I think the first thing I would do is to determine what p
Chris,



I think the first thing I would do is to determine what part of the

component surface I was soldering to by running a trial and by doing

cross sections.  The trial would be to solder side by side a component

that had formed leads and one that didn't have formed leads.  I would

also cross section two other components (one with formed leads and one

without)before soldering to see if the soldering problem is due to the

fact that the forming process exposes nickel in the area that is being

soldered.  I'd also do a third evaluation and us an XRF to measure the

thickness of the Sn and the Ni on the component leads both before and

after forming.  It might just turn out that you're having solderability

issues because you're soldering to exposed Ni rather than matte Sn.



Regards,

George

George M. Wenger

Andrew Corporation Wireless Network Solutions

Senior Principal FMA / Reliability Engineer

40 Technology Drive, Warren, NJ 07059

(908) 546-4531 [Office]  (732) 309-8964 [Cell]

-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Schaefer

Sent: Friday, December 28, 2007 12:00 PM

To: [log in to unmask]

Subject: [TN] Hand Soldering Matte Tin over Nickel Flash with SnPb Alloy



Greetings All,



I have a PTH TK type resistor component that is formed to fit an SMT 

geometry land pattern. The component is Pb Free component plated using 

Matte Tin over Nickel Flash. Once the component is soldered it exhibits

non-

wetting/ poor wetting characteristics thus causing us to rework until we

have 

achieved acceptable results. Of course this is not what I would like to

see 

occur, but unfortunately at this time it is the process. The

installation process 

is as follows:



- Part is formed using a lead forming tool

- Is tinned using 25% RMA for 3 seconds and let to dry (somewhat); then 

soldered (SnPb tin/ lead alloy) for 3-4 seconds in a 600F bath

- It is soldered (SnPb tin/ lead alloy) to the cca using a 6ooF solder

iron tip for 

2-3 seconds

- END...



Apparently this has been an issue for years, but just recently was

brought up 

to our Engineering department. We tin the component to allow for

improved 

wetting characteristics, but this does not provide much improvement. I

have 

done some investigation on the internet looking for reports and tests  

performed soldering Matte Tin over Nickel using standard Tin/ Lead

alloy, but 

have found very little information regarding this. The component

manufacture 

states our process as described to them 'should work without issue, but

this is 

not the case.



So my questions are what are the issues related to soldering matte tin

over 

nickel flash with tin/ lead alloy? What hand soldering parameters are 

considered optimal/ ideal with a low-mass matte tin plated component 

considering the information provided? Is it possible to get very similar

results 

using this combination of metallurgies versus using tin/ lead plating

and solder 

materials?



Any help would be appreciated.



Thank You,



Chris



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