Hi All

We use 130C for SS/DS PWBs and 105C for ML PWBs. These are the most
common UL parameters from our supply base. I believe with some laminate
formulations it is possible for the laminate to get higher ratings but
it is the value that the board shop receives that is important to the
end user.

Also keep in mind that no matter what, even at 105C the resin system
will oxidize and become severely discolored after awhile in the field.

Regards

Gerry

-----Original Message-----
From:   LOGISTIC_0/JANINE'S_P/dieterb  On Behalf Of Dieter Beisiegel
Sent:   Monday, May 11, 1998 9:02 AM
To:     'TechNet E-Mail Forum.'
Subject:        RE: [TN] Maximum FR4 operating temperature

Hi Sam,
according to UL746 (?) the temperature limit for FR4 is 130 ºC.
Kind regards,
Dieter

        ----------
        From:   Sam Mollet[SMTP:[log in to unmask]]
        Sent:   Monday, 11 May, 1998 14:25
        To:     [log in to unmask]
        Subject:        [TN] Maximum FR4 operating temperature


        I have an application with a maximum ambient temperature of 70
°C.  I am using copper planes on FR4 to help cool some power resistor
leads.  The copper planes can hit 115 °C.  Is this a problem?  Is there
a rule of thumb on how hot FR4 can continuously be operated at? 

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