Thanks Dennis and Paul for the response.
Dan S.
----- Original Message ----- 
From: "Dennis Fritz" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, June 29, 2009 10:13 PM
Subject: Re: [TN] Operating Temperatures


> Nearly all printed circuit boards are rated by Underwriters Laboratories.?
Dan - you are touching on the
> maximum operating temperature for the lowest rated material in the build.?
Epoxy and the coverlay are
> UL rated at only 105C, so that is the maximum you can safely operate the
board, while getting a UL
> certification.?? Your board shop will have a UL maximum temperature for
its product boards, through its
> initial certification, and will have had its boards sampled annually to
remain certified.? Here is a pretty
> good presentation from UL to get you started.? Maximum operating
temperature is in the middle.
>
>
http://www.ul.com/global/eng/documents/offerings/industries/chemicals/plastics/ThermalManagement_April2008.pdf
>
>
> -----Original Message-----
> From: Dan Skweres <[log in to unmask]>
> To: [log in to unmask]
> Sent: Mon, Jun 29, 2009 3:59 pm
> Subject: [TN] Operating Temperatures
>
>
>
> I have a question regarding operating temperatures. Specifically regarding
bare
> board level. It's actually opened up dialogue here as well as with my
material
> suppliers. What is taken into consideration when determining the operating
> temperature of the board? I understand most base materials have a maximum
> operating temp. but what characteristics (electrical, mechanical etc.) are
taken
> into consideration when determining the operating temp of a bare circuit
board
> with mask, legend etc.? Is it just the base material that is a concern or
a
> combination of all co-mingled elements on the board? I have spoken to a
> representative at DuPont and they, for example, stated that AP material
alone
> has a maximum operating temperature of 180C but when FR or LF coverlayer
> material is applied then the operating temp goes down to 105C due to the
acrylic
> adhesive present. If this is true then wouldn't a mask applied to either a
> flexible or rigid board influence the operating temp? If so, is testing on
each
> and every option(s) of materials then necessary? Or... is there a simpler
method
> of determining the operating temp. of the bare board?  Just curious.
> Thanks in advance!
> Dan S.
>
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