Very basic diode / heatsinc question

The part of the diode that has to be in contact with the heatsinc is the base, correct? or does the can really have any effect on the thermal dissapation properties?

The more contact surface the more dissipation, it's quite simple unless I'm missing something xD

In the case of a diode pressed into an aixiz module, the heat transfer from diode casing to heatsink (aixiz module) is essentially through the side of the base, as this is the area in press-fit contact with the module. This small region has to conduct a fair bit of heat away from the diode. The aixiz module should be contained in a larger heatsink.

Well the aixiz modules is the reason I asked since they are a press fit, I noticed the can didn't come in contact with any surface and I wondered if i couldn't make it better by allowing the can to also dissapate heat by packing the outside of the can with al. oxide thermal compound. or in making my own heatsincs, maybe make a hole the size of the can rather than the size of the base. although it seems in all the sleds i've taken apart the can has never been in contact with the heatsinc. although they're not ever run at the temps/amps that we normally run them.

Is cause when the can is soldered to the base, there's a step, and opposite of the diameter of the base, that is a fixed and precise measure, this step is not granted as position and measure, from different manufacturers ..... so, when you build a module, you can grant the external diameter of the diode housing as a precise measure, but not the step and can position.

For fit also the can, you need to make the hole with:

a precise 5,6mm, less 0,2mm for the press fit

a first step at the point where the can is soldered to the base, that is, usually, 4,2mm dia and 0,15mm height, but not a granted measure

a second step of the diameter of the can, that is usually 3,6mm dia, but not a granted measure (other than this, being a piece made with a pressform and not a machined piece, the base of the can, where it bend in the lip that is soldered to the base, is not a precise angle, but a round angle, also if small)

And also, with the small thickness of the can, it also is not robust enough for support the pressure of a press-fit operation of this gender, without deformate, and unglue or chip the front window ..... so, for the little thermal improvement that you can get, the risk is too high ..... much better work coupling the base to the module in better way .

I improved the thermal transfer with some of my diodes, using very small thermal compound in the assembly, on the module step, when i press fit the diode, then some thermal glue, like the arctic silver alumina (the white one, not the metal one), that is insulant, putting some of it on the back of the diode and aixiz module, in this way



This for the diodes that i don't plan to change ..... or the same thing using fujik silicone thermal glue, when i made some mounting where i want the possibility to dismantle them (it's a little bit less efficent, but opposite to the bicomponent one, it can be took away)

This almost double the transfer rate, without risk the can and the window

very nice idea :0

lv128 said:

The part of the diode that has to be in contact with the heatsinc is the base, correct? or does the can really have any effect on the thermal dissapation properties?

Click to expand...

The base has the best thermal contact with the actual chip.

On some Sony Red 20X diodes I have; the manufacturer soldered the base to the nickel-plated heatsink in two different locations. This is the best method of tranferring heat away from the diode.

I use thermal compound when I press diodes into modules.

As these diodes become more powerful, we will need better heatsinking.

LarryDFW