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All stored transistors are dead! The killer: SGTC

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LAN_403

Mates

Wed May 14 2008, 02:37PM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

I think that wrapping the transistor into alu-foil (and shortening the legs) should be pretty enough... I can give a try with some cheap FET...

Dr. Drone

Wed May 14 2008, 03:26PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
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Posts: 1673

GeordieBoy

Wed May 14 2008, 04:13PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

Always keep MOSFETs, IGBTs and CMOS chips in the original antistatic packaging right up until when they are fitted into the board.

You are actually _lucky_ that those devices were fully killed and not latent failures. Static damage has a habbit of producing failures in semiconductors some time into normal opeation. You can waste a lot of time and effort trying to explain such failures.

Perhaps even more strange is that I have personally witnessed MOSFETs that deliberately had their gate-oxide punctured in stress-testing, and measured short-circuit, supposedly "self-heal" and later test "okay"!

The lesson is not to use any devices unless they are still in the original anti-static tubes!

-Richie,

Mads Barnkob

Wed May 14 2008, 05:26PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Hmm I recieved my fets from a china store in normal pvc plastic zipperbags.

got antistastic bags from computer hardware i could put them in, are they really so sensitive that they can already be dead?

Dr. Drone

Wed May 14 2008, 06:40PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
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Posts: 1673

Mates

Wed May 14 2008, 07:21PM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

Dr. Spark wrote ...

I run some big coils in my garage @

and have lots of $$$ Si, all stored in the ESD packages and never had any issues in 10 years.

Your coil is DRSSTC... Actaually, I think that SSTC and DRSSTC, even if they are big, are not so Si-dangerous as SGTC. I've never had any problems while I was operating my SSTC (which is 20times more powerfull than the si-killer SGTC). I think the HF-RF (and EMP?) interference from SG based coils is something we need to be much more carefull about...
But, of course your originally packed si-components are most likely safe anyway...

BTW: In the box with the transitors were also UCC gate drivers (unpacked

) - both are dead and two tl494 which are surprisingly fine! How strange...

Reaching

Wed May 14 2008, 08:00PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

yep. ive never had problems with mosfets or igbts and i ran my bigger drsstcs right beneath them.

but one story made me cry. i tested my big marx generator a while ago with voltages up to 600kV at some 5joules energy per bang. a fuill bridge of expensive siemens igbts was dead after this test.

that was my only esd failure within 5 years.
i have a massive metal cabinet, really emv safe :P never had any problems after storing all my sensitive components within this metal cage

GeordieBoy

Wed May 14 2008, 08:04PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

It typically only requires around 50 - 100V to puncture the gate oxide layer on most power MOSFETs, so you really don't need much of a "HV" source to cause some damage. Those that work or play with laser diodes will know that they are even more easily damaged by static.

Re the zip bags: there are various types of "anti-static" materials such as dispersive, dissipative, conductive etc. I have seen black conductive bags, shiny metallic looking bags, and clear ones with a slight pink tinge all used for storing power MOSFETs during transit. Some are conductive on the outside, some conductive on the inside, and some have an embedded conductive layer inside the plastic!

If I'm not working at an anti-static workstation, i'll take the MOSFET out of the anti-static bag, and assemble the board on top of the anti-static bag, preferably without fidgeting around and definitely without walking around on a nylon carpet to fetch solder etc. Just remember to move the board off the conductive bag or conductive foam before you power it up! Been there before and you get a lot of smoke if you forget!

-Richie,

Dr. Dark Current

Wed May 14 2008, 08:31PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

This is strange, I have many FETs "dispersed" on my table, and while working with xxkV DC, SSTCs and other sparking things, I think I've never found a dead fet that I knew was not dead before.

Mathias

Wed May 14 2008, 11:22PM

Registered Member #1381 Joined: Fri Mar 07 2008, 05:24PM
Location: Hungary
Posts: 74

Same , luckaly no esd damaged ics/fets as of yet , maybe cause i store them by type in special anti static bags, and/or that black sponge thingy (wrapped in alu foil , just kiding :D)

now that i put my sstc in it's faraday cage , i can generate around 200-300w of rf power (for now) without any harmful interference or high field strength to cause damage to parts

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