  A novel open waveguide cavity resonator is presented for the combined
variable frequency microwave curing of bumps, underfills and encapsulants, as
well as the alignment of devices for fast flip-chip assembly, direct chip
attach (DCA) or wafer-scale level packaging (WSLP). This technology achieves
radio frequency (RF) curing of adhesives used in microelectronics,
optoelectronics and medical devices with potential simultaneous micron-scale
alignment accuracy and bonding of devices. In principle, the open oven cavity
can be fitted directly onto a flip-chip or wafer scale bonder and, as such,
will allow for the bonding of devices through localised heating thus reducing
the risk to thermally sensitive devices. Variable frequency microwave (VFM)
heating and curing of an idealised polymer load is numerically simulated using
a multi-physics approach. Electro-magnetic fields within a novel open ended
microwave oven developed for use in micro-electronics manufacturing
applications are solved using a de icated Yee scheme finite-difference
time-domain (FDTD) solver. Temperature distribution, degree of cure and thermal
stresses are analysed using an Unstructured Finite Volume method (UFVM)
multi-physics package. The polymer load was meshed for thermophysical analysis,
whilst the microwave cavity - encompassing the polymer load - was meshed for
microwave irradiation. The two solution domains are linked using a
cross-mapping routine. The principle of heating using the evanescent fringing
fields within the open-end of the cavity is demonstrated. A closed loop
feedback routine is established allowing the temperature within a lossy sample
to be controlled. A distribution of the temperature within the lossy sample is
obtained by using a thermal imaging camera.
