Graphite fiber composites for CTE control in thermal management [packaging]

A limiting problem in electronic packaging is thermally induced stresses in adjacent components with mismatched coefficients of thermal expansion (CTE). Composite technology can be utilized to minimize such problems. An important method for CTE control is the use of graphite fibers with negative CTE and high modulus to constrain high CTE materials. By controlling fiber volume fraction, precise CTE tailoring can be achieved in a single component such as a thermal plane, or in multiple components if they are hard bonded. An example is the use of a graphite fiber reinforced thermal plane to constrain an organic printed wiring board (PWB) to match the CTE of chips or chip carriers. Thermal performance enhancement of MCMs and other advanced module designs can be obtained through careful selection of the composite fiber and matrix, the consolidation method and appropriate joining technology. Evaluation of composite components must be based on property reproducibility, stress analysis, performance in thermal cycling and thermal flow through the module. This information is vital for performance/cost trade-offs which determine the extent of system integration.