PCB is a important product.so when we buy it, we sholud know the quality of pcb.today i will tell you How to Know if a PCB Is Bad. 10pcb.com is a great pcb manufacturer from china.

1.Test the PCB with the power on, if electronic components are installed. A motherboards is an example of a PCBA. If it's a motherboard you will know it is bad if no lights come on or sound is made soon after power-up. This test works with any PCB that has similar light and sound test functions built in.

2.Remove any power source from the PCB if one exists. Also remove any electronic components if they exist by clipping the connection wires with wire cutters and pulling them away from the board. Unplug anything that doesn't require cutting.

3.Look for scratches, burn marks or misplaced solder. These are clear signs that the board is at least partially bad and needs professional work or replacement. Scratches can expose and damage the copper connections beneath the lamination. Extra solder can cause a short which is a unneeded connection and compromises other connections. Do not proceed to test if any of these things are present. Doing so could cause harm.

4.Ground the board at one of the screw holes for mounting using a ground lead provided with your tool. Use the voltmeter or oscilloscope to test for appropriate voltage across each connection in the PCB schematic by applying probes to each end of the connection with specified voltage.

5.Record the results of each connection and compare them to the details of the PCB schematic. If any or multiple connections are not conducting the right voltage then the PCB is bad.