How to Inspect and Prevent PCB Short Circuit

- Dec 11, 2017-

PCB short circuit is the most common problem, there are two kinds of short circuit, one is the PCB has reached its service life.The second one, there is a short-circuit phenomenon in PCB production but the inspection is not in place.However, the small mistake in these production can lead to large damage to the whole PCB circuit board, very likely to cause PCB scrapped. So how do we inspect and prevent PCB short circuit? Here's a brief introduction.

PCB circuit boards

1. Find short circuit phenomenon.Take a piece of circuit board and cut the lines (especially be suitable for single/double layers PCB). After cutting, electrify each function part respectively and some will be eliminated.

2. SMT capacitor with small size must be careful when welding, especially for power filter capacitor (103 or 104), due to quantity large, it is easy to cause power and ground short circuit. Of course, sometimes due to bad luck, will encounter the station that capacitor itself is short circuit, so the best way is to inspect capacitor first before welding.

3. If it is manual welding, develop good habits.

(1) first, inspect PCB boards before welding, and check whether the key circuit (especially the power supply and ground) is short-circuited by the multimeter.

(2) Use a multimeter to measure if the power supply and ground have short circuit after welding one chip at a time;

(3) when soldering, do not throw the soldering iron. If you throw tin into the soldering foot of the chip (especially the SMT components), it is not easy to be found.

4. Open the PCB diagram on the computer, light up the short circuit network, and find which two are the nearest and the most likely to be connected together.Special attention to the internal short circuit of IC.

5. Use the short circuit positioning analyzer, such as: CB2000 short circuit tracker, QT50 short-circuit tracker, ToneOhm950 multi-laminated circuit short-circuit detector, etc.

6. if there is a BGA chip, because all solder joints are covered by chip invisiblely, in the meantime it is a multilayer(above 4 layer), so it's best to depart each chip power when design and connect with magnetic beads or zero resistance. Then when power and ground have short circuit, disconnect magnetic beads to do test, it is easily to locate the chip. Since BGA is difficult to weld, if it is not welded by machine automatically, it will beshort-circuit for the adjacent power supply and the ground.

PCB inspection should not be ignored, every step need to make inspection work,we must treat it carefully, can't let go of any one suspect in the production process, which can reduce rework rate and product scrap rate, so avoid unnecessary loss.