Question about fried capacitors

[ChaoticKinesis]

I've seen some mention of the need to be careful when soldering capacitors so as not to fry them and was wondering how much heat is too much. Also, in the case that a capacitor is fried, does it just lose its capacitance or will it no longer pass a signal?

[m1ke323]

I am also interested in knowing if a fried cap will pass a signal or just lose it's capacitance.

Mike

[joecarrow]

It depends on the capacitor composition.

I know, for example, that tantalum capacitors tend to fail as a dead short. This sucks when you're using low ESL tantalums as a power supply bypass.

Electrolytic capacitors usually make some noise and have something come out of them when they fail- and I think it's a reduced capacitance, but I'm not sure.

I killed a tiny mylar cap once, and I believe it failed as an open circuit. I don't really remember, it was a long time ago.

A lot of capacitors are rated for use in modern manufacturing processes that involve getting a dip of solder, or passing through an oven for a short period of time. The key that you don't want to hold them at an elevated temperature for longer than you need to.

A high-power high-temperature soldering iron is actually good for preventing component damage because it can allow you to quickly heat up just the area of the solder joint, allowing you to spend less time heating up the component. If you have a wimpy soldering iron that you have to hold in contact for a long time before the solder will melt, that's when you'll really overheat your components and board.

[joetama]

Well too much heat on any part is not good. I would say not to lower the temp but to solder faster. If you lower the temp it takes longer for the solder to melt correctly to bond so there would be more heat over time. If that makes sense (does to me). If it's "fried" it could either lose it's rated capacitance or just stop passing signal all together...

[TacoD]

MKP caps, frequently used in loudspeaker x-overs, can take a lot of heat in my experience. I solder @ 380 Celsius and I have never broken a single capicitor (and I have soldered a couple of hundred of these things).

The only thing what hapens to me with caps, are broken leads. I reuse a lot of caps, and after 20x bending the leads they will break.

[ThomasW]

What happens depends on whether you want 'regular' or 'extra-crispy'... :B

[ChaoticKinesis]

Can I have that with some hot sauce on the side please? :P

[dynamowhum]

Hey it seems the fried stuff is bad for other things besides the old ticker.

[Amphiprion]

Cap leads tend to be small, you won't have a problem unless you're soldering them to a junction with multiple large gauge wires. If you can touch the lead right where it enters the cap and it's hot, stop. Let it cool and try again.

FWIW, a guy at my work does his reflow soldering in our toaster oven. I don't think he's lost a component yet doing it that way. Makes me wonder about how sensitive we think things are in the hobbyist world

[ChaoticKinesis]

While soldering, the leads did get quite hot from a few seconds of contact with the iron but not hot enough to burn me from touching them. That's not to say that I would be comfortable keeping my fingers there for long, but my guess is the temperature was not higher than 60 Celsius.

Does the voltage rating on the caps correspond in any way to the temperature they can withstand?

[JonW]

I was also wondering if I was frying my caps when I was soldering up my first crossover. I'm new to soldering, so I doubt my technique was too good. I imagine that the caps got quite hot- especially when connecting to larger parts. Probably too hot to touch, but I didn't try. When it was all done, I used a voltmeter to test the crossover and everything worked well. Which isn't to say the caps aren't now off somewhat.

[Arneson]

If your soldering to freestanding component legs a simple alligator can be clipped upside of the iron to take the heat. If not just be as fast as possible at a good hot temp. and with good 40/60 rosin core solder.
Last night I recapped a motherboard and have the burned finger to prove it.
Interesting that the crossovers in the old days were post wire wrapped, a different connection technique.