BGA inspection (Abstract)

Summary form only give as follows. BGAs (Ball Grid Arrays) have drawn much attention as the rising star of high-pincount surface mount packaging technology. Compared to fine-pitch QFPs they offer: a higher pincount for a given area, the ability to use existing or at least less costly mounting equipment, and lower solder defect rates. Disadvantages are a higher package cost and the inability to inspect the solder joints after reflow. It has been argued that the cost disadvantage goes away when overall manufacturing costs through finished product are taken into account. The problem of not being able to physically inspect the solder joints may never go away. However, one can mitigate the need to inspect solder joints by physical inspection of the BGA prior to mounting. This paper discusses the physical attributes of a BGA which contribute to poor mounting and how 3-D laser inspection can be used to check those attributes. The presentation focuses on the use of a laser system to measure coplanarity, true position error, pitch, ball diameter, and board warpage. Also addressed are issues associated with inspection of BGAs as presented to the placement system. Future applications of 3-D inspection are mentioned