A common (but destructive) test for determining the Tg of a material is
Differential Scanning Calorimetry (DSC). You subject a small sample (mg
scale) to a (usually linear) temperature scan covering the range you suspect
Tg to be in. The slope of the absorbed-energy curve is related to the heat
capacity of the substance. At Tg, there will be a heat capacity change.
Depending on the thermal history of the substance, there may also be a
"bump" in the curve at Tg cause by enthalpic relaxation. DSCs are common lab
equipment in materials science and other fields. It may be possible to have
such tests done by a contact lab if you just want Tg of a given substance
(say an epoxy). This will likely prove too troublesome if you want to, say,
check the Tg of each new batch of PCBs you get.

Yves Dupuis
Leitch Technology

> -----Original Message-----
> From: Le Dai Tri [SMTP:[log in to unmask]]
> Sent: Monday, August 14, 2000 5:40 AM
> To:   [log in to unmask]
> Subject:      [TN] Procedure for Tg measuring
>
> TechNeter,
>
> We purchase Prepreg in roll then cut into suitable worksize, before
> sending prepreg to Laminating process we have IR heating process:
> Maximum heating temperature was 115 deg.C (FR-4).
>
> 1. Can anyone have any experiences about this treament ? it is effect
>     or not ? Does it effect Tg of Prepreg material?
>
> 2. Can I measure Tg by ourselves ? I want to confirm Tg before and
>     after IR treatment. If posible please show me where I can get
>     procedure.
>
> Any help would be appreciated.
>
> Best regards,
> Tri'.
> _______________________________________
> E-Mail    : [log in to unmask]
> <mailto:[log in to unmask]>
>
>

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