max FR4 PCB temperature and lifetime

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?

Thanks

Klaus

On May 20, 8:44 am, Klaus Kragelund <klausk...@hotmail.com> wrote:
> 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?
>
> Thanks
>
> Klaus

FR-4 isn't a material as such, more of a qualifier for a bunch of
materials. Get the exact manufacturer and part number and look at
their data.
Isola, Rogers, Getek (or whatever) Nelco, etc all make "FR-4"
materials and all are slightly different chemistries.
Your best bet is to get details and ask the manufacturer rep.

On Wed, 20 May 2009 05:44:42 -0700, Klaus Kragelund wrote:

> 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?

On _any_ PC board?  Including the phenolic stuff you find in clock radios 
that appears to be made out of old trash?

-- 
http://www.wescottdesign.com

On Wed, 20 May 2009 05:44:42 -0700 (PDT), Klaus Kragelund
<klauskvik@hotmail.com> wrote:

>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?
>
>Thanks
>
>Klaus

The functional failure modes of the material application are too
varied and interdependant. To produce a simple temperature chart for
the basic material is pretty meaningless without a specific physical
or chemical property being identified. Specific failure modes are the
subject of study, combined with other environmental factors, like
moisture or impurities. (conductive filament formation, relative
tracking index etc etc) 

You might be better off concentrating on SJ reliability, or assembly
reliability, which is more frequently and more readily evaluated.

Hot boards mean hot components with readily applied mtbf.

RL

Klaus Kragelund wrote:
> 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?
> 

Not graphs. Probably best to contact the mfg of the material. For 
example, page 10 on this datasheet specifies -65C to 150C max for flex 
but I cannot imagine that to be good for the FR-4 parts in there:

http://www.minco.com/uploadedFiles/Products/Flex_Circuits/aa24-flex_design.pdf

For more detailed data things become expensive, problem is you can't a 
priori find out how good a paper or book is unless you have quick access 
to a university library:

http://www.emeraldinsight.com/Insight/viewContentItem.do?contentType=Article&hdAction=lnkhtml&contentId=878282&dType=SUB&history=false

With new packages such as D2PAK and such, these guys recommend 100C but 
state that the FR-4 can be rated as high as 125C:

http://www.ams.de/de/en/file/download/t/download/id/120/

I am going to have a similar challenge soon, heat-sinking DPAKs into the 
board for a unit that is supposed to be used in very hot climates. That 
part of the design won't be fun.

-- 
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Klaus Kragelund wrote:

> 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