Electronics Assembly Knowledge, Vision & Wisdom
Stencil Design Improves Drop Test Performance
Stencil Design Improves Drop Test Performance
Paper evaluates the influence of stencil printed solder volume on electronic component lifetime in mechanical stress testing.
Materials Tech

Authored By:
Jeff Schake
DEK USA, Rolling Meadows, IL USA

Brian Roggeman
Universal Instruments Corp., Conklin, NY USA
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Summary
Future handheld electronic products will be slimmer than today and deliver more functions, enabled by innovative electronics packaging design using smaller components with greater I/Os assembled in higher density. As solder interconnects between component and circuit board shorten, they also become weaker. This causes us greater concern on the survivability of such delicate electronic interconnects under normal handling impacts and serves motivation for formal study. This investigation will evaluate the influence of stencil printed solder volume on CVBGA97 electronic component lifetime in mechanical stress
testing.

A stencil aperture design to print a lower limit of solder paste volume has been thoroughly characterized as the first step towards determining the range of print volumes exhibiting the greatest influence on drop, bend, and die shear test performance. In this printing focused piece of work, print volume measurements were found varied across different circuit board pad designs with no change in aperture size. Highest paste volume transfer consistently occurred with solder mask defined pads. Stencil aperture and circuit board pad design variables are discussed in detail
Conclusions
This investigation has shown that stencil print volume and repeatability performance is not exclusively attached to compliance with aperture design rules, but is also strongly influenced by the circuit board pad design. It is incorrect to assume a common aperture size will print the same volume on different pad types.

Furthermore, the manufacturing tolerances associated with the circuit board can also have consequences on print registration and aperture gasketing quality. Additional print qualification testing will commence using larger aperture dimensions to build up a profile of print volume and repeatability metrics that will ultimately be compared against results of drop, bend, and die shear testing of assembled CVBGA97 components.
Initially Published in the IPC Proceedings
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