Tom,
(1) Over heat the polyimide board will result dis-coloration and
brittlement.
(2) yes, not all the polyimide are made equal.
(3) TMA is more sensitive than DSC for the Tg measurement. Usually, a bit
lower Tg observed when use TMA technique compare to DSC.
my 2 cents.
jk
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of Tom Waznis
>Sent: Wednesday, September 18, 2002 10:37 PM
>To: [log in to unmask]
>Subject: Re: [TN] Poyimide cure
>
>
>Pretty hard to overcure Polyimide with that high a Tg. Too long at
>high temperatures can make the material more brittle.
>Hope your using one with Tg of 240-260 (similar to the old 601, 601A
>resin that is no longer available). Some of the new ones have
>significantly lower Tg.
>
>
>Since Polyimide resin systems now vary (no more 601A) from supplier to
>supplier The supplier should be consulted. In general the heat rises
>are similar to FR4s but the material is usually significantly thicker
>than FR4 while it is flowing. Higher pressures than FR4 are typical
>but not really needed for all builds; depends how much you are
>actually filling.
>
>Tg can be done anytime. DSC or TMA is ok; I prefer DSC.
>At lest one formula requires two cure times / temperatures and time at
>the higher temp. does NOT count for the first required time at the
>lower temp.
>
>[log in to unmask] wrote:
>> Technetters:
>> I'm looking for information on the best way to confirm cure on a
>> polyimide board. The particular part is a sequential lamination
>> structure.
>> My questions include:
>> 1. Is the best time to confirm cure of polyimide immediately after
>> final lamination?
>> 2. Do the polymers created require a specific cure test, e.g. is TMA
>> best, DSC, or other method?
>>
>> Also, can overcure be a problem with Polyimide?
>>
>> And, does this material offer special challenges with respect to gel
>> time, resin flow, etc?
>>
>> I've already heard differences of opinions, and am looking forward to
>> more avenues of knowledge from Polyimide experienced folks.
>>
>> Mark Julstrom
>>
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