The Importance of PCB Surface Finishes for High-Performance Applications

A PCB surface finish is important for a printed circuit board since it protects the copper from oxidizing itself – an important factor in high-level application performance. A surface finish is important to ensure that firm and good connection established between the Soft Gold PCB and the electronic component. A surface finish is mainly used in two ways, it must offer a solderable surface with which to solder enough components to the PCB and secondly it has to guard any exposed copper from getting oxidized.

Making the right selection of the final type of finish is equally important as choosing the right material for your bare board. It is very important to choose the right surface finish depending on the application.

As customers continue to request a thinner substrate, higher density, faster speeds and lighter weight applications the solder finish will become the deciding factor.

• Electroless Nickel Immersion Gold (more commonly known as ENIG)
• These include Electrolytic Nickel/Gold – Ni/Au (Hard/Soft Gold).
• Immersion Silver
• White Tin or Immersion Tin
• OSP (Organic Solderability Preservatives)

Because of the application demands for higher performance of the electronics applications, there has also been the development of the surface finishes. As Soft Gold PCB manufacturing topographical designs are getting more compacted the HASL finish is gradually being phased out to gold plated covering like ENIG, ENEPIG and soft and hard gold. What makes the gold-based surface finishes good is their offer of many features and benefits when they are used in applications.

Why Is It Used?

Immersion Tin has been mostly applied as a replacement to lead surface finishing process. It is also used for the very flat and smooth dimension for it to suit fine geometries and fine pitch surface mount components.

Immersion tin is also sustainable; this is because after the tin has been dipped in immersion tin before soldering, it is only required to be soldered once, unlike when soldering solder float which requires being soldered severally. Some of the components that may be hard to procure are used in other finishes for instance the ENIG or HASL. Further, it is effective in application that requires lesser water and chemicals than traditional systems.

It is also easier to re-work.

As with all other surface finishes we have discussed here, there are a number of advantages and disadvantage of each one.

Advantages:

• Immersion Tin Finish has great flatting possibility (appropriate for SMT), good for F/P/BGA/S components.
• Immersion Tin is moderate in cost for lead free finish
• Press fit suitable finish
• Demonstrated to maintain satisfactory levels of solderability after several cycles of thermal stress.
• Applicable all the areas of organization especially for the Horizontal production line.
• Perfect for fine geometry organization and assembly, no lead.