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Diode Failure Mechanism & Mode

  • Thread starter RST Engineering \(jw\)
  • Start date
L

legg

Jan 1, 1970
0
Suppose I have a popcorn glass diode like a 1N4148. I will slowly advance
the temperature so as to not thermally shock the glass.

At what temperature (or range of temperatures) would you expect the diode to
fail?

What is the mechanism for the failure (thermal expansion, solder melt,
etc.)?

What is the mode of failure (short, open, gross deterioration, etc.)?

Glass diode thermistors are rated for operation to 250degC, probably
due to problems with solder migration above that. No semiconductors
involved.

I expect semiconductors would see the same problem.

RL
 
L

legg

Jan 1, 1970
0
With nickel leads, the thermistor range is extended to 300degC.

RL
 
J

Joerg

Jan 1, 1970
0
Hello Robert,
Excellent start, but better if a gap is left between the part and the
pliers.
Do not remember the recommended minimum gap.


True. You can't fully grab the middle lead with regular needle nose
pliers because they'll mostly lock onto the outside lead. I took an
older pair and ground down the tips except for the very end. That
provides a gap so it really only grabs at the tip.

And then everything went SMT...
 
S

Spehro Pefhany

Jan 1, 1970
0
Glass diode thermistors are rated for operation to 250degC, probably
due to problems with solder migration above that. No semiconductors
involved.

I expect semiconductors would see the same problem.

RL

I think I've seen some similar items (bulk silicon thermistor?) rated
for intermittent 1200F. Could be wrong. Target application was
domestic self-cleaning ovens.


Best regards,
Spehro Pefhany
 
S

Stanislaw Flatto

Jan 1, 1970
0
Robert said:
..and so, if you want to decrease collision with Mr Murphy, then revise
the design for Justin Case...

Oh God! have mercy.
Justin Case A. Shuttle on launching pad, don't tell me that some
un-inspected and un-certified parts were included, and the system cannot
be refuelled because a no-return valve was assembled into piping the
wrong way, inspected and certified.
After that, and only after that! NASA speck specified one way valves to
have different diameter threads on "in" and "out" ends.

Justin Case B. Idiot-proof design in which a push button is positioned
behind a metal revolving plate with a hole in "zero" position so the
button can be pressed. The "newer, better, upgraded" idiot got a very
thin long screwdriver and succeeded to press the button in HV position.
QED.

Justin Case C. Old, very old, mobile logical circuitry for support of
avionics, few racks of eqipment on vehicle and another vehicle sporting
a 3-phase generator for powering it. The "smartie" responsible noticed
that the main power plug has some screws wobbling, disassembled it, put
everything back, tightened the screws and connected.
Result, IC's exploding with such force that they created holes in
adjacent prints.
On inspection we found that the ground connection was inserted into one
of the phases and one phase was grounded.

My favorite Justin Case D. Avionics inspection of military planes
system, the security IS verything as some of the equipment includes
various "nasties". So a _continuous_ wire is running between ALL parts
of the equipment to let the safety part to be able to check existance of
proper connection of all parts for powering the system.
Safety refuses to connect, gives us about a week of hair tearing till we
find on "desperate" "crazy" full disassembly, can you visualise this
with equipment distributed behind panels in all parts of the "bird" till
we found it. Properly produced and inspected, proofs in papers! cables
were connected (Mil-Speck multicontacts) male to male and the connecting
technician did not notice but worked with such force or impatience that
the pins were bent everywhich way.

I rest my case of Justin Case and ask the court to call Mr.Murphy for
his expert opinion.


Have fun

Stanislaw
Slack user from Ulladulla.
 
R

Robert Baer

Jan 1, 1970
0
RST said:
OOOOOOOOOkay. Let me try again. The diode is being operated forward bias
at about a milliampere. It has been handled with kid gloves from the day it
left the factory until it was carefully installed with no stress on the
leads into the circuit. I put the sucker into an oven and start slowly
bringing the temperature up.

At what temperature (or AROUND what temperature) would you expect the diode
to reach an elastic limit of some sort, either physical or electrical, and
not come back to approximately the same forward voltage at room temperature
than it had before the thermal stress test? What do you SUSPECT might be
the mode of the failure.

Jim
Hmmm..have yet to crank up SMTs above 200C but suspect problems in
the 250 to 300C region in the following order: 1) die attach solder
melting - most likely an open circuit as the result; 2) failing that
(meaning the solder is a liquid but the whisker wire is holding the die
in place) then diffusion of the P and N dopants resulting in a short.
That is, if you have a *furnace* or *kiln* to get up that high...
Oh yeah; next to go is that the glass enclosure melts and then the
die melts and then the metal melts and then the furnace liquefies and
Pele has a good laugh...
 
R

Robert Baer

Jan 1, 1970
0
Jim said:
"The horse may talk" ;-)

...Jim Thompson
Mister Ed????
Is that you typing instead??
Or is it a neigh-bor?
 
R

Robert Baer

Jan 1, 1970
0
Stanislaw said:
Oh God! have mercy.
Justin Case A. Shuttle on launching pad, don't tell me that some
un-inspected and un-certified parts were included, and the system cannot
be refuelled because a no-return valve was assembled into piping the
wrong way, inspected and certified.
After that, and only after that! NASA speck specified one way valves to
have different diameter threads on "in" and "out" ends.

Justin Case B. Idiot-proof design in which a push button is positioned
behind a metal revolving plate with a hole in "zero" position so the
button can be pressed. The "newer, better, upgraded" idiot got a very
thin long screwdriver and succeeded to press the button in HV position.
QED.

Justin Case C. Old, very old, mobile logical circuitry for support of
avionics, few racks of eqipment on vehicle and another vehicle sporting
a 3-phase generator for powering it. The "smartie" responsible noticed
that the main power plug has some screws wobbling, disassembled it, put
everything back, tightened the screws and connected.
Result, IC's exploding with such force that they created holes in
adjacent prints.
On inspection we found that the ground connection was inserted into one
of the phases and one phase was grounded.

My favorite Justin Case D. Avionics inspection of military planes
system, the security IS verything as some of the equipment includes
various "nasties". So a _continuous_ wire is running between ALL parts
of the equipment to let the safety part to be able to check existance of
proper connection of all parts for powering the system.
Safety refuses to connect, gives us about a week of hair tearing till we
find on "desperate" "crazy" full disassembly, can you visualise this
with equipment distributed behind panels in all parts of the "bird" till
we found it. Properly produced and inspected, proofs in papers! cables
were connected (Mil-Speck multicontacts) male to male and the connecting
technician did not notice but worked with such force or impatience that
the pins were bent everywhich way.

I rest my case of Justin Case and ask the court to call Mr.Murphy for
his expert opinion.


Have fun

Stanislaw
Slack user from Ulladulla.
Good greif!
And i would not be surprised to learn that those were *mild* cases.
 
P

Paul E. Schoen

Jan 1, 1970
0
Stanislaw Flatto said:
Oh God! have mercy.


My favorite Justin Case D. Avionics inspection of military planes system,
the security IS verything as some of the equipment includes
various "nasties". So a _continuous_ wire is running between ALL parts of
the equipment to let the safety part to be able to check existance of
proper connection of all parts for powering the system.
Safety refuses to connect, gives us about a week of hair tearing till we
find on "desperate" "crazy" full disassembly, can you visualise this with
equipment distributed behind panels in all parts of the "bird" till we
found it. Properly produced and inspected, proofs in papers! cables were
connected (Mil-Speck multicontacts) male to male and the connecting
technician did not notice but worked with such force or impatience that
the pins were bent everywhich way.

I have seen something like this once, but it was a replacement cable for a
customer, who later called back and said it would not work. I could hardly
believe it when it was returned and I looked at it. The male pins were put
in the female housing and vice-versa.

Of course, this cable was made by the same technician who once was
struggling, for what seemed to be hours, to drill a few small holes in a
steel panel. The drill was making an awful noise, and so was he. When I
finally investigated I found he had the drill in reverse. I think he was
still able to drill one or two holes.

I also once found, in a customer's facility, some drill bits that were
sharpened backwards. I thought they were left-handed, but the spiral was
right-handed. Maybe, in this case, two wrongs make a left?

Paul
 
S

Stanislaw Flatto

Jan 1, 1970
0
Robert said:
Good greif!
And i would not be surprised to learn that those were *mild* cases.

Just samples of "Failure Mechanism & Mode" as presented by designs of
experts in technology and Quality Control.
"The best definition of infinity is human stupidity!"

Have fun

Stanislaw
Slack user from Ulladulla.
 
R

Rich Grise

Jan 1, 1970
0
Approximately 1 milliampere of forward current. 5 volt supply with 4.7k
resistor in series, with the diode far away from the current source.

Well, then, put it in an oven, do the experiment, and then tell _us_ what
the results were!

And howcome you still haven't learned to bottom-post?

Good Luck!
Rich
 
R

Rich Grise

Jan 1, 1970
0
Hello Tom,

More than 1% of the bad thru-hole era diodes I found had cracks in the
glass. Some of them were missing chunks of glass.

But, did the glass break before, or after, the diode failed? i.e., was
the diode's failure the cause of the broken glass?

Thanks,
Rich
 
R

Rich Grise

Jan 1, 1970
0
Mine was blue. No idea where it is now.

I used a blue one too, but it belonged to my employer at the time.
I do have a couple of WSU-30Ms, however. ;-)

Cheers!
Rich
 
R

Rich Grise

Jan 1, 1970
0
Mine was blue. No idea where it is now.

Same here. I was going to post a picture, but I couldn't find it :-(
[/QUOTE]

http://images.google.com/images?q=lead+bender

Interestingly, the four out of the first eight images that are the thing
we're talking about show red ones!

Must be a political thing. ;-) ("Is your lead bender red, or blue?")
(mine were always blue, or maybe aquamarine, as well.)

Cheers!
Rich
 
R

Rich Grise

Jan 1, 1970
0
The picture, the post, or the horse tied to the post?

"The horse may talk" ;-)
[/QUOTE]

"Sheep LIE!!!"

Cheers!
Rich
 
R

Rich Grise

Jan 1, 1970
0
Mister Ed????
Is that you typing instead??
Or is it a neigh-bor?

The king sentenced some peasant to death for some triviality. The peasant,
at his sentencing, said to the king, "Your majesty, if you postpone my
death for one years' time, I will teach your horse to talk. Yours will be
the only kingdom in the realm whose king's horse can talk! How about it?"
So, the king says, "OK, one year." About six months later, he's in the
stable, still babbling at the horse, and the poop-shoveler guy asks, "Why
did you make such a stupid claim?" And the peasant says, "Well, I got a
year of life. The king could die, there could be a revolution, I could die
of natural causes, and who knows? The horse may talk."

Cheers!
Rich
 
R

Rich Grise

Jan 1, 1970
0
---
Even that's no guarantee. The 100% right way to do it is to grab
the lead with a pair of longnose pliers in one hand and then to bend
the free (non-diode) end of the lead where it exits the pliers.

Same way with T0-220s; grab the lead where it necks down on the
package side of the lead and then bend the free end of it down.

Start with the middle lead. :)

Makes me want to design a jig - The tips of my needle-nose are tapered,
so it's hard to get a nice right-angle bend. But a sort of a cradle, that
clamps the leads but lets you bend closer to the epoxy could be useful.

Cheers!
Rich
 
T

tlbs101

Jan 1, 1970
0
Joerg said:
Hello Tom,


More than 1% of the bad thru-hole era diodes I found had cracks in the
glass. Some of them were missing chunks of glass.

--
Regards, Joerg

I should have made one clarification that is applicable: Mil-HDBK-338
pertains to military class parts, and not commercial parts. So Joerg,
and the rest of you, are all probably correct that the "other"
percentage is much higher in commercial parts. IMHO mechanical
failures are still the lowest probability mode of failure compared with
the other modes.

I looked at other military-type standards for failure modes, but the
rest of them showed "open" and "short" as the only 2 modes.

I doubt there is a "commercial" standard for failure modes, because
rigorous industry-wide FMEAs are usually not performed for commercial
components/assemblies.

Tom
 
J

Joerg

Jan 1, 1970
0
Hello Tom,
I should have made one clarification that is applicable: Mil-HDBK-338
pertains to military class parts, and not commercial parts. So Joerg,
and the rest of you, are all probably correct that the "other"
percentage is much higher in commercial parts. IMHO mechanical
failures are still the lowest probability mode of failure compared with
the other modes.

I looked at other military-type standards for failure modes, but the
rest of them showed "open" and "short" as the only 2 modes.

Maybe true. However, some of the broken glass in diodes I have seen were
when I was serving. We weren't supposed to repair this stuff ourselves
but the maintenance guys used to be quite happy when we presented the
diagnosis on a silver platter. A lot of times it might have been simple
mechanical trauma that cause it.

I doubt there is a "commercial" standard for failure modes, because
rigorous industry-wide FMEAs are usually not performed for commercial
components/assemblies.

Oh yeah, there is. If we didn't do FMEA in the medical device industry
the Federales would come swooping in and shut the place down, and for
good reason (FDA is known to occasionally do that...).
 
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