Introduction for PCB common surface treatment

I.LF HASL - Lead free of Hot Air Solder Level

Common thickness 1-40UM

Advantage for the HASL LF Surface finishing

1. Very good for soldering

2. Cost effective

3. Long valid period

4. Long history with mature technology,Common surface treatment way.

5. Multiple thermal deviation

Disadvantage for the HASL LF Surface finish

1. The tolerance for the thickness of the pads / the tolerance for the profile size is lower than SNPB

2. Manufacturing temperature is high,260-270℃

3. Not suitable for SMD/BGA with the pin spacing less than 20mil

4. Solder bridge would happen for Micro spacing

5. Not suitable for HDI product.

Ⅱ.ENIG-Immersion gold

Common thickness is 3-6UM (Nickel) + 0.05-0.125UM(Gold)

Advantage for the ENIG Surface finishing

1. Excellent flatness

2. Suitable for Micro spacing/BGA/small components

3. Long history,Mature technology

4. Long storage life

5. Wires bond available

Disadvantage for the ENIG Surface finishing

1.Price higher

2.It may caused BGA pads become black

3.It’s erosion to the layer of soldermask - especially for the large resistance welding bridge.

4.Shouldn’t plug the vias by single side.

Ⅲ.Immersion Tin

Common thickness is 0.12-0.40UM

Advantage for the Immersion Tin

1.Excellent flatness

2.Suitable for Micro spacing/BGA/small components

3.Medium price range

4.Good solderability after multiple thermal deviations

Disadvantage for the Immersion Tin

1.Have to wear glove when production,A high demand is required during production procedure.

2.Tin whisker problem

3.It’s erosion to the layer of soldermask-resistance welding bridge should larger than 5mil.

4.To bake before use the boards may cause quality problem

5.The Peelable glue is not suggested

6.Shouldn’t plug the vias by single side.

Ⅳ.Immersion Silver

Common thickness is 0.12-0.40UM

 
Advantage for Immersion Silver

1.Excellent flatness

2.Suitable for Micro spacing/BGA/small components

3.Medium price range

4.Re-work available

5.Long storage period under a good package situation.

Disadvantage for Immersion Silver

1. A high demand is required for Silver color / PCB Profile ect,Glove is necessary for worker.

2. Special package is required

3. Short valid period for assembly manufacturing

4. The Peelable glue is not suggested

5.Shouldn’t plug the vias by single side.

V.OSP-Organic Solderability Preservative

Common thickness is larger than 1.0UM

Advantage for OSP surface treatment

1. Excellent flatness

2.Suitable for Micro spacing/BGA/small components

3.Cheap / Cost effective

4.Re-work available

5.Clean and environmental protection

Disadvantage for OSP surface treatment

1. A high demand is required when production,The Worker to Wear glove is necessary to avoid scratch

2. Short valid period for assembly manufacturing

3. Limited thermal cycling,It’s not preferred for multiple welding processes(>2/3)

4. Limited storage period - Not suitable for long shipping model or long storage.

5. It is difficult to test

6. The OSP coating probably adversely affected when cleaning misprinted solder paste

7. To bake the boards before assembly may cause adverse effect.


Click here:Most common used PCB surface finishing comparison
Click here:Introduction for Surface finish choices
Click here:Tips for PCB Storage with different surface finishing
Click here:PCB Final surface finish comparison

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