Both liquid-phase-sintered and presintered-and-infiltrated approaches are used to fabricate copper-tungsten and copper-molybdenum heat sinks. Comparing manufacturing routes reveals: Infiltrated composites have a TC advantage over liquid-phase-sintered composites at any target value of CTE, and a CTE advantage at any value of TC. Copper-tungsten has a TC advantage over copper-molybdenum at any target value of CTE, and a CTE advantage at any value of TC. At low copper contents, the small difference in properties between infiltrated and liquid-phase-sintered composites is acceptable for components that are candidates for near-net-shape forming. This drives significant R&D work to optimize powders and processes for liquid-phase-sintered materials. The requirement for continuing increases in TC without sacrificing thermal expansion compatibility with solid-state devices and packaging substrates, has generated interest in other copper-base composites with graphite and diamond. The problems to be solved in copper-carbon composites, and some of their promising solutions, include: Poor particle-matrix bond strength: matrix alloying, and fibers coated with reactive metals such as chromium or titanium, show promise in improving interfacial bonding. Detrimental effects of alloying on matrix TC, but composites of copper and chromiumcoated diamond have shown promise, exhibiting TC values as high as 600 W/m·K. Machinability and fabricability of diamond composites: these problems are being attacked with machining technologies that do not require mechanical interaction between tool and workpiece, e.g., laser and EDM machining, and the use of net-shape-forming technologies. A new copper PM technology shows promise in the manufacture of solid-state devices and TFT-FPD screens. It employs sputtering targets of copper-refractory metal alloy (molybdenum, tungsten, tantalum) that produce circuit lines free from copper suicide formation under standard processing and operating temperatures. Developers cite several advantages of the material, including: Improved process yields due to fewer processing steps Lower direct processing costs due to fewer processing steps Lower electrical resistance of sputtered films, allowing faster response times and enabling large displays Finer-pitch wiring than standard aluminumneodymium wiring Elimination of chromium in devices using it as a diffusion barrier, and Enhanced oxidation resistance compared with pure copper.
|Original language||English (US)|
|Number of pages||12|
|Journal||International Journal of Powder Metallurgy (Princeton, New Jersey)|
|State||Published - Sep 1 2007|
All Science Journal Classification (ASJC) codes
- Metals and Alloys
- Industrial and Manufacturing Engineering