(1) Single-handed automotive antenna PCB board, whICh is SMAll size, light weight, no BGA, no chip capacity of the circuit board is generally allowed; But for what size, heavy mass, side layout BGA, chip capacitor circuit board, absolutely should be avoided. Because such behavior is easy to cause the failure of the solder joint of BGA, sheet volume and even sheet resistance. Therefore, in the process document, should indicate how to take the circuit board requirements.
The easiest part to hold a car antenna PCB board with one hand is the circuit board cycling process. Most people unconsciously adopt the practice of holding a car antenna PCB board with one hand, either when removing the board from a conveyor belt or placing it, because it's convenient. When welding by hand, paste the radiator and install the screws. To complete an operation, you will naturally use one hand to manipulate other work items on the board. These seEMIngly normal operations often hide huge quality risks.
(2) Screw installation, in many SMT patch processing factories, in order to save costs, no tooling. When A screw is instalLED on the PCB board A of the automobile antenna, it is often deformed because of the uneven components on the back of the PCB board A of the automobile antenna, which is easy to crack the welding spot sensitive to stress.
(3) Insert through-hole components
Through-hole components, especially transformers with thick lead wires, are often difficult to accurately insert into the installation hole because of the large position tolerance of the lead wires. The operator will not try to find a way to correct, usually using a hard pressing operation, which will cause the bending deformation of the antenna PCB board, also will lead to the damage of the surrounding chip capacitor, resistance, BGA.
First, maintenance to understand the vulnerable parts on the circuit board
l, Improperly designed places tend to break down first
industrial circuit board in the end where the design is not reasonable? First of all, the heat dissipation problem, a lot of circuit board damage is because of the heat dissipation design is not good; The second is printed board copper foil line, poor quality circuit board power supply line copper foil is very thin, easy to burn due to the current, so that the motherboard can not work.
2, frequently used places prone to failure
For example, industrial circuit board drive motor, rotating shaft, switching power switch tube, operation panel commonly used keys.
3. Components with heavy load, high power and high working voltage are most prone to failure
The power supplies, driving circuits, power control devices, and operational amplifiers of industrial circuit boards are most likely to be damaged; these components are usually next to heat sinks; they will easily become the first 'victims' if insufficient protection and heat dissipation measures are taken first.
4. Protective circuits are easily damaged
The valuable chips or components on the circuit board of the Circuit board factory are protected. If the equipment is abnormal, the first sacrifice is these protective circuits. These protective devices should be instantly recognizable during maintenance.
5. The interface and line of the inline seat and connector are easy to contact poorly or break the line
For example, the board and slot contact is bad, the cable is broken when the internal through, the wire plug and terminal contact is not good, components welding, etc.
Two, industrial circuit board commonly used components damage characteristics and detection
Industrial circuit board damage is usually a component damage, may be a chip, a capacitor, or even a small resistor, the repair process is to find the damaged component to replace.
1. Small resistance and large capacity of electricity are easy to break
Small resistance is often used to limit the current on the power supply line, that is, to play the role of fuse, if the current is too large, the first will be burned off. In addition, many ground capacitors are used to filter the power supply line, and the head and capacity are generally large. If the voltage or current is unstable, it will breakdown the capacitance and lead to leakage.
2. Fault characteristics and maintenance of capacitor damage
Failures caused by capacitor damage are the highest in electronic equipment, especially those caused by electrolytic capacitors. Capacitor damage is manifested as: 1. Capacity becomes smaller; 2. 2. Complete loss of capacity; 3. Electric leakage; 4. Short circuit.
3, operational amplifier is good or bad discrimination method
No matter what type of amplifier, there is a feedback resistance Rf, we can check this feedback resistance from the circuit during maintenance, use a multimeter to check the resistance between the output and the reverse input. If it is too large, such as more than a few MΩ, then we can probably be sure that the device is used as a comparator; If the resistance value is smaller 0Ω to dozens of kΩ, then check whether there is no resistance connected between the output and the reverse input end, if there is a must be used for amplifier. According to the principle of virtual short amplifier, that is, if the operational amplifier is working properly, its co-input and the opposite input voltage must be equal!
Three, maintenance should be "chest frame"
How to repair industrial equipment in the absence of relevant information?
You can draw inferences from one example to the next. For example, switching power supply, always inseparable from the oscillation circuit, switching tube, switching transformer, check whether the circuit vibration, capacitor damage, each transistor, diode damage, etc. In addition, it is necessary to pay attention to the maintenance order so as to find the shortest path to solve problems, so as to avoid poking and dismantling randomly, which will fail to repair and otherwise lead to greater faults.