Automated X-ray inspection of chip-to-chip interconnections of Si-on-Si MCM´s

The silicon-on-silicon (Si-on-Si) multichip module (MCM) is one of the newest system integration technologies that has the potential for high functional integration, enhanced performance, and cost effectiveness. Aside from functional tests, X-ray inspection is required to ensure good quality chip-to-chip interconnections during the fabrication process. This paper presents an automated inspection system that is capable of detecting defects such as “swollen” solders, misaligned solders, missing solders, solder robbing, and solder bridging in a semi-finished MCM. The semi-finished MCM is in wafer form and has completed the following operations: stencil printing device placing, and solder reflowing. The defect detection methodology is detailed. Over a test set of 54 sample images of wafer tiles, 100% inspection accuracy was obtained. This system has the potential to automate the manual visual inspection operation which is tedious, slow, and error-prone