4 uinchs of gold on a 7 sq. in board =28 uinches of gold per board.
100 boards =2800 uinches of total gold dissolved into the solder pot per
month.
Assuming the client has a standard wave solder machine that can hold a
minimum of 1000 lbs of solder, and some drag-out is going to occur, he
can build 100 boards per month for the next ten years before his gold
content in the solder pot exceeds .00011 percent gold.

He will never have a brittle fracture using ENIG on through-hole parts,
unless his pwb design is subject to a tremendous CTE mismatch, in both
the planar axis as well as the z-axis.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Lazzara
Sent: Thursday, November 30, 2006 3:47 PM
To: [log in to unmask]
Subject: [TN] ENIG Risks

Dear TechNetters:

My company recently produced bare PCBs with ENIG finish for a client who
now wants HASL. I can't strip the ENIG and the routed PCBs are too small
for HASL processing (conveyor or dip).

Here's my client's concern:
1. ENIG will poison his solder pot.
2. ENIG will introduce risk of thru-hole component attachment failure

On the poison solder pot issue, my client will only assemble 100 PCBs
every 30-days. Each PCB has a total solderable surface area of 6.94 sq."
At an average measure of 4.05uI of gold I can't see the drag-in being an
issue of concern. The small amount of gold introduced to the solder pot
will likely be diluted into nothingness by solder replenishment across
the next 30-days.

On the embrittlement issue, virtually everything I find in the TechNet
archives (and elsewhere) concerns SMT designs and applications. Here
again the concern is with an all thru-hole design with no SMDs in the
build. If it's important, the nickel thickness averages 118uI.

Q1: Is there a real risk to solder pot poisoning?

Q2: Is there a real risk that PTH components are going to unplug due to
embrittlement?


Your thoughts and opinions are appreciated -

Robert Lazzara
VP, Business Development
Circuit Connect, Inc.

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