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Centre Capabilities

Microwave Heating: From food to semiconductor packages

Centre staff are collaborating in developing and applying modelling techniques that predict microwave heating of materials. The industrial application to which these techniques are being applied is the cooking of food and the curing of polymer materials used to package semiconductors.

Microwave Heating Diagram

The vast majority of polymer materials used in circuit boards for electronic products such as computers, heart pacemakers, safety critical display consoles, and many others, are joined together and cured using infra-red radiation. This conventional process can take several hours to perform, slowing production throughput and contributing a significant portion to the cost of manufacture.

With the demand for lighter, faster, and smaller electronic devices, there is a need for innovative material processing techniques and control methodologies. One such technique is Variable Frequency Microwave (VFM) processing, which can perform the same functions as conventional thermal processing but much quicker, and in terms of minutes instead of hours. However, there are several limitations in VFM processing, including: uncertain process characterization methods, incomplete understanding of the interactions between the microwaves and materials, and a lack of control over the various processes occurring. This lack of capability and understanding has held back the uptake of microwave curing in electronic product assembly.

Multi-physics modelling that can predict microwave heating, polymer cure, and the resulting stresses imposed in the materials will greatly assist electronic product designers to adopt an optimised microwave heating technology.

Within the Centre, CSEG has pioneered the development of microwave heating techniques for food. The basic science of the electromagnetic fields, and the heat and mass transfer relevant to microwave cooking, are well understood. What had not been quantitatively analysed is the systematic coupling between these phenomena, which controls the whole process because of the sensitive dependence of the electromagnetic properties on the local temperature and, especially, the moisture content. Integrated modelling techniques have now been developed which predict the electromagnetic fields, temperature, and moisture transport within a food sample placed inside a microwave oven. These techniques have been used to greatly increase understanding of the impact of microwave frequencies, as used in ovens found in the home, on the heating of foods with different composition and moisture content.

CMRG, with the assistance of CSEG, is coupling the microwave heating prediction tools with its thermo-mechanical and reliability prediction methodology. Within software such as PHYSICA these coupled numerical techniques will enable highly complex calculations to be undertaken for the curing of polymer materials as found in electronic circuit boards. A new micro-engineered oven is being design by our industrial partners which, when placed over an electronic component, will heat and cure the polymer materials without damaging the semiconductors and circuitry. These simulations are also helping to establish design rules for electronic product designers that will allow them to effectively adopt these new technologies and ensure that the resulting products are reliable.