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