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November 2008

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Subject:
From:
Werner Engelmaier /* <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 12 Nov 2008 15:58:12 -0500
Content-Type:
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 It is the Tg determined by TMA that is the one reflecting the CTE changes.

Werner


 


 

-----Original Message-----
From: Paul Reid <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, 12 Nov 2008 2:39 pm
Subject: Re: [TN] Tg specification










Not all Tgs recorded are reflection of changes in CTE. There are three
DMA based Tgs. One each for Young's' modulus, loss modulus, and tan
delta. DSC gives a fifth Tg.

Pick you operating temperature, test method, point of view ... 

Best regards,

Paul

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Syed Ahmad
Sent: Wednesday, November 12, 2008 10:25 AM
To: [log in to unmask]
Subject: Re: [TN] Tg specification

Tg being the transition temperature where CTE (commonly designated as
alpha
1) shifts to a higher value, FR4 Tg is no longer 14 or 15 ppm past its
Tg.
The CTE past the Tg (alpha 2) should be listed on the material
datasheet.
Higher CTE will cause more reliability problems than a lower CTE
depending on the operating temperature at a site or for the system. To
determine the effect of Tg, operating temperature needs to be measured
or simulated.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bryan Montney
Sent: Tuesday, November 11, 2008 1:49 PM
To: [log in to unmask]
Subject: [TN] Tg specification

I'm looking for a guideline or resource (IPC spec?) on how to select and
specify the proper Tg for a given design? I'm not talking about process
wise (Tg140 is acceptable in our lead-free processes), but design wise.
For example, is Tg140 material sufficient for a board running 80amps
through it and sitting in an enclosure on a hot summer day in Arizona?
Also, I'm looking for how best to test the Tg robustness during
production.
Any help would be greatly appreciated. 

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It is the 


 


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