Ask the Experts

James Wetherald
Ronatec C2C, Inc.

James Wetherald

Electroless Nickel Problem Solving and Related Applications

Q: I have been told that passivating 13-8ph material prior to electroless nickel plating will cause problems with adhesion. Is this true, and if so, why?

I am very familiar with electroless nickel plating over stainless steel. I have always passivated with HCL prior to plating. I would like to see a woods nickel strike used between passivation and electroless nickel plating. If you are trying to activate bare stainless in the electroless nickel tank, you will need to use an electrolytic start for a few seconds so the stainless surface will begin plating.

Date asked: 19 February 2013

Q: Can a gold pattern with isolated features on a ceramic substrate (Pd activated) be electroless nickel plated and pass tape test?

Please note that you cannot plate EN top of gold. Gold, like lead, is a poison to EN and it is not autocatalytic. Putting palladium on top of gold may make it plate, but adhesion will be poor.

Date asked: 19 October 2012

Q: Could you point me to a method for determining the % phosphorous in a thickness test panel from the electroless nickel process?

1. Analyzing phosphorus percent with ICP and AA are very inaccurate due to interferences and the form that phosphorus is in (phosphides). We have both seen very low and very high (chemically impossible) phosphorus levels from these methods.
2. X-ray analysis also gives inconsistent values due to the localized non-uniform distribution of the nickel phosphide complexes at the surface--meaning two local areas could have a higher and one lower phosphorus content, when the average of the Ni-P matrix is somewhere in between those two values.
3. All major EN suppliers have found that there is only one consistent way to analyze phosphorus percent. Using a spectrophotometer, the light absorbance of phosphorus is measured, which has a linear relationship to the percent of phosphorus in the deposit. This method is accurate and repeatable.

Date asked: 17 September 2012

Q: I am trying to find out the proper way to activate Thermcon 83 prior to placing part in an electroless nickel tank. Do you have any suggestions. The material is 25% copper and 75% tungsten. Thanks in advance!

I am assuming you are using a RoHS-compliant electroless nickel (doesn't have lead or cadmium)?

Tungsten can be tricky, and my experience has been limited with it when combined with copper. With that said, copper should act as a conductor once "set off" so I would suggest either an electrolytic strike (Woods) prior to your electroless nickel tank or electrolytically charging the electroless nickel by running negative current to the part and positive current to the solution with a small rectifier for 15 seconds (maybe less).

Just a quick note on electroless nickel over 100% tungsten: It should be activated with a diluted percentage of palladium chloride. We are not doing so here as we have 25% copper in the substrate.
 

Date asked: 04 January 2012

Q: We have a sink that is hand hammered copper, plated with nickel and brushed. We are experiencing a problem with the sink discoloring and turning black. It can be cleaned and polished, but the black returns. I understand this comes from a problem in the plating process. Can you help me understand that?

I have actually faced this exact issue in the past. (I am assuming that you are referring to electroless nickel when you mention nickel?) A great way to resolve it is by using an electroless nickel with a slightly higher phosphorous content.

It sounds like you are using either a low phosphorous or "low-medium" phosphorous electroless nickel on these sinks. What is happening is that the low pH(a.ka. acidness) of the water or tomato juice--or whatever else you are putting in the sink--is reacting with the low-phos of the electroless nickel, causing it to turn black. By increasing the phos content to over 7% you should be able to eliminate the problem. Either way, the plating process sounds fine-- you just need a bath with higher phos content.
 

Date asked: 10 August 2011

Q: We are having pitting/porosity issues with our high-phos electroless nickel process. After extensive testing, we found the pitting begins after 0.004" of deposit. This is a problem when we need to build up to around 0.020". I feel like we've tried everything. Do you have any suggestions on how to stop this?

Please check the following: pH, temp, ni concentration, and plating rate. Assuming that you are using a standard semi-bright, high-phos electroless nickel (like our 2500 process), I would like to see your temp dropped to 183°F, pH at 4.7, and nickel concentration at 100% of manufacturer’s recommendation. This will slow your plating rate, which will help increase high build without stressing the surface. We might even let the pH drop to 4.5 later.

It is also possible that you have contamination in the bath or in your pretreatment. Please check for nitric in the electroless tank with nitric test strips (make sure they are not old). Also, shut off all agitation to the pretreatment baths (including rinse tanks), wait 5 minutes, and check for oil slicks at the solution surface. If you have oil, you will have pits. Try “spray rinsing” to avoid the rinse tanks and see if this helps as a test.

Also check your concentrations while plating. It sounds like the pitting is happening at around the first hour mark. Do you replenish while in production? If not, you are plating too much of the wetter out of the bath while plating. You should be replenishing while in production for thicknesses which require over 1 hour of plating. TIP: Make sure you add the “A” or nickel component first, then the “C” or hypo/stabilizer component.

If the substrate is aluminum: Are you using a caustic or acid-based etch? I would recommend an acid etch for most high build/high-phos applications to avoid porosity at the part's surface, which can lead to hydrogen “leakage” at around 1 hour of plating.

This sounds like something we can fix pretty quickly with a little brainstorming and trial and error testing in my lab.
 

Date asked: 27 April 2011

Q: What is the ideal post-plating treatment over high phosphorus EN plated regions ( apart from local removal of phosphorus) that need to receive tin-copper solders? Should region-specific bronze plating be tried?

A fluoride pickle is always recommended before soldering an EN coating. However, an RMA (rosin mildly active) flux will allow you to solder to any phosphorus type EN. Fresher plated EN is also preferred, if given the choice, to reduce oxidation of the nickel surface.
Hope this helps.
 

Date asked: 26 April 2011

Q: Hi Jim. My competition’s electroless nickel appears brighter than mine. We both use the same RoHS mid-phos bright EN, and my customers are requesting that I match the other guy’s brightness?

Assuming that both baths are the same age, your pre-treatment is also equal, and that you are operating at your electroless nickel manufacturer’s suggested optimum levels. I would advise the following:

1. Increase temperature to 191° F
2. Increase agitation (air or solution)

These should show an increase in brightness. If neither of these help, then contact your EN supplier and request an over-the-side brightener. While I HATE adding brighteners to electroless nickel tanks, sometimes it is the only option left.

Good luck and let me know how it goes!

Jimbo
James Wetherald
Ronatec C2C, Inc.
858-401-3374
 

Date asked: 25 March 2011

Q: Hey Jim, I recently spoke with a gentleman who claimed to achieve 12+ turnovers on aluminum. Is this actually possible?

Yes. By limiting the amount of zincate in your final electroless nickel tank, combined with “othro drag-out”, you will allow for greater turnovers over aluminum.

I would suggest an alkaline electroless nickel strike. It is inexpensive to operate and should double the amount of turnovers you currently achieve over aluminum (10+). This will increase adhesion and limit blistering.

While running a bath out to higher turnovers can save you money, it is important to look at some of the downsides. As a bath’s turns increase, hypo converts to ortho, which will increase brittleness. At a certain point higher rejects will cause you to rework parts, which can be a lot more expensive than a new electroless nickel bath make-up.

Weigh both options before you decide to go after that extra turn. While the EN strike will ALWAYS help, going after an extra turnover might open up a can of worms you don’t want to deal with.

Good luck and let me know how it goes! Please contact me if you need more information.

Jimbo
James Wetherald
Ronatec C2C, Inc.
858-401-3374
 

Date asked: 25 March 2011