Yes, that is the process I would use as well.
I have a BGA on a 63/37 HASL Polyimide board.
But I am not concerned about the board and what moisture it has
absorbed, the BGA is my main concern (MSD Level 4). It is expensive
enough that I don't want to throw it away, so I feel the need to bake it
prior to rework.

But when I bake the board, the conformal coating turns brown - is this a
problem?

Ben

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rodney Miller
Sent: Thursday, November 15, 2007 4:00 PM
To: [log in to unmask]
Subject: [TN] Conformal coating Rework

Per Ben Gumperts email.

 

I'm not sure the logic on baking a Conformal coated PCB?  If the coating
is working or you have residually absorbed moisture, you are creating a
problem by baking a CC'ed PCBA in my opinion.  The barrier of conformal
coating Ureathane or otherwise should be easy to remove and locally
repair with localized Reflow system.  If you are totally reflowing the
PCBA, that is even larger problem on rework.

 

I would remove the part, with hot air.  

 

Remove Conformal coating with appropriate solvent from the area of
repair.

 

Rework/re-solder components

 

Reapply Components with localized Reflow and/or HotAir system.

 

There will be some aesthetic issues, but with proper solvents and
cleaning, you should not have issue with moisture in the PCBA more than
any other issue.

 

Is this RoHS or 63/37 solder?

 

How long have they been in Ambient conditions?

 

What is the laminate?

 

What is the plating?

 

What technology is the components that are to be reworked?

 

Just my couple of CNY..

 

Rodney


---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 15.0
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
-----------------------------------------------------