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August 2003

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Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 11 Aug 2003 11:58:16 -0400
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text/plain
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Z axis expansion may weaken or break the plated through holes.

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of
> [log in to unmask]
> Sent: Friday, August 08, 2003 8:47 AM
> To: [log in to unmask]
> Subject: [TN] Wave Solder Preheat
>
>
> Hello Technetters,
>
> I have a family of boards that to achieve 100% hole fill (I'm
> building to IPC-A-610C class 2 - yeah, I know 100% isn't
> required), I need to preheat the topside of the board to
> approximately 310F at about 1.75 ft/min (maybe a 6-7 second
> dwell).  I usually follow the 180-220F rule-of-thumb, so I'm
> asking: What are the potential or real problems?  Also, the
> flux is OA.
>
> The family of boards are .050-.070" made out of either FR4,
> GE TEK, or NELCO 4000-13.  They are also waved in a selective
> soldering pallet with an aluminum plate on the topside over
> 90% of the components to hold them in place per a design
> specification.
>
> Will I damage the board or components (with immediate
> noticeable failures or latent field failures)?  Or is the
> 180-220F guideline more from the old WS6536/Mil-Std-2000 days
> and todays fluxes, boards, and components can handle the temperatures?
>
> Thanks in advance for the help,
>
> Al Kreplick
> Sr. Mfg. Eng.
> Teradyne, Inc.
>

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