Metal working – Method of mechanical manufacture – Electrical device making
Patent
1986-03-10
1988-01-26
Eley, Timothy V.
Metal working
Method of mechanical manufacture
Electrical device making
228 45, H05K 320
Patent
active
047209143
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to method and apparatus for forming a thick film circuit which is capable of being adapted for use in broadcasting radio receivers, television receivers, communication equipment, measuring control equipment, and so on, and to a method for forming a thick film circuit which is capable of accurately drawing a thin and wide line in a short time.
BACKGROUND OF THE INVENTION
A thick film circuit has been hitherto formed in accordance with the screen printing method for mass production, and it has also been attempted to form such a thick film circuit by means of the drawing method using a drawing nozzle. When beginning a manufacturing process, the screen printing method requires the design and manufacture of a screen for each thick film circuit, and therefore this method take a long time to complete. On the other hand, the drawing method does not require such screens and therefore a new circuit pattern can be made in a short time. This makes it possible to shorten the time period required for development of a new circuit pattern manufacturing process
A conventional drawing method is illustrated in FIG. 1, where a drawing nozzle 3 has a circular paste discharging hole 4 for discharging a thick film paste 1 and is relatively moved with respect to a substrate 2 to thereby apply the thick film paste 1 on a surface of the substrate 2 so as to form a desired circuit pattern. This drawing method is useful for drawing a narrow line. FIG. 2 is an illustration of an end portion of the drawing nozzle 3. Generally, the paste discharging hole 4 has a diameter of 100 to 300 .mu.m. FIG. 3 is an illustration of the cross-section of the paste drawn by the drawing nozzle 3 having a circular paste discharging hole, which cross-section is measured by a surface roughness measuring device after burning. As seen from FIG. 3, the configuration of the cross-section is a semicircle and the thickness of the center portion is greater than the edge portions. Therefore, in cases where a wide line is drawn by increasing the diameter of the nozzle, the thickness thereof increases, with accompanying disadvantages. Particularly, in a laser trimming process performed for adjusting the resistance value of a resistor paste after burning, the large thickness of the line causes difficulties during the trimming process. Even if the trimming is performed by increasing the output of the laser or in a slow manner, a micro-crack occurs in the resistor portion due to the high temperature required and therefore the resistance value varies with time, resulting in low reliability. Generally, the resistor paste is less than 12 .mu.m in film thickness after burning and is about 1.0 mm in width. Using the circular paste discharging hole and keeping the film thickness to less than 12 .mu.m, the maximum width of a line is only 150 .mu.m. In order to eliminate this problem a method has been hitherto employed in which a thin and wide line is formed by drawing a plurality of narrow lines close to each other. However, this method takes a long time, and the thickness of the connection portions becomes uneven and the resistance value becomes unstable, resulting in a deterioration in quality.
DISCLOSURE OF THE INVENTION
The present invention relates to a method for forming a thick film circuit by discharging the thick film paste from the paste discharging hole and drawing a desired shape on a substrate, wherein the drawing nozzle has a substantially wide paste discharging hole and is rotated about its axis so that the longitudinal direction of the paste discharging hole is maintained substantially kept at right angles to the direction that the drawing nozzle is moved with respect to the substrate. Since the drawing nozzle according to the present invention has a substantially wide paste discharging hole, a thin and wide pattern can be drawn by one stroke, or required, by several strokes. Furthermore, since the drawing nozzle is arranged to be freely rotated, the drawing can efficiently be made in optional directions by
REFERENCES:
patent: 4291642 (1981-09-01), Kolc
Kabeshita Akira
Kudou Shinichi
Maeda Yukio
Eley Timothy V.
Matsushita Electric - Industrial Co., Ltd.
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