Abstract
Recently, Motorola was notified that certain of their RFIC devices had failed electrically during Accelerated Life Testing (ALT) at their customer’s board-mounting facility. These devices were assembled in both 8 and 16 lead narrow-body SOIC packages, and had been previously qualified ‘by comparison’ as JEDEC Moisture Sensitivity Level (MSL) 1, indicating that the packages could be shipped without dry packing and left indefinitely at factory-level temperature and humidity, without the need for pre-baking before surface mount reflow. The returned parts exhibited delamination of the mold compound from the die surface, in some cases resulting in wire bond lifting. Since the parts had been shipped as MSL1 for several years in some cases, it was not deemed necessary to investigate whether the customers, Motorola N.S.S. in Fort Worth, TX, and Swindon, U.K., had implemented any changes in their handling procedures which may have impacted the MSL performance of the packages. At the beginning of February, 2000, because of the fact that the SOIC packages were assembled at an external subcontract facility, the issue was brought to the attention of the Motorola External Manufacturing Quality (EMQ) and External Final Manufacturing (eFM) organizations. A containment action was immediately implemented at the assembly site, which consisted of large-scale Scanning Acoustic Microscope (SAM) inspection of the assembled devices, to identify delamination after post mold cure (PMC). A separate series of more in-depth engineering analyses were also initiated, centering on three main areas: 1, Possible die surface contamination; 2, Possible mold compound material issues, and 3, Possible molding process variation. All such activities were conducted with the support and assistance of the IC packaging subcontractor. Results gathered from these activities are summarized below.
