Dan's Biz Bookshelf: 'Apple in China: The Capture of the World’s Greatest Company'
The Chemical Connection: Experience and Wisdom Gained by Doing Business
It's Only Common Sense: Leveraging AI in Your Sales Strategy
ENEPIG: The Plating Process
June 1, 2015 | George Milad, Uyemura International CorporationEstimated reading time: 1 minute
Electroless nickel/electroless palladium/immersion gold (ENEPIG) is sometimes referred to as the universal finish, because of the versatility of its applications. It is a multifunctional surface finish, applicable to soldering and wire bonding (gold, aluminum, copper and palladium clad copper). In addition, it is also suitable as the mating surface for soft membrane and steel dome contacts, low insertion force (LIF) and zero insertion force (ZIF) edge connectors, and for press-fit applications. ENEPIG is formed by the sequential deposition of electroless Ni (120–240 µin) followed by 2–12 µin of electroless Pd with an immersion gold flash (1–2 µin) on top.
Chemical Definitions
Electroless Process: This chemical process promotes sustained deposition of a metal or metal alloy onto the PWB surface through an oxidation-reduction chemical reaction, without the application of an external electrical potential. Reducing agents, such as sodium hypophosphite or sodium formate, react at catalytic surfaces to release electrons, which immediately reduce the positively charged metal ions (e.g., nickel ions in ENIG and ENEPIG and palladium ions in ENEPIG), promoting their deposition onto the PWB.
This type of reaction is described as autocatalytic, as the deposition process will continue even after the substrate is completely covered by a continuous layer of the plated deposit. The deposit thickness will therefore continue to rise in the presence of source metal ions and a reducing agent, until the board is removed from the plating bath. The thickness of plated deposits will vary depending on the bath temperature, chemical parameters (such as solution pH) and the amount of time spent in the plating bath.
Immersion Process: This chemical process uses a chemical displacement reaction to deposit a layer of a second metal onto a base metal surface. In this reaction, the base metal dissolves, releasing the electrons that reduce the positively charged ions of the second metal present in solution. Driven by the electrochemical potential difference, the metal ions in solution (e.g., gold ions in ENIG or ENEPIG process) are deposited onto the surface of the board, simultaneously displacing ions of the surface metal into solution.
Editor's Note: This article originally appeared in the May 2015 issue of The PCB Magazine.
Share on:
Testimonial
"In a year when every marketing dollar mattered, I chose to keep I-Connect007 in our 2025 plan. Their commitment to high-quality, insightful content aligns with Koh Young’s values and helps readers navigate a changing industry. "
Brent Fischthal - Koh YoungSuggested Items
Trouble in Your Tank: Minimizing Small-via Defects for High-reliability PCBs
08/27/2025 | Michael Carano -- Column: Trouble in Your TankTo quote the comedian Stephen Wright, “If at first you don’t succeed, then skydiving is not for you.” That can be the battle cry when you find that only small-diameter vias are exhibiting voids. Why are small holes more prone to voids than larger vias when processed through electroless copper? There are several reasons.
The Government Circuit: Navigating New Trade Headwinds and New Partnerships
08/25/2025 | Chris Mitchell -- Column: The Government CircuitAs global trade winds continue to howl, the electronics manufacturing industry finds itself at a critical juncture. After months of warnings, the U.S. Government has implemented a broad array of tariff increases, with fresh duties hitting copper-based products, semiconductors, and imports from many nations. On the positive side, tentative trade agreements with Europe, China, Japan, and other nations are providing at least some clarity and counterbalance.
How Good Design Enables Sustainable PCBs
08/21/2025 | Gerry Partida, Summit InterconnectSustainability has become a key focus for PCB companies seeking to reduce waste, conserve energy, and optimize resources. While many discussions on sustainability center around materials or energy-efficient processes, PCB design is an often overlooked factor that lies at the heart of manufacturing. Good design practices, especially those based on established IPC standards, play a central role in enabling sustainable PCB production. By ensuring designs are manufacturable and reliable, engineers can significantly reduce the environmental impact of their products.
50% Copper Tariffs, 100% Chip Uncertainty, and a Truce
08/19/2025 | Andy Shaughnessy, I-Connect007If you’re like me, tariffs were not on your radar screen until a few months ago, but now political rhetoric has turned to presidential action. Tariffs are front-page news with major developments coming directly from the Oval Office. These are not typical times. President Donald Trump campaigned on tariff reform, and he’s now busy revamping America’s tariff policy.
Global PCB Connections: Understanding the General Fabrication Process—A Designer’s Hidden Advantage
08/14/2025 | Markus Voeltz -- Column: Global PCB ConnectionsDesigners don’t need to become fabricators, but understanding the basics of PCB fabrication can save you time, money, and frustration. The more you understand what’s happening on the shop floor, the better you’ll be able to prevent downstream issues. As you move into more advanced designs like HDI, flex circuits, stacked vias, and embedded components, this foundational knowledge becomes even more critical. Remember: the fabricator is your partner.