Mumtaz Y. Bora
San Diego, CA, USA
Wire bonded packages using conventional copper lead frame have been used in industry for quite some time. The growth of portable and wireless products is driving the miniaturization of packages resulting in the development of many types of thin form factor packages and cost effective assembly processes. Proper optimization of wire bond parameters and machine settings are essential for good yields. Wire bond process can generate a variety of defects such as lifted bond, cracked metallization, poor intermetallic etc. NSOP - Non- stick on Pad is a defect in wire bonding which can affect front end assembly yields. In this condition, the imprint of the bond is left on the bond pad without the wire being attached. NSOP failures are costly as the entire device is rejected if there is one such failure on any bond pad. The paper presents some of the failure modes observed and the efforts to address NSOP reduction .
Die bond pad quality can be affected in numerous ways during processing and handling. Both wafer fabrication and assembly facilities as well as intermediate process owners such as probe/back grind/laser scribe/singulation operations need to address outgoing quality issues with proper detection and preventive methods. Automated Optical inspection (AOI) is a valuable tool in screening defects and categorizing them. Successful and reliable wire bonding can be achieved by contamination free surface, machine maintenance, optimized process settings and providing an optimal bonding environment.
Initially Published in the SMTA Proceedings