Blackbuck 3 fail

[badboybilly]

I've been working on a very nice custom host build and was just finishing up connecting the blackbuck 3, set to just under 3a with a new NDB7675 pressed the new momentary switch and got a nice beam for 2 seconds and then nothing.

So checked all my connections, took switch off checked it it's fine, connected the driver with diode to bench power supply 9v nothing but tiny spark on the wire,

I've been doing this for a while know and everything always goes smoothly for me and it did again for 2 seconds then nothing,

I've herd a few people having problems with these, my soldering is always precise and quick my connections are nice, there's no shorts, I haven't disconnected the diode from the driver yet I hope it's still fine, now I'm going to have to use a 2.2a Fixed SXD but this was not the plan the plan was to push a NDB7675 further to 3a for that beautiful Cyan beam again,

Any ideas or opinions please!

 

[diachi]

Is it isolated well enough from the heatsink...? Soldering looks fine, driver looks fine otherwise. Be a shame to have to go down to 2.2A!

 

[badboybilly]

Is it isolated well enough from the heatsink...? Soldering looks fine, driver looks fine otherwise. Be a shame to have to go down to 2.2A!

Removed the driver to check and there's thermal paste under the 4 main connections also solder never made it to the bottom I made sure,

This is a joke never ever happened to me before, the diode is also LED, so much for this awesome host i turned out on the lathe, awesome 12mm momentary switch I was really going to enjoy,

Over $100 gone in a split second, I'm sure if it was the SXD the diode would still be fine.



If you look closely at the last pic you can see the lumps of thermal paste were the wires go witch shows my solder never made it threw to the copper, and Vladimir has said a thin layer of paste is sufficient for heatsinking!

 

[superduck]

Hello LPF, I'm sorry that my first post here, not in welcome section, but the issue requires my comment ))

NDB7675 has 1.4A operating current ratings and 1.7A absolute maximum ratings... You have applied 3A and are surprised the diode has down into LED brick. All that you are applying above 1.7A, you applying at your own risk.

set to just under 3a with a new NDB7675

Btw, I'm not sure there is good isolation between the cathode pad and the host, It looks like the wire pierces the silicone layer

 

[Alaskan]

oops.... appears he is correct

 

[badboybilly]

Hi there!
You should do some reading before posting!

This is not my first build and definitely not my first NDB7675

There are many threads on pushing this diode to 2.7-2.8 for a 470nm Cyan!

There cheap and this custom build was supposed to push 470nm +

Thread isn't really about diode though or current it's about driver also many threads and issues.

There was is no short or there wouldn't have been a 2 second beam! Thanks anyway!


Correct me if I'm wrong but is that not thermal paste on the anode pin!

 

[Alaskan]

Every diode I've pushed hard to reach closer to 470nm dies, some get away with it, some don't. I think he used that new member name to post without suffering bad blood, then I chimed in with that test graph, my bad.

 

[superduck]

I always read the datasheet before posting - this is the first thing that I should pay attention to. Also I have an experience with some NDB7875s, which died at double overcurrent. In your opinion, if the diode remained alive after 3A kick - this is your luck, if it died - the driver issue.

You should do some reading before posting!

Some time ago, your blackbuck 8M driver died. It happened because you closed the reference output to the ground (most likely by accident, and as result you got a full DC at this output instead of 5 volts) - this killed an LDO chip, then a dead LDO chip killed the main chip. I witnessed several "driver issues" and everytime we had find the answer beyond drivers.

Thread isn't really about diode though or current it's about driver also many threads and issues.

As I told you earlier, we need an examination of your bb3, I am unable to identify the malfunction by looking at the photo.

There was is no short or there wouldn't have been a 2 second beam! Thanks anyway!

My Bbe name is occupied by someone on this forum, it was my really first post here

I think he used that new member name to post without suffering bad blood

 

[Alaskan]

Wow, call this man doctor, he knows the terms and his way around drivers as well as laser diodes.

 

[GSS]

Hello LPF, I'm sorry that my first post here, not in welcome section, but the issue requires my comment ))

NDB7675 has 1.4A operating current ratings and 1.7A absolute maximum ratings... You have applied 3A and are surprised the diode has down into LED brick. All that you are applying above 1.7A, you applying at your own risk.


Btw, I'm not sure there is good isolation between the cathode pad and the host, It looks like the wire pierces the silicone layer

I was going to question BBB secret but if you look at Dtr's sight below the graph he offers a overdriven special.
BBB is keeping his drivers well sinked:beer:

 

[Alaskan]

Yep, I want one - Edit: Only afraid, I'm having BL with hard driven 462-465's to reach up close to 470 nm, but if free or 1/2 price gimmie! RIP my 07E OD to 3.5 A

 

[superduck]

These laser diodes has approx 0.8nm/10°C wavelength thermal shift. Thus, in order to rise it to 470nm you should add at least 40 degrees to the rated temperature. Normally the rated chip temperature is much higher than the diode case temperature (depending on operating current and heatsinking). Diode chip can easily get an overheat destroy.

Only afraid, I'm having BL with hard driven 462-465's to reach up close to 470 nm

If you crossed the street many times to a red light without consequences, this doesn't mean that you will never meet with a car bumper

I was going to question BBB secret but if you look at Dtr's sight below the graph he offers a overdriven special.

 

[paul1598419]

I had a feeling I was going to see this thread as people continued to push these diodes far past 2.2 amps to try to achieve more of a wavelength sift. I'm waiting on a 2.4 amp driver for one of these diodes, but won't be pushing it past that, as I have a couple in my stock.

 

[DTR]

Yea there could be many things that happened here. The diode might not have been able to take 3A, the driver might have had a defect, there might have been a short with the driver to the sink or even something that got overheated when adding leads. Really could be a lot of things and based on the info it is probably just guesswork right now due to all the factors of this build.

A few things I could suggest. For over driving I have not risked past 2.8A as testing shows it starts getting very unstable past that even in the large 20mm sinks. Even with that going past 2.4A for a portable is a risk the builder is taking to force the diode into a state it was not designed for. Failures are always possible when doing this and should be a risk that is accepted. Also testing where you go from zero to high current on a current regulated supply can be different than power cycling it @ 3A or whatever current just do to shock factor.

For the blackbuck when I do the units with driver I use some thermal tape and then some thermal adhesive to ensure there is no short. When I first started working with them I had one fry and take the diode with it just using thermal paste because of a short to the sink when I thought I had the solder pretty. It was why I started using thermal tape as well to create a extra buffer. Also this is a thin board that does pass the heat through to the sink from the regulator but it conducts heat better than the thicker board of the two sided SXD's which also means that it is easier to overheat and possible damage or change the soldered components or traces easier when soldering.

The best chance is probably to send the driver to Vlad and have him see if it reveals anything.

 

[badboybilly]

All great info and advice thanks!