Blued solder joints [log in to unmask]" rel=File-List>
I have just experienced the same phenomenon currently.  We have been using the same solder paste for years and the same saponifier for the last few years.  A recent change has been the wash equipment.  The machine is complete "stainless steel" construction where as the older machine had "plastic" tanks.  The situation is that over the course of the last 5 to 6 weeks the chain in the new wash has been turning blue and most of the metal in the first rinse tank and nozzles and the final rinse tank and nozzles have picked up the blue coloration.  The 2 detergent zones have not picked up any color.  Does anyone think there is a plating condition occurring in the solution from any leakage current from heaters or blowers.  The costly material analysis on the "blue" metal chain link has been determined to be a tin/lead combination where the heaviest of blue has high oxygen content.
 
We have not experienced this blueing in the paste 7 years we have used this material until recent.  Any ideas.
 
Candace Garcia
Sypris Electronics
10901 N McKinley Drive
Tampa, Fl 33612
813-972-6786
 
-----Original Message-----
From: Maguire, James F [mailto:[log in to unmask]]
Sent: Wednesday, April 09, 2003 4:11 PM
To: [log in to unmask]
Subject: Re: [TN] Blued solder joints

Charlie,

 

In my former job (at Boeing) we supported a military customer and after converting from 1,1,1 to saponification they “noticed” an “increase” in blue solder on sn/pb eutectic solder joints (both SMD and PTH).  We spent a small fortune on analysis (surface chemistry, chemical extraction/FTIR, SEM, etc.) and found when all was said and done that the “blue” flecks were related to the laminar spacing of the “beta” phase (dark bands) in the alpha phase background.   Basically, their spacing was almost exactly the wavelength of blue light, thus white light hiting these portions of the solder joint essentially hit a structure that would reflect back blue light.  

 

I don’t have the final report (of course) but if you like you could contact Victor Starkovich at Boeing and ask him if they’re willing to share this info.  Was an interesting study.

 

You could reach Victor at 253-657-9125.

 

==============================

Jim Maguire

Intel Corporation

DuPont Site Environmental Lab

2800 Center Drive  MS DP1-107

DuPont, WA  98327

email:  [log in to unmask]

Ph (253)371-4065

Fax (253)371-5779

Pg  (888)341-8572

======================================

 

-----Original Message-----
From: Charlie Pitarys [mailto:[log in to unmask]]
Sent: Wednesday, April 09, 2003 12:56 PM
To: [log in to unmask]
Subject: [TN] Blued solder joints

 

What would be the cause of blue tint, hue, specks  etc to be visible on the surface of solder joints. Is it just alloy composition?

I have seen this in the past typically in high temp reflow /high lead alloy, copper lead frame devices around the die attach fillet.

Now it is being seen on a 63/37 alloy solder smt reflow.

It was not seen in the past, the cleaning chemistry is buffered to protect the metal etc. and has been in use for many years without seeing this phenomena!

Maybe if a crappy traditional high ph saponifier was used and the solder joint was dull and gray it would not be as noticeable?

Perhaps the copper is leaching to the surface from the tinned component lead or HASL surface?
My suspicion is that trace amounts of copper is present on the surface of the solder joint after reflow. That when exposed to reflow temperatures it picks up this bluish color.

Charlie

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