Soderability

The ability of a surface, under a given set of conditions such as fluxing and temperature, to be wetted by liquid solder and thus to form a bond with another solid component.
It is NOT an intrinsic property, but is a FUNCTION OF THE OVERALL SYSTEM.

Soldering of ENP Films

ALL electroless nickel deposits can be readily soldered provided the soldering conditions are matched to the particular surface.

Advantages of Soldering to ENP Films

• Superior corrosion protection of the device
• Excellent thermal diffusion protection
• Uniformity of the coating allows successful mounting of flat pak devices

Why Use Solderable ENP?

• To provide a solderable finish over a nonsolderable base
• To use nickel as a barrier to inhibit leaching of the base material into the molten solder
• To provide a diffusion barrier to minimize the formation of undesirable intermetallics

• Phosphorus Content
• Bath Age
• Bath pH
• Bath Temperature
• Additives / Contaminants
• Age of Deposit
• Storage Conditions
• Return to Index

Additives / contaminants

• Cadmium, zinc, and sulfur are detrimental to the solderablity of electroless nickel coatings
  .

Which Electroless Nickel Coatings are Most Solderable

• Theoretically,low phos electroless nickel deposits are most easily solderable, immediately after deposition, than higher P ENP Films. 
• Practically, high phos electroless nickel coated components have the best results for solderable applications because of the uniformity of the oxide. This is important because most companies send out their plating, and do their soldering in house. The immediacy needed for successful soldering with a low phos deposit is not standard manufacturing process today, and the oxide produced is much less uniform and can form a tenacious barrier for soldering.

Storage Condition - Potential Problems

• SO2
• Cl2
• High Humidity
• High Temperatures
  

Additional Cautions

• Other problem areas for ENP plated components that will get soldered
• Human Handling - Oils
• Contamination from Handling Equipment - Conveyor greases
• Packaging Materials - Sizing agents can inhibit solderablity
  

• Increase flux dwell time ( 4.5 - 9 sec. )
• Increase flux temperature ( 70 - 120 degrees F. )
• Change to a more active flux
• Increase solder temperature
• Use higher tin content solder
• Increase solder dwell time ( 0.8 - 1.6 sec. )
  

Summary

• Use care to thoroughly rinse plating solutions
• Do not package parts if wet or hot
• Use proper packaging material
• Store parts in clean location - avoid industrial fumes and chemical vapors
• Avoid ENP which contain materials detrimental to wetting (Zn, S, Cd)
• Use a High Phosphorous electroless nickel chemistry
• Solder as soon as possible after plating
• Back fill packaging with nitrogen if prolonged storage or shipping is required.