Coplanarity analysis and validation of PBGA and T2 -BGA packages

Plastic BGA (PBGA) has recently been extensively used in microelectronics package. However, its heat-dissipating capacity is limited to below 2 or 3 W, and thus fails to satisfy the requirement of high heat dissipation and improved electrical performance. This work offers a finite element analytic methodology to predict the coplanarity of T-2-BGA (Turbo thermal ball grid array) and PBGA, using ANSYS software. T-2-BGA involves inserting a heat slug into the molding compound of a PBGA. The material of the heat slug can be either aluminum or copper. Surface mount technology (SMT) of BGA is limited mainly by the coplanarity due to coefficient of thermal expansion mismatch, since the structure of BGA is asymmetric. The coplanarity is limited below 0.2 mm (8 mil) by the Joint Electron Device Engineering Council (JEDEC) standard (JEDEC Design Standard, No. 95-1, Section 14, Ball Grid Array, June 2000). Coplanarity analysis is performed for both PBGA and T-2-BGA, using ANSYS. Finally, a coplanarity experiment is conducted on the constructed specimens of PBGA and T-2-BGA, to confirm the analytic results. The results in this work establish the effectiveness of T-2-BGA in improving coplanarity. Moreover, the analytic results differ slightly from the experimental results, by 1.53-10.50%. The FEM model proposed here can be extended to optimize the structure of T-2-BGA. (C) 2002 Elsevier Science B.V. All rights reserved.