"Rework" is the professional term for the refinishing operation or reparation of an electronic assembly (PCBA) in the "Surface Mount Technology". Usually a single defective Surface Mount Device of a PCBA is exchanged. The entire rework includes a few adaptations, which must be done one by one.
Obtaining a successfully reworked board requires of course no damage on surrounding units and the PCB itself. Consequently all parts of the treated conductor board are protected during the different processes. Further it is necessary to keep the thermal strain of the electronic assembly as low as possible and prevent unnecessary contractions of the board durability.
Separating a single SMD from the PCBA after all the solder joints between these two parts have been molten is generally the first step and called desoldering. Afterwards the pad array on the conductor board is cleaned from old lead. It is quiet easy to remove these rests by heating up above the area of melting temperature. In principle the exact positioning of the new unit onto the prepared pad array requires an automatic placement system which is controlled by an specialist. The smaller the pitch of the components the higher the demand for the precision device of alignment. Finally the just now placed SMD is soldered on the board. Reliable and high quality solder joints are created by an adapted solder profile which heats all the connections between the unit and the PCBA up to exceed the melting temperature and cools them down properly.
