Issue link: https://iconnect007.uberflip.com/i/1471044
18 PCB007 MAGAZINE I JUNE 2022 Carano: Again, Happy, it's about where the board is located and how it's going to be used. ink about the environment that it's going to be used in and the application, whether it's telecom, internet of things, harsh use environ- ment, military, aerospace, office, etc. Holden: Is there anything like ENIG that could be used for finger plating, or does it have to be electrolytic plating? Carano: I wouldn't put ENIG on my fingers, not at that price. None of the people I work with do it either. ey'll do it on BGAs or IC substrates when they want to do wire bonding and soldering, but not on fingers. Shaughnessy: Mike, we're seeing some young people finally coming into the industry now. What advice would you give young process engineers coming in who are starting off in plating? Carano: It's funny. I learned about plating in graduate school through a phone call from Happy. I was finishing my master's degree at 23 years old, and I was working in a lab, doing mostly metal finishing. Happy Holden called out of the blue and he wanted to know about this product of ours that he saw in a copper and brass mill in New England, which I knew plenty about. It was a peroxide sulfuric micro- etch, used to clean copper and brass. He asked, "How would this work on a circuit board?" Of course, I said, "What's a circuit board?" Next thing you know we had a product called Cobra-Etch that Happy had implemented throughout Hewlett- Packard's five or six facilities in those days. You know what's so exciting today? It's not just about surfaces of circuit boards anymore; it's plat- ing on glass and silicon wafers and with the palladium, you're using a truly elec- troless palladium; therefore you're catalyzing it and you're not doing a galvanic cell. When you have galvanic reactions going on, a lot of things can happen: liing the solder mask, trenching, creep corrosion where you exposed the copper underneath the solder mask, and if you're in a harsh environment, you end up getting what they call creep corrosion when it interacts with sulfur. at's why pure electro- less tends to have some advantages over the immersion coatings. Immersion coatings are within what you call galvanic effect, so a bat- tery cell, a very simple exchange reaction. Holden: In your estimation, what's the current use of tab plating of gold on fingers vs. ENIG on fingers? Carano: No, it's not ENIG anymore; it's still electrolytic nickel-gold. You need it for hard- ness. If you're going to use plug-in boards, and your boards are actually going to get plugged in, electroless nickel immersion gold is too so and you'll just rub the gold right off. You need electrolytic gold and it's got to be thicker and harder. Holden: I haven't seen an article about tab plat- ing in 15 years. ere are always a lot of articles about ENIG, so I was assuming that tab plating had dried down in terms of its usage.