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Use of back titrations and maintenance of a dedicated lab help assure the results of your bath analyses. Photo courtesy of Midwest Finishing Inc.
When it comes to man agement styles, there’s a fine line between too much and too little. The micro-manager has a tendency to miss the big picture, while the laissez faire manager discounts the importance of detail. Either way, these managers often miss the target, which is optimal performance.
This is not an endorsement of the micro-management approach, but platers must be consistent in their approach to operating their electroless nickel lines. If they pay attention to the details, the payoff will be improved performance and reduced costs—ultimately hitting the target, improved profits.
The following are 12 low-cost (or, in some instances, no-cost) tips that can radically improve your overall EN operations—and your bottom line.
1. Perform back titrations of your reagent-grade chemicals.
In a plating shop, common reagent chemicals are analogous to the micrometers and other gages operators and quality personnel might use to check critical part dimensions in a machine shop. They help calibrate and control your electroless nickel bath. But EDTA, sodium thiosulfate and iodine are unlike dimensional gages in that they inherently break down and become weak with age.
When wet analyses are inconsistent with your past experience, a simple back titration will help you determine whether your “gages” are working accurately. In the case of iodine, it takes 25 mL of sodium thiosulfate to bring 25 mL of iodine to a neutral endpoint. Any variance in this simple titration may be the reason for your inconsistent readings.
2. Use first-in, first-out inventory control—know your date codes.
In accounting, FIFO (First In, First Out) is a way to manage inventory, and it applies to your EN chemicals as well. Fortunately, it’s a simple concept.
Most chemicals have shelf life. As part of the receiving process, the person in charge of inventory control in your shop should always use the oldest product first to maintain consistent quality.
As a secondary note, do you know where to find the expiration dates on your chemistries, including your lab materials? Some suppliers use actual expiration dates, while others use simple codes to determine the age of the material. If you cannot determine the age of the material in the drum on your floor, it is imperative that you contact your supplier to make sure you are not purchasing material that may give you problems down line. In a worse-case scenario, you may have to waste treat your stock because it was not rotated properly.
3. Protect your work environment.
What do I mean by protect your work environment? Even with good ventilation, the electroless nickel process can be messy. Often, the work bench containing your shop tickets, control sheets, titration materials and other necessary items is in the same general area as the plating tanks.
Consistent use of protective lids, dedicated computers linked to the corporate mainframe, and separate labs adjacent to the plating operation will ensure a cleaner work environment and more consistent quality.
4. Use dedicated pumps for EN concentrates.
The cost of a bellows hand pump is $200, the cost of a drum cart with spout is $100 and the cost of cross-contaminating a drum of a concentrate containing LNS is priceless. Many job shops have been guilty of rushing and not properly flushing a pump of one chemical before pumping the next.
These shops find out that there’s a reason EN components do not come in one container. Mixing the nickel and hypophosphite components prior to use will prematurely break those components down. Inexpensive pumps or drum stands pay for themselves if they prevent even one such incident. And remember the old adage, “An ounce of prevention is worth a pound of cure.”
5. Accept training from your suppliers.
Obviously, EN chemistry suppliers want their customers to succeed. One thing this means is that, for the cost of your employees’ time and wage, you can receive hours of free training from your supplier.
This is truly a “win/ win” situation. Your company better understands how the product works, how to control it and how to optimize it, improving your throughput and quality. The supplier will, in turn, better understand your business. In the long run this will reduce technical service calls, which improves the supplier’s profitability.
6. Calculate the true cost of your filters.
Among famous quotes you hear from the field, two fairly common ones are: “We change the filter once a day,” or “We wash ours out and re-use them.” Over time, the filter bag has lost its meaning. It is a nuisance, it is costly, and what purpose does it serve?
To be blunt, it filters. Filters do not wear a watch, and they do not work a shift. Based on the amount of contaminants in your shop and on your parts, a filter may last days or only a few hours.
A standard 5-μm, 8-inch diameter polypropylene filter bag costs $3. The potential cost involved with rough or pitted EN coatings radically outweigh the minimal cost of changing a filter more than once a day. Change the filter when it needs to be changed, not based on time.
7. Don’t heat tanks that aren’t needed.
Common sense would say you use heat when you need it. The problem lies more in the thought processes of some production managers, as in, “We must be ready at all times,” or the old “throw on all the switches” routine when opening the shop. Not only are these approaches not cost-effective from an energy standpoint, but heated EN solutions that do not see work and are not fed fresh chemistry break down prematurely, lose their nickel/ hypophosphite balance and will be sluggish at initiation when they are needed.
A common excuse for this behavior is that tanks take too long to heat up. Review your tank volumes and pre-existing heating systems. The return on an investment made in more efficient equipment will be quick when balanced with reduced energy costs and more stable EN chemistry.
8. Control Your EN strippers.
The most neglected bath in any plating shop is the EN strip tank. Typically, these baths are made up, heated up and used up with little care or attention.
If this were any other bath, it would be subject to periodic titration, maintenance and control. There would be control plans, quality control checks and routine inspections.
Ask yourself a simple question: Why wouldn’t you control a bath that could potentially ruin thousands of dollars worth of parts, cost you valuable customer relations and eliminate the opportunity to enjoy further business? The answer is simple. Control and monitor the strip tank according to the technical data sheets provided by your chemical supplier.
9. Use deionized rather than tap water.
In an effort to save money, some platers opt to use tap water instead of deionized water. In some cases, this may even be OK based on the nature of the end use of the customer’s product, but the reality is that use of tap water will cause problems with the electroless nickel deposit.
Depending on the area of the country where your shop is located, tap water can contain organic and metallic compounds. Organic compounds include sulfur-based materials that can cause lowered phosphorus content in high-phosphorus EN deposits, nitric acid failures and cloudy and hazy appearances.
Metallic compounds such as calcium, lithium, and magnesium found in tap water form, in-situ, insoluble compounds with the orthophosphate byproduct of the EN plating process. These insoluble particles will cause shelf roughness and plate-out of electroless nickel solutions. The resulting deposit will be porous and have poor corrosion resistance.
The added cost of using DI water is, on average, $0.02/gal. Measure the costs of your electroless nickel chemicals against the small added cost of using deionized water.
The impact of that $0.02/gal in your overall costs is negligible compared to the cost of a defective product and the rework it creates. Are you saving pennies to lose dollars?
10. Perform regular fixture maintenance.
Racks and barrels have finite lives, much like an electroless nickel bath. Oils, greases and residual nickel from barrels can cause pitting and roughness in EN deposits.
Nitric acid or other pretreatment chemicals will leach from cracked protective plastic coatings on racks, creating a number of bath control issues. I strongly suggest routine stripping of EN buildups on fixtures in a segregated nitric acid tank.
Sharing the same nitric acid used in the pretreatment of aluminum is not advised.
11. Control your EN controllers.
As with any piece of equipment, the EN controllers should see scheduled maintenance and calibration. Viscosities of the replenishment chemicals will vary from drum to drum and are also dependent on the time of year. Calibrating the feed rates of your pumps is critical for the proper control of your electroless nickel bath.
Transferring replenishment chemicals to clear holding containers will make it easier to maintain proper chemical inventories and avoid running out of a replenisher, which will cause an imbalance in the system.
Periodically flushing the system with clean DI water will help avoid blockage.
12. Control your plating rate.
The speed at which your bath plates correlates directly to the amount of phosphorus in the deposit. In high-build applications—over 0.001 inch per side—bath plating speed will have a strong influence on deposit quality.
For thick deposits, use of high-phosphorus EN at a deposition rate of less than 0.0003 inches/hr will helpavoid roughness and pitting.
On the flip side, speed directly relates to the degree of brightness in the deposit for bright, mid-phos EN chemistries. In this instance, a slower bath typically will result in a duller deposit. By adjusting bath temperature and pH, you can control the bath rather than letting it control you.
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