OL #1–May–Micro Substrates–SC– Page
Ceramic substrate allows mounting of devices directly on vias
Traditionally, packages used for microwave applications have been
prohibitively expensive because of the costly glass-to-metal seals used in
them. Now a patented ceramic substrate from Micro Substrates (Tempe, AZ)
called the Via/Plane promises both cost and performance benefits for
microwave and other high-performance applications. Micro Substrates uses
a patented technique to metallize and fill vias with a tungsten-copper
composite rather than copper only. In the process, the vias are first
laser-drilled in a prefired substrate. A tungsten-copper metallization
layer is then deposited in the via. Subsequent steps include
high-temperature sintering, secondary metal infiltration, and liquid phase
sintering. The advantage of the Via/Plane substrate is that the
tungsten-copper composite deposited into the vias more closely matches the
thermal coefficient of expansion of the ceramic than the usual copper-only
material. With this arrangement, devices can be mounted directly on the
vias. This in turn shortens the path to the ground plane, reducing
inductance and improving electrical performance. Besides improving
performance, the ability to mount devices on the vias improves heat
transfer and permits higher mounting density. Substrates can be made
larger and with fewer layers than, for example, a cofired multilayer
ceramic package. The table lists performance and physical characteristics
for the substrate. According to Ramachandra Panicker, president of Micro
Substrates, a single-chip package made using the Via/Plane substrate
typically costs $0.05 to $0.07 per I/O pad. By contrast, a cofired
multilayer ceramic package costs $0.10 to $0.15 per I/O. Several
applications exist for the prefired substrate. It can be used for
microwave device packages having operating frequencies as high as 26 GHz.
The substrate can also be used to replace hermetic metal cans having
glass-to-metal seals for MMIC packages. The company is also using the
substrate in multichip module packages which incorporate features like
integral decoupling capacitors and termination resistors. According to
Panicker, a single-chip package made using the ceramic substrate would
typically costs $0.05 to $0.07 per I/O pad, compared with $0.10 to $0.15
per I/O pad for a cofired multilayer ceramic package. Micro Substrates is
looking to license the technology to interested companies. For more
information, contact Ramachandra Panicker, Micro Substrates Corp., Tempe,
AZ, at 602-731-6230, or . –Spencer Chin
Table is on file OL1TABLE.MAY
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