Method for manufacturing multilayer circuit board through low-temperature thermocompression welding

Abstract

The invention relates to a method for manufacturing a multi-layer circuit board through low-temperature thermocompression welding, and the method comprises the following steps: S100, respectively manufacturing metal circuit patterns at two sides of a plurality of circuit boards, and enabling the metal circuit patterns at the opposite sides of any two adjacent circuit boards to be arranged in a mirror symmetry manner; s200, grinding and polishing the metal circuit pattern, and controlling the surface roughness and flatness; s300, coating a bonding layer on the surface of the metal circuit pattern; and S400, the circuit boards are stacked and then placed in a working cavity of a hot press for diffusion welding. The invention mainly aims to provide a method for manufacturing a multilayer circuit board through low-temperature thermocompression welding, and a multilayer metal circuit is formed on a ceramic substrate through a special stacking process.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a circuit board, and in particular to a method for manufacturing a multi-layer circuit board by low-temperature hot pressing welding. Background Art

[0002] Ceramic substrate is a special process board. This ultra-thin composite substrate has excellent electrical insulation performance, high thermal conductivity, excellent soft solderability and high adhesion strength. It can be etched with various patterns like PCB boards and has a large current carrying capacity. Therefore, ceramic substrate has become the basic material for high-power power electronic circuit structure technology and interconnection technology.

[0003] However, in the prior art, metal circuit patterns are printed on both sides of the ceramic substrate. However, there are currently no solutions to the problem of printing metal circuit patterns inside the ceramic substrate to form a multi-level metal circuit on the ceramic substrate. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for manufacturing a multi-layer circuit board by low-temperature hot pressing welding, so as to form a multi-level metal circuit on a ceramic substrate through a special stacking process.

[0005] In order to achieve the above object, the present invention provides a method for manufacturing a multi-layer circuit board by low temperature hot pressing welding, comprising the following steps: S100: Making metal circuit patterns on both sides of a plurality of circuit boards respectively, wherein the metal circuit patterns on opposite sides of any two adjacent circuit boards are arranged in mirror symmetry; S200: Grinding and polishing of metal circuit patterns to control surface roughness and flatness; S300: coating a bonding layer on the surface of the metal circuit pattern; S400: After stacking these circuit boards, place them in the working chamber of the hot press for diffusion welding.

[0006] Preferably, in step S100, a metal circuit pattern is produced on the circuit board by vacuum plating, chemical plating or electroplating.

[0007] Preferably, in step S100, the metal patterns of the metal circuit patterns of the two opposite circuit boards are respectively a pure copper layer and a tungsten-titanium alloy layer.

[0008] Further preferably, the titanium content in the tungsten-titanium alloy layer is 2.2%, the crystal structure of tungsten in the tungsten-titanium alloy is a face-centered cubic structure, and the crystal structure of titanium is a close-packed hexagonal lattice structure.

[0009] More preferably, the bonding layer is a silver-based alloy layer.

[0010] Preferably, in step S400, the temperature in the working chamber of the hot press is 883-890 degrees, the pressure is 400 kilograms per cubic centimeter, the heating rate is 10 degrees to 30 degrees per minute, the insulation time is 10-15 minutes, the cooling rate is 10 degrees to 30 degrees per minute, and the working chamber is filled with argon.

[0011] Further preferably, in step S400, the temperature in the working chamber of the hot press is 885 degrees, the pressure is 400 kilograms per cubic centimeter, the heating rate is 15 degrees per minute, the insulation time is 11 minutes, the cooling rate is 15 degrees per minute, and the working chamber is filled with argon.

[0012] Preferably, a blowing device is further provided in the working chamber, and the gas blown out by the blowing device can accelerate the gas flow around the semiconductor in the working chamber.

[0013] Further preferably, the blowing device includes a cone, a sleeve and an air inlet pipe, the large end of the cone is located at the top, the small end of the cone is located at the bottom, the small end of the cone is provided with a connecting pipe, and the large end of the cone is in a sealed state through a sealing plate, the top of the sleeve is sealed and connected to the sealing plate, the sleeve is arranged on the outside of the pressure arm of the hot press, the bottom end of the sleeve extends out of the connecting pipe, the sleeve is coaxially arranged with the cone, a plurality of through holes are provided on the top of the sleeve, the air inlet pipe is connected with the large end of the cone, and the gas blown out of the air inlet pipe is located in the tangential direction of the large end of the cone.

[0014] The beneficial effects of the present invention are: The present invention utilizes diffusion welding technology and changes process conditions to weld a plurality of ceramic substrates together, thereby realizing welding of multi-level metal circuits on the ceramic substrates.

[0015] The method for manufacturing the ceramic substrate of the present invention has the following beneficial effects: By making metal circuit patterns on both sides of multiple circuit boards respectively and ensuring that the metal circuit patterns of adjacent circuit boards are arranged in mirror symmetry, better alignment and contact can be achieved during the welding process, thereby improving welding quality; Grinding and polishing metal circuit patterns to control surface roughness and flatness helps improve welding reliability and consistency and reduce welding defects; Coating a silver-based alloy on the surface of the metal circuit pattern as a bonding layer effectively enhances the connection strength between circuit boards and improves the overall performance of multi-layer circuit boards; By using diffusion welding technology, the mutual diffusion between metal atoms is achieved at a lower temperature to form a strong metal bond, thereby improving the reliability and durability of multi-layer circuit boards; The present invention uses a pure copper layer and a tungsten-titanium alloy layer as materials for the metal circuit pattern, effectively utilizing the high melting point and good electrical conductivity of the tungsten-titanium alloy, while the high thermal conductivity of the pure copper layer facilitates rapid heat conduction, thereby improving welding efficiency; Filling the working chamber with argon as a protective atmosphere can prevent oxidation and other adverse chemical reactions, protecting the circuit board material and welding quality; The blowing device in the working chamber uses the principle of aerodynamics to accelerate the gas flow, which helps to evenly distribute the temperature and atmosphere, improve the uniformity and efficiency of welding, and at the same time can effectively guide the gas flow to ensure a stable and controllable welding environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0017] Figure 1 It is a schematic structural diagram of the blowing device of the present invention.

[0018] Description of Reference Numerals 1. Lower support plate; 2. Upper pressure plate; 3. Lower support column; 4. Upper pressure column; 10. working chamber; 20. cone; 21. sealing plate; 22. connecting pipe; 30. Casing; 40. Air intake duct. DETAILED DESCRIPTION

[0019] The technical scheme in the embodiment of the present invention is described clearly and completely below in conjunction with the accompanying drawings in the embodiment of the present invention. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0020] This embodiment provides a method for manufacturing a multi-layer circuit board by low-temperature hot pressing welding, comprising the following steps: S100: metal circuit patterns are respectively produced on both sides of a plurality of circuit boards, wherein the metal circuit patterns on opposite sides of any two adjacent circuit boards are arranged in mirror symmetry.

[0021] Specifically, in step S100, a metal circuit pattern is made on the circuit board by vacuum plating, chemical plating or electroplating. In addition, in step S100, the metal patterns of the metal circuit patterns of the two opposite circuit boards are respectively a pure copper layer and a tungsten-titanium alloy layer.

[0022] It should be noted that the content of titanium in the tungsten-titanium alloy layer is 1.5% to 3%, and preferably, 2.2% is selected in this embodiment. According to the metallic properties of titanium, the content of titanium should not be too high to avoid poor conductivity of the metal circuit. In order to better weld the pure copper layer and the tungsten-titanium alloy layer during the diffusion welding process, in this embodiment, the crystal structure of tungsten in the tungsten-titanium alloy is a face-centered cubic structure (i.e., β-tungsten), and the crystal structure of titanium is a close-packed hexagonal lattice structure.

[0023] S200: Grinding and polishing the metal circuit pattern to control the surface roughness and flatness. Preferably, the surface needs to reach a nanometer-level polishing degree, preferably, below 10 nanometers.

[0024] S300: coating a bonding layer on the surface of the metal circuit pattern. In this step, preferably, the bonding layer is a silver-based alloy layer.

[0025] S400: After stacking the circuit boards, place them in the working chamber 10 of the hot press for diffusion welding.

[0026] Specifically, in this step, the temperature in the working chamber 10 of the hot press is 883-890 degrees, the pressure is 400 kilograms per cubic centimeter, the heating rate is 10 degrees to 30 degrees per minute, the insulation time is 10-15 minutes, the cooling rate is 10 degrees to 30 degrees per minute, and the working chamber 10 is filled with argon.

[0027] Specifically, in this embodiment, the temperature in the working chamber 10 of the hot press is 885 degrees, the pressure is 400 kilograms per cubic centimeter, the heating rate is 15 degrees per minute, the insulation time is 11 minutes, the cooling rate is 15 degrees per minute, and the working chamber 10 is filled with argon.

[0028] In this embodiment, since the present application adopts a tungsten-titanium alloy layer, the temperature of the diffusion welding is selected to be 885 degrees. In this way, when the β-tungsten is higher than 630 degrees, oxygen desorption will occur, thereby converting the β-tungsten into α-tungsten. When the β-tungsten is converted into α-tungsten, the molecules will produce a phase phenomenon and rearrange, thereby facilitating the diffusion reaction between the pure copper layer and the tungsten-titanium layer. The present embodiment adds a certain amount of titanium metal, so that the metal circuit of the present embodiment has a certain corrosion resistance, and titanium will also be converted into β-titanium at 883 degrees. As mentioned above, during the conversion process, the titanium molecules will also produce a phase phenomenon, and after the temperature is lower than 883 degrees, the β-titanium will be converted into α-titanium, so that the phase phenomenon will occur again, further optimizing the diffusion reaction. Therefore, this embodiment adopts step cooling.

[0029] In addition, it should be noted that since the working temperature of the present application is not higher than 890 degrees, after the diffusion welding is completed, annealing measures can be taken according to the thickness of the pure copper layer to reduce the stress generated after the diffusion welding. In this embodiment, the thickness of the pure copper layer is 15 μm, so this embodiment does not adopt a subsequent annealing process.

[0030] As mentioned above, the β-tungsten in this embodiment releases oxygen atoms during the conversion process of α-tungsten. In order to prevent the oxygen molecules from reacting with pure copper to form copper oxide and causing an oxidation-reduction reaction, it is necessary to carry out the reaction in a protective atmosphere. Therefore, argon gas is filled in the working chamber 10 to drive the oxygen molecules away from the ceramic substrate.

[0031] In this embodiment, if Figure 1 As shown, in order to drive away oxygen molecules as quickly as possible, a blowing device is further provided in the working chamber 10. The gas blown out by the blowing device can accelerate the gas flow around the semiconductor in the working chamber 10, and the blowing device is used to blow away the gas near the ceramic substrate.

[0032] Specifically, in this embodiment, if Figure 1 As shown, an upper pressure column 4 is installed in the working chamber 10, and the upper pressure column 4 is fixedly connected to the arm of the press, an upper pressure plate 2 is fixedly installed at the bottom of the upper pressure column 4, a lower supporting column 3 is fixedly installed at the bottom of the working chamber 10, a lower supporting plate 1 is fixedly installed at the top of the lower supporting column 3, and the ceramic substrate is fixed between the upper pressure plate 2 and the lower supporting plate 1, and the blowing device is sleeved on the outside of the upper pressure plate 2.

[0033] Specifically, the blowing device includes a cone 20, a sleeve 30 and an air inlet pipe 40. The large end of the cone 20 is located at the top, and the small end of the cone 20 is located at the bottom. The small end of the cone 20 is provided with a connecting pipe 22, and the large end of the cone 20 is in a sealed state through a sealing plate 21, and the sealing plate 21 is fixedly connected to the upper pressure column 4. The top of the sleeve 30 is sealed and connected to the sealing plate 21. The sleeve 30 is sleeved on the outer side of the upper pressure plate 2 and the lower support plate 1 of the hot press. The bottom end of the sleeve 30 extends out of the connecting pipe 22. The sleeve 30 is coaxially arranged with the cone 20. The top of the sleeve 30 is provided with a plurality of through holes. The air inlet pipe 40 is connected with the large end of the cone 20, and the gas blown out of the air inlet pipe 40 is located in the tangent direction of the large end of the cone 20.

[0034] In this embodiment, the air inlet pipe 40 blows argon into the cone 20 from the tangential direction of the cone 20, so that the argon will rotate and flow downward along the inner wall of the cone 20, thereby forming a pressure difference with the central part of the cone 20, so that the gas in the sleeve 30 will flow toward the inner wall of the cone 20, and the bottom of the sleeve 30 will draw the argon in the working chamber 10 into the sleeve 30, thereby forming a flow of argon in the sleeve 30, and the flowing argon can more effectively replace the air and other gases generated by the ceramic substrate during the diffusion welding process, including oxygen and water vapor, thereby ensuring that the gas purity in the welding area is high and helping to prevent material oxidation and contamination. At the same time, the flowing argon can help quickly remove the gas released from the surface of the material, such as the gas generated by the degassing of the material at high temperature. As described above, the flowing argon increases the gas exchange rate on the surface of the material, and also accelerates the diffusion rate of the pure copper layer and the tungsten-titanium alloy layer.

[0035] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for manufacturing a multi-layer circuit board by low temperature hot pressing welding, characterized in that: The following steps are involved: S100: Making metal circuit patterns on both sides of a plurality of circuit boards respectively, wherein the metal circuit patterns on opposite sides of any two adjacent circuit boards are arranged in mirror symmetry; S200: performing grinding and polishing on the metal circuit pattern to control surface roughness and flatness; S300: coating a bonding layer on the surface of the metal circuit pattern; S400: After stacking these circuit boards, place them in the working chamber of the hot press for diffusion welding.

2. The method for manufacturing a multi-layer circuit board by low temperature hot pressing welding according to claim 1, characterized in that: In step S100, the metal circuit pattern is manufactured on the circuit board by vacuum plating, chemical plating or electroplating.

3. The method for manufacturing a multi-layer circuit board by low temperature hot pressing welding according to claim 1, characterized in that: In step S100, the metal patterns of the metal circuit patterns of the two opposite circuit boards are respectively a pure copper layer and a tungsten-titanium alloy layer.

4. The method for manufacturing a multi-layer circuit board by low temperature hot pressing welding according to claim 3, characterized in that: The titanium content in the tungsten-titanium alloy layer is 2.2%. The crystal structure of tungsten in the tungsten-titanium alloy is a face-centered cubic structure, and the crystal structure of titanium is a close-packed hexagonal lattice structure.

5. The method for manufacturing a multi-layer circuit board by low temperature hot pressing welding according to claim 4, characterized in that: The bonding layer is a silver-based alloy layer.

6. The method for manufacturing a multi-layer circuit board by low temperature hot pressing welding according to claim 1, characterized in that: In step S400, the temperature in the working chamber of the hot press is 883-890 degrees, the pressure is 400 kilograms per cubic centimeter, the heating rate is 10 degrees to 30 degrees per minute, the insulation time is 10-15 minutes, the cooling rate is 10 degrees to 30 degrees per minute, and the working chamber is filled with argon.

7. A method for manufacturing a multi-layer circuit board by low temperature hot pressing welding according to claim 6, characterized in that: In step S400, the temperature in the working chamber of the hot press is 885 degrees, the pressure is 400 kilograms per cubic centimeter, the heating rate is 15 degrees per minute, the insulation time is 11 minutes, the cooling rate is 15 degrees per minute, and the working chamber is filled with argon.

8. The method for manufacturing a multi-layer circuit board by low temperature hot pressing welding according to claim 1, characterized in that: A blowing device is also provided in the working chamber, and the gas blown out by the blowing device can accelerate the gas flow around the semiconductor in the working chamber.

9. The method for manufacturing a multi-layer circuit board by low temperature hot pressing welding according to claim 8, characterized in that: The blowing device includes a cone, a sleeve and an air intake pipe, the large end of the cone is located at the top, the small end of the cone is located at the bottom, the small end of the cone is provided with a connecting pipe, and the large end of the cone is in a sealed state through a sealing plate, the top of the sleeve is sealed and connected to the sealing plate, the sleeve is sleeved on the outside of the pressure arm of the hot press, the bottom end of the sleeve extends out of the connecting pipe, the sleeve is coaxially arranged with the cone, a plurality of through holes are provided on the top of the sleeve, the air intake pipe is connected with the large end of the cone, and the gas blown out of the air intake pipe is located in the tangent direction of the large end of the cone.

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