Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Noninterengaged fiber-containing paper-free web or sheet...
Reexamination Certificate
2000-03-22
2002-09-17
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Noninterengaged fiber-containing paper-free web or sheet...
C428S298100, C428S364000, C428S435000, C174S212000, C257S798000
Reexamination Certificate
active
06451418
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a heat conductive resin substrate dissipating heat generated from electronic equipments and a semiconductor package excellent in heat radiation ability.
Recently, a countermeasure of heat generated from the electronic equipment due to advance in integration of the semiconductor package and advance in high integration and speed up of LSI or the like accompanying with advance in performance, miniaturization and weight reduction in the electronic equipment has became to be very important problems.
Conventionally, a method using a printed circuit board made of metal or ceramic with high heat conductivity, a method forming thermal via-holes for dissipating heat in a substrate, a method using metal, ceramic or resin with high heat conductivity as semiconductor-packaging material, or a method interposing grease with high thermal conductivity or a heat conductive rubber with flexibility between a heat-generating source and a radiator or between a heat source and a heat-conducting plate for purpose of reduction in contact thermal resistance or the like have been practiced in order for diffusion of heat by heat-generating element.
Although a known resin substrate, that is, the glass-cloth epoxy resin substrate or the like used in the printed circuit board on which electronic components such as the semiconductor package are equipped is relatively excellent in mechanical property, dimension accuracy, workability of a through-hole and multi-layering as compared with the metal substrate or the ceramic substrate, there is a disadvantage of inferiority in heat conductivity.
Therefore, it has been considered a method filling electrical insulation fillers such as metal oxides, metal nitrides, metal hydroxides and such as an aluminum oxide, a boron nitride, an aluminum nitride, a magnesium oxide, a zinc oxide, a silicon carbide, quartz and an aluminum hydroxide with high thermal conductivity into resin for a resin substrate which high heat conductivity is required.
However, thermal conductivity of the resin substrate into which such heat conductive fillers are filled is to the extent of 3 W/mK at most, therefore, advance in thermal conductivity has been desired earnestly.
According to Japanese Patent Laid-open No.HEI9-255871, a thermoplastic resin composition containing a polybenzasol fiber and the moldings is proposed.
This invention relates to the moldings such as a rigid resin composition, substrate material and case material with impact resistance, toughness, electrical insulation and heat conductivity. However, an upper limit of thermal conductivity of the substrate material obtained by this resin composition is approximately 1 W/mK, whereby heat conductive substrate material and the heat radiation semiconductor package of an object of the invention have not been obtained.
On the one hand, Japanese Patent Laid-open No.HEI11-17369 relates to heat radiation material consisting of a synthetic-resin wire rod with a certain diameter, which organic fibers are blended into a synthetic resin in the longitudinal direction. This heat radiation material is one which the synthetic-resin wire rods consisting of protrusion rods of 5 mm in diameter and 4 mm in length is blended, whereby the heat conductive substrate material and the semiconductor package excellent in heat radiation, of the object of the invention can not be obtained.
Moreover, for the electronic components constituted by a plurality of different materials such as semi-conductive silicon, an alloy of a copper and iron system, aluminum, a solder, a silicon oxide, a nitride, a resin substrate and an adhesive, a countermeasure for malfunctions by a generating thermal stress becomes important because of difference in the thermal expansion coefficients of respective constituting materials. That is, when the thermal expansion coefficient of the resin substrate becomes possible, thermal and electrical reliability is improved, thereby being able to contribute for the industry.
SUMMARY OF THE INVENTION
This invention provides a heat conductive substrate which is provided with electrical insulation and high heat conductivity, and is able to control a thermal expansion coefficient, a semiconductor package being excellent in heat radiation ability.
As a result of earnest studying for solving these problems, it has been found that the heat conductive resin substrate which the polybenzasol fibers are arranged in the thick direction and/or in the direction of a surface of the resin substrate, is provided with electrical insulation, and high heat conductivity and the thermal expansion coefficient can be controlled, and this invention is put into practice.
That is, this invention relates to a heat conductive resin substrate wherein the polybenzasol fibers are oriented in the thick direction and/or in the direction of a surface of the resin substrate, and further, a semiconductor package wherein semiconductor chips are mounted on the heat conductive resin substrate which the polybenzasol fibers are oriented in the thick direction and/or in the direction of a surface of the resin substrate.
The polybenzasol fiber used in the heat conductive resin substrate and the semiconductor package according to the invention is a fiber constituted of polybenzasol fiber polymer, and a polybenzasol (PBZ) means polybenzooxasol homopolymer (PBO), polybenzothiasol homopolymer (PBT) and random copolymer, sequential copolymer, block copolymer or graphed copolymer of those PBO and PBT, and is an organic polymer fiber excellent in strength, modulus of elasticity, heat resistance and electrical insulation.
Although a diameter, a shape of the cross section and a length of the polybenzasol fibers are not specified, the length of the fiber is preferable the same length as that of the resin substrate for heat transmission. The reason is that a length is same or the near to the same is the length, the larger becomes the thermal conductivity and a thermal expansion coefficient becomes lower. Moreover, for tensile strength of the polybenzasol fiber, it is preferable 4G Pa or more and an initial modulus of elasticity for tension is 140G Pa or more. The heat conductive resin substrate and the semiconductor package according to the invention can show more excellent heat conductivity by arranging in the resin substrate using the polybenzasol fiber which the tensile strength and the initial modulus of elasticity for tension are present within the range thereof.
The heat conductive resin substrate according to the invention comprises a structure that the polybenzasol fibers are oriented in the thick direction and/or in the direction of a surface of the resin substrate. The heat conductivity of the longitudinal direction of the fiber arranged is improved by orienting the polybenzasol fibers in the thick direction and/or in the direction of a surface of the substrate. Moreover, heat conductivity in the any direction which respective polybenzasol fibers are oriented has become possible to increase, as well as the thermal expansion coefficients has become possible to control, by orienting the polybenzasol fibers not only in one direction of the thick direction (hereinafter defined this as a Z direction) or the direction of a surface (hereinafter defined this as a X direction or a Y direction), but also a plurality of directions such as in two directions of the surface, in two directions of the thick direction and one direction within the surface (the Z direction and the X direction), in three directions of the thick direction and two directions within the surface (the Z direction and the X direction and the Y direction), and in three directions or more of the thick direction and two directions or more within the surface (the Z direction and the X direction, the Y direction and an another direction within X Y surface).
The concentration of the polybenzasol fiber allowing to contain in the heat conductive resin substrate is preferably 2 to 80 in volume percent. Improvement in heat conductivity becomes less, and the controlled range of the
Dixon Merrick
McGlew and Tuttle , P.C.
Polymatech Co. Ltd.
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