Electronics > Metrology

New TI REF54EVM Evaluation Module Leaked

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floobydust:
I wonder if they are collectibles  ;)  Mouser does not list the ADR45xxD. Digi-Key shows no stock, no price, no lead time - request quotation only.
There were delays closing the Milpitas wafer fab(s)/hermetic packaging, it might have happened end 2021/beginning 2022 and you got that stock? But today it appears the parts are unobtainium.

Why is the new REF54 not offered in the LCC-8 package?

Kleinstein:

--- Quote from: floobydust on December 10, 2023, 06:53:54 pm ---Why is the new REF54 not offered in the LCC-8 package?

--- End quote ---
That is a good question. Still with the ref70xx the performance in the LCC-8 package is still not that much better than in a plastic case as one may hope for.
If power is not a big issue the ref70xx may be the alternative that is available in LCC-8.

floobydust:
It must be marketing specmanship - advertise the Holy Grail of low TC, yet moisture and flex stress of the plastic package undermine the overall performance and let's all be in denial and not mention it in app notes or datasheets.

I found this on LCC CTE which I was wondering about, did not compare to old friend TO-46 package rolled out in 1962, it's over 60 years old.

Andreas:
Hmm,

https://cleanroom.byu.edu/cte_materials

Kovar (the bottom of a TO-package) is 5.9
Silicon is 2.6
The big advantage of a TO-package is that the PCB stress is decoupled by the wires.

with best regards

Andreas

floobydust:
I was thinking of thermal properties between the PCB and LCC, and any advantages of the LCC package beyond the hermetic seal.

LCC ceramic material I find Kyocera A440 CTE 7.1 and thermal conductivity 14.0 W/mK, Young's Modulus 310.
So it is quite rigid and an excellent conductor of heat. CTE is greater than Kovar by a little. FR-4 CTE is 13-17 and I have no idea how much stress is on the IC package after reflow, if it's significant. Ceramic is very stiff.

A reference with on-die heater i.e. ADR1399KEZ "The heater power for the LCC version is about 3× to 4× greater than the TO-46 version." They could probably use the LTZ1000A die attach technology if they weren't lazy.

So it seems a REF54 in LCC would only benefit from the hermetic seal against moisture, and see much less package flex and die stress from that?
I remember a product SOIC-8 op-amps that had huge offset shifts when the PCB was flexed, it was a nightmare in production to calibrate.

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