SMTA International Conference Proceedings


EFFECT OF SURFACE TENSION OF SOLDER ON UNDERSIDE DEVICE SUPPORT DURING REFLOW OF A PCBA

Author: Mulugeta Abtew
Company: Sanmina - SCI Corporation
Date Published: 9/22/2002   Conference: SMTA International


Abstract: An experimental approach was taken to investigate the capability of liquid solder to hold components in place during inverted reflow in a typical Printed Circuit Board assembly (PCBA) soldering process. Three lead configurations, namely Jlead, Gull Wing and Solder Balls were evaluated.

The maximum mass per lead that can be supported by the surface tension of liquid solder during bottom side reflow of a peripheral J-leaded device with 84 leads was determined to be 0.089 grams; for a Gull wing device with 208 leads the maximum supported mass per lead was 0.029 grams while for a 388 pin Plastic Ball Grid Array and a 48 pin CSP devices the maximum supported mass per lead was found to be 0.045 grams and 0.013 grams respectively.

Further, it was found that the weight carrying capacity of molten solder is strongly dependent on the size of the solder fillet area on a component lead. Analytical model to estimate the optimum weight of a device that can be supported by liquid solder during inverted reflow is proposed.



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