2.5 Post-printing of Thick Film Circuits
Generally, a thick film printed circuit board is printed. Conductor printing is performed first, and resistance is repeatedly printed 2 to 3 times. According to circumstances, the glass coating may be appropriately cross-processed, and the following processing or processing may be performed after printing.
(1) Flattening process: After printing, prints are left for 5-7 minutes until the web disappears.
(2) Drying: Dry it at a temperature of about 100 °C.
(3) Firing: The firing is performed at a temperature of about 650 to 670C. This process is very important, so it is necessary to adjust the furnace temperature at any time to maintain the temperature suitable for slurry sintering.
(4) Adjustment: Adjusting the resistance value is generally performed by sandblasting the circuit board or adjusting the resistor body with a laser.
(5) Encapsulation: Protection of the manufactured internal components.
2.6 Thick Film Resistor Screen Printing Process
Thick film printing is similar to screen printing in general, except that thick film printing products are circuit elements such as thick film resistors and capacitors. Accuracy, electrical stability, and solderability of thick-film resistors are related to the quality of thick-film screen printing. There is a slight change in ink film thickness and the product cannot be used. Therefore, the uniformity of the film thickness of the thick film resistor will directly affect the product yield.
An ordinary thick film resistor is a cube with a thickness of about 20 μm. If the thickness is controlled, the ratio of length to width can be used to determine the resistance of the resistor. The aspect ratio of the thick film resistors is 10:1 to 1:10 maximum, and the resistance of the printing ink (resistance paste) with the same resistance value can only be varied within the range of 10 to 1/10. In order to obtain a resistance value outside this range, it is necessary to use a paste having a different resistance value. Thick film resistors, as shown in Figure 3.
2.7 Influence of Silk Screen Defects on Thick Film Circuits
In the production of thick-film printed circuits, the impact of screen printing defects on the quality of finished products is great. Table 1 shows the impact of screen printing defects on the quality of finished products.
3 Conclusion
At present, although the application of silk screen technology in our country is becoming more and more extensive, there is still a big gap compared with the advanced technological level in foreign countries. This article discusses in detail the whole process of screen printing technology for thick film integrated circuits. Of course, it is good. In addition to the technological factors, screen printing products have to take into account advanced machinery and equipment. I hope that this article will serve as a reference or reference for printers and strive to promote the development of China's screen printing industry.
Chen Zhongwu (Eleventh Institute of Electronics, Ministry of Information Industry)
