LOC open circuit failure

[Benm]

I've encountered something odd with a lpc open case diode: the thing is open circuit, not doing anything at all anymore.

The diode was driven quite conservatively at 300-ish mA, but failed in an unusual mode: it didn't go led on me, but just presents an open circuit, Obviously i suspected a failure in wiring, but that doesnt seem to be the case - all connections are soldered solid.

Perhaps a bond wire was melted though, i can't really see that with the naked eye.

Anyone experienced something similar before?

 

[daguin]

It happens. When I've looked, I've found a break/burn inside the diode with one of the fine wires.

Peace,
dave

 

[Benm]

There doenst seem to be any physical damage to the diode or connecting wires... which leaves me a bit puzzled over this one. I've seen plenty of diodes gone led before, but this is something entirely different.

I'm curious about probable cause, even while replacing the diode isn't costly at all.

 

[Greenmechanic]

Probably a speck of dust settled on the thin wires and burned one, as Dave stated.
I've had a couple do this just from changing lenses.
That's why I prefer the LCC.
No worry's about dust or metal shavings.
It's all part of the game, buy another one and try again

 

[Benm]

Might be something like that - i was adjusting the lens when it died (or just a second before). I don't use a spring though, just the aixiz glass lens with a thin layer of teflon tape to make it fit well.

The thing lasted a year at 300+ mA though (incidental use, but still), so not much to complain about, time to order a couple of sleds

 

[BShanahan14rulz]

well, if it's going to waste, might as well try to pulse it like an LED, perhaps it'll come back....

An electrical open, though, sounds like a busted bond wire or something.

 

[JellyCrab]

well, if it's going to waste, might as well try to pulse it like an LED, perhaps it'll come back....

An electrical open, though, sounds like a busted bond wire or something.

So, like clicking it on and off really fast? Does that work for blu-rays?

 

[Benm]

Nah, the diode is toast allright - takes zero current even with the driver pushing almost 7 volts through it. I suppose its a broken bond wire, there is no way to restore those on laser diodes (on RF power transistors there sometimes is, but those dies are much much larger).

Its too bad it died this way, i was kinda wondering how long it would take before that diode went LED. Those LOC's seem very sturdy from an electro-optical point of view, but they remain mechanically fragile.

 

[LarryDFW]

Benm;

I have made an electrical probe with a small pointed pick.

Probe the bond wire connection on the die.

It worked on a Red 16X with a broken bond wire.

Larry

 

[Benm]

Sounds like a cool idea, but its gonna be difficult in this case: i have no way to remove the diode from the aixiz module it is in, apart from just ramming it out with a bit in a vise... which is rather destructive to the diode

I havent removed it yet though, i'll try to take some macro photos just to satisfy curiosity before replacing it.

 

[Greenmechanic]

They actually come out a lot easier then they press in, (most of the time)
Use a short rod a little larger then the LD's face and a small socket on the back side larger then the LD's base. I've removed lots of them without damage.

 

[Benm]

Thats interesting - i suppose when you press against the 'pedestal' the die sits on it would be feasible to remove them without damage. I've never tried it though, i only remove them when they are dead. With canned diodes the damage is pretty obvious then, but these might survive

 

[BShanahan14rulz]

Yeah, with an LED, the chip's so big it probably doesn't take much damage from a reverse pulse. With a LD, it's probably less effective.