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Re: max FR4 PCB temperature and lifetime

E

Eeyore

Jan 1, 1970
0
Klaus said:
Hi

UL has a rule for maximum temperature on a PCB at 105 degrees C.

Standard FR4 can handle 130 degrees, and normally I have used 95
degrees as a maximum to have long lifetime of the PCB (discolouration
and delamination of the FR4)

I have tried to find a graph of lifetime versus PCB temperature, but
to no end. Have any of you ever seen one?

If it helps any, I designed an audio amp once with a PCB made out of that
white 'part synthetic' stuff CEM( not sure which grade )
http://en.wikipedia.org/wiki/Composite_Epoxy_Material. It was partly in
contact with a heatsink ( over some area ) that could reach 120C. We had
no problems with it and I've seen units that are 10 years old.

http://norplex-micarta.com/products/category-detail.php?page=31

"Epoxy Resin - Glass Fabric Substrates

Consisting of electrical grade epoxy resin systems combined with a
variety of glass fabric substrates, these products come in low and high
temperature versions. Low temperature thermoset epoxy/glass materials
offer good chemical resistance and electrical properties under dry and
humid conditions. Some systems are flame retardant and meet the
Underwriters Laboratories Flammability Class, V-0. They also feature high
flexural, impact, and bond strength at temperatures up to 130°C. These
fiberglass composite materials are suitable for a variety of structural,
electronic, and electrical applications.

High temperature fiberglass epoxy resin systems offer superior mechanical
strength and insulative properties over a wider temperature range. These
products feature high mechanical strength at continuous operating
temperatures up to 180°C in mechanical applications. In response to
customer requests, Norplex-Micarta can change the resins to enable
products to withstand even higher continuous operating temperatures.
Several standard grades can handle temperatures much higher than 180°C
for short periods of time. At elevated temperatures up to 155°C, epoxy
composites retain at least 50 percent of their room temperature flexural
strength. Several types meet NEMA G-11 requirements, and the materials
can also be produced on any glass style for applications that do not
require NEMA G-11. Applications include solder pallets, corona
dissipation, rotor slot cell insulation, and structural applications at
elevated temperatures."

Graham
 
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