Choosing PCB Plating Solution

Printed circuit boards are also coated or plated for their protection, and often this is done with a surface finish of solder or some other material. Not only does this help to protect the exposed metal on the board from corrosion, but it helps with component soldering.

Different types of surface finishes can be used on a circuit board depending on what kind of protection the board needs:

 

ENIG (Electroless Nickel Immersion Gold):  after the solder mask

ENIG has become one of the most popular surface finishes currently being applied to circuit boards. It is composed of two layers of metal coatings, with the first being a layer of nickel that is chemically plated to the board. The nickel provides a barrier of protection for the copper and then, in turn, is protected from oxidation by a thin layer of gold.

Organic Solderability Preservative (OSP)

OSP is to chemically grow a layer of organic film on the clean bare copper surface. This layer of film has anti-oxidation, thermal shock resistance, and moisture resistance to protect the copper surface from rusting (oxidation or sulfidation, etc.) in a normal environment; but in the subsequent soldering high temperature, this protective film must be very easy to be quickly removed by the flux, so that the exposed clean copper surface can be immediately combined with the molten solder into a strong solder joint in a very short time. But it is not suitable for multiple reflow soldering.  

Immersion Silver

This finish is often used in high-speed circuit boards as the silver has low losses in high-frequency applications.

The process is relatively simple and fast; even if exposed to heat, humidity and pollution, silver can still maintain good solderability, but will lose its luster. Immersion silver does not have the good physical strength of electroless nickel/immersion gold because there is no nickel under the silver layer. As the immersion silver surface treatment with other unmatched good electrical properties, it can also be used in high-frequency signal board.

Our Silver-Plating offering: organic brightener system & electrolytic brightener[AB1] 

 

ENEPIG

Electroless nickel electroless palladium immersion gold):  after the solder mask. The chemical nickel palladium gold has an extra layer of palladium between nickel and gold. Palladium can prevent corrosion caused by substitution reaction and make full preparations for immersion gold. Gold is tightly covered on palladium, providing a good contact surface.

 

Hard Gold

Nickel and gold are electroplated on the same surface. It contains other metals so that to improve the wear resistance of the product. as well as increase the number of insertion and removal and electroplating of hard gold. The abrasion resistance of electric gold is relatively high. As the integration of IC becomes higher and higher, IC pins become denser. The vertical spray tin process is difficult to flatten the thin pads, which brings difficulty to the SMT placement; in addition, the shelf life of the spray tin plate is very short. The gold-plated [AB2] board just solves these problems, so the whole board gold plating is common in high-density and ultra-small surface mount processes.

 

Palladium

The physical properties of palladium combine to make it an ideal metal for the plating of printed circuits. Palladium is extensively used in plating of printed circuits, particularly for plug applications. Typically for printed circuit board applications palladium is plated on a nickel or copper base. The palladium is applied on the base followed by a soft gold over plate. Palladium has very good solder ability characteristics and is wire bondable so the final gold thickness can be reduced. Palladium has a Knoop hardness up to 400 so it is an excellent choice in electrical contact applications where contact wear is a concern.

P & S Chemitech offers Palladium Flash[AB3]  (to deposit bright white palladium flash deposit), Neutral Bath (to deposit bright white palladium deposit), mildly alkaline electrolyte (to deposit bright black palladium deposit), palladium nickel alloy with 20% Palladium, palladium nickel alloy with 80% Palladium

 [AB1]Link to Silver Plating Chemistry [Superb rite Silver EF, Silver plating PS11]

 [AB2]Link to Geeform 2024S

 [AB3]Link to Palladium Plating