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Soldering and Desoldering
Introduction
Having done the preparation, you are now ready to begin SMT/BGA rework. The basic SMT process for soldering a
component is as follows:
1.
Material Science (ESD, Moisture, Contamination, Components, PCB, Flux and Solder)
2.
Alignment/Placement
3.
Reflow
4.
Test
Material Science
To get a high yield at the point of testing you need to develop an effective SMT/BGA Rework process and control
all parameters in stages 1, 2 and 3 above. However, in practice when problems occur it is easy to overlook
material science issues when trying to sort rework process problems. Moisture, contamination, ineffective flux
activity, solder issues all need to be constantly reviewed and effectively controlled.
It is not easy but it is important to exercise all the same care in SMT/BGA rework as is applied throughout the
various stages of a typical SMT line.
BGA Alignment System and Placement
The PDR Rework system can be purchased with, or without, a CCTV/Prism based BGA alignment system. In practice
it may not be needed as BGAs are often placed within very accurate PCB markings to aid pick and place systems. For
this reason, we have made the feature optional and fully upgradeable at a later date. The procedure for aligning
and placing a BGA with the BGA alignment system is as follows:
1.
(X410 0nly) lock pick-up and vision arms (using the black locking levers at the rear of the arms) before
alignment and placement.
2.
Lower Component to 1mm above PCB and ‘macro’ or approximately align X/Y/rotation