Linear steady state finite element models have been performed tosimulate thermally induced stresses on 225 I/O plastic ball grid array(PBGA) packages under thermal cycling (TC) condition. Eutectic solderjoints (63%Sn, 37%Pb) in shapes of barrel and hourglass have beenstudied. The effects of thermally induced stresses on the solder jointsbetween BT (Bismaleimide Triazine) substrate of PBGA and FR-4 printcircuit board (PCB) are studied as a function of four parameters: (a)coefficient of thermal expansion (CTE) of molding compound, (b) heightof solder joint, (c) size of solder pad, and (d) location of siliconchip. Furthermore, the warpages of a PBGA substrate caused by transfermolding and solder reflow processes are discussed. Several PBGA designswith minimum thermal stress are proposed based on the above finiteelement analysis results
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