Many DIY players will find that the PCB color used in various board products in the market is dazzling. Common PCB colors with black, green, blue, yellow, purple, red and brown. Some manufacturers have also developed PCB of different colors such as white, pink.
In the traditional impression, the black PCB seems to be positioned on high-end applications, and red, yellow, etc. is low-end dedicated. Is it true if it is true?
PCB copper layer without coating resistant paint is exposed to air in the air is extremely easy to oxidize
We know that the PCB is in opposite sides of the copper layer. In the production of PCB, the copper layer is manufactured by the addition method or the reduction method, and it will finally get a smooth-free surface. Although the chemical properties of copper is not lively as aluminum, iron, magnesium, etc., pure copper and oxygen contact is easily oxidized under water; because of the air, oxygen and water vapor are present, the pure copper surface is in contact with the air. Oxidation will soon occur. Since the thickness of the copper layer in the PCB is very thin, the oxidation of copper will become a poor conductor of the electricity, which greatly damages the electrical properties of the entire PCB.
In order to prevent copper oxidation, in order to protect the welding portion of the PCB and the non-welded portion, the engineers invented a special coating in order to protect the PCB surface layer. Such coatings can be easily painted on the surface of the PCB, forming a protective layer having a certain thickness, and blocks contact of copper and air. This layer of coating is called a solder resist layer, and the material used is a barrier.
Since it is called paint, it must have different colors. That's right, the original solder welding lacquer can be made into colorless transparent, but the PCB often needs to print small text on the board for maintenance and manufacturing. Transparent resistant paints can only reveal the background of PCB, so that it is manufactured, maintenance is still sold, the appearance is not good enough. Therefore, engineers have added a variety of colors in the solder-weld paint, and finally forms black, red, and blue PCB.
Black PCB is difficult to see the line, bringing difficulties to repair
From this point, there is no relationship between the color of the PCB and the quality of the PCB. The difference in other color PCBs such as black PCB and blue PCB, yellow PCB is different in the last brush. If the PCB design, the manufacturing process is exactly the same, the color does not have any effect on performance, nor does it affect heat dissipation.
Regarding the black PCB, due to almost all of its surface traces, it has caused great difficulties to future repairs, so it is less convenient for manufacturing and use. Therefore, in recent years, people have gradually reform, giving up using black soldering paints, turn deep green, dark brown, dark blue, etc., the purpose is to facilitate manufacturing and repair.
Speaking here, everyone has basically clear the problem of PCB color. The reason why the "color representative is high-end or low-end", that is because the manufacturer loves to use black PCB to create high-end products, leading to red, blue, green, yellow and other low-end products. Summarizing a sentence is: The product gives the color meaning, not the color gives the product meaning.
What is the benefit of gold, silver and other precious metals?
The color is clear, and then the valuable metal on the PCB is coming. Some manufacturers will specifically mention their own products, and special processes such as gold plating, silver plating are specifically mentioned in promoting their products. So what is the use of this craft?
The surface of the PCB requires welding elements, requiring some copper layers to be exposed to welding. These exposed copper layers are called pads, and the pads are generally rectangular or circular, and the area is small. We know that the copper used in the PCB is easily oxidized, so after brushing the solder welding paint, the only exposure to the air is the copper on the pad.
If the copper on the pad is oxidized, it is not only difficult to weld, but the resistivity is increased, which seriously affects the final product performance. Therefore, engineers have thought of various ways to protect the pads. For example, a layer is plated with an inert metal or covers a layer of silver by a chemical process, or a copper layer is covered with a special chemical film, and contact of the air is blocked.
The soldering discharged on the PCB, the copper layer is directly exposed to the outside. This part needs protection to prevent it from being oxidized. From this perspective, whether it is gold or silver, the purpose of the process itself is to prevent oxidation and protect the pads, so that it ensures good rate in the next welding process.
However, different metals will be made to the storage time and storage conditions of the PCB used by the factory. Therefore, the PCB plant generally has completed the production of PCB, before delivery, using a vacuum plastic machine packaging PCB, minimizes whether PCB does not have oxidative damage.
And before the last component is welded, the board manufacturer also detects the degree of oxidation of the PCB, and eliminates the oxidation of the PCB to ensure good rate. The final consumer has already passed various tests, even if oxidation after long use, almost only insertion of the connection, and the weld and the welded components, there is no impact.
Because silver and gold have lower resistance, will it reduce the amount of heat during use when using special metals such as silver and gold?
We know that the biggest factor affecting the heat is the resistance. The resistance is also related to the material of the conductor itself, the cross-sectional area of the conductor, and the length. The metal thickness of the pad surface is even less than 0.01 mm, and if the OST (organic protective film) is used, there is no extra thickness at all. The resistance exhibited by such a small thickness is almost equal to 0, and even can't calculate, of course, it will not affect the amount of heat.
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