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PCB short-circuit inspection method

For electronic engineers, PCB fabrication is an inevitable step, while the short circuit is a relatively easy problem in the board manufacturing process. A short circuit may cause the component burned out, causing the system out of work, so we must pay attention to it. I will analyze what is the main reason for the short circuit on the board?

There are two situations that a short circuit occurs. One is that the pcb board has reached a certain useful life. The second case is that the inspection work is incomplete in the pcb manufacturing process . However, the small mistakes in these productions are very harmful to the entire pcb circuit board, which is likely to cause scrapping. So how do we check and prevent circuit board shorts?

Method 1

If it is manual soldering, we should develop good habits. Firstly, we should inspect the PCB board visually before welding, and check whether the key circuits (especially power supply and ground) are short circuit with a multimeter. Secondly, a chip is welded, Using a multimete to test whether the power supply and ground are short circuit after chip is solderd each time ; Also, do not shake the soldering iron while soldering. If the soldering tin is thrown onto the soldering feet of the chip (especially the SMD elements), it will not be easy to find.

Method 2

Open PCB deisgn on the computer, light up the short-circuited network, and check where it is closest and most easily connected. Pay special attention to IC internal short circuit.

Method 3
A short circuit was found. Take a plate to cut the line (especially for single/double plate), and turn each functional block on separately after cutting the line.

Method 4

Using a short circuit positioning analyzer , such as Singapore PROTEQ CB2000 short circuit tracker, Hong Kong lingzhi technology QT50 short circuit tracker, POLAR ToneOhm950 multilayer road short circuit detector, etc.

Method 5

If there is a BGA chip, since all welding points are covered by the chip and cannot be seen, and it is also a multi-layer board (more than 4 layers), it is better to separate the power supply of each chip when design it and connect each chip with magnetic beads or zero-ohmic resistance. when a short circuit occurs between the power supply and the ground, the magnetic beads can be disconnected in this way, and it is easy to locate a chip. Due to the difficulty of BGA welding, if it is not soldered by automatic welding machine, it will cause short-circuit between the adjacent power source and two welding balls.

Method 6

Be careful when welding small-sized capacitor, especially the power filter capacitance (103 or 104), which is large in quantity, can cause short circuit between power supply and ground easily. Of course, sometimes the capacitor itself is short-circuited by bad luck, so it is better to check the capacitor before welding.

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