Hello,

Below it was stated that ' . . . the manufacturing process doesn't over cure
the material'.

What happens to PCB material that is overcured?  Does the dialectric of the
material change? Does it cause signal attenuation in the vias?

Thank you in advance,
 
David Tremmel
847 557-9574 - Phone
847 557-9573 - Fax
http://ValuRecovery.com
 
VALUE RECOVERY
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ted Tontis
Sent: Viernes, 05 de Octubre de 2007 09:21 a.m.
To: [log in to unmask]
Subject: Re: [TN] Via plugging with LPI soldermask...

Werner,
	I will be the first to admit I am not an expert in the matter of
HWPA and I can only relate to the few articles I have read. You wouldn't
find them in unprocessed PCB's because the material around the hole is not
cured correctly. As the boards continue through the process they continue to
cure, there by shrinking the material causing resin recession. Board
material that is correctly cured by the board house is slightly under cured.
The reason for this is so that the manufacturing process doesn't over cure
the material.  
As a board reaches its Tg it expands in the Z axis not the x or y axis.
Another point is with the different types of resin content, fabric
reinforcement and PWB constructions would it difficult to graph or trend the
relationship between CTE and hole wall reliability.

Ted T

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Friday, October 05, 2007 1:40 AM
To: [log in to unmask]
Subject: Re: [TN] Via plugging with LPI soldermask...

Hi Ted,
I cannot agree with what you relate from that article as the causes of 
HWPA and resin recession-if that were so, you would find them in 
unprocessed PWBs. They are only found after exposure to soldering 
temperatures, and result directly from the large CTEs of the resin 
above Tg.

Werner

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