Ceramic substrate unit for power module and method for manufacturing ceramic substrate unit for power module
The ceramic substrate unit with conductive spacers and Ag alloy filler layers addresses the issues of short circuits and thermal shock in power modules by providing stable bonding and efficient heat dissipation, enhancing reliability and efficiency in high-power applications.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- AMOGREENTECH CO LTD
- Filing Date
- 2025-10-31
- Publication Date
- 2026-06-04
AI Technical Summary
Conventional power modules using wire bonding for electrical connections in high-power and high-current environments are prone to short circuits or open circuits, and the manufacturing process is susceptible to thermal shock and bonding defects.
A ceramic substrate unit with conductive spacers and Ag alloy filler layers, where the second filler layer has a higher Ag content than the first, providing stable and robust bonding without wires, reducing thermal stress and preventing layer separation.
Eliminates electrical hazards and improves reliability and efficiency by ensuring stable bonding and heat dissipation in high-voltage and high-current environments, while protecting against thermal shock during manufacturing.
Smart Images
Figure KR2025017705_04062026_PF_FP_ABST
Abstract
Description
Ceramic substrate unit for power module and method for manufacturing a ceramic substrate unit for power module
[0001] The present invention relates to a ceramic substrate unit, and more particularly to a ceramic substrate unit for a power module suitable for a high-voltage power module requiring high mechanical strength, thermal conductivity, and heat dissipation performance, and a method for manufacturing the ceramic substrate unit.
[0002] Power semiconductor devices are fundamental components of electronic systems that perform rectification and switching functions. Various power semiconductor devices, such as diodes, transistors, and thyristors, play a critical role in power conversion and control and are used to process high-voltage and high-current signals. Power semiconductor devices are designed to minimize power consumption by efficiently converting or amplifying electrical signals.
[0003] Power modules utilizing these power semiconductor devices are essential for applications requiring high voltage and high current, such as hybrid and electric vehicles. Power modules consist of power semiconductor devices and the substrates that mount them, and thermal dissipation characteristics, durability, and reliability are critical factors for efficient power transfer. Ceramic AMB substrates are a representative material used as the substrate for these power modules.
[0004] Ceramic AMB substrates provide stable performance even in high-voltage and high-temperature environments due to the excellent insulation and thermal conductivity of ceramics. Ceramic AMB substrates feature a structure in which electrodes are formed on the upper and lower surfaces of the ceramic substrate. The electrodes are primarily made of copper, and this structure provides high mechanical strength, thermal conductivity, and strong electrical connections, enabling the maintenance of excellent performance even in high-temperature environments.
[0005] In conventional power modules, semiconductor devices are electrically connected to a substrate via wire bonding using gold (Au), copper (Cu), or aluminum (Al), and the substrate is also connected to a PCB via wire bonding. In other words, most existing power modules utilize wire bonding for the power transmission paths required for electrical signal and power conversion. However, this structure has the disadvantage of a high probability of short circuits or open circuits occurring in high-power and high-current environments.
[0006] The matters described in the background technology above are intended to aid in understanding the background of the invention and may include matters that are not disclosed prior art.
[0007] The technical problem that the present invention aims to solve is to provide a ceramic substrate unit for a power module that can eliminate electrical hazards in high-power and high-current environments by having a configuration (conductive spacer) that electrically connects semiconductor devices to a ceramic substrate without wires.
[0008] Another technical problem that the present invention aims to solve is to provide a method for manufacturing a ceramic substrate unit for a power module that protects the substrate from thermal shock during the manufacturing process, resolves bonding defects and the resulting layer separation problems, and enables stable and robust bonding between components.
[0009] According to one aspect of the present invention as a means of solving the problem, a ceramic substrate unit for a power module comprises a ceramic substrate having an upper metal layer and a lower metal layer formed on the upper and lower surfaces of the ceramic substrate, a first filler layer disposed between the ceramic substrate and the upper metal layer and between the ceramic substrate and the lower metal layer, a plurality of conductive spacers having one surface bonded to the upper metal layer of the ceramic substrate, and a second filler layer disposed between the upper metal layer and the conductive spacers, wherein the first filler layer and the second filler layer are composed of an Ag alloy containing Ag, and the alloy composition ratios of the first filler layer and the second filler layer are different.
[0010] In a ceramic substrate unit for a power module according to one aspect of the present invention, the upper metal layer and the lower metal layer may be formed from one of the following materials: Cu, Cu alloy, ETP (Electrolytic Tough Pitch), OFC (Oxygen-Free Copper), and Al.
[0011] In a ceramic substrate unit for a power module according to one aspect of the present invention, the conductive spacer may be formed from one of the following materials: Cu, Cu alloy, Mo, and CPC (Conductive Polymer Composite).
[0012] In a ceramic substrate unit for a power module according to one aspect of the present invention, the first filler layer and the second filler layer may be composed of an Ag-Cu alloy. Here, the second filler layer may be an Ag-Cu alloy having an Ag content higher than the Ag content of the first filler layer.
[0013] In a ceramic substrate unit for a power module according to one aspect of the present invention, the first filler layer may be an Ag-Cu alloy with a composition ratio of Ag to Cu of 5:5, and the second filler layer may be an Ag-Cu alloy with a composition ratio of Ag to Cu of 7:3.
[0014] As another preferred embodiment, the first filler layer may be an Ag-Cu alloy with a composition ratio of Ag to Cu of 4:6, and the second filler layer may be an Ag-Cu alloy with a composition ratio of Ag to Cu of 7:3.
[0015] According to another aspect of the present invention as a means of solving the problem, a method for manufacturing a ceramic substrate unit for a power module is provided, comprising the steps of bonding an upper metal layer and a lower metal layer to the upper and lower surfaces of a ceramic substrate via a first filler layer, and bonding a conductive spacer to the upper metal layer via a second filler layer, wherein the first filler layer and the second filler layer are composed of an Ag alloy containing Ag, and the alloy composition ratios of the first filler layer and the second filler layer are different from each other.
[0016] In a method for manufacturing a ceramic substrate unit for a power module according to another aspect of the present invention, the upper metal layer and the lower metal layer are formed from one of the following materials: Cu, Cu alloy, ETP (Electrolytic Tough Pitch), OFC (Oxygen-Free Copper), and Al, and the conductive spacer may be formed from one of the following materials: Cu, Cu alloy, Mo, and CPC (Conductive Polymer Composite).
[0017] In a method for manufacturing a ceramic substrate unit for a power module according to another aspect of the present invention, the first filler layer and the second filler layer may be an Ag-Cu alloy. Here, the second filler layer may be an Ag-Cu alloy having an Ag content higher than the Ag content of the first filler layer.
[0018] In a method for manufacturing a ceramic substrate unit for a power module according to another aspect of the present invention, the first filler layer may be an Ag-Cu alloy with a composition ratio of Ag to Cu of 5:5 to 4:6, and the second filler layer may be an Ag-Cu alloy with a composition ratio of Ag to Cu of 7:3.
[0019] The present invention eliminates potential hazards, such as electrical short circuits or open circuits in high-power and high-current environments, by providing a conductive spacer that mediates the electrical connection between a semiconductor device and a ceramic substrate instead of a wire. This improves the reliability and efficiency of the power module and offers the structural advantage of satisfying the heat dissipation characteristics and mechanical rigidity required by power modules that process high-voltage and high-current signals.
[0020] In addition, the present invention can lower the secondary bonding temperature during the substrate manufacturing process by using an Ag alloy with a higher Ag content than the primary bonding layer (first filler layer) as the secondary bonding layer (second filler layer) (because Ag alloys have the characteristic that the effective melting point decreases as the Ag content increases). As a result, thermal stress applied to the substrate during the bonding process is reduced, and the quality and stability of the bonding layer can be maintained.
[0021] In other words, by using an Ag alloy with a higher Ag content than the primary junction layer (first filler layer) as the secondary junction layer (second filler layer), the substrate can be safely protected from thermal shock, and problems such as bonding defects and subsequent layer separation can be resolved. In addition, since stable and robust bonding between components is achieved, a high-power module capable of stable and reliable power transfer even in high-voltage and high-current environments can be provided.
[0022] FIG. 1 is a partially exploded perspective view illustrating a ceramic substrate unit for a power module according to an embodiment of the present invention.
[0023] FIG. 2 is a cross-sectional view of a ceramic substrate unit for a power module according to an embodiment of the present invention.
[0024] FIG. 3 is a flowchart illustrating a method for manufacturing a ceramic substrate unit for a power module according to an embodiment of the present invention.
[0025] Hereinafter, preferred embodiments of the present invention will be described in detail.
[0026] In describing the embodiments of the present invention, identical or similar components are assigned the same reference numerals, and redundant descriptions thereof are omitted. Furthermore, detailed descriptions of related prior art are omitted if it is determined that such detailed descriptions could obscure the essence of the embodiments disclosed in this specification.
[0027] In addition, the attached drawings are intended only to facilitate understanding of the embodiments disclosed in this specification, and the technical concept disclosed in this specification is not limited by the attached drawings, and it should be noted that they include all modifications, equivalents, and substitutions that fall within the concept and technical scope of the present invention.
[0028] Additionally, terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but said components are not limited by said terms. These terms are used solely for the purpose of distinguishing one component from another.
[0029] Furthermore, when it is mentioned that a component is "connected" or "joined" to another component, it should be understood that while it may be directly connected or joined to that other component, there may also be other components in between.
[0030] On the other hand, when it is stated that one component is "directly connected" or "directly coupled" to another component, it should be understood that there are no other components in between.
[0031] Furthermore, terms such as "comprising," "having," and "having" used in describing embodiments of the present invention are intended to specify the existence of features, numbers, steps, actions, components, parts, or combinations thereof of the invention, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.
[0032] And the fact that one component is in the "front," "rear," "upper," or "lower" of another component includes, unless there are special circumstances, not only being placed in the "front," "rear," "upper," or "lower" of the other component in direct contact with it, but also having another component placed in between.
[0033] The drawings are intended solely to facilitate an understanding of the concept of the present invention and should not be interpreted as limiting the scope of the invention. Furthermore, it is noted that relative thicknesses, lengths, or sizes in the drawings may be exaggerated for convenience and clarity of explanation.
[0034] FIG. 1 is a partially exploded perspective view illustrating a ceramic substrate unit for a power module according to an embodiment of the present invention, and FIG. 2 is a combined cross-sectional view of a ceramic substrate unit for a power module according to an embodiment of the present invention.
[0035] Referring to FIGS. 1 and 2, a ceramic substrate unit (1) according to an embodiment of the present invention includes a ceramic substrate (10) and a plurality of conductive spacers (20). The ceramic substrate (10) may be one of an AMB (Active Metal Brazing) substrate, a DBC (Direct Bonded Copper) substrate, or a TPC (Thick Printing Copper) substrate. These ceramic substrates (10) are substrates in which a metal is directly bonded to a ceramic substrate (12).
[0036] The ceramic substrate (10) may be configured to include a ceramic substrate (12) and an upper metal layer (14) and a lower metal layer (16) formed on the upper and lower surfaces, respectively, of the ceramic substrate (12) so as to have high mechanical strength and thermal conductivity and to effectively dissipate heat generated from a semiconductor chip (not shown). Here, the thickness of the ceramic substrate (12) may be 0.32t, and the thickness of the upper metal layer (14) and the lower metal layer (16) may be 0.3t.
[0037] The ceramic substrate (12) may be made of an oxide-based or nitride-based ceramic material. For example, the ceramic substrate (12) may be composed of one of alumina (Al2O3), zirconia-reinforced alumina (ZTA), aluminum nitride (AlN), or silicon nitride (Si3N4). The upper metal layer (14) and the lower metal layer (16) may be formed by brazing a thin metal foil to the upper and lower surfaces of the ceramic substrate (12).
[0038] The upper metal layer (14) can be formed in the shape of a predetermined circuit pattern. For example, the upper metal layer (14) can be formed by brazing a thin metal foil in the shape of a flat plate onto the upper surface of a ceramic substrate (12), and then processing it into an electrode pattern suitable for mounting a semiconductor chip or driving element through an etching process. This upper metal layer (14) can be made of one of Cu, Cu alloy, ETP (Electrolytic Tough Pitch), or OFC (Oxygen-Free Copper).
[0039] The lower metal layer (16) can be formed in a flat plate shape that facilitates heat transfer on the lower surface of the ceramic substrate (12). The lower metal layer (16) can be formed by a process of brazing a thin metal foil in the shape of a flat plate onto the lower surface of the ceramic substrate (12). This lower metal layer (16) can be made of the same metal or metal alloy as the upper metal layer (14). For example, it can be made of one of Cu, Cu alloy, ETP, or OFC.
[0040] The conductive spacer (20) serves to electrically connect a semiconductor chip or a driving element to a ceramic substrate (10). The conductive spacer (20) also serves to adjust the height between the ceramic substrate (10) and the semiconductor chip or driving element. To this end, one side of the conductive spacer (20) is bonded to the upper metal layer (16) of the ceramic substrate (10), and the semiconductor chip or driving element can be mounted on the other side.
[0041] Each conductive spacer (20) may be formed in a block shape having an area corresponding to the electrode area of a semiconductor chip or driving element to be mounted thereon. After a plurality of semiconductor elements (200) are mounted corresponding to each of the plurality of conductive spacers (20), they may be sealed with a molding resin (not shown), such as epoxy, for protection from the external environment. The molding resin may be formed by melting under high temperature and high pressure, injecting it in a liquid form through a molding mold, and curing it.
[0042] The conductive spacer (20) may be made of a metal or metal alloy having excellent electrical and thermal conductivity. The conductive spacer (20) may be made of, for example, Cu, a Cu alloy, or Mo. The conductive spacer (20) may also be made of a conductive polymer composite material, such as CPC, which has flexibility, processability, and electrical and thermal conductivity.
[0043] A first filler layer (13) is disposed between the ceramic substrate (12) and the metal layers (14, 16). The first filler layer (13) is disposed between the ceramic substrate (12) and the upper metal layer (14) and between the ceramic substrate (12) and the lower metal layer (16), respectively, to facilitate strong thermal and mechanical bonding between them. The first filler layer (13) can be formed on the surface (upper and lower surfaces) of the ceramic substrate (12) by various methods such as paste application and sintering, sputtering deposition, foil attachment, and electroless plating.
[0044] In the embodiment, the first filler layer (13) may be composed of an Ag alloy containing Ag. The first filler layer (13) may preferably be composed of an Ag-Cu alloy. Since the Ag-Cu alloy has a high level of thermal conductivity, it can maximize heat dissipation performance in the power module when high heat is present. The Ag-Cu alloy can also maximize bonding strength while preserving the structural characteristics of the ceramic substrate (12) due to its properties.
[0045] In particular, Ag has strong oxidation resistance, maintaining a stable state at high temperatures, and can contribute to maintaining stable bonding quality by suppressing oxide formation during the bonding process. Ag also has excellent wettability with metals or ceramics at specific brazing temperatures (typically 600–900°C), allowing it to spread uniformly across the bonding surface to form a solid bonding layer.
[0046] A second filler layer (30) is disposed between the upper metal layer (14) of the ceramic substrate (10) and the conductive spacer (20). The second filler layer (30) mediates a strong thermal and mechanical bond between the upper metal layer (14) of the ceramic substrate (10) and the conductive spacer (20). The second filler layer (30) can be formed on the surface of the upper metal layer (14) to which the conductive spacer (20) is attached or on the surface of the conductive spacer (20) to which the upper metal layer is bonded by various methods such as paste application and sintering, sputtering deposition, foil attachment, and electroless plating.
[0047] The second filler layer (30) may be composed of an Ag alloy containing Ag. Preferably, the second filler layer (30) may be composed of an Ag-Cu alloy. Since the Ag-Cu alloy has a high level of thermal conductivity, it can maximize heat dissipation performance in the power module when high heat is present. The Ag-Cu alloy can also contribute to maximizing bonding strength while preserving the structural properties of the ceramic substrate (12) due to its characteristics.
[0048] In particular, Ag has strong oxidation resistance, maintaining a stable state at high temperatures, and can contribute to maintaining stable bonding quality by suppressing oxide formation during the bonding process. Ag also has excellent wettability with metals or ceramics at specific brazing temperatures (typically 600–900°C), allowing it to spread uniformly across the bonding surface to form a solid bonding layer.
[0049] As mentioned, the first filler layer (13) mediating the bonding between the ceramic substrate (12) and the metal layers (14, 16) and the second filler layer (30) mediating the bonding between the upper metal layer (14) and the conductive spacer (20) can both be composed of an Ag alloy. Preferably, the first filler layer (13) and the second filler layer (30) can both be composed of an Ag-Cu alloy. As a more specific embodiment, the first filler layer (13) and the second filler layer (30) can be formed of an Ag-Cu alloy with different compositional ratios (mixing ratios) of Ag and Cu.
[0050] In the embodiment, the second filler layer (30) may be formed of an Ag-Cu alloy having an Ag content higher than that of the first filler layer (13). As a preferred embodiment, the first filler layer (13) may be formed of an Ag-Cu alloy with an Ag-to-Cu composition ratio of 5:5, and the second filler layer (30) may be an Ag-Cu alloy with an Ag-to-Cu composition ratio of 7:3. As another preferred embodiment, the first filler layer (13) and the second filler layer (30) may be formed of Ag-Cu alloys with Ag-to-Cu composition ratios of 4:6 and 7:3, respectively.
[0051] For reference, in the embodiment, the second filler layer (30) mediates the bonding between the upper metal layer (14) and the conductive spacer (20) in the second brazing bonding process performed after the first brazing bonding between the ceramic substrate (12) and the metal layer by the first filler layer (13).
[0052] Ag alloys have the characteristic that the higher the Ag content, the lower the effective melting point. A lower effective melting point allows brazing to be performed at a lower temperature. The embodiment reflects this characteristic in its composition by using an Ag alloy with a higher Ag content than the first filler layer (13), which is the primary brazing bonding agent, as the secondary brazing bonding agent (second filler layer), thereby allowing the temperature of the secondary brazing process to be lowered compared to the primary brazing.
[0053] When an Ag-Cu alloy with an Ag-Cu composition ratio of 5:5 is used as the first filler layer (bonding agent for the first brazing bond), brazing bonding is possible at approximately 890°C according to the binary eutectic phase diagram of the Ag-Cu alloy. When an Ag-Cu alloy with an Ag-Cu composition ratio of 4:6 is used as the first filler layer (bonding agent for the first brazing bond), brazing bonding is possible at approximately 850°C.
[0054] In contrast, in the case of an Ag-Cu alloy with a composition ratio of Ag to Cu of 7:3, brazing can be performed at approximately 780°C according to the binary eutectic phase diagram of the Ag-Cu alloy. Therefore, if an Ag-Cu alloy with a composition ratio of Ag to Cu of 7:3 is used as the second filler layer (bonding agent for secondary brazing), brazing can be performed at a temperature approximately 70°C to 110°C lower than the brazing temperature of the first filler layer (13) with a composition of 5:5 or 4:6.
[0055] If the secondary brazing bonding temperature is lowered, the deformation caused by thermal expansion of the ceramic substrate (10) is reduced, thereby reducing thermal stress. Additionally, if the secondary brazing temperature is set lower than the liquidus temperature of the alloy composition of the first filler layer (13), the first filler layer (13) is not remelted, so the bonding state can be maintained stably, and the problem of layer separation (separation between the ceramic substrate and the metal layer) due to remelting can also be reliably prevented.
[0056] Since the first filler layer (13) is used for bonding between the ceramic substrate (12) and the upper and lower metal layers (14, 16), mechanical strength and heat resistance are important. Since the second filler layer (30) is used for bonding between the upper metal layer (14) and the conductive spacer (20), relatively high thermal conductivity and a low bonding temperature are more important. Therefore, adjusting the bonding characteristics by increasing the Ag content of the second filler layer (30) can be considered an effective design strategy to lower the bonding temperature between the upper metal layer (14) and the conductive spacer (20), improve thermal conductivity, and optimize overall heat dissipation performance.
[0057] According to the ceramic substrate unit of the embodiment of the present invention, by providing a conductive spacer that mediates the electrical connection between a semiconductor device and a ceramic substrate in place of conventional wires, potential risk factors such as electrical short circuits or open circuits can be eliminated in high-power and high-current environments. As a result, the reliability and efficiency of the power module are improved, and structurally, there is an advantage in that it can satisfy the heat dissipation characteristics and mechanical rigidity required by power modules that process high-voltage and high-current signals.
[0058] In addition, the present invention can lower the secondary bonding temperature during the manufacturing process by using an Ag alloy with a higher Ag content than the primary bonding layer (first filler layer) as the secondary bonding layer (second filler layer) (because Ag alloys have the characteristic that the effective melting point decreases as the Ag content increases). As a result, thermal stress applied to the substrate during the bonding process is reduced, and the quality and stability of the bonding layer can be maintained.
[0059] FIG. 3 is a flowchart illustrating a method for manufacturing a ceramic substrate unit for a power module according to an embodiment of the present invention.
[0060] Referring to FIG. 3 and the preceding drawings together, the manufacturing method according to the embodiment includes the step (S100) of bonding an upper metal layer (14) and a lower metal layer (16) to the upper and lower surfaces of a ceramic substrate (12) via a first filler layer (13), and the step (S200) of bonding a conductive spacer (20) to the upper metal layer (14) via a second filler layer (30). Here, the first filler layer (13) and the second filler layer (30) may be composed of an Ag alloy containing Ag. Preferably, they may be composed of Ag alloys with different alloy composition ratios.
[0061] In the step (S100) of bonding the upper metal layer and the lower metal layer, a first filler layer (13) is formed on the surface (upper and lower surfaces) of the ceramic substrate (12) using various methods such as paste application and sintering, sputtering deposition, foil attachment, and electroless plating. Then, a metal layer is placed on the upper and lower surfaces of the ceramic substrate (12) with the first filler layer (13) in between, and a brazing bonding process is performed at a set temperature to bond the metal layer (14, 16) to the ceramic substrate (12).
[0062] In the embodiment, the ceramic substrate (12) may be composed of one of alumina (Al2O3), zirconia-reinforced alumina (ZTA), aluminum nitride (AlN), or silicon nitride (Si3N4). The upper metal layer (14) and the lower metal layer (16), which are brazed to the upper and lower surfaces of the ceramic substrate (12), respectively, may be metal foils having high thermal and electrical conductivity characteristics. For example, they may be metal foils of Cu, Cu alloy, ETP, or OFC.
[0063] Although not illustrated, an additional step of brazing the upper metal layer (14) onto the ceramic substrate (12) and then processing the upper metal layer (14) into a predetermined circuit pattern shape may be added. In the step of processing the upper metal layer (14) into a predetermined circuit pattern shape, the upper metal layer (14) can be processed into an electrode pattern shape suitable for mounting a semiconductor chip or driving element through micro-machining or an etching process.
[0064] In the step of bonding the upper metal layer (14) and the lower metal layer (16), the first filler layer (13) may be an Ag alloy containing Ag. Preferably, the first filler layer (13) may be an Ag-Cu alloy. Since the Ag-Cu alloy has a high level of thermal conductivity, it can maximize heat dissipation performance in the power module when high heat is present. The Ag-Cu alloy can also maximize bonding strength while preserving the structural properties of the ceramic substrate due to its characteristics.
[0065] In particular, Ag has strong oxidation resistance, maintaining a stable state at high temperatures, and can contribute to maintaining stable bonding quality by suppressing oxide formation during the bonding process. Ag also has excellent wettability with metals or ceramics at specific brazing temperatures (typically 600–900°C), allowing it to spread uniformly across the bonding surface to form a solid bonding layer.
[0066] In the step (S200) of bonding a conductive spacer to an upper metal layer, the bonding of the conductive spacer (20) can be achieved by forming a second filler layer (30) on the surface of the upper metal layer (14) to which the conductive spacer (20) is attached or on the surface of the conductive spacer (20) to which it is bonded to the upper metal layer (14) (lower surface in the drawing) using various methods such as paste application and sintering, sputtering deposition, foil attachment, and electroless plating, and then placing the conductive spacer (20) at a designated location on the upper metal layer (14) and performing brazing bonding at a set temperature.
[0067] In the step (S200) of bonding a conductive spacer (20) to an upper metal layer (14), the second filler layer (30) may be an Ag alloy containing Ag. Preferably, the second filler layer (30) may be an Ag-Cu alloy. Since the Ag-Cu alloy has a high level of thermal conductivity, it can maximize heat dissipation performance in a high-temperature power module. The Ag-Cu alloy can also maximize bonding strength while preserving the structural properties of the ceramic substrate (12) due to its characteristics.
[0068] In particular, Ag has strong oxidation resistance, maintaining a stable state at high temperatures, and can contribute to maintaining stable bonding quality by suppressing oxide formation during the bonding process. Ag also has excellent wettability with metals or ceramics at specific brazing temperatures (typically 600–900°C), allowing it to spread uniformly across the bonding surface to form a solid bonding layer.
[0069] In the manufacturing method according to the embodiment, the first filler layer (13) mediating the bonding between the ceramic substrate (12) and the metal layer, and the second filler layer (30) mediating the bonding between the upper metal layer (14) and the conductive spacer (20) may both be Ag alloys as mentioned. Preferably, the first filler layer (13) and the second filler layer (30) may both be Ag-Cu alloys. As a more specific embodiment, the first filler layer (13) and the second filler layer (30) may be Ag-Cu alloys with different compositional ratios (mixing ratios) of Ag and Cu.
[0070] In the embodiment, the second filler layer (30) may be an Ag-Cu alloy having a higher Ag content than the Ag content of the first filler layer (13). As a preferred embodiment, the first filler layer (13) may be formed of an Ag-Cu alloy with an Ag-to-Cu composition ratio of 5:5, and the second filler layer (30) may be an Ag-Cu alloy with an Ag-to-Cu composition ratio of 7:3. As another preferred embodiment, the first filler layer (13) and the second filler layer (30) may be formed of Ag-Cu alloys with Ag-to-Cu composition ratios of 4:6 and 7:3, respectively.
[0071] Ag alloys have the characteristic that the higher the Ag content, the lower the effective melting point. A lower effective melting point allows brazing to be performed at a lower temperature. The embodiment reflects this characteristic in its composition by using an Ag alloy with a higher Ag content than the first filler layer (13), which is the primary brazing bonding agent, as the secondary brazing bonding agent (second filler layer), thereby allowing the temperature of the secondary brazing process to be lowered compared to the primary brazing.
[0072] When an Ag-Cu alloy with an Ag-Cu composition ratio of 5:5 is used as the first filler layer (bonding agent for the first brazing bond), brazing bonding is possible at approximately 890°C according to the binary eutectic phase diagram of the Ag-Cu alloy. When an Ag-Cu alloy with an Ag-Cu composition ratio of 4:6 is used as the first filler layer (bonding agent for the first brazing bond), brazing bonding is possible at approximately 850°C.
[0073] In contrast, in the case of an Ag-Cu alloy with a composition ratio of Ag to Cu of 7:3, brazing can be performed at approximately 780°C according to the binary eutectic phase diagram of the Ag-Cu alloy. Therefore, if an Ag-Cu alloy with a composition ratio of Ag to Cu of 7:3 is used as the second filler layer (bonding agent for secondary brazing), brazing can be performed at a temperature approximately 70°C to 110°C lower than the brazing temperature of the first filler layer (13) with a composition of 5:5 or 4:6.
[0074] If the secondary brazing bonding temperature is lowered, the deformation caused by thermal expansion of the ceramic substrate (10) is reduced, thereby alleviating thermal stress. Additionally, if the secondary brazing temperature is set lower than the liquidus temperature of the alloy composition of the first filler layer (13), the first filler layer (13) is not remelted, so the bonding state can be maintained stably, and the problem of layer separation (separation between the ceramic substrate and the metal layer) due to remelting can also be reliably prevented.
[0075] The first filler layer (13) used for bonding between the ceramic substrate (12) and the upper and lower metal layers (14, 16) is important for mechanical strength and heat resistance. The second filler layer (30) used for bonding between the lower metal layer (16) and the conductive spacer (20) is more important for relatively high thermal conductivity and a low bonding temperature. Therefore, adjusting the bonding characteristics by increasing the Ag content of the second filler layer (30) can be considered an effective design strategy to lower the bonding temperature between the upper metal layer (14) and the conductive spacer (20), improve thermal conductivity, and optimize overall heat dissipation performance.
[0076] According to the manufacturing method of the present invention, the secondary bonding temperature can be lowered during the manufacturing process by using an Ag alloy with a higher Ag content than the primary bonding layer (first filler layer) as the secondary bonding layer (second filler layer). This is due to the inherent characteristic of Ag alloys, where the effective melting point decreases as the Ag content increases. As a result, the thermal stress applied to the substrate during the secondary bonding process is reduced, and the quality and stability of the bonding layer can be maintained.
[0077] In other words, by using an Ag alloy with a higher Ag content than the primary bonding layer (first filler layer) as the secondary bonding layer (second filler layer), the substrate can be safely protected from thermal shock, and the bonding strength of the substrate can be secured, thereby resolving problems such as bonding defects and the resulting layer separation or degradation of properties. In addition, since stable and robust bonding between components is achieved, a high-power module capable of stable and reliable power transmission even in high-voltage and high-current environments can be provided.
[0078] The ceramic substrate unit according to such an embodiment of the present invention can be applied to a single-sided or double-sided cooling power module, and can also be applied to various devices requiring high power and high heat dissipation characteristics.
[0079] The above description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention.
[0080] Accordingly, the embodiments disclosed in this invention are intended to illustrate, not limit, the technical concept of the invention, and the scope of the technical concept of the invention is not limited by these embodiments. The scope of protection of this invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of this invention.
Claims
1. As a ceramic substrate unit for a power module, A ceramic substrate having an upper metal layer and a lower metal layer formed on the upper and lower surfaces of the ceramic substrate; A first filler layer disposed between the ceramic substrate and the upper metal layer and between the ceramic substrate and the lower metal layer; A plurality of conductive spacers, one side of which is bonded to the upper metal layer of the ceramic substrate; and A second filler layer disposed between the upper metal layer and the conductive spacer; comprising The first and second filler layers are composed of an Ag alloy containing Ag, and A ceramic substrate unit for a power module, wherein the alloy composition ratios of the first filler layer and the second filler layer are different.
2. In Paragraph 1, The upper metal layer and the lower metal layer above are, A ceramic substrate unit for a power module formed from one of the following materials: Cu, Cu alloy, ETP (Electrolytic Tough Pitch), OFC (Oxygen-Free Copper), or Al.
3. In Paragraph 1, The above conductive spacer is, A ceramic substrate unit for a power module formed from one of the following materials: Cu, Cu alloy, Mo, or CPC (Conductive Polymer Composite).
4. In Paragraph 1, The first and second filler layers are Ag-Cu alloys, and A ceramic substrate unit for a power module, wherein the Ag content of the second filler layer is higher than the Ag content of the first filler layer.
5. In Paragraph 1, The first filler layer above is an Ag-Cu alloy with a composition ratio of Ag to Cu of 5:5, and A ceramic substrate unit for a power module, wherein the second filler layer is an Ag-Cu alloy with a composition ratio of Ag to Cu of 7:
3.
6. In Paragraph 1, The first filler layer above is an Ag-Cu alloy with a composition ratio of Ag to Cu of 4:6, and A ceramic substrate unit for a power module, wherein the second filler layer is an Ag-Cu alloy with a composition ratio of Ag to Cu of 7:
3.
7. A method for manufacturing a ceramic substrate unit for a power module, A step of bonding an upper metal layer and a lower metal layer to the upper and lower surfaces of a ceramic substrate via a first filler layer; and The method includes the step of bonding a conductive spacer to the upper metal layer via a second filler layer; The above first filler layer and second filler layer are composed of an Ag alloy containing Ag, A method for manufacturing a ceramic substrate unit for a power module, wherein the alloy composition ratios of the first filler layer and the second filler layer are different from each other.
8. In Paragraph 7, The above upper metal layer and lower metal layer are formed from one of the following materials: Cu, Cu alloy, ETP (Electrolytic Tough Pitch), OFC (Oxygen-Free Copper), and Al. A method for manufacturing a ceramic substrate unit for a power module, wherein the conductive spacer is formed from one of the following materials: Cu, Cu alloy, Mo, or CPC (Conductive Polymer Composite).
9. In Paragraph 7, The first and second filler layers are Ag-Cu alloys, and A method for manufacturing a ceramic substrate unit for a power module, wherein the Ag content of the second filler layer is higher than the Ag content of the first filler layer.
10. In Paragraph 7, The first filler layer above is an Ag-Cu alloy with a composition ratio of Ag to Cu of 5:5 to 4:6, and A method for manufacturing a ceramic substrate unit for a power module, wherein the second filler layer is an Ag-Cu alloy with a composition ratio of Ag to Cu of 7:3.