TO-220 Failures due to lead bending?

[Yzordderrex]

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.

thanks,
Bob

 

[Jim Thompson]

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.

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

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

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

I will contact mosfet vendor after discussing
here.

thanks,
Bob

...Jim Thompson

 

[Genome]

Production is bending a complete 90degree at the drain lead
of the mosfet directly at the package.

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

thanks,
Bob

Not in particular but since semiconductor manufacturers give 'No No'
imformation about this sort of thing elsewhere you might assume that it is
BAD practice. They also give good practice recommendations.

As a result of such warnings it is not something I would 'design in'.

But I'm totally gay and spend most of my time hoping some nice person will
post a Candy Samples movie in the Pornstars80s newsgroup.

DNA

 

[John Larkin]

But I'm totally gay and spend most of my time hoping some nice person will
post a Candy Samples movie in the Pornstars80s newsgroup.

Yuk. She was a stripper on Bourbon Street back when I lived in New
Orleans. Way high on the bovine-osity scale, in my opinion.

Tempest Storm was pretty classy in her day.

John

 

[Jim Thompson]

Yuk. She was a stripper on Bourbon Street back when I lived in New
Orleans. Way high on the bovine-osity scale, in my opinion.

Tempest Storm was pretty classy in her day.

John

What was that gal's name who performed in SF, in a swing, around
1968... about 5', very petite except for 44's ?

...Jim Thompson

 

[Phil Hobbs]

What was that gal's name who performed in SF, in a swing, around
1968... about 5', very petite except for 44's ?

...Jim Thompson

Shanda Lear?

Cheers,

Phil Hobbs

 

[Spehro Pefhany]

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.

thanks,
Bob

What kind of filthy? Black filthy or white streaks filthy?



Best regards,
Spehro Pefhany

 

[John Larkin]

What was that gal's name who performed in SF, in a swing, around
1968... about 5', very petite except for 44's ?

...Jim Thompson

Carol Doda, the original silicone diva; she performed at the Condor. I
saw her show when I was here on a business trip, and aside from the
dual deformities, she was actually pretty talented and funny.

"The Condor Club on the corner of Columbus and Broadway was also
reputedly the world's first officially recognized strip club. It is
now a night club and a municipal landmark."

John

 

[mc]

Tempest Storm was pretty classy in her day.

But this is the first time she has appeared in a thread about TO-220 lead
failures!

 

[Jim Thompson]

On Thu, 01 Jun 2006 12:31:38 -0700, Jim Thompson
[snip]

What was that gal's name who performed in SF, in a swing, around
1968... about 5', very petite except for 44's ?

...Jim Thompson

Carol Doda, the original silicone diva; she performed at the Condor. I
saw her show when I was here on a business trip, and aside from the
dual deformities, she was actually pretty talented and funny.

"The Condor Club on the corner of Columbus and Broadway was also
reputedly the world's first officially recognized strip club. It is
now a night club and a municipal landmark."

John

Carol Doda, that's the name I was trying to remember. I was only 28
at the time... I was "entranced" ;-)

...Jim Thompson

 

[Genome]

Yuk. She was a stripper on Bourbon Street back when I lived in New
Orleans. Way high on the bovine-osity scale, in my opinion.

Tempest Storm was pretty classy in her day.

John

I remember having a KitKat with chocolate all the way through.....

Didn't Dolly Parton have similar proportions when she was in 9-5...... and
was that a leather dress she wore?

DNA

 

[Spehro Pefhany]

On Thu, 01 Jun 2006 12:31:38 -0700, Jim Thompson
[snip]

What was that gal's name who performed in SF, in a swing, around
1968... about 5', very petite except for 44's ?

...Jim Thompson

Carol Doda, the original silicone diva; she performed at the Condor. I
saw her show when I was here on a business trip, and aside from the
dual deformities, she was actually pretty talented and funny.

"The Condor Club on the corner of Columbus and Broadway was also
reputedly the world's first officially recognized strip club. It is
now a night club and a municipal landmark."

John

Carol Doda, that's the name I was trying to remember. I was only 28
at the time... I was "entranced" ;-)

...Jim Thompson

I got photos from my stag just about being smothered by 'Suzy
Boobies'. She must have found a criminally insane doctor to insert
that much silicone in a single chest. If she hasn't had them reduced,
they're probably dragging on the floor now (almost exactly 17 years
ago now). whew.


Best regards,
Spehro Pefhany

 

[John Larkin]

On Thu, 01 Jun 2006 12:31:38 -0700, Jim Thompson
[snip]

What was that gal's name who performed in SF, in a swing, around
1968... about 5', very petite except for 44's ?

...Jim Thompson


Carol Doda, the original silicone diva; she performed at the Condor. I
saw her show when I was here on a business trip, and aside from the
dual deformities, she was actually pretty talented and funny.

"The Condor Club on the corner of Columbus and Broadway was also
reputedly the world's first officially recognized strip club. It is
now a night club and a municipal landmark."

John

Carol Doda, that's the name I was trying to remember. I was only 28
at the time... I was "entranced" ;-)

...Jim Thompson

I got photos from my stag just about being smothered by 'Suzy
Boobies'. She must have found a criminally insane doctor to insert
that much silicone in a single chest. If she hasn't had them reduced,
they're probably dragging on the floor now (almost exactly 17 years
ago now). whew.

CD's silicone was directly injected, no baggies. Sounds medically
scairy to me.

I like skinny women anyway.

John

 

[Mike Monett]

Carol Doda, that's the name I was trying to remember. I was only 28
at the time... I was "entranced" ;-)

...Jim Thompson

She also performed at the Brass Rail in Mountain View in the early 70's.
One of her tricks was to hold a full pitcher of beer under one tit and pour
it into a beer mug held under the other. Both were frosted from the
humidity.

A bunch of us from the engineering group at Memorex often went there for
lunch. The roast beef was excellent. One day she came to our table after
her act and sat down beside me. I asked her how long did it take to learn
how to do that - she replied "A Very Long time."

We gave her a good tip and went back to work.

Regards,

Mike Monett

 

[Jim Thompson]

On Thu, 01 Jun 2006 12:59:47 -0700, John Larkin

On Thu, 01 Jun 2006 12:31:38 -0700, Jim Thompson

[snip]

What was that gal's name who performed in SF, in a swing, around
1968... about 5', very petite except for 44's ?

...Jim Thompson


Carol Doda, the original silicone diva; she performed at the Condor. I
saw her show when I was here on a business trip, and aside from the
dual deformities, she was actually pretty talented and funny.

"The Condor Club on the corner of Columbus and Broadway was also
reputedly the world's first officially recognized strip club. It is
now a night club and a municipal landmark."

John


Carol Doda, that's the name I was trying to remember. I was only 28
at the time... I was "entranced" ;-)

...Jim Thompson

I got photos from my stag just about being smothered by 'Suzy
Boobies'. She must have found a criminally insane doctor to insert
that much silicone in a single chest. If she hasn't had them reduced,
they're probably dragging on the floor now (almost exactly 17 years
ago now). whew.

CD's silicone was directly injected, no baggies. Sounds medically
scairy to me.

I like skinny women anyway.

John

Slender plus grapefruits ;-)

...Jim Thompson

 

[Richard Henry]

On Thu, 01 Jun 2006 12:31:38 -0700, Jim Thompson
[snip]

What was that gal's name who performed in SF, in a swing, around
1968... about 5', very petite except for 44's ?

...Jim Thompson

Carol Doda, the original silicone diva; she performed at the Condor. I
saw her show when I was here on a business trip, and aside from the
dual deformities, she was actually pretty talented and funny.

"The Condor Club on the corner of Columbus and Broadway was also
reputedly the world's first officially recognized strip club. It is
now a night club and a municipal landmark."

John

Carol Doda, that's the name I was trying to remember. I was only 28
at the time... I was "entranced" ;-)

She had her own club (or at least, she worked in a club that bore her name)
when I visited SF with some friends in 70 or 71. Due to quirks in the law
of the time, she performed nude on stage (as other apprentice strippers
performed nude on little side stages) between acts of a xxx-rated film in
which she performed acts which would not be legal to do live.

 

[Richard Henry]

The roast beef was excellent.

Sure.

 

[John Larkin]

On Thu, 01 Jun 2006 12:31:38 -0700, Jim Thompson
[snip]

What was that gal's name who performed in SF, in a swing, around
1968... about 5', very petite except for 44's ?

...Jim Thompson


Carol Doda, the original silicone diva; she performed at the Condor. I
saw her show when I was here on a business trip, and aside from the
dual deformities, she was actually pretty talented and funny.

"The Condor Club on the corner of Columbus and Broadway was also
reputedly the world's first officially recognized strip club. It is
now a night club and a municipal landmark."

John

Carol Doda, that's the name I was trying to remember. I was only 28
at the time... I was "entranced" ;-)

She had her own club (or at least, she worked in a club that bore her name)
when I visited SF with some friends in 70 or 71. Due to quirks in the law
of the time, she performed nude on stage (as other apprentice strippers
performed nude on little side stages) between acts of a xxx-rated film in
which she performed acts which would not be legal to do live.

Yes, I saw that same live/film act about that time.

That place was, and still is, the Condor, though she had top billing
for some time. It's now a cajun/creole restaurant, I think.

John

 

[Jim Thompson]

Sure.

Smirk. I was thinking the same thing ;-)

...Jim Thompson

 

[Brian]

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.

thanks,
Bob

Parts should be bent BEFORE placement in the board. This eliminates the
tendency for the part to want to spring back and always have tension on it.
Under certain conditions, this tension can cause the part to crack apart.