By George Federman, Technic Inc. & Karl Wurst, AEP
Everyone in our industry is painfully aware of the rise in precious metal prices. This is especially true for the electronic interconnect industry, where precious metals are used to ensure stable and low contact resistance. Strategies to reduce their use include reduction of electrodeposited precious metal thicknesses, substitution of less costly precious metals and increased use of selective plating technologies to limit the precious metal plated area.
A major connector OEM approached Technic’s Advanced Technology Division in early 2011 with a request to eliminate/minimize the nanoporosity it saw in all of its plated gold deposits (some from Technic, others from various suppliers). Their theory was this nanoporosity was the primary cause of poor corrosion performance, as determined by nitric acid vapor testing (NAV), in connectors designed with low gold thicknesses in contact areas.
Technic subsequently developed an improved gold process, but testing showed only marginal improvement. Thus began an extensive research project into the interactions of the plated deposits that make up the modern day connector.
Lab findings showed that an entire suite of new processes—barrier layers, precious metal processes, and post treatments—could achieve dramatic reductions in precious metal thicknesses—50 to 75 percent—without performance compromise. Technic named this suite “Goldeneye.”
Connector manufacturers expressed interest in the Goldeneye products, but wanted to evaluate parts plated in an actual production line. Technic agreed, contacting several job shops with reel-to-reel selective plating lines, and American Electro Products (AEP) in Waterbury, Conn. stepped up to the plate.
AEP has a broad base of customers in the electronics, aerospace, automotive, medical, military and telecommunications industries. The company has always looked to innovative technologies, so installing the Goldeneye process suite into one of its selective reel-to-reel production lines made sense.
The Goldeneye suite of processes is broken into four categories:
- Goldeneye barrier layer processes, including Goldeneye Nickel, a low stress nickel process with excellent corrosion characteristics and high throw capabilities; Goldeneye Level Nickel, which has an additional leveling component to improve corrosion resistance and increase brightness over rough substrates; and NiPhos 611, a mid- to high-phosphorous electrolytic nickel sulfamate process.
- Gold processes, including TechniGold 800/900, a new nickel (800) or cobalt (900) hardened gold processes that incorporate pulse plating; and TechniGold 850/950 – new nickel (850) or cobalt (950) DC gold processes designed for flash gold applications that still require high corrosion resistance.
- Alternative precious metal processes, including Pallaspeed 985 PdNi, a neutral pH ammonium sulfate PdNi process with alloy stability, wear and corrosion resistance characteristics; and Durasil hard silver, a silver alloy process with excellent wear and low contact resistance.
- Post-treatment processes, including Auroguard NP-12, a solvent-based lubricant that provides corrosion protection without leaving an oily film on the parts; Durasil post treatment, a solvent-based lubricant that prevents galling during silver-on-silver wear, and protection against discoloration.
AEP’s line designated to run the Goldeneye process suite had the following processes, with rinses in between:
Soak Clean 1 → Soak Clean 2 → Electroclean → Acid Activator → Mild Microetch → Acid Activator → Goldeneye Nickel → Goldeneye Nickel with Leveler → Nickel Phos 611 → TechniGold 800 with Pulse → Selective Tin.
Testing by AEP, connector OEMs, Technic, and an independent lab all confirmed that improved barrier layers could substantially enhance corrosion resistance of the connector at low gold thicknesses. Most of the plated connectors had only marginal one hour NAV performance with 30 microinches of conventional “hard” gold plated over conventional nickel sulfamate. Yet these same connectors passed two-hour NAV testing with 0 to 2 pores with the Goldeneye process, and the contact resistance of the TechniGold 800 process is the same as for conventional Ni hardened gold.
Rougher and more porous substrates may require more gold to pass the NAV test. The GE Level Nickel will help reduce the amount of gold needed, but with rough substrates, it is recommended to use an electropolish for most benefit.
With lower gold thicknesses possible, OEMs were concerned about stability of the contact resistance after multiple mate/unmate cycles, both in the air and after MFG exposure. The results from plating several part designs in the AEP Goldeneye were excellent. Passing criteria for the change in contact resistance was 1 mΩ for parts tested in air and 3 mΩ for parts tested after MFG exposure.
Goldeneye processes have been running without problems for more than a year at AEP, and all customers report satisfaction with connector performance at significantly lower precious metal thicknesses. Results to date indicate that such reductions can be made for the majority of connector applications, and the savings will be just as significant.