/ News & Press / Video / What are Aluminum Polymer Capacitors -- KEMET and Mouser Electronics
What are Aluminum Polymer Capacitors -- KEMET and Mouser Electronics
WEBVTT Kind: captions Language: en
00:00:04.990 [Music] 00:00:17.93000:00:17.940 hey we need to talk about capacitors yep 00:00:21.89000:00:21.900 I know what you're thinking if engineers 00:00:24.23000:00:24.240 were chefs capacitors would be salt 00:00:26.90000:00:26.910 never the star of the show you never 00:00:29.81000:00:29.820 know exactly how much you're going to 00:00:32.21000:00:32.220 need we all just kind of sprinkle them 00:00:34.85000:00:34.860 on to our design until it tastes about 00:00:38.03000:00:38.040 right hmm 00:00:40.84000:00:40.850 needs more capacitors but there's a lot 00:00:45.08000:00:45.090 more to choosing the best capacitor than 00:00:47.47900:00:47.489 just grabbing a shaker full of 00:00:48.92000:00:48.930 electrolytic sand sprinkle them artfully 00:00:51.22900:00:51.239 around your PCB hmm pinch more there hi 00:00:56.06000:00:56.070 I'm Amelia Dalton host of chalk talk it 00:00:59.11900:00:59.129 turns out that choosing the right kind 00:01:01.25000:01:01.260 of capacitor can have important 00:01:03.74000:01:03.750 implications for your design in 00:01:05.93000:01:05.940 reliability longevity cost board size my 00:01:11.02900:01:11.039 guest today is James Lewis from Kemet 00:01:13.60900:01:13.619 and we're gonna dive into some 00:01:15.20000:01:15.210 fascinating discussion of capacitors 00:01:17.85900:01:17.869 including some super cool new organic 00:01:21.32000:01:21.330 polymer aluminum hmm what's all this 00:01:25.46000:01:25.470 about let's find out and before we get 00:01:29.08900:01:29.099 started don't forget to click that link 00:01:31.04000:01:31.050 there you can find out more information 00:01:33.13900:01:33.149 about capacitors from Kemet hi James 00:01:37.07000:01:37.080 thank you so much for joining me today 00:01:39.19900:01:39.209 thanks Melia I'm looking forward to our 00:01:41.24000:01:41.250 discussion about a certain kind of 00:01:42.88900:01:42.899 capacitor okay so my relationship with 00:01:45.55900:01:45.569 capacitors is mainly things like 00:01:47.77900:01:47.789 decoupling of course and working in 00:01:50.83900:01:50.849 power and filtering parts of my design 00:01:53.41900:01:53.429 now I've heard of aluminum electrolytic 00:01:56.97900:01:56.989 capacitors but what are these organic 00:02:00.30900:02:00.319 aluminum capacitors I've heard about and 00:02:03.44000:02:03.450 and are they in that expensive section 00:02:06.49900:02:06.509 of the grocery store no no they're just 00:02:11.66000:02:11.670 a different type of aluminum 00:02:13.10000:02:13.110 electrolytic capacitor okay then why 00:02:15.94900:02:15.959 don't we talk about the difference 00:02:17.90000:02:17.910 between organic and traditional aluminum 00:02:21.19900:02:21.209 all right let's start by talking about 00:02:23.18000:02:23.190 what's inside of a traditional aluminum 00:02:25.22000:02:25.230 and then we'll get to these polymer 00:02:26.63000:02:26.640 stuff in a few minutes so if we look at 00:02:28.88000:02:28.890 this picture I've got a can 00:02:31.05900:02:31.069 that we've kind of exploded out a little 00:02:32.55900:02:32.569 bit and there's two key things inside 00:02:34.89900:02:34.909 the can there's the anode foil and the 00:02:36.81900:02:36.829 cathode foil and so these are actually 00:02:38.25900:02:38.269 the electrode plates that provide our 00:02:40.92900:02:40.939 positive and negative connection to the 00:02:42.55000:02:42.560 capacitor in between them is a separator 00:02:45.61000:02:45.620 paper which as you might imagine from 00:02:47.92000:02:47.930 the name separates the two plates from 00:02:49.69000:02:49.700 each other so that we don't have direct 00:02:51.03900:02:51.049 contact and then within those foils in 00:02:53.89000:02:53.900 that roll of paper we have foil tabs 00:02:56.08000:02:56.090 that are connected into them and that's 00:02:57.78900:02:57.799 what actually provides the actual 00:02:59.02000:02:59.030 terminal connection so I notice there's 00:03:01.56900:03:01.579 no electrolyte in this electrolytic 00:03:04.70900:03:04.719 capacitor at least on this page at least 00:03:08.19900:03:08.209 so where is this electrolyte hiding it's 00:03:12.67000:03:12.680 actually that's a good question because 00:03:14.80000:03:14.810 it's hiding inside of the paper 00:03:16.92900:03:16.939 separator and so we actually impregnate 00:03:19.24000:03:19.250 the paper with the electrolyte itself I 00:03:21.36900:03:21.379 think sometimes people think of kind of 00:03:23.37900:03:23.389 like this picture shows a actual liquid 00:03:25.30000:03:25.310 kind of rolling around inside the can 00:03:27.09900:03:27.109 but it's not really like water it's more 00:03:29.37900:03:29.389 like a paste and so that electrolyte 00:03:31.80900:03:31.819 does a lot of things for us one thing I 00:03:33.67000:03:33.680 wanted to point out is that there's a 00:03:35.53000:03:35.540 lot that goes into what we choose for 00:03:37.30000:03:37.310 that electrolyte just for example at 00:03:39.12900:03:39.139 Kemet we have something on the order of 00:03:40.59900:03:40.609 40 different electrolytes for our 00:03:42.42900:03:42.439 various products and so we have to 00:03:43.92900:03:43.939 consider what's the ph of the material 00:03:46.36000:03:46.370 what kind of operational temperature 00:03:47.77000:03:47.780 range does it work across what's its 00:03:50.02000:03:50.030 ability to help us reoxidized a foil 00:03:52.92900:03:52.939 which we'll probably talk about in a 00:03:54.46000:03:54.470 little bit then of course with all the 00:03:56.55900:03:56.569 other materials we've got going on is 00:03:58.17900:03:58.189 how compatible are they we don't want 00:04:00.69900:04:00.709 something that eats away at the can 00:04:02.19900:04:02.209 otherwise be able iki capacitor and then 00:04:04.27000:04:04.280 of course we need to make sure that it 00:04:06.03900:04:06.049 doesn't cost too much to use it it's not 00:04:08.02000:04:08.030 toxic and more importantly it's not 00:04:10.62900:04:10.639 flammable okay James can you walk me 00:04:13.24000:04:13.250 through how the elements of an 00:04:15.28000:04:15.290 electrolytic capacitor work together 00:04:17.34900:04:17.359 right okay we've got the anode foil the 00:04:19.95900:04:19.969 cathode foil and we've got the separator 00:04:21.87900:04:21.889 which is a red line as we show in this 00:04:23.58900:04:23.599 diagram now what we do on the anode foil 00:04:25.87000:04:25.880 is when we're processing the foil we do 00:04:28.42000:04:28.430 two things we acid etch it which gives 00:04:31.12000:04:31.130 us a really large surface area and then 00:04:33.39900:04:33.409 the second thing we do is we run it 00:04:34.83900:04:34.849 through an electrolyte bath where we 00:04:36.70000:04:36.710 actually grow the dielectric layer and 00:04:38.58900:04:38.599 so we think about the basic elements of 00:04:40.65900:04:40.669 a capacitor we get our anode plate and 00:04:42.58000:04:42.590 then we grow the dielectric 00:04:44.65000:04:44.660 and that gives us a cathode plate and so 00:04:46.45000:04:46.460 then over on the other side of the 00:04:48.01000:04:48.020 capacitor we have another foil which 00:04:49.60000:04:49.610 called the cathode foil and so in order 00:04:51.85000:04:51.860 to connect that foil which is connected 00:04:53.80000:04:53.810 to the terminals we include a conductive 00:04:56.29000:04:56.300 electrolyte between them and so that way 00:04:58.48000:04:58.490 we get the electrical connection to the 00:05:00.25000:05:00.260 actual cathode of the capacitor and so 00:05:02.11000:05:02.120 that's how we get our anode plate 00:05:04.06000:05:04.070 gathered plate all connected got okay so 00:05:07.54000:05:07.550 other than making this electrical 00:05:09.64000:05:09.650 connection how does the electrolyte do 00:05:12.61000:05:12.620 anything else for us there's a really 00:05:15.67000:05:15.680 critical thing that can happen with a 00:05:17.68000:05:17.690 aluminum electrolytic capacitor and 00:05:19.51000:05:19.520 that's called reform or heal and so 00:05:22.21000:05:22.220 remember when I talked about the 00:05:23.47000:05:23.480 electrolyte I mentioned that we consider 00:05:25.93000:05:25.940 the pH value of the electrolyte and 00:05:28.36000:05:28.370 that's because when the oxide is in 00:05:31.00000:05:31.010 contact with this electrolyte material 00:05:33.13000:05:33.140 it tends to break down the oxide which 00:05:36.31000:05:36.320 what we're showing here is a 00:05:37.51000:05:37.520 cross-section of a aluminum plate where 00:05:40.54000:05:40.550 we've grown a dielectric which is the 00:05:42.55000:05:42.560 black region and then the yellow region 00:05:44.14000:05:44.150 represents the electrolyte and so when 00:05:46.81000:05:46.820 we grow this dielectric we grow it based 00:05:49.75000:05:49.760 on what we call the formation voltage 00:05:51.31000:05:51.320 which is going to be some multiplier of 00:05:53.17000:05:53.180 the radiant voltage which we hope is 00:05:55.03000:05:55.040 more than your application voltage and 00:05:57.25000:05:57.260 so the thing that happens is over time 00:05:59.32000:05:59.330 the electrolyte will actually eat into 00:06:01.42000:06:01.430 the dielectric or the oxide and it's 00:06:04.27000:06:04.280 going to basically eat down to whatever 00:06:06.25000:06:06.260 voltage is applied and so that's one 00:06:08.98000:06:08.990 reason why when we do the formation we 00:06:10.78000:06:10.790 form it much higher than what we say we 00:06:13.63000:06:13.640 can apply to it so even though the 00:06:15.67000:06:15.680 electrolyte can eat away at this oxide 00:06:17.38000:06:17.390 it also has the ability to help regrow 00:06:20.08000:06:20.090 it and so let's just say for example 00:06:22.12000:06:22.130 it's sitting on a shelf for a couple of 00:06:24.37000:06:24.380 years well that oxide over time is going 00:06:26.56000:06:26.570 to be depleted just from the interaction 00:06:28.81000:06:28.820 between the oxide and the electrolyte 00:06:30.40000:06:30.410 when you apply a voltage to it however 00:06:32.23000:06:32.240 the dielectric will actually regrow or 00:06:35.20000:06:35.210 what we call reform and the way it does 00:06:37.18000:06:37.190 that is it pulls oxygen out of the 00:06:39.07000:06:39.080 electrolyte allowing it to regrow the 00:06:41.14000:06:41.150 oxide it seems like this electrolyte is 00:06:44.20000:06:44.210 a bit of a liability in a way then if we 00:06:48.40000:06:48.410 could just get rid of this electrolyte 00:06:50.52000:06:50.530 would it be a better capacitor yeah I 00:06:54.15900:06:54.169 think the thing we need to consider is 00:06:56.26000:06:56.270 if we have like a long life application 00:06:58.39000:06:58.400 or application where conductivity is 00:07:00.52000:07:00.530 important then we might want to consider 00:07:01.87000:07:01.880 ways to get rid of the electrolyte and 00:07:04.06000:07:04.070 so one way we can do that is with these 00:07:06.25000:07:06.260 organic aluminum polymer capacitors and 00:07:08.92000:07:08.930 in these capacitors we've replaced the 00:07:11.50000:07:11.510 electrolyte with a polymer material and 00:07:14.14000:07:14.150 so here I'm showing a cross-section of a 00:07:16.99000:07:17.000 polymer aluminum capacitor and what you 00:07:19.27000:07:19.280 might notice is the diagram doesn't look 00:07:21.18900:07:21.199 all that much different than the 00:07:22.65900:07:22.669 previous one we looked at in fact all 00:07:24.52000:07:24.530 we've done in this picture is just said 00:07:26.46900:07:26.479 that the polymer is now impregnating 00:07:28.48000:07:28.490 inside of the paper that separates the 00:07:30.43000:07:30.440 anode and cathode okay so then how do we 00:07:33.40000:07:33.410 get that electrical connection through 00:07:36.12900:07:36.139 the paper paper isn't exactly my 00:07:38.86000:07:38.870 favorite conductor yeah it turns out 00:07:41.50000:07:41.510 craft paper is not so good at conducting 00:07:43.68900:07:43.699 electricity so when we actually look 00:07:45.79000:07:45.800 inside if we think about the wet 00:07:48.18900:07:48.199 electrolytic the paper was there to 00:07:50.17000:07:50.180 physically isolate the two connections 00:07:52.75000:07:52.760 it was also there to provide a 00:07:55.37900:07:55.389 suspension for the liquid electrolyte 00:07:57.70000:07:57.710 when we look at a polymer capacitor some 00:08:00.49000:08:00.500 constructions use actually a film 00:08:01.87000:08:01.880 material instead of a paper material 00:08:03.40000:08:03.410 because it's only a physical separation 00:08:05.29000:08:05.300 the polymer is a solid material and by 00:08:09.25000:08:09.260 the way I didn't mention this before but 00:08:10.62900:08:10.639 if you're curious about it it's called P 00:08:12.76000:08:12.770 dot PE do T and so it's a conductive 00:08:15.87900:08:15.889 polymer material so is conductive 00:08:18.79000:08:18.800 polymer really an electrolyte but 00:08:21.79000:08:21.800 without all the usual gooey mess that's 00:08:24.49000:08:24.500 pretty close to being exactly the case 00:08:26.83000:08:26.840 like I said before number one it's a 00:08:28.90000:08:28.910 solid material it's still there to help 00:08:31.27000:08:31.280 provide our cathode connection from the 00:08:33.07000:08:33.080 literal cathode on the dielectric to a 00:08:35.17000:08:35.180 terminal but it's solid it doesn't dry 00:08:37.39000:08:37.400 up in the same way that a wet 00:08:38.70900:08:38.719 electrolyte does because it's solid it's 00:08:41.17000:08:41.180 not a liquid now that doesn't mean it 00:08:43.44900:08:43.459 doesn't wear out but it has a completely 00:08:45.28000:08:45.290 different wear out mechanism and in 00:08:46.78000:08:46.790 terms of conductivity which is something 00:08:48.37000:08:48.380 I think you're going to be most 00:08:49.48000:08:49.490 interested in is it can be orders of 00:08:51.79000:08:51.800 magnitude higher than a traditional 00:08:53.26000:08:53.270 electrolyte okay there are always 00:08:56.46000:08:56.470 compromises let's get this over with 00:08:59.82900:08:59.839 what do I give up by going with polymer 00:09:03.32900:09:03.339 electrolytic fantastic question because 00:09:06.49000:09:06.500 it's very rare we can say you know it's 00:09:09.19000:09:09.200 actually a lot of upside and only 00:09:11.60000:09:11.610 few downsides and so in terms of a 00:09:14.21000:09:14.220 capacitor generally people think okay 00:09:16.22000:09:16.230 when you change a material you're going 00:09:17.66000:09:17.670 to lose some of the rate of voltage 00:09:19.46000:09:19.470 capability or maybe the amount of 00:09:21.86000:09:21.870 capacitance that you get or you need 00:09:23.69000:09:23.700 more size the great thing about the 00:09:25.67000:09:25.680 polymer material is that for about the 00:09:28.22000:09:28.230 same size we get the same voltage of 00:09:29.99000:09:30.000 capacitances available because we're 00:09:31.55000:09:31.560 only replacing out one material the key 00:09:33.71000:09:33.720 benefit as I mentioned the conductivity 00:09:35.54000:09:35.550 means we get very very low es R's 00:09:37.73000:09:37.740 so the one critical trade-off is that 00:09:40.46000:09:40.470 the polymer material is more temperature 00:09:43.10000:09:43.110 sensitive in terms of maximum operating 00:09:45.29000:09:45.300 temperature and so 105 125 are really 00:09:49.00900:09:49.019 the upper limits for the technologies 00:09:50.44900:09:50.459 which isn't to say that 150 and maybe 00:09:52.46000:09:52.470 one day 175 is impossible but that's one 00:09:55.49000:09:55.500 area where we see that the operational 00:09:57.53000:09:57.540 temperature does come down a little bit 00:09:59.32900:09:59.339 compared to the same capacitance voltage 00:10:01.63900:10:01.649 and size for wet electrolytic alright so 00:10:04.73000:10:04.740 temperature is the thing then what are 00:10:07.61000:10:07.620 these temperature characteristics you're 00:10:09.76900:10:09.779 talking about 00:10:10.55000:10:10.560 okay so let's say you're okay with the 00:10:12.86000:10:12.870 temperature range and you want to 00:10:13.88000:10:13.890 operate the capacitor within its 00:10:15.31900:10:15.329 temperature range whether it's 105 over 00:10:17.03000:10:17.040 125 or some de 150 one thing to know 00:10:19.73000:10:19.740 with just about any wet electrolyte is 00:10:21.86000:10:21.870 that you're going to see a huge shift in 00:10:24.23000:10:24.240 conductivity or probably what we're more 00:10:26.50900:10:26.519 interested in with the capacitor is a 00:10:27.88900:10:27.899 shift in resistance across its 00:10:30.23000:10:30.240 temperature range so here the red graph 00:10:32.44900:10:32.459 is showing us an aluminum electrolytic 00:10:34.40000:10:34.410 from negative 55 to 125 degrees C and it 00:10:37.61000:10:37.620 shifts it changes over 250 ohms from 00:10:41.48000:10:41.490 it's cold hot temperature that's kind of 00:10:43.93900:10:43.949 tough to design for right whereas if we 00:10:45.76900:10:45.779 look at a similar-sized voltage 00:10:48.29000:10:48.300 capacitance of a conductive polymer 00:10:51.07900:10:51.089 electrolytic the same range the shift is 00:10:53.72000:10:53.730 only 233 millions and so obviously the 00:10:57.62000:10:57.630 range is much tighter but also by the 00:11:00.11000:11:00.120 way pay attention to the change in 00:11:02.38900:11:02.399 overall ESR we're talking about a 00:11:04.51900:11:04.529 capacitor that is over a home versus one 00:11:06.88900:11:06.899 that's less than 100 milli ohms for my 00:11:09.59000:11:09.600 de coupling needs for say a switching 00:11:12.71000:11:12.720 power supply how does the switching 00:11:15.59000:11:15.600 frequency affect these capacitors right 00:11:18.65000:11:18.660 sometimes a non-obvious characteristic 00:11:21.23000:11:21.240 of a capacitor especially electrolytic 00:11:23.00000:11:23.010 capacitor is that the ESR 00:11:25.40000:11:25.410 is affected by frequency and it turns 00:11:27.61900:11:27.629 out it's because internally there's an 00:11:29.24000:11:29.250 RC ladder construction that's going on 00:11:31.10000:11:31.110 and so we see the response change with 00:11:33.82900:11:33.839 frequency again because it's such a 00:11:35.62900:11:35.639 highly conductive material the overall 00:11:37.61000:11:37.620 ESR is lower and it's stability is 00:11:40.30900:11:40.319 relatively high and so here we're just 00:11:41.96000:11:41.970 gonna compare an aluminum electrolytic 00:11:43.63900:11:43.649 which again is much much higher ESR but 00:11:46.24900:11:46.259 it shifts quite a bit from say DC to 00:11:48.07900:11:48.089 tens of megahertz whereas if we look at 00:11:50.17900:11:50.189 the conductive polymer it's relatively 00:11:52.40000:11:52.410 stable right around 100 million it drops 00:11:54.47000:11:54.480 down a little bit around 100 K but it's 00:11:56.48000:11:56.490 mostly stable across the frequency sweep 00:11:58.51900:11:58.529 and then back on temperature a little 00:12:00.76900:12:00.779 bit how does temperature translate into 00:12:03.86000:12:03.870 life expectancy this is probably one of 00:12:06.92000:12:06.930 the most misunderstood and critical 00:12:09.47000:12:09.480 differences between a wet electrolyte 00:12:11.38900:12:11.399 and a conductive polymer electrolytic 00:12:13.40000:12:13.410 the lifetime of a conductive polymer is 00:12:16.30000:12:16.310 significantly better than a traditional 00:12:19.12900:12:19.139 aluminum electrolytic one of the main 00:12:21.37900:12:21.389 reasons why is that as the alumina 00:12:24.07900:12:24.089 electrolytic is used over a period of 00:12:26.21000:12:26.220 time its electrolyte dries up and so 00:12:28.79000:12:28.800 that affects its lifetime now if we look 00:12:31.73000:12:31.740 at this graph a common rule of thumb is 00:12:34.34000:12:34.350 that for every 10 degree decrease you'll 00:12:37.04000:12:37.050 double the life of an aluminum 00:12:38.87000:12:38.880 electrolytic which is typically true for 00:12:41.12000:12:41.130 a standard wet electrolyte however if we 00:12:43.57900:12:43.589 look at the conductive polymer life is 00:12:46.28000:12:46.290 10 times longer with every 20 degree 00:12:49.24900:12:49.259 decrease and so it's not a linear 00:12:51.59000:12:51.600 relationship between their lifetimes now 00:12:53.92900:12:53.939 the way you can kind of think about this 00:12:55.67000:12:55.680 is look at these lower temperatures 00:12:57.07900:12:57.089 right under 85 degrees C you're getting 00:12:59.78000:12:59.790 significantly more life out of that 00:13:01.55000:13:01.560 conductive polymer now like I said the 00:13:03.53000:13:03.540 one kind of trade-off here is that as 00:13:05.12000:13:05.130 you get closer to 105 125 that's not 00:13:07.55000:13:07.560 quite the same advantage but you still 00:13:09.65000:13:09.660 do get the benefit of lower ESR and 00:13:12.29000:13:12.300 since temperature isn't a big factor in 00:13:14.90000:13:14.910 the life of my capacitor what about self 00:13:18.49900:13:18.509 heating and internal resistance 00:13:20.90000:13:20.910 good follow-up because if we think about 00:13:23.15000:13:23.160 temperature it's easy to think about 00:13:24.55900:13:24.569 ambient but most of the time we're 00:13:26.72000:13:26.730 worried about what does the self heating 00:13:28.18900:13:28.199 due to the capacitor with in an ambient 00:13:30.37900:13:30.389 situation and so because the ESR is so 00:13:33.53000:13:33.540 low on these parts they can take on 00:13:35.54000:13:35.550 higher amounts of ripple current before 00:13:37.69900:13:37.709 their self heating contribu 00:13:39.04900:13:39.059 it's to the overall maximum temperature 00:13:40.90900:13:40.919 and so we've tried to normalize out some 00:13:42.88900:13:42.899 information here so this graph we're 00:13:44.68900:13:44.699 going to look at aluminum electrolytic 00:13:45.97900:13:45.989 versus conductive polymer and we're 00:13:48.34900:13:48.359 looking at the same voltage and 00:13:50.20900:13:50.219 capacitance and when possible in the 00:13:51.85900:13:51.869 same case sizes and so what's 00:13:53.56900:13:53.579 interesting is when you look at this 00:13:55.09900:13:55.109 you've got quite a bit more ripple 00:13:57.34900:13:57.359 current available from the conductive 00:13:59.44900:13:59.459 polymer and so basically we've done the 00:14:01.18900:14:01.199 math for you we've looked at what the 00:14:02.62900:14:02.639 self-heating would be and then we added 00:14:04.42900:14:04.439 it to an room temperature ambient to get 00:14:06.61900:14:06.629 to 105 C so if you're not calculating 00:14:08.83900:14:08.849 with room temperature then we have to do 00:14:10.15900:14:10.169 a little bit different math but the same 00:14:11.59900:14:11.609 trend holds the conductive polymers can 00:14:13.54900:14:13.559 handle quite a bit more ripple current 00:14:15.37900:14:15.389 than a traditional aluminum what oolitic 00:14:17.35900:14:17.369 which by the way it might mean you don't 00:14:19.09900:14:19.109 need as much capacitance or really where 00:14:21.73900:14:21.749 I'm getting is you don't need as many 00:14:22.81900:14:22.829 capacitors and so you might actually be 00:14:24.58900:14:24.599 able to reduce the size of your design 00:14:26.38900:14:26.399 just with a single polymer capacitor 00:14:28.63900:14:28.649 okay I think I've got a pretty good 00:14:31.03900:14:31.049 handle on all of this 00:14:32.59900:14:32.609 hit me with some of that datasheet stuff 00:14:35.11900:14:35.129 okay let's let's look at some things 00:14:37.45900:14:37.469 that maybe don't look so good on a graph 00:14:39.55900:14:39.569 but I think they're important to 00:14:40.72900:14:40.739 understand about the aluminum polymers 00:14:42.31900:14:42.329 so first of all they do have a shelf 00:14:44.29900:14:44.309 life but it's not really much different 00:14:46.03900:14:46.049 than any other surface mount capacitor 00:14:48.46900:14:48.479 the shelf life is really related to the 00:14:50.77900:14:50.789 solder ability of the component not 00:14:52.90900:14:52.919 necessarily the degradation of the 00:14:54.61900:14:54.629 capacitive element now the one exception 00:14:56.50900:14:56.519 here is that aluminum polymer capacitors 00:14:58.57900:14:58.589 and we see this with almost any 00:15:00.46900:15:00.479 capacitor using P dot is going to be 00:15:02.62900:15:02.639 rated as an MSL one rating in terms of 00:15:05.14900:15:05.159 surge voltage there are similar search 00:15:07.00900:15:07.019 capabilities to a traditional aluminum 00:15:09.01900:15:09.029 electrolytic but it's gonna be series 00:15:11.08900:15:11.099 dependent so you're gonna have to look 00:15:12.22900:15:12.239 at the parts datasheet to understand 00:15:13.78900:15:13.799 what it's search capabilities are in 00:15:15.34900:15:15.359 terms of D rating voltage D rating even 00:15:17.80900:15:17.819 temperature D rating to some extent it's 00:15:20.14900:15:20.159 not like other polymer capacitor 00:15:22.30900:15:22.319 technologies where you're told you need 00:15:23.95900:15:23.969 a ten to twenty percent voltage D rate 00:15:25.75900:15:25.769 you can use 100 percent of the applied 00:15:28.00900:15:28.019 voltage to the capacitor obviously the 00:15:30.10900:15:30.119 less volts that you apply you'll 00:15:31.45900:15:31.469 probably increase the life but it's not 00:15:33.61900:15:33.629 gonna have a significant effect on the 00:15:35.20900:15:35.219 wear out unlike traditional what 00:15:37.06900:15:37.079 electrolytic and then finally the 00:15:38.68900:15:38.699 failure mode sort of like Illumina 00:15:40.36900:15:40.379 electrolytic the ESR will change over 00:15:42.19900:15:42.209 time the mechanism for that ESR change 00:15:44.17900:15:44.189 is different but what we'll see is that 00:15:45.67900:15:45.689 the ESR will increase which will 00:15:47.74900:15:47.759 effectively turn it into an open as it 00:15:50.50900:15:50.519 reaches end-of-life 00:15:51.53000:15:51.540 okay James remind me again how 00:15:53.84000:15:53.850 traditional electrolytic and polymer are 00:15:56.72000:15:56.730 similar and different okay so they're 00:15:59.54000:15:59.550 similar in their form factors Radio lead 00:16:02.45000:16:02.460 it surface mount snapping all available 00:16:04.79000:16:04.800 in the same sort of packages that are 00:16:06.77000:16:06.780 used to quite honestly the big 00:16:08.60000:16:08.610 difference you'll notice is the colors 00:16:10.13000:16:10.140 that we use on the silkscreen are 00:16:11.48000:16:11.490 different you'll see very similar 00:16:13.04000:16:13.050 voltages and capacitances between the 00:16:15.29000:16:15.300 two now for the highest voltage parts 00:16:17.36000:16:17.370 it's still going to be done with a wet 00:16:18.89000:16:18.900 electrolytic but we keep seeing the 00:16:20.69000:16:20.700 voltages on the polymers go up higher 00:16:22.64000:16:22.650 and higher and just for context I'm 00:16:24.35000:16:24.360 talking about things like in the 300 400 00:16:26.39000:16:26.400 volt range if we're talking anything 50 00:16:28.07000:16:28.080 volts and below nearly identical and 00:16:29.93000:16:29.940 then in terms of price of course my 00:16:31.76000:16:31.770 favorite answer with capacitors is price 00:16:33.56000:16:33.570 as always it depends on a number of 00:16:35.12000:16:35.130 factors but when we look at the 00:16:36.65000:16:36.660 differences between these two we 00:16:38.24000:16:38.250 typically see things that are in the 00:16:40.04000:16:40.050 same ballpark and then of course keep in 00:16:41.99000:16:42.000 mind with lower ESR you get more 00:16:44.39000:16:44.400 effective capacitance at switching 00:16:46.01000:16:46.020 frequencies and so in a switching 00:16:47.33000:16:47.340 application you may actually be able to 00:16:48.80000:16:48.810 use fewer components which will 00:16:50.48000:16:50.490 contribute to a lower overall cost and 00:16:53.26000:16:53.270 polymer is better at what number one 00:16:56.12000:16:56.130 message if you didn't hear it before is 00:16:57.83000:16:57.840 that there is so much less ESR at these 00:17:00.47000:17:00.480 parts and so if you can't relate how 00:17:02.99000:17:03.000 that could it be helpful in your circuit 00:17:04.49000:17:04.500 just remember less ESR means less heat 00:17:07.04000:17:07.050 and almost everybody wants less heat in 00:17:09.05000:17:09.060 their designs basically allows us to 00:17:11.12000:17:11.130 address more ripple current with these 00:17:12.98000:17:12.990 devices because there is no liquid 00:17:15.17000:17:15.180 electrolyte there is a much longer 00:17:17.87000:17:17.880 lifetime associated with them now there 00:17:20.21000:17:20.220 are wear out mechanisms associated with 00:17:22.25000:17:22.260 polymer and field application engineer 00:17:24.26000:17:24.270 can talk to you about what that's going 00:17:25.40000:17:25.410 to be but the mechanism is completely 00:17:27.31900:17:27.329 different and then lastly as we saw 00:17:29.06000:17:29.070 especially with temperature the 00:17:30.44000:17:30.450 parameters for the capacitor are 00:17:32.09000:17:32.100 extremely stable we're getting much 00:17:34.19000:17:34.200 closer to a solid device which is in a 00:17:36.26000:17:36.270 surprise they are solid devices and so 00:17:38.36000:17:38.370 it just makes it much easier to design 00:17:39.83000:17:39.840 in with these parts because the range of 00:17:41.66000:17:41.670 change is much lower well I think that's 00:17:43.82000:17:43.830 all I have time for today thank you so 00:17:45.86000:17:45.870 much for joining me James oh you're very 00:17:47.75000:17:47.760 welcome Amelia I think aluminum 00:17:49.61000:17:49.620 capacitors are very popular and I think 00:17:51.47000:17:51.480 it's really important to understand the 00:17:52.73000:17:52.740 difference between these two types and 00:17:54.26000:17:54.270 before we go you didn't forget to click 00:17:56.39000:17:56.400 that 00:17:56.83000:17:56.840 did you there you can find out more 00:17:59.25900:17:59.269 information about capacitors from Kemet 00:18:02.31000:18:02.320 for chalk talks I'm Amelia Dalton from a 00:18:05.52900:18:05.539 journal comm for more chalk talks 00:18:08.61900:18:08.629 check out the chalk talks section of a 00:18:11.61900:18:11.629 journal calm or head on over to youtube 00:18:15.11900:18:15.129 keyword EEE journal
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