It also is effected by the grain of the copper, warp in the grain direction is usually more severe.
Joseph Spicuzza
Production Supervisor
Millennia Technology, Inc.
1105 Pittsburgh Street
Cheswick, PA 15024
724 274-2222 PHONE
724 274-2235 FAX
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Ivanoe Pedruzzi
Sent: Friday, December 16, 2005 4:04 AM
To: [log in to unmask]
Subject: Re: [TN] PCB warping due to copper imbalance
I guess it has more to do with CTE .
CTE for Copper is much less that the CTE of the substrate.
To me, that should end with having the side with more Copper bowed
inward as you experience.
But I'm still learning.
Ivan
Il giorno 15/dic/05, alle ore 20:53, Blair K. Hogg ha scritto:
> That's exactly opposite of what is actually happening.
>
> Perhaps it is due to the WS process where the top side is not
> getting as hot as the bottom?
>
>>>> [log in to unmask] 12/15/05 02:49PM >>>
> The side with most metal will expand more and will tend to
> curve the board toward the lesser metal side while is heated. The
> board will shrink back but not all the way to its original shape
> when it cools. An uneducated guess. Board fabricators will know
> exactly what happens.
> Regards,
> Ramón
>
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair K. Hogg
> Sent: Thursday, December 15, 2005 9:07 AM
> To: [log in to unmask]
> Subject: [TN] PCB warping due to copper imbalance
>
> We have a motherboard type PCB assembly that constantly warps
> during the wave soldering process. From what I've learned on this
> forum, I believe it is due to a copper imbalance from the top layer
> to the bottom layer - the PCB is a 2 layer assembly, with traces on
> the bottom and ground planes on the top.
>
> My question is this - is it typical that the warping will occur
> towards the side with more copper (the side with more copper will
> be bowed inward)?
>
> Thanks,
>
> Blair
>
>
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Ciao,
Ivan
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