Survivability assessment of electronics subjected to mechanical shocks up to 25,000g

Mechanical drop testing and reliability of BGA electronics in consumer markets is conducted using the JEDEC JESD22-B111 standard. The JEDEC form factor PCB may not be suited for use in part survivability assessment at very high-g levels up to 25,000g. Product board geometries may need to be considered for survivability assessment in fuzing applications. Commercial-off-the-Shelf (COTS) parts like fine pitch BGAs of 0.4mm and 0.5mm pitch are increasingly being used for military and defense applications. Use of fine pitch Ball Grid Array (BGA) technology is preferred over the other packaging technologies due to relative ease of procurement relative to leaded parts, high level of integration with small foot print. Commercial parts may need supplemental restraints in form of underfills, and potting compounds to meet the reliability requirement of extreme-acceleration applications such as fuzing. Survivability of fine pitch semiconductor packages under high-g mechanical shock in the range of 10,000g–25,000g is unknown. In addition, the efficacy of the traditional supplemental restraint mechanisms such as underfills and potting in reducing the risk of interconnect failure under high-g mechanical shock, is not available. In this study, instead of using a JEDEC form-factor board, a product form-factor circular board with annular ring typical of end product projectile applications under harsh high-g operating environments of 25,000g was studied. Five different BGA packages of interconnects ranging from 84–360 I/O have been studied. Three configurations of the test board have been studied including non-underfilled, underfilled and potted assemblies. Lord Thermoset ME-531 has been used to underfill the packages in this test study. Two categories of potting compounds have been used including Armstrong A12 is a low modulus material and Henkel STYCAST 2850FT is a high modulus material intended for shock applications. Data on the survivability of BGA's using supplemental restraint mechanisms like underfill reinforcing the packages and potting the PCB with epoxies is presented. Modal analysis of the unreinforced and supplemental restraint configurations has been done to understand the frequency response of the configurations.