JDW
Well-known member
First, I'd like to thank @ttb, @aeberbach and others who contributed to my separate thread on SE/30 SONY Chip Voltages. The conclusion of that thread is that while most of the 47uF capacitors on the motherboard see only 5v, there are 4 which see about 12V. That is actually a problem for those 4 capacitors. I know that many people, myself included, recap very often with Solid Tantalum capacitors, myself having used 16V rated parts in the past. But there are important reasons why we need to stop using those 16V rated "solid" tantalums on the SE/30 motherboard, despite the fact that most of you and even myself haven't experienced any burn-downs yet.
Below is a video I released a few days ago. While it is a general advice video about how to pick capacitors for recapping just about anything, I used the SE/30 motherboard as a practical example in the final half of the video, explaining why you should take extreme care with your tantalum capacitor selection.
In summary, it's cheaper to make all 10pcs of 47uF the same type of capacitor since you get a price break for quantities of 10 or more, and that choice should be something other than 16V Solid Tantalum. Even though 6 out of 10 can be 16V Solid Tantalum, for the sake of using the manufacturer specified voltage derating, it's best to either use 25V Solid Tantalum (yes, they do come in 7.3mm lengths) or 16V (or higher voltage) Polymer Tantalum. You can even use OS-CON caps which don't have a voltage derating, although they do have a higher leakage current than even Polymer Tantalum. (Leakage of Solid Tantalum is about the same as fluid filled Aluminum Electrolytic capacitors, which is extremely low at around 7 or 8µA. But since the SE/30 is not battery powered, higher leakage really won't matter. The OS-CON caps also have lower ESR than even the Polymer Tantalums.)
Be sure to watch the video above on YouTube so you can click SHOW MORE to expand the text description I wrote under the video. There you will find Mouser links to individual capacitors which are fully compatible and safe to use on the SE/30 motherboard, along with my notes about usage.
I fully realize that many of you have recapped with 16V Solid Tantalum for years, and I myself have two boards like that. Indeed, I've used those 16V Solid Tantalum caps for years without issue. But the fact remains that any Solid Tantalum capacitor used at voltages higher than the manufacturer specified derating faces increased failure rates. As shown in Table 4 on page 7 of this AVX Technical Document, the failure rate of 47uF 16V Solid Tantalum capacitors with a recommended 50% voltage derating stands at about 0.03% versus 1.1% for no voltage derating. And when solid tantalum fails, it is not only a dead short but the cap itself goes up in flames. Polymer Tantalum in contrast will not burst into flames and has a 20% voltage derating. That means you can only use a 16V Solid Tantalum at a max of 8V to be within the derating guidelines, but you can use up to 12.8V on a 16V rated Polymer Tantalum. Choose a 25V rated Polymer Tantalum, and it can handle up to 20V continually and still be within manufacturer recommended derating guidelines.
Yes, I will admit there are some manufacturers that recommend even more stringent derating guidelines of 1/3 the max rated voltage for solid tantalum. But that's all the more reason to use Polymer Tantalum instead.
All said, what I plan to do for my own SE/30 boards is swap out C3, C4, C9 & C10 for caps with the proper voltage derating, leaving the other 16V Solid Tantalums as they are since they only see 5V.
Lastly, when you solder tantalum caps and especially the polymer types, be sure to keep the soldering iron heat to 350°C or less and never keep the iron on each side of the capacitor for more than 3 seconds. This information is also specified in the data sheets as heating with a soldering iron can affect failure rate as well.
I hope this information helps my fellow recappers get the longest life possible from their chosen replacement capacitors.
Below is a video I released a few days ago. While it is a general advice video about how to pick capacitors for recapping just about anything, I used the SE/30 motherboard as a practical example in the final half of the video, explaining why you should take extreme care with your tantalum capacitor selection.
In summary, it's cheaper to make all 10pcs of 47uF the same type of capacitor since you get a price break for quantities of 10 or more, and that choice should be something other than 16V Solid Tantalum. Even though 6 out of 10 can be 16V Solid Tantalum, for the sake of using the manufacturer specified voltage derating, it's best to either use 25V Solid Tantalum (yes, they do come in 7.3mm lengths) or 16V (or higher voltage) Polymer Tantalum. You can even use OS-CON caps which don't have a voltage derating, although they do have a higher leakage current than even Polymer Tantalum. (Leakage of Solid Tantalum is about the same as fluid filled Aluminum Electrolytic capacitors, which is extremely low at around 7 or 8µA. But since the SE/30 is not battery powered, higher leakage really won't matter. The OS-CON caps also have lower ESR than even the Polymer Tantalums.)
Be sure to watch the video above on YouTube so you can click SHOW MORE to expand the text description I wrote under the video. There you will find Mouser links to individual capacitors which are fully compatible and safe to use on the SE/30 motherboard, along with my notes about usage.
I fully realize that many of you have recapped with 16V Solid Tantalum for years, and I myself have two boards like that. Indeed, I've used those 16V Solid Tantalum caps for years without issue. But the fact remains that any Solid Tantalum capacitor used at voltages higher than the manufacturer specified derating faces increased failure rates. As shown in Table 4 on page 7 of this AVX Technical Document, the failure rate of 47uF 16V Solid Tantalum capacitors with a recommended 50% voltage derating stands at about 0.03% versus 1.1% for no voltage derating. And when solid tantalum fails, it is not only a dead short but the cap itself goes up in flames. Polymer Tantalum in contrast will not burst into flames and has a 20% voltage derating. That means you can only use a 16V Solid Tantalum at a max of 8V to be within the derating guidelines, but you can use up to 12.8V on a 16V rated Polymer Tantalum. Choose a 25V rated Polymer Tantalum, and it can handle up to 20V continually and still be within manufacturer recommended derating guidelines.
Yes, I will admit there are some manufacturers that recommend even more stringent derating guidelines of 1/3 the max rated voltage for solid tantalum. But that's all the more reason to use Polymer Tantalum instead.
All said, what I plan to do for my own SE/30 boards is swap out C3, C4, C9 & C10 for caps with the proper voltage derating, leaving the other 16V Solid Tantalums as they are since they only see 5V.
Lastly, when you solder tantalum caps and especially the polymer types, be sure to keep the soldering iron heat to 350°C or less and never keep the iron on each side of the capacitor for more than 3 seconds. This information is also specified in the data sheets as heating with a soldering iron can affect failure rate as well.
I hope this information helps my fellow recappers get the longest life possible from their chosen replacement capacitors.