We put a LMZ10501 ( http://www.ti.com/lit/ds/symlink/lmz10501.pdf ) part in a new project, and we have been running into a few issues. We have 7 of these supplies on each board, and of the 12 boards we have had assembled only one come back from manufacturing and worked on the first bootup. After some investigation we came to the realization that the BGA on the top of the part is a little more fragile than expected. Small cracks and fractures of the BGA seem to render the supply completely inoperable, and we have seen cases where it looks like the BGA got squeezed down during the manufacturing process - thus shorting out the entire supply. One of the questions we had is can we get a version of this where the top side of the part is encased in plastic, as to provide more protection from bench handling? It seems the part only takes a little bit of pressure to break and its getting damaged by putting the board into our test setup. The other question we had, is the BGA part on top, is it leadfree or a leaded part? Several of our customers are strictly leaded - as to mitigate tin whisker concerns.
Any feedback or input is welcomed and appreciated.
Be sure to look at Ap Notes AN-1112 and AN-1412. Also View the video "How to Solder Rework Nano Module Packages".
Alan Martin TI - SVA
Thanks for the feedback!
It's a starting place - here are a few concerns pertaining the micro SMD Wafer Level Chip Scale Package. I know the LMZ10501 was originally designed by National Semiconductor, has the Micro SMD on the top of the part been retro-actively tested to verify conformity to TI's standards?
The other thing questions were, can we get the same package where the top has been encapsulated in plastic/epoxy to increase ruggedization?
And is the Micro SMD done lead free or is it leaded?
Yes the device was designed by NSC. NSC was purchased by TI last year. The NSC design team is fully intact under the "TI umbrella". We are all "happy campers" and are moving full speed ahead with follow-on designs.
WIth regard to conformity to TI standards I'll have to get back to you because the guy I need to ask is out on vacation for a few weeks.
As far as an encapsulated version. You can be sure that we are working on it, but the delivery date is not announced yet.
I need to ask the packaging folks about the lead free question.
Alan Martin - TI Silicon Valley Analog
Were you able to find out any additional information with respect to the packaging and lead-free option?
In terms of the lead-free question, yes the part is lead-free.
Please refer to the following document for the exact chemical composition of the part:
In terms of the assembly issues you mentioned, we should be able to provide guidance. Would it be possible to provide the mounting conditions including the equipment used, settings, stencil file, etc? If it is more appropriate, I can get you in touch with our packaging expert via email. Let me know what you would prefer.
I was wondering if there is any news on the plastic encapsulated part, and if there were pre-release parts we could test.
For now, we have decided to simply encapsulate the entire part on the PCB with an epoxy to dramatically improve their work bench reliability.
I am sorry for the late reply. In terms of pre-released parts, do you have a TI sales contact in your region? I would like contact them to get you parts.
We just got an EOL notification for the part and it looks like its getting replaced with the plastic encapsulated part. I think this clears up any concerns.
Do you have a link to the EOL notification?
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