What's your technique for fitting caps?

[big10p]

I've just read an interesting discussion about what technique should be used when fitting electrolytic caps. It says the leads should never be bent apart (not even slightly), as this will damage the seals and likely cause leakage. Instead, two 90 degree bends should be made in each lead to fit the through hole spacing. It also discussed how too long soldering time can damage them, and whether caps should be fitted flush to the PCB or not.

Interested to know what the experienced (and less experienced, like myself) techs here have to say on the matter.

big10p2022-02-12 13:03:58

 

[Monstermug]

Flushed to avoid getting knocked over. It looks so much nicer too. If it doesnt fit order one that does or 90 degrees bends if your feeling lazy. If its out by a little bit then spread them but they wont sit flushed. Use high quality high temp caps and occasionally higher voltages for problematic caps.. Panasonic, nics, etc

 

[big10p]

Flushed to avoid getting knocked over. It looks so much nicer too. If it doesnt fit order one that does or 90 degrees bends if your feeling lazy. If its out by a little bit then spread them but they wont sit flushed. Use high quality high temp caps and occasionally higher voltages for problematic caps.. Panasonic, nics, etc

So you try to fit all size caps tight flush to the board, not just the physically bigger ones? The article I was reading was saying this might be bad, as the leads heat up and expand when being soldered, then contract when cooled down, putting stress on the leads/seals. Also, if the caps are in an environment that gets hot, this stress is constantly being applied as the device is switched on/off.

Not sure if this is significant myself, which is why I'm keen to hear other points of view. TBH, I haven't given much thought to bending the leads to fit, but will probably be more wary of it in the future.

big10p2022-02-12 15:41:11

 

[John Bennett]

I try to measure the spacing and order the correct lead spacing.
But it’s an arcade PCB, not a passenger airliner, I wouldn’t stress about a half a millimetre bend on the odd capacitor.

 

[big10p]

I try to measure the spacing and order the correct lead spacing.
But it’s an arcade PCB, not a passenger airliner, I wouldn’t stress about a half a millimetre bend on the odd capacitor.

Of course, but I'd still like to do things the right way, especially as it costs nothing. I've pretty much made caps do the splits before, in the past.

 

[John Bennett]

I didn't mean to sound dismissive there - it's just always a matter of how far you choose to go.
They do have plastic bases, and I'd be suprised if you bent a 2.5mm cap to fit a 3mm spacing and it pissed it's guts out within a decade as a result.

I wouldn't batter things flush that don't fit though, and I'd probably go back to Farnell and order another cap if I had a 5mm cap and an 8mm spacing, rather than make it do the splits and sit proud of the board waiting to be smashed off.

Can't see how you'd do 90 degree bends on the legs without putting force on the cap either.

 

[RaveN]

Heat and high voltages cause capacitors to fail. It is important to not apply the soldering iron for too long (but why would you need to?) One benefit of repairing older equipment is that an old 16v 47uF cap may now have the same lead spacing as a modern 50v 47uF cap, so we install that instead, preferably with one that's by a decent manufacturer rated at say 105oC @ 3000hours, and we know that's going to last probably until the end of our lifetimes regardless of how it sits on the pcb (unless there's a manufacturing fault).

Another potential issue, and not always thought about, is when replacing capacitors in certain circuits (like the PSU), where the ripple current and impedance are important. If a capacitor isn't rated for a particular ripple current, it again will fail much sooner. Also, whilst I personally will increase uF ratings in things like smoothing capacitors, there's also the risk of damaging other components whilst the caps act as a short circuit for a short while when power is first applied.

I've bent capacitor legs all over the place in the past, but I've never had one leak on me, and I'm talking about things I still own that I worked on 25 years ago.

 

[big10p]

Thanks all for the input. It's interesting to hear people's views. Also interesting to hear that replacing a cap with one that has a much higher voltage rating is OK? I did read in the same discussion that using a 'one size fits all' for voltage isn't a good idea, and that we should go for one closer to the original e.g. use a 25v cap to replace an old 16v.

Anyway, I've probably been overthinking the issue by the sounds of it, so will probably carry on in the same manner as before.