First encountered, by observation, rework affects on neighboring devices a
few years ago. Developing our first SRT1000 station, I had difficulty with
16 layer up boards and super BGA's. Couldn't get any profile to work.

Was using SRT's Pro series nozzles with the upward vent to protect
neighboring devices outside the .200" keep out zone (needed for nozzle to
part physical clearance). You know the situation.

Couldn't get adequate reflow with nozzle contacting board surface, or near
contact. Raised nozzle off board about 80 mils and everything worked fine.
No matter what part or board thermal mass, the rework worked great. However,
noticed some component leads, on QFP's within about a half inch, were
partially reflowing. Talked it over with HP's super soldering guru and they
said that was definitely not good. Would have been good if total reflow was
effected. Must be that IMC thing again that I haven't figured out yet.

Anyway, to continue the rework process, I had two choices. One was to
continue my happy little adventure with the raised nozzle but use a thermal
barrier, using ceramic substrates and Kapton tape too shield the nearby
parts. The other was to replace the BGA's, using the SRT, and run the entire
assembly back through the BTU thereby reflowing everything again. Wonder how
much IMC this created?

Not a very good answer to your question. And, it raises another way too
obvious one from me.

MoonMan

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------