Tutorial: Pressing a Diode

[ApexProxy]

Does this work with every size of diode(specifically a 9mm)?

EDIT: I just realized the kryton I will be getting from the GB will be a pressfit design. Is the process any different?

This process will work with a 3.8mm, 5.6mm, and 9mm diodes but remember you need to get the appropriate sized press. Flaminpyro offers a press specific to each sized diode. For 9mm diodes you also need to make sure you remove the any optics and mounting brackets and clean up the diode before you press and the small red pin guard on some diodes can usually be left on during pressing.

 

[The Baron]

do we take the red pin guard off or can we leave it on? whats its purpose?

 

[ApexProxy]

It was used for the diode's previous purpose and totally unnecessary to keep on the diode but also makes no difference either way. If you have enough lead coming off the diode you can just leave the guard on. Its up to you.

You might even be better off using the press to remove the guard like Silvershot mentioned. Just push the diode into the press with the guard on and after you press the diode the press itself might pull off the guard when you take it apart which is sometimes easier than trying to pull it off yourself. If the guard comes off then great, if not you can leave it if you can access enough of the pins for soldering.

 

[cheech226]

great tutorial! it's been needed.
my press doesn't fit over the pink thing on the m140 diodes. the plastic pink pries up pretty easily and then i clip the soldered end of the pins off with nail clippers and slide the insulator off.

 

[Bionic-Badger]

I prefer to use a real vise rather than pliers. Then you can get even pressure on the press ends. The pliers work in a pinch though.

 

[ApexProxy]

@Cheech
Thanks bro. I also do that pretty much with small wire cutters instead. Half the time I can just slide the guard off without having to touch the pins at all if the pins are clean enough on arrival.

@Bionic-Badger
Its pretty much up to you. I find I am able to position the press very well in my pliers and the design of the press itself means that it doesn't exactly need super even pressure since its basically a piston in a cylinder.

I have become quite adept at pressing using pliers and have yet to damage a single diode in pressing. I am even able to do direct press heatsinks using a pair of channel locks

With a vice its very easy to exert too much pressure but with pliers you need to take care that you position it right and that nothing slips.

 

[SixTee9]

Nice tutorial there Apex, good job

 

[Psi]

Is a thermal interface material (TIM) ever used? Such as that used with CPUs & heat sinks.

 

[ApexProxy]

Something like Arctic Silver can be used in extremely small amounts directly inside the diode pocket of the module(seriously small amount in the pocket) as well as around a diode module for increased contact area to the heatsink and around the heatsink for increased contact area to the host.

 

[Psi]

TIM is not normal? I have modeled the heat transfer in electronics and there is a definite difference between with/without TIM. The high wattage CPUs used to burn out before the manufacturers built in thermal shutdown.

I am just curious is all.

 

[ApexProxy]

Most of the time it isn't used.

The difference is that in the diode pocket the diode is pressed into it with such force that pretty much all the thermal grease would just come out.

It can be used on the diode module to increase contact with the heatsink but in that design the gaps are usually so large that the effectiveness of the grease is minimal. Tolerances between the diode module and heatsink tend to be quite large unfortunately so the gaps are beyond the aid of thermal compound. This goes for the tolerances between the heatsink and host as well. With a CPU the tolerances are quite insanely small so the contact area is quite large and this allows the thermal compound to be drawn extremely thin which is the time that it becomes most effective. Thermal compound is designed to fill in extremely small gaps between the contact surfaces and in the case of lasers the gaps are usually significantly larger than in CPU/cooler contact.

In a nutshell, it doesn't help anywhere near as much as it does with a CPU.

Something else that can be done is use thermal epoxy which works significantly better with transferring over larger gaps. The problem is thermal epoxy drys to make extremely strong bonds so the laser cannot be disassembled later.

 

[Psi]

This is the typical with TIM. Imagine two 1" square plates pressed together with about 100 lbs of force. Just different TIMs can make a several degree difference. No TIM versus *any* TIM is a very large and distinct delta.

I have beaten this to death in so many ways ... ... .. .

 

[ApexProxy]

That's true. Thing is with lasers you aren't working with flat surfaces pressed together but rather mostly cylindrical parts that may or may not even touch all the way around. A diode pressed in a diode pocket is crammed in so well that it can even microscopically alter the shape of the pocket and diode and mesh together even better. A TIM added in the pocket will increase thermal conduction through places that aren't meshed together so perfectly and on the front surface that isn't touching with as much force as the sides are.

Arctic silver for ex uses extremely small pieces of silver dust that will smash into the tiniest spaces and act as heat pathways where there would have otherwise been a gap. When you have a gap that is larger than the particles of silver you are not using the silver itself as the transfer pathway but instead using the silver and the grease it is suspended in which, while better than nothing, is a very small fraction of the efficiency. Other types of TIMs may use ceramic and even diamond particles as the material to create the pathways.

 

[Psi]

The CPUs was only an example. TO5 transistors and others are similar to laser diodes. As I said I have modeled and tested this & predates laser diodes. Modeled is computer modeling.

 

[ApexProxy]

I was also trying to add in some info for anyone reading this thread later on. TIMs have greatly varying effectiveness depending a lot on the actual design of the laser parts. I had one laser a while back that worked amazingly well with some added arctic silver because it was intended to press together in just the right ways to facilitate transfer between parts.

 

[icecruncher]

I prefer to use a real vise rather than pliers. Then you can get even pressure on the press ends. The pliers work in a pinch though.

True, but they've also destroyed a couple of my first diodes. Not a fan of pliers personally.

People - go to harbor frieght and buy a cheap vise for a few bucks. It'll save your diodes.

I really liked the good explanation on how far to press them in. Easy to only seat them flush or crush. Nicely done!

FInally, I've had good success with Thermal stuff, like arctic silver. My first build was in a MXDL host and is still running with a phazor diode at about 250mw which is WAY above spec, thanks in part, I believe to the artic silver. Works for me, but YMMV