any reason to NOT replace surface mount electrolytic caps with tantalum? - Page 1
Forum section: electronics / beginners

author: Dave928
author_rank: Newbie
timestamp: February 27, 2025, 02:25:41 am
content: i'm starting a project of recapping several old Macs, from a 1984 128k to a 2013 Mac Pro. the older ones need it to fix leaks, the newer ones work fine, so it's more "future proofing" than repair. i assume this would apply to PCs too.my question is, is there any circumstance where a surface mount aluminum electrolytic cap should NOT be replaced with a Tantalum cap or solid polymer can type, either on the logic boards, power supplys or the RAM cards from a functional standpoint? as in, the function of a circuit requires electrolytic, or it just won't work right? or can i just replace them all? i know the "thing" right now is to use solid tants, but i like the idea of the aluminum can solid polymer caps to retain the look of the original electrolytics.thanks

author: daisizhou
author_rank: Super Contributor
timestamp: February 27, 2025, 03:26:30 am
content: Electrolytic capacitors are more stable and reliable.Except for poor quality electrolytic capacitors.Solid polymer capacitors are expensive and difficult to buy on the market.I usually choose tantalum capacitors with a voltage rating higher than 3 times the withstand voltage.For some special circuits I will not consider it, such as: power supply part,Because it has a high failure rate, short lifespan, and is unreliable

author: Whales
author_rank: Super Contributor
timestamp: February 27, 2025, 07:28:02 am
content: Quote from: Dave928 on February 27, 2025, 02:25:41 amThat's a popular thing to do now? Eww.Tantalums are great until they fail. Then they're revolting disgusting smelling things that make you evacuate your house. They are really,reallybad, trust me. Like fumigation-product bad.Electrolytics fail much more gracefully. Heat causes them to slowly loose capacity and gain ESR. In many devices this means they become marginal to turn on, but still work fine if you heat them up a bit first.In both cases you can choose higher quality & specced parts to avoid the failure modes, but I'd still want to more graceful option on top of that(EDIT: Of your two stated options) I'd definitely go with the solid polymer caps, BUT, be warned that some voltage regulators (eg anything with 1117 in the name) might stop working. They need crappy high-ESR caps to be stable. You might only see this problem at low load, or you might not.

author: benj38
author_rank: Frequent Contributor
timestamp: February 27, 2025, 07:39:58 am
content: Quote from: Dave928 on February 27, 2025, 02:25:41 amIt may be the "thing" in some circles, but not among electronics engineers

author: Kleinstein
author_rank: Super Contributor
timestamp: February 27, 2025, 08:20:33 am
content: Tantalum capacitors should not be used with a powerfull supply rail, that can deliver more than some 2 A. So a 78xx regulator is usually still just OK if there is not much capacitance in parallel. The problem is that they fail short and too powerfull a supply can make them burn from the inside quite violently in a kind of thermite reaction. I have seen a 5 mm size hole in FR4 from a failed tantalum capacitor.So there is a big no to using them in some positions.Polymer capacitors should be OK in most cases. However some voltage regulators (especially older low drop ones) don't like the very low ESR a the output.

author: squadchannel
author_rank: Frequent Contributor
timestamp: February 27, 2025, 09:08:11 am
content: There is no need to use polymers for a 128K Mac.Use low ESR 105℃ capacitors.Tantalum is very hard to deal with when it fails.So I have replacing with polymer and hybrid capacitors, but I use ceramic NP0/C0G for RC timing capacitors and other capacitors with small capacitance.To begin with, polymer capacitors don't have that high withstand voltage, and they don't use often. especially if they are CRTs. and EXPENSIVE.Never use capacitors made in china.Buy from a reputable distributor(Digi-key, Mouser, RS etc...).DONT using capacitors from Amazon or chinese cap kits(sets). Those are for prototyping.if you are confused about brands, go with Nichicon or Chemi-con(nippon chemi-con/united chemi-con).I love Nichicon so much that I seldom use capacitors other than Nichicon.

author: Amper
author_rank: Frequent Contributor
timestamp: February 27, 2025, 10:08:52 am
content: One thing to consider is that "better" is not always better. Old caps can have normal or higher ESR, replacing them with low ESR or even ceramics that are available today can make stuff oscillate or ring that was previously dampened by the ESR. Also inrush currents can go up enough to blow fuses and damage stuff.For electrolytics just try to get something similar, buy from a reputable source (as said, not ali, amazon or some shop that has them lay in the box for two decades) and get ones with long life at high temperature. Tont buy 85°C types, go for 105 and something >10k h.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: February 27, 2025, 11:00:09 am
content: As others have mentioned, use reputable brand 105 degree electrolytic caps. It helps if you have an ESR meter to check the old caps, over a few years at high temperatures the original capacitors may have increased their ESR values to the point of not being as effective. There is no need to pick low ESR types as the original ones were probably just plain vanilla types.I have bad memories of hunting down failed tantalum capacitors that failed short circuit. Maybe modern ones are more reliable, but in older equipment they were a common failure.This manual for the Peak Instruments ESR meter has a table showing typical ESR values for a range of capacitors:http://www.peakelec.co.uk/downloads/esr70-user-guide-en.pdfSJ

author: squadchannel
author_rank: Frequent Contributor
timestamp: February 27, 2025, 11:09:22 am
content: The only tantalum I trust is the hermetically sealed sprague tantalum used in the old TE.

author: Dave928
author_rank: Newbie
timestamp: February 28, 2025, 12:04:37 am
content: Quote from: benj38 on February 27, 2025, 07:39:58 amhobbyists, mostly.

author: Dave928
author_rank: Newbie
timestamp: February 28, 2025, 12:16:16 am
content: Quote from: Solder_Junkie on February 27, 2025, 11:00:09 amin my situation there is no need to check them, they've mostly already burst (30-40 years old) and leaked on the boards. the ones that haven't are the same age so i'll just replace them en masse, along with performing some minor trace repair.

author: Dave928
author_rank: Newbie
timestamp: February 28, 2025, 12:17:35 am
content: thank you everyone for the input. helps to narrow down where to go with this.

author: David Hess
author_rank: Super Contributor
timestamp: February 28, 2025, 05:19:54 am
content: There is no reason aluminum electrolytic capacitors cannot be replaced with solid tantalums except where surge current is unlimited, like with input capacitors. To get equivalent impedance, the capacitance can be reduced to 25%. To prevent surge related failures, solid tantalum voltage ratings should be derated to at least 2/3rds, or even 1/2, so use 10 volt capacitors on 5 volt supplies.

author: amyk
author_rank: Super Contributor
timestamp: February 28, 2025, 06:21:56 am
content: Quote from: squadchannel on February 27, 2025, 11:09:22 amYes, the "wet tants", ridiculously expensive but also extremely reliable. Found in mostly military/aerospace now and otherwise extinct.

author: David Hess
author_rank: Super Contributor
timestamp: February 28, 2025, 12:02:13 pm
content: Quote from: amyk on February 28, 2025, 06:21:56 amIt is not just the sealed wet tantalum capacitors. The dry tantalums which use a similar packaging are also very reliable because strain is isolated from the pellet.

author: coppice
author_rank: Super Contributor
timestamp: February 28, 2025, 12:10:32 pm
content: Quote from: Kleinstein on February 27, 2025, 08:20:33 amActually tantalum capacitors should not be used with a lower power rail. Many tantalums just shouldn't be used at all, as they are unreliable. However, the sealed wet ones can be extremely reliable and long life. However they all grow dendrites, which short across the plates. A big power supply will fuse them in a way that, with an otherwise reliable tantalum capacitor, usually just makes the product hiccup and require a reset. With a low power supply they short out, stay shorted, and the product is dead.

author: CaptainBucko
author_rank: Regular Contributor
timestamp: March 09, 2025, 10:15:06 am
content: Leaded resin dipped Tantalum’s do have a bad reliability history, but Kemet, AVX, Panasonic Tantalum’s are about as good as it gets. I recently disassembled a power supply project to fix an error I made with the pcb and grounding a terminal. I then spotted a 10u 10v SMT kemet Tantalum installed on the output of a +12v supply. It had been successfully working for 20 years in a crappy environmental area. Lucky or the result of a quality manufacturer ? Who knows, but I use them all the time.

author: Zero999
author_rank: Super Contributor
timestamp: March 09, 2025, 10:29:40 am
content: Solid tantalum capacitors have a bad reputation, but can be more reliable than aluminium capacitors. They don't dry out. Problems occur when they're run at high temperatures, voltages and currents (ripple & surge).

author: mtwieg
author_rank: Frequent Contributor
timestamp: March 09, 2025, 03:49:46 pm
content: Quote from: Dave928 on February 27, 2025, 02:25:41 amNews to me.AFAIK the major motivator for using tantalum (solid tantalum, at least) is when you need energy density much higher than what MLCCs or Electrolytics can offer (but don't need super low ESR). Recently the energy density of MLCCs has improved to close that gap somewhat. Polymer electrolytics now have much lower ESR than normal electrolytics. And higher switching frequency DC-DC converters (with higher control bandwidth) have reduced the necessary bulk capacitance on supply rails. So the niche for tantalum caps has shrunk considerably. Meanwhile their bad reputation regarding reliability and failure modes has persisted (not going to comment on whether the reputation is well founded).If you are recapping boards, you certainly have enough space available for electrolytics. I see zero reason to switch to tantalums.

author: David Hess
author_rank: Super Contributor
timestamp: March 09, 2025, 05:15:45 pm
content: Quote from: mtwieg on March 09, 2025, 03:49:46 pmFor a given capacitance, common solid tantalum capacitors have a lower impedance than even low impedance aluminum electrolytic capacitors, and the difference is greater at higher frequencies, so a lower capacitance solid tantalum capacitor may be used for the same impedance, but the cost is still be greater. A larger low impedance aluminum electrolytic capacitor has a lower impedance than the solid tantalum capacitor for the same price.I was recently doing price comparisons to replace 15 microfarad solid tantalum capacitors with low impedance modern parts. Low impedance aluminum electrolytic capacitors were the least expensive to achieve the same or better impedance, but required a lot more capacitance. Polymer aluminum electrolytic and polymer solid tantalum parts were significantly more expensive. So I elected to use much higher capacitance low impedance aluminum electrolytics with 1 microfarad ceramic capacitors in parallel.

author: u666sa
author_rank: Frequent Contributor
timestamp: March 09, 2025, 05:36:07 pm
content: Tantalum caps also fail. Common occurance in laptops. The thing boots up, and then freezes right before windows logon screen. That's them.

author: mtwieg
author_rank: Frequent Contributor
timestamp: March 10, 2025, 01:10:08 pm
content: Quote from: David Hess on March 09, 2025, 05:15:45 pmIn general I agree if but only if we don't consider polymer electrolytic caps. Not sure what you mean by "low impedance" aluminum electrolytic capacitors.It's pretty messy to compare tantalum vs polymer electrolytic. IME if you restrict yourself to the "chip" style packages then tantalum compares much better. But if you allow for radial packages then polymer aluminum wins every time.

author: David Hess
author_rank: Super Contributor
timestamp: March 10, 2025, 08:31:49 pm
content: Quote from: mtwieg on March 10, 2025, 01:10:08 pmI mean aluminum electrolytic capacitors designed for high ripple current applications which have a lower impedance than generic or low leakage aluminum electrolytic capacitors, like the Panasonic FR, or Chemi-Con KZN series.QuoteThe polymer aluminum electrolytic and polymer solid tantalum are better, however I found that at least for radial packages, they cost even more. They make more sense in high ripple current applications where a suitable low impedance aluminum electrolytic becomes both large and more expensive to support the needed ripple current.

author: CaptainBucko
author_rank: Regular Contributor
timestamp: March 12, 2025, 04:25:52 am
content: Quote from: u666sa on March 09, 2025, 05:36:07 pmNot disagreeing with you, but 75% of all laptop repair videos I watch on you tube have their root cause involving a ceramic capacitor of some sort.

author: DavidAlfa
author_rank: Super Contributor
timestamp: March 12, 2025, 04:37:26 am
content: Use solid (polymer) eletrolytics, best of all, they don't leak, they don't explode, while retaining the looks you're after.A bit more expensive but not that much.

author: Terry Bites
author_rank: Super Contributor
timestamp: March 12, 2025, 12:29:23 pm
content: Tantalum... tantrums more like. Short lives.They die short and catch fire. I avoid them at all cost now.