Printed circuit board surface finish

The circuit board surface is responsible for raising the wetting ability of the contact areas for soldering; non-chemical surfaces serve simultaneously as protection against oxidation of the covered copper and improve shelf life characteristics. 

The circuit board surfaces vary in shelf life, typical application field and price, but are normally specified by the process, product or desired location for the application.

Available surfaces

SurfacePCB RoHS-compliantRoHS-compliantPCB solderingSolderingPCB Bonding aluminium wireBonding aluminium wirePCB Bonding gold wireBonding gold wirePCB BGABGAPCB Flex-/Rigid-FlexFlex-/Rigid-FlexPCB PressfitPressfitPCB PCI contactsPCI contactsPCB sliding contactSliding contactPCB surface thicknessThicknessPCB shelf lifeShelf lifePCB Reflow CyclesReflow Cycles
SurfaceHal SnPbPCB RoHS-compliantRoHS-compliant PCB solderingSolderingcheckPCB Bonding aluminium wireBonding aluminium wire PCB Bonding gold wireBonding gold wire PCB BGABGA PCB Flex-/Rigid-FlexFlex-/Rigid-Flex PCB PressfitPressfitcheckPCB PCI contactsPCI contacts PCB sliding contactSliding contact PCB surface thicknessThickness>5µmPCB shelf lifeShelf lifeca.12 monthsPCB Reflow CyclesReflow Cycles5**
SurfaceHAL lead-freePCB RoHS-compliantRoHS-compliantcheckPCB solderingSolderingcheckPCB Bonding aluminium wireBonding aluminium wire PCB Bonding gold wireBonding gold wire PCB BGABGA PCB Flex-/Rigid-FlexFlex-/Rigid-Flex PCB PressfitPressfitcheckPCB PCI contactsPCI contacts PCB sliding contactSliding contact PCB surface thicknessThicknessacc. to IPC-6012*PCB shelf lifeShelf lifeca. 12 monthsPCB Reflow CyclesReflow Cycles5**
SurfaceChemical tinPCB RoHS-compliantRoHS-compliantcheckPCB solderingSolderingcheckPCB Bonding aluminium wireBonding aluminium wire PCB Bonding gold wireBonding gold wire PCB BGABGA PCB Flex-/Rigid-FlexFlex-/Rigid-Flex PCB PressfitPressfitcheckPCB PCI contactsPCI contacts PCB sliding contactSliding contact PCB surface thicknessThickness>1µmPCB shelf lifeShelf lifeca. 6 monthsPCB Reflow CyclesReflow Cycles5**
SurfaceChemical silverPCB RoHS-compliantRoHS-compliantcheckPCB solderingSolderingcheckPCB Bonding aluminium wireBonding aluminium wirecheckPCB Bonding gold wireBonding gold wire PCB BGABGA PCB Flex-/Rigid-FlexFlex-/Rigid-Flex PCB PressfitPressfitcheckPCB PCI contactsPCI contacts PCB sliding contactSliding contact PCB surface thicknessThickness0.2 - 0.3µmPCB shelf lifeShelf lifeca. 12 MonatePCB Reflow CyclesReflow Cycles5**
SurfaceChemical gold
ENIG		PCB RoHS-compliantRoHS-compliantcheckPCB solderingSolderingcheckPCB Bonding aluminium wireBonding aluminium wirecheckPCB Bonding gold wireBonding gold wire PCB BGABGAcheckPCB Flex-/Rigid-FlexFlex-/Rigid-FlexcheckPCB PressfitPressfitcheckPCB PCI contactsPCI contacts PCB sliding contactSliding contact PCB surface thicknessThickness3-6µm Ni
0.05-0.1µm Au		PCB shelf lifeShelf lifeca. 12 monthsPCB Reflow CyclesReflow Cycles5**
SurfaceENEPIGPCB RoHS-compliantRoHS-compliantcheckPCB solderingSolderingcheckPCB Bonding aluminium wireBonding aluminium wirecheckPCB Bonding gold wireBonding gold wirecheckPCB BGABGAcheckPCB Flex-/Rigid-FlexFlex-/Rigid-Flex PCB PressfitPressfitcheckPCB PCI contactsPCI contacts PCB sliding contactSliding contact PCB surface thicknessThickness3-8µm Ni
0.05-0.15µm Pd
0.05-0.1µm Au		PCB shelf lifeShelf lifeca. 12 monthsPCB Reflow CyclesReflow Cycles-
SurfaceGalvanic softgoldPCB RoHS-compliantRoHS-compliantcheckPCB solderingSolderingcheckPCB Bonding aluminium wireBonding aluminium wire PCB Bonding gold wireBonding gold wirecheckPCB BGABGA PCB Flex-/Rigid-FlexFlex-/Rigid-Flex PCB PressfitPressfit PCB PCI contactsPCI contacts PCB sliding contactSliding contact PCB surface thicknessThickness4 - 6µm Ni
>1µm Au		PCB shelf lifeShelf lifeca. 12 monthsPCB Reflow CyclesReflow Cycles-
SurfaceGalvanic hardgoldPCB RoHS-compliantRoHS-compliantcheckPCB solderingSoldering PCB Bonding aluminium wireBonding aluminium wire PCB Bonding gold wireBonding gold wire PCB BGABGA PCB Flex-/Rigid-FlexFlex-/Rigid-Flex PCB PressfitPressfit PCB PCI contactsPCI contactscheckPCB sliding contactSliding contactcheckPCB surface thicknessThickness4 - 6µm Ni
0.8 - 2µm Au		PCB shelf lifeShelf lifeca. 12 months
on request		PCB Reflow CyclesReflow Cycles-

* IPC-6012: Fully covered and solderable | ** not reliable empirical values

PCB surface HAL SnPb

HAL SnPb

HAL SnPb (lead-tin) is nowadays allowed only in certain technology fields such as medicine and space travel. HAL is suitable for standard SMD, but shows weaknesses in fine pitch applications. A chemical surface is preferable for finepitch (see also HAL vs.  chemical gold).

Advantages:

  • Good solderability
  • Good reflow properties

Disadvantages:

PCB surface HAL leadfree

HAL lead-free

HAL (Hot Air Levelling) is a well-proven method to apply tin as circuit board surface. Every assembler should be able to process circuit boards with HAL surfaces without any problem. HAL is suitable for standard SMD, but exhibits some weaknesses for finepitch applications, for which a chemical surface should be preferred (see also HAL vs.  immersion gold).

Advantages:

  • Good solderability
  • Good reflow properties

Disadvantages:

  • Pads are non-planar
PCB surface chemical tin (immersion tin)

Chemical tin

The surface chemical tin is for manufacturing reasons rarely requested any more! Due to the rapid oxidation of the copper, the shelf life is highly dependent on temperature and packaging. Fingerprints on the surface should be avoided at all.

Advantages:

  • Absolutely flat
  • Good for fine pitch
  • Good for SMD
  • Good for press-fit

Disadvantages:

  • Extra charge
  • Critical manufacturing process
  • Faster oxidation, thus:
  • Limited storability
PCB surface chemical silver (immersion silver)

Chemical silver

This circuit board surface is very similar to chemical tin, with better properties for oxidation and contact applications. The surface is very flat and therefore suited very well for finepitch.

Advantages:

  • Absolutely flat
  • Good for fine pitch
  • Good for SMD
  • Good for press-fit
  • Better shelf life than chemical tin

Disadvantages:

PCB surface chemical gold (ENIG)

Chemical gold (ENIG)

Just as with chemical tin and chemical silver, chemical gold is an extremely flat circuit board surface, and has very good oxidation properties. It is perfectly suited for finepitch and bonding (aluminium wire) applications. Due to popular demand, Multi-CB can offer chemical gold in pooling service (cheaper price). Chemical gold is also called ENIG (Electroless Nickel Immersion Gold).

Advantages:

  • Absolutely flat
  • Very good for fine pitch
  • Very good for SMD
  • Very good wetting characteristics
  • Good for press-fit
  • Good storability
  • Available in Pool-Service

Disadvantages:

  • Possible extra charge
PCB surface ENEPIG

ENEPIG

ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold) is extremely planar and has very good oxidation properties. It is ideally suited for soldering applications and aluminum wire bonding / gold wire bonding.

Advantages:

  • Absolutely flat
  • Very good for alu-wire-bonding
  • Very good for gold-wire-bonding
  • Very good for fine pitch, SMD
  • Very good wetting characteristics
  • Good storability

Disadvantages:

  • Extra charge

Additional information