TO-220 Failures due to lead bending?

[Brian]

Slender plus grapefruits ;-)

...Jim Thompson

Cmon, you geeks have never touched a naked woman that wasn't 2-D on paper or
a monitor.

 

[Pooh Bear]

I have a small 480v 5w flyback power supply that has had a large number
of field failures. In general the failure rate is about 0.4%, one out
of 250 units. This I can live with. One particular customer in
Northern California has had a 25% failure rate. Most of the units come
back filthy so that there may be an environmental aspect to the problem
as well. I think units are in an air stream which may be blown in from
a rooftop intake. We have beat the crap out of the power supplies here
at the factory and have not been able to kill them. Heated transistors
to 150c, put 1500v dc on the supply, etc and they keep on running. I
am begining to think there may be a stress related problem with the
lead bend. Production is bending a complete 90degree at the drain lead
of the mosfet directly at the package. It looks like the package
ruptures and sends plasma out and destroys the clamp diodes and control
chip and so forth. Destruction is very complete here.

So question is then - has anybody ever heard of failures related to
this type of handling? I will contact mosfet vendor after discussing
here.

Device manufacturers explicitly say not to bend the lead at the body. I assume
it places a strain on the die.

Graham

 

[Terry Given]

"directly at the package" would imply that the lead is bent without
any support at the package side of the lead?




I've seen such failures with DIP I/C's. I think such bends destroy
the little "hermeticity" afforded by the molding process.

As have I, with re-worked SO-8 apckages. Luckily it was the bit in a
gatedrive that decided whether or not to turn the IGBT off

I'd support the lead adjacent to the package with some kind clamp so
that the plastic is not stressed.

At a place I worked, we did exactly this with a progressive tool the
first part of the lever pull clamped the leads just outside the package,
then the bending occurred. The production manager said it took them a
while, and a lot of failures, to come up with this approach.


Cheers
Terry

 

[Jim Thompson]

[snip where inadequate newsreader failed :-]

Cmon, you geeks have never touched a naked woman that wasn't 2-D on paper or
a monitor.

I had four kids... they're probably all older than you are... none of
which was immaculate conception ;-)

...Jim Thompson

 

[Yzordderrex]

Filthy in that it looks like drives were rained on. Terminal blocks
are actually rusty. They are supposed to be in a pollution degree 2 or
4 or something that signifies a closed box. So right off the bat these
motor drives are being mis-applied. I expect our production dept was
stressing dies and more than likely upsetting seal where lead enters
plastic case. They have since learned how to form leads without
stressing part.

regards,
Bob

 

[Spehro Pefhany]

Filthy in that it looks like drives were rained on. Terminal blocks
are actually rusty. They are supposed to be in a pollution degree 2 or
4 or something that signifies a closed box. So right off the bat these
motor drives are being mis-applied. I expect our production dept was
stressing dies and more than likely upsetting seal where lead enters
plastic case. They have since learned how to form leads without
stressing part.

regards,
Bob

If the boards are getting *wet*, as well as dirty (ie. conductive),
all bets are off. Burned up is to be expected.

Better enclosure and conformal coating.


Best regards,
Spehro Pefhany

 

[John Larkin]

Cmon, you geeks have never touched a naked woman that wasn't 2-D on paper or
a monitor.

Au contraire. There's a type of woman who goes for engineers, and they
are a very nice type indeed.

And I never touch my monitor; the fingerprints are hard to get off the
lcd.

John

 

[Brian]

I had four kids... they're probably all older than you are... none of

which was immaculate conception ;-)

...Jim Thompson

This only proves to me that you had a mailman.

 

[Brian]

And I never touch my monitor; the fingerprints are hard to get off the

lcd.

John

Not to mention the "fluids" you have deposited there.

 

[John Larkin]

Not to mention the "fluids" you have deposited there.

You really are weird.

John

 

[Brian]

You really are weird.

John

Yes, very true.

 

[Jim Thompson]

You really are weird.

John

Let's award him "Village Idiot of the Week", so he can then contend
for higher honor ;-)

...Jim Thompson

 

[rob]

You really are weird.

John

Nah, I think he's referring to Window's "sticky keys" feature.

 

[Brian]

Let's award him "Village Idiot of the Week", so he can then contend
for higher honor ;-)

...Jim Thompson

I'll accept it when you accept the "Village Idiot That Didn't Get Any This
Week" award.

 

[John Larkin]

Nah, I think he's referring to Window's "sticky keys" feature.

He talks about sex all the time because he doesn't know much about
electronics. Ironic, since he doesn't know much about sex, either.

John

 

[Spehro Pefhany]

He talks about sex all the time because he doesn't know much about
electronics. Ironic, since he doesn't know much about sex, either.

John

I have a nagging feeling that the underwear I've got on at the moment
may well be older than him.


Best regards,
Spehro Pefhany

 

[Brian]

He talks about sex all the time because he doesn't know much about
electronics. Ironic, since he doesn't know much about sex, either.

John

John, I did more in electronics in the first 15 years than you will in your
life. Now, I can just sit back, run the company I always wanted, and never
worry about a thing. In the meantime, you keep in there eating Mac and
Cheese every nite with your sig. other. After all, he loves ya!

 

[Brian]

I have a nagging feeling that the underwear I've got on at the moment
may well be older than him.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
[email protected] Info for manufacturers:
http://www.trexon.com
Embedded software/hardware/analog Info for designers:
http://www.speff.com

Spehro, come on now. You were the one that could not present facts on your
side of the arguement and ran from it, to instead talk about women's boobs!
Your just being even more ignorant now than in that series of posts. Just
admit you know zero about the subject and move on. I would, after alll, you
don't see me trying to move in on your expertise as a inside player in the
homosexual community, do you?

 

[John Larkin]

I have a nagging feeling that the underwear I've got on at the moment
may well be older than him.

Cleaner, too.

John

 

[John Larkin]

John, I did more in electronics in the first 15 years than you will in your
life.

OK, I've designed over a thousand circuit boards, roughly $200e6 in
sales, and hacked close to a thousand programs, a million lines or
two, including three RTOSs and a couple of compilers. Lately, timing
system and beam modulators for NIF, and a lot of NMR and aerospace
stuff.

Now, I can just sit back, run the company I always wanted, and never
worry about a thing.

Show us a link.

I've delegated the running of my company to people who are good at
that sort of thing, so I can keep designing electronics:

http://www.highlandtechnology.com/index.html

In the meantime, you keep in there eating Mac and
Cheese every nite with your sig. other. After all, he loves ya!

Mo does make mighty tasty mac and cheese, with white cheddar and
crunchy toasted baked bread cubes on top. She's Irish/Sicilian and
does interesting things. I just cooked lunch, portabellas and veggies
(mostly garlic!) in a white wine sauce over pasta, and I'm just now
finishing off the last of the chocolate truffles.

All I need now, to make life perfect, is a good affordable source for
connectorized 1310 nm singlemode lasers.

John