Assembly Process Influence On Mechanical Test Performance Of 0.4mm Pitch CSP And LGA Components
Authors: Jeff Schake and Brian Roggeman Company: DEK International and A.R.E.A. Consortium Date Published: 10/16/2011
Abstract: Drop testing represents an amplified simulation of accidental mishandling that routinely occurs with handheld electronic appliances. A carefully structured drop test accelerates the damage induced on populated circuit boards, permitting efficient discovery of failure mechanisms that can be used to improve the mechanical stress tolerance designed into next generation products . The driving purpose of this work was to correlate effects of different stencil printed solder paste volume on drop shock reliability. We found that drop test performance improved by simply increasing the printed solder volume for balled array components (i.e. CSPs). Identical components supplied without pre-attached solder balls (i.e. LGAs) were assembled and drop tested to compare. The LGAs exhibited consistently high drop reliability for both high and low printed solder volumes. Further investigation into solder joint failure mechanisms show that the combination of low solder print volume with air reflow atmosphere can inhibit wetting enough to form stress concentrations which drastically reduce drop reliability for CSPs.
Stencil, printing, drop test, mechanical reliability, CSP, chip scale package, LGA, land grid array.