the pros and cons of pcb surface finishes continues
Figure 3: PCB with OSP/Entek surface finish.
layer of material over the exposed copper, usually using a conveyorized process.
It uses a water-based organic compound that
selectively bonds to copper and provides an
organo-metallic layer that protects the copper prior to soldering. It's also extremely green,
environmentally, in comparison with the other
common lead-free finishes, which suffer from
either being more toxic or consuming substantially more energy.
Advantages:
• Flat surface
• No Pb
• Simple process
• Re-workable
• Cost effective
Disadvantages:
• No way to measure thickness
• Not good for PTH
• Short shelf life
• Can cause ICT Issues
• Exposed Cu on final assembly
• Handling sensitive
Electroless Nickel Immersion Gold (ENIG)
ENIG is a two-layer metallic coating of 2–8
μin Au over 120–240 μin Ni. The nickel is the
barrier to the copper and is the surface to which
the components are actually soldered to. The
gold protects the nickel during storage and also
provides the low contact resistance required for
the thin gold deposits. ENIG is now arguably
January 2014 • The PCB Magazine
33
