Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1996-09-04
1999-07-27
Krynski, William
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
428209, B32B 900
Patent
active
059287683
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a silicon nitride circuit board used in a semiconductor device or the like, and more particularly, to a silicon nitride circuit board whose heat radiation characteristics and mechanical strength are simultaneously improved and whose heat cycle resistance characteristics are improved.
In the present invention, a high-strength silicon nitride substrate having a thermal conductivity (heat conductivity) of 60 W/m K or more is used to improve a circuit board, thereby making it possible to form a thin circuit board. When the circuit board is decreased in thickness, a compact, high-accurate circuit board is obtained, and a decrease in source cost or material cost can be decreased. The maximum deflection and anti-breaking strength of the circuit board are considerably improved in comparison with a conventional circuit board. For this reason, the circuit board is not easily broken when the circuit board is incorporated or assembled in a semiconductor device or the like, and the production yield of the semiconductor device can be considerably improved. When the silicon nitride substrate having high strength, excellent heat radiation, and high thermal conductivity is applied, a high-heat-quantity type and wide-area type circuit board (for example MCM: multi-chip module) in which a plurality of semiconductor elements or chips can be mounted can also be manufactured.
BACKGROUND ART
A circuit board in which a metal circuit layer having electrical conductivity is integrally bonded to the surface of a ceramic substrate such as an alumina (A1.sub.2 O.sub.3) sintered body having excellent insulating characteristics with a soldering material, and a semiconductor element is mounted at a predetermined position of the metal circuit layer is popularly used.
A ceramic sintered body containing silicon nitride as a main component has excellent heat resistance in a high-temperature environment of 1000.degree. C. or more, and has excellent thermal-shock resistance. For this reason, as a structural material for high temperature which can be replaced with a conventional heat resistant super alloy, the ceramic sintered body is tried to be applied to various refractory heat-resistant parts such as gas turbine parts, engine parts, or mechanical parts for making steel. In addition, since the ceramic sintered body has high corrosion resistance to a metal, the ceramics sintered body is tried to be applied as a melt-resisting material for a molten metal. Since the ceramic sintered body has high abrasion resistance, the ceramic sintered body is tried to be actually applied to a slidable member such as a bearing or a cutting tool.
As the composition of a conventional silicon nitride ceramic sintered body, the following is known. That is, an oxide of a rare earth element or alkaline earth element such as yttrium oxide (Y.sub.2 O.sub.3), cerium oxide (CeO), or calcium oxide (CaO) is added as a sintering assistant to silicon nitride material powder. By using such a sintering assistant, sintering characteristics are improved, and high density and high strength can be obtained.
A conventional silicon nitride sintered body is manufactured as follows. That is, a silicon nitride source powder is added with the above sintering assistant to be molded. The molded member is sintered in a sintering furnace at a temperature of about 1,600.degree. C. to 2,000.degree. C. for a predetermined time, and then cooled in the furnace. The resultant sintered body is subjected to grinding and polishing processes.
However, in a silicon nitride sintered body manufactured by the above conventional method, although mechanical strength such as a toughness or tenacity value is excellent, thermal conductivity characteristics are considerably degraded in comparison with other sintered bodies such as an aluminum nitride (AlN) sintered body, a beryllium oxide (BeO) sintered body, and a silicon carbide (SiC) sintered body. For this reason, the silicon nitride sintered body is not actually used as a material for electronics such
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Ikeda Kazuo
Komatsu Michiyasu
Komorita Hiroshi
Mizunoya Nobuyuki
Sato Yoshitoshi
Kabushiki Kaisha Toshiba
Krynski William
Lam Cathy F.
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