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Microwave Tech
ENEPIG PCB surface treatment process
Microwave Tech
ENEPIG PCB surface treatment process

ENEPIG PCB surface treatment process

2021-12-27
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Author:pcb

Compared with other processes such as OSP and ENIG, ENEPIG PCB surface treatment process has the following advantages:

1. ENEPIG prevents the occurrence of "black nickel problem" - there is no replacement gold to attack the nickel surface, resulting in grain boundary corrosion.

2. Electroless palladium plating of ENEPIG will be used as a barrier layer, and there will be no problem of copper migration to gold layer, resulting in poor solderability.

3. The electroless palladium plating layer of ENEPIG will be completely dissolved in the solder, and there will be no high phosphorus layer on the alloy interface. At the same time, when the electroless palladium is dissolved, a new electroless nickel layer will be exposed to produce a good nickel tin alloy.

4. ENEPIG can withstand multiple lead-free reflow soldering cycles.

5. ENEPIG has excellent bonding of gold wire (bond).

6. ENEPIG is very suitable for SSOP, TSOP, QFP, TQFP, PBGA and other packaging components.


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Detailed explanation of ENEPIG PCB surface treatment process:

1. For ordinary ENIG nickel gold plates, the gold layer is required to be very thick, basically more than 0.3 microns. ENEPIG plates only need about 0.1 microns of palladium and 0.1 microns of gold (palladium is a precious metal much harder than gold. The reason for the palladium layer is that pure gold and nickel are seriously corroded and the welding reliability is poor. Palladium also plays a role in heat diffusion. On the whole, the reliability of ENEPIG is higher than that of ENIG).

2. The process of chemical nickel palladium metal has been proposed for several years, but now there are few PCB manufacturers producing energy, that is, only some large PCB manufacturers have mass production. The process is basically similar to the chemical gold precipitation process. A chemical palladium tank (reducing palladium) is added between chemical nickel and chemical gold. The ENEPIG process is: degreasing - micro etching - Pickling - prepreg - activated palladium - chemical nickel (reduction) - Chemical palladium (reduction) - chemical gold (replacement).

3. There are few PCB manufacturers that can really do a good job in the surface treatment process of ENEPIG PCB. The main control points are palladium tank and gold tank. Palladium is the active metal that can be used as catalyst. If it is not well controlled after adding reducing agent, it will react by itself (that is, turning the tank as the saying goes). Unstable deposition speed is also a problem. Many tanks are very fast, and the speed will slow down a lot in less than a few days. This is not something that ordinary companies can do well.

4. At present, there are many problems of black nickel in chemical gold precipitation and diffusion after heating. Adding a layer of dense palladium in the middle can effectively prevent the diffusion of black nickel and nickel.

5. The surface treatment was first proposed by Inter. Now it is used in many BGA carrier plates. One side of the carrier plate needs bonding wire and the other side needs soldering. The thickness requirements of these two surfaces are different. It is determined that the gold layer needs to be a little thicker, about more than 0.3 microns, while the solder only needs about 0.05 microns. When the gold layer is thick, the bonding strength is good, but there is a problem with the solder strength. When the gold layer is thin, the solder is OK, but it can't be hit. Therefore, the previous processes were covered with dry film and gold plating of different specifications twice. At present, the same thickness specifications on both sides of nickel palladium (ENEPIG) can meet the requirements of bonding and solder. At present, the thickness of palladium and gold film is about more than 0.08 microns, which can meet the requirements of bonding and solder welding.


At present, the companies that widely use this technology include Microsoft, apple, Intel, etc!

Unit conversion:

1um (micron) = 39.37uinch (micro inch)

1cm (CM) = 10mm (mm) 1mm = 1000um

1ft (feet) = 1000mil (mils) = 1000000uinch (micro inches)

1ft = 12inch 1inch = 25.4mm 1ft = 0.3048m

1mil=25.4um=1000uinch

As mentioned above, uinch reads Mai Some electroplating plants use U '' in the film thickness report