HASL – Tin/Lead hot air solder level
Typical thickness 1 – 40um. Shelf life:12 months

•  Excellent solderability

•  Inexpensive / Low cost

•  Allows large processing window

•  Long industry experience / well known finish

•  Multiple thermal excursions

•  Difference in thickness / topography between large and small pads

•  Not suited for < 20mil pitch SMD & BGA

•  Bridging on fine pitch

•  Not ideal for HDI products

LF HASL – Lead Free hot air solder level
Typical thickness 1 – 40um. Shelf life: 12 months

•  Excellent solderability

•  Relatively inexpensive

•  Allows large processing window

•  Multiple thermal excursions

•  Difference in thickness / topography between large and small pads – but to a lesser degree than SnPb

•  High processing temperature – 260-270 degrees C

•  Not suited for < 20mil pitch SMD & BGA

•  Bridging on fine pitch

•  Not ideal for HDI products

ENIG – Immersion gold / Electroless Nickel Immersion Gold
Typical thickness 3 – 6um Nickel / 0.05 – 0.125um Gold. Shelf life: 12 months

•  Immersion finish = excellent flatness

•  Good for fine pitch / BGA / smaller components

•  Tried and tested process

•  Wire bondable

•  Expensive finish

•  Black pad concerns on BGA

•  Can be aggressive to soldermask – larger soldermask dam preferred

•  Avoid soldermask defined BGA's

•  Should not plug holes on one side only

Immersion Sn – Immersion Tin
Typical thickness ≥ 1.0μm. Shelf life: 6 months

•  Immersion finish = excellent flatness

•  Good for fine pitch / BGA / smaller components

•  Mid range cost for lead free finish

•  Press fit suitable finish

•  Good solderability after multiple thermal excursions

•  Very sensitive to handling – gloves must be used

•  Tin whisker concerns

•  Aggressive to soldermask – soldermask dam shall be ≥ 5 mil

•  Baking prior to use can have a negative effect

•  Not recommended to use peelable masks

•  Should not plug holes on one side only

Immersion Ag – Immersion Silver
Typical thickness 0.12 – 0.40um. Shelf life: 6 months

•  Immersion finish = excellent flatness

•  Good for fine pitch / BGA / smaller components

•  Mid range cost for lead free finish

•  Can be reworked

•  Very sensitive to handling / tarnishing / cosmetic concerns – gloves must be used

•  Special packaging required – if packaged opened and not all boards used, it must be resealed quickly.

•  Short operating window between assembly stages

•  Not recommended to use peelable masks

•  Should not plug holes from one side only

•  Reduced supply chain options to support this finish

OSP (Organic Solderability Preservative)
Typical thickness 0.20-0.65μm. Shelf life: 6 months

•  Excellent flatness

•  Good for fine pitch / BGA / smaller components

•  Inexpensive / Low cost

•  Can be reworked

•  Clean, environmentally friendly process

•  Very sensitive to handling – gloves must be used and scratches avoided

•  Short operating window between assembly stages

•  Limited thermal cycles so not preferred for multiple soldering processes (>2/3)

•  Limited shelf life – not ideal for specific freight modes and long stock holding

•  Very difficult to inspect

•  Cleaning misprinted solderpaste can have a negative effect on the OSP coating

•  Baking prior to use can have a negative effect