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March 2002

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Subject:
From:
Jim Kittel <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 11 Mar 2002 12:01:12 -0700
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Brad,
Thanks for your inputs.  One thing I failed to mention was the non wetting
occurrs on the thru hole pads on the wave solder side.  I don't believe it
is a case of heat being pulled away into the planes because the solder wets
up the barrel of the thru hole pins.  It just won't wet to the land areas.
JIm Kittel

-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Monday, March 11, 2002 9:09 AM
To: [log in to unmask]
Subject: Re: [TN] ENIG AND NON WETTING


Jim,

Sounds to me like your non wetting issue is related to the connector thermal
planes.  I have seen this time and time again.  The culprit is always
thought
to be PWB, finish or connector, or assy process.  If you have luxury of
xsection of soldered connector (destructive) it will definitively show the
effect of planes on the solder wetting.  The only way to avoid this (if it
is
your problem) is redesign the I/O entry of planes to the connector by using
trace entry (verses thermal), reducing or eliminating same hit thermals on
same pin, reducing from four to two spoke thermal and or increasing OD on
thermal diameter.

As far as non wetting attributed to ENIG, we have not had a problem (never
say never), but I still recommend moving away from it (using Silver or Tin).
I differ in the upcoming IPC ENIG spec in that I prefer minimizing the
amount
of nickel to the 45-75 microinch thickness (and no high phos).  This compels
the user to FIFO or even better the JIT that has been discussed previously.
Mind you, I am not knocking gold but in the case of an issue [i.e. Moonman
dilemma] it is a nagging point of contention.

Brad

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