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Stencil Printing of Solder Paste

IP.com Disclosure Number: IPCOM000116107D
Original Publication Date: 1995-Aug-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Britton, K: AUTHOR

Abstract

Solder paste is typically printed through a stencil using a roller squeegee in order to apply solder selectively to parts of a circuit substrate. Problems can however arise where the substrate has a 3-D configuration, due for example to certain features of the circuit being raised above others. In particular, intimate contact between screen and squeegee can be broken by such features, restricting the range of substrates that can be effectively processed.

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Stencil Printing of Solder Paste

      Solder paste is typically printed through a stencil using a
roller squeegee in order to apply solder selectively to parts of a
circuit substrate.  Problems can however arise where the substrate
has a 3-D configuration, due for example to certain features of the
circuit being raised above others.  In particular, intimate contact
between screen and squeegee can be broken by such features,
restricting the range of substrates that can be effectively
processed.

      The method disclosed here allows a larger range of 3-D
substrates to be printed with a more robust design, with the added
benefit of ensuring solder paste remains "in front" of the printing
squeegee, thus reducing operating cost (smaller volume of paste
required) and eliminating operator intervention (no need to manually
move solder paste on stencil).

Method
  o  Modify stencil 'artwork' to allow large opening in stencil to
      correspond to "3-D" areas of circuit/substrate (i.e., area of
      circuit which is raised away from required printing area).
  o  Secondly, design the corresponding metal 'template' with
      apertures/pockets corresponding to '3-D' area of substrate.
      Thickness dependant on 3-D area.
  o  Half etch or laser ablate 'gutters' on both stencil and template
      mating surfaces.
  o  Attach stencil and template using suitable chemically resistant
      adhesive so that impervious adhesive fillet fil...