5k capatitors durabillity

[ringo]

I found this on one forum about 5k capacitors:

 

The capacitors lifetime doubles by reducing 10° C.
Here the math for 5 K cap for "normal" usage for small gaming (5 Hr each day):
5000÷5÷365 = 2.739726027 ~= 2.74
So, 5 K caps have a lifetime of 2.74 year of 5 Hr each day running at 105° Celsius.

2.74 years at 105° C while running 5 Hr each day
5.48 years at 95° C while running 5 Hr each day
10.96 years at 85° C while running 5 Hr each day
21.29 years at 75° C while running 5 Hr each day

I would say, even 5 K caps would run 20 years, if not under constantly stress.

Question: at what temp capatitors usually works? I know that in load mbo temp is around 30-40c...

[Electronics Wizardy]

8 minutes ago, ringo said:

5 K caps

5k what? what unit? what specific capictor.

 

for temps, depends on board, but normally in the 60-80c range under load,

[mariushm]

The  double lifetime with every 10c is valid only for electrolytic capacitors.  Actually the formula is this one, but for 105c capacitors and most use cases you can simplify the formula below to double lifetime for each 10c below the maximum temperature rating :

 

 

 

So for example a 3300uF 16v electrolytic capacitor rated for 8000h @ 105 c , in a power supply where for the most of its life it would sit at around 40c ambient temperature because the fan blows air over it and the circuit board, the lifetime of that capacitor will be around 131.000 hours or around 5500 days or around 15 years.

 

Very low ESR / Ultra low ESR electrolytic capacitors were using water based electrolytes and those had maybe 2000-3000h @ 105c lifetime rating, so motherboards using them near the VRM where ambient temperatures were higher (around 50-60c) basically guaranteed the capacitors would go out of specs in around 8-10 years. Luckily, modern motherboards use solid (polymer) capacitors these days which have much higher lifetime and aren't so sensitive to heat.

 

Power supplies don't need to use such ultra low ESR capacitors, they use very low ESR capacitor or low ESR capacitors so the electrolyte in these is more semi-liquid and often not water based, and therefore most capacitors in power supplies are rated for at least 3-4000 hours at 105c. Often they sacrifice lifetime for space, for example instead of using a 10mm-12mm x 25mm capacitor with 8000h at 105c capacitor, they'd use a 8mm x 20mm capacitor with only 2-3000h @ 105c because it would last for more than the 3-5 year warranty of the power supply. The high end power supplies these days also abandon electrolytic capacitors for solid capacitors (even though they cost more).

 

Polymer capacitors (solid) lifetime is measured using another formula:

 

 

So for example if you have a capacitor rated for 5000h at 105c and the ambient temperature is considered 60c (because they're close to a VRM which is working at up to 80-100c so heat will radiate through the circuit board and the capacitor leads making the ambient temperature higher than the normal 30-40c ... then you have :

 

L2  = 5000 h  * 10 ^{[ ( 105 - 60 ) / 20 ]} =  5000 x 10^2.25 = 5000h  x 178 = ~ 890.000 hours  = ~ 37083 days or ~ 101 years.

 

In reality, most capacitors but in particular electrolytic capacitors have an expected lifetime of maximum 15-25 years. It's not due to the internal electrolyte in the case of the electrolytic capacitors, the main failure reason after so many years is usually the rubber bottom (through which the leads come out) that can deteriorate/break in around 15 years so when it naturally breaks the electrolyte eventually can leak out or evaporate and then the capacitor goes outside specifications.

 

Solid capacitors don't have this issue, so even with rubber breaking down, they'll still last for a long time.

 

[ringo]

1 hour ago, Electronics Wizardy said:

5k what? what unit? what specific capictor.

 

for temps, depends on board, but normally in the 60-80c range under load,

don`t know spec, these 5k are used as I see on every b350 and some x370 boards.

 

mariushm

 

Thank you very much for your long answer. I was just asking these because I will buy b350 Asus strix board which will probably have 5k capacitors, just curious. No worry than, they will last

[asand1]

2 hours ago, Electronics Wizardy said:

5k what? what unit? what specific capictor.

 

for temps, depends on board, but normally in the 60-80c range under load,

Farads or micro farads. If you are interested in replacing capacitors use higher temp and higher voltage, but keep the same value on the farads. If you are interested in prolonging the life of your existing capacitors make sure to have good case cooling.

[Electronics Wizardy]

Just now, asand1 said:

Farads or micro farads. If you are interested in replacing capacitors use higher temp and higher voltage, but keep the same value on the farads. If you are interested in prolonging the life of your existing capacitors make sure to have good case cooling.

its not 5000 farads, thats way too high.

 

 

[asand1]

Just now, Electronics Wizardy said:

its not 5000 farads, thats way too high.

 

 

Well then its micro farads, the point is that the base unit is farads. Been a while since I recapped a mobo or GPU.

[ringo]

Is it 5000 hours?

[mariushm]

No, he means lifetime rating of 5000 hours at 105c

 

These days, motherboards use polymer capacitors with values between 150uF and 270uF at 16v rating for the high side (12v from the power supply) and typically they use a bunch of capacitors with capacitance of 560uF to 820uF and 2.5v .. 4v rating for the secondary side of processor VRMs (because the processors are powered with smaller voltages, let's say 0.7v .. 1.5v  so even a capacitor with 2.5v rating would be more than adequate.

 

Because the voltage regulators are so fast to react to changes in demand, there's really no need for a lot of capacitance on the secondary side, but there's a lot of capacitors in parallel there in order to reduce the ESR of the capacitors and in order for the regulator to handle current spikes better.  

In the past, motherboard designers used 820uF to 2200uF electrolytic capacitors rated for 16v on the primary side , mainly because the power supplies were worse quality back then. On the secondary side, they used a bunch of capacitors in parallel with  1000uF to 3300uF 6.3v/10v on the lower voltage side, again mainly because larger volume capacitors have much lower ESR ... they want as low ESR as possible, not necessarily a lot of capacitance.

 

As solid (polymer) capacitors have much lower ESR than electrolytic capacitors, there's no need to use such high capacitance polymer capacitors these days.

 

The cheapest polymer capacitors you find on motherboards have lifetime ratings of 1000 to 2000 hours at 105c ( the Apaq ones Asus uses a lot are 2000h if I'm not mistaken).

There's really no need for more than 2000h, what that company does saying 5000h as something great is just marketing crap, anything equal or higher than 1000h for polymer capacitors will last more than 10 years - by that time the motherboard will probably be in the trash.

 

Yes, technically they're better capacitors but it's pointlessly better, makes no difference in quality of life of product.

 

// realized some people don't know what ESR means .. it's short for equivalent series resistance, it's a technical property of capacitors... lower is better for capacitors used in VRMs (dc-dc converters). Higher ESR means capacitors will heat more and could potentially affect negatively the output voltage of a VRM, making it fluctuate more around the desired voltage. So if your processor needs exactly 1.5v, poor quality capacitors could make the voltage oscillate between 1.495 and 1.505v and make it harder to overclock processors.

Higher ESR may be desirable in audio applications (amplifiers) or for some special situations.