SURFACE FINISHES

The best surface finish for your PCB design

Background

A PCB's final finish protects the underlying copper from oxidation. It also ensures a sufficiently firm connection to components and logic chips via soldering, glueing, and bonding processes. Most frequently, chemical plating methods such as immersion Sn, ENIG, or ENEPIG/ENEPAG are used. These are characterised by a planar plating structure with a low layer thickness. Galvanic processes such as galvanic NiAu are frequently used if extra robustness is required (e.g. slider and plug contacts) or in the case of stringent corrosion behaviour requirements. These current-regulated processes have a higher Au layer thickness. The PCBs, with required current connections for the pads to be plated, cannot be designed freely.

Applications

  • Current-free and current-regulated wet chemical processes
  • Physical immersion process for tin plating from melt phase

Benefits

  • Copper corrosion protection and improvement of shelf life
  • Assurance of processability for subsequent assembly and connection processes such as soldering, glueing, printing, and bonding

Special features

In addition to the standard processes such as chemical tin or ENIG, new functional or more cost-effective alternatives can be created through the combination of individual layer systems. This must be checked on a case-by-case basis depending on the product, layout/design, processing, and application.

Surface finish

Layer thicknesses (µm)

Applications: Processability/
solderability

immersion tin

0.9-1.2

6 months

OSP

0.1-0.3

6 months

ENIG

Ni: 3-9
Au: 0,05-0,1

6 months

ENEPAG (ENEPIG)

Ni: 4-8
Pd: 0,1-0,3
Au: 0,03-0,08

6 months

ENIG + galv. Au

Ni: 3-9
Au: 0.1-1.0

6 months

Galv. nickel gold

Ni: 3-9
Au: 0.1-1.0

6 months

Galv. hard gold (99.7%)

Ni: 3-9
Au: 0.5-2.0

6 months

Leaded HAL

Covered – 45 µm

6 months

Lead-free HAL

Covered – 45 µm

6 months

Chem. silver (99.9%)

0.1-0.3
Performed by subcontractor

12 months