JPS592395A - Method of forming thick film circuit - 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] The present invention relates to a method of forming.

Conventional technology Thick film circuits such as thick film hybrid ICs have conductors and resistors.

Paste for insulators, etc., using the screen printing method.

They have been formed by laminating each on an insulating substrate such as alumina ceramic. In the thick film circuit formed in this way, the printed film thickness tends to change depending on the printing condition, and the resistance value and capacitance may change. Therefore, it is necessary to control the film thickness to be constant. For example, regarding resistors.

If the film thickness is larger than the reference value, it will be smaller than the predetermined resistance value, so various trimming techniques can be used to make it a predetermined circuit constant. However, if the film thickness is too small than the reference value, the resistance value will be greater than the predetermined value, making trimming impossible and resulting in a defect. For this reason, the pattern is designed by printing so that the film thickness is larger than the reference value in advance, but by setting an area ratio that takes into account the variation in the actual i thickness with respect to the reference film thickness.

In addition, since the printing film thickness depends on various conditions during printing, squeegee speed, printing pressure, distance between the screen and the substrate (screen nicestance), paste viscosity, etc., perform a trial print when setting the screen and check the film thickness. The thickness is measured using a stylus type or optical type film thickness meter, and after adjusting and setting each condition, the product is printed.

Here, if we explain the conventional film thickness formation using drawings, the first
As shown in Figure (A), if the substrate 1 is very flat and ideal, the thick film 2 formed on it will always have a constant and controlled thickness as long as there is no change in the viscosity of the paste. It is formed.

However, in reality, alumina ceramic substrates and the like have warps, waviness, and thickness tolerances.

Therefore, as shown in Figure 1 (b), the printed state of the actual product is such that the thick film printed on the substrate 3, which has undulations, is thin as shown in 4, and thick as shown in 5. is normal. When fired in this state.

In the case of a resistor, the thick film 5 is smaller than the design constant, so
Trimming is possible, but since the thick film 4 becomes larger than the design constant, trimming cannot be performed, resulting in a defect. To prevent this, either print the film to be much thicker than the standard film thickness, or print at the risk of producing a defective product. However, when printing thickly, not only does the amount of paste used increase, but also the trimming time increases, resulting in higher costs; in the latter case, the yield decreases, which also increases costs. .

OBJECTS OF THE INVENTION An object of the present invention is to eliminate variations in film thickness within the same substrate due to the substrates described above and variations in film thickness within the same production lot, to efficiently form thick film circuits, and to improve production yield. It is an object of the present invention to provide a method for forming a thick film circuit that improves the performance and further reduces costs.

Summary of the Invention Therefore, in the present invention, a thick film having a predetermined area and thickness is formed by printing a paste of a conductor, a resistor, etc. on a film. Then, the film surface on which the thick paste film is formed is brought into contact with a metal plate at a predetermined position on an insulating substrate such as alumina ceramic to transfer the thick film.

After being transferred, the insulating substrate is fired to form a thick film circuit.

Embodiment of the Invention As shown in FIG. 2(a), a thick paste film 7 of a conductor, resistor, insulator, etc. having a predetermined area is formed on a film 6 of polyester or the like by screen printing or the like.

Then, from the back side of this film 6, as shown in FIG. 2 (b), a transfer jig 8 such as a roller is used.

The paste thick film 10 is brought into contact with and transferred to predetermined positions such as between the conductors 11 on the substrate 3. In this case film 6
The thickness tolerance is as small as ±5 inches, and since it is thin, it has sufficient ability to follow the table condition of the printing press. Therefore, by controlling the flatness of the table, a thick film 9 having a uniform thickness can be obtained. The substrate 3 is then fired in a conventional manner to form a thick film circuit.

As for the transfer method, there may be a method of sequentially selecting and performing the transfer as shown in FIG. 2(b), or a method of transferring a plurality of layers onto the substrate 3 at the same time, but either method may be used.

For example, the plate thickness is 0635±0.95m and the warpage tolerance is 2
5 length per p maximum 0. l Standardized by TGM 9
5 will be considered when applied on a 6% alumina ceramic substrate 3. 100 thick film circuits were manufactured by transferring a paste resistor previously formed by screen printing onto a 50 μm thick polyester film 6, and 100 thick film circuits were printed directly onto a conventional alumina ceramic substrate. When we measured the resistance value, we found that it was only 1% compared to 30% for thick film circuits using conventional methods.
In the thick film circuit according to the present invention, variation could be suppressed within a very small range of 5%.

As described in detail, according to the present invention, in the process of forming a thick film printed circuit, it is possible to reduce the film thickness due to thickness tolerances, waviness, etc. of the insulating substrate itself, such as alumina ceramic, which was previously impossible. It is possible to eliminate variations in Therefore, it is very effective to realize an improvement in yield, eliminate waste of materials and man-hours, and realize cost reduction and performance improvement. Additionally, if a standardized pattern shape is formed on the film in advance, the thick film circuit formation process can be simplified.
Mass production becomes effective.

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[Brief explanation of the drawing]

Figure 1 (a) is a cross-sectional view showing the ideal thick film formation state using the conventional printing method, Figure 2 (b) is a cross-sectional view showing the actual thick film formation state using the conventional printing method, and Figure 2 (a) 2 is a cross-sectional view showing the state of a thick film formed on the film of the present invention, and FIG. be. The symbols used in the drawings are as follows. 1...Ideal insulating substrate, 2...Ideal thick film, 3...Actual insulating substrate, 4...
...Thin thick film, 5...Thick thick film, 6...
・Film, 7... Paste thick film on film, 8... Transfer jig, 9... Transferred paste thick film, 10... Transfer Thick film of paste inside. 11... Lower thick film of conductor, etc. 7- Figure/Fig.

Claims (1)

[Claims] A thick film with a predetermined area and thickness is printed on a film using a paste of a conductor, a resistor, an insulator, etc., and the thick film of the film is formed on a predetermined position on an insulating substrate such as alumina ceramic. A method for forming a thick film circuit, characterized in that the thick film circuit is formed by transferring the thick film by bringing the thick film into contact with the insulating substrate, and completely baking the insulating substrate after the transfer.