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PCBA repair and rework process

2021-09-26 15:50:01   Visit:68

1. The process purpose of PCBA repair and rework

① Solder joint defects such as open circuit, bridge, false solder and poor wetting generated in reflow soldering and wave soldering process need to be repaired manually with the necessary tools (such as: BGA rework station, X-ray, high-power microscope) Remove various solder joint defects to obtain qualified pcba solder joints.

②Repair the missing components.

③Replace the sticking position and damaged components.

④There are also some components that need to be replaced after the single board and the whole machine are debugged.

③Repair the whole machine after leaving the factory.

Second, the solder joints that need to be repaired

The following describes how to determine the solder joints that need to be repaired.

(1) Electronic products should be positioned first

To determine what kind of solder joints need to be repaired, you should first locate the electronic product and determine which level of product the electronic product belongs to. Level 3

It is the highest requirement. If the product belongs to Level 3, it must be tested according to the highest standard, because the third level product is based on reliability as the main goal; if the product belongs to Level 1, it is fine to follow the lowest level standard.

(2) It is necessary to clarify the definition of "good solder joints".

Excellent SMT solder joints are those that can maintain electrical performance and mechanical strength in the use environment, method, and lifespan considered by the design.

Therefore, as long as this condition is met, there is no need to repair it.

(3) Measure with IPCA610E standard. It is not necessary to use the soldering iron to rework if the conditions of acceptable level 1 and 2 are met.

(4) Detect with IPC-A610E standard, defect level 1, 2, 3 must be repaired

(5) Test with IPCA610E standard. Process warning level 1 and 2 must be repaired.

Process warning 3 refers to conditions that do not meet the requirements. But it can also be used safely. therefore. General situation process alert

It shows that level 3 can be treated as acceptable level 1, and repairs are not required.

3. PCBA repair and rework process requirements In addition to meeting the requirements of 1. SMC/SMD manual soldering process, add the following ③ requirements. When disassembling SMD devices, you should wait until all pins are completely melted before removing the device. To prevent damage to the coplanarity of the device.

Four, rework precautions

①Do not damage the pad

②The availability of components. If it is double-sided welding, a component needs to be heated twice: if it is reworked once before leaving the factory, it needs to be heated twice (disassembly and welding each heat once): if it is repaired once after leaving the factory, it needs to be heated again twice. According to this calculation, it is required that a component should be able to withstand 6 times of high temperature welding to be considered a qualified product. Therefore, for high-reliability products, components that may be repaired once cannot be used again, otherwise reliability problems will occur

③The component surface and PCB surface must be flat.

④Imitate the process parameters in the production process as much as possible.

⑤Pay attention to the number of potential electrostatic discharge (ESD) hazards. ①The most important thing for rework is to follow the correct welding curve.

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