EEVblog Electronics Community Forum
Electronics => Manufacturing & Assembly => Topic started by: coppercone2 on September 25, 2024, 05:21:23 am
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Sockets for components, are you supposed to make them ESD safe?
I have a custom heat sink thing I made, for a TO package. I used copper, and drilled oversized holes, which I filled with epoxy and then drilled out so their insulated.
However, when you slide the part on, it does make contact with the epoxy. Its for a apex amplifier chip, I already burned a number of them out, their delicate to rail voltage imbalance.
If I were to make another one, is this acceptable or should I be using some additive to the epoxy "bushing" that slides on a part? Since its just very thin (0.5mm thick and 2mm tall), does it perhaps not pose a hazard to the part? It is just like a coating to prevent short circuits. It works very well mechanically.
I used the PCB repair epoxy (DP270)
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Generally you want a material which causes the least triboelectric effect.
Unless you are constantly sliding the device in and out of your 2mm long epoxy tubes, I cannot imagine they will build up much charge. Especially when mounted in a metal shell.
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Although it is good practice, you're not required by law to make them ESD-safe.
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I mean it seems like there has to be some limit, especially for high impedance stuff.
Obviously, I don't want a leakage path either (for say a non inverting buffer)
I broke 2 or maybe 3 of these expensive chips through other mishaps
They commonly use ceramic bushings, all the ceramic plate i test on a ESD tester shows fail. I think they have PTFE bushings too.
So long its small and only moves during assembly its OK?
I assume if you have a rattling bushing insulator on a TO3 package that could be bad. Can it charge up and destroy it? Usually it gets a bit of solder on it so it prevents vibration. Like a PTFE bushing in a anodized heatsink hole.
It is a pretty old technology, and bushing s are common. I assume at this age there would be a warning about it, if it was a threat.
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Ceramics are good insulators, but are not generally ESD safe. You can get coated or modified ceramics that are ESD safe, but I imagine that has some impact on the insulation properties.
To stop any charge buildup you need to have a leakage path, and thus you will have a non-ideal insulator.
For high impedance stuff you need good insulators, so you want to protect from ESD in other ways (i.e. low leakage clamping diodes/transistors).
The best way to test the potential for charge buildup would be with a bare wire sliding up and down through the hole and and ESD meter, or better an electrometer.
ESD will be generated by movement, so if there is no movement after assembly then it shouldn't be an issue.
The small amount of movement of a bushing is unlikely to generate much charge, except in extreme conditions where you will likely encounter bigger problems.
Note though that even (fast) air movement can create a charge buildup.