Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to heat or cool
Reexamination Certificate
1998-09-04
2001-02-13
Jones, Deborah (Department: 1775)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to heat or cool
C428S551000, C428S539500, C428S613000, C428S312600, C428S319100, C428S698000, C501S088000, C501S154000
Reexamination Certificate
active
06186768
ABSTRACT:
The invention refers to a metal matrix composite body (MMC body), including a porous reinforcement material having pores which are filled with an infiltration material selected from the group metal and metal alloy.
Metal matrix composites, also designated metal matrix composite materials or short MMC, are materials in which a nonmetallic reinforcement material and a metallic or semimetallic infiltration material are embedded within each other at different quantity ratios. The reinforcement material can be engulfed or infiltrated in the form of particles, fibers or porous bodies by metal or semimetal. Through selection of the type, shape, quantity and porosity of the reinforcement material as well as the type of the infiltration material, mechanical, electrical and thermal properties of finished materials can be accordingly varied to suit the demand.
A possible field of application of such MMC bodies is the electronic field or power electronics where they are utilized to dissipate lost heat generated by electronic components and thus are used to make heat sinks or circuit carriers.
For that, in particular the following three characteristics are required:
1.) High thermal conductivity—so that the lost heat generated by an electronic component can be dissipated as efficiently as possible.
2.) Low coefficient of thermal expansion, or coefficient of thermal expansion which substantially corresponds to the coefficient of thermal expansion of the component being cooled—so that the component and the attached heat sink change their dimensions in a substantially same manner when the temperature fluctuates so as to avoid tensions in the interface between component and heat sink.
3.) Low density—so that a smallest possible weight of the heat sink/circuit carrier can be realized.
A further possible field of application of MMC materials is their use for designing hot plates, with an insulator, for example of ceramic material, such as Al
2
O
3
, AlN, Si
3
N
4
, secured to the surface opposite the placement surface for a cooking pot. Attached to the surface of the insulator in opposition to the MMC plates is an electric heating resistance. Also for this field of application, the MMC plate should exhibit the above-stated three characteristics: the high thermal conductivity is required in order to efficiently transmit the heat generated by the heat conductor onto the cooking pot, the good match of the coefficients of thermal expansion between plate and insulator eliminates despite temperature fluctuations in the interface between MMC plate and insulator the formation of tensions which would result in a separation of both components from one another, and the low density realizes a low overall weight of the hot plate.
It is an object of the present invention to provide a MMC body of the above-stated type, which has all of the stated three characteristics to a high degree, but yet exhibits a particularly low coefficient of thermal expansion which especially matches the coefficient of thermal expansion of e.g. AlN and Si.
This object is attained in accordance with the invention by forming the reinforcement material from recrystallized silicon carbide (RSiC).
As a consequence of the structural configuration of this material, metal trapped in the pores can no longer deform the RSiC. The coefficient of thermal expansion of the entire MMC body is thus essentially defined solely by the coefficient of thermal expansion of the RSiC.
In accordance with a further development of the invention, it may be provided that the recrystallized silicon carbide has a porosity of 5 to 40% by volume, preferably 10 to 35% by volume, in particular 2 to 30% by volume.
By using these different porosities, the coefficient of thermal expansion can then be adjusted in a very precise manner.
Moreover, it may be provided to form the infiltration material from magnesium, zinc, iron, aluminum, copper or the like, as well as alloys of these metals. These materials can be additionally suited to the conditions and demands of the application.
In accordance with a further development of the invention, at least one structure may be secured to the MMC body. Thus, a formed body can be realized in a simple manner which exhibits areas of different mechanical, thermal and electrical properties. In this context, it may be provided to make the structure of electrically insulating material, in particular of a ceramic material such as e.g. Al
2
O
3
, AlN, or the like, or of diamond. The electronic component to be cooled can then be attached directly onto this insulating structure.
In accordance with a particularly preferred further development of the invention, the structure may be a diamond deposited from the gas phase, e.g. by a CVD process or PVD process, onto the MMC body. Diamond exhibits a particularly good thermal conductivity. Furthermore, as a result of the gas vapor deposition, a particularly intimate bond can be realized between the arising diamond structure and the MMC body. In both cases, heat applied—for example by an electronic component—onto the MMC body distant surface of the diamond structure can be transferred in a particular efficient manner to the MMC body.
Moreover, the body may be made of the infiltration material and formed in one piece with the MMC body. The MMC body and the attached component are then also in intimate connection which effects an especially good transfer of heat.
According to another further development of the invention, the structure may include a porous reinforcement material such as e.g. RSiC, SiC, ceramic, graphite or the like, having pores which are permeated by infiltration metal, and the structure may be formed in one piece with the MMC body.
Also in this case, the intimate bond between MMC structure and body is of advantage; moreover, the physical characteristics of the structure can be adjusted to suit those of the MMC structure through respective selection of its reinforcement material.
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Electrovac, Fabrikation elektrotechnischer Spezialartikel Gesell
Feiereisen Henry M.
Jones Deborah
Savage Jason
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