x-ray is good tool to see if different location using different size  
of chip (chip shrink) or not - you might have different working temp  
range due to MFG process limitation.  Way back, one of the vendor  
provide chips at reduced temp range (different bin) for far east  
commercial usage, but main location process version got wider temp  
range and narrower parameters.  I order specified for main location  
only with 6month early notification with possible "last time batch  
buying" if MFG location change (pay extra for the clause).
- I was told un- officially, the difference due to less MFG of  
environment control (water, cleanroom, etc) and eliminate burn in  
steps with off shore location.
that is beside the counterfeit.  good luck.
jk
On Feb 9, 2022, at 1:44 PM, Wayne Thayer wrote:

> Greetings-
>
> The only way I've been able to keep parts moving in this  
> environment of
> part shortages and 72 week lead times is by constantly finding  
> substitutes.
>
> The least appetizing substitute option is offshore brokers. We are  
> revising
> our counterfeit detection strategy for minimizing cost/benefit (and  
> time).
> My inclination is to do careful visual inspections, especially  
> labels and
> lead finish, followed by solvent testing and a simulated Pb-free  
> soldering
> profile on samples of the lot. I also compare the decapsulated die  
> faces
> with known genuine parts.
>
> Is anybody else working this issue? Our old corporate document  
> suggests XRF
> and x-ray inspection, but I'm not seeing the value in those. XRF is  
> a great
> way to see if your system is Pb-free, but I'm more interested in  
> whether
> the leads were soldered to previously which a thorough visual  
> inspection
> should find.
>
> Thanks,
>
> Wayne Thayer