Introduction about PCB Surface Treatment of Hard Gold Plating

This Gold Phoenix PCB Knowledge Center article introduces hard‑gold plating as one type of printed‑circuit‑board surface‑treatment technology.

Surface treatment represents one of the critical manufacturing processes for PCBs. It forms an essential interface between electronic components and the printed circuit board. Fundamentally, PCB surface treatments serve two core functions: protecting exposed copper circuitry on the PCB, and providing suitable solderable surfaces for assembly workflows.

Hard gold plating (Hard electrolytic gold) consists of a gold plating layer deposited over a nickel barrier under‑layer. Hard gold delivers outstanding wear resistance and is primarily implemented for high‑wear locations such as gold‑finger edge connectors and keypad contact pads.

Hard gold plating differs from immersion‑gold finishes. Plated‑gold thickness can be adjusted by modifying electroplating cycle duration. For gold‑finger applications, IPC typical minimum requirements specify 30 u" gold over 100 u" nickel for IPC Class 1 and Class 2; 50 u" gold over 100 u" nickel for IPC Class 3. Hard gold is generally not specified for solder‑capable pads, due to high material cost and relatively poor solderability. IPC defines 17.8 u" as the maximum gold thickness still considered suitable for soldering applications. Where hard gold must be applied to soldering pads, a nominal thickness of approximately 5‑10 u" is recommended.

Advantages of hard gold plating

• Hard, durable contact surface

• Lead‑free material system

• Extended shelf‑life performance

Disadvantages of hard gold plating

• High manufacturing cost

• Requires extra dedicated processing steps during PCB fabrication

• More complex production workflow compared with alternative surface finishes

• Hard gold above 17 u" is not solderable.

Hard‑gold plating cannot be applied to isolated selective pads unless dedicated plating tie-bars are designed onto those pads to deliver electroplating current.