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The three-proof in PCB board processing refers to the abbreviation of "waterproof, moisture-proof, and dust-proof". After the production test is completed, the PCB circuit board is evenly coated with the circuit board three-proof paint, which is called the PCB board three-proof treatment.
Why should we carry out the three-prevention treatment? The three prevention treatment has the following advantages:
1. Protect the circuit board The protective film formed by the three anti-paints of the circuit board can effectively isolate the circuit board and protect the circuit from the erosion and damage of the harsh environment, thereby improving the reliability of the circuit board, increasing its safety factor, and ensuring its Service life.
2. Realize higher circuit board integration
In addition, because the three-proof paint can prevent leakage, it allows higher power and closer printed board spacing, which can meet the purpose of component miniaturization.
3. Modify the appearance of the circuit board
Both transparent and colored three-proof paint can improve the appearance of printed circuit boards, and the latter can ensure a higher degree of confidentiality by covering components and PCB design layout.
4. Insulate the tin feet between the circuit boards to prevent leakage, short circuit and other phenomena. Especially after the dust is deposited, the short-circuit phenomenon caused by the combined action of moisture.
5. Protect the tin points on the surface of the circuit board from oxidation by air to make it more beautiful and prevent dust from obstructing and affecting the normal operation of the circuit board.
The three-proof processing of PCB board is generally used in tropical electrical products, relays, small transformers, marine instruments, thermal instruments, precision instruments, carrier communication, protection of electronic components, and protection of positive machines, etc.
6 For the feeding and feeding of RF signals on the PCB, special RF coaxial connectors must be used. The most commonly used is the SMA type connector. For SMA connectors, it is divided into in-line type and microstrip type. For signals with a frequency below 3GHz, and the power of the signal is not large, and we don't care about the weak insertion loss, you can use the in-line SMA connector. If the frequency of the signal is further increased, we need to carefully choose the RF connection wire and RF connector. At this time, the in-line SMA connector may cause relatively large signal insertion loss due to its structure (mainly turning). At this time, a better quality microstrip SMA connector can be used (the key lies in the PTFE insulator material used in the connector) to solve the problem. Similarly, if your frequency is not high, but you are demanding indicators such as insertion loss and power, you can also consider a microstrip SMA connector. In addition, small RF connectors include SMB, SMC and other types. For SMB connectors, this type of connector generally only supports signal transmission below 2GHz, and the snap structure used in SMB connectors will appear in high vibration situations. The "flash" situation. So carefully consider when choosing SMB connectors. Most RF connectors have a limit of 500 plugs and unplugs. Too frequently plugging and unplugging may permanently damage the connector, so don't use the RF connector as a screw when debugging the RF circuit. Since the PCB socket of the SMB has a pin structure (male), the connector that is frequently plugged and butt welded at one end of the PCB has relatively little loss, which reduces the difficulty of maintenance. Therefore, in this case, the SMB connector is also a kind of Good choice. In addition, for those occasions with extremely high space requirements, there are also miniature connectors such as GDR for selection. For those whose impedance is not 50 ohms, low frequency, small signal, precision DC and other analog signals or digital signals such as high-frequency clocks, low jitter clocks, high-speed serial signals and other digital signals, SMA can be used as a feed-out connector. .
