Loan, are you talking solder mask blisters or de-lamination blisters. No
matter which condition, a 250 C excursion or 2 should not produce a problem
with mask or lamination.


At 08:18 AM 08/25/2005, you wrote:
>Hi Technos,
>
>wanted to start a pilot run, but the first PCB that we soldered ended up
>full of blisters when it came out of the oven. It is a 6 layers, full
>ground and power planes, about 6"x7", not a high density one, pretty light
>stuff on it, the toughest part is a transformer which needs a little more
>heating. The profile peaks at 250C on the PCB itself and the PCB is made
>out of FR4, Tg 170.
>
>I said to myself that it must be humidity, so I baked 1 board, 8H @ 125C,
>and passed it through the reflow again. Same blistering, almost to the
>same extent. Then I took a totally different PCB that was hanging around
>on my desk for about 3 months, reflowed it at 250C and got just a tiny
>blister, probably due to humidity this time.
>
>The questions I have are:
>
>is 250C too much for a properly manufactured PCB?
>
>If it's not the humidity what else could it be?
>
>Any other test that I could do to get a better idea of the root cause?
>
>Thanks,
>Ioan
>
>
>
>---------------------------------------------------
>Technet Mail List provided as a service by IPC using LISTSERV 1.8e
>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 or (re-start) delivery of Technet send e-mail to
>[log in to unmask]: SET Technet NOMAIL or (MAIL)
>To receive ONE mailing per day of all the posts: send e-mail to
>[log in to unmask]: SET Technet Digest
>Search the archives of previous posts at: http://listserv.ipc.org/archives
>Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
>for additional information, or contact Keach Sasamori at [log in to unmask] or
>847-615-7100 ext.2815
>-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------