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Peak Temperature

Views: 1492

df

#44595

Peak Temperature | 18 October, 2006

Hi all,

If a component is rated as Peak Temperature 225 DegC. Is there a safety factor built into this rating or is it exact?

df...

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#44597

Peak Temperature | 18 October, 2006

I thought that it was a worse case scenario. This is when you first get failure but most components will withstand greater temps. What are these temps? Who knows.

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Rob

#44602

Peak Temperature | 19 October, 2006

It's the max you can put them through before you can expect failures. However some suppliers - particularly the Japanese have a higher safety window.

IS it a through hole part you looking at intrusively reflowing?

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#44603

Peak Temperature | 19 October, 2006

Time is also a factor, usually. IIRC almost everytime I"ve seen a max temp rating it also included time. ex. 225C for 20 seconds.

If a part can take 300C but the spec sheet says 220C and you take it to 225C, it doesn't matter if the heat made the part fail as far as liability goes.

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df

#44604

Peak Temperature | 19 October, 2006

thanks for replies guys.

I have a nearly Full RoHS Compliant bom with 1 device non-rohs.

It is a soj28 device rated ( as best as I can find out at 225degC)

Production are screaming for these boards - I put a thermocouple on the part and it hits 235 max .

I am just wondering what if any tolerances there are in the Peak Temp. I have built 10 and sent to test!

At what stage would the part fail - if heat was an issue would you expect it to fail straight away...

df..

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#44609

Peak Temperature | 19 October, 2006

If you're talking about practical application who knows? If you're talking about liability I think you're going to lose.

Most of the parts that I've had to look closely at had a peak AND a "time at" maximum. If they spec. 220 as the peak and you exceed it you're asking for trouble.

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#44610

Peak Temperature | 19 October, 2006

Don't confuse ROHS compliant with "able to take higher temps". In fact I think some parts lost some heat tolerance when they went ROHS compliant. Don't forget that some fire retardants are on the banned list.

I do know that before we even heard of ROHS I saw lots of heat tolerance data on spec sheets then after that info seemed to disappear.

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#44628

Peak Temperature | 19 October, 2006

I agree with Stephen there! Or maybe we just didn't care enough about looking into it in the COLD profile days! Back to df: I don't think any manufacturer is going to give you a tolerance level, they'll stick with what they've told you -225. If it's any consolation I've been running an SnPb profile for ten years on some products with a peak of 240. The SOP, SOJ style components are hitting around 235. No probs. I wouldn't be surprised if a lot of people are running leaded profiles with these sorts of peaks. I reckon 215-225 would be the exception rather than the rule on any board that has more than jellybeans on it.

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