After the circuit board is patched, many users will encounter the situation that the vias are blocked. In those cases, the vias will be blocked. According to personal past experience, I will share the reasons why the vias are blocked after the patch. Of course, this reason is due to the production of circuit board manufacturers on the one hand, and the reason of SMT on the other hand. Analyze both aspects.

　　1. Defects caused by the drilling of the circuit board

　　The board produced by the circuit board is made of epoxy resin glass fiber. Referred to as FR4 fiberglass board. After the circuit board is drilled, there will be a layer of dust in the hole. Especially drill holes above 0.3MM. If the dust is not cleaned, copper cannot be deposited in the dusty place after curing, which will cause the via hole to be blocked. The defects caused by drilling can be tested if the PCB has been tested. This kind of bad circuit board manufacturers can do scrap processing.

　　2. Defects caused by copper sinking

　　The first choice is that the time for sinking copper is too short. The hole copper is not full. When the tin is applied, the hole copper melts off and causes defects. Most of these appear in vias below 0.3MM. The second is that the circuit board needs too much current without thickening the copper. After the power is turned on, the current is too large to melt the copper in the hole, which will cause defects. Therefore, if there is a PCB board that requires excessive current, it must be told to the circuit board manufacturer to thicken the copper during production. For example, circuit boards such as power supply boards are almost always made of thick copper plates.

　　3. Defects caused by SMT tin or flux quality and technology

　　This type of situation mostly occurs in the vias of the plug-in. The tin used by SMT manufacturers is not pure, and there are too many impurities. And the quality of the flux is too poor. Tin and tin welding is not good. This is easy to cause virtual welding. Components do not work. In addition, there are technical problems in SMT, which makes the circuit board stop flowing for too long when it passes through the tin furnace during soldering. Cause the hole copper to melt. The resulting vias are blocked.

　　What are the application fields of high frequency board

　　High-frequency boards refer to special circuit boards with high electromagnetic frequencies, which are used for PCBs in the fields of high frequency (frequency greater than 300MHZ or wavelength less than 1 meter) and microwave (frequency greater than 3GHZ or wavelength less than 0.1 meters). The copper plate is a PCB circuit board produced by using part of the process of ordinary rigid circuit board manufacturing methods or using special processing methods. Generally speaking, a high-frequency board can be defined as a PCB circuit board with a frequency above 1GHz.

　　With the rapid development of science and technology, more and more devices are designed for applications in the microwave frequency band (>1GHZ) or even in the millimeter wave field (30GHZ), which also means that the frequency is getting higher and higher, and the impact on the PCB circuit board. The requirements for substrates are also getting higher and higher. For example, the substrate material needs to have excellent electrical properties, good chemical stability, and the loss on the substrate with the increase of the power signal frequency is required to be very small, so the importance of high-frequency boards is highlighted.

　　High frequency board application fields:

　　1. Mobile communication products;

　　2. Power amplifier, low noise amplifier, etc.;

　　3. Passive devices such as power dividers, couplers, duplexers, filters, etc.;

　　4. Automobile anti-collision system, satellite system, radio system and other fields.

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