Abstract

Electronics tend to be thin in thickness, small in size and light in weight, with more functionality and speed. Therefore, the electronic industry has developed diversified and advanced technologies and methods to enable it to increase the density, quantity and variety of integrated circuits (IC) on the same circuit board.

The way to increase the density of packages and connections is from the evolution of through-hole technology(PTH) towards the surface assembly technology(SMT), which leads to the further application of Wire bonding. The reduced connection line spacing and application of chip size packaging technology (CPS) increase the density of the device. thus derived a new surface treatment process, ENEPIG. The ENEPIG’s process and advantages will be described below.

Key words

Ni/Pd/Au、ENEPIG、Wire bonding、Black PAD

Introduction of ENEPIG Process

Chemical nickel palladium gold is a layer of palladium between nickel and gold, which can prevent the corrosion caused by the displacement reaction and prepare for the sinking gold. Gold is tightly covered in palladium, providing a good contact surface.

Process:

Chemical reaction mechanism

Picture from network

The characteristic chemical Pd(No electrolytic palladium)

1. Coated on top of the nickel layer.
2. Prevent the oxidation of the nickel layer and improve the wiring and welding capacity.
3. The gold thread can be fixed.
4. Prevent the black pad from happening.

Performance comparison of different surface treatments

★The more stars the better

The image of palladium layer layer

The Advantages of ENEPIG

1. Gold coating is very thin can be gold wire, or aluminum wire.
2. The palladium layer can separate the nickel layer from the gold layer, prevent the transfer of gold and nickel to each other, and prevent the occurrence of black circles
3. Improved weldability after high temperature aging and high humidity, excellent wire bonding.
4. Low cost, gold thickness 0.03-0.04um, average palladium thickness 0.025-0.03um .
5. The palladium layer is thin and uniform.
6. The nickel layer is lead free
7. Good compatibility of coating with solder paste