JPH0365032B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION The present invention relates to an improvement in a method for manufacturing a thick film multilayer circuit board. Background of the Technology The following is an explanation using a thermal head as an example. A thermal head has a large number of heat-generating low antibodies on a heat-resistant substrate, and prints on heat-sensitive recording paper by applying electrical pulses to the desired low-antibodies to generate heat. There are two types: thick-film type and thick-film type. Thin-film thermal heads have excellent printing quality but are expensive, while thick-film thermal heads have poor printing quality or are inexpensive. Therefore, a thermal head has been proposed that combines the two methods and provides excellent printing quality at a low cost. Prior Art and Problems FIG. 1 is a diagram for explaining a thermal head that combines a thin film type and a thick film type. This consists of a heat-resistant substrate 1 made of alumina or the like, and a thin film head part A consisting of a heat insulating glaze layer 2, a thin film low antibody 3, a thin film conductor 4, and a protective film 5, a first layer conductor 6, and dielectric layers 7, 2.
It is composed of a thick film multilayer circuit section B consisting of a layer conductor 8, a dielectric layer 9, a third layer conductor 10, and a dielectric layer 11, and the thin film conductor 4 and the thick film conductor 8 are connected at a section C. An IC driver 12 for driving the heat-generating low antibody is bonded with resin 13 onto the second layer conductor 8 of the thick film multilayer circuit, and wire bonded to the third layer conductor 10. In such a thermal head, the thick film conductor is conventionally patterned only by screen printing, but the minimum line width in this case is set to be 100 μm or more. Therefore, the dot density increases and the line width increases.
When the thickness is less than 100 μm, it becomes difficult to form using the screen printing method. To this end, it was believed that after forming a thick film conductor over the entire surface, it would be possible to make the pattern finer and more precise by using photolithography techniques, including photoresist coating, exposure, and etching. However, in reality, the surface roughness of the thick film conductor that is formed is large (approximately 2 to 5 μm), and as a result, the resist is not formed uniformly, and there are large variations during etching, making it virtually difficult to pattern with a thickness of 100 μm or less. . OBJECTS OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide a method for manufacturing a thick film multilayer circuit board in which thick film conductors can be patterned by photolithography. According to the present invention, this object is to provide a thick film multilayer circuit board in which a thick film conductor is formed on the entire surface of a heat-resistant substrate or a dielectric layer, and then a conductor pattern is formed using photolithography. Provided is a method for manufacturing a thick film circuit board, characterized in that, before the photolithography process, mechanical polishing is performed to flatten and reduce roughness on the surface of the thick film conductor. This is achieved by EXAMPLES OF THE INVENTION The present invention will now be described in detail with reference to examples. As sample No. 1, a copper thick film paste was printed on the entire surface of a 97% alumina substrate, and after drying, it was heated at 900℃ in _N2 gas.
A thick copper film layer of about 10 μm is formed by firing with
Sample No. 2 was prepared by forming a multilayer thick dielectric layer on the entire surface of a 97% alumina substrate, and then forming a copper thick film layer on top of it in the same manner as Sample No. 1, and printing these. Polishing was performed in this order using an oscillation polishing machine for plates using polishing rolls of #300 → #600 → #1000 → #2000, and the surface roughness before and after polishing was measured. The results were as shown in Table 1.

[Table] For these samples, the pattern width is 10, 20,
Using six types of test patterns of 40, 80, 160, and 320 μm (length 100 mm, gap equal to pattern width, number of patterns 100), patterning was performed using photolithography to shoot pattern defects and disconnections. Evaluation was based on points. Tables 2 and 3 show the results of evaluating 1000 pieces of each pattern. Table 2 shows sample No. 1 (patterned thick copper film layer on a 97% alumina substrate),
Table 3 shows the evaluation results of sample No. 2 (patterned thick copper film layer on a thick film dielectric layer). In the table*
The defective rate is high because the mark is shot and disconnected.
It is over 100%.

【table】

[Table] From Tables 2 and 3, it can be seen that the number of defects in samples No. 1 and No. 2 that were polished was reduced by about one to two orders of magnitude compared to those that were not co-polished. . Also
Although the pattern is as long as 100 mm (in reality, it is rare to extend it even 100 mm with high density), it is possible to use patterns with a pattern width of about 40 μm. In the example described above, the surface of the thick film conductor was polished using an oscillation polisher for printed circuit boards, but other polishing methods, such as spraying a solution of ceramic powder suspended in water, onto the conductor surface may also be used. Equivalent results can be obtained using the same device. Furthermore, it goes without saying that the thick film conductor is not limited to copper, and equivalent results can be obtained with thick film conductor materials such as gold, silver, silver-palladium, and the like. Effects of the Invention As described in detail above, the method for manufacturing a thick film multilayer circuit board of the present invention is to polish the surface of the thick film conductor to reduce the surface roughness, and then to increase the density of the thick film conductor using the photolithography method. This has a great effect in making it possible to create a pattern.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining a conventional thermal head. In the drawings, A indicates a thin film head section, and B indicates a thick film multilayer circuit section.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a thick film multilayer circuit board in which a thick film conductor layer is formed on the entire surface of a heat-resistant substrate or a dielectric layer, and then a conductor pattern is formed using photolithography. A method for manufacturing a thick film multilayer circuit board, characterized in that, before a lithography process, mechanical polishing is performed to flatten and reduce roughness on the surface of a thick film conductor.