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temperature range

SV

#2419

temperature range | 20 November, 2000

Hello,

I have to design a PCB for which the customer have the following temperature requirements:

-55degC to +85degC operating temp. -61degC to +125degC storage temp.

My question is: does the FR4 material meet this conditions? Which are the parameters that shall I look for when I read the specification for the FR4 materials and how are these parameters interpretated?

If the FR4 material meet these temperature conditions and also the components mounted on my PCB meet these temperature conditions, are there other issues that have to be checked with regard to these temperature ranges?

Many thanks, SV

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#2420

Re: temperature range | 27 November, 2000

Gawd.

Sure FR-4 will meet those conditions. Tg [check the fine SMTnet Archives for discussion on Tg] of FR-4 is 130�F or so. Consider: * Is the delT between Tg and the upper operating [or storage] temperature acceptable for your application? * Do hot spots on the board affect Tg and operating delT between Tg and the upper operating temperature?

All those little numbers that describe the characteristics of different board types and cost affect your decisions to a greater or lesser degree.

Tell us: * What is the impact of temperatures used in production processing steps on your selection of a core material? * What is the cycling rate over the range of temperatures you mention for operation and storage? And how this rate affects the creep of the solder type you expect to use to attach components to the boards you design?

On one hand your seeming naivete appears charming, but on the other it�s a little concerning that someone so seemingly clueless is designing for such a rigorous application. Places to look for guidance are: * Earl Moon, a once frequent contributor [now a lurker] at this forum: - Has forgotten more than most of us will know about board fab and materials selection. [Check some of his old postings for an e-mail address contact.] - Wrote in previous SMTnet Newsletters several articles that introduced various aspects of board fab. Consider revisiting them. - Likely would appreciate someone [anyone, although preferably women] fawning over him about the articles, especially if they had money to pay for his services. * http://www.ipc.org lists wizards and wizettes on various aspects of board fabrication. * Werner Engelmeyer (engelmaier@aol.com) teaches courses in reliable board design. One such course is at APEX this spring. * Consider other design courses at APEX * Consider that there are sites with a greater focus on board design [pcbdmag.com] and fabrication [www.pcfab.com] this one.

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