netneut
finishing.com -- The Home Page of the Finishing Industry
A website for Serious Education, promoting Aloha,
& the most FUN smiley you can have in metal finishing


Finishing.com has been free for 22 years,
but without net neutrality we could soon
cease to exist. Do us a solid, click on
the banner, and contact congress today!
HomeFAQsBooksHelpWantedAdvertiseForum
topic 3990

Solderability problems gold over nickel over copper


(1999)

We barrel plate some brass contact pins with 50 microinches hard gold over 100 microinches min. sulfamate nickel(non-brightened) over a cyanide copper strike. The plated part is required to pass a Solderability test per MIL-STD-202 method 208. We fail this test periodically due to De-wetting. The nickel bath is dummy plated continuously to keep down the copper, and has a carbon cartridge(10") running continuously, replaced every 3 weeks. The gold bath also is continuously carbon treated.

Can anybody provide some clues as to the possible causes for this problem and/or some good information source. Please note that the parts show excellent adhesion and pass nitric acid vapor porosity tests. Can organic contamination via a treated closed loop recycle rinse system cause de-wetting on nickel? Any help would be great.

David Muliyil
- Mesa, Arizona


(1999)

Hey David,

Your process (step-wise) is good. Let's look at the steps. The cyanide copper strike is the perfect first step for adhesion and sealing in the zinc (from the brass). But, the word strike means color (coverage) and not thickness. This step should be at least 50 microinches thick (measured at the thinnest point) to prevent the zinc from impacting the solder test. Organics in the plating solution at this point can also cause de-wetting (add carbon). Make sure that the nickel plating is thick enough 100 microinches plus 2x the standard deviation (about 130-150 microinches). In the nickel, continuous carbon treatment is a very good idea but one 10" tube changed every three weeks will not get the job done. Closed loop systems can cause a build-up of contaminates (both metallic and organic) in the nickel. Dummy plating is also a very good practice. Check your copper PPM (send out samples for testing) to be sure you have enough area and/or amps to remove the copper (from time to time get the parts up from the bottom of the tank). (You can test for de-wetting after each process by removing a few parts after each step to pin-point the problem). One last note: the carbon tube used in the gold bath can hold up to one oz of gold, so reclaim. And, the old solder also has gold in it, so send it out for reclaim (old solder and flux can be a (rare) source of de-wetting).

Regards,

Fred Mueller, CEF
- Royersford, Pennsylvania



This public forum has 60,000 threads. If you have a question in mind which seems off topic to this thread, you might prefer to Search the Site

ADD a Q or A to THIS thread START a NEW THREADView This Week's HOT TOPICS

Disclaimer: It's not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices


©1995-2017 finishing.com     -    Privacy Policy
How Google uses data when you visit this site.