Excellent and important point. We did some FA on parts like this. A skilled hand soldering technician can make a very nice looking solder connection that has very poor or non-existent intermetallic. We infer that the intermetallic has formed by the appearance of the low contact angle and wetting, but wetting by surfactant is different from wetting do to "soldering". Well discussed in the text, The Mechanics of Solder Alloy Wetting & Spreading; Yost, Hosking, Frear. Van Hostrand Reinhold press, 1993. 


Guy

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Thursday, October 29, 2015 8:10 PM
To: [log in to unmask]
Subject: Re: [TN] No-wetting on Mini USB (Nickel plating)

Deng,
I suggest if you have the time, get the supplier to provide you connectors with a tin or solder plating already on the connection pins.  

About a decade ago almost lost my job over these suckers.  Told my boss that the USB connectors were bare nickel and he brushed it off and we had terrible field problems as a result.
Bev
Blackberry

Opinions expressed are my own and may not represent those of the company I work for.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Deng RongJun
Sent: October 29, 2015 3:33 AM
To: [log in to unmask]
Subject: [TN] No-wetting on Mini USB (Nickel plating)

Hi Technetters

I have got a problem with a SMT type mini USB connector. The four pins contacted shield are no-wetting after reflow soldering.  But can be solder well by iron.
The pins only plated by Nickel, is it possible the oxidation film creating on pin surface and then affect soldering? 

Picture:
https://goo.gl/photos/qap1CBEWzUEJEc5i6

Thanks in advance.
 
RongJun Deng


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