what makes a part "automotive"?

[slowpogo]

Both Mouser and Digikey have an "application" column for parts. The most common applications I see are "general purpose" and "automotive."

Which raises the question: what makes a part suited for "automotive" use? Oftentimes parts have basically identical characteristics except one is designated "general" and the other "automotive" and I've always wondered why.

 

[benny_profane]

Essentially, it's guaranteed reliable performance over a wider temperature range. Check out the AEC-Q200 standards for more information.

 

[slowpogo]

Essentially, it's guaranteed reliable performance over a wider temperature range. Check out the AEC-Q200 standards for more information.

I see. That seems not especially relevant to guitar pedals. But possibly useful for tube amps or other audio gear that gets hot?

 

[benny_profane]

General use capacitors are typically rated for 0 - 70ºC. The least rigorous automotive grade temperature range is -40 - 85ºC; the most rigorous is -50 - 150ºC. I don't think a capacitor should be nearing the general purpose extreme when good design practices are followed. The caps should be isolated from anything emitting excess heat.

 

[Alan W]

I’m pretty sure that a main differentiator for Automotive rating is stress and vibration resistace, along with the wider temperature range.

 

[benny_profane]

I’m pretty sure that a main differentiator for Automotive rating is stress and vibration resistace, along with the wider temperature range.

Temperature range defines the buckets. Mechanical stress (including g-force testing and vibration), moisture and solvent resistance, solderability, and part integrity are all part of the test for each temperature qualification.

There’s also installation/layout aspects of the evaluation that look at leads and flex.

So yes, anything with an AEC-Q200 qualification has undergone mechanical, moisture, etc. evaluations. The differentiation for each category is the temperature rating as the other tests are consistent.

 

[RetiredUnit1]

Tubes are powered by heaters. If you heat metal in a vacuum electrons are released. The signal attracts those electrons and when they hit a grid in synch with the signal amplification is born. Put those suckers in a 3/4" thick birch box and pump 100watts out to a speaker and you're talking a squatload of heat. For this reason it's a bit difficult to isolate the electrolytic capacitors which need to be as far as possible from the preamp.

It's not just the heat rating in degrees it's how LONG they'll take that. Cars are pretty hot too. Especially going up the grapevine in SoCal on a 120f day. I've seen more than a few cars pulled over on that stretch.

Sorry for the rambling post, my recent covid brain fog is still manifesting itself.....

 

[HamishR]

And here's dumb ol' me thinking that a part meant for automotive use just went faster.