My views on circuit board Welding

After several circuit board welding experiences and lessons, we will summarize the circuit board welding skills and steps:

1. Check whether the circuit board has obvious faults.

For example, some cables in the circuit board are broken due to processing, or the line width is uneven, or there is an open circuit between the line and the passing hole, and so on. Once, when welding the USB _ board core board, we didn't pay attention to this issue.After finishing ep2c8, we found that JTAG was not easy to use because an open circuit occurred when a communication line passed through the hole, the lead I/O line is connected to the pad and there are also multiple circuit breakers, which eventually leads to welding failure.

2. Tin Plating, this step is mainly because the pad on the board is too small to avoid the phenomenon of virtual welding.

After many circuit board debugging lessons, n many problems are caused by virtual soldering, so in order to overcome this problem, if the solder pad on the circuit board has less Tinning, human Tinning should be performed on the Solder Pad, the pad here mainly refers to DSP, FPGA,Such as Ram and flash. In addition, tin plating must be even. If it is uneven, it may cause trouble when placing the chip.

3. welding sequence.

First, weld the power supply to ensure that the power supply voltage of each part is normal;

Secondly, major chips such as FPGA and DSP are welded to ensure that the JTAG works properly.ProgramNormal operation, such as led;

Again, the memory chip is welded one by one and tested one by one to ensure normal read/write operations.

Finally, the remaining parts such as the filter capacitor are welded.