On Thu, 5 Jul 2001 00:56:32 -0700, Shirley Xiao <[log in to unmask]>
wrote:

>IPC-TM-650 2.3.18 "gel time, prepreg material" 4.1
>states" Platen, hot plate or melting point apparatus
>capable of maintaining a temperature of 171.5 C +/-
>0.5 C (340 F +/- 0.9 F).
>
>Is that mean laminators need to have a thermalmeter
>with accuracy better than 0.5 C? I audited several
>plant but can not find one can meet this requirement.
>
>How big is the impact on gel time test result if gel
>plate temperature shifted?
>
>
>Regards
>Shirley
>
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Shirley,

at this temperature, 1°c will make approx. 6 seconds difference to the gel
time. It is also my opinion that gel time should only be used for guidance
and that the most critical characteristic is minimum melt viscosity.

Regards Michael

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