Al-Si controlled expansion alloys possess the lower weight-adjustable coefficient of thermal expansion( CTE)-high thermal conductivity features.Aluminum Silicon alloys are lightweight, high thermal conductivity alloys that are increasingly being used for RF & microwave packages, electro-optical housing, power device base plates and other critical heat sinking applications. The manufacture of these packages requires the Al-Si body containing the electronics to be hermetic sealed using Aluminum 4047 lids. The heat sensitivity of the weld requires the use of a pulsed laser, however welding alloys with a silicon content over 27% becomes increasingly problematic due to cracking of the Al-Si alloy. This is due to the weakness of the Al-Si alloy under the solidification forces of the weld. The thermal performance advantage of the higher silicon content alloys has great potential for significantly improving power handling of the packages. Therefore, a welding process was developed using pulse shaping and a minimized average power approach that eliminated cracking in alloys with up to 40% silicon.
These controlled expansion alloys are offered in a range of weight proportions of silicon and aluminum from 70Si-30Al to 27Si-73Al, with CTE’s 7 to 17 ppm/°C respectively. The specific applications of these alloys in summarized below table. Aside from tailoring the CTE, the key advantages these alloys over materials such as kovar and Cu-W are reduced weight, high stiffness and ease of manufacture.
Commonly electronic packaging;Circuit boardstiffener;Heat sink/spreader for avionic/telecommunications.
Laser-mirror;Electro-optia housing;optical devices;
High-power electronic packaging;housing;radar packages
Power device and laser packages
RF & microwave packages;High-brightness(HB)LED;Electro-optical housing;High-power laser substrate.