Improvement of Metal Diamond Composite (MDC) material manufacturing capability to reduce production costs.

 

 

The ESA-EC FP7 coordinated project AGAPAC (Advanced GaN Packaging) was completed in 2012 and has been highly successful. The aim of AGAPAC was to demonstrate advanced packaging concepts using MDC with improved thermal dissipation capability that can allow the full performance advantages of GaN technology to be realized. In addition, a consecutive TRP activity, ?High dissipative material for LF/RF hermetic hybrids?, was run and meant to assess different materials (e.g. AlSi, CMC, CuD) developed for realizing high dissipative packages. The contract has confirmed that MDC material offers the best perspective in terms of thermal conductivity. The MDC based package shows up to 5 fold improvement in thermal conductivity compared to more traditional materials (e.g. CuW, CuMo) and has allowed a 50% reduction in transistor channel temperature to be achieved, giving better electrical performance and improved reliability. These results show that a major improvement in the thermal capability of microwave and power transistor packages can be realized with the MDC approach.

 

Further work is now required to improve the manufacturing capabilities of the MDC material and to consolidate the European supply chain. To-date the material has been fabricated using an experimental manufacturing line. However, for this material to be able to be considered for commercial manufacture a pilot production line needs to be established in order to benefit from economies of scale and reduce manufacturing costs. In the AGAPAC project both hot pressing and liquid based infiltration manufacturing techniques were investigated. The infiltration approach was found to give the most stable material performance.

 

In Phase 1 (450 kEuro, 16 months duration) of this activity MDC material development and optimization shall be addressed based on the AGAPAC results. This includes the manufacturing of diamond based composites by liquid phase infiltration process, development of suitable shaping and finishing process (e.g. laser cutting), thermal analysis in terms of thermal conductivity and thermal expansion coefficient (before and after thermal cycles). So that coefficient of thermal expansion are matched to Kovar material without compromising the thermal conductivity required to be higher than 500 W/m?C.

 

Finally, the outcome of this Phase 1 will be to deliver MDC heat sink base plates compatible with hybrid package technology. A demonstrator of HPA package using MDC material as base plate shall be available at the end of this study. It will also arget price reduction of such MDC material by actively using low cost powder technologies that can be easily scaled to large dimensions.

 

The price-performance benefit will allow many new application markets to be considered and provide a disruptive route for implementing GaN (and other high power dissipation devices) technology on space based platforms. Phase 1 is expected to increase the TRL level from the current TRL 3 to TRL 4.

 

In Phase 2 (1000 kEuro, 12 months duration) of the project, a range of space product applications shall be identified and bespoke packages manufactured using a commercial supplier and subjected to a preliminary ESCC evaluation (e.g. in terms of material robustness, hermeticity, reliability, outgassing etc). The packages shall then be used to demonstrate an application for realization of a high power SSPA prototype/flight demonstrator design, manufactured and tested in accord with ECSS standards. Completion of Phase 2 shall allow to reach a technology TRL level of 6.