Electrical Component Thermal Fatigue?
Electrical Component Thermal Fatigue?
(OP)
I'm a structures guy, but I've been asked to look at thermal fatigue for a surface mounted transistor. To give you some background, it is company policy not to use surface mounted components on electronics boards. But the electrical guys want to use a specific surface mounted transistor, but cannot perform a thermal cycle test on any board with the transistor until they have some analysis showing the transistor good.
I'm pretty ignorant to electrical components, so any information would be greatly appreciated. I have a book by Steinberg, called Preventing Thermal Cycling and Vibration Failures in Electronic Equipement, but I've heard his method is flawed and is not neccessarily a conservative analysis.
How does one go about doing one of these analyses? Does anybody have fatigue properties for Solder? Does anybody have good advice for me?
Thanks in Advance
I'm pretty ignorant to electrical components, so any information would be greatly appreciated. I have a book by Steinberg, called Preventing Thermal Cycling and Vibration Failures in Electronic Equipement, but I've heard his method is flawed and is not neccessarily a conservative analysis.
How does one go about doing one of these analyses? Does anybody have fatigue properties for Solder? Does anybody have good advice for me?
Thanks in Advance





RE: Electrical Component Thermal Fatigue?
Sorry I couldn't be of more help.
saxon
RE: Electrical Component Thermal Fatigue?
I agree, it's a Catch 22. We can't test the boards until we have analysis showing that it will pass the thermal cycling qualification. And we can't do an analysis without good empirical test data.
I do have some empirical data for thermal fatigue of solder. The Engelmaier curves from Bell Labs, relate fatigue cycles to strain. And, I can calculate the thermal strain using the Steinberg method I mentioned in my first post.
The problem that I have, is that I have heard the Steinberg method is flawed and may not give acceptable results. I am searching for a "better" method, to calculate thermal fatigue.
RE: Electrical Component Thermal Fatigue?
TTFN
RE: Electrical Component Thermal Fatigue?
RE: Electrical Component Thermal Fatigue?
Issues with surface mount solder and fatique were solved nearly twenty years ago.
TTFN
RE: Electrical Component Thermal Fatigue?
sounds like the poster has two issues at hand: the fatigue limitatations of the transistor (the manufacturer will have to help you there) and the fatigue limitations of the surface mount/board/and fastener technology.
Designing to 12 thermal cycles falls in the category of low cycle fatigue, where failure is defined by the peak thermal stresses (i.e. peak operating temperatures). sounds like you have a fairly simple design issue to sort out.