Hot Topics At the Wastewater Treatment Operators Forum Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 The Wastewater Treatment Operators Forum continued to be a popular activity at AESF COMPLIANCE WEEK ’95. Edited excerpts of some questions and answers from the forum that appear here reflect some of the current concerns in the industry. Thanks, and congratulations, to the panelists for another outstanding job. QUESTION: What types of treatments have you found that work most effectively on any of the streams in your plant that come in contact with the electroless nickel in terms of its complexing problems? Brad Crowe: We have a high concentration of copper. Our city ordinance is .7 ppm. What we had to do is go to a complete waste segregation of the effluents that come into our waste stream. We’ve set up a lamella clarifier in tandem, and will run the material twice, quite literally, to make sure we precipitate the copper to the necessary levels. That’s been successful for about 18 months now. Lyle Kirman: Most of the suppliers of electroless nickel do not have any strong chelators in them. They don’t have EDTA. They have lactic acid, some wetters and weak chelators, glucconates, etc. They’re not that difficult to treat by any of the conventional means, unless you have a low limit for nickel. There are a lot of people who have limits under 1 mg/L, in which case you might have to go to some advanced type of treatment, such as sulfides or carbamates. We’ve done things with ion exchange, as well. Borohydride treatments are also used occasionally on concentrated dumps. The chelators in the typical EN, while it is segregated for treatment, are not that tough to deal with as, say, electroless copper. Brad Crowe: In that tandem set-up, we have the ability to introduce carbamates at that point, as it passes through the second time, and that has been beneficial on occasions as well. *********** Hot Topics At the Wastewater Treatment Operators Forum Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 QUESTION: Is there a simple test by which you can tell when all the EDTA in your rinsewater has been destroyed? Frank Altmayer: Take the water sample, acidify it down to about a pH of two, add some calcium chloride, take the pH back up to about nine, see if it drops back out. If it doesn’t, you’ve got EDTA still in there. Tom Martin: One of the tests I use is to take the effluent sample and add dithalcarbamic to it, drop-wise. If you get a yellow precipitant, guess what? You’ve still got the complexing agent there. If it’s clear, you’re home free. Frank Altmayer: The test I was talking about can be done both quantitatively and qualitatively, if you want to sit down and make the calculations. Add a known amount of any soluble metal—take copper sulfate—add it, acidify it, then bring it up in pH and see at what level it drops out. Whatever is left in, you can go back and calculate the reaction between EDTA and copper and get a quantified answer as far as how much EDTA is left. Any of these tests would probably do. If you know the only chelate you’re worried about is EDTA, you can actually quantify it. *********** Hot Topics At the Wastewater Treatment Operators Forum Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 QUESTION: How do you remove copperfrom printed circuit board drag-out by the use of aluminum? The purpose is to ensure that you displace the copper onto the aluminum. Clarence Roy: This is the old “nail-in-the-copper-sulfate” from freshman chemistry. I’ve built these systems at 100 gal/min using scrap steel, which works great in a rotating reactor. You’ll take that copper out like a shot. The funny thing is, if you’re doing through- hole copper and there is quattro present, the iron is displaced in this copper substitution for iron. We tie up the quattro, so it doesn’t go downstream and get mischievous and start chelating your nickel or some other metal. It has a very high affinity for ferrous ions. *********** Hot Topics At the Wastewater Treatment Operators Forum Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 QUESTION: What are the limitations of DTC compounds as polishing agents? Tom Martin: From the practical point of view, you’ve got to be very careful using DTC as a polishing agent because it is a very strong carbamate-type pesticide, and there is no way to control it by pH or ORP—you have to do it stoichiometrically, which is an educated guess, for the most part. In Indianapolis a TSDF overfed DTC while treating nickel. The end result was it shut down one of the cells in the POTW. Another problem is, if you’re producing a sulfide-type sludge from the use of DTC, don’t try to dry it in your sludge dryer. It will catch fire and take off like a rocket. Frank Altmayer: I wouldn’t use DTC on stream discharge; you’ll never pass your bio-toxicity test. I also would not use it as an exclusive treatment chemical. In my estimation, it’s always used as a polishing step, so you keep the concentration very low. Lyle Kirman: One mistake a lot of people make by using it in an existing treatment system is that it’s a relatively slow reacting compound, compared to hydroxide precipitation. What you’ll commonly see happen is you’ll have browner solution coming out of your clarifier, thinking you’ve taken all the chelators out. If you let that sit overnight, you’ll see a film of very fine particulate that didn’t settle out in your clarifier that is still going through your system. It’s too fine to filter. Another problem is that it’s not cost-effective, for the most part. Unless you use it as a polishing agent, it’s real hard to compete against the sodium sulfide or sodium hydroxide with $20/gal DTC. *********** Hot Topics At the Wastewater Treatment Operators Forum Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 QUESTION: A number of companies are receiving F006 sludge as hazardous waste, and drying it prior to shipment to smelters. If you already have a dryer on-site, you can essentially do the same thing and ship directly to a nickel smelter. Can this be done? Tom Martin: If it is a raw material, it is not covered in RCRA. It is a hazardous waste in our industry, however, even though it may be considered a raw material in another industry. The RCRA rules need to be examined to see if there can be some changes to allow companies to treat certain wastes and ship them as raw materials where it is possible. Lee Martin: To be specific, all hazardous waste must be shipped with a manifest as a hazardous waste. Each facility providing a treatment must be a TSD. At the point where it is mixed with other treated waste, it would normally become de-listed, and from that point could be used as a raw material. Frank Altmayer: Most of the information we are discussing is related to federal rules. Be sure you know the state and local rules in your area. In many cases, the requirements are different. *********** Hot Topics At the Wastewater Treatment Operators Forum Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 QUESTION: I have a separate vibratory finishing operation that is relatively small—a few hundred gallons per day. Lead is showing up in the system, with no use of acid. We use alkaline cleaning compounds. We only finish steel, and are getting a half-ppm of lead. Where is the lead coming from? Lee Martin: Check your caustics, and your sources for obtaining them. You may need to switch to a different grade. Lyle Kirman: Free machining steel can have up to one percent lead. If you use material from the secondary steel industry, the lead is not as insoluble as you might think. Frank Altmayer: Of course, any tumbling operation creates fines. One percent lead is 10,000 ppm, so it would not be difficult to get a half-ppm in the water. *********** Hot Topics At the Wastewater Treatment Operators Forum Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 QUESTION: We recently stated .51 cadmium in the city water report. The limit was .50. We were cited. We were not fined, but were written-up. We were also cited in a separate incident with silver, and we did not know silver was regulated. Can you comment on this? Frank Altmayer: There is provision in federal regulations to petition for credit on any amounts that you are receiving in the incoming water. That does not mean you will automatically get the credit, but it can help to convince a local control authority that a close call may not be fair. Silver is regulated, and you must treat for it. Comment from audience: I’d like to comment on aquatic monitoring. In Connecticut, not only do we have aquatic monitoring on our regular discharge, we also have it on our stormwater discharges. It’s mandatory under law, and if you don’t catch the stormwater in a huge downpour at the last minute that it’s legally permissible, your test specimens will croak. Connecticut has had aquatic monitoring for a long time; therefore, a dozen or more labs in the state do aquatic monitoring. I strongly recommend that you evaluate these labs, and spend the money to send samples to various labs. They are growing their own bugs and minnows, and some of them are stronger than others. So much stronger, in fact, that the State of Connecticut tried to clamp down on one of the labs and was unable to find any problem. It’s not a joke, because if you fail the tests two quarters in a row in Connecticut you’re all the way up the pipe. You can find strong minnows and strong bugs, and you better look for the strong ones. ****************** 101 Ways To Make Pollution Prevention Work By James W. DeWitt Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 Abstract: Business and government pressures are affecting change in the environmental management practices of metal finishing operations. Some companies have discovered that costs can be reduced, productivity improved, and waste reduced through some simple changes in technology or worker behavior. Successful industrial pollution prevention programs are often unique, as companies adopt practices that make good business and environmental sense, yet basic concepts still apply to all industries. This article describes ways that a company with metal finishing operations can improve its environmental performance and business climate. PDF file: 01-04-95-33t39.pdf *************************** Enviroscope EPA Publishes Final Rule On Chromium MACT Standards by Dr. K.C. Yiin, Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 Abstract: The Environmental Protection Agency (EPA) has published the final rule of the National Emission Standards (or the Maximum Achievable Control Technology [MACT] Standards) for Chromium Emissions for Hard and Decorative Chromium Electroplating and Chromium Anodizing Tanks, in the Federal Register, pp. 4948–4993, Vol. 60, No. 16, Wednesday, January 25, 1995, which is the effective date of this set of standards. Owners and operators of all affected sources must understand the heart of the affected emission standards and the compliance dates triggered by these MACT standards. This article describes the regulatory obligations of platers with regard to the standards. PDF file: 01-04-95-58t59.pdf ************* FINISHERS' THINK TANK by Marty Borruso Originally Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 Good Rinsing May Help Eliminate Silver Tarnish Problems Question: We are in the reel-to-reel plating business. Silver tarnish (yellow and blue) are our major problems. What can be causing this and how can it be corrected? Answer: Silver is an interesting finish to apply, rinse, dry or store. It is subject to a variety of problems associated with atmospheric attack, accelerated by residue materials that are not rinsed from the surface because of inefficient and poor-quality rinsing. The best place to address this kind of problem is on the plating line, with good control on the plating processes and by using the highest quality rinsewater achievable. The best rinsing, however, may not mean the use of strictly DI rinsing, which could be aggressive if not handled properly. Silver is largely plated by the use of cyanide systems in order to deposit a uniform coating of silver. Residue cyanide on the surface of the silver deposit will cause discoloring and tarnishing, so good rinsing is a must to reduce or eliminate this problem—and to avoid the problem self- generating from the process. Finally, problems must be addressed that result after the parts are plated, and consequently interact with the atmosphere. Common practice is to use an immersion chromate to apply a passivated film onto the surface of the silver, so that is is more resistant to tarnishing and discoloring. I have found that the use of an electrolytic chromate will put a more resistant passivation film on the silver, as well as provide a greater protective film on the silver-plated parts. The use of a stock solution of either carbon disulfide or ammonium sulfide will provide a means of testing the silver surface for proper passivation. A known concentration of either material will allow estimation of the protective ability of the passivate on the silver surface. Exposure to this kind of material for a controlled period of time will permit projection of the effectiveness of the coating. ************* FINISHERS' THINK TANK by Marty Borruso Originally Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 Microfiltration/Ultrafiltration My thanks to Ken Lemke of Plating Systems, and Dereck Vachon of Waste Water Technology Center in Canada for much of the following information. Microfiltration/ultrafiltration (MF/UF) is similar to reverse osmosis (RO). The primary difference between these two technologies is the pore size of the membrane and the use of ceramic membranes on certain processes with circumstances of high pH. Although MF/UF is one of the newer technologies, a great number of suppliers “surfaced” almost immediately after the recognition of the usefulness of such technology. Applications range from removing oil from water (to recycle the water to the system), to filtration of electrophoretic paint (to remove oils and oil couples from alkaline cleaning solutions), which make for efficient methods of attaining a pollution prevention goal. Through the use of MF/UF, emulsified oils can be removed from alkaline cleaning solutions, thereby greatly extending the life of the cleaners from a few months to a few years. Cleaners can then be recovered and regenerated, and put back into the process tank for reuse. Cleaners generally become spent after the cleaner solution becomes loaded with oils, greases and solids. MF/UF will allow the system to be regenerated, and the cleaner, therefore, will cease to be part of the waste stream. This type of recovery scenario will save money by (1) preventing discharge and treatment of the spent cleaners, and (2) reducing the purchase of cleaners, resulting from the recovery techniques. Some problems that must be considered by the use of this treatment include: • A prefilter may be required to remove larger particulate, and • It may preclude the use of silicated cleaners that may form silic acid, which can bind off the membranes. These systems also may not address all of the organic oil/grease materials contaminations, and a preliminary study may therefore need to be done to determine the efficiency without buildup of certain deleterious organic species. In summary, MF/UF is only a weapon in the arsenal of pollution prevention. It should be used with intelligence and good preliminary assessment. It can demonstrate paybacks of investment in a very short time, or it may offer nothing but headaches. It is important to do the preliminary assessments properly—with the goal of zero discharge in mind—to see if this technique fits your operation. Editor’s Note: For more in-depth coverage of this topic, please see p. 40, “Microfiltration of Aqueous Cleaner Solutions,” P&SF, April, 1995. ********************** EPA Administrator Carol Browner: Committed to the Industry & to Building a New Generation Of Environmental Protection Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 Abstract: Administrator Carol Browner was the keynote speaker at the 16th AESF/EPA Pollution Prevention and Control Conference, which was held in Orlando during COMPLIANCE WEEK. Her presence there, as well as her continuing leadership in the Common Sense Initiative, represents a milestone in the long environmental journey that this industry began in the 1970s. EPA Assistant Administrator David M. Gardiner, who spoke at last year’s Conference and is coordinating the CSI effort involving our industry, was also present in the audience. Together they renewed their commitment that the EPA will work closely with the electroplating and metal finishing industry. Administrator Browner addressed the standing-room-only crowd of more than 600 industry leaders and professionals, commending their commitment to environmental protection as “a model for many other industries.” She also commented that, while touring the Exhibit Hall, she was impressed with the advances that have been made within this industry and by the hard work that is under way to produce high-quality products in the safest and most efficient manner. This article contains portions of Ms. Browner’s talk, including a question and answer session. Serge: use Common Sense Initative and CSI as key words. PDF File: 01.04.95.10t13.pdf ************************* How Crown City Plating Co. Spells Success: Teamwork Through Innovation, Communication & Environmental Leadership Crown City Plating Co. was formed by a husband-and-wife team back in 1911. It has since grown to a more than 450-person operation, with a strong reputation as a leader in process development and innovative manufacturing techniques, as well as plating and finishing of metal and plastic substrates. Here’s a look at what contributes to the company’s success. PDF File: 01.04.95.14t17.pdf **************************** Microfiltration of Aqueous Cleaner Solutions by Dave Peterson Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 This edited version of a paper presented at the 16th AESF/EPA Pollution Prevention and Control Conference, held February 13–15, 1995 during AESF COMPLIANCE WEEK, focuses on the fundamentals of aqueous cleaner chemistry and microfiltration. Basic surfactant chemistry is discussed to provide an understanding of how grease and oils exist in aqueous solutions. Various types of filtration are covered, with particular attention given to crossflow. Actual case study information is presented concerning the use of microfiltration at Modine Manufacturing Company in Racine, WI. PDF File: 01.04.95.40t44.pdf **************** Strategies at a Decorative Chromium Electroplating Facility: On-line vs. Off-line Recycling by James P. Lamancusa, P.E., CEF Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 The regulatory, as well as moral, obligations to prevent pollution, coupled with the desire to minimize long-term environmental liabilities, present electroplaters with a dichotomy of waste minimization and recycling decisions. Economic and technical restraints, however, usually prohibit recycling all residue materials generated from plating and wastewater treatment processes. Because there will always be a certain quantity of residuals generated in electroplating—hopefully smaller amounts as time goes on—it is more desirable from a long-term environmental standpoint to ship wastewater treatment sludge (EPA waste F006) to off-site recycling facilities, rather than to treatment/disposal (landfill) facilities. To conserve valuable natural resources (chemicals, metals, etc.) it is also important to maximize on-line recycling efforts whenever possible. To avoid creating a wastewater treatment sludge that is not marketable for metal reclamation, a careful balance must be maintained between various on-site and off-site recycling activities. The ratio and concentration of metals and contaminants in the sludge must be of a composition acceptable to the off-site recycler. Ideally, on-line recycling should be implemented so that the maximum volume of sludge is reduced, and any remaining sludge recycled, rather than sent to a landfill. --- This article is an edited version of a paper presented at the 16th AESF/EPA Pollution Prevention and Control Conference, February 13–15, 1995, and discusses on-site vs. off-site recycling strategies at a plastic parts chromium electroplating facility. pdf file: 01-04-95-46t50.pdf ************* Advice & Counsel Chromium MACT Performance Testing by Frank Altmayer Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 Following up on the last two columns covering the Chromium Emission Regulations under the Clean Air Act (CAA), any plater/anodizer that relies on equipment or foam blankets (not wetting agents) to comply must conduct an initial performance test to verify that the equipment meets the discharge requirements. The regulations require any plater/anodizer to make a plan available to the EPA Administrator upon request. Before conducting a performance test to be used as proof of compliance, it would be good to notify the control authority and the regional office of EPA that the test will be performed, and to have a test plan available for review. Such notification minimizes the possibility that the test results will be rejected or questioned. pdf file: 01-04-95-54t56.pdf ********************** Circuit Technology NiAu—A Solution To Industry/Environmental Problems by James P. Langan Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 In the ’60s, most of the multilayer and double-sided printed circuit boards were coated with a nickel/gold combination to serve as a metal etch resist, preserve solderability, and act as a contact surface. At that time, gold ranged at about $40/Troy oz. This coating eliminated a separate procedure for selectively plating contact fingers, and therefore, was comparable in cost to tin and tin/lead coating. When gold prices skyrocketed in 1972, this custom of processing PC boards was virtually abandoned. This method is currently being considered as a means of obtaining flat pads, which are essential for efficient attachment of ultra-fine pitch components. In resurrecting a system that was abandoned 20 years ago, one should investigate all reasons why other modes were adopted. Although escalating price of gold was the dominant deterrent, there were other drawbacks, including: • Sliver problem—caused by undercutting in the etching process; • Brittle solder connections—as a result of excessive gold thickness; • Solderability problems—resulting from a passive nickel prior to gold plating or from a thin, porous gold deposit. Gold Thickness Considerations For multi-heat cycle, gold thickness is an important consideration. Concern for the reliability of a solder connection initiates when the gold concentration is above two percent. In wave soldering, most of the gold dissolves in the solder bath. Before the concentration of the solder bath reaches dangerous levels, the solder is worth more as scrap and can be economically replaced. In solder fillets formed by fusing solder paste, all gold dissolves into the solder connection. Only thin gold coatings can be used to avoid embrittlement from the gold/tin intermetallic. A maximum limit for gold content in tin/lead solder, above which embrittlement is likely, is presumed to be somewhere in the area of two to four percent. For attaching surface-mount components by reflow soldering, some manufacturers maintain stricter guidelines as to a safe gold thickness when the end product will be subjected to vibration. Specification on gold thickness, therefore, will vary between 0.125–0.5 microns (5–20 microinches) for reflow soldering. With a gold thickness under 0.5 microns (20 microinches), all the gold will be dissolved in the fillet. To ensure solderability of the nickel, an activation procedure prior to gold plating is essential. Because porosity is usually present with thin gold thicknesses, an inert atmosphere could be necessary to guarantee solderability for multi-heat cycle applications. New Approach The nickel/gold electrodeposits used in the ’60s usually required at least 1.28 microns (0.00005 in.) to serve as an etch-resist metal, and to preserve solderability. This thickness also ensured dependable contact surfaces. To avoid the sliver and embrittlement problems, electroless deposits of nickel plus gold are being evaluated. A gold thickness of < 0.5 microns (0.00002 in.) is being suggested. If soldering is conducted in an inert atmosphere, a lower thickness is possible. Here are some of the advantages of this approach: • Lessens the possibility of barrel-cracking of plated through-holes as a result of thermal cycling; • Eliminates sliver problem; • Provides flat pads; • Permits wire-bonding; • Has no exposed copper; • Evenly distributs gold thickness, which can be easily controlled within the limits for avoiding embrittlement. Similarly, there are also some disadvantages that have to be considered: • Higher cost; • Possibility of solder problems; • Limited number of facilities capable of providing this process at this time. Unlike fused tin/lead, where solderability can be assesed by visual inspection, this process has the same handicap as organic coatings, in that there is no simple nondestructive test to monitor solderability. Conclusions The possible solderability problems can be minimized if the nickel is activated prior to gold desposition. Gold electroplating typically utilizes a gold strike to guarantee an active nickel. Because electrolytic activation procedures are not possible on etched printed wiring boards, it is suggested that acid cleaners—specifically formulated for activating nickel—be employed. This approach is gaining popularity in Europe, where there is insistent regulatory pressure to eliminate lead. Although it is a more costly process than inhibitor-type organic solderability preservatives, it has an advantage because the thickness of both nickel and gold are verifiable by non-destructive testing. Also, it provides a surface for attaching components by wire-bonding. no pdf ************************** Standards Topics by Allen W. Grobin, Jr. Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 The ASTM/ISO Specification Review Committee held its semi-annual meeting on February 14 during AESF COMPLIANCE WEEK in Orlando, FL. The committee is charged with fomulating AESF positions on standards/standards issues. Recently added to its duties is overseeing the administration of the ISO/TC 107 Secretariat. The committee reviewed the Secretariat management’s report and endorsed submission of it to the AESF Board of Directors. Also reported on was the status of a feasibility study for AESF, in which the Society may become a distributor of Metal Finishing Standards and Specifications. A second report was on a study of the feasibility of the translation into Spanish of ASTM Metal Finishing Standards and subsequent distribution of the translated documents. We welcome opinions from readers on this project. The Light Metals Finishing Committee wants to put together a complete handbook of anodizing standards, to include those by ASTM, ISO, AMS, SAE, the Aluminum Anodizing Association, federal government, military, Architectural Anodizers Council, Aluminum Extruders Council, Aluminum Architectural Manufacturers Association, National Coil Coaters Association, and Chemical Coaters Association. The standards would be in looseleaf form with regular update packages. If you have an interest in this proposal or want to add other standards, let us hear from you. Cancellation of MIL-C-26074 Attending COMPLIANCE WEEK was former AESF director and good friend Milton Stevenson, Sr., president of Anoplate. He alerted us to serious problems engendered by the cancellation of the Electroless Nickel Specification, MIL-C-26074, in favor of AMS 2404C, 2405B and 2433A. By the end of the week, I had three FAXes and seven phone messages concerning this subject. During my review of the specifications, I referred to an excellent paper (presented at the EN ’93 Conference) by Milt Stevenson, Jr., vice president of Anoplate, and Kurt Weamer, vice president of Imagineering Enterprises that compares the MIL, ASTM and AMS documents. For the most part, the AMS 2404 and 2405 documents are almost identical, with the exception of clause 3.4, where 2405 has a phosphorus content requirement not in 2404, and clause 4.3, where 2404 has an addition concerning the definition of a lot. When compared against the military standard, the AMS specifications are too vague and lack means of verifying important requirements, and therefore are ill-suited to replace MIL-C-26074. ASTM B 733 was prepared as a performance document; it clearly defines coating requirements and methods of testing for those requirements. The ASTM specification, B 733 (Autocatalytic Nickel-Phosphorus Coatings on Metals) is an outstanding performance-oriented standard. Along with B 656 [Autocatalytic (Electroless) Nickel-Phosphorus Deposition on Metals for Engineering Use], which is incorporated by reference, it provides for all the requirements of MIL-C-26074, while avoiding some of the MIL standards deficiencies. The AMS specifications are, however, good and useful documents, and are extremely effective when used with certain business operation strategies. All U.S. government standards and specifications are classified under a Federal Supply Class Number or Area Assignment four-letter class. Plating falls under the MFFP Area (Metal Finishes and Finishing Processes and Procedures), with administration assigned to the Army Materials and Mechanics Research Center at the Watertown Arsenal in Massachusetts. The MFFP Program was managed, until his recent retirement, by E.J. Clegg, who was an active member of ASTM B 08 and chairman of the ASTM Section on Government Specifications. Ed Clegg had reported, over the last several meetings, on the Department of Defense (DoD) efforts to improve its acquisition process and to accelerate the adoption of industry standards in place of military standards. The ASTM B 08 Committee was aware that cancellation of MIL-C- 26074 was under consideration and thought that ASTM B 733 was being considered as a replacement. Two of the calls I received on the cancellation were from European finishers (AESF members) performing work under NATO contracts. One of them suggested that, as chairman of the ASTM/ISO Specification Review Committee, I should contact the U.S. government to ensure that ASTM B 733 was included as one of the acceptable industry standard replacements. To try to resolve the problem, I first called the MFFP area at Watertown, MA. I found that the program was in disarray, and that the Center was considering giving up the program. I called Wright-Patterson Air Force Base—the custodian of MIL-C-26074—to locate the right individual with whom to discuss this. The “beneficial comments” statement in military standards contains an acronym to whom comments are to be addressed. MIL-C-26074, Revision E referred to ASD/ENES, which Wright-Patterson told me has changed to ASC/ENS. They referred me to Rosemary Farley, who told me that Tom Nagui had technical responsibility for MIL-C-26074 and Ret Bailey had administrative responsibility. Mr. Nagui was away for two weeks on military duty, so I spoke to Ms. Bailey, who explained the change process and why she could not make changes on her own authority. She referred me to Jay Free, chief of technical information, who directed me to Ron Williams, a laboratory manager. After a very fruitful conversation, in which we discussed having a respresentative from Wright-Patterson on the ASTM B 08 Committee, he had me call Lee Dulley, to whom Nagui reports. Dulley and I discussed the problem, and he agreed, based on the information I had provided, to rescind the cancellation of MIL-C-26074. I plan to continue the dialog with him and provide any assitance I can to provide a final resolution. As the DoD steps up its efforts to get out of the specifications business, we may see more of these unfortunate incidents. If any of you become aware of an impending cancellation, please inform me so I can review the impact on our industry. o ----- Correction to March 1995 column: The chairman of ISO/TC 107/SC 1 WG 1, on Surface Treatment and Coatings—Vocabulary, is R.W. Polleys, the working group convener. This group will meet June 27–28. no pdf ******************** Hands On by Mark Zahn Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 The Mettle of Metals, Continued ... After looking at nickel- and zinc-plated items in terms of their unique properties and applications (Salesmen would call these “features” and “benefits.”), perhaps it is easier to see why different types of baths and special tools are necessary to the finishing business. Let’s continue our study of some aspects of finished surfaces by discussing tin plating—a coating that can have distinctly different properties, depending on how the coating is applied and what type of bath is used. Tin is commonly plated from two types of baths: Acid sulfate or fluoborate tin and alkaline tin. Parts are usually plated with tin for “engineering” applications, because it is a good layer to put on a part if the substrate is not easily solderable, or if it would be damaged by fabrication operations before soldering. In this case, matte acid or alkaline tin is usually the bath that’s used. Bright acid tin is used where appearance of the part is important, but no soldering is required. Articles that come in contact with food can be safely coated with tin, although tin is rarely used to simply provide corrosion protection. Whiskers & Tin Pest In the most common cases, some sort of acid tin plating is evident. At one time, there was only the alkaline variety—commonly called “stannate” tin—which produces a very pure, matte tin deposit with some very interesting properties. For one thing, over time it can produce little hair-like growths of tin crystals called “whiskers.” These crystals are detrimental, because they can short-circuit an electrical system, like a circuit board, and they can grow to be more than 1/4-in. long. Part of the reason why whiskers grow on matte tin is that the deposit is so pure. Another problem is that these pure deposits can produce microscopic flakes, called “tin pest.” There is a formula for alkaline tin, using the same electrolyte (potassium stannate) that contains some bismuth, which will keep flakes from forming. Stannate tin baths require some special care to keep operating properly. The anodes must be “filmed” at the start of every processing run, so that the tin dissolves correctly ... one of those “valence” things. They also have to be zapped with about 40 amp/ft2 for a few minutes, after which they will look decidedly green. This is a sign that the tin is dissolving in the 4+ (stannic) 2+ (stannous) state. This is stannous tin, and doesn’t contribute to the useful tin metal dissolved in the bath. In fact, the deposit can become dark and spongy when too much stannous tin metal is in the bath. On the other hand, the alkaline baths are relatively inexpensive to operate and plate at decent speed, because the limiting current density is high. Unfortunately, the formulation that produces a bismuth-doped deposit is hard to control, so maintenance is touchy. Insoluble anodes are sometimes used to keep stannous tin from dissolving into the bath. Acid tin became very popular with the widespread acceptance of fluoborate tin plating baths. When this formulation hit the market, everyone claimed that acid tin deposits were immune to whiskers and tin pest. There are still, however, two schools of thought on that. It has also been said that bright tin deposits solder as well as matte tin—that just isn’t so. The grain refiners and/or brighteners used in the bright tin bath are deposited with the tin and cause big problems in soldering, because they try to “gas off” with the heat applied for soldering. The additives used for matte tin, however, don’t become occluded (mixed in) with the deposited metal, so soldering doesn’t cause any foreign matter to try to “escape” from the heat. Pros & Cons with Acid Tin Baths There are some important considerations with acid tin. First, the baths plate very fast because they plate tin from the 2+ state. This can mean real cost savings in labor, as well as increased production per/ft2 of floor space. Second, they are relatively expensive to run, because the two addition agents that are invariably used must be replenished regularly. Using acid tin does not resolve the problem with tin dissolving in the wrong valence state, either. Chloride is an anathema to stannous tin, and will convert stannous tin to the stannic form very readily. This results in a very milky tin bath where the stannic particles, which don’t dissolve, are so small that they can’t be filtered out. It’s a waste of money to allow this to happen. If you’ve ever made up a new sulfate acid tin bath, you know that you can see the bottom of the tank. If you can keep people from using muratic acid as an acid dip before the tin plate step in the process, the bath will stay that way for a long time. I prefer the use of electronics or PC-grade sulfuric acid for makeup and additions to the acid sulfate bath. Fluoborate baths are fine, too, as long as the boric acid concentration is kept high enough to preclude the formation of HF. One favorite application for tin these days is as a barrier coating over electroless nickel, when soldering is planned. Because nickel oxidizes very quickly, it is extremely difficult to solder. The recent introduction of “no clean” fluxes has made soldering to nickel a more common problem than ever. Nickel solders relatively dependably when resin-mildly activated (RMA) fluxes are used, but these aggressive fluxes are giving way in the marketplace to the less aggressive ones. A good coating of tin, therefore, is applied over the nickel to keep the nickel surface fresh. Despite appearances, when soldering a tin-over-nickel plated part, you really are soldering to the nickel. All of the tin melts at the solder joint, allowing the piece that is being joined to the part to bond properly to both the solder and the nickel undercoat. If the nickel were oxidized, both the solder in that area and whatever was being soldered to the part would not adhere to it. Typically, a matte tin deposit is applied immediately after the nickel plate. Of course, nothing is forever, and given enough time or heat, tin will oxidize—no matter how pure it is. If the oxide layer is too thick, even flux won’t remove all of the oxide, and the part won’t solder. It is important to recognize that there are limitations to any process, and if the job is not done properly, a failure may result. Be sure, then, that you clean properly, don’t use HCl as an acid dip before the tin if it can be avoided, and keep contaminants out of the tin tank. The deposit has to be pure if it is going to perform properly. Also, keep finished articles out of the corrosive atmosphere common in plating facilities. These are just common sense precautions to an informed plater—like yourself. no pdf *************** Pretreatment & Organic Finishing Chemical Pretreatment & Finishing—Part 1 by R.W. Phillips Jr. and R.W. Phillips III Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 Starting with this issue, a series dealing with chemical pretreatment and finishing will be presented in this column. This idea surfaced when someone asked about presenting some continuous, practical information, instead of summarizing specific incidences and activities. This series will focus on cleaning, rinsing, phosphating and finishing. We hope the information will be of some help. How Clean is Clean? Many years ago, the “Saturday night bath” was considered socially acceptable. Today, some people take a bath—or shower—in the morning, and again in the evening after work. Some people shower once a day, and some only once a week. Some are still known to take a bath in the creek! The question becomes one of convenience, necessity, and acceptability. Just how often and thorough should one bathe to feel secure around others without being embarrassed? If bathing does not remove soils, residues, or odors, why bathe? How many kids who play in the back yard all day during the summer can get clean in a tub of water? None. They will need some soap. How many will become clean with a tub of water and a bar of soap? None. They will need to use soap and water, followed by rinsing. If they rinse in the same water where soap was used, how clean are they? Cleaner, but fresh water must be used to remove the soap. To get really clean, the kids would need to use pure water to be free of some form of soil. Even fresh municipal tap water contains chemicals and salts, such as calcium carbonate, chloride, iron and minerals. These are dissolved in the water and do not normally settle out during the purification and filtration processes. A certain degree of cleanliness is needed to be socially acceptable, or to provide a feeling of security among family, friends and business associates. Isn’t that similar to cleaning for finishing? There must be a certain degree of cleanliness to be acceptable. “A surface is considered clean only when it is chemically clean, not just physically clean.” The Standards Have Changed In the past, there were cleaning standards that were acceptable in the industry. Most of those would not be acceptable today, because a business must be competitive, and comply with regulations. There is increasing demand to be more productive, efficient, and produce higher quality, while complying with environmental and health and safety regulations. Today, a surface is considered clean only when it is chemically clean, not just physically clean. The removal of soils (or dirt, or matter out of place) from a surface provides a useful and compatible surface. All objectionable soils and metal oxides must be removed or replaced by a more suitable surface condition to provide a physically clean surface. To achieve a chemically clean surface, however, the soils, oxides, blemishes and salts are removed, leaving only the base surface, or virgin material. Know the Part & Use the Correct Preparation Before a final finish is applied—such as anodizing, electroplating, electroless plating, porcelain enameling, chemical conversion coatings for painting, etc.—there are other important considerations. Examine the history of the part to be finished. What has really happened to it? What is the present condition of the surface? Those are prerequisites for establishing the cleaning section for the total process. Single cleaning stages are no longer enough. Today’s requirements—economics, productivity, environmental, and compatibility with the final finishing process— demand multiple stages of cleaning and rinsing. Because cleaning is the removal of dirt, or matter out of place, to provide a surface that is more useful or compatible for our needs, it is necessary to have the proper cooperation of all involved with processing parts before the final finish. We must, therefore, question the background of the parts to ensure that we have established a cleaning process that will properly prepare them for final finish. Next month’s column will discuss types of soils and cleaners. If you have questions, please direct them to the author, in care of AESF Headquarters, 12644 Research Parkway, Orlando, FL 32826-3298. o no pdf ******************* SVC Topics by Donald M. Mattox, Technical Director • Society of Vacuum Coaters Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 Substrates for Tribological Coatings Tribology is the science and technology of solid surfaces moving with respect to one another under load. Tribological coatings include ones used for wear resistance and abrasion resistance, such as those used for tool coatings. Wear and abrasion are typically inversely proportional to hardness—with fracture toughness, corrosion resistance, coefficient of friction, and adhesion between contacting surfaces also playing roles. The hardness of a material is measured by its resistance to surface deformation. If the coating is deposited on a rough surface, a “macro-columnar” morphology will be superimposed on the normal columnar morphology of atomistically deposited films, caused by geometrical effects, giving a less than fully dense deposit. If the film material is less than fully dense, it will compact under load, resulting in a lowered hardness value, as well as increased friction, wear and galling. Surface roughness and the angular distribution of the depositing vapor atoms are important in generating macro-columnar morphology, because of geometrical shadowing effects. It is best to have a smooth substrate surface to obtain a dense deposit. The ability of a hard coating to carry a load depends on the load, load distribution, mechanical properties of the coating material, and the coating thickness. If the coating is deformed by the load, then some of the load will be carried by the underlying substrate material, and the mechanical properties of the substrate become important. The Vickers (HV) or Knoop (HK) hardness measurements are made by pressing a diamond indenter of a specific shape into a surface, with a known force. The hardness is then calculated by using an equation of the form “hardness (HV or HK) = constant (HV or HK) x p/d2 (Kg/mm2),” where p is the indentation force, and d is a measured diagonal of the indenter imprint in the surface. Testing for Hardness Hardness measurements generally do not give much of an indication of the pdf file: 01-04-95-74t75.pdf **************** Gelatin Inhibition of a Silver Plating Process by O.A. Ashiru Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 This paper reports a study of the effect of gelatin (additive) on silver electrodeposition from an industrially viable iodide-based bath formulation. Gelatin is a grain refiner, as well as a leveling agent in the silver iodide plating system studied. The study is essentially an electroplating program whereby the electrode surface structure is related to the electrochemistry under well-defined experimental conditions, using a rotating disk electrode. DC polarization and in situ AC impedance techniques were utilized for monitoring adsorption and other surface relaxation processes. The resulting current-voltage curves and complex plane AC impedance spectra were used to elucidate the kinetic parameters of the additive-free and gelatin-containing silver iodide plating systems. pdf file: 01-04-95-76t82.pdf ************************** Effect of Electroless Nickel Plating On Fatigue Strength of 30CrMoA Steel by Y. Wu, Y. Zhang and M. Yao Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 The effect of electroless nickel plating on the fatigue properties of 30CrMoA steel was investigated by means of up and down load fatigue tests, scanning electron microscopy (SEM) and optical metallograph. The results show that electroless Ni-P alloy on quenched and tempered 30CrMoA steel decreases its fatigue strength by 39 percent, but that shot-peening before plating can increase the strength by 30 percent, compared with plating directly, and that the fatigue source appears almost at the interface between the coating and the substrate. On the coating, some parallel cracks vertical to the stress axis form after testing. pdf file: 01-04-95-83t85.pdf ******************** Electrodeposition of Nickel-Polytetrafluoroethylene (PTFE) Polymer Composites by G.N.K. Ramesh Bapu and S. Mohan Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 A nickel-fluoropolymer composite was produced by a technique using a Watts nickel bath containing PTFE in suspension. The effects of the PTFE concentration, the current density, the pH and the temperature on the volume percent of PTFE incorporation in the deposit were investigated. It was found that the PTFE content increased with PTFE concentration and current density. An optimum PTFE content (14.6 vol. percent) was possible by operating the bath at 6 A/dm2 at pH 3.0 and 50 C. pdf file:01-04-95-86t88.pdf ************ Electroless Gold Plating by Disulfiteaurate Complex by H. Honma, A. Hasegawa, S. Hotta and K. Hagiwara Orignially Published in: PLATING AND SURFACE FINISHING Journal of the American Electroplaters and Surface Finishers Society April 1995 Non-cyanide electroless gold plating, using a disulfiteaurate complex, is unsatisfactory because the complex is unstable and easily decomposes. Bath stability was improved by using Na2SO3, Na2S2O3 and nitrilotriacetic acid as complexing agents; the disproportionation reaction of gold(I) ions was suppressed by the addition of cupferron, bipyridine or Ni(CN)2 2KCN. The plating rate ranged from 0.7 to 1.0 µm/hr with sodium ascorbate as a reducing agent. The rate was increased to about 1.5 to 2.0 µm/hr with the addition of sodium ascorbate and hydrazine sulfate. Based on these results, gold wire bondability was evaluated. Gold crystal orientation was influenced by the wire bonding, and high bonding strength was obtained with (220) and (311) preferred orientation gold films. pdf file: 01-04-95-89t92.pdf