Is the IRF3708 static sensitive?
hinv
Posts: 1,255
I ordered some IRF3708 MOSFETs from a vendor on ebay and I got them today packed in white open cell foam. Are these things static sensitive? If so, I should probably just send them back.
Comments
As a general principle, it's not a good idea to ship any kind of MOS device in contact with ordinary plastic foam or any other kind of static-prone insulating material. Sometimes the foam has material incorporated into it or sprayed onto it that reduces static charges. It all depends on the humidity, on the movement of the box and the materials it's made from, etc.
The problem is that you don't know whether there's been any damage. The IRF3708 may work just fine, forever. It may not work at all and you don't know whether it's your fault from the circuit you're using it in or whether it was defective to begin with or was damaged in some other shipment or the shipment to you. It may also work for a while, then fail. That makes it even harder to assign blame and, when it fails, it may take out other parts.
Lots of people ship cheap stuff in foam. Static dissipating foam or plastic film or bags are relatively expensive. A lot of electronics parts are pretty robust and the static problem tends to be much less in the spring, summer, and fall when the humidity is relatively high. Everything has some risk. You have to decide how much you're willing to pay to mitigate it.
Sure, you can send back the MOSfets for improper packing. But at your own shipping cost, right? And then you need to persuade the vendor to ship another order.
If you buy in the quantities that I do, they may just decide to cut their losses and not fill more orders.
Over the years, I have had very little trouble with static sensitive material regardless of rough handling. But I am not shut in a building with nylon carpets and 10% humidity.
Optimally, you should just test the items if it is a small order and return them if they show real defects. Of course if you are big buyer, you have clout and you can just tell the supplier that you cannot afford to have a whole production run ruined by a bad batch of components.
Parallax does a beautiful job of anti-static protection, but nobody else I deal with seems to even try.
-Phil
If you want to use a light to indicate functionality, an LED will work fine on 9 Volts if you just limit the current appropriately with Ohms law. (LEDs will even work on 220VAC with the proper current limiting resistor, but it will conduct 50% of the time.) Personally, I'd just test for continuity and not try for a full power stress test. If static has damaged them, the gate is likely no good. And 12V gel cell should be fused to limit the current surge in testing. Silly things happen with tangled wires, miscalculations, unseen shorts - so a fuse is wise. Even better is a bench power supply that can limit current and shut down much faster than a fuse.
I suspect flooring and A/C or central heating create most of the static electricity problems. I just can't imagine having a problem if you are sitting in 60% humidity on a tile floor. I suppose a fabric chair might be creating problems as well.
In any event, any ground strap should have a 1 meg resistor in line as one can also accidentally electrocute themselves if they are attached to a direct ground around an electronics work bench.
Be warned.... Since most MOSfets have an internal flyback diode, if you accidentally apply reverse of the correct polarity to the Drain and Source, the device will get very hot, may burn up, and fail.