Do ceramic disk capacitors go bad when left on a shelf for ~5 years at room temperature?
By "bad," I mean that their capacitance decreases and their ESR increases.

Thanks!

 

Do ceramic disk capacitors go bad when left on a shelf for ~5 years at room temperature?

Ceramic caps are pretty stable, and I would not expect any significant change in their characteristics after 5 years (or more) at room temperature.

 

They used to be wax coated to protect from humidity but it doesn't seem to be the case now. High humidity could be a problem but I've had some for many years that are still within their rated ±20%.

 

Do ceramic disk capacitors go bad when left on a shelf for ~5 years at room temperature?
By "bad," I mean that their capacitance decreases and their ESR increases.

Thanks!

I think ceramic disk capacitors are pretty stable as far as their performance goes. After all, consider how long products that are made with them are expected to last. Lot's of things out there, including life-critical things, that are decades old with no problems. What drives the "shelf life" of many components is not performance degradation, but assembly degradation. If you are running a high-speed, high-volume assembly line, you need the components you use to all behave in a nearly identical fashion during the assembly process. You can't tolerate one batch of capacitors that solder too differently than the next, for instance. So these get characterized and the manufacturers of the components are essentially guaranteeing that as long as the components are stored in such-and-such a way for no longer than this many months, they can be reliably assembled using the same processes and techniques as if they were used immediately the day they were manufactured.

 

Some of mine must have been a bad batch then, resold on ebay as an assortment for beginners.
Thanks!

 

Some of mine must have been a bad batch then, resold on ebay as an assortment for beginners.
Thanks!

There's a good chance that stuff sold on eBay and the like were bad (or at least out of tolerance in some respect) from day one -- that's how the seller got their hands on them really cheap.

 

resold on ebay as an assortment for beginner

I'm convinced that a lot of the components coming out of china were sold as scrap for being off-spec and repackaged by vendors to sell to whoever they could entice to buy them at a cheap price. If you want on-spec components you have to buy from legitimate parts houses. If you're just playing around you can take your chances with eBay, AliX, and their ilk.

 

I recall someone saying that when they were working at an electronics component manufacturer, all the components that did not meet specs were put in a bin labelled for "RS".

 

I'm convinced that a lot of the components coming out of china were sold as scrap for being off-spec and repackaged by vendors to sell to whoever they could entice to buy them at a cheap price. If you want on-spec components you have to buy from legitimate parts houses. If you're just playing around you can take your chances with eBay, AliX, and their ilk.

"Coming out of China..."
There is the stuff we buy via places like alibaba.com, eBay and Lazada, and then there are the authorized distributors, which at least identify the manufacturer!

 

If done right, there's a legitimate place for these parts. By having a buyer for their surplus and reject parts, manufacturers can keep their costs down, which are reflected in the price of in-spec parts. By having a source of much cheaper surplus and rejected parts, experimenters, amateurs, hobbyists, students have a source of affordable parts in low quantities. This market used to be served primarily by electronic surplus stores, which were very common. I remember when I was first getting started there were about a dozen that I quickly learned of in the Denver metro area and I became a very frequent customer of four of them. Two had a sign by the cash register that very clearly announced that most of their parts were from surplus inventories and that no assertion was being made that they met the manufacturer's performance specs. One even had, in big bold letters, the title "Buyer Beware" at the top of the sign. As a broke college student, I certainly couldn't afford to buy in quantities of a thousand from some place like Allied and I couldn't afford the prices that a place like DigiKey charged for single quantities. In addition, most of my work was of the scramble-because-I-need-it-now flavor, so it largely came down to Radio Shack and the surplus houses, but when a 7400 cost $1.19 at Radio Shack within walking distance or $0.14 at Quest Electronics ten miles away, Quest got as much of my business as I could manage. But even though I was fully aware that I was buying surplus parts (though I didn't really understand some of the nuances of what that meant at the time), I don't recall a single part ever failing to function. Now, it wouldn't surprise me if some, perhaps many or even all, of the parts didn't meet spec in some way, but they met my needs perfectly.

Today things are different. Even though surplus houses were selling surplus and rejected parts, they still have motivation to sell parts that could be counted on to at least function reasonably well. If they got a reputation for selling non-functional parts, people went elsewhere. Furthermore, closing shop and reopening a few miles away under a new name in order to get around this wasn't an option -- there weren't THAT many shops and word got around real fast whenever a new one opened or management changed. But today, I can sell total crap -- completely counterfeit parts that are completely non-functional -- through one of these online market places and as soon as I sense that the word is out, I can quickly switch to a completely new company. If I'm really playing the game, I open up multiple stores and sell good parts long enough to build a positive reputation and then start transitioning to junk on some of them. When those tank, I can simply switch to one of the others that has already been selling for months and start selling crap there, knowing that it will take time for inertia to catch up to it, while at the same time setting up a new company and start it out building a good reputation.

 

I've bought a lot of "hobby parts" through AliX and I've learned to do a basic go/no-go test on any chips bought there. ~10-20% fail! I was looking for a specific Op Amp and bought my typical batch of 10 about six times and all failed before I finally got a good batch (I was starting to think it was impossible but I kept hammering away at them). Hardware, tools, resistors, and capacitors are typically good. What you do have to watch out for are kits, especially capacitors in kits being as much as 50% (or more) out of spec. and/or kits of poor design. Not always, but enough to be wary and test. Things have changed in china and their shipping charges from china post have increased to the point that the same device can often be found on Amazon for less. It used to be the other way around. Find something on Amazon and go straight to the source (china) and cut the middleman out (Amazon). Not so much lately. Same can be extrapolated to chinese vendors on eBay but not as bad as on AliX. AliX is good at refunding bad/lost in shipment products but you have to be very patient as international shipping is slow. Seems Congress is starting to realize that the 800USD Customs Tariff point is too high and talking about lowering it again so you will have to pay Tariff on small international orders maybe. Will have to watch and see what they do...

 

I have found that I can "trust" certain sellers on Amazon and AliExpress. I've gotten few or no bad parts from them (e.g.: one otherwise reputable (in my experience) Amazon seller, uxcell, sold me "UV" LEDs that produced no UV I could detect and almost no light of any kind).

The short list of suppliers I use have cost me almost nothing in bad buys. I tend to buy ~$10 at a time on any given order. This is part of a strategy to silo possible losses, and also to optimize shipping costs. Overall, I have been very happy with the parts I have purchased.

That said, I also buy from Newark, Mouser, and Allied(/RS) when I have a need for a particular part (such as a replacement component) or a critical need for a particular value such as a precision resistor or the like.

As an aside, the "official store" for a lot of Chinese brands is actually on AliExpress, so for products like Esspresif dev boards, or Heltec LoRa boards, the better price on AliExpress (usually) is not a risk, just a delay.

 

How is the TS defining "Bad"??? What usually suffers from long term storage is the solderability of the leads. So what aspect of the capacitors no longer is in spec?? And is the TS certain that the devices are not thermistors or MOVs?? How are you measuring the capacitance? And what is the claimed working voltage?? The capacitance measuring scheme of cheap multi-meters is not often very accurate.

 

How is the TS defining "Bad"???

The original post:

Do ceramic disk capacitors go bad when left on a shelf for ~5 years at room temperature?
By "bad," I mean that their capacitance decreases and their ESR increases.

Thanks!

 

And I asked how they were measuring and what the specs were. And a good point is also made that said devices may never have been in spec. And I have seen parts with +20%/-80%tolerance, I think I recall.

 

"`Bad` is an objective word, until you use it when posting online." -- Me

And is the TS certain that the devices are not thermistors or MOVs??

They're sold as capacitors, they're labeled as capacitors, they look like capacitors, I think that they're capacitors. But for all I know, they could be alien technology that was misdirected from the state department to my door.

How are you measuring the capacitance?

With an LCR meter...You should know better than to post messages like this in reply to me. I enjoy typing up stupid/funny replies like this.

And what is the claimed working voltage??

50v

The capacitance measuring scheme of cheap multi-meters is not often very accurate.

Yes, you first have to take into account the accuracy of your test equipment. But first you have to calibrate it.

And I asked how they were measuring and what the specs were. And a good point is also made that said devices may never have been in spec. And I have seen parts with +20%/-80%tolerance, I think I recall.

I expected them to all be within +/- 20% tolerance. That's rather normal for passive parts, from what I've read.

Now that being said, I don't expect them to be ~45% out of spec for capacitance (104 capacitor). Also, ceramic caps supposedly have much lower ESR than electrolytic...
Mind, this result is in Ohms!

 

OK, this IS NOT one of those cheap multi-meters. So it is believable. Good!
But items sold on line may not always be "as described."
The spread of measured values may reveal if the bunch is simply out of tolerance rejects, or just assorted values mislabeled. Both happen sometimes.