|
During IC encapsulation filling process, the epoxy would exert
drag force on wires and cause wire sweep. If the neighbor wires
touch, short-circuit occur. With the trend of more wires, less
wire distance and thinner the cavity depth, wire sweep problem
would become serious and critical.
We observe the flow pattern and wire sweep in different mold
cavity shape with flow visualization facility. We also
investigate the influence of various parameters in TCCM
(Transfer Charged Compression Molding).
With the same Reynolds number. The wire sweep is larger in
circular mold cavity than that in square cavity. During the
same filling time. The wire sweep difference between circular
cavity and square cavity is not very significant.
During TCCM process. The wire sweep becomes larger with
faster compression speed and larger compression ratio. We could
introduce higher flow rate and would not cause serious wire
sweep.
PBGA (Plastic Ball Grid Array) is a rising and popular IC
packaging technology. However, due to its unsymmetrical shape
and the difference of CTE between its consisted components.
PBGA is easy to warp during thermal cycling. It’ll reduce it
yield.
This study use ANSYS to analyze warp of PBGA during thermal
convection by building up various 3D finite element model,
changing EMC shape and adding ribs on it. We conclude that
adding ribs on square EMC would enhance the stiffness of PBGA
during thermal cycling, but circular EMC do not have
significant effect.
|