Parameters for Screen Printing

Open Doctor Blade Systems


Today, standard open doctor blade systems are used to apply solder paste. The picture shows a screen printing machine with corresponding doctor blade, which pushes a solder paste roll in front of it and over the template, filling the corresponding SMD surface pads and the plated-through THR drill holes with solder paste.



Screen Printing Parameters


By regulating the doctor blade angle and doctor blade speed parameters, sufficient pressure is applied to the solder paste to fill (push the paste through) the THR drill holes. SMD fine pitch structures are not affected in any way. The additional solder paste requirement of the THR components does not adversely affect the fine structure. The amount of solder paste required depends on the type of screen printer used.



Screen Printing Function

Example of pushing a certain amount of solder paste into the THR drill holes. By adjusting the doctor blade angle (depending on the system) while keeping the doctor blade speed constant, a smaller angle creates a higher filling pressure and thus an optimum THR filling ratio for the drill hole.


Closed Doctor Blade Systems


The picture shows a DEK screen printing machine with a closed doctor blade system (PROFLOW). DEK is Phoenix Contact's partner for screen printing processes. Together we develop essential parameters for THR screen printing.



Screen Printing Parameters

Closed doctor blade systems apply pressure to the solder paste directly in the paste cartridge. The amount of pushed-through paste required for the THR process can be adjusted by regulating the speed and the pressure applied to the paste. This means that at constant speed, increased cartridge pressure leads to higher filling ratios plus protruding solder paste. The key features of this method are that it can be set quickly and the results are easy to reproduce.


THR Screen Printing Results - Filling Ratio / Paste Volumes


An optimum THR screen printing result is achieved if:
  • Excess pressure is not applied to the solder paste. This is achieved by using an appropriate template cutout.
  • The drill hole is completely full.
  • The solder paste protrudes by 1 to 1.5 mm (0.039 to 0.059 in.).



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