Ceramic PCB Surface Finishes

ENIG - Electroless Nickel Immersion Gold

Usual thickness :Nickel 3 - 6µm, Gold 0.05 - 0.125µm
Shelf Life : 12 months

With PCB designs incorporating finer lines and micro vias the flatness issue of Hot Air Solder Levelling (HASL) can be an issue. ENIG is a popular alternative finish for small components, fine pitch and BGA. ENIG is also wire bondable.

ENEPIG - Electroless Nickel Electroless Palladium Immersion Gold

Usual thickness :Nickel 3 – 6µm, Palladium is 0.05 – 0.3µm, Gold 0.05 – 0.125µm
Shelf Life : 12 months

ENIG can give ‘Black Pad’ concerns on BGA. Black Pad refers to nickel corrosion on electroless nickel and gold immersion, (ENIG). It can occur when joints come under pressure and break to leave behind exposed corroded nickel, hence the name Black Pad.

ENEPIG is an upgraded version of ENIG and can defeat the Black Pad issue.

Palladium is added between the electroless nickel and immersion gold, ENEPIG results in containing a thin layer for resistance whose thickness usually falls in the range from 0.05μm to 0.1μm. The Palladium layer helps stop the immersion gold from corroding the nickel layer.

ENEPIG also has excellent wire bonding capability and reflow soldering capability.

Electroless Palladium / Immersion Gold (EPIG)

Shelf Life : 12 months

The EPIG nickel-free PCB finish proves advantageous for non-magnetic, high-frequency applications and designs requiring precise tracks and gaps. In the EPIG process, palladium is directly deposited onto the copper substrate, eliminating the use of nickel. This absence of nickel reduces the accumulation on the circuit, facilitating plating on small geometries and making it well-suited for applications with smaller features and clearances.

• Suitable for ceramics
• Maintains solderability and wire bonding ability to the copper
• No skin effect on low current, HF applications
• Non-magnetic
• No nickel to pose corrosion issues
• Ideal for fine track and gaps

Immersion Tin

Usual thickness :≥ 1.0µm
Shelf Life : 6 months

Immersion Tin offers excellent flatness making it ideal for small components, fine pitch and BGA. The process offers good solderability and a mid-range cost.

The main area of concern with the process are ‘tin whiskers’ and it is a aggressive to soldermasks meaning a larger than normal soldermask dam is needed. It is also is very sensitive to handling meaning gloves must be used.

Immersion Silver

Usual thickness :0.12 – 0.4µm
Shelf Life : 6 months

Silver has excellent conductivity and surface of silver is smooth and solderable, beneficial to signal transmission integrity. Like Tin, the flatness makes it ideal for small components, fine pitch and BGA. However, it is very sensitive to handling and can tarnish quickly meaning special packaging required and unused boards resealed quickly.