Directly Cooled Substrates for Semiconductor Modules
A semiconductor module includes a substrate having a metallized first side and a metallized second side opposing the metallized first side. A semiconductor die is attached to the metallized first side of the substrate. A plurality of cooling structures are welded to the metallized second side of the substrate. Each of the cooling structures includes a plurality of distinct weld beads disposed in a stacked arrangement extending away from the substrate. The substrate can be electrically conductive or insulating. Corresponding methods of manufacturing such semiconductor modules and substrates with such welded cooling structures are also provided.
The instant application relates to semiconductor modules, and more particularly to directly cooled substrates for semiconductor modules and methods of manufacturing such substrates and modules.
BACKGROUNDHeat dissipation is an important consideration in the design of power electronics and must be controlled carefully. To protect semiconductor devices against overheating, the cooling system of a power module should be very efficient. The cooling approach is typically based on the type of power module. For example, power modules can be cooled directly or indirectly. Furthermore, modules may or may not have a base plate where the base plate can be flat or structured. Conventional power module base plates are normally made of copper because of the excellent heat conductivity. Other materials like AISiC, aluminum or clad materials are suitable substitutes with the advantage of a lower cost. Power modules without a base plate are less expensive, but with reduced thermal performance as compared to modules that use a base plate.
Power modules with and without a base plate can be cooled indirectly by an air or fluid based cooler. Typically the heat generated in the semiconductor dies (chips) flows through a ceramic substrate with metallized sides such as a DCB (direct-copper-bonded), the different solder layers (chip-soldering, system soldering, etc.) and the base plate. The thermal contact for heat conduction is realized by a thermal grease between the base plate (or DCB in the case of no base plate) and the cooler. Cooling semiconductor dies in this way is less than optimal as the thermal grease has a low heat conductivity of about 1 W/mK.
Directly cooled power modules with structured base plates provide more efficient cooling of power devices. Such base plates have pin or fin cooling structures on the bottom side of the base plate in direct contact with a cooling liquid (e.g. water, or a water glycol mixture) so that high heat transfer coefficients are achieved. Different technologies for structured base plate production are available such as metal-injection-molding process (MIM) or forging technology, which tend to have high production and material costs.
SUMMARYAccording to an embodiment of a semiconductor module support member, the support member comprises a substrate having a metallized side and a plurality of cooling structures welded to the metallized side of the substrate. Each of the cooling structures comprises a plurality of distinct weld beads disposed in a stacked arrangement extending away from the substrate.
According to an embodiment of a semiconductor module, the semiconductor module comprises a substrate having a metallized first side and a metallized second side opposing the metallized first side. A semiconductor die is attached to the metallized first side of the substrate. A plurality of cooling structures are welded to the metallized second side of the substrate. Each of the cooling structures comprises a plurality of distinct weld beads disposed in a stacked arrangement extending away from the substrate.
According to an embodiment of forming cooling structures for a semiconductor module, the method comprises: providing a substrate having a metallized side; and welding a plurality of cooling structures to the metallized side of the substrate, each of the cooling structures comprising a plurality of distinct weld beads disposed in a stacked arrangement extending away from the substrate.
According to an embodiment of a method of manufacturing a semiconductor module, the method comprises: providing a substrate having a metallized first side and a metallized second side opposing the metallized first side; attaching a semiconductor die to the metallized first side of the substrate; and welding a plurality of cooling structures to the metallized second side of the substrate, each of the cooling structures comprising a plurality of distinct weld beads disposed in a stacked arrangement extending away from the substrate.
Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.
The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts. In the drawings:
According to embodiments described herein, cooling structures are added to the metallized side of a support member for semiconductor modules by a multi-stage welding process. The cooling structures are built up in a step-by-step manner via an arc welding or other type of welding process applied several times on a substrate. In a first stage of the welding process, a weld bead is formed on a metallized side of the substrate. In each successive stage, an additional weld bead is added to form a stacked arrangement of distinct weld beads which extends away from the substrate. Each stacked arrangement of weld beads forms a cooling structure. The resulting support member with directly welded cooling structures provides a cost-effective solution for use in semiconductor modules to more efficiently transfer heat away from semiconductor dies included in the modules.
The substrate 102 shown in
In a second stage of the welding process, a third distinct weld bead 114 is formed on each of the second weld beads 112 after the second weld beads 112 solidify. Additional successive welding stage(s) can be carried out to form one or more additional distinct weld beads 116, 118 on each stack of preexisting weld beads after the previously formed weld beads solidify. In general, the weld beads 110, 112, 114, 116, 118 in each stacked arrangement are formed in successive stages by arc welding or other suitable welding process with a solidification period between each welding stage that allows the weld beads formed in the preceding stage to solidify before the weld beads in the next stage are formed. The right-hand side of
In each case, the most recently formed weld bead is permitted to solidify before the next weld bead in the stack is formed so that the cooling structures 100 are formed of stacked arrangements of distinct weld beads 110, 112, 114, 116, 118. In an arc welding embodiment, a weld interface or joint is present between adjacent ones of the weld beads 110, 112, 114, 116, 118 in the same stacked arrangement as indicated by the dashed lines shown in the cooling structure 100 illustrated in the right-hand side of
Module cooling can be further enhanced by providing the cooling structures 100 welded to the exposed metallized side 404, 414 of one or both substrates 400, 410 as shown in
The cooling structure welding processes described herein can be carried out within or after the process-chain for the power module. Therefore is not necessary to integrate an additional process step for cooling structures within the module process chain. The cooling structures offer a high heat transfer coefficient and a low thermal resistance comparable with directly cooled base plate systems. If aluminum is used for the cooling structures as well as for the substrate metallization, corrosion can be prevented. Power modules based on the substrates described herein with cooling structures eliminate a base plate and corresponding system soldering. Thus, production and material costs are reduced. In addition, a significant weight reduction is realized by eliminating the base plate.
Different concepts of power modules with directly cooled substrates as described herein are contemplated. For example, semiconductor modules for half-bridge, full-bridge or a 3-phase application can be realized with the cooling structures described herein. For power module production, power devices such as diodes, IGBTs (insulated gate bipolar transistors), JFETs (junction filed effect transistors) and/or power MOSFETs (metal oxide semiconductor field effect transistors) can be soldered or sintered to the top side of a ceramic substrate structured by etching in a defined way. For the electrical connections, bond wires and terminals can be provided for the control port and load current connections. After the die soldering and bonding steps, a plastic housing can be bolted or glued together with the substrate e.g. as shown in
Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper” and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc. and are also not intended to be limiting. Like terms refer to like elements throughout the description.
As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open-ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.
With the above range of variations and applications in mind, it should be understood that the present invention is not limited by the foregoing description, nor is it limited by the accompanying drawings. Instead, the present invention is limited only by the following claims and their legal equivalents.
Claims
1. A semiconductor module support member, comprising:
- a substrate having a metallized side; and
- a plurality of cooling structures welded to the metallized side of the substrate, each of the cooling structures comprising a plurality of distinct weld beads disposed in a stacked arrangement extending away from the substrate.
2. The semiconductor module support member of claim 1, wherein at least some of the weld beads have a curved exterior surface.
3. The semiconductor module support member of claim 1, wherein one or more weld beads of at least some of the cooling structures are non-uniformly shaped with respect to the other weld beads in the same cooling structure.
4. The semiconductor module support member of claim 1, wherein the weld bead of each cooling structure disposed furthest from the substrate has a proximal end welded to the weld bead next furthest from the substrate and a rounded distal end.
5. The semiconductor module support member of claim 1, wherein the substrate comprises an isolation material having a first metallized side and a second metallized side opposing the first metallized side, and wherein the cooling structures are welded to one of the metallized sides of the isolation material.
6. The semiconductor module support member of claim 1, wherein the metallized side of the substrate and the weld beads comprise aluminum.
7. The semiconductor module support member of claim 1, wherein at least some of the stacked arrangements of weld beads are columnar.
8. The semiconductor module support member of claim 7, wherein at least some of the columnar stacked arrangements of weld beads have different diameters and lengths.
9. The semiconductor module support member of claim 1, wherein a first end of each stacked arrangement is attached to the metallized side and a second end of each stacked arrangement is free standing.
10. A semiconductor module, comprising:
- a substrate having a metallized first side and a metallized second side opposing the metallized first side;
- a semiconductor die attached to the metallized first side of the substrate; and
- a plurality of cooling structures welded to the metallized second side of the substrate, each of the cooling structures comprising a plurality of distinct weld beads disposed in a stacked arrangement extending away from the substrate.
11. The semiconductor module of claim 10, further comprising a cooler attached to a periphery of the metallized second side of the substrate, the periphery being free of the cooling structures, wherein the cooling structures extend away from the substrate into a recessed region of the cooler.
12. The semiconductor module of claim 11, further comprising a mold compound encapsulating the semiconductor die at the metallized first side of the substrate.
13. The semiconductor module of claim 10, further comprising:
- a mold compound encapsulating the semiconductor die and the substrate;
- an additional substrate embedded in the mold compound above the metallized first side of the substrate and spaced apart from the semiconductor die by part of the mold compound, the additional substrate having a first side facing the semiconductor die and an opposing second side; and
- a plurality of cooling structures welded to the second side of the additional substrate, each of the cooling structures comprising a plurality of distinct weld beads disposed in a stacked arrangement extending away from the additional substrate,
- wherein the cooling structures welded to the second side of each substrate protrude out of the mold compound.
14. The semiconductor module of claim 10, wherein the metallized second side of the substrate and the weld beads comprise aluminum.
15. The semiconductor module of claim 10, wherein the metallized first side of the substrate comprises a different material than the metallized second side of the substrate, and wherein the weld beads comprise the same material as the metallized second side.
16. The semiconductor module of claim 10, wherein the plurality of cooling structures is electrically isolated from the semiconductor die by the substrate.
17. The semiconductor module of claim 10, wherein a first end of each stacked arrangement is attached to the metallized side and a second end of each stacked arrangement is free standing.
Type: Application
Filed: Jul 11, 2017
Publication Date: Oct 26, 2017
Inventors: Andre Uhlemann (Dortmund), Alexander Herbrandt (Warstein)
Application Number: 15/646,127