by S. Manian Ramkumar Ph.D., Rita Mohanty Ph.D., CEMA, Chris Anglin, Toshitake Oda
The demand for product miniaturization, especially in the handheld device
area, continues to challenge board assembly industry. The desire to incorporate
more functionality while making the product smaller continues to push board
design to its limit. It is not uncommon to find boards with castle like components
right next to miniature components. This type of board poses special
challenge to the board assemblers as it requires wide range of paste volume
to satisfy both small and large components. One way to address the printing
challenge is to use creative stencil design to meet the solder paste requirement
for both large and small components. Example of stencil design includes step
stencil, dual printing, over size aperture, etc. Stencil printing process at its
most basic level involves pushing solder paste through a stencil (with various
size apertures) by a squeegee blade. As the squeegee blade and the stencil
are in constant contact with the paste during the printing process, their surface
characteristics play an important role in the printing process. The most
important attribute of a stencil is its release characteristic. In other word, how
well the paste releases from the aperture. The paste release in turn depends on
the surface characteristics of the aperture wall and stencil foil surface. Recent
introduction of a new technology, Nano-coating for both stencil and squeegee
blades, has drawn the attention of many researchers. As the name implies,
Nano-coated stencils and blades are made by conventional method such as
laser cut or Electoform then coated with nano functional material to alter the
surface characteristics. This study will evaluate nano-coated stencils for passive
component printing including 01005. Various print experiments will be
conducted using different stencil technology, stencil thicknesses, aperture size,
aperture orientation, aperture shapes, and selected paste type with optimal
print parameters, to understand the effect of chosen factors on the print quality.
Print quality will be determined by visual inspection and 3D measurement of
the paste deposit to understand the volume transfer efficiency.
Apex 2011, solder paste, transfer efficiency, area ratio, stencil technology, broadband printing, nano-coated stencil
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Posted on 11 Apr 2011
