Optimized acoustic microscopy screening for multilayer ceramic capacitors

A program was having a significant number of early life failures due to infant mortality of Multilayer Ceramic Chip Capacitors (MLCC). Board rework was difficult and expensive due to the locations of the MLCC and the complexity of the board. The proposed solution was to develop an improved acoustic microscopy screen for MLCC with latent defects 30 MHz acoustic microscopy screening is unable to detect a significant number of life limiting defects MLCC. 50 MHz screening is able to detect the defects that were missed at 30 MHz. There was not a 100% link between the detection of an anomaly and a device failure in this study. Four factors were identified that correlate strongly with MLCC failure rates: (1) Dielectric composition (2) Delaminations (3) Size (4) Capacitance value greater than 100,000 pF MLCC program requirements have been changed to require 50 MHz two sided C-Mode Scanning Acoustic Microscope (C-SAM) 100% lot inspection. The enhanced screen had positive cost impact. A different transducer was required in a screen that was already in place. There was increased screen fallout of MLCCs but the reduced board rework/repair costs more than offset the part cost. Parts passing the enhanced screen have not shown the early life failure issue. Additional work is necessary to determine the effects on MLCC reliability of defects other than delaminations.