A Response Spectrum Method and Post-layout Optimization for Mechanical Shock Analysis of 3D NAND BGA Packages

摘要

Ball Grid Array (BGA) package has become a popular solution due to its small footprint, cost effectiveness, and insatiable demand for memory packaging. The mechanical strength of high density interconnect (HDI) of 16-layer Printed Circuit Board Assemblies (PCBAs) with memory packages is becoming very critical, especially for 3D NAND flash. In a variety of flash memory products, such as memory cards, USB Flash Drive or Solid State Drive (SSD), the mechanical robustness of PCBAs is becoming the key factor in product reliability. In a normal mechanical shock test performed in accordance with IPC-TM-650, Method 2.6.5, the boards were subjected three times to a shock pulse of 100 Gs with a duration of 6.5 milliseconds in each of the three principal planes. However, the requirements have been harsher in mobile gadget application. Mechanical shock testing is challenging because it is destructive and time consuming. Hundreds of designs need to pass the product reliability tests during development stage, so it's too expensive to conduct the experiment for all of them. In this study, simulation models of shock tests for memory packages on rigid board using Response Spectrum Method in Finite Element Models (FEM) have been developed under different applied acceleration values to examine the structural integrity of solder joints. The strain values on the M.2 form factor were estimated from the FEM and compared with experimental data. A series of post-layout M.2 designs were performed, and optimization analysis was conducted to improve mechanical reliability.