There are several ways for the chip processing factory to check the short circuit of the PCB circuit board. The first is to open the PCB design diagram on the computer, light up the short-circuit network of the pcb board, and see where it is closest, and it is easiest to connect a piece. Special attention should be paid to the short circuit inside the IC.

If it is manual welding in the pcb factory workshop, you also need to develop good habits:

 1. Visually inspect the pcb board before welding, and use a multimeter to check whether the key circuits (especially the power supply and ground) are short-circuited;

 2. After each chip is soldered, use a multimeter to check whether the power supply and the ground are short-circuited;

3. Do not throw the soldering iron around while soldering. Short circuit phenomenon; take a board and cut the line (especially suitable for single/double-layer board), after the line is cut, energize each part of the function block, and gradually eliminate it.

Using a short-circuit positioning analyzer, if there is a BGA chip, since all the solder joints are covered by the chip and are not visible, and it is a multi-layer board (more than 4 layers), it is best to separate the solder joints when designing the power supply for each chip, and use magnetic beads or 0 ohm resistor connection, so when the power supply is short-circuited to the ground, the magnetic bead detection is disconnected, which is convenient for locating a certain chip. Due to the difficulty of soldering the BGA, if it is not automatically soldered by the machine, the two adjacent power and ground solder balls will be short-circuited accidentally.

Be careful when soldering small surface mount capacitors, especially power filter capacitors (103 or 104). When the pcb circuit board is repaired, if it encounters a short circuit of the public power supply, it is often a big problem, because many electronic components on the pcb circuit board share the same power supply, and every device using this power supply is suspected of short circuit. There are not many electronic components, and the short-circuit point can be found by "hoeing the ground". For the external capacitor on the pcb circuit board, you can use diagonal pliers to cut off one foot (be careful to cut from the center, do not cut the root or cut the circuit board), the plug-in IC can cut off the VCC pin of the power supply, when a foot is cut off When the short circuit disappears. , the chip or capacitor is shorted. If it is a SMD IC, you can use a soldering iron to melt the solder on the IC power pins and lift them up to keep them away from the VCC power supply. After replacing the shorting element, re-solder the cut or raised part.

There is also a quick method, but it requires a special instrument: a milliohmmeter. We know that the copper foil on the PCB circuit board also has resistance. If the thickness of the copper foil on the PCB is 35um, the printed line width is 1mm. , then every 10mm in length, the resistance value is about 5mΩ, such a small resistance value cannot be measured with a common multimeter, but it can be measured with a milliohmmeter.

Now let's assume that some component on the pcb board is shorted. It is measured as 0Ω with an ordinary multimeter, and it is about tens of milliohms to hundreds of milliohms measured with a milliohmmeter. When measuring the two feet of the short-circuit component on the pcb board, the obtained resistance value must be the smallest (because if the two feet of the component on other pcb circuit boards are measured, the obtained resistance value also includes the copper foil traces on the circuit board. resistance value), so we decided to compare the resistance value difference of the milliohmmeter. When the resistance value obtained by a component (if it is a short circuit of solder or copper foil, the same is true), then the component of the pcb board is the key to suspecting things, so that the obstacle point can be quickly found.