Tell me more ×
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It's 100% free, no registration required.
up vote 2 down vote favorite
1

it is just a 8 layers PCB with min line 4mil ,6mil holes in a 10 mil pads, Can somebody tell me why we need gold plating for each inner layer while immerison nickel gold for all out layers.

share|improve this question
Never heard of gold inner layers. – user10238 Jun 10 '12 at 4:04
Yes, I know it is not common, so We don't know why we need gold plating for inner layers. – NancyZhang Jun 12 '12 at 10:47

1 Answer

up vote 4 down vote

Both inner and outer layers require gold as an etchant mask. The outer layers require nickel because the etchant chemistry is different. Difference of chemistry for inner and outer layers is caused by involvement of electroless step for holes walls plating. Typically, palladium is the starter for walls. I read this on the EPA site.

The dominating requirement after all is environmental impact of etchants.

share|improve this answer
Markrages, I viewed the link: EPA site, Thanks for your sharing . – NancyZhang Jun 12 '12 at 10:47

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.