| Advanced Ceramic Heaters Improve IC Packaging and System Performance |
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| Jan 01 2007 | |
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AlN Heater DesignBased on the results of the theoretical analysis for heater performance and design, Watlow has developed a manufacturing process and proprietary composition to realize an AlN heater that meets the aggressive requirements in semiconductor die bonding and IC testing applications. The basic structure of the high performance ceramic heater consists of the AlN matrix, the heating element with distributed wattage based on FEA to ensure the temperature uniformity (shown in Fig 3A), as well as a high power input capability and terminal. The basic structural units were assembled in a green state and then sintered in a nitrogen furnace to allow densification to take place. The resultant AlN heater is a nearly full-density ceramic compact with little or no porosity, which combined with uniformed grains (Fig. 3 B), ensures high mechanical strength and thermal conductivity. The mechanical strength (ASTM type A configuration) of an AlN processed heater has a mean of 371 MPa and Weibull modulus of 11. Following careful consideration of the environment and defining of the boundary conditions, the heating element pattern is optimized using the FEA technique. Infrared images of the AlN heater reveal excellent temperature uniformity of ±2ºC at 400ºC steady state. In addition to uniform temperature distribution, the heater must provide a fast heat-up rate for the short die bonding cycle. Collected data indicates that an AlN heater takes about 10.5 s to reach 400ºC when powered at 250 W/in2 power input. When power input is increased to 1,000 W/in2, a linear temperature profile with a heating rate approaching 150ºC per second is achieved and takes less than three seconds to reach target temperature. Such a heating rate exceeds the typical 100ºC per second requirement for die bonding applications. Finally, a small overshoot of less than 5ºC at 400ºC can be achieved easily using a self-tuning PID controller even at 150ºC per second ramp rate. To validate the reliability of the heater, a series of heaters with dimensions of 55 × 10 × 1.5 mm with 25-mm no-heat terminal were produced and tested by cycling between 100ºC and 700ºC at power of 1,000 W/in2. A Weibull analysis indicates that the MTBF life expectancy of the AlN heater is approximately 460,000 cycles. As these experimental results show, a high-performance AlN ceramic heater offers significant advantages in terms of fast ramping and cooling as well as temperature uniformity, and is ideal for the most demanding die bonding and flipchip operations. This article was written by Dr. Hongy Lin, principal scientist in charge of ceramic heater research and development, at Watlow Electric Manufacturing, St. Louis, MO. For more information, contact Dr. Lin at hlin@watlow. com, or visit http://info.hotims.com/10960-400 Prev: Accelerated Testing — Raising the Bar on Electronics Integrity Next: Sensor Interface Design Demystified |
