What are the parts that are fretting? Is it the machine parts or the PWAs being processed?
Ramon
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From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord
Sent: Wednesday, May 16, 2007 3:19 PM
To: [log in to unmask]
Subject: [TN] SV: [TN] AC Outlets in China
Dear P,
Fretting has nothing to do with wave soldering, as far as I understand.
I have spent lots of hours studying fretting on multiconnectors for aircraft equipments. Imagine a contact male pin mated into a female fork or sleeve. There is a contacting pressure, specifically rather high per sq unit. Now, when exposed to vibration, the metals may slide against one another, small increments, just microns. The friction heat in the matrix is so high, that you get millions of micro welds. These are cooled down in nanoseconds, fractured, reheated, fractured, reheated, and after millions of such events, the metal begins to change character, oxides and other microscopic products deteriorates the crystalline order, and the surface metal begins to fall apart by kind of fatigue.
Microscopically, it looks like corrosion, therefore the name fretting corrosion. I speak about gold plated beryllium copper or other metal concepts. Even tinned contacts are involved, but are less prone to fretting because of the more ductile properties. Fretting can be a very severe problem, can cause electrical discontact and catastrophic failures. This is my amateur explanation. I have a friend who disputed on fretting mechanisms, got her thesis, so I can perhaps give you more specific answer later.
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För P. Langeveld
Skickat: den 16 maj 2007 17:27
Till: [log in to unmask]
Ämne: Re: [TN] AC Outlets in China
Technetters,
Is there anybody who has experience with fretting/corrosion of metal parts in wave soldering by the use of lead-free (SAC) solder wether or not in combination of VOC-free fluxes?
P. Langeveld
Soft Soldering Processes
The Netherlands
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