High density boards with gold plating for inner layers

[Jane.Z]

Are there any high density Boards with gold plating for inner layer while immersion nickel gold for out layers

1.Why we need this ?

2.How to ensure good reliablity in Manufacturing ?

 

[(*steve*)]

This sounds like a homework question (or spam -- just kidding, eh?)

Is it homework? If so, what do you think might be the answers? Maybe someone here can help.

If it's not homework then perhaps you need to be more specific. Do you have a particular problem?

 

[Jane.Z]

Question on high density boards

Hi Steve,

It is not a homework or a Spam ,I post here for some advices on PCB design or fabrication process.

It is a 8 layers PCB with high density Circuit 4 mil /4 Mil ,and BGA In it . As per
clients requirement ,We need plating gold for all inner layers ,(2-3-4-5-6 -7layers ) while
Immersion Gold for out layers (1 and 8 layers ).

The question is : Why we need plating gold for inner layers ,Will it influence high density Circuit design ?

Hope it is clear now ,Welcome more advices from all of you.

This sounds like a homework question (or spam -- just kidding, eh?)

Is it homework? If so, what do you think might be the answers? Maybe someone here can help.

If it's not homework then perhaps you need to be more specific. Do you have a particular problem?

 

[CocaCola]

The question is : Why we need plating gold for inner layers ,Will it influence high density Circuit design ?

I believe the short of it is that it's per clients requirement as you stated... Now the question of why they want that is likely best left to them, it could be for something as simple as an advertising gimmick, all the way to an anal engineer that feels it's necessary for whatever reason, and some where in the middle where they have a valid concern based on whatever criteria...

IMO it's likely overkill but they might very well have a valid concern... IMO you generally gold plate to slow down oxidation and corrosion and provide a nice conductive surface, but I don't see much need for this while encapsulated in the PC board substrate... I'm also of the opinion that no matter how strong you make the chain the weakest link is the failure point, thus you can gold plate all this stuff but if you use traditional solder and components that are not gold you are right back to page one with the weak link...

But, those are my opinions not your clients...

As for how to ensure a reliable manufacturing process, that is really a loaded question... The short of it you have to trust your manufacture to do a good job and follow your specifications... Or you can invest a ton of money and resources into taking the product apart and verifying they did a what they where supposed to...

 

[Harald Kapp]

I have never heard of gold plated inner layers.

 

[gorgon]

I've never heard about gold on inner layers before. On the outer layers it's common and necessaery when using BGA chips.

I don't know what you normally plate with on the inner layers, if anything other than copper, but the only reason to plate with gold could be a wish to reduce the build of whiskers from other metals, in a leadfree environment.

TOK