PCB Technical - What is the principle of rework and repair for pcb board processing?

Not all PCB board processing manufacturers can guarantee that every design and processing will be without accident, sometimes due to various circumstances, the PCB board will have problems, which need to be reworked and repaired. However, the rework and repair of PCB board processing is not carried out casually, but has certain principles. What is the principle? Let's take a look.

1. The basis for the need to rework and repair the PCB board is that the design and production staff found that they are inconsistent with the actual after producing according to the PCB board design documents, and must be reworked, and this rework and repair also has a unified process and cannot be casual Mess around.

2. Each time in the PCB processing process, the number of solder joints allowed to be reworked is limited. Some novice PCB board processors think that as long as they are wrong, they can rework and repair them. It's no big deal. But in fact, according to the production principle, solder joint rework is limited to a certain number of times, basically no more than three times, otherwise it will cause damage to the soldering part, and then affect the performance of the PCB board. Therefore, once there are three rework situations, basically this PCB board will not be used again.

3. For the case of disassembling components during PCB processing and repair, in principle, the disassembled components cannot be used again. Even if it is to be used, it must be screened and tested to confirm that it meets the requirements before it can be used again. Here, the editor will give you a small reminder. In order to save costs, some small workshops or small manufacturers of unprofessional PCB processing will re-use the components that have been reworked and repaired. This approach is not correct. Yes, although the cost is saved, the performance is actually affected. Therefore, the low price of some small workshop-type PCB board processing plants is because of this.

Fourth, when the PCB board is processed, the number of desoldering on the pad is also specified. According to the designer of a regular PCB board processing manufacturer, each printed pad is basically a one-time operation, and only one component is allowed to be replaced, because a qualified solder joint will increase in thickness after remelting, resulting in a change in the solder joint. It is brittle and has reduced strength. In the event of vibration, it is extremely easy to bring safety hazards to electronic products. Therefore, regular PCB board processing manufacturers will not often de-soldering twice.

5. When remelting, the required temperature is higher, this temperature will have a certain impact on the PCB board, especially the IMC needs to be removed, so a certain high temperature must be maintained. The high temperature will cause the copper plating layer to fracture or deform, and eventually cause the pad to detach. In addition, in the case of lead-free, high temperature will also pull up the entire pad, and eventually heat up and delaminate, causing warping or separation.