Russell,
I'm speaking also from a board shop perspective. We're working on a 3-layer
board at the moment, with a construction so out of whack it will indeed be
warped after rout...the customer is aware of this...and will 'make the
boards work' when they recieve them... We see this often, I don't believe it
is their 'choice' or 'inability' as much as not being aware of alternative
layups that might work.
We receive our fair share of out-of-balance designs...whenever possible we
try to alter the customer to the possibility of warpage...and at the same
time offer a solution to their design...in a diplomatic manner of course
(grinning)... Most of the times they follow our lead and everything works
out well...those time when they insist (for whatever reason) it be made we
make sure it is indeed documented in the purchasing documents, etc...and we
move forward... just more things to think about...
Franklin
----- Original Message -----
From: "Russell Burdick" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, October 30, 2002 9:26 AM
Subject: Re: [TN] WARPAGE
> 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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