The role of screen printing in PCB manufacture

With the continuous growth of screen printing skills, the deployment of new screen printing materials, screen printing processes and testing equipment for PCB industryhas been perfected, so that the screen printing skills before appropriate can roughly adapt to the high density PCB production. 

The application of screen printing in PCB manufacturing is important in the following three aspects:

a. Application of PCB surface solder resistance layer;

b. PCB graphic transfer process and corrosion resistant coating application;

c. The application of PCB appearance marking.

Due to the realization of the former two application on skills is difficult, this paper will be targeted to introduce, at the same time for screen printing material of PCB technology DiYaoXing introduction.

A, screen printing material

1. Silk screen

Screen is the most important component of the screen printing plate, this is because it is the key to control the activity of ink and printing thickness, at the same time it determines the durability of the screen and quality switch manufacturing skills have been widely used. In addition, screen and screen plate sensitive material has excellent joint is also an important factor in the production of high quality, high precision screen printing plate. In order to guarantee the good combination of screen and photosensitive material, the traditional practice is to hold the new screen coarsening and degreasing disposal penalty, such as allowing to package network version quality and extend the life of the screen.

2. Plate sensitive material

Plate sensitive material commonly used diazo sensitive agent, sensitive film and so on. Diazo emulsion is widely accepted in screen printing. Photosensitive film has the characteristics of symmetrical and controllable film thickness, high image resolution, high clarity, wear resistance, strong adhesion with screen, etc., and has been widely used in the character printing of printed board.

3. Network frame

The material of the frame and the shape of the section are very important, compared with a certain size of the frame, if the strength of the frame is not enough, it can not guarantee the equality of tension. Now it is common to use high tension aluminum mesh frame.

Ii. Conclusion

With the growth of screen printing skills, screen printing skills occupy more and more important positions in the printed circuit manufacturing industry, its application, not only improved the production of printed circuit obedience, low production cost of printed circuit, but also improved the quality of printed circuit board processing. On the other hand, due to the research, development and application of screen printing materials, especially the development of functional ink, so that the application of screen printing more diversified, and has been expanded, such as film switch manufacturing skills in silver printing; SMT manufacturing skills in solder paste printing and template manufacturing;

 PCB strippable ink application.

The problem solving method of PCB board on - line dividing machine

On line PCB splitter integrated circuits, due to the fast speed, no other measures of the edge, tracking length must be shortened in order to maintain signal integrity. Any long signal path of an in-line splicer PCB can be regarded as a transmission line, and if the line propagation delay time is much shorter than the rise time signal, then the rise of the signal generation reflects that Yahweh must be flooded. No longer will overshoot, recoil and ring, most existing MOS circuits, due to the rise time line propagation delay time ratio is greater, so alignment can grow in meters without signal distortion.

The problem solving method of PCB board on - line dividing machine

On-line splitters have two ways to make high-speed circuits work on a relatively long line without serious waveform distortion.

TTL drops along the fast Schottky diode clamp method. Such excesses are clamped in more than one diode below the ground potential level, thus reducing the amplitude of the rear recoil-back, slowing the rise of the edge over allows for relatively high output impedance attenuation in the H level state of the circuit. In addition, since the level H state exemption is large, so the problem is not very prominent in the recoil of the HCT series equipment, using a Schottky diode clamp and series resistor termination method in combination with the improved effect will be more obvious.

Another method is commonly used: line impedance matching method. In this way, the control can reflect the signal integrity assurance. Strictly speaking, on-line splitters have a slower speed, traditional TTL edge and CMOS devices, and transmission lines are not very necessary. With a faster edge speed high emitter coupled logic device, transmission lines are not always needed. However, when using transmission lines, they must predict connection delays and control impedances reflected by dominance and oscillations.