Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With provision for cooling the housing or its contents
Reexamination Certificate
2003-10-11
2004-12-14
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With provision for cooling the housing or its contents
C257S706000
Reexamination Certificate
active
06831359
ABSTRACT:
This application claims foreign priority from DE 102 48 644.1, filed Oct. 13, 2002, the contents of which are incorporated herein by reference.
SELECTED FIGURE FOR PUBLICATION
FIG. 1
is selected for publication on the face of the face of the patent.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power semiconductor module having improved configuration technology. More specifically, the present invention relates to a power semiconductor module with a base plate and/or being configured for direct or indirect installation on a heat sink or other cooling body, with active and/or passive components and improved configuration and electro-conductive features.
2. Description of the Related Art
Power semiconductor modules, in particular those including a power converter module, are known to have a base plate or for direct installation on a heat sink, with active and/or passive components. Several such power semiconductor modules are known from the literature. When the capacity is increased, especially by using modern power semiconductor components with higher cooling requirements, the conventional art cannot meet these requirements. Consequently, the present invention provides other methods of configuration technology that are absolutely necessary for the individual parts.
Modern power semiconductor modules, which are the starting point of this invention, are modules without base plates, such as described in DE 199 03 875 C2, the contents of which are herein incorporated by reference, consisting of:
a packaging,
a ceramic substrate with circuit-friendly metallic laminations such as those made according to the DCB (direct copper bonding) method;
components positively bonded to this substrate by soldering, such as diodes, transistors, resistors or sensors;
bonds to connect the structured side of the components with other components, the substrate and/or connecting elements leading outside;
a sealing compound preferably made of silicon rubber, to insulate the individual components from each other.
A configuration technology with pressure contact for the thermal contacting of the module on a heat sink has proven very advantageous for such power semiconductor modules. Unfortunately, this pressure contact configuration technology has been shown in particular, that the quality of large-surface soldering bonds is very difficult to control, which is greatly detrimental to the reliability and service life (premature failure) of the power semiconductor modules. This type of pressure contact bond has uniformity, homogeneity, and substantial quality control problems that increase greatly with the areas being pressure-contact-bonded.
Preferably, the pressure configuration in such pressure-contacted power semiconductor modules is achieved with a mechanically stable pressure plate. Depending on the further development, the generated pressure can be transmitted to the substrate either by means of special pressure plate designs (as shown, for example, in DE 196 48 562 C2) or by means of an elastic pressure accumulator according to DE 199 03 875 C2, the contents of both references are herein incorporated by reference as background material.
In such pressure-contacted power semiconductor modules, a heat-conducting medium is provided in an effort to establish full-surface thermal conduct and thus to compensate for any unevenness or non-uniformity on the heat sink and/or the substrate underside between the power semiconductor module and the heat sink. The non-uniformity of surface between the two opposing surfaces for pressure contacting can magnify the difficulties where any defects are complementary and additive.
In the power semiconductor modules according to DE 196 48 562 C2 or DE 199 03 875 C2, as well as power semiconductor modules known in prior art, with a base plate or for direct installation on a heat sink, each has the distinct disadvantage that heat dissipation to a cooling element, such as a heat sink, is subject to high thermal resistance, or thermal resistivity (the inverse of thermal conductivity). The more marginal areas exist between the power semiconductor module generating the heat and the heat sink, the greater the thermal transfer resistance. In comparison with metals, flexible thermally conducting layers such as heat-conductive paste, have clearly higher heat resistance. Therefore, the efficient dissipation of heat from a power semiconductor module to a heat sink is a substantial component of highly efficient compact configuration topologies.
Another disadvantage of conventional power semiconductor modules with a base plate or designed for direct installation on a heat sink is that modern power semiconductor components, as commonly used, have a higher current load capacity per relative chip area and consequently produce much more waste heat per unit of area. Unfortunately, the thermal connection between an advantageously metal-laminated substrate and the power semiconductor component is already a limiting factor for the efficiency of a power semiconductor module. At present, the heat generated in the power semiconductor component can still be dissipated by means of existing connection methods, usually soldering bonds.
In considering future chip generations, the thermal conductivity of the connection between the power semiconductor component and the substrate, will have an even more limiting effect on efficiency. Furthermore, the connections named above are presently at the limit of their current load capacity. In that respect, too, the electrical connection between the power semiconductor component and the substrate will determine the efficiency of the power semiconductor module
In summary, the problems with commercially available power semiconductor modules include at least the following:
1. Incapable thermal conductivity between semiconductor components and a substrate and/or a substrate and a heat sink or cooling body or means for cooling.
2. Non-uniform pressure contacting and non-uniform bonding resulting in the potential for hot-spots and weak-spots where the pressure contact bonding is insecure or non-uniform.
3. The electrical load capacity of present designs is limited by the pressure contact bonding between components.
4. Difficulty in uniformly forming a pressure contact bond between a metal-laminated surface of a substrate with either a power semiconductor component and/or a heat sink, cooling body, or other means for cooling and further transmitting any received thermal energy.
OBJECTS AND SUMMARY OF THE INVENTION
Another object of the present invention is to provide a power semiconductor module that overcomes the disadvantages noted above.
It is another object of the present invention is to provide a power semiconductor module with improved cooling ability while retaining module strength and electro-conductive characteristics.
It is another object of the present invention to provide an improved uniformity of a thermal bond between a substrate and a power semiconductor component.
It is another object of the present invention is to present a power semiconductor module in which the electrically and thermally conductive connection between at least one power semiconductor component and a substrate and/or the thermally conductive connection with a heat sink or cooling body or other means for cooling the power semiconductor module that has a reduced thermal and optionally also electrical resistance.
It is a further object of the present invention to present a power semiconductor module easily adapted in multiple embodiments beyond those shown herein as along as the invention, as described herein, is embodied.
It is another object of the present invention to create a thermally conductive paste including carbon based tubules resulting in a thermally conductive paste with better thermal conductivity than the prior art by at least about two orders of magnitude.
The present invention relates to a power semiconductor module, in particular a power converter module, with a base plate or for direct installation on a heat sink, cooling body, or
Ho Tu-Tu
Nelms David
Semikron Elektronik GmbH
Young, P.C. Andrew F.
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