The Plating Forum: New Developments in ENIG

Electroless nickel immersion gold (ENIG) has been around the printed circuit industry for more than 25 years. The first version of the IPC-4552 ENIG specification was issued in 2002. Initially, the specification only addressed tin/lead solder; now, lead-free solder, like SAC 305 and its variants, dominate soldering in electronics. Although the occurrence of corrosion was recognized, a better understanding of the defect has led to a series of improvements over time.

Today, it is well established that Ni corrosion occurs in the immersion gold step, and the most important method for eliminating the defect is through process control. ENIG is a complex chemical process with multiple process steps, and each step must be completed successfully before proceeding forward. ENIG remains a very popular surface finish and offers a series of benefits at assembly: it is easy to inspect, has an extended shelf life, and is suitable for a wide range of assembly applications.

The IPC-4552 Rev A, issued in 2017, specifies the deposit thickness: nickel from 3–6 µm (120–240 µnis) and gold from 0.04–0.1 µm (1.6–4.0 µins). The upper limit for gold at 0.1 µm (4.0 µins) would require an extended dwell time in the immersion gold bath. The extended dwell time makes the deposit susceptible to nickel corrosion. The recommended immersion gold deposit thickness is 0.04–0.07 µm (1.6–2.8 µins). If a higher gold thickness is a design requirement, an alternative to immersion gold should be used for deposition. Two available alternatives are reduction-assisted immersion (RAI) gold and electroless gold.

To read this entire column, which appeared in the December 2019 issue of PCB007 Magazine, click here.

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2020

The Plating Forum: New Developments in ENIG

01-08-2020

ENIG has been around the printed circuit industry for more than 25 years. George Milad provides an update and explains how although the occurrence of corrosion was recognized, a better understanding of the defect has led to a series of improvements over time.

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2019

The Plating Forum: Update on IPC-4552 ENIG Specification Revisions

10-20-2019

George Milad's columns will cover PCB plating, IPC specifications, and more. In this debut installment, he gives us an update on the IPC-4552 ENIG specification, including Revision A and B.

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2014

The Plating Forum: Wire Bonding to ENIG

03-05-2014

The IPC-4552 ENIG specification was written in 2002, but the committee is currently updating and revising the document. The thickness of the immersion gold layer is being revised with the intent of reducing the minimum thickness from 2.0 µin to 1.6 µin. A series of studies were conducted to find out if this reduction is possible.

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The Plating Forum: ENIG and the Plating Process

01-07-2014

ENIG continues to gain market share due to its versatility in a wide range of component assembly methods including solder fusing, wave soldering, and wire bonding. The plating of ENIG is a complex multi-step process. Each process step is carefully designed and must be well understood and controlled to produce the desired end product. George Milad reports.

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2013

The Plating Forum: Wire Bonding to ENIG

03-05-2014

The IPC-4552 ENIG specification was written in 2002, but the committee is currently updating and revising the document. The thickness of the immersion gold layer is being revised with the intent of reducing the minimum thickness from 2.0 µin to 1.6 µin. A series of studies were conducted to find out if this reduction is possible.

View Story

The Plating Forum: ENIG and the Plating Process

01-07-2014

ENIG continues to gain market share due to its versatility in a wide range of component assembly methods including solder fusing, wave soldering, and wire bonding. The plating of ENIG is a complex multi-step process. Each process step is carefully designed and must be well understood and controlled to produce the desired end product. George Milad reports.

View Story
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