Soldering Electroless Nickel plated components

A. It's not the nickel but the Ni oxide that is extremely difficult to solder to without using a very active flux. Aluminum can be soldered to if the oxide is first removed. Ni is used as a barrier material and is usually over-plated with Au, Ag, Sn, Pt, or Pd to create a good solderable or bondable surface. Ni is also used as a barrier material to keep materials from diffusing into one another thus creating un-desirable inter-metallics.

A. There are many metal finishing experts who read this site, however there may not be many soldering experts. Please contact the supplier of your solder and flux for help.

A. (1) more phosphorus, the worse for soldering EN, (2) try to go with electroless nickel boron instead of nickel phosphorus, (3) thickness has nothing to do with ability to solder in this case.

First of two simultaneous responses --

A. I agree with the above.

The best idea would be to use electroless nickel boron. The properties of dimethylaimineboraine enable successful soldering however the solution does not like plating thick coatings - about 6 microns per hour which is fine for you situation. I would point out that nickel boron is trickier to control then ENP due to its limited pH range.

Second of two simultaneous responses --

A. I fully agree with Jeffrey's answer. If the problem is the soldering, the first thing to check is the soldering procedure. There may be nothing wrong with the EN. So, his answer seems totally logic to me.

A. To add my two cents worth to the above, nickel boron is more easily soldered but using the right flux enables fairly easy soldering of low and mid phos deposits. This is something to talk about with the solder supplier. If they are technically proficient they should be able to supply the correct flux.

A. The correct answer is that EN-P can be soldered if the right flux is used. The type of flux is classified as acid containing. There are a number on the market. consult a supplier of solder and fluxes for the one that best suits your conditions. Organic acid fluxes may not be sufficient due to the head process after plating. Heating builds the oxide film that is making it difficult to solder. If mild wet abrading is possible, it is a good way to start, followed by an acid activated flux. Note Acid activated fluxes are feared by electronic devices makers because they often contain chloride, that, if not completely removed, may cause later corrosion. Sulfamic acid does a good job without the danger of corrosion.

A. It is not possible to solder to nickel or Electroless nickel deposits without removing the oxide layer. It is better to remove the oxide and solder in an ordinary atmosphere.

A. Indeed, what Mr. Baudrand pointed out is that you need to activate the nickel surface. Finally, you tell us there is no flux and it's inert atmosphere. Sorry, this will do nothing to the oxide on the nickel surface.

A. Why don't you try a PVD coating of copper-on -Nickel and solder normally. I have done this on glass on copper strips it should be easy, in fact you can PVD coat the solder it self on the substrate!

A. I am not an EN expert. I only tell you my only experience of soldering to EN on thick film substrate. My engineers and I had many problems of soldering (Sn63) on gold thick film substrate. We visited a precious metal plating business for advice hoping to be find a buffer zone between gold and solder. The owner of this firm, a plating veteran, suggested and put a layer of EN on our thick film substrates for a try. The plated parts looked very pretty. However, we found nickel was peeling off from the substrate when soldering (Sn63 type). If you found success, please share your results.

Good luck.

A. Gentlemen

I have seen this problem many times, you will want to use a low phosphorous electroless nickel plating, followed by a gold plating of about 100 micro-inches. The Gold should have no brighteners in it

Good luck

A. Hi, Juan. When other plating does not stick to nickel plating it's usually because the nickel is passive (has acquired a thin tarnish layer). Multiple layers of plating must be done at the same time or else special activation procedures are required before the next layer. Good luck.

Regards,

A. Hi, Bob. The lead and cadmium were not there to promote solderability, they were there to regulate the autocatalytic deposition process. Replacing them with other regulating chemicals to accommodate RoHS shouldn't effect the solderability. Always solder ASAP after plating.

Regards,

A. Hi Steven. Yes, nickel is solderable. For the benefit of readers who might otherwise misread, we note that electrolytic nickel (nickel plating) is a different process than the electroless nickel plating described here, and it deposits purer nickel. Watts Nickel and Sulfamate Nickel are probably the two most common plating processes. Sulfamate is probably slightly more solderable because of fewer organic additives.

Nickel plating baths in most countries are proprietary processes rather than something mixed together from commodity chemicals, and you can go to any plating process supplier for their technical data sheets for the processes they offer.

Regards,

A. Hi,
My suggestion is to give more than 5 microns thick Electroless Nickel; the solutions contain mid Phosphorus i.e., 7-9%.
I think your soldering issue will be solved with above process.

A. You can electroplate the nickel plated surface with selective tin plating at the tail side where you are trying to solder it or you can use the nickel sulfamate solution while plating nickel to provide better solderability.

The tin plating has better solderability instead of directly soldering on nickel plated surface but the issue with tin is it gets oxidised so try to apply some grease/conformal coating on the soldered part to avoid oxidising.

This type of plating is mainly used in automotive selective gold plated connectors. The tail side of terminal is coated with tin for better electronic component solderability.

So the sequence of coating in my case was --> base material+1.35 micron minimum Ni (nickel sulfamate)plating + 0.75 micron min selective hard Gold plating + 1 micron min. tin plating(tail/solder side)+ apply some grease/conformal coating on tin plated side after soldering to avoid oxidation.