LMZ10500: Coefficient of Thermal Expansion (CTE) for Part Number LMZ10500SILT

Hi David,

It might take a bit of time to find out this detail for you.  So let me make sure that I get you a relevant answer.

Are you interested in the CTE of the solder that attaches the integrated inductor or the lead finish on the device's pins?  

Can you tell me a little bit about your application and reason for needing this detail?

No, I am interested in the overall CTE of the part.

When any part is soldered to a PCB, there is a mismatch between the CTE of the board and the CTE of the part.  Every time the board heats up, this mismatch essentially makes the board stretch the part a little bit.  This puts a lot of stress on the solder.  It's usually way under the yield stress, but if there are a sufficient number of thermal cycles, and if they are of a high enough magnitude, the solder fatigues and cracks.

This is actually the #1 reason for solder joint failures in electronic assemblies.  My application is a non-military space application, and requests for this kind of analysis are becoming more and more common in space applications.

I know the CTE of the board.  So I need to know the CTE of the part.  Then, I can analyze the fatigue, over the anticipated life cycle of the board.

I have asked this question before (for other parts) on the E2E forum (example: https://e2e.ti.com/support/amplifiers/f/14/t/789140), and have always received reasonably prompt assistance.

Note that the link in the previous paragraph estimates the CTE of the part as approximately equal to the CTE of the leadframe.  This is generally true for leaded parts.  The part I am asking about here is leadless, so that won't be the case.

I would suggest asking your packaging people.

Thank you for explaining the background.

Yes, I have asked our packaging people.  With a module like this, it is not so straightforward since we have the silicon die, a PCB substrate, and an inductor which form the power module which has a single CTE for your calculations.  I expect a few more days and they can gather all these details and generate the CTE value.

Hi David,

We're still waiting on the vendor to get us the CTE of their component, which is used inside the LMZ10500.  I will let you know when we have it.

That'll do just fine.  Thanks!  I really appreciate the help!

I hope your holidays are fantastic and your 2020 is filled with success and happiness!

You're most welcome!