Franklin offers good advice; many circuit boards should be baked prior
to processing.
Immersion silver boards are prebaked on a regular basis throughout the
industry, and IF they are packaged and stored properly per IPC-4553
(read it, please) they can easily be baked for up to 24 hours @ 105 deg.
C, which I know is more than enough to remove more than 85% of the fully
saturated moisture content of a printed wiring board that is 36" wide by
24" high and consists of 48 layers with 18 miles of embedded copper,
.50" thick, 180 Tg with no detectable drop in the solder DPU or
reliability.
On the other hand, Guy is correct in that reckless HANDLING and STORAGE
and baking at improper temperatures can quickly render the boards
unsolderable.
And as for immersion tin, well, that is really not a practical circuit
board finish... lets not go there today.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Tuesday, October 23, 2007 2:51 PM
To: [log in to unmask]
Subject: Re: [TN] Delamination of lead free PCBs
It should be noted that immersion tin and immersion silver may not
respond well to baking. Reckless methods can render the boards
unsolderable.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin D Asbell
Sent: Tuesday, October 23, 2007 1:39 PM
To: [log in to unmask]
Subject: Re: [TN] Delamination of lead free PCBs
Joel,
Baking was indeed required for leaded PCBs, the nature of most laminates
is to suck up moisture regardless of the Tg or final finish. Also,
depending upon the laminate type, baking may be necessary immediately
upon receipt from the board supplier. I always caution assemblers to
bake boards regardless, it just makes good sense.
Franklin D Asbell
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joel Alexander
Sent: Tuesday, October 23, 2007 11:23 AM
To: [log in to unmask]
Subject: [TN] Delamination of lead free PCBs
Has anyone experienced an increase of delamination when processing in a
lead free environment. Typically 4 to 6 layer pcbs during SMT reflow. We
are using the high temp laminate suggested for our process. When we
contacted the supplier and they indicated that any PCBs that are over
six months old should be baked prior to processing. This was never
required with leaded PCBs.
Is anyone seeing the same condition and similar feedback from your PCB
suppliers
Joel Alexander
Quality Assurance Manager
TT APSCO, INC.
---------------------------------------------------
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
-----------------------------------------------------
---------------------------------------------------
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
-----------------------------------------------------
|
