The harm caused by short circuit to PCBA board mounted by SMT machine is quite large, from small to burn components, to scrap PCBA. We can try to avoid short circuit, grasp every step of production, inspection does not let go of every suspect. So how to check and prevent PCB short circuit?
1. If manual welding, to develop good habits.
First of all, the PCB should be visually checked before welding, and the key circuit (especially power supply and ground) should be checked with a multimeter for short circuit. Second, every time after welding a chip, use a multimeter to test whether the power supply and the ground are short-circuiting. In addition, do not throw the soldering iron when welding, if the solder is thrown to the chip solder foot (especially the surface attached components), it is not easy to find.
2. Open the PCB map on the computer, light up the short-circuit network, and see where is the closest to the most easily connected to a piece. Pay special attention to IC internal short circuit.
3. A short circuit is found. Take a board to cut the line (especially suitable for single/double board), after cutting the line, electrify each part of the function block separately, one part of the exclusion.
4. Use short circuit to locate the analyzer.
5. Be careful when welding the small size table stick capacitor, especially the power supply filter capacitor, the number is large, it is easy to cause the power supply and ground short circuit. Of course, sometimes, unfortunately, the capacitor itself is short-circuited, so the best way is to test the capacitor before reflow oven.
6. If there is a BGA chip, because all solder joints are covered by the chip can not be seen, and it is multi-layer board (more than 4 layers), it is best to split the power supply of each chip in the design, with magnetic beads or 0 Ohms resistance connection, so there is a short circuit between the power supply and the ground, disconnect magnetic beads detection, it is easy to locate to a chip. Due to the difficulty of BGA welding, if the machine is not automatic welding, a little attention will short-circuit the adjacent power supply and the two welding balls.
