I agree. The term should be done away with. Nowadays, solder will "coat
over" many substances, but that is not soldering. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Thursday, May 26, 2005 12:03 PM
To: [log in to unmask]
Subject: Re: [TN] Wetting balance

Speaking of that, Werner, do you remember me? I was the program engineer
at Honeywell for the A-12 Flight control system in St. Louis Park, MN.
You came in in 1986 to help me find out why we had excellent wetting
characteristics of IC leads on a Cu-In-Cu assembly, but the solder
joints were fracturing. The problem was that we were soldering to gold
over nickel, and the nickel was heavily oxidized under the gold. This
was a classic case of solder appearing to wet over the pad properly, but
a good IMF never really formed, thus causing the "well-wetted" solder
joints to fracture in the saddle during thermal cycling.
Hi Richard,
Good to hear from you.
Sure do--and have had a problem with the unfortunate choice of the word
"wetting" ever since. For solder joints, 'wetting' does not mean
'wetting' in the hand-washing sense, but includes the dissolution of the
base metal into the Sn of the solder, the formation of intermetallic
layer(s), and the formation of a sound metallurgical bond. The choice of
the word "wetting" for this process has led to a lot of problems over
the years.
Werner Engelmaier

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