TABLE OF CONTENTS Paul Wood and Howard Rupprecht
Metcal, Inc.
As array package components become increasingly accepted in mainstream production, one of the most commonly asked questions is, How can I rework these new components? Many existing installed QFP rework machines may not have the required features for successful ball grid array (BGA) or chip scale package (CSP) rework. While rework of these components is not difficult, there are certain pitfalls that can be avoided if the engineer understands the method of interconnection, the different rework options, and the application of the product being reworked.
If we compare a peripheral lead package such as a QFP with an array package such as a BGA or CSP, the fundamental difference is that one has leads on the perimeter and the other has an array of solder balls on its underside functionally the packages are the same. If we are reworking a QFP and a defect occurs, it has always been possible to touch up that defect with a conventional soldering iron, repairing the fault. Engineers traditionally have had this safety net that often has meant that less process control was applied to the rework operation.
With any array package, when it is assembled, there is no possible way to touch up a defective solder joint making complete package removal mandatory. Since none of us want to be perpetually removing and replacing devices, a greater level of process control is required to ensure that we...
