IPC 4552A outlines requirements for ENIG deposits (in IPC lingo, guidelines are guidance and not requirements). Within some of the items covered in the spec, some attributes are ‘if specified’, meaning that if the procurement documentation calls it out explicitly, then its required, and shall be performed as described in 4552A. An example of this can be found in section 3.6.1 where the paragraph starts out with the words “When specified….”. If the drawing says "ENIG per 4552A" only, it does not trigger 3.6.1, unless theres an additional standalone callout for 3.6.1 as well. This spec has evolved into one that comprehensively evaluates the deposit during lot conformance, and has further transitioned to where the statistical term in the Au thickness evaluations per Table 3-1 is prominently outlined; if all your thickness readings are at or just above the minimum, it may not meet the thickness requirements of 4552A because of the statistical term. The ENEPIG spec similarly applies statistical terms to deposit thickness evaluations.

But as Richard says, its perfectly alright to tailor the requirements to fit your own application, especially if you’ve developed your own acceptance requirements based on historical performance.


José (Joey) Ríos, Sr QA Engineer
Mission Assurance Manager
Kavli Institute for Astrophysics & Space Research
Massachusetts Institute of Technology
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(617)324-6272




On Apr 30, 2018, at 10:10 AM, Stadem, Richard D <[log in to unmask]<mailto:[log in to unmask]>> wrote:

I believe the standard is a guideline, but defined ENIG at that time with those specifications for thickness.
However, any company can put any specification they feel is appropriate for plating, plating thickness, etc, on their PWB fabrication drawing if they feel it is appropriate for the specific product and product use environment. This is usually handled AABUS. It can also be handled through the use of a deviation or waiver.
Your company's PWB fabrication drawing notes, assembly drawing notes, BOM, schematic, and any waivers or deviations take precedence over all other technical specifications, standards, etc, except for possibly legal requirements such as local environmental standards, etc.
So if you decreed .4 microns on your fabrication drawing, or if you allowed it as part of receiving inspection requirements and/or product MRT/MRB disposition, and the plating was in fact .4 microns minimum and not less, you were fully compliant to your own Technical Data Package. You did not ship anything that did not meet your requirements AABUS.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Showers
Sent: Monday, April 30, 2018 8:15 AM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: [TN] Interpretation of IPC-4552A (ENIG Thickness)

I am asking that anyone who is an appropriate authority on IPC-4552A to chime in on the new standard.

Clarification 1) The ENIG process min is still 0.5 microns (2 uinch) expect for the following exceptions:
1) An allowance in the Procurement documents (PO, fab prints/notes) down to 0.4 microns [ For that matter, I can write my fab documents to allow for anything ].

Clarification 2) I have always allowed for readings down to 0.4 microns when inspecting as to allow for process and measurement variation.  Previously this could have been rejected for by IPC-4552.  Is this now acceptable?  That is, is what I used to do out of necessity and to prevent rejection of usable product, now an allowance of the standard?