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MICRONANOSYSTEMS
manufacture. With a very high power to mass
ratio, Watlow’s ULTRAMIC 600 advanced ceramic
heater makes it easier for devices to be constructed
that are smaller and lighter weight without
sacrificing performance.
As a machineable heater, it is capable of becoming
an integral part of the design thereby lowering part
count, simplifying assemblies and ultimately
improving performance. For example, clam shell
designs provide a very efficient approach to
heating small tubes for flowing liquids and gases
whereas flat rings or rectangular forms easily
accommodate mounting applications.
This process of developing custom designs is
completed by carefully considering the environment
and defining the boundary conditions. The heating
element pattern is optimised using the FEM
technique. Infrared images of the AlN heater performance can be achieved without the Clam shell designs
reveal excellent temperature uniformity of +/-2°C disadvantages of high initial cost and complexity provide a very
at 400°C steady state. associated with many other cooling technologies. efficient approach to
heating small tubes
Getting performance Conclusion for flowing liquids
requirements right The push for productivity, increased consumption of and gases
In addition to uniform temperature distribution, semiconductor devices and limited space in
the heater must provide a fast heat-up rate for the complex machinery will continue to drive the need
short die bonding cycle. Collected data indicates for component improvements in all areas of
that an AlN heater takes about 10.5 seconds to semiconductor and microelectronic’s manufaturing.
reach 400ºC when powered at 250 wsi power Speed and thermal repeatability are improving When power input is
input. When power input is increased to 1000 wsi, back end productivity in semiconductor increased to 1000
a linear temperature profile with a heating rate applications as a continuous process. wsi, profile
approaching 150°C per second is achieved and To achieve these improvements, choosing the approaching 150°C
takes less than three seconds to reach target correct materials, using FEM to optimise per second is
temperature. Such a heating rate exceeds the performance, and understanding thermal and achieved and takes
typical 100ºC per second requirement for die cooling requirements to help build a heater will less than three
bonding applications. Finally, a small overshoot of ensure a tool that provides the desired performance seconds to reach
less than 5ºC at 400ºC can be easily achieved and efficiencies for a chosen application. target temperature
using a self tuning PID controller even at 150ºC
per second ramp rate.
Cooling the heater
The development of AlN heaters has made rapid
heating of small parts and assemblies possible. For
applications requiring cyclic heating and cooling,
compressed air is one method for quick cooling
that should be considered. Compressed air is widely
available, does not typically create concerns
related to leaks, accommodates the range of
common heater operational temperatures and can
be easily integrated into production equipment
since it requires relatively simple, small,
lightweight components and does not complicate
electrical isolation requirements. When a system
operating on a thermal cycle is appropriately
designed to use forced air as a coolant, good
REFERENCES: of Missouri-Rolla. Jim Kreisel is director of industry marketing
Dr. Hongy Lin is a Principal Scientist and advanced ceramic in the life science and semiconductor industries for Watlow.
heater development team leader at Watlow. Kreisel has more than 27 years experience at Watlow, leading
Dr. Lin holds a Ph.D. in ceramic engineering from the University numerous product and market development projects.
www.micronanosystems.info July 2008
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