A power module housing manufacturing method for replacing a conventional brazing insulator process

Abstract

The present application relates to power module shell preparation technical field, especially in a kind of power module shell preparation method of replacing traditional brazing insulator process.It is to process the surface of the main structure of aluminum-based in hollow structure, according to the size of hollow structure, the welding ring of iron-based material is processed, so that the welding ring is embedded in hollow structure after;Transition layer is arranged on the outer surface of welding ring and the surface of hollow structure;With transition layer, the welding ring is embedded in hollow structure plated with transition layer, and the expansion block matching the shape of welding ring is embedded in welding ring;Plate body is placed in graphite mould, and high temperature treatment is carried out, so that welding ring is fixed in hollow structure;With the inner diameter shape of welding ring matching, the iron-based pinout board is laser welded on welding ring, and insulator pin is processed on pinout board;After the aluminum plate welded with insulator pin and other aluminum plates are connected, power module shell is obtained.The present application can provide a kind of power module shell preparation method which replaces traditional brazing, and the cost is lower.

Description

Technical Field

[0001] This invention relates to the field of power module housing manufacturing technology, and in particular to a method for manufacturing power module housings that replaces the traditional brazing insulator process. Background Technology

[0002] In modern aviation, aerospace, radar, communications, high-speed rail and other application fields, the power supply of circuit systems is mostly completed by distributed standardized power modules. The power modules contain electronic components such as conversion circuits, voltage regulation circuits, control circuits and transformers.

[0003] Traditional power module packaging typically uses materials like low-carbon steel and Kovar alloy for the casing. The sides of the casing are usually sealed with high-temperature fired glass or ceramic to create leads that function as input / output power and control / communication. A hermetically sealed connection is required between the leads and the casing material. However, with the development of electronic circuits and the application of next-generation semiconductor materials, the power of power modules is increasing dramatically, with advanced modules approaching 500W or even 800W. In this situation, traditional low-carbon steel and Kovar alloys, due to their poor thermal conductivity, cannot dissipate the heat generated during operation, causing the entire power module to overheat and exceed relevant temperature control requirements.

[0004] Under these circumstances, the use of low-carbon steel and Kovar alloy casings has been gradually abandoned or reduced, replaced by packaging materials represented by aluminum-based alloys (mainly high-silicon aluminum alloys). However, when using aluminum-based alloys for the casing, the original glass sealing and ceramic firing (welding) processes cannot be used for the casing leads, because aluminum alloys or silicon-aluminum materials cannot withstand the high temperatures (700~800℃) during firing. Instead, traditional brazing processes are adopted, with high-temperature brazing, typically gold-tin brazing, being more suitable. Gold-tin brazing is widely used and the process is relatively mature, but its disadvantage is its high cost because it requires gold-tin solder (Au80Sn20). During brazing, each insulator lead requires a ring made of gold-tin solder, and the corresponding holes on the casing also need to be gold-plated. The entire process makes this solution costly.

[0005] Therefore, in order to address the above problems, there is an urgent need for a power module housing manufacturing method that can replace traditional brazing and has a lower cost. Summary of the Invention

[0006] This invention provides a method for manufacturing a power module housing that replaces the traditional brazing insulator process, offering a lower-cost alternative to traditional brazing.

[0007] This invention provides a method for manufacturing a power module housing that replaces the traditional brazing insulator process, comprising: A hollow structure is processed on the surface of the aluminum-based main structure, and a welding ring of iron-based material is processed according to the size of the hollow structure, so that the welding ring is embedded in the hollow structure while maintaining a gap of a preset thickness. A transition layer is provided between the outer surface of the welding ring and the surface of the hollow structure; wherein the thickness of the transition layer is not greater than 1 / 2 of the preset thickness; A welding ring with the transition layer is embedded in the hollow structure coated with the transition layer, and an expansion block matching its shape is embedded inside the welding ring; The main structure is placed in a graphite mold and subjected to high temperature treatment to fix the welding ring in the hollow structure; An iron-based pin header plate, whose shape matches the inner diameter of the welding ring, is laser-welded onto the welding ring. The pin header plate is machined with insulator pins.

[0008] Optionally, the transition layer is composed of nickel powder, copper powder, and alumina powder.

[0009] Optionally, the particle size of the powder in the transition layer is 20~50μm, and the preset thickness is 300~600μm (to ensure uniform spreading and densification, making it easier to form a uniform layer; too thin may not be effective in blocking, while too thick may become a performance bottleneck).

[0010] Optionally, the transition layer is applied to the surface to be coated using an electrostatic spraying process.

[0011] Optionally, the high-temperature treatment includes heating at 2~3℃ / min to 250~300℃, heating at 5~6℃ / min to 500~550℃, and then natural cooling.

[0012] Optionally, the expansion block may be made of brass.

[0013] Optionally, an isolation layer is laid between the expansion block and the welding ring.

[0014] Optionally, the insulating layer comprises nickel foil.

[0015] Optionally, the thickness of the isolation layer is 1~50μm.

[0016] Optionally, the pin header plate is provided with multiple insulating sheets, and the insulator pins are passed through the insulating sheets.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: In this embodiment, an aluminum-based alloy with excellent heat dissipation properties is used to prepare the main structure of the power module housing, enabling the resulting housing to adapt to high-power power supplies. In this invention, a hollow structure is first machined into the aluminum-based alloy main structure, and a welding ring is placed on the hollow structure. The welding ring is connected to the hollow structure by hot pressing and sintering. Then, a pin header plate matching the shape of the inner ring of the welding ring is sealed and connected to the welding ring by simple laser welding. The pin header plate is also made of an iron-based material, allowing it to be sealed and connected to the welding ring by simple laser welding. Furthermore, the iron-based pin header plate can also have insulator pins installed using traditional firing methods. Thus, a low-cost, high-heat-dissipation, and simple-to-manufacture power module housing is obtained.

[0018] To ensure a tight connection between the welded ring and the hollow structure, this application utilizes an expansion block in conjunction with an external high-hardness graphite mold, achieving a solution where a simple high-temperature treatment is sufficient for complete bonding. Since aluminum-based materials have relatively low hardness, direct hot pressing may cause deformation of the aluminum plate. This application, by incorporating an expansion block inside the welded ring, eliminates the need for pressure on the overall mold. The thermal expansion of the expansion block allows pressure to be applied directly to the welded ring and the hollow structure, creating localized high pressure where necessary, thus ensuring a thorough bonding under high temperature and pressure.

[0019] To improve the bonding strength between aluminum-based and iron-based materials, a transition layer is set between the welding ring and the hollow structure. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the main structure provided by the present invention; Figure 2 This is a schematic diagram of the structure of a pin header plate provided by the present invention; Figure 3 This is a schematic diagram of the structure of a power module housing that replaces the traditional brazing insulator process provided by the present invention.

[0022] Figure label: 101-Main structure; 102-Hollowed structure; 103-Welding ring; 201-Pin plate; 202-Insulator pin array; 203-Insulating sheet. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] Please refer to Figures 1 to 3 This invention provides a method for manufacturing a power module housing that replaces the traditional brazing insulator process, comprising: A hollow structure is processed on the surface of the aluminum-based main structure, and a welding ring of iron-based material is processed according to the size of the hollow structure, so that the welding ring is embedded in the hollow structure while maintaining a gap of a preset thickness. A transition layer is provided between the outer surface of the welding ring and the surface of the hollow structure; wherein the thickness of the transition layer is not greater than 1 / 2 of the preset thickness; A welding ring with the transition layer is embedded in the hollow structure coated with the transition layer, and an expansion block matching its shape is embedded inside the welding ring; The main structure is placed in a graphite mold and subjected to high temperature treatment to fix the welding ring in the hollow structure; An iron-based pin header plate, whose shape matches the inner diameter of the welding ring, is laser-welded onto the welding ring. The pin header plate is machined with insulator pins.

[0025] In this embodiment, an aluminum-based alloy with excellent heat dissipation properties is used to prepare the main structure of the power module housing, enabling the resulting housing to adapt to high-power power supplies. In this invention, a hollow structure is first machined into the aluminum-based alloy main structure, and a welding ring is placed on the hollow structure. The welding ring is connected to the hollow structure by hot pressing and sintering. Then, a pin header plate matching the shape of the inner ring of the welding ring is sealed and connected to the welding ring by simple laser welding. The pin header plate is also made of an iron-based material, allowing it to be sealed and connected to the welding ring by simple laser welding. Furthermore, the iron-based pin header plate can also have insulator pins installed using traditional firing methods. Thus, a low-cost, high-heat-dissipation, and simple-to-manufacture power module housing is obtained.

[0026] To ensure a tight connection between the welded ring and the hollow structure, this application utilizes an expansion block in conjunction with an external high-hardness graphite mold, achieving a solution where a simple high-temperature treatment is sufficient for complete bonding. Since aluminum-based materials have relatively low hardness, direct hot pressing may cause deformation of the aluminum plate. This application, by incorporating an expansion block inside the welded ring, eliminates the need for pressure on the overall mold. The thermal expansion of the expansion block allows pressure to be applied directly to the welded ring and the hollow structure, creating localized high pressure where necessary, thus ensuring a thorough bonding under high temperature and pressure.

[0027] To improve the bonding strength between aluminum-based and iron-based materials, a transition layer is set between the welding ring and the hollow structure.

[0028] It should be noted that the main structure can be formed by connecting multiple plates, or it can be formed by machining in one piece.

[0029] In this embodiment, aluminum-based materials include aluminum alloys, silicon-aluminum alloys, and silicon-aluminum carbide. Iron-based materials include steel, stainless steel, or Kovar.

[0030] In some embodiments of the present invention, the transition layer is composed of nickel powder, copper powder and alumina powder.

[0031] In this embodiment, Ni / Cu powder is miscible with both Fe and Al or forms compounds, but the reaction kinetics are slow, thus serving as an effective diffusion barrier. Furthermore, the addition of alumina inert ceramic particles effectively blocks the interdiffusion of Fe and Al atoms. Simultaneously, alumina also improves the hardness and wear resistance of the intermediate layer.

[0032] It should also be noted that the powder layer has a certain porosity, and the space within the porosity provides room for the expansion and compaction of the expanding block. Furthermore, the powder has a certain shape, and under the pressure of the expanding block in the early stages, they interlock with each other, resulting in a stronger interfacial bond.

[0033] In some embodiments of the present invention, the particle size of the powder in the transition layer is 20-50 μm, and the preset thickness is 300-600 μm.

[0034] In this embodiment, particle size within the above range ensures uniform spreading and densification, making it easier to form a uniform layer. Thickness needs to be controlled within the above range; too thin a layer may not provide effective barrier properties, while too thick a layer may become a performance bottleneck.

[0035] In some embodiments of the present invention, the transition layer is applied to the surface to be coated by an electrostatic spraying process.

[0036] In this embodiment, the electrostatic spraying process is operated at room temperature, which can obtain a powder layer with uniform thickness and high powder utilization (>95%), making it easy to form a uniformly covered powder layer on complex shapes.

[0037] In some embodiments of the present invention, the high-temperature treatment includes heating at 2~3℃ / min to 250~300℃, heating at 5~6℃ / min to 500~550℃, and then natural cooling.

[0038] In this embodiment, the initial heating rate needs to be controlled within a relatively slow range to allow the expansion block to fully expand and provide expansion force. After heating to 250~300℃, the heating rate is increased to 500~550℃ to allow for full diffusion and bonding at the interface. Finally, it is allowed to cool naturally to obtain a material with high interfacial bonding strength.

[0039] In some embodiments of the present invention, the material used to prepare the expansion block includes brass.

[0040] In this embodiment, brass has a good coefficient of thermal expansion and a high modulus, which makes it easy to provide expansion stress, and its expansion force can reach hundreds of megapascals.

[0041] In some embodiments of the present invention, an isolation layer is laid between the expansion block and the welding ring.

[0042] In this embodiment, in order to prevent the expansion block from bonding with the welding ring under high temperature and high pressure, an isolation layer is provided between the two to facilitate subsequent separation of the two.

[0043] In some embodiments of the present invention, the insulating layer comprises nickel foil. Of course, it can also be other sheets with insulating functions.

[0044] In some embodiments of the present invention, the thickness of the isolation layer is 1~50μm.

[0045] In some embodiments of the present invention, a plurality of insulating sheets are disposed on the pin header plate, and the insulator pins are inserted through the insulating sheets. The insulating material includes ceramics and glass.

[0046] In some embodiments of the present invention, the aluminum-based alloy includes aluminum alloy, silicon-aluminum alloy, and silicon-aluminum carbide.

[0047] In some embodiments of the present invention, the iron-based alloy includes steel, stainless steel, or Kovar.

[0048] To more clearly illustrate the technical solution and advantages of the present invention, the following describes the solution of this application in detail through several embodiments.

[0049] Example 1 1. Material and workpiece preparation: Base material: Aluminum plate with pre-fabricated perforated structure.

[0050] Connector: Iron-based welded ring (machined according to the dimensions of the aluminum plate's hollow structure to ensure a single-sided gap of 420μm after embedding).

[0051] Functional components: brass expansion block (shape matches the inner cavity of the welding ring), iron-based pin header plate (with prefabricated insulator pin header).

[0052] Auxiliary materials: Transition layer powder: a mixture of nickel powder, copper powder, and alumina powder.

[0053] Barrier layer: Nickel foil.

[0054] Tooling: Graphite mold.

[0055] 2. Main equipment: Electrostatic spraying equipment.

[0056] Box-type / tube-type heating furnace (temperature controllable).

[0057] Laser welding machine.

[0058] Machining equipment (used for processing hollow structures, welding rings, expansion blocks, and pin headers).

[0059] 3. Experimental procedures and process parameters: Step 1: Workpiece pretreatment Clean the surface of the aluminum plate with its hollow structure and the outer surface of the iron-based welded ring to ensure that there is no oil or oxides.

[0060] Step 2: Preparation and application of the transition layer Transition layer composition: a mixture of nickel powder, copper powder, and alumina powder.

[0061] Powder particle size: 20~50 μm.

[0062] Application method: Electrostatic spraying.

[0063] Application location and thickness: A uniform coating with a thickness of 200 μm is applied to the outer surface of the iron-based welded ring.

[0064] A uniform coating with a thickness of 200 μm is applied to the inner surface of the hollowed-out aluminum plate.

[0065] Post-application treatment: Allow to dry at room temperature.

[0066] Step 3: Assembly and Embedding The welding ring coated with the transition layer is embedded in the hollow structure of the aluminum plate coated with the transition layer.

[0067] A layer of nickel foil is laid inside the cavity of the welding ring.

[0068] The brass expansion block is embedded into the inner cavity of the welding ring, placing it on top of the nickel foil.

[0069] Step 4: Heat treatment connection (brazing) Mold: Place the above assembly in a graphite mold.

[0070] Heat treatment process: Heat to 280℃ at a heating rate of 2.5 ℃ / min.

[0071] Then, the temperature was increased to 530°C at a rate of 5.5 °C / min.

[0072] Once the temperature reaches 530°C, stop heating and allow it to cool naturally to room temperature inside the furnace or in the air.

[0073] Result: Through this heat treatment process, the transition layer material is activated, achieving metallurgical bonding and fixation between the welding ring and the hollow structure of the aluminum plate.

[0074] Step 5: Soldering the pin header plate Laser welding is used to weld the iron-based pin header plate to a welding ring that has been fixed on an aluminum plate.

[0075] Features of the pin header plate: The pin header plate has been pre-machined with insulator pins, and its shape matches the inner diameter of the welding ring.

[0076] Step 6: Final Assembly The aluminum plate that has been welded as described above is mechanically connected or welded to other aluminum plate components to assemble a complete power module housing.

[0077] 4. Key Process Points: Gap control: The 420μm single-sided gap provides space for the transition layer material and helps to alleviate thermal stress.

[0078] Transition layer function: The Ni / Cu / Al2O3 mixed powder layer is designed to promote the bonding of Fe-Al dissimilar materials and suppress brittle phases.

[0079] The function of the nickel foil is to be placed between the brass expansion block and the welding ring to prevent diffusion bonding between the two during heat treatment.

[0080] Heat treatment curve: Segmented heating is intended to control the diffusion reaction and stress between materials.

[0081] The obtained product was subjected to an interfacial shear strength test, and the shear strength was 73.4 MPa.

[0082] Finally, it should be noted that the above embodiments and comparative examples are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments and comparative examples, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments and comparative examples, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments and comparative examples of the present invention.

Claims

1. A method for manufacturing a power module housing that replaces the traditional brazing insulator process, characterized in that, include: A hollow structure is processed on the surface of the aluminum-based main structure, and a welding ring of iron-based material is processed according to the size of the hollow structure, so that the welding ring is embedded in the hollow structure while maintaining a gap of a preset thickness. A transition layer is provided between the outer surface of the welding ring and the surface of the hollow structure; wherein the thickness of the transition layer is not greater than 1 / 2 of the preset thickness; A welding ring with the transition layer is embedded in the hollow structure coated with the transition layer, and an expansion block matching its shape is embedded inside the welding ring; The main structure is placed in a graphite mold and subjected to high temperature treatment to fix the welding ring in the hollow structure; An iron-based pin header plate, whose shape matches the inner diameter of the welding ring, is laser-welded onto the welding ring. The pin header plate is machined with insulator pins.

2. The preparation method according to claim 1, characterized in that, The transition layer is composed of nickel powder, copper powder and alumina powder.

3. The preparation method according to claim 2, characterized in that, The particle size of the powder in the transition layer is 20~50μm, and the preset thickness is 300~600μm.

4. The preparation method according to claim 2, characterized in that, The transition layer is applied to the surface to be coated using an electrostatic spraying process.

5. The preparation method according to claim 1, characterized in that, The high-temperature treatment includes heating at 2~3℃ / min to 250~300℃, heating at 5~6℃ / min to 500~550℃, and then natural cooling.

6. The preparation method according to claim 1, characterized in that, The expansion block is made of brass.

7. The preparation method according to claim 1, characterized in that, An isolation layer is laid between the expansion block and the welding ring.

8. The preparation method according to claim 7, characterized in that, The insulating layer comprises nickel foil.

9. The preparation method according to claim 7, characterized in that, The thickness of the isolation layer is 1~50μm.

10. The preparation method according to claim 1, characterized in that, The pin header plate is provided with multiple insulating sheets, and the insulator pins are passed through the insulating sheets.

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