Introduction to some of the PCB surface treatment technology-Shenzhen Vip Circuit Co.，Ltd
PCB surface treatment technology refers to the PCB components and electrical connection point to form a layer with the matrix of the mechanical, physical or chemical properties on the surface. The aim is to ensure the good solderability or electrical performance of PCB. As the copper in the air tend to exist in the form of oxides, seriously affect the PCB solderability and electrical properties, therefore, the surface treatment of PCB is necessary.
The current common surface treatment methods are the following:
1, Hot Air Leveling(Lead-free)---HASL(Lead-free)
A process of coating molten tin lead solder on the PCB surface and leveling (blowing) with a heated compressed air to form a coating that is resistant to copper oxidation and provides good solderability. During the hot air, solder and copper form copper/tin metal compounds at the junction, and the thickness is about 1 to 2mil;
2, Organic Solderability Preservatives---OSP
OSP,it can also be called Preflux.It is grow a layer of organic film in a chemical way on a clean bare copper surface.This layer of film with anti-oxidation, heat shock, moisture resistance, to protect the copper surface is no longer continue to rust (oxidation or curing, etc.) in the normal environment,At the same time, it must be quickly removed by soldering flux in the subsequent welding high temperature so that can be helpful for the soldering.
3, Immersion Gold---ENIG
A nickel gold alloy with good electrical properties is coated on the copper surface, which can protect PCB surface for a long time. Unlike OSP just as a rust barrier, Immersion gold can be in the PCB long-term use of the process has a practical role and to achieve good electrical performance. Besides, its stability is very good,but the price is expensive than OSP and LF-HASL / HASL.
4 ,Immersion Silver---Immersion Ag
The process is relatively simple, fast, exposed to hot, wet and polluted environment, still can provide good electrical properties and maintain good solderability, but the silver will lose luster. Because there is no nickel below the silver layer, so the silver does not have all the good physical strength of immersion gold ;
5, Plating Nickel Gold / Electroplating Nickel Gold
Firstly plating a layer of nickel and then plating a layer of gold on the PCB surface, nickel is mainly to prevent the spread between gold and copper. There are two types of electroplating nickel/gold: plating soft gold (soft gold, gold surface does not look bright) and hard gold plating (surface smooth hard, wear, containing cobalt and other elements, the surface looks more bright). Soft gold is mainly used for chip packaging to wire bonding, hard gold is mainly used in non-welded electrical interconnection (such as gold finger).
6, PCB mixed surface treatment technology
Choose two or more surface treatment methods for surface treatment, common forms are: Immersion Gold + HASL(Lead-free), Electroplating nickel gold + Immersion Gold, Electroplating nickel gold + HASL(Lead-free), ENIG + OSP and so on.
RoHS is a mandatory standard developed by the EU legislation, its full name is Restriction of Hazardous Substances. The standard was officially implemented on July 1, 2006, mainly used to regulate the electrical and electronic products, materials and process standards, making it more conducive to human health and environmental protection. The aim of this standard is to eliminate the total amount of lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls and polybrominated diphenyl ethers in electrical and electronic products, and to impose a lead content of not more than 0.1%.
Article from Shenzhen Vip Circuit Co.，Ltd