SURFACE FINISH

Surface finishes form a crucial interface between the components to be mounted and the interconnection circuitry.

As its most essential function, the final finish process is intended to provide exposed copper circuitry with a protective coating in order to preserve solderability. In a more expanded view, the final finish coating is required to meet dozens of functional criteria, including solderability, environmental, electrical, physical, and durability demands. The past decades have brought about a wholesale transformation in this segment of the industry – a wide variety of functional, environmental, engineering, cost, productivity, and failure mode issues have contributed to this frequent change.

Nonetheless, years of manufacturing experience and constant innovation has enabled PCB International to be a leading edge provider for all your surface finish needs. Including, but not limited to: HASL, ENIG (Immersion Gold), Organic solderability preservative (OSP), immersion silver, immersion tin, Electrolytic nickel/electrolytic gold, electroless gold, etc. Below lists the pros and cons of a number of the more popular surface finishes – most relevant in today’s applications. We are pleased to offer all the above surfaces finishes at International Circuits.

Pros & Cons of HASL

ProCons
InexpensiveEnvironment Consequences
Cu/Sn solderjointPoor fine pitch assembly
Re-workableSolder bridging
Widespread availabilityPlugged PTH
Thermal damage to board
Not Flat
Thick intermetallics

Pros & Cons of Immersion Gold (ENIG)

ProCons
Pb FreeComparatively expensive
No copper dissolutionBrittle Ni/Sn solderjoint
Surface contactsSignal loss at RF frequencies
Long shelf lifeBlack-pad, black-line nickel
Strong PTH “rivet”Solder Mask “attack”
Fine pitch assemblyNot re-workable
Widespread availabilityComparatively complicated

Pros and Cons of Organic Solderability Preservative (OSP)

ProCons
Least expensive finishHandling sensitive
Flat, fine pitch assemblyPoor PTH soldering
relatively simple processShorter shelf life
Widespread availabilityDegrades with multiple reflow
Cu/Sn solderjointNo direct thickness measurement
Pb freeHigh surface contact resistance
High productivity at fabricationNot inspect able prior to assembly
Re-workableExposed copper on final assembly

Pros and Cons of Immersion Silver

ProCons
Flat, fine-pitch assemblyTarnish
Comparatively inexpensive finishAttack at solder mask interface
No PbDendrite formation
Re-workableExposed silver can corrode
Easy thickness measurementSolder joint microvoid history
Excellent surface contact functionalityHandling Sensitive
No degradation with multiple soldering reflow
High productivity at fabrication

Pros and Cons of Immersion Tin

ProCons
Flast, fine-pitch assemblyHandling sensitive
Comparatively inexpensive finishSolder mask attack
No PbCorrosion of Whiskers
FunctionalityDifficult thickness measurement
Multiple reflow solderingDegredation with time/heat
Less visible tarnishUse of thiourea
Reworkable
international sircuits
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