PCBA Tech - Principles and methods of desoldering for PCBA processing

In PCBA processing, after checking the welding quality of electronic components, it is necessary to disassemble and weld the electronic components with poor welding. If you want to remove the electronic components with incorrect welding without damaging other components and PCB board, you must master PCBA processing and disassembly welding skills. Next, I will introduce the desoldering principles and key points of PCBA processing.

1. Basic principles of desoldering for PCBA processing:

Before disassembling welding, the characteristics of the original welding point must be clarified. Do not do it easily.

1) Do not damage the components, wires and surrounding components to be removed;

2) Do not damage the bonding pad and printed wire on the pcb when removing the soldering;

3) For the electronic components that have been judged to be damaged, the pins can be cut off first and then removed to reduce the damage;

4) Try to avoid moving the position of other original components, and if necessary, do a good job of restoration.

2. Key points of desoldering for PCBA processing:

1) The heating temperature and time shall be strictly controlled to avoid damaging other components due to high temperature. Generally, the time and temperature of desoldering are longer than those of welding.

2) Do not use excessive force when disassembling welding. The packaging strength of components under high temperature decreases, and excessive pulling, shaking and twisting will damage components and bonding pads.

3) Remove the solder from the solder joint. Solder can be absorbed by the tin absorbing tool, and the components can be directly unplugged to reduce the desoldering time and the possibility of damaging the PCB board.

3. Dismantle welding method for PCBA processing:

1) Split point desoldering method: for resistance capacitance components installed horizontally, the two welding points are far away, so electric soldering iron can be used for split point heating and point by point extraction. If the pin is bent, pry it with a soldering iron head and then remove it. During desoldering, erect the PCB, heat the pin solder joints of the components to be disassembled with an electric soldering iron, and gently pull out the component pins with tweezers or pointed nose pliers.

2) Centralized desoldering method: since each pin of the row resistor is welded separately, it is difficult to heat it at the same time with an electric soldering iron. You can use a hot air welder to quickly heat several welding points, and pull them out once after the solder melts.

3) Preserve the desoldering method: first, use the tin absorbing tool to absorb the solder of the desoldered joint. Generally, components can be removed. In case of multi pin electronic components, the electronic hot air fan can be used for heating. If the components or pins are overlapped, the solder joint can be dipped with flux, the solder joint can be opened with an electric soldering iron, and the pins or wires of the components can be removed. If it is a hook welded component or pin, first remove the solder from the solder joint with an electric soldering iron, and then heat it with an electric soldering iron to melt the residual solder under the hook. At the same time, use a blade to lift the pin in the direction of the hook. Do not use excessive force when prying to prevent molten solder from splashing into eyes or clothes.

4) Cutting and desoldering method: if there is any margin in the component pins and wires on the removed solder joints, or if it is determined that the components are damaged, the components or wires can be cut off first, and then the wire ends on the bonding pad can be removed.

4. Precautions for rewelding after disassembly of PCBA processing:

1) The soldered component pins and wires shall be consistent with the original as far as possible;

2) Penetrate the blocked pad hole;

3) Restore the moved components.

In the face of such electronic components, we will generally remove the electronic components with incorrect welding without damaging the PCB board. These are the principles and methods of desoldering for PCBA processing.