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 FAQ's

  . COMPONENTS (8 questions)
  . HAND SOLDERING AND DE-SOLDERING (3 questions)
  . INSPECTION (3 questions)
  . PRINTED BOARD DESIGN (3 questions)
  . PRINTED CIRCUIT BOARDS (6 questions)
  . REFLOW SOLDERING (5 questions)
  . REWORK (1 questions)
  . SCREEN PRINTING (2 questions)
  . WAVE SOLDERING (4 questions)
  . X-RAY INSPECTION (1 questions)





SCREEN PRINTING

1 . I have changed my solder paste to a finer particle size due to my fine pitch requirements. I now have problems with solder balls which I did not originally have.
2 . My production department wants to use different PCB aperture size for production of stencils for lead-free solder paste. Is this normal, it means having another set of design rules.

 

I have changed my solder paste to a finer particle size due to my fine pitch requirements. I now have problems with solder balls which I did not originally have.
Just remember that when you reduce the size of solder particles in a paste for fine pitch printing you are increasing the metal surface area. In combination with a low residue paste and lead-free reflow it may be just too much for the paste activators. Try running some comparisons of you new and old paste using your existing reflow settings. Also type 3 powder will still work for the majority of applications.

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My production department wants to use different PCB aperture size for production of stencils for lead-free solder paste. Is this normal, it means having another set of design rules.
This is becoming common practice in the industry, but I would suggest that you talk to your companies stencil supplier. Most stencil manufacturers take, and prefer design data, so they can modify the data for you. Lead-free solder does not wet or flow as well hence covering more of the pads can improve the join appearance particularly on different surface finishes like gold, silver, copper and tin.

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