guarantee initial plasticity and flowability of the pellet. Pre-heating
of the substrate increases thermal uniformity and adhesion between
substrate and polymer. The pellet is crushed by a plunger,
increasing thermal contact to the hot tool and melting (step B).
After this preconditioning the plunger presses the polymer through
the film gate and into the cavity on top of the PCB (step C). Specially
designed shaping structures (labeled ‘‘3”) can be used to
achieve sufficient shear heating within the EMC and a homogeneous
flow front at the gate. After filling of the cavity the EMC is
pre-cured for about a minute to guarantee sufficient gelation and
therefore adequate contour accuracy during removal of the substrate
(step D). In most applications the parts are post-cured afterwards
at the mold temperature for several hours. Our mold tool
was equipped with a PZT pressure sensor from Kistler (labeled
‘‘4”). Small marks of the sensor can be seen on the overmolded substrate
(labeled ‘‘5”).