SEM Lab, Inc. uses SEM/EDS analysis to characterize ENIG finish quality on PWBs, as discussed here and here.  Examples of gold thickness values obtained in this laboratory (N = 14) are illustrated in the histogram shown below.  IPC-4552 suggests that the range of acceptable thickness is 0.0508 – 0.2032 microns, so 6 of the measurements exceeded the expected thickness.  This may be the case because some suppliers provided thin electro-plated gold in place of immersion-gold when the finish was specified as ENIG.



The phosphorus concentration in the electroless-nickel is expected to be 7 – 9 wt%, which corresponds with “medium phosphorus” electroless-nickel.  We detected one value below 7 wt% P, which can lead to corrosion of the electroless-nickel deposit during the immersion-gold plating process.  Values above 9 wt% P can lead to solderability issues during the assembly process.



Routine measurements of gold thickness and phosphorus concentration in electroless-nickel on incoming board lots is an important way to avoid costly processing problems at assembly and reliability issues in the field.  SEM Lab, Inc. has developed a cost effective approach to evaluating ENIG quality on PWBs.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes:

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

The reCAPTCHA verification period has expired. Please reload the page.