 4: Figure 3

Claims (1)

[Claims] A method for manufacturing a printed circuit board, in which a thick film conductor pattern and an overcoat are sequentially printed on a board, and openings not covered with the overcoat are formed at specified locations on the conductor pattern, the method comprising: printing a thick film conductor pattern on the board; After printing a thick film conductor with a thickness corresponding to the layer thickness of the overcoat in accordance with the specified dimensions of the opening at the designated opening part on the conductor pattern and double printing. . A method for manufacturing a thick film printed substrate, comprising printing an overcoat while masking the opening.