Evolution of microstructure and mechanical properties of as-cast Al-50Si alloy due to heat treatment and P modifier content

Macro segregation formation mechanism of the primary silicon phase in directionally solidified Al–Si hypereutectic alloys under the impact of electric currents

Microstructure characterization and thermal properties of hypereutectic Si–Al alloy for electronic packaging applications

http://www.ysxbcn.com/down/2014/06_en/17-p1766.pdf

Microstructure evolution of spray-formed hypereutectic Al-Si alloys in semisolid reheating process

La demarche actuelle des industries aerospatiales est de diminuer le cout de lancement des engins spatiaux par une reduction de la masse des composants. Dans l’optique de cette demarche, de nouveaux materiaux sont elabores et permettent de satisfaire aux exigences de densification, de dissipation thermique et de reduction de masse des equipements electroniques embarques dans les satellites. Cette these est une contribution a l’etude de deux de ces materiaux, l’AlSi CE9F et une nuance d’alumine cofrittee a temperature, destines a realiser des boitiers hybrides de protections de composants electroniques, initialement concus en Kovar. Les objectifs sont d’affiner les connaissances sur proprietes mecaniques des deux materiaux et de mettre en place des regles de conceptions propres a leurs comportements mecaniques. En effet, l’AlSi CE9F et l’alumine ont un comportement a rupture fragile. La determination de leurs resistances a la rupture est alors realisee dans le cadre de la theorie de Weibull. Des series d’essais de flexion quatre points et trois points sont effectues. Elles permettent d’identifier les parametres de Weibull des deux materiaux a temperature ambiante et de mettre en evidence les effets de volume. L’etude experimentale est poursuivie sur l’AlSi CE9F afin de determiner l’influence de la temperature sur ses proprietes mecaniques a travers deux approches. La premiere s’interesse a une variation monotone de la temperature et la seconde a des cycles thermiques entre -50 et 125°C. Si la premiere etude ne montre qu’une faible evolution du module d’elasticite, la seconde demontre que les cycles thermiques contribuent a l’amelioration de la resistance a la rupture de l’AlSi CE9F. Cette augmentation de la contrainte a la rupture se traduit egalement par une evolution de sa microstructure. Dans un second temps, un modele de Weibull est numeriquement mis en place a partir des parametres identifies et du critere de la contrainte equivalente de Freudenthal. Ce critere est analyse et valide a travers l’etude de trois eprouvettes en AlSi CE9F a chargements complexes. Le modele valide est enfin utilise pour decrire le comportement mecanique de deux composants dans differentes configurations de sollicitation, realises respectivement en alumine HTCC et en AlSi CE9F. Une methodologie de dimensionnement est alors mise en place et permettra de disposer de nouvelles regles de conception equivalentes a celles existant sur les materiaux classiques.

Caractérisation et modélisation probabiliste de la rupture fragile de l’AlSi CE9F et d’une alumine cofrittée pour composants embarqués à applications spatiales

The high silicon content Si-Al alloy is a typical heat dissipation material that used in the electrical packaging field. A spray forming process is used to produce a 70%Si-Al alloy specimen as a heat dissipation material with a diameter of 76.2mm (3 inch) and a thickness of 6mm. Then the spray formed Si-Al alloy specimens are hot pressed at 570 C with different pressure ranged from 200MPa to 700MPa to increase their density. The physical properties of the experimental alloy specimen are measured. And the microstructures are observed by using optical microscopy and scanning electronic microscopy. The results show that Spray forming is suitable to produce a 70%Si-Al alloy. The size of primary Si phase in the spray formed 70%Si-Al alloy is refined only 20 30 mm. The relative density of 70%Si-Al alloy after spray forming is about 90%. With a following hot pressure of 700MPa, the relative density value can obtain 98%. The typical physical properties such as the thermal conductivity, coefficient of thermal expansion and electrical conductivity of spray formed 70%Si-Al alloy are acceptable as a heat dissipation material for many electronic packaging applications. [doi:10.2320/matertrans.MRP2007630]

http://www.jstage.jst.go.jp/article/matertrans/49/3/49_MRP2007630/_pdf

Production and Properties of a Spray Formed 70%Si-Al Alloy for Electronic Packaging Applications

The high silicon content Si-Al alloy is a typical heat dissipation material that used in the electrical packaging field. A spray forming process wais used to produce a 90%Si-Al alloy specimen as a heat dissipation material in the present study. Then the spray formed 90%Si-Al specimens weare hot pressed at 1000°C with different pressure ranged from 2MPa to 10MPa to increase their density. The physical properties of the experimental alloy specimen weare measured. And the microstructure wass are observed by using optical microscopy and scanning electronic microscopy. The results showed that the Spray forming wais suitable forto producinge a 90%Si-Al alloy. With hot pressure of 10MPa, the relative density value of 90%Si-Al reachedcan obtain 94%. The typical physical properties such as the thermal conductivity, coefficient of thermal expansion and electrical conductivity of 90%Si-Al alloy are acceptable as a heat dissipation material for many electronic packaging applications.

Jun Yang

Papers

Production and Properties of a Spray Formed 70%Si-Al Alloy for Electronic Packaging Applications

Production and Properties of a 90%Si-Al Alloy for Electronic Packaging Applications