Papers about stencil technology
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
by Marty Carr, John Carr, Richard Brooks
New assembly technologies are being considered for production to reduce size and/or increase functionality. These new technologies include: 0201 & 01005 chip components and 0.4 mm & 0.3 mm pitch CSP devices. In order to implement these new technologies, some major changes in the manufacturing process may have to be addressed. First, the solder paste must provide the ability to print very small apertures, such as 0.008" (0.2mm) & below and with consistent paste release from the stencil. Therefore, one of the possible solutions may be to change the standard solder powder size, which is type 3 powder. Also, because we are printing very small aperture openings, we need to consider changes in the stencil technology. Some of those changes are the stencil type (laser versus electroformed) and the stencil thickness. Additionally, because we are attempting to print very small apertures, the printing process must be in control and characterized. This paper will review the new technology requirements and how they will affect the performance of the solder paste and stencil technology in the manufacturing process, as well as the printing process.
fine pitch printing, stencil technology, stencil design, pad design, solder powder, process characterization, solder paste
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Posted on 8 Mar 2010
by George Babka, David Sbiroli, Richard Brooks, Chris Anglin
With the introduction of 01005 chip components and 0.3 mm pitch CSP devices, electronic component packaging is pushing surface mount technology to the limits of its potential. Miniaturization is driving the electronics industry to implement the smallest and tightest pitch components in order to meet their customer demands. But how much miniaturization is possible before there is a paradigm shift in the technology? At what point is solder paste no longer viable? How small of a feature can be printed with solder paste, and can this process be implemented into a production environment?
Most of the factors and critical parameters in ultra-fine pitch printing have been well understood and documented for over twenty years. Some of these parameters are squeegee speed, squeegee pressure, stencil design (technology, thickness & area ratio), and solder paste. But as the pitch and aperture sizes get smaller and smaller, we begin to see that additional factors start to have an increased effect on the solder paste deposition (transfer efficiency). What are these factors and can we control them in order to obtain acceptable results for transfer efficiency and minimized variability? This paper will evaluate these additional factors and how they affect the transfer efficiency of the paste.
ultra-fine pitch printing, separation speed, stencil technology, stencil design, pad design, solder powder, tooling, solder paste, area ratio
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Posted on 15 Oct 2009
