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October 2002

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Subject:
From:
Russell Burdick <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 30 Oct 2002 08:26:15 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (259 lines)
As mentioned in this group before, if a board is designed to warp you are
getting what you wanted. I speak from a board manufacturing company that
deals with customers unwilling to change construction to eliminate their
"warped" designs. It's their choice or their inability to change that will
continue the cycle of warp.

Board manufacturers can be the cause of warp, we can also help customers
eliminate/reduce warp.

Russell Burdick
Process Engineer






>From: [log in to unmask]
>Reply-To: "TechNet E-Mail Forum." <[log in to unmask]>, [log in to unmask]
>To: [log in to unmask]
>Subject: Re: [TN] WARPAGE
>Date: Tue, 29 Oct 2002 11:48:46 +0800
>
>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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