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Proper Handling Of Mosfet Devices

11/06/2013 11:15 AM

Recently, I received a set of 8 Power Mosfet Transistors from our supplier, and they had been repackaged in a non-anti-static bubble wrap bag. We all agree that improper handling can destroy static sensitive devices. My question is if they can also be 'injured', meaning that they may work now, but may fail prematurely? Also, if you can add a link to the reference, it would help. I did find tutorials for proper handling and packaging, but none mentioned the possibility of premature failure.

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#1

Re: Proper handling of Mosfet devices

11/06/2013 11:43 AM

Yes, as with all dielectrics, the insulation can be compromised with multiple 'events' over time, none of which cause an immediate fault or failure but may compromise insulation such that its lifetime may be reduced. My experiences are with high voltage cables and other associated equipment and not specifically semiconductors but the physics are fundamentally the same. Others may have more relevant ESD information regarding the gate oxides of MOSFETS.

Now, with that being said, I doubt much of anything bad has happened to those MOSFETS and I would be comfortable using them in any non-safety critical application. Did you check the manufacturer's data sheet to see what ESD precautions are required?

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#2
In reply to #1

Re: Proper handling of Mosfet devices

11/06/2013 12:36 PM

I am waiting for a reply from the component manufacturer, since the data sheet and their website did not list ESD handling precautions.

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#5
In reply to #2

Re: Proper handling of Mosfet devices

11/06/2013 3:41 PM

if they never saw voltage I highly doubt that not being shipped in a static bag has an adverse effect, they are inherently rugged

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#8
In reply to #5

Re: Proper handling of Mosfet devices

11/07/2013 11:04 AM

If the person who handled them did not follow proper antistatic procedures, then they could have been "damaged".

Shirts, underwear or anything with man made fiber or wool can cause problems. With my last company we had to wear special straps around our feet to discharge to ground. After putting them on we had to make a test to prove that it had been electrically correctly fitted.

Anyone who has walked on nylon carpets and then touched a door handle and experienced a shock, probably had between 6-10,000 volts of charge. I do not know what the upper limits are....

This more than enough to cause damage to unprotected devices.

Please note that some devices have protection already built in!!

I would like to draw your attention to the following link, which saves me a lot of writing!:-

http://en.wikipedia.org/wiki/Static_electricity#Electronic_components

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#3

Re: Proper Handling Of Mosfet Devices

11/06/2013 2:16 PM

How do you know the bag was a non-anti-static bubble wrap bag?

What color was it?

It could be an ESD bag and look like a "normal" bag.

Just sayin'.

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#4

Re: Proper Handling Of Mosfet Devices

11/06/2013 3:34 PM

you tube has dozens of tutorials on mosfet transistors

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#6

Re: Proper Handling Of Mosfet Devices

11/06/2013 3:53 PM

I have never personally seen a degraded condition for any MOSFET.

It has always been all or none for me.

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#7

Re: Proper Handling Of Mosfet Devices

11/06/2013 10:51 PM

We are constantly being told that incremental damage can result from poor handling but I haven't seen it - I guess you wouldn't attribututea failure later on to handling anyway.

It could be that the devices have inbuilt ESD protection on their gates - zeners perhaps. Many IGBTs now ship with zeners inbuilt.

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#9

Re: Proper Handling Of Mosfet Devices

11/07/2013 11:20 AM

I cannot say whether or not your specific power mosfets are ESD sensitive. The device manufacturer is the expert on if the device is ESD sensitive or not.

However, I can answer your question:

ESD damage is particularly insidious because it rarely results in full, hard failure. On a microscopic level, the doping material gets holes in it and looks like swiss cheese. This will not typically result in an immediately noticeable effect. However, due to the changes in charge propagation across the doping levels, the operation of the device is indeed effected. Over time, the device might:

  • Work fine / as intended.
  • Not work at all.
  • Fail intermittently
  • Work for a while and fail totally later.
  • Continue to operate intermittently and not as designed.

General rule of thumb: If it came in ESD packaging, it should remain in ESD packaging until it is used on final assembly, using proper ESD practices.

If the manufacturer states that it is not ESD sensitive, and standard bubble wrap is OK, then obviously it is!

Good info from TI:

http://www.ti.com/lit/an/ssya010/ssya010.pdf

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#10
In reply to #9

Re: Proper Handling Of Mosfet Devices

11/07/2013 12:16 PM

Excellent answer. This TI ESD Report explains in Latent Damage, that these parts can be degraded, and fail later. They call these miss-handled parts "Walking Wounded."We repair Inverting Power Supplies for robotic welders, and even a 1% failure rate would be unacceptable.Thank you all for the help, and I will forward this information to our suppliers.

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#11
In reply to #9

Re: Proper Handling Of Mosfet Devices

11/07/2013 12:23 PM

GA

Good comment...

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#12

Re: Proper Handling Of Mosfet Devices

11/07/2013 4:17 PM

I have another question you may want to consider, especially if these transistors are considered an obsolete part. Since they were not in the original packaging, I would want to know if they were used or counterfeit parts. Southeast Asia recycles a lot of used components as new parts. Clipped leads are lengthend to look new, surfaces are polished and re-printed, and they may even provide new documentation and packaging.

If they are not obsolete, I would still wonder if these were pieces returned to your supplier from another customer who did not want them for whatever reason. In this case, neither you nor your supplier have any idea how well they were handled before you got them.

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#13
In reply to #12

Re: Proper Handling Of Mosfet Devices

11/07/2013 5:09 PM

I am positive that these are not counterfeit parts. They are not obsolete either. We have addressed the proper handling and packaging with our supplier, and are receiving new ones which are properly packaged. We also addressed the issue of returns, no ESD Sensitive devices will be accepted for return, except to account for inventory before disposing of them.Thank you all again for the great help.

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