CMA3000 Datasheet, PDF (15/18 Pages) VTI technologies – 3-axis accelerometer

CMA3000 Assembly Instructions
6 Rework Guidelines
There are several rework systems on the market. Some will heat solder joints directly from the
sides of component package, while others will direct heat on the top of component. Occasionally,
very rough rework methods are used such as hand placement and heating with a soldering iron.
However, these rough methods are not recommended for CMA3000 component. It is
recommended that the heat flow of hot-air convection directed at the edge and under the
component body directly to the solder joints and component pad areas would be used. Secondary
methods include a horizontal flow method, a conduction method, and a conduction heating from
the top of the package.
6.1 Preparations
Prior to the rework process, PWBs and components should be free from moisture. If necessary,
baking and drying processes should be performed.
The reflow profile for the component removal should be similar to the normal reflow process. A
carefully adjusted reflow profile is essential for the successful rework operation. A proper reflow
profile should be measured with thermo-couples. During the reflow profiling, at least the solder
joints, the top of the component, and the bottom of the PWB should be monitored. If there are
other components near the component to be reworked, the temperatures of those should also be
monitored. The bottom side heating of the PWB is recommended in order to reduce the PWB
warpage during the rework operation.
6.2 Component removal
Once the solder joints have been fully melted, the component can be carefully removed from the
PWB. The common rework methods for the component removal can be used, i.e. a vacuum nozzle
etc. It is absolutely necessary to ensure the complete melting of the solder joints before the
component lifting. If the solder joints are not fully melted before the lifting operation, pad damage
may occur on the PWB and the component.
6.3 PWB cleaning
After the component is removed, the pad areas of the PWB should be cleaned using common
rework methods. These include the applying of a rework flux, an excess solder and flux removal
using a vacuum solder removal tool or a solder wick and a soldering iron with a wide chisel tip, and
the cleaning of solder pads with alcohol and brush. The PWB cleaning process should be
performed gently as too high force or a scrubbing motion can cause pad lifting and trace damage.
6.4 Component reuse
It is not recommended to reuse the component.
6.5 Applying flux or solder paste
Prior to the placement of a replacement component onto the reworked PWB, solder paste or flux
should be applied onto the cleaned PWB pads. Recommended methods for applying solder paste
or flux are the usage of a micro-stencil or dispensing. If the micro-stencil is used, it should be
cleaned after each paste application to prevent clogging. For the solder paste and the stencil, the
same guidelines as for the normal reflow process should be used. The usage of solder paste over
mere flux is recommended due to an increased stand-off.
VTI Technologies Oy
www.vti.fi
PRELIMINARY
Subject to changes
TN68
15/18
Rev.09