*new* ecu question

[drew93tsi]

i keep getting into arguments with ppl here at work on ecus, need a little clarification please. ok here we go...if a cap "leaks" what exactly eats the copper traces and the board itself...considering that the cap conatians nothing acidic? after tearing apart a "cap" to find that it only contains kevlar/mylar material for insulation purposes...so if the cap "leaks" it would only be leaking insulation not acidic base properties that would eat the board...so is it fair to say that the insulation would leak and the cap would get too hot and melt the epoxy that covers the copper trace and perhaps the caps would arch causing the board to char? i have heard electrolytic "fluids" cause damage to the board...but the only thing in a "cap" is insulation and even if it was acidic it would explode on contact with metal...acid cant eat through plastic or glass...kinda confused need some clarification as to how the epoxy is takin off! so basically what in a cap would cause the board to be "eatin"? i read vfaq already and it contained little info.

[M 4 L k i 3 R]

A capacitor is two plates of metal that are separated a 'dielectric'. That dielectric can be plastic, air, mylar, liquid, etc. as long as it does NOT conduct electricity. It depends on the capacitor's final use that determines what is actually in it.

To be continued when I get to work...

[drew93tsi]

please do cause im stumped on this one...if all caps are the same what makes them different in a dsm ecu...

[sandman_1221]

Ok, there are several types of caps, electrolytic and creamic are 2. electrolytic caps are filled with a capactive fluid that can be corosive. They are mainly used for large variances in a signal like huge current swings or voltage swings. They act like a filter. The problem with them is that they have a self life. Usually around 10-15 years after that they will leak therefore rendering the ecu inoperable. unless you change them before. Manufacture would rather use ceramic cap but the technology might not of been there yet to make capacitors with huge capacitance like 1 milli farad out of ceramic material.

[DQ Driver]

where do you guys learn this stuff?

[drew93tsi]

i try to read as much as possible...but the problem is i can read all day, but if dont physically see it....its not worth anything...that will make me as bad as ppl who just give hearsay to questions...

[drew93tsi]

Ok, there are several types of caps, electrolytic and creamic are 2. electrolytic caps are filled with a capactive fluid that can be corosive. They are mainly used for large variances in a signal like huge current swings or voltage swings. They act like a filter. The problem with them is that they have a self life. Usually around 10-15 years after that they will leak therefore rendering the ecu inoperable. unless you change them before. Manufacture would rather use ceramic cap but the technology might not of been there yet to make capacitors with huge capacitance like 1 milli farad out of ceramic material.


but the problem is that i took one apart to see whats inside and it was nothing but kevlar rolled up..no fluids...thats why i was wondering...i was aslo under the impression that all caps do the same thing...just control currents to avoid harmful spikes to ecu...they used to make oil based caps, those are now no longer made. whats the fluid that gives the leaking insulation its corrosive property? even if it was corrosive it shouldnt be able to eat glass apoxy...

[boostedjuice]

I see someone hasn't been very busy at work lately.

[DQ Driver]

i see i haven't been paying attention in my classes. 2 quarters away from my EE degree


HA

[drew93tsi]

I see someone hasn't been very busy at work lately.


damn straight :D you of all ppl should know how mobile is....phone rang once...

[M 4 L k i 3 R]

Drew,
To answer your question about no liquid being present...
Instead of having liquid sloshing around inside the capacitor, an electrolyte-soaked paper is used, some modern types are even virtually solid.

Back to your original question, why do they leak?
Many reasons...
Excess heat, from either internal or external sources, will eventually start to evaporate the liquid, building up pressure in the closed cannister and cause it to leak out slowly or even explode! (See picture)
http://home.earthlink.net/~doniteli/cap4.jpg
Something like for every 10deg C over 80-ish will halve the life-span of a cap, and how many times does your car get over 80 in the summer?
Overvoltage Excess voltages to a capacitor will leak through the isolation very violently, creating hot-spots which makes explosion very likely.
Time Electrolyte capacitors have a self-healing ability that allows them to 'regenerate' if any small variances occor within the capacitor. However, the dielectric may deteriorate beyond regeneration, resulting in a high leakage current, or the electrolyte will eventually dry away, reducing the capacity by several orders of magnitude. This is often the case when it comes to restoring an antique radio or an antique car, err... DSM.

I hope that helps you guys out. If you have any more questions, post away and I'll try to remember or find the answer.

[Iwishiwascool]

columbusDSM has been very techy today.

good times.

[Funkdariaa]

i see i haven't been paying attention in my classes. 2 quarters away from my EE degree


HA

Maybe you haven't been paying attention but that wouldn't matter. :confused

I graduated in EE last may and they don't talk about things like this for the most part. You'll get tidbits here and there but four years of school just isn't enough to go that in depth. You learn about the theory and you learn how to learn. You learn about things like this when you get into the field if you need to know about them. You'll more than likely have ALOT of smart old people around you that know AOLT and they learned it when they were younger from some smart old guy.

[drew93tsi]

hense me asking you guys....ya old farts...wait im getting old too...thanks for all the intelligent answers guys you have been a big help!