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i was wondering for a project of mine if i can order components that are made for a long time of usage. would Mil-spec components fit under this category? What i basically want are parts that are good for a very long time, and have a very high reliability, in addition to high life cycle (amount of times it is used) I can count out electrolytics, as they don't last long. Components with high power ratings are also probably better. Does anyone know if there are companies that manufacture these?

p.s. Is there an alternative to relays that i can use to switch high amounts of power? because relays have a low amount of switchings.

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  • \$\begingroup\$ Please split out the relay question into a separate question \$\endgroup\$ – Brian Carlton Apr 30 '11 at 18:12
  • \$\begingroup\$ As important to splitting out the relay question would be specifying what sort of power - AC, DC, high voltage or high current, what kind of load (resistive or inductive), etc. \$\endgroup\$ – Chris Stratton May 1 '11 at 4:38
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The life of your electronics will probably be more a function of your design then it will be of the components. You can review the component reliability data from the manufacturer's websites. Without a proper design you will not achieve the specified reliability. Without process controls in manufacturing you will not be able to manufacture a reliable product. A strategy of trying to test the quality into a product is doomed to failure.

A lot of components will follow the Arrhenius activiation law which estimates the component life based on the operating temperature and the maximum operating temperature specification of the component. Reducing the operating temperature will have a dramatic affect on life. For example -- reducing the operating temperature of electrolytic capacitors by 10degC will increase the capacitor life by roughly a factor of 2. A 105degC rated capacitor run at 85degC will last roughly 4 times as long as running an 85degC rated capacitor at 85degC.

You can switch high amounts of power with MOSFETs and IGBTs. For reliability heat will be your enemy. You want to transition the semiconductor from off to on and on to off quickly to minimize the heating. There are transient thermal curves at the back of the datasheet. The thermal mass of the die is small. Switching the transistor in 10uS versus 1mS will have a dramatic affect on the junction temperature.

In general --

  • Design review -- thermal, electrical stress, environmental stress
  • Design qualification
  • Choose components with a wide temperature.
  • Choose quality component manufacturers.
  • Handle your components properly -- ESD, humidity, environment
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    \$\begingroup\$ Heating a transistor isn't the worst thing (as long as you run it cooler than its rated temp, + keep lots of margin so Arrhenius' equation gives you more lifetime). It's thermal cycling that's the killer. \$\endgroup\$ – Jason S Dec 20 '09 at 15:16
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First off, many times the life of a specific electronics product boils down to 1 or 2 components on a board, and usually those can be the capacitors used on a project. Capacitor lifetimes are very dependent on which type you choose (tantalum being the best, I think, but someone correct me if I'm wrong). Also, you want to keep these items cool as many times the life of the component doubles for every 10 °C below the maximum operating temperature. So if any part of the product will be getting hot (> 50-60 °C) try to find ways to keep it cool through heat sinking or through other means.

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    \$\begingroup\$ I think ceramics have the best lifetime actually. Tantalums are electrolytic, they're just a different material than aluminum electrolytic caps, and they do have better lifetimes than aluminum. see wikipedia: en.wikipedia.org/wiki/Tantalum_capacitor \$\endgroup\$ – Jason S Dec 20 '09 at 15:14
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Depending on your application you can use a transistor to "turn things on". Also, you can always use a Solid State relay. (no moving parts). As far as the rest of your question. I am sorry I do not know.

Hope that helps.

Ril3y

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I suppose it depends on how long is long. Do you need this device to go on well after your life span? certain components, for example a back electret microphone capsule, will die of over usage before you do. I'd imagine the majority chips and discreet components will probably outlast all of us, as long as you don't abuse them. Be very careful to only operate within your components power ratings, if your worried about damage from static discharge then avoid CMOS chips.

I've got a 22 year old Atari computer, still works perfect to this day and I'm sure it has a good few delicate chips inside.

Things like electrolytic capacitors have come a long way in the last 10-20 years, a modern one probably lasts substantially longer than the ones in my Atari. You could always go overkill on the power rating of your components, i'd imagine they would put up a better fight in the long run.

Come to think of it, my uncle has a 30 year old electric guitar, it may have something to do with having passive circuitry, but it's fine to this day, it probably sounds better now. I don't think it's ever been repaired.

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