Capacitors issue ?

[catalin gramada]

Hello.
Bought from Mouser 8 pcs. KEMET 470uF/450v. When opened the pack found two of them are shaking and rattling inside the shell. I consider this sort of mechanical problem unacceptable and intend to return. But just as information , what can be the cause of this type of fault, please? The shell have not signs of mechanical shocks to suppose someone dropped to the floor , or some. These are first capacitors I saw rattling and was happened to be fresh new ones. Why ? I add a pic in attach. Thanks.

[Chuck H]

It's pretty common for modern can caps to be assembled from smaller caps simply wired up and stuffed into the can. Sometimes it's just the wax coated cap innards and sometimes it's actually already made caps in their cases and everything just jammed in there. Newer caps are smaller than older caps so this is possible and practical for making the multi cans in sized typical of where they'll be used. I expect this is the case. But I agree about loose/floating parts inside the can being a possible mechanical issue. It's probably not. I'd bet everything is fine. but I wouldn't like it either. They could have at least stuffed something in there to take up the extra space, right?

[catalin gramada]

I don't think they are fake. They comes with a conformity certificate from Mouser which attest there are original parts. It is very tempting to open one to see what happen inside, but at almost 25$ per piece I prefer to return it. Now I just thinking...all 8 ordered caps are from the same lot. Is just a matter two exhibits this problem or is a quality problem with the whole lot ...🤔 ?

[Jon Snell]

We got the odd capacitor that rattled when I worked for Daly Condensers in the UK. It was because the pitch filler missed them and were rejected, however there was nothing wrong with them electrically as they passed all of the tests, they only got rejected when a human intervened at the end of production.
Personally I would reject them as well.

'Pitch filler' is the machine that filled the can with pitch/filler as they were being stuffed with the electrolytic.

[Mick Bailey]

Can caps usually conform to standard form factor sizing. Because of improved cap manufacturing (meaning smaller caps for a given rating and value) and the need to maintain external sizing, there's sometimes quite a bit of empty space between the internal cap assembly and the can. Sometimes a plastic spacer is used to centre and locate the cap. Maybe this is a little loose in the cans that rattle. You can feel really cheated when you open up a can and there's a smaller cap inside but that's the way it is with shrinking component sizes. Just think how big that can looks compared to some radial caps of the same value/voltage and maybe even lower ESR and better temperature rating.

[catalin gramada]

If take a look at datasheet ,for any producer, will see they use standard sized shells for diferent capacitors value and voltages. Seems very improbable for a standard shell to fit perfectly all caps related in dimensional range. Think the electrolyte stabilize mechanical inside, as should suppose it do little pressure inside during the working cycle, by heating. And should be enough, with one condition...to not forgot to fill in.
I wonder how there is not a factory machine to test caps for mechanical issues. Guess nobody do a quality controll in any factory by hand nowadays...

[Chuck H]

FWIW not all electrolytics actually use a filler. I know that Sprague Atom's sure don't. All of them I've cut open were a small cap in a bigger can. There are others that do this too but here are some images of Atom caps I found on line.

[Helmholtz]

You could try to contact Kemet and ask if it's a quality issue:
https://go.kemet.com/contact-us

[Chuck H]

You could try to contact Kemet and ask if it's a quality issue:
https://go.kemet.com/contact-us

Best advice so far ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[catalin gramada]

Best advice so far ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Was done from Monday when received the pack . Get No answer.��

[catalin gramada]

Good news as Mouser agreed for replace without any comments. Those faulty caps remains at me so I.ll have the opportunity to open it to see what the heck is going inside. No excuses for Kemet as they put at sale capacitors which should be rejected from production. They looks very suspect which reveal the sale policy and have no doubt they are original in conformity with quality certificate I received. They are not printed but have a stickers instead meant they can keep it stock and put on sale with any data they want. On the stickers is marked "made in EU" which meant nothing as time cannot identify by what standard quality they are made: they are for Bulgarian market or for Sweeden market?...which is not same thing as nowadays nobody craft for specifications but for the price instead. This meant you can have the same product but for different price you asked to be made. Same product, different qualities. This meant European unique market by principles...Lot of shit throwing around cause nothing meant competitions and performances but agreements instead.

[Jon Snell]

If you test them, I expect they will be well within the specification. As I wrote earlier, the production line omitted the filler.