I agree with Lee. First we take every action to prevent bowing which is typically worse with PCBs that are 0.062" or under, that are long, approx 10" and narrow, 1.2" to 3". You may have to use sanp mask (solder plow) at either end of the panel for reflow.
The wave solder process may require you to purchase wave solder pallets that secures the boards with an overarm bar or thumbscrews through mounting holes or in the routed spaces between the PCAs that keep the individual PCAs in the panel flat .
A selective solder machine also achieves the desired result without buying wave pallets.
----- Original Message -----
From: "Gary Bremer" <[log in to unmask]>
To: [log in to unmask]
Sent: Monday, February 1, 2010 5:37:25 PM GMT -05:00 US/Canada Eastern
Subject: Re: [TN] IPC-7721 LESSONS LEARNED
Lee,
According to IPC-A-610
Acceptable - Class 1,2,3
• Bow and twist does not cause damage during post solder assembly operations or end use. Consider ‘‘Form, Fit and Function’’ and product reliability.
Note: Bow and twist after solder should not exceed 1.5% for through-hole and 0.75% for surface mount printed board applications (See IPC-TM-650, 2.4.22).
My interripertation is any bow/twist after soldering is not measured but usage at the next assembly level is considered ie. does the board mate in the card slot if yes then there is only and oberservation of a possible defect. I have only seen bare boards that have been warped past the acceptance certeria, during wave solder the boards will warp to some degree and will take a set only when the copper is unbalanced.
Gary Bremer
Senior Manufacturing Engineer
> Date: Mon, 1 Feb 2010 11:19:13 -0800
> From: [log in to unmask]
> Subject: Re: [TN] IPC-7721 LESSONS LEARNED
> To: [log in to unmask]
>
> Lee,
>
> Are these populated PCBs?
>
> Paul
>
> Paul Edwards
> Surface Art Engineering
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee Whiteman
> Sent: Monday, February 01, 2010 7:07 AM
> To: [log in to unmask]
> Subject: [TN] IPC-7721 LESSONS LEARNED
>
> We got some boards that are warped (bent & twisted that exceeded the
> flatness requirements per the J-STD-001). IPC-7721 has a repair
> procedure for warped boards. I'm getting a copy of IPC-7721 so I can
> familiarize myself with the process. In the meantime, does anyone have
> any "lessons learned" from using this procedure?
>
> THANKS.
>
> Lee Whiteman, PMP
> Senior Member Engineering Staff
> L-3 Communications East
> Telephone: (856) 338-3508
> FAX: (856) 338-2906
> E-Mail: [log in to unmask]
>
>
> ---------------------------------------------------
> 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
> -----------------------------------------------------
>
>
> ==============================================================================
>
> This email and any attachments thereto may contain private, confidential, and
> privileged material for the sole use of the intended recipient. Any review, copying,
> or distribution of this email (or any attachments thereto) by others is strictly prohibited.
> If you are not the intended recipient, please contact [log in to unmask]
> immediately and permanently delete the original and any copies of this email and
> any attachments thereto.
>
> ==============================================================================
>
>
> ---------------------------------------------------
> 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
> -----------------------------------------------------
_________________________________________________________________
Your E-mail and More On-the-Go. Get Windows Live Hotmail Free.
http://clk.atdmt.com/GBL/go/201469229/direct/01/
---------------------------------------------------
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
-----------------------------------------------------
|
