The Rework process involves two main stages: desoldering and re-soldering. Each of these stages improves the efficiency of surface-mounted electronic components. Since mass techniques cannot be applied to repair a single device, the rework process is widely used to repair electronic equipment, such as a mobile phone. It is usually performed by skilled personnel who have a lot of experience replacing defective parts of electronic devices. In this process, skilled personnel use a hot air station to melt solder and utilize tools to place tiny components in proper positions.
Desoldering is an essential part of reworking. It removes components and solder in order to allow a skilled professional to diagnose, repair, and possibly replace the parts that were causing a malfunction. In order to do desoldering successfully, you have to use such tools as a desoldering pump, solder wick, heated soldering tweezers, various picks, and removal alloys, not to mention pressure pumps and removal fluxes. You also have to be skilled with heat guns. Another tool that you will need at this stage of reworking process is the rework station. It is used to restore circuit board assembly.
Resoldering is another essential part of reworking. During this process, melting is used to join separate metal items. Then the filler metal - called solder - is added to the joint. Most of the time, adjoining metal has a higher melting point than the filler metal. This process is very different from welding because during this process the work components are not melted.
In the last century, almost all solders had a lead component. This has changed. The concern for environmental safety has created regulations that prohibit the use of lead alloys when manufacturing electronic equipment.
There are many reasons people rework their electronic equipment. The most common ones are faulty components, the need to change out-dated engineering parts, poor solder joints, and unwanted drops of solder. Some of this work occurs during the repair of mobile phones.
When doing a rework, skilled professionals have to protect surrounding parts. They do this by keeping thermal stress on the assembly line at the lowest level possible. This helps avoid potentially dangerous contractions of the board.
The first step of rework is using hot-air gun to heat a single surface-mount device. This melts all solder joints between the printed circuit board and a surface-mount device. The second step of rework is removing the surface-mount device, and the third step is to clean the pad array on the conductor from an old solder. An old solder is easily removable. All you have to do to remove it is to heat it to melting temperature. A desoldering braid and a hot air gun are used for that purpose, as well as a soldering iron.
In order to complete the steps above, skilled professionals use vision-alignment system. The top of the line equipment have a high resolution and are highly accurate. This system enables the new component to be precisely placed on the pad array.
Once everything is done, a surface-mount device is soldered on the circuit board. The solder profile is used to preheat the circuit board. It is also used to heat connections between the printed circuit board and the device.
And the job is done!