Glen,
My interpretation has been 0.5% per inch, especially for boards with
(large) BGA's. You can have an overall warp of 0.5% that is considerably
more in local areas, so if I have concernes about warpage, I check the
critical areas as well as the overall board. If your boards are properly
made, they shouldn't warp any more as a result of assembly processing. The
acceptable degreee of warping, within recognised limits, depends on how
flat YOU need the board to be. If you receive boards from your fab house
that are regularly warped close to the IPC acceptable limit, and this is
not good enough for your vacuum processes, you will have to impose tighter
tolerances yourself. If your fab house cannot meet your requirements -
well, time to find a new fab house that can.
Tough ol' world, ain't it?
Peter
Glenn Pelkey <[log in to unmask]> 29/10/2002 01:13 AM
Sent by: TechNet <[log in to unmask]>
Please respond to "TechNet E-Mail Forum."; Please respond to glenn.r.pelkey
To: [log in to unmask]
cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: Re: [TN] WARPAGE
We apply IPC-6015 to much of our product, which requires 0.5%. After SMT,
there are a number of fixtures that require the board to be flat for vacuum
hold down or epoxy dispense processes.
Now tell me if I'm interpreting this wrong. I apply the 0.5% limit at
incoming, and apply the 0.75% limit after SMT. Sound correct?
Glenn
-----Original Message-----
From: Franklin D Asbell [mailto:[log in to unmask]]
Sent: Monday, October 28, 2002 8:31 AM
To: [log in to unmask]
Subject: Re: [TN] WARPAGE
Would that criteria also apply to "populated" boards? I believe he
was seeking data for populated boards...curious...would it matter
after assembly if they were warped or not???
Franklin
----- Original Message -----
From: Eric Castonguay
To: [log in to unmask]
Sent: Monday, October 28, 2002 10:14 AM
Subject: Re: [TN] WARPAGE
Pankaj,
check in IPC-6012 par. 3.4.4 Bow & Twist. The printed board shall
have a maximum bow & twist of 0.75% for boards that use SM
components and 1.5% for all other boards. Also, see test method
2.4.22 described in the "IPC-TM-650 test methods manual" on how to
measure it.
Eric Castonguay, Eng.
Manufacturing Engineering
www.Hyperchip.com
Montreal, Canada
T. 514 906 2409
F. 514 906 2501
-----Original Message-----
From: Karnwal, Pankaj [mailto:[log in to unmask]]
Sent: Monday, October 28, 2002 02:02
To: [log in to unmask]
Subject: [TN] WARPAGE
> Hi TechNet
>
> Can any body give me the acceptable range of PCB {Populated } For
> Warpage, { Both Throughole And SMD And MIX components} .And how
we can
> measure it. Also tell that what IPC states about this.
>
>
> With regards
> Pankaj Karnwal
> Quality Assurance Ext. 211
> BESL A-4,Sec-5 NOIDA , 201301, INDIA
> e mail : <mailto:[log in to unmask]>
> Barco, innovators in image processing
>
>
>
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