Ask the Experts
May 4, 2009
Nickel Barrier Thickness Requirement
What is the minimum nickel barrier thickness required when soldering to copper to restrict high consumption of the copper.
We are using a tin/antimony based solder with a reflow temperature at approximately 260 degrees C.
Expert Panel Responses
The the normal spec for Nickel thickness is 100 micro-inches minimum (39.4 microinches/micron). Normally the Nickel minimum thickness is done to ensure no Gold migration into the copper. The thinner Nickel also is more nodular and this is not good.
I have not seen any studies that look at aging etc. as a function of minimum Nickel thickness but I would refer to the specs on this. You might want to check with a couple of companies, www.superior-processing.com and www.eftcircuits.com as they have some good information on their websites.
Mike Scimeca created FCT Assembly after the purchase of Fine Line Stencil, Inc., and consists of two major operations: stencil manufacturing and the manufacturing of electronic assembly products such as solder paste, flux and solder bar.
The rule of thumb is no lower than 100 microinches and the nominal should be 150 microinches. It is ok for 200 microinches because electroless nickel barriers are sometimes hard to control and you see 175 to 200 microinches but as a general rule you will see 125 to 150 microinches.
The reason is you need to make sure the nickel is uniform across the board – pcb and that you do not see large swings in plating thickness across the board.
Same holds true for electrolytic nickel which is plated in an anode / cathode nickel bath. Again we want to see 150 microinches of nickel uniformily distributed across the board / pcb. This is a good safe plating margin.
VP Engineering Services
STI Electronics Inc.
Mark T. McMeen is STI Electronics Inc.Ê¼s Vice President of Engineering Services. He oversees the daily operations of the Engineering Services division of STI. He has over 18 years experience in the manufacturing and engineering of PCBs.
For nickel to be an effective diffusion barrier, the thickness of nickel is typically at 150 micro-inches.
Technical Manager - Europe
Currently with Indium Corporation and responsible for technology programs and technical support for customers in Europe. Over 15 yrs experience in SMT, Power, Thermal & Semiconductor Applications. Masters Degree in Industrial Engg, State University of New York-Binghamton.