5 replies to this topic

[BigMax]

People of similar interests,

This is my first post on this forum, so be gentle with me :-)

ANYWAY, my question is, when 'disassembling' a power semiconductor (ie puck SCR) for post mortem purposes should we be concerned about the possibility of hazardous materials contained within these type of devices? For example, is beryllium oxide still used in the manufacture of such devices?

Thanks in advance for your consideration.

[Harry Dampers]

Welcome Max .....haven't got the answer but nice to see that someone else realises the value of splitting the devices Post - Mortem to get some idea of why it failed.

[marke]

Hello BigMax

Good question.

The puck style SCRs do not contain hazadous materials. The biggest problem is watching that you dont cut your fingers on the remains of the capsule when you cut it apart.
Most of the module type SCRs are also quite safe, but some (higher power only) can contain Beryllium Oxide as an insulator.
Beryllium oxide is expensive and although it offers an improved thermal resistance, the gain is only of benefit on larger higher power devices. Most modules use an aluminium oxide ceramic as a thermally conductive insulator. This is the white insulator bewteen the die and the baseplate.
Another material that is very good in this region, is Aluminium Nitride. It has a very good thermal characteristic and on larger devices, can offer definite thermal advantages. At this stage, the cost is still high so it is not in common usage yet.
I am not aware of toxic problems from Aluminium Nitride. It is sold as a machinable thermally conductive ceramic material.
Berillium Oxide is most commonly used in RF devices where the power density is much higher and the capacitance is very important.

[GGOSS]

All forum members.

It appears that the issue of hazardous materials within power semiconductor devices has been adequately addressed by Marke.

However, having previously disected many SCRs to identify fault cause myself, and after seeking independant advice to get clarification, it has become apparent that there are many self professed experts out there that really don't seem to know what they are on about. And unfortunately that includes some of the SCR manufacturers!

I for one would like to see images of failed SCRs (after disection & with a description of the fault cause) posted on this forum, by people who really understand the subject.

Alternatively, if anyone is aware of a WEB site that provides this information or has access to related documentation, I'm sure many members of this forum would find it useful!

Regards,
GGOSS

[marke]

Good idea!!

How about, sending good photos of damaged SCR wafers and I will look at setting up a page so that they can be viewed and commented on.
;e;

[GGOSS]

Would if I could, but we don't have a product that fails!!!

Let me see if I can scrounge some from the opposition.:D