Electronics > Metrology

SMD ADR1399 (LM399)

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branadic:
Isn't it scientific practice to transfer experience from a non-heated reference A in LS8 package to a heated reference B in the very same package? And since there is experience but also some numbers given for reference A in LS8 package it is valid to assume very similar results for reference B in the very same package.
ADR1399 in LS8 though has its right to exist, it might be intended for precision application on automated SMD assembly lines, but it will probably not be good enough for metrology use, which calls for the TO package. ADI can prove me wrong on that.

There might be some workarounds to cover the well know issues of strain transfer from the PCB to the ceramic SMD package and from there to the die itself, such as Flex PCBs or Rigid-Flex PCBs, with the ceramic package sitting on the flex part. But even then the heat transfer of such a ceramic package calls for a pretty well insulating die attach. I wonder how ADI addressed that challenge on ADR1399 but also ADR1001. Hopefully we will know soon.

So let's differ between precision vs. high precision, high precision vs. ultra-high precision or ultra-high precision vs. metrology use and call it a day :)

-branadic-

macaba:
Haven't seen any mention of die attach in this thread - will a flexible die attach and bond wires isolate SMT package stress from the die?

Also - PCB slots are usually voltnut voodoo, but in this case might help reduce package stress?

We could really do with a lot more data on both points.

Edit: I'm amused branadic mentioned it at the same time as me.

branadic:

--- Quote ---Haven't seen any mention of die attach in this thread - will a flexible die attach and bond wires isolate SMT package stress from the die?
--- End quote ---

That is sort of challenging. During wire bonding you don't want the die to move, as you introduce heat and ultra-sonic to the die and bond wire. A moving (flexible) die would make that pretty hard of a job.
I'm not aware though of a die attach that has shear viscosity properties; that can be made flexible after wire bonding or that can be removed somehow after the wire bonding process to have the die floating, since we all know that air is the best insulator, right?

Edit: macaba probably meant flexible SMD assembly, not die attach.

Edit2: I do not recommend the use of ICA (conductive adhesives) as they are prone to humidity and their CTE is pretty large, worsening the issue of strain transfer even more.

-branadic-

macaba:
I meant die attach. This is a problem to be solved at the source, not by voltnut wizards of the internet!

KT88:
With the die attach compound used in the LTZ100A (400°C/W) the heat transfer into the PCB would be still reasonable. A heat spreading (GND-) layer under the package would reduce both absolute temperature as well as thermal gradients. Last but not least a ceramic package won't require Kovar...

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