ceramic cpu wires

[ebb]

Hello I am processing a batch of ceramic cpu's the ones with the lids on the underside, I brazed off the lids and soaked them in 50/50 nitric to drop the pins off before crushing but I noticed the tiny wires have also been digested on most of the cpu's, before the acid bath I also noticed there was a difference in color, some were yellow/gold while others were white-ish.
My question is are some of the wires made from a different metal, if so what will it be?

 

[lazersteve]

The white wires are Aluminum.

Steve

 

[ebb]

The white wires are Aluminum.

Steve

Thanks for that, got some silver out of the solution.