I am not an expert, but I believe you want to make sure your P level is between 4 and 7%. Here is an older link that can lead you to lots of other good papers on the subject. In addition, if you read through 4552 there is a lot of good information right there as well.

http://www.ipc.org/feature-article.aspx?aid=Black-pad


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Kelly
Sent: Thursday, November 08, 2018 1:27 PM
To: [log in to unmask]
Subject: Re: [TN] Immersion gold thickness per 4552

Thanks Ed,
If I do a SEM/EDX do you know what I should be looking for? Regards Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ed Hare
Sent: November-08-18 2:03 PM
To: [log in to unmask]
Subject: Re: [TN] Immersion gold thickness per 4552

Steven,

I believe it means that at higher gold thicknesses there is a higher probability of hyper-etching of the EN by the gold bath.

------------------------
Ed Hare
[log in to unmask]




> On Nov 8, 2018, at 7:03 AM, Steven Kelly <[log in to unmask]> wrote:
> 
> Hi all,
> Is it normal to obtain thickness readings of approx. 2.5 microinches of gold on large pads and 5 microinches on small pads across a panel ? What does it mean under paragraph 3.2.2 that higher gold thickness (>4.925 microinches) may compromise the integrity of the nickel undercoat?
> Thanks in advance. Steve Kelly