An analytical model is presented in this paper to study the warpage of plastic ball grid array (PBGA) packages subjected to uniform thermal loading. This model was derived from the classical laminated plate theory (CLPT). Based on theconfiguration of PBGA, the package was considered as a three-layer 2-D laminate with two regions, namely, with chip and without chip. The curvature in each region under a certain temperature raise was calculated by the CLPT. From direct integration, thewarpage of the package could be evaluated. The present model was applied to study the effects of various parameters on the package warpage. The parameters under investigation included the chip size, the chip thickness, the BT substrate thickness, and thethickness of molding compound. Some interesting phenomena were identified. The present model provides the electronics packaging engineers with a convenient tool to evaluate the warpage of their PBGA package design instantly.
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