Printed Circuit Board Finishes

6 Major Types of Printed Circuit Board Finishes

Anyone dealing with Printed Circuit Boards must be aware that PCB’s need some finishing on their surfaces before concluding that the end product is achieved. This is because if PCBs are left unprotected; without copper finishes, copper oxidizes and deteriorates thus the final circuit board thus the service life of the whole board is shortened significantly. It is critical to recall that PCBs are designed for various applications, pressures, temperatures and other work environment parameters. However, we at RushPCB (https://www.rushpcb.co.uk/ ) ensure that all the Printed Circuit Boards we design can fit in different environments like harsh solvents or chemicals, dust and elevated temperatures. It is because of our uniqueness and quality of the products that we offer to all our clients across the globe that we came up with this article to educate you on the most common types of PCB finishes and help you identify the best.

Using leaded solder

this is the most common type of PCB finishing. It is produced by mixing lead and tin such that the solder is easily applicable and provides a comprehensive coating which lasts for many years. This method of PCB finishing is applied by the immersion of the board into the mixture of molten tin and lead. Sequentially, an air knife is used to purposively blow off the excess mixture from the surface of the Printed Circuit Board. Different from that, this technique is one of the oldest techniques of PCB finishing but it’s still widely used due to its availability and low cost. However, it can be very harmful to the environment since high levels of lead may result to lead-poisoning in the air and consequently water sources when it rains. The end result of this effect is increased cases of blood cancer (leukemia) and infertility in human.

Using lead-free solder

this method eliminates harmful lead elements from the environment thus it is the more preferred compared to the leaded solder type. In this type of PCB finishing, the PCB is dipped in a molten mixture of copper and tin. Sequentially, an air knife is used to remove the excess solder from the PCB’s surface. This method leads to shiny silver colored PCB that can last for several years. Comparatively, the method is widely available and easy to apply in many PCB designs. Significantly, this method does not use lead thus it is environmentally friendly.

Using Electroless Nickel Immersion Gold (ENIG)

As of today, the electroless Nickel Immersion Gold is the best and the recommendable type of finish used in the manufacturing of Printed Circuit Boards. In the initial stages of the finishing, nickel of about 150 to 200 micro-inches is coated onto copper’s surface.  Nickel is used as a barrier to copper and it’s the surface where the components are soldered to. Sequentially, a thin layer of gold which is approximately 3 to about 10 micro-inches is applied over nickel’s coating. The gold provides protection to nickel during storage and provides an interface of low contact resistance which is requires for thin gold deposits. This coating uniquely provides a comprehensive protection to the Printed Circuit Boards from any hostile environmental conditions, is of flat surface, has no lead, is good for Plated Through Holes (PTH) and has a long life. Unfortunately, the coating is expensive, damaged by ET, has some properties of radio-frequency signal loss and islaborious to apply. Luckily, we at RushPCB have ENIG finished PCBs and we can fabricate any board depending on your specifications. Please pay us a visit today at https://www.rushpcb.co.uk

Using Immersion Silver method

in this technique of Printed Circuit Board finishing, a micron thick layer of silver element is comprehensively coated over copper’s surface though the application of the process of electroless plating.  Silver is used since it is has a high electrical conductivity thus it form excellent interconnect surface.  This technique leads to the creation of a flat surface that has outstanding solderability and is environmentally friendly since it does not use lead coating. Equally important, the PCBs finished using this technique can be used for high speed signals. However, when exposed to high humidity, temperature or mishandled, the coating becomes susceptible.

Immersion Tin

this method is also lead-free and it uses SMT assembly for PCB finishing. In this type of PCB finishing, a thin layer of tin is applied over copper layers thus leading to a whitish finish. Tin and copper have a strong affinity for each other and the diffusion of one metal into the other metal’s surface occurs inevitably. On the other hand, this method is cost-effective compared to gold and silver immersion techniques. Moreover, it is free of lead-deposits, its re-workable and the best choice for Press Fit Pin Insertion. Unfortunately, it has a very short (limited) shelf life and it has higher chances of being damaged when compared to silver and gold finished PCBs. Consequently, Printed Circuit Boards coated with tin are used for a short period of time; usually 6 to 12 months. As if that is not enough, the thickness of such boards cannot be measured easily and the technique uses Thiourea which is a Carcinogen. Do you want to know more of Tin Immersion finished PCBs? Please visit us at: https://www.rushpcb.co.uk/and feel free to ask us any question or place an order. Customer satisfaction is our pride.

Using Organic Surface Protectant (OSP/Entek)

this method leads to a green finish unlike the other methods of PCB finishing. In this method of PCB finishing, a water based organic compound is carefully applied over copper by making use of a conveyorized process. The compound not only bonds tocopper but also protects copper during the soldering process. Sequentially, in industrial environments which are aggressive; the coating protects the copper from oxidation. Additionally, the method is cost-effective and is simple to apply unlike other methods like ENIG. Are you in need of such a board? Kindly visit us at https://www.rushpcb.co.uk/

With the discussion above, you must have some questions about the best type of Printed Circuit Board finish to use. We at RushPCB have the answers to all your questions and we are ready to provide any type of finishing for you at a cheap price. Please note that the quality of the final board and consequently the product depends on the efficiency with which PCB finishing is done. This is why we recommend you to the experts; https://www.rushpcb.co.uk/contact/.