Hi Leo,



I agree with Werner. The material systems act differently above and below Tg. At the same time different materials will have different CTEs above and below Tg. It is not surprising that A does not correlate to B. 



If the difference between material A and B is only glass style then I would expect the relation of CTE to be consistant although the CTEs would be different between the two materials. If the difference is in the epoxy systems with the same glass style then your observation is not surprising. Variations in lamination and the degree of cure of the material are influential and may add to confound results.



You should also note that CTE” may have subtle changes in onset with each thermal excursion giving us the delta Tg. The effect of assembly and rework can significantly change the thermal mechanical attributes of materials. Lately I am concerned that loss in elasticity, stiffening of the material, and time to decomposition (Td) may be more important than CTE or Tg in predicting material reliability in lead free applications.



Best regards,



Paul



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Lin Leo

Sent: Monday, September 01, 2008 6:52 AM

To: [log in to unmask]

Subject: [TN] TMA result



  

Hi,

 

Recently, I tested CTE for two material(A & B) with TMA.  I found Z-a1(A<B) but Z-a2(A>B).  How can I explain about that result?  What's the physical properties between these two material in a1 & a2?

 

Best regards

 

Leo





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