Choosing Electroless Nickel Plating Chemistry

Electroless nickel (EN) can be a complicated, multivariable problem to solve for a plating shop. Many factors are needed to determine the correct bath(s) to run in order to accomplish the process goals. When it comes down to it, there are three categories that are the ultimate deciding factor: the deposit properties of the technology; tools and equipment necessary to run the solution; and the cost associated with the chemistry.

Deposit properties

Every supplier should have a list of deposit properties on its technical data sheet. Depending on the job and the application, some properties are more important than others. While some chemistries are specifically designed with one of these variables in mind, others try to excel at as many things as possible. Chemistries are commonly selected for properties such as alloy content and to the ability to provide desired melting points, hardness, density, salt spray performance (porosity) and electrical properties.

Consistency goes hand in hand with properties in a solution. It is imperative the chemistry is not different day to day and that, within all controllable parameters, the deposit is unchanging within tolerance. For example, the plating rate needs to be steady to ensure that thickness can be held to tolerance. Also, with thickness in mind, will the properties mentioned earlier change with thickness in a desired way? Common pitfalls (yes, that pun is intended) with thickness is that adhesion issues and inclusions on the surface will be a bigger problem with increased thickness. The alloy percentage, depending on the alloy, has been shown to vary with plating rate as the bath ages. Considerations need to be taken by both the supplier and end user to ensure this can be managed with addbacks.

Often, the correct procedure is the way one has been taught. If plating to a specification, there are hard limits on how things are run. It is critical to ensure the solution being used can be run in a way that is compliant with every specification that needs to be met. If this can’t be done across multiple conflicting specifications, there should be more than one bath. Sometimes this can be avoided with deviation letters from a supplier to run in a wider operating range.

Ultimately, vendor support is helpful when dealing with these concerns. It is best to ensure that everything that can be tested has a repeatable procedure and everything that can’t be tested can be handled via third party or by the vendor. This communication can make or break a relationship. Sample turnaround should be prompt, supply chain issues should be well communicated and data should be a two-way street because it is a partnership where everyone benefits from the plating shop’s success.

Necessary tools

As with every EN solution, equipment is needed to run the technology and people must be trained to use it. While a lot of the tools are universal across suppliers, some solutions are easier than others when it comes to the specifics. Factors to consider are the equipment itself, staffing requirements, mobility, contingency, and legal and regulation concerns.

The solutions of EN plate uniformly, however, they should be applied with certain geometries considered. Surface-to-volume ratios (bath loading) might be more important for some applications, and tanks should be sized properly for the work being run through. Some deposit properties can be affected by overloading or underloading baths. Solution volume must remain steady in a bath as well to keep the concentrations tight, and addbacks should be designed with solution levels in mind. Too much dilution of chemical addbacks can take up more space and overfill a tank if they surpass evaporation. Ultimately, chemistry needs to be safe to work around; chemicals must stay in the tank or be vented away from operators.

The way the staff interacts with the replenishment and testing of the EN bath is critical. Staffing considerations for the bath can include or exclude an EN application from certain available options. Dialing in an EN bath takes expertise and an understanding of how it works. A big selling point is the easy addback system of the 1-to-1 ratio for a nickel source and a reducer. Some have even condensed this to a single all-encompassing addback component. Having someone trained in EN chemistry is valuable when properties are not in balance and need adjustment. A standard operating procedure (SOP) cannot encompass everything that can possibly go wrong; therefore, it is necessary to have someone who can troubleshoot. EN control can also be implemented electronically.

The ability to move your solution is another potential consideration for your EN line. EN has come a long way in terms of stability but eventually, if left in a container for long enough, unintentional plating surfaces (plate outs) might occur, which make the solution mobility a valuable tool. Examples of bath mobility are the pump over from one tank to another, adjustments to chemistry to account for the plate out, and ways to bolster the stability or lengthen a bath life from unexpected decants (overflows). Vendors can offer products such as chelation, stabilizer or other boost chemistries to extend bath life or minimize production loss.

Contingency for EN solutions can help quickly identify and minimize problems associated with this technology. A vendor can help with some of these issues by providing an FAQ page or other guidance accepted by the industry. In this way, platers learn how to manage problems and fix them in a timely matter without having to stop and wait for help from the vendor for every issue.

Compliance with local, state and federal guidelines should not be taken for granted. The environment involving the laws and requirements for chemistries used in metal finishing processes is ever changing, and compliance with these regulations requires ongoing efforts. Because a lot of components in an EN solution are proprietary, it is crucial that vendors are equipped to answer questions about the unknowns in the solutions. Vendors may also be able to help with waste treatment and offer advice on how to get rid of spent chemistry.

Cost calculation

Pricing for EN is clearly an important choice to consider when choosing the correct solutions. However, understanding a quote and the costs associated with running the bath must be considered in the cost per gallon or liter received. I usually look at this last to make sure I have all the correct metrics in order correctly interpret the overall cost of running the bath."

Cost per mil-square foot (Mil-sq/ft.) is a common unit used for pricing a deposit with variable thickness. While the unit might differ depending on your preferences, the outcome is always the same. How much does the solution yield in surface area “x” thickness. This can also be thought of as deposit volume. An understanding of the deposit and how it is formed from the metal source and reducer is required to calculate this number. Consider that the yield of a deposit is dependent on the material in the bath itself. For example, a 6 g/L bath will have twice as much yield potential as a 3 g/L bath for the same volume of working solution. This doesn’t always mean that concentrated bath is less expensive though because addbacks will take more chemistry per metal turnover (MTO). Will running at 3 g/L double the MTO? This is why the Mil-sq/ft calculation should be used when considering cost. A vendor can supply the cost of a Mil-sq/ft and expected bath life.

The cost of quality for running EN is something no one enjoys dealing with. Does running a bath to 12 turns instead of 10 turns really save you money if it causes a reject occasionally? Pushing baths to an MTO has diminishing returns the further it is stretched. Depending on how expensive the makeup is, this might be more or less than expected. It is useful to run Mil-sq/ft calculations for 10 versus 12 turns to understand how much less that deposit costs. Identifying and fixing the causes of problems can reduce cost of quality and increase time pushing work out the door. Working with a vendor on failures can be a big selling point for the actual cost of doing business. Service does have value.

The importance of throughput is a consideration for the price of the solutions. It is no secret that getting more work done means making more money if all other factors are equal. If an EN tank can stay full of parts and it truly is the bottleneck of an operation, saving 10% on chemistry to do half as much work isn’t doing anyone any good.

Bottom line

If the goal of the process is to ultimately make the company more money or produce more parts for the operation, all the factors mentioned affect the bottom line of the company’s profitability in one way or another. Cost of chemistry, cost of operation, overhead and the ability to sustain it through a changing environment all can be affected by choosing the correct solution.