1.0 What is immersion silver？
1.1 Immersion silver processThere is a process that meets that the RoHS standard, immersion silver, which is the common immersion PCB process. Immersion silver is an updated version of HASL and can be used in most applications as a substitute for immersion Gold rather than chemical Nickel (Au/Ni). The use of immersion silver has no effect on the assembly process of customers as its thickness is between 0.12 and 0.40μm.
- Lead free content
- Good surface flatness
- For small spacing components
- Can be modified repeatedly
- Excellent shelf life
- More harmful for people with sensitive skin - (Wear Gloves)
- The process contains carcinogens
- Tin is prone to corrosion during assembly
- Short operation window between assembly stages
- Thickness is not easy to measure
- Easily damaged devices
2.0 What is immersion Gold？
There are two methods with immersion Gold, Electroless Nickel Immersion Gold (ENIG) and Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG).
2.1 Electroless Nickel Immersion Gold (ENIG)
ENIG has two-layer metal coating, a layer is 2-8μin metal in Au, and another layer is 120-240μin metal in Ni. Nickel is a barrier to copper and is the surface to which the assembly is welded. During storage process, Gold protects Nickel and satisfies the low contact resistance need with thin Gold. Nowadays, ENIG is the most widely used finished product method in the PCB industry.
- Good surface flatness
- Lead free content
- Apply to Plated Through Holes
- Excellent shelf life
-Expensive
-Cannot be modified
-Black Pad / Black Nickel
-ET Damage
-RF Loss
-Complex process
2.2 Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG)
This surface treatment is often referred to as Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG). It consists of electroless Nickel plating with a thin layer of impregnated Gold. In ENEPIG, Gold is produced by displacement over a layer of Nickel. This process continues until the resulting layer of Gold covers the Nickel. This is a reason why the Gold is also thinner. The Gold layer protects Nickel from Oxidation. The general thickness range of ENEPIG is 0.05-0 23μm (2 - 9μin) Gold and 2.5-5.0 m (100-200 μin) chemical Nickel.
- Multi-cycle assembly
- Excellent surface flatness
- Lead free content
- Nickel layer (Strong protection & High weldability)
- Excellent shelf life
- Low contact resistance
- High signal strength
- Strong antioxidant capacity
- the price of your
- Not easy to modify
-Complex process
- Partial location processing is limited
3.0 What's the difference between immersion Gold and immersion silver？
ENEPIG is mainly used for PCB boards with connection function requirements and long storage life. Gold is uniform in thickness, flatness, good in contact, wettability, and good electrical performance. ENEPIG can be long-term storage (usually 1 year). Its biggest disadvantage is that it cannot be repeatedly modified, and the production requirements are relatively high.4.0 Conclusion
According to the advantages and disadvantages of these methods, it seen that there are some differences between these methods. Generally, ENEPIG really have more advantages than immersion silver and ENIG. However, ENEPIG's process requirements are relatively strict. So ENEPIG is the best choice in the case of meeting production needs and sufficient funds.