Life Prediction and RUL Assessment of Fine Pitch Solder Joint Fuze Electronics Under Mechanical Shock Loads Up to 50,000g

Commercial electronics parts are increasingly being used in high-g fuzing applications. Sustainment of long-term systems requires the understanding of the survivability limits on newer fine pitch part architectures. In this study, the survivability of 0.4mm pitch and 0.5mm pitch parts at acceleration levels upto 50,000g have been studied for bare test boards, underfilled test boards, and potted test boards. In consumer electronics, survivability in mechanical shock is ascertained using the JEDEC JESD22-B111 test standard which involves the use of 1500g, 0.5ms shock pulse in a standard 132mm x 77mm, 15-parts test board. Consumer products may be designed in a number of form factors which may likely differ from the test board size and part configuration. Correlation of performance in JEDEC test to actual product performance is often weak. In order to alleviate this limitation of the JEDEC test, the test assembly in the present study has been designed in the form factor of the actual use application to be circular with an annular ring in the center. Two categories of underfills has been used including Lord Thermoset ME-531, and Loctite UF 3811. Two categories of potting compounds have been used including Armstrong A12, Henkel Stycast 2850FT. Armstrong A12 is a low modulus material and Henkel Stycast 2850FT is a high modulus material intended for shock applications. Digital image correlation has been used to measure the strain field of the board assembly during impact. Failure of interconnects has been detected using a high-speed data acquisition system. The transient dynamic motion of the board assemblies and the strains in interconnects have been modeled using ABAQUS Explicit finite element models.