Dragon Group China Bird AC-5K, Manual

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中龙集团
Dragon Group China Limited
BIRD
®
www.dragongroupchina.com
www.chinaemall.biz
Generally, before mounting a new BGA, the paste should be laid on the pad with a
special micro mesh. But for those common devices such as PBGA or MBGA, the paste
can be laid on the pad directly, and the soldering can be finished by the melting of
soldering balls. Of course, for CBGA, a mesh and soldering paste are necessary, because
the melting point of soldering balls on CBGA is much higher than common paste, such as
Sn63 and pb27.
4. Removal of residual soldering tin and mounting of BGA
Besides the temperature curve, the removal of remained soldering tin and mounting
of BGA are of great importance in BGA rework. Generally, people don't realize it. But in
practice, it often leads to failure in BGA rework.
We usually use copper tin-absorption line to remove the residual tin. In the rework
process, the pad is likely to be destroyed by the wrong operation of the technician, thus
the total process of BGA rework becomes a failure. Therefore, we should pay more
attention. Here are 2 tips: one is to remove the residual tin within a short time after
desoldering BGA. Because at that time PCB has not cooled down completely and the
temperature difference cause less damage to the pad; the other tip is to use some flux
when removing the residual soldering tin, which can improve the activity of tin. Never
move the copper tin-absorption line under the great pressure of soldering iron. The
remounting of BGA calls for the "fine finish" of tin removal. Thus it ought to be operated
by some experienced technicians.
5. Use of nozzle
Every hot-air heating rework station need a suitable nozzle. It is better to use a
nozzle which is 2-5mm bigger than the component, then the component is entirely
covered by the nozzle, and BGA can be heated evenly.