Hi TechNetters,

I've been asked by a client to do some SMT rework and he wants assurance
that this rework will have no adverse effect on long-term reliability. The
boards are 10 layer .063 thick FR4, roughly 4" long by 2.5" wide. One side
of the board is mainly taken up by two large heat-slug 304 pin DSP QFPs.
The other side has 14 SOJ32 memories and there are two more memories on the
first side. The client wants these 16 memories removed and replaced with
upgraded devices.
I plan to remove the SOJ memories by using a pair of Metcal irons with 700 F
blade tips, each blade is the full length of the device. With the boards
preheated to approx 200F, to minimize thermal shock, it will take less than
5 seconds per device to remove them. The heat will be localized and the
technique is similar to what we often use to remove chip caps or resistors.
We will hand solder the new devices in place.
The whole process should have no impact on the large DSP devices.  So what
do I say to the client regarding long term reliability?


 Thanks in advance.


Bob Perkins
SMT Manufacturing Process
Automation Technician
Aimtronics - Delta