DP83848-EP: NiPadAuAg finish, Ag whiskers risk ?

Hi Pascal,

I understand your concern. Under the Ordering & Quality tab of the DP83848-EP Product Page, you can find the version of the part with the NiPdAuAg finish and see the material contents under the Quality, Reliability, and Packing information column.

Regards,

Alvaro

Hi,

Thanks for the quality section of the Part. I guess NiPdAu-Ag terminal finish is not prone to formation of silver whiskers but I cannot find this information in any TI documents. Could you help in definitively confirming that this finish is not concern for the formation of silver whiskers ?

Many thanks,

Pascal

Hi Pascal,

I'm an Applications Engineer that deals more with functional issue with our Ethernet PHYs. This would be more of a Product engineer question. I had a brief discussion with one of our product engineers who initially he agreed with you. After we checked the actual silver contents he said not to worry about it. Aside from that I don't have any other documentation to point to.

Regards,

Alvaro 

Hi Alvaro,

Thanks for your comments.

I understand no to worry about this finish but indeed we worry...

NiPdAuAg finish can be found on Infineon, NXP, Cypress product for a decade and it seems to be an industry common finish. However, we cannot find any litterature on this particular finish that indicates, silver compound will not be a risk for silver whiskers formation on the Leads. I expect Leads brazed with SnPb Solder will dissolve the AU-Ag alloy but the exposed area of lead (not brazed) will let the Au-Ag layer susceptible to environment. We know that sulfid gas or temperature or mechanical lead stresses could initiate the formation of silver whiskers in this case and the minimum lead spacing is only 9mils which fals under the 18mils limit of Lead spacing where the whiskers risk of creating shorts between leads is minimal. On the other hand, Silver plating is only 0.3% of the leadframe plating, but we do not know which is the limit of silver level to initiate whiskers.

Is there a post bake @150°C for this finish ? Could TI certify the silver level of the plating is controlled at production ? (0.3%+/- ?) 

Is there a return of experience of TI on this NiPdAu-Ag finish showing there were no whiskers concern from customers over years ?

Many Thanks!

Best regards,

Pascal

Hello,

Alvaro is OoO and will be back on Monday.

Sincerely,

Gerome

Hi Pascal,

The product engineer was not in today, please allow me another day to discuss this with him.

Regards,

Alvaro

Hi Pascal,

We are still working to getting you an answer. An internal email chain has been started to find the right person to assist on this. I will reply before end of day Friday March 15th with an update.

Regards,

Alvaro

Hi Pascal,

There hasn't been any updates, I am still pushing via email. 

Regards,

Alvaro

Hi Pascal,

Thank you for your patience. The feedback I received was that the Ag Whiskers are a valid concern if there is sulfide gas in the environment. That being said there are still versions of this part that does not use silver. 

Regards,

Alvaro

Hi Alvaro,

I assume this reply is a bit academic... Regarding the tests TI has performed on this kind of finish, it was not reported any whiskers formation in document "Assessment of Ni/Pd/Au-Pd and Ni/Pd/Au-Ag Pre-plated Leadframe Packages Subject to Electrochemical Migration and Mixed Flowing Gas Tests". However dentrite formation was not a big concern if the component is varnish coated.

Indeed, Au-Ag plating thickness is 0.005µm (5nm) only! and Ag is not an external layer but mixed with Gold: it is indeed a Gold/silver alloy flash whose mixture would not be prone to release whiskers. Otherwhise, it is nonsense to use expensive material in this which can contribute to other concerns!

I expect TI could provide more than an academic answer and as a main contributor in the electronics world could show ths finish would not require Sn/Pb Hot solder dip to mitigate whiskers risk!

Best regards,

Pascal

Hi Pascal,

I am not the expert regarding this issue. Do you have an Field Applications Engineer (FAE) you can contact over email so that they can direct you to the right person?

Regards,

Alvaro