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Elements of solder paste printing process-Ⅱ Written by HC AUTOMATOIN / Read 74 times

A. Printing Speed of Solder Paste Screen Printer

1. Because the speed of scraper is inversely proportional to the viscosity of solder paste, the speed is slower when there is a narrow distance. If the speed is too fast, the time when the scraper passes through the opening of the stencil is relatively short, and the solder paste can not enter the opening adequately, which simply constitutes the printing defects such as inadequate solder paste forming or leak printing.

21.png2. There is a certain relationship between printing speed and scraper pressure. Decreasing speed is equivalent to increasing pressure. Appropriate reduction of pressure can improve printing speed.

3. The ambitious speed and pressure of the scraper should be to scrape the solder paste from the surface of the stencil.

B. Printing gap of SMT solder paste screen printer machine

Printing void is the distance between stecil and PCB, which is related to the amount of solder paste left on PCB after printing.

C. Separation Speed of Steel Mesh and PCB in Operation of Smt Solder Paste Printer

After solder paste printing, the instantaneous speed of steel mesh leaving PCB is separation speed, which is a parameter related to printing quality. It is the most important in close distance and high density printing. Advanced printing press, when its steel mesh is separated from the solder paste pattern, has one or more small staying processes, i.e. multi-stage demoulding, which can ensure the best printing forming.

When the separation speed is too high, the paste adhesion decreases and the cohesion between the paste and the pad is small, which causes some paste to adhere to the bottom of the steel mesh and the open wall, thus constituting printing defects such as under-printing and tin collapse. When the separation speed slows down, the solder paste has high viscosity and cohesion, which makes the solder paste easily detached from the open wall of the steel mesh, and the printing condition is good.

D. Cleaning Mode and Frequency of Solder Paste Screen Printer

Cleaning the bottom of the steel mesh is also an important factor to ensure the quality of printing. Cleaning mode and frequency should be confirmed according to solder paste, steel mesh material, thickness and hole size. (Set dry cleaning, wet cleaning, one-time reciprocating, scrubbing speed, etc.)