Evaluation of High Temperature Overmold Compounds for Manufacturing of Laminate Based Leadfree System in Package

摘要

The worldwide push for leadfree microelectronics has caused the industry to revamp its design, material selection, and manufacturing processes of its products. However, the needs of industry have surpassed the current leadfree standards set up by organizations such as JEDEC. This paper looks into how ANADIGICS defined internal standards, reviewed customer needs, and met them by using unique materials and processes prior to the release of leadfree standards for laminate based modules. Laminate based system in package products, which combine assembly process and materials, historically, have been limited to meeting Moisture Sensitivity Level (MSL) 3 at 240 °C. It is now possible to achieve this level at 260 °C-a temperature requested by customers for leadfree assembly. The use of lead free solders has caused a significant rise in the reflow temperatures of packages and has therefore prompted the need for high-temperature overmold compounds. The high temperature capabilities of several overmold compounds that could be used to encapsulate laminate based modules were evaluated. Five overmold compounds were subjected to conditions specified for MSL 3 with a reflow peak temperature of 260 °C. Three of the five overmold compounds that provided positive results were subjected to the more aggressive stress test of MSL 2a at 260 °C. Comparison of pre and post stress electrical tests to determine the change in electrical parameters, and comparison of pre and post stress sonoscan images to determine the change in percent delamination were used to judge the performance of the overmold compounds. Failure analysis was also performed on the modules to look for evidence of solder mask delamination and/or solder extrusion.