Measured reverse base damage of NPN

I remember there was some discussion if low reverse currents can damage a bipolar transistor. I got a new toy (HP 4142B with 3 SMUs) and did some quick testing.

It seems that even 1uA reverse current starts to destroy the transistor. Here's a graph that shows hFE as a function of amp-seconds from the base:

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I also did an another test with 0.1 for 2000s and 1mA for 2000s:

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The reverse voltage increased during the test from 7.5 to 7.9V

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The quick test was limited to 2000s, i.e. 2mAs, but I'll do a longer run to see if the detoriation depends on the charge only or does current have some effect.

(Unfortunately transistors _were_ harmed during the tests.)

--
mikko OH2HVJ
Reply to
Mikko OH2HVJ
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Were they new transistors out of the box? Can the graphs be explained by something other than physical damage to the structure like charge-storage effect or some kind of wear-in process that would occur when a new transistor is used in any configuration?

Reply to
bitrex

Forward-active beta varies for different amounts of constant current thru the base-emitter junction there's nothing unusual about that. AFAIK it doesn't matter which direction the current is going to affect it.

Reply to
bitrex

Yikes.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

recovers.

Reply to
tom

...

Don't have a heating chamber at home, using the one in kitchen for electronics causes distortion and our sauna at home has a hard limit

next to plastic.

hFE curves before heating (hFE~=105 for Ic=1mA, Vce=3V)

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The performance drop at low currents is especially gruesome!

After heating (hFE~=177 for Ic=1mA, Vce=3V)

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Heat cures!

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mikko OH2HVJ
Reply to
Mikko OH2HVJ

Yes, they were out of the box. The effect was visible even after hours no backwards BE current, I would expect any charge storage to clear within that time - on the other hand heating seems to help.

Here's one paper I found about the subject - it mentions 'interface states created in the oxide over the emitter-base junction during the stress' as being one generally assumed reason for additional base current.

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I guess the interface/surface states could be cleared up by heat ?

So - add a heater or cover your bases!

--
mikko
Reply to
Mikko OH2HVJ

Pease says someplace that Widlar used to use his cigar on metal can transistors for exactly this.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

t

Fun... here's a silly question. Can you cure 'em with C-E voltage/current heating?

Heal thyself, physician.

George H.

Reply to
George Herold

ge

s

run

t

There was reputed to be an HP pulse generator which worked much better afte r the service engineer stubbed out his cigarette on the output transistor.

Other people's cigarettes worked equally well.

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Bill Sloman, Sydney
Reply to
bill.sloman

You may find that the amount of measurable damage depends on the product of time and revers current, not unlike radiation damage or ionic contamination.

Reply to
Robert Baer

It is well known (since before the Apollo mission) that the damage can be annealed out.

Reply to
Robert Baer

Yeah it just seemed like an awful large droop for such a small amount of charge which is why I was trying to explore whether it could be accounted for by a measurement error.

Reply to
bitrex

1uA, to 0.05 A*s:
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100/1000uA
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The resolution of the latter graph is not that good, but to me it looks like the 1uA current causes damage slower.

--
mikko
Reply to
Mikko OH2HVJ

downloads.hindawi.com/journals/apec/2001/053209.pdf

Reply to
bloggs.fredbloggs.fred

Good work! Last year I did a few simple experiments too and noticed the same rapid initial decline in beta which then tends to level off. But I never thought to look for changes in breakdown voltage.

piglet

Reply to
piglet

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