PCB Fabrication

How to judge the PCB surface process by color

by:A-TECH      2021-04-03
How to judge the PCB surface process by color 2020-06-29 15:55:00 In this technologically advanced information age, the circuit boards of mobile phones and computers generally contain gold and copper. Therefore, the recycling price of used circuit boards can reach more than 30 yuan per kilogram. It makes more money than selling waste paper, glass bottles, and scrap iron. From the appearance alone, the outer layer of the circuit board mainly has three colors: gold, silver, and light red. Gold is the most expensive, silver is the cheapest, and light red is the cheapest. Generally, it can be seen from the color whether the PCB manufacturers are cutting corners. In addition, the circuits inside the circuit board are mainly pure copper, which is easily oxidized if exposed to the air, and the outer layer must have the above-mentioned protective layer. Some people say that golden yellow is copper, which is wrong. So let's take a look at the difference between them. 1. Gold The most expensive gold is real gold. Although there is only a thin layer, it also accounts for nearly 10% of the cost of the circuit board. Some places along the coast of Guangdong and Fujian specialize in purchasing waste circuit boards and peeling off the gold. The profits are considerable. There are two reasons why gold is used, one is to facilitate welding, and the other is to prevent corrosion. Gold fingers that have been stored for a long time can still be shiny. If they are replaced with copper, aluminum, or iron, they will be rusty and useless. The gold-plated layer is widely used in the component pads, gold fingers, and connector shrapnel of the circuit board. If you find that some circuit boards are all silver, you must be cutting corners. The industry term is called 'costdown'. This kind of gold is very common in life. For example, mobile phone motherboards are mostly gold-plated boards, while computer motherboards, audio and small digital circuit boards are generally not gold-plated boards. Gold-plated circuit boards can generally be stored for a long time. 2. Silver Some people want to ask, gold is gold, is silver silver? The editor tells you that of course not, the silver one is tin. The silver board is called the spray tin board. Spraying a layer of tin on the outer layer of the copper circuit can also help soldering. But it cannot provide long-term contact reliability like gold. The tin-spraying board has no effect on the components that have been soldered, but the reliability of the pads that have been exposed to the air for a long time, such as grounding pads, spring pin sockets, etc. Long-term use is prone to oxidation and corrosion, resulting in poor contact. The circuit boards of small digital products, without exception, are spray tin boards. There is only one reason: cheap. In daily life, small and medium digital products are widely used in the production of electrical components with spray tin plates. 3. Light red OSP, organic soldering film. Because it is organic, not metal, it is cheaper than tin spraying. The only function of this organic film is to ensure that the inner copper foil will not be oxidized before welding. This layer of film evaporates as soon as it is heated during welding. The solder can weld the copper wire and the components together. But it is not resistant to corrosion. If an OSP circuit board is exposed to the air for about ten days, the components cannot be welded. The OSP process is mainly used in computer motherboards, because the circuit board area is too large, and gold plating is generally not used. The above is how to distinguish the three color surface treatment methods, how about it? After reading the article of the editor, do you think that if you get a board, you can also tell what process it is? PCB is simple and not simple, say It is not difficult. You have to study everything by yourself. You are also welcome to visit the factory. More knowledge is waiting for you to discover.
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