The surface coating process is one of the most important and final stages in PCB (Printed Circuit Boards) production. Solderable surfaces are formed on the PCB after the surface coating process. PCB surface coating and board placing are a whole. The smoother and higher quality the soldering surface in the placing process is, the more successful the result would be.
We can list some of the surface coating types as follows:
-HASL-LEADFREE; Hot Air Solder Leveling Lead FREE
-HASL-LEADED; Hot Air Solder Leveling Leaded
-OSP; Organic Solderability Preservatives
-ENIG; Electroless Nickel Immersion Gold
-ENEG; Electroless Nickel Electroless Gold
-ENEPIG; Electroless Nickel Electroless Palladium Immersion Gold
- Immersion Silver
- Immersion Tin
These types of coatings are usually applied alone, but there are also cases where they are applied in combination. For example, OSP and ENIG can be applied as ENIG Plus OSP.
PCB design accuracy, placing criteria, place of use, structural properties of the material, costs and similar criteria help the designer to choose the most suitable surface coating. There are advantages and disadvantages of all coating types. To briefly explain;
HASL-LEADFREE (Lead-Free Coating);
The degree of soldering is high in this type of coating. It has RoHS certificate. The surface smoothness is moderate both in coating with and without lead. Both coating types are the most widely preferred types in the industrial field. One of the disadvantages is that it is difficult to apply laminates below 0.6 mm due to the process temperature. The shelf life is 12 months.
HASL-LEADED (Leaded Coating);
It offers the advantage of being easily soldered at lower temperatures than lead-free coating. On the other hand, the leaded surface causes limitations since it cannot obtain ROHS certificate. The surface smoothness is moderate. The shelf life is averagely 12 months.
“Ozdisan PCB technical support unit helps the customers to make the correct choice
by meeting customer demands in surface coating selection.”
GOLD PLATED;
If the PCB design is complex, OSP or GOLD plating is usually preferred. The surface smoothness of both coatings is ideal. It provides convenience especially in the placement of boards with BGA processor. It is the most widely used ENIG coating type among gold plating variants. It has a price advantage over other gold-plated variants. HARD GOLD, on the other hand, has an increased gold surface thickness compared to that of ENIG, and is preferred in joints that require a hard surface. Gold-plated types do not contain lead. It is fully RoHS compliant. Corrosion resistance is ensured by treatment with nickel material. The shelf life is averagely 12 months. ENEPIG, one of the gold-plated variants, is preferred in high-tech and military cards.
OSP;
It is known as organic coating. It is also called “ENTEK”. This type of coating is an organic chemical protective coating applied on the copper. Its advantage is that the surface smoothness is good, like gold plating, and it is more economical. It provides convenience in the placement of boards with BGA processor. Its disadvantage is that its shelf life is short. The average shelf life is 6 months.
IMMERSION SILVER (SILVER PLATED);
Similarly, the surface smoothness is very good in silver plating. The electrical conductivity is high. It is preferred in high frequency designs.
IMMERSION TIN (TIN PLATED);
It is an economical and easy-to-apply coating type. Provides ease of soldering. It offers a flat and smooth surface. The negative side is that it can be easily oxidized. The shelf life is quite short. The average shelf life is limited to 3-6 months. At Ozdisan PCB unit, we meet customer demands in surface coating selection and help them to make the correct choice.
