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The common problems are false soldering, short circuit, electric leakage, breakdown, etc. How do we judge whether the patch capacitor is short circuited and electric leakage? Let's take a look at the specific judgment methods below
What are the phenomena of short circuit and leakage of SMD capacitors? Here is an answer for you.
When the chip capacitor is disconnected, the DC will form an open circuit, leading to abnormal operation of the DC circuit. In other words, when the chip capacitor fails, we can determine whether the capacitor is through or leakage by measuring the DC voltage of the Test point in the circuit. After capacitor breakdown, it will only affect the local circuit of the capacitor.
Because in other circuits, capacitors are still isolated from DC. According to this principle, the maintenance scope can be shortened.
Short circuit and leakage of patch capacitors occur in different circuits, such as coupling circuit short circuit. DC current will directly flow to the next stage, so there should be no current noise, and filter capacitor breakdown may cause fuse.
What is the measurement method for short circuit and leakage of SMD capacitors? There are several methods below.
Method 1: Generally, the resistance value of a small capacitor is infinite, and the abnormal resistance value is replaced. If the capacitance decreases and the multimeter cannot measure it, replace it directly.
Method 2: Use a multimeter to ground one pole to the other and measure both ends of the capacitor. The sound at both ends indicates a short circuit.
Method 3: If the capacitance of the patch is short circuited, a multimeter can be used to measure it online to determine. If it is an open circuit and the capacity is too small to measure a multimeter, you can use a pen to connect a 220V live wire and place the pin of the chip capacitor on the pen cap to see if the neon light bulb is emitting light and the emitting capacitance is good. Otherwise, the circuit will be cut off. 220V voltage, but do not experiment on the board.
Method 4: The resistance value is infinite, a zero resistance value is considered bad, and there should be some small changes in other values.
Summary of issues related to short circuit and leakage of SMD capacitors. During use, it is important to pay attention to the following reasons:
The decrease in surface insulation caused by surface dirt leads to leakage, and this leakage current is not very large, usually at the microampere level. Internal cracks, welding cracks, and MLCC cause severe self suppression cracks, and the leakage current caused by these cracks will continue to increase. In severe cases, it can cause local explosions and fires.