Connecting with the Right Finish

Delta Electronics tried different finishes for its connectors, non-cyanide finishes, but it wanted to keep its customers happy...


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Massachusetts has tough pollution regulations. Ask any finishing company in the state. Delta Electronics, (Beverly, MA) is aware of this, yet it continues to use cyanide-plating baths, as it has since 1981. Why? "We haven't found anything that works better on our product," stated Rick Allard.

Delta Manufacturing produces hundreds of different connectors for the communications, military and other industries. The company is vertically integrated. The connectors are made from raw bar stock and are manufactured through to finishing at Delta. If the company doesn't have a connector to fit your need, it will work with you to design a connector that suits your application. Not only does Delta work with customers to develop the right connector, it also knows the right finish for the part.

"When my father, Nick Nikitas, founded Delta in 1955, he envisioned the company not only as an outlet for his creative and inventive energy, but also as an organization that would reflect his own work ethic and dedication," stated Diane Delaney, president. "We have worked hard to continue this commitment to on-time delivery, high quality and new product development. All of the elements that combine to produce total customer satisfaction."

Customer satisfaction is why Delta has stayed with cyanide plating baths. "We have tried non-cyanide plating baths, but we can't get the appearance that our customers demand. Even plating to mil-spec, which all of our plating is, the non-cyanide baths just didn't give us what we wanted for our customers," stated Mr. Allard. "Waste treatment really isn't a problem. We do cyanide destruct and drop the metals out and neutralize them. We meet the effluent limits without a problem."

Delta uses Technic's Orosene 999, a bright, cobalt-hardened 24-caret acid gold process in its rack and barrel plating operations. The process provides the connectors with a low-stress deposit and a hardness range of 130-200 Knoop. Using this bath, Delta is able to meet the specifications of MIL-G-45204C, Type and II, Grade C.

Gold is replenished by adding 1 Troy ounce of gold salts every 14 amp/hr. The brightener is added at a rate of 20 milliliters per ounce of gold added. pH rises slowly during operation, and the platers at Delta monitor it regularly. Operating parameters are outlined in Table 1.

The silver process, also from Technic, Inc., produces extremely bright, ductile silver deposits on the connectors. The finish has excellent wear resistance, which is important to Delta's quality control. Delta platers produce finishes meeting Federal Specifications QQ-S-365B, Type III. In the bath, silver metal is replenished by the corrosion of the silver anode; however, the bath is analyzed to ensure that the concentration is correct.

The bath also uses potassium cyanide and potassium carbonate. Potassium cyanide is monitored using a Hull cell. The potassium carbonate level rises as the bath is electrolyzed. When the concentration is greater than 8 ounces per gallon, Delta removes the carbonates and reconstitutes the bath. A Hull cell is also used to monitor the brightener level. Brightener is added (200 milliliters) after every 100 amp/hr of plating. See Table 2.

Tarniban 51 is used as an anti-tarnish agent on the silver-plated parts at Delta. Parts are immersed in the solution for 1-2 min at 80-120F. This is followed by a cold water rinse, hot water rinse (below 150F) and drying with warm air.

These precious metals are what make the connectors work. Nickel is plated first onto stainless steel parts prior to gold plating. Beryllium copper and brass parts receive a copper strike to promote adhesion. Beryllium copper substrates all go through heat-treating and a bright acid dip prior to any plating. The bright acid dip removes the deposits left by the heat-treating process. Mr. Allard estimates that 80% of the plating done at Delta is gold. All contacts plated at Delta are gold. Teflon is used as the standard insulation on all connectors.

TABLE 1: Gold Bath Operating Parameters
  Range Optimum
Gold Metal 0.75-1.5 Troy oz 1.0 Troy oz/gal
Specific Gravity 1.09-1.15 (12-10 deg Be; ) 12 deg Be; minimum
Brightener 200-400 ml/gal 300 ml/gal
pH 4.0-4.5 4.2
Temperature 80-100F 90F
Current Density 1-10 asf 3 asf barrel/10 asf rack
Deposition rate 0.0001 inch in 26 min
Filtration Continuous
Agitation Filter pump, sparger, cathode rod
Anode: Cathode ratio 1:1 to 1:3
TABLE 2: Silver Bath Plating Parameters
  Range Optimum
Silver Metal 3.5-5.0 Troy oz/gal 4.5 Troy oz/gal
Free Potassium CN 16.0-18.0 oz/gal 14.5 oz/gal
Potassium Carbonate 2.0 oz/gal
Specific Gravity 12.5 deg Be; minimum
Temperature ambient < 80F
Anodes Silver 99.99% pure
Anode: Cathode ratio 1:1 or greater
Current Density 3-20 asf 10 asf
Deposition Rate 2.5 microns in 3-7 min
Agitation Cathode rod

Parts manufactured and plated at Delta range from delicate parts that are 50 thousandth of an inch in diameter with holes and slots that require complete coverage, to one-inch-sq flanges and larger that also require full coverage. Everything is manufactured from brass or stainless steel bar stock, often using equipment designed and modified by Mr. Nikitas. Apparently, Mr. Nikitas was well known for tinkering with and improving the machinery in his shop. "He would get an idea about a machine and work on it all weekend," noted Mr. Allard. "The machinist would come in on Monday, and there would be a sign on the machine saying 'Do Not Touch.'"

Mr. Nikitas' daughter, Diane Delaney, has continued with her father's commitment to machine enhancements by adding several million dollars of new CNC equipment.

Mr. Allard commented, "At Delta Electronics, we know that in order to best serve our customers coaxial connector needs, we have to keep up with the latest in equipment and processes. All of our operating systems are designed to enable us to provide the high quality, on-time delivery and connectors with electrical and mechanical performance that will help guarantee your product's success."

Ms. Delaney added, "But machines and systems only work as well as the people who control them. At Delta we have not forgotten the traditions of family ownership and New England craftsmanship that have formed the basis of our business philosophy since 1955. Every Delta employee uses these values to further our focus on providing the best in connector value."