BOARD-LEVEL THERMAL CYCLING AND MECHANICAL BEND RELIABILITY OF HiCTE FLIP-CHIP BGAS WITH MULTIPLE BGA PAD SURFACE FINISHES
Authors: Rajiv Dunne, Kejun Zeng, Sergio Martinez, Venu Cha Company: Texas Instruments, Inc. and Kyocera America, Inc. Date Published: 9/24/2006
Abstract: High pin count ASIC packages have stringent fan-out, electrical performance and reliability requirements. In order to meet these requirements a high thermal expansion coefficient (HiCTE) ceramic flip-chip BGA was used. Board-level thermal cycling (T/C) testing was done on 42.5mm and 51mm packages. 4-point Monotonic Bend test and Ball Pull (CBP) test was done to assess interfacial strength of the solder joints. In 0-100C BLR T/C test, the characteristic life of solder joints in both packages was found to be in excess of 4500 cycles. There were no brittle fracture failures in T/C or Monotonic bend tests. These results showed the BGA package, assembly process, and solder joint metallurgy resulted in a robust system. Based on above accelerated test results, we estimated projected field life using the modified Coffin-Manson equation. Our analysis showed these packages meet the reliability requirements in a typical systems application. Additional tests were done to assess the viability of an alternate BGA pad surface finish using NiPdAu; the effect of Pd thickness on solder joint strength was characterized and is reported here.