PCB Surface Finish Types

The surface of printed circuit boards (PCB) is made of copper to ensure electric currents flow efficiently. These metals require appropriate protection to avoid oxidation or other corrosion. A range of PCB surface finish types provide different levels of protection against deterioration. PCB surface finishes also aid in certain processes such as soldering.

Typically, the main factors to consider when selecting the most suitable finish are:

  • End application
  • The assembly process
  • The design of the PCB

 

We have compiled the table below as a guideline for standard PCB finishes. This table will give you a brief understanding about different surface finishes that enhance performance of your PCB. The shelf life is absolutely a critical element you need to consider when planning your purchasing schedules. Make sure all the PCBs you purchased are assembled within the shelf life, and please pay attention to time schedule between when the PCBs are taken out from the vacuum package and your wave soldering time.

 

Property/RequirementImmersion Gold (ENIG)Immersion Silver (I Ag)Immersion Tin (I Sn)OSPLF-HASLHASL (Tin Lead)
CostHighMediumMediumLowestLowLow
Estimated Shelf Life (15-28°c)12 months6 months6 months6 months12 months12 months
Thermal Shock (PCB MFG)LowVery LowVery LowVery LowHighHigh
Wetting PerformanceVery GoodGoodGoodLowBestBest
Solder Paste Printing (fine pitch)ExcellentExcellentExcellentExcellentGoodGood
Integrity/Reliability Of Solder JointBestGoodGoodGoodBestBest
Al. Wire Bonding (can be used with)YesYesNoNoNoNo
RoHS CompliantYesYesYesYesYesNo

 

Here is also a brief summary of the most common advantages and disadvantages of different PCB finishing procedures. However for further or more detailed information, please feel free to contact our sales team. We are hearer to answer all your questions.

 

HASL – Tin/Lead hot air solder level
HASL is an affordable finishing option that utilizes tin/lead to creating a thin protective covering on a PCB. Hot air bursts are used to clear excess lead or tin from the board’s surface.
Typical thickness 1 – 40um. Shelf life:12 months
 
1. Excellent solderability
2.  Low cost
3. Allows large processing window
4. Long industry experience / well known finish
5. Multiple thermal excursions
 
1. Difference in thickness / uneven surface for soldering
2. Not suited for < 20mil pitch SMD & BGA
3. Contains Lead (Not RoHS Compliant)
4. Not ideal for HDI products
5. Cannot hold tight tolerances on plated holes
LF HASL – Lead Free hot air solder level ( Pb-Free HASL)
 LF HASL finishes use tin or copper paired with nickel to create a protective coating.
Typical thickness 1 – 40um. Shelf life: 12 months
 
1. Excellent solderability
2.  Low cost
3. Lead free and RoHS Compliant
4. Allows large processing window
5. Multiple thermal excursions
 
1. Difference in thickness / uneven surface for soldering
2. High processing temperature – 260-270 degrees C
3. Not suited for < 20mil pitch SMD & BGA
4. Bridging on fine pitch
5. Not ideal for HDI products
Immersion gold (ENIG) / Electroless Nickel Immersion Gold
Immersion Gold is one of the most popular widely-used circuit board finishes available today.  The gold protects the nickel from corrosion and the nickel protects the base metal board and allows for circuits to be securely soldered to its surface.
Typical thickness 3 – 6um Nickel / 0.05 – 0.125um Gold. Shelf life: 12 months
 
1. Immersion finish = flat surface to solder to
2. Lead free and RoHS Compliant
3. Good for fine pitch / BGA / smaller components
4. Longer Shelf Life, Tighter tolerances can be held for plated holes.
 
1. Expensive
2. Black pad concerns on BGA
3. Can be aggressive to soldermask – larger soldermask dam preferred
4. Signal loss for signal integrity applications
Immersion Silver -Immersion Ag ( I Ag)
Immersion Tin (IAg) is applied directly to the base metal of a PCB via chemical displacement. Due to the way copper and silver interact, they eventually diffuse into one another.
Typical thickness 0.12 – 0.40um (4-12u”). Shelf life: 6 months
 
1. Immersion finish = flat surface to solder to
2. Lead free and RoHS Compliant
3. Good for fine pitch / BGA / smaller components
4. Low loss for Signal Integrity Applications.
5. Tighter tolerances can be held for plated holes,
6. Mid range cost for lead free finish,  cost  between ENIG and Immersion Sn ( I Sn)
 
1. Very sensitive to handling / tarnishing / cosmetic concerns – gloves must be used
2. Special packaging required –When the package is opened and all boards are not used, then it must be resealed quickly.
3. Finish can tarnish and oxidize, short operating window between assembly stages
4. Not recommended to use peelable masks
5. Shorter Shelf Life than ENIG
Immersion Tin-Immersion Sn ( I Sn)
Immersion Tin (ISn) is applied directly to the base metal of a PCB via chemical displacement. It’s a more affordable option than ENIG and Immersion Silver. Due to the way tin and copper interact, they eventually diffuse into one another.
Typical thickness ≥ 1.0µm. Shelf life: 6 months
 
1. Immersion finish = flat surface to solder to
2. Lead free and RoHS Compliant
3. Good for fine pitch / BGA / smaller components
4. Press fit suitable finish, it’s a more affordable option than ENIG and Immersion Silver,
5. Good solderability
6. Mid range cost for lead free finish, cost less than I Ag and ENIG
 
1. Very sensitive to handling – gloves must be used
2. Tin whisker concerns
3. Aggressive to soldermask – soldermask dam shall be ≥ 5 mil
4. Baking prior to use can have a negative effect
5. Not recommended to use peelable masks
6. Shorter Shelf Life than ENIG
OSP (Organic Solderability Preservative)
The Organic Solderability Preservative (OSP) doesn’t introduce any toxins into the process. Instead, an organic compound is used that bonds naturally with copper, creating an organometallic layer that protects against corrosion.
Typical thickness 0.20-0.65µm. Shelf life: 6 months
 
1. Excellent flatness
2. Good for fine pitch / BGA / smaller components
3. Inexpensive / Low cost
4. Can be reworked
5. Clean, environmentally friendly process
 
1. Very sensitive to handling – gloves must be used and scratches avoided
2. Short operating window between assembly stages
3. Limited thermal cycles, thus not preferred for multiple soldering processes (>2/3)
4. Limited shelf life – not ideal for specific freight modes and long stock holding
5. Very difficult to inspect
6. Cleaning misprinted solder paste can have a negative effect on the OSP coating
7. Baking prior to use can have a negative effect
Hard Gold
Among the most expensive PCB surface finish types, hard gold applications are extremely durable and enjoy a long shelf life. They’re commonly reserved for components that get a substantial amount of use, with normal thickness rates ranging from 30 μin gold over 100 μin nickel to 50 μin gold over 100 μin nickel.
 
1.Durable surface
2. Lead-Free and RoHS Complaint,
3. Long shelf life.
 
1. Extremely expensive compared to other finishes
2. Bus plating can be required, and additional labor required.
3. Additional labor required.

 

Venture PCB Surface Finishes Options

*  Immersion Gold (ENIG) & ENEPIG*  Immersion Silver(I Ag) & Immersion Sn (I Sn)
* HASL (lead)*  HASL( lead free)
* OSP*  Soft Gold & Hard Gold
* Gold Fingers ( GF)*  Immersion Sn +Gold Fingers
*  Plating Au*  Ni
*  Gold Fingers + OSP*  Gold Fingers + HASL
*  OSP+ENIG*  Immersion Silver + Gold Fingers

 

Alternative surface finishes process are available through our network of fully approved sub-contractors. For further or more detailed information, please feel free to contact our sales. We are here to answer any of your questions.