Joining a metal body made by a powder-based additive manufacturing process
Patent Information
- Application Number
- EP2023719301
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-04-26
- Filing Date
- 2023-04-05
- Publication Date
- 2024-12-25
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing methods for joining powder-based additively manufactured metallic bodies to thermal interfaces, such as silver sintering and diffusion soldering, are not suitable for larger connecting surfaces and require contact pressure, limiting their use in high-power density applications where efficient heat dissipation is critical.
A method involving a metallic body with metal particles on its joining surface, where a solder material is applied to form intermetallic phases with the particles, allowing for a high-temperature stable connection without the need for significant contact pressure, thus enhancing thermal conductivity and reducing manufacturing complexity.
This method enables improved thermal conductivity and temperature resistance in heat sink connections, allowing for higher performance and smaller packing densities in power electronic assemblies without the need for extensive cleaning or mechanical removal of residual powders, and can be applied to complex geometries produced by additive manufacturing processes.
Smart Images
Figure 1.1
Abstract
Description
[0001] Description
[0002] Joining a powder-based additively manufactured metallic body
[0003] The invention relates to a method for joining a powder-based additively manufactured metallic body to a thermal interface of an object. The invention further relates to a power electronic assembly and a semi-finished product.
[0004] Such a process is used, for example, in the manufacture of power electronic assemblies with high power density. These power electronic assemblies can be used in applications with high power densities, such as converters, rectifiers, inverters, and other power electronic components.
[0005] When electronic components such as power electronic semiconductor components are used, heat is generated which is usually dissipated via a heat sink. For this purpose, heat sinks are used, e.g. made of Cu, to which entire modules or individual components are adhered, e.g. using conductive adhesive. Due to its low thermal conductivity, the conductive adhesive, however, limits the heat dissipation from the layers above. In order to enable higher performance and lower packing densities, a temperature-resistant, highly thermally conductive connecting layer between the heat sink and the component or module is necessary. New assembly and connecting technologies such as silver sintering or diffusion soldering fundamentally enable the production of a highly temperature-resistant and highly thermally conductive connecting layer.
[0006] However, these processes are not yet suitable for use with larger connecting surfaces, particularly heat sink connections. Silver sintering processes often require contact pressure during production, so pressure-sensitive components or large surfaces cannot be manufactured. The object of the invention is to provide a process that enables high-temperature-stable connection of objects with reduced contact pressure.
[0007] This object is achieved by a method having the features specified in claim 1.
[0008] The following steps are proposed for joining a metallic heat sink manufactured using a powder-based additive manufacturing process to a thermal interface of an object:
[0009] - Providing the body which has metal particles at least on one joining surface and a solder material such that the metal particles are arranged between the solder material and the joining surface, and
[0010] - Soldering the joining surface of the body to the thermal interface so that at least some intermetallic phases are formed from the solder material and the metal particles.
[0011] Objects manufactured using powder-based additive manufacturing processes, in particular heat sinks, can have complex and correspondingly efficient geometries with regard to heat transfer and heat dissipation. Examples of possible manufacturing processes include selective laser sintering, selective laser melting, or electron beam melting. The process according to the invention enables such objects to be connected more effectively to a thermal interface. The metal particles can be from the powder used in the manufacturing process and can still be present on the joining surface from the manufacturing process. A cleaning process for the joining surface can thus be skipped or carried out in a less intensive manner.The metal particles allow the solder layer formed from the solder material and the metal particles to interpenetrate with intermetallic phases, thus achieving a particularly good thermal bond. Soldering of the joining surface can be performed with or without pressure, thus protecting the object, the thermal interface, and the body, and allowing the processing of sensitive bodies and objects.
[0012] In a further embodiment, the metal particles consist of the material used to manufacture the body. This can be metal powder, in particular a copper powder, which preferably comes from the same batch as the powder used to manufacture the body.
[0013] In another embodiment, the metal particles originate from the body's manufacturing process. If the metal particles are taken directly from the body's manufacturing process and / or are already adhered to the body and / or the joining surface, the material does not need to be stored separately and has experienced a similar temperature profile to the body itself.
[0014] In a particularly advantageous embodiment, the metal particles originate at least partially, in particular exclusively, from a powder bed during the body's manufacturing process. This can be the case, for example, if the body is removed from the powder bed and some metal particles are still adhering to it.
[0015] In a further embodiment, the soldering is designed such that intermetallic phases form between the metal particles, the solder and the joining surface. The formation of the intermetallic phases depends essentially on the conditions during the soldering process. For example, the soldering process can be designed in such a way that growth of the intermetallic phases is promoted. This can be ensured, for example, by an appropriate temperature and / or pressure profile. In a further embodiment, a cleaning process and / or post-surface treatment of the joining surface is skipped when the body is prepared. This can advantageously lead to sufficient metal particles from the manufacturing process of the body remaining on the joining surface, which can then form diffusion zones with the solder.In addition, the complex procedures and follow-up treatments can be simplified and the body can be used directly.
[0016] In a further embodiment, at least the joining surface of the body is provided as it is produced in the manufacturing process. Surfaces produced in additive powder-based processes have a certain surface roughness with certain, partially regular, unevennesses. These unevennesses can lead to a further improvement in heat transfer through the formation of diffusion zones. In particular, in conjunction with the metal particles, this enables hollow penetration with diffusion zones. In other words, the joining surface is provided unchanged from the manufacturing process.
[0017] In a further embodiment, the body is a heat sink, which, for example, has cooling fins and / or other cooling structures through which fluids can flow. Furthermore, the body and the metal particles can advantageously be made of copper or copper alloys.
[0018] In a further embodiment, the solder material is provided on the joining surface. This can be done in particular in such a way that the solder material fixes the material particles on the joining surface. This can be pre-formed solder deposits that are applied to the joining surface. Alternatively or additionally, it can be solder material that is pre-soldered at lower temperatures and in a shorter period of time than the actual joining process and already partially forms a solder connection with the joining surface without losing its solderability. The advantage here is that the particles are fixed, are no longer removed from the body during transport and a certain corrosion resistance is achieved.
[0019] The object is further achieved by a power electronics assembly which has at least one substrate with a metallization and a thermal interface. Furthermore, the assembly has at least one power electronics semiconductor component and a metallic body manufactured by means of a powder-based additive manufacturing process. The body has a joining surface which is soldered to the thermal interface in a heat-conducting manner such that a solder material which is arranged between the thermal interface and the joining surface and metal particles which are also arranged there form intermetallic phases. This has the advantage that the intermetallic phases considerably improve the thermal connection of the body, which is preferably designed as a heat sink, to the thermal interface, i.e. to the heat-generating assembly.
[0020] In an alternative or additional embodiment, the assembly comprises a substrate with a metallization, one or more power electronic semiconductor components, and a metallic body manufactured by means of a powder-based additive manufacturing process. The body is soldered to at least one of the power electronic semiconductor components in a heat-conducting manner with the joining surface in such a way that a solder material and the metal particles form intermetallic phases. The semiconductor components can also comprise metallizations which can also form intermetallic phases together with the solder material and the metal particles. The bodies are preferably designed as heat sinks. Furthermore, the bodies are preferably made of copper. Appropriate powder-based copper alloys can be used.Additionally or alternatively, the body can be soldered to at least one of the power electronic semiconductor components in a heat-conducting manner with the joining surface in such a way that the solder material and the metal particles form intermetallic phases. By applying appropriate joining conditions during soldering, the intermetallic phases can completely penetrate the solder and reach a thermal interface between the semiconductor components and the metallization.
[0021] In a further embodiment, the metal particles consist of the material used to manufacture the body. The embodiments of the method mentioned above are also applicable to the design of electronic assemblies.
[0022] The object is further achieved by a semi-finished product comprising a metallic body manufactured by means of a powder-based additive manufacturing process, which has metal particles originating from the additive manufacturing process on at least one joining surface. A solder material is also applied to the joining surface, so that the particles are enclosed between the solder material and the joining surface. This has the advantage that such a semi-finished product encloses and seals the particles, and enables easy transport and handling of the semi-finished products prepared in this way.
[0023] In other words, the process described at the beginning can be used to produce heat sinks that are produced by melting metal powders using additive manufacturing. In this case, Cu powder, for example, is melted, e.g. with the help of a laser, to form a solid bond. Without the use of a cleaning process, a residue of Cu powder will still be present on the surface of the heat sink produced in this way. If a solder material is then applied to this surface (with Cu powder residues), the solder material will mix with the Cu powder. During the soldering process, intermetallic phases that are characterized by particularly high thermal conductivity and temperature resistance form at the interface to the Cu. The particular advantage of the Cu particles from the AM process is that additional Cu is provided, at the interface of which intermetallic phases can form.This allows the bonding layer to grow through, forming the desired bonding layer between the heat sink and the module or component, or the respective thermal interface. This offers advantages through a significant improvement in thermal conductivity and the temperature resistance of the heat sink connection. Furthermore, costly steps such as cleaning or mechanical removal of residual metal powders on the surface of AM heat sinks can be eliminated.
[0024] The invention is described and explained in more detail below with reference to the exemplary embodiments shown in the figures. They show:
[0025] FIG 1 schematically shows an object and a
[0026] Body,
[0027] FIG 2 a cross-section of a solder joint,
[0028] FIG 3 shows an embodiment of a power electronic
[0029] assembly,
[0030] FIG 4 shows an alternative and / or additional embodiment of a power electronic assembly and
[0031] FIG 5 a combination of the embodiments of a power electronic assembly.
[0032] FIG 1 schematically shows an object 100 with a thermal interface 110, which is thermally connected via a solder material 60 to a metallic body 40 manufactured by means of a powder-based additive manufacturing process. The thermal connection of the body takes place via a joining surface 42 of the body, on which metal particles 50 are arranged, which in this case are already partially embedded in the solder material 60. Thus, during a soldering process, intermetallic phases are formed between the metal particles, the joining surface and the solder material. These phases considerably improve the heat transfer between the object 100 and the body 40. FIG 2 shows a micrograph of an actual solder connection of a body 40 that was manufactured by means of a powder-based additive manufacturing process. The metal particles 50 can be seen, which are already embedded in a solder material 60.Furthermore, unevennesses 45 resulting from the production of the body 40 are shown, which in turn also led to an improved connection between the solder, the metal particles and an object 100 that may then be attached to it. The area marked VOID is not filled in this case. An object 100 could be attached instead of the VOID area. Also visible are intermetallic phases 56, which are shown in one position only as an example. Such intermetallic phases 56 have also formed on other particles 50 in the solder material 60 and improve the thermal contact.
[0033] FIG 3 shows a power electronic assembly 200, which in this case has two power electronic semiconductor components 240, for example diodes or semiconductor switches. The power electronic semiconductor components 240 are applied to a metallization 230, which is structured so that electrical contacting of the semiconductor components 240 is possible. The metallization 230 is in turn applied to a substrate 220. The substrate 220, in addition to the metallization 230, also has a thermal interface 210. A body 40 designed as a heat sink, which has metal particles 50 on its joining surface 42, is attached to this thermal interface 210 via a solder material 60. The heat sink is shown schematically here as a simple heat sink 40 with fingers, but since it is an additive and powder-based manufactured body 40, the structures can be considerably more complex.Structures for the flow of fluids are also conceivable here.
[0034] FIG. 4 shows an alternative or supplementary embodiment of the power electronic assembly 200 from FIG. 3. Here, the heat sink 40 is thermally bonded to the power electronic semiconductor components 240 by means of a solder material 60 and the metal particles 50 contained therein. The substrate 220 and the metallization 230 are configured as shown in FIG. 3.
[0035] FIG. 5 shows an embodiment designed for particularly high thermal loads, for example, at high power densities. Here, heat sinks 40 are mounted on both sides using the method according to the invention, as shown in FIGS. 3 and 4.
[0036] In summary, the invention relates to a method for joining a metallic body (40) manufactured by means of a powder-based additive manufacturing process to a thermal interface (110) of an object (100), comprising the steps:
[0037] - providing the body (40) which has metal particles (50) at least on one joining surface (42), and a solder material (60) such that the metal particles (50) are arranged between the solder material and the joining surface (42),
[0038] - Soldering the joining surface (42) of the body (40) to the thermal interface (110) so that intermetallic phases (56) are formed at least partially from the solder material (60) and the metal particles (50). The invention further relates to a power electronic assembly and a semi-finished product.
[0039] Reference sign
[0040] 40 metallic body manufactured using a powder-based additive manufacturing process 42 joining surface of the body
[0041] 45 irregularities caused by the manufacturing process
[0042] 50 metal particles
[0043] 56 intermetallic phases
[0044] 60 solder material
[0045] 100 objects
[0046] 110 thermal interface of the object
[0047] 200 Power electronic module 210 Thermal interface of the module
[0048] 220 substrate
[0049] 230 structured metallization
[0050] 240 power electronic semiconductor components
Claims
Patent claims 1. Method for joining a metallic body (40) manufactured by a powder-based additive manufacturing process to a thermal interface (110) of an object (100), comprising the steps: - Providing the body (40) which has metal particles (50) at least on one joining surface (42), and a solder material (60) such that the metal particles (50) are arranged between the solder material and the joining surface (42), - Soldering the joining surface (42) of the body (40) to the thermal interface (110) so that at least partially intermetallic phases (56) are formed from the solder material (60) and the metal particles (50). - wherein the metal particles (50) consist of the material used to manufacture the body (40) and - the metal particles (50) originate from the manufacturing process of the body (40) and - the metal particles (50) originate at least partially from a powder bed of the manufacturing process of the body (40) 2. The method according to claim 1, wherein the metal particles (50) originate exclusively from a powder bed of the manufacturing process of the body (40).
3. Method according to one of the preceding claims, wherein the soldering is designed such that intermetallic phases (56) are formed between the metal particles, the solder and the joining surface (42).
4. Method according to one of the preceding claims, wherein when providing the body (40) a cleaning process and / or a surface post-treatment of the joining surface (42) is skipped.
5. Method according to one of the preceding claims, wherein when providing the body (40) at least the joining surface (42) is provided as it is by the manufacturing process cess is produced.
6. Method according to any of the preceding claims, wherein the body (40) is a heat sink.
7. Method according to any of the preceding claims, wherein the body (40) and the metal particles (50) consist of copper.
8. Method according to one of the preceding claims, wherein the solder material (60) is provided on the joining surface (42), in particular such that the solder material (60) fixes the metal particles (50) on the joining surface.
9. Power electronic assembly (200) , which at least - a substrate (220) with a metallization (230) and a thermal interface (210) , - at least one power electronic semiconductor device (240) and - has a metallic body (40) manufactured by means of a powder-based additive manufacturing process with a joining surface (42), wherein the body (40) is thermally soldered to the thermal interface (210) with the joining surface (42) such that a solder material (60) and the metal particles (50) form intermetallic phases (56).
10. Power electronic assembly (200) , which at least - a substrate (220) with a metallization (230) , - one or more power electronic semiconductor devices (240) and - a metallic body (40) manufactured by means of a powder-based additive manufacturing process with a joining surface (42), wherein the body (40) is thermally soldered to at least one of the power electronic semiconductor devices (240) such that a solder material (60) and the metal particles (50) form intermetallic phases (56) train.
11. Power electronic assembly (200) according to claim 9 or 10, wherein the metal particles (50) consist of the material used to manufacture the body (40).
12. Semi-finished product comprising a metallic body (40) manufactured by means of a powder-based additive manufacturing process, which has at least on a joining surface (42) metal particles (50) originating from the additive manufacturing process, wherein a solder material (60) is applied to the joining surface (42) such that the metal particles (50) are enclosed between the solder material (60) and the joining surface (42).