Published in Proceedings of the 1999 International Symposium of Microlectronics (IMAPS'99): Chicago, IL, October 26, 1999, pages 532-537. Copyright 1999 International Microelectronics And Packaging Society.
NOTE: At the time of publication, the author Jianbiao Pan was not yet affiliated with Cal Poly.
Due to the increased use of Ball Grid Arrays (BGAs) and fine pitch and ultra fine pitch Quad Flat Packages (QFPs), there is a dramatic increase in demand for solder paste inspection after the stencil printing process. The important response variables of the printing process are deposited solder paste volume, area, height and position. To identify and remove defects at the earliest possible process step, a 3-D solder paste inspection system should be used to monitor solder paste deposited on all pads on every board before component placement. An example is a fully automatic laser-based 3-D triangulation solder paste inspection system that is currently used for inspection of 0.635mm (25mil) pitch QFP components of automobile electronics products. As the pitch of QFP components decreases and the use of BGA components increases, the gauge repeatability & reproducibility (R&R) of the inspection system must be reevaluated. This work investigates whether the present system can be used for measuring 0.4 mm and 0.3mm pitch QFPs and BGAs. An experiment was conducted featuring 2,400 pads of 5 different pitch levels of QFPs and BGAs from 0.3mm (12mil) to 0.76mm (30mil). The analyses show that the system is capable of measuring solder deposits higher than 0.025 mm (1 mil) with repeatability of 5% for volume and area measurement, and with repeatability of 5% for average height of the majority of pads and 18% for all pads. In addition, there are requirements in board design necessary to ensure the reference points for measurements can be specified close enough to the pads.
Industrial Engineering | Manufacturing