Advantages & Disadvantages of Surface Treatment

1. Nickel Gold (ENIG)

Characteristics :

· 3-6µ of nickel is placed on copper, followed by 0.05-0.1µ of gold.

· A good knowledge of the chemical process used to prevent oxidation of nickel.

Advantages/ Disadvantages:

· Good solderability.

· Very good flatness.

· Common finishing.

· Multiple brazing possible.

· Long lifespan.

· The nickel layer is not always compatible with uses high frequency.

· Too much oxidation of the nickel can lead to problems of soldering.

· High cost due to the use of gold.

2. Nickel - Gold Palladium (ENEPIG)

Characteristics :

· The method is identical to the ENIG plus depositing a layer of palladium from nickel and gold.

· This function is to prevent oxidation of nickel.

Advantages/ Disadvantages:

· Good solderability.

· Very good flatness.

· Multiple brazing possible.

· Long lifespan.

· More expensive than ENIG.

· Given its dissemination within 5 days is required.

3. HASL (Hot Air Solder Levelling)

Characteristics :

· After a first immersion, the carte is submerged in a tin-lead bath of 250 °C (482 °F). Just after immersion, hot air knife leveling the alloy surface.

Advantages/ Disadvantages:

· Good solderability.

· Cheap finishing.

· Long storage possible.

· SMD (surface-mounted device), fine cutting-point.

· Flatness (not recommended for small paths).

· Fierce temperature.

· Frail copper.

4. HASL Lead Free

Characteristics :

· The method is close to HAL, but the allay used is SN100C with a melting point of 270°C ( 518 °F).

Advantages/ Disadvantages:

· Identical to HAL. Low priced alternative to chemical finishing.

· Better planeity than SnPbHASL (BGA picth 0,8mm compatibility)

5. Immersion Tin

Characteristics :

· 1 to 1.2 µ of tin is selectively placed on a copper surface.

· An inter-metallic Copper-Tin is created after aging.

This inter metallic is not compatible with the solderability.

Advantages/ Disadvantages:

· Good solderability.

· Very good flatness.

· Compatible with Press-fit.

· Quick ageing.

· Incompatible with products needing a polymerisation process

· All welding has to be done at once.

· Use of a dangerous substance (Thiourea).