A manufacturing method for improving the thermal cycling reliability of copper-clad ceramic substrates

Abstract

This invention discloses a production method for improving the thermal cycling reliability of copper-clad ceramic substrates, belonging to the field of advanced ceramic preparation. This method involves stabilizing the copper-clad ceramic board after circuit forming through thermal cycling before cutting and dividing it into independent carrier board units. This invention improves thermal cycling performance by more than 20%, extending product lifespan.

Description

Technical Field

[0001] This invention relates to the field of advanced ceramics preparation, and in particular to a production method for improving the thermal cycling reliability of copper-clad ceramic substrates. Background Technology

[0002] Copper-clad ceramic substrates are the core interconnect and heat dissipation components of power semiconductor modules. They combine the high insulation, high voltage resistance, and low thermal expansion characteristics of ceramics with the high electrical and thermal conductivity of copper, providing a reliable electrical path and efficient heat dissipation path for high-current, high-voltage, and high-frequency switching devices. Their performance directly affects the power density, thermal management capability, and long-term reliability of the module. Therefore, in high-end application fields such as new energy vehicles, rail transportation, smart grids, wind power generation, and aerospace, they are regarded as one of the key technologies that determine the overall performance and lifespan of the system.

[0003] The existing process steps for copper-clad ceramic substrates are: high-temperature sintering of ceramic substrates for copper cladding → image transfer → etching → cutting → appearance inspection → finished product.

[0004] The excessive internal stress in existing copper-clad ceramic substrates is mainly due to the significant difference in the coefficients of thermal expansion between copper and ceramic. This issue is receiving increasing attention within the industry because excessive internal stress can cause serious damage to multiple aspects, including the substrate's structure, subsequent processing and assembly, and long-term reliability. Specifically, this manifests in the following ways: (1) Direct damage to the substrate's own structure; First, high internal stress easily leads to cracking of the ceramic layer; ceramic materials are inherently brittle and have low fracture toughness. When internal stress forms excessive tensile stress in the ceramic layer and exceeds its tensile strength, cracks will be triggered. Under the superposition of thermal cycling stress, these microcracks will continue to propagate, eventually potentially leading to the overall fracture of the substrate; Second, internal stress can cause substrate warping; the copper layer is mainly under compressive stress, while the ceramic layer is mainly under tensile stress. This imbalance in stress distribution will cause the substrate to bend; Third, internal stress can damage the copper-ceramic interface bond. Stress is highly concentrated at the interface between copper and ceramic, especially at the edges. Once it exceeds the interface bond strength, it will damage the transition layer, thereby affecting the thermal and electrical conductivity of the substrate.

[0005] (2) Interference with subsequent processing and assembly: The warping and deformation of the substrate will seriously interfere with the subsequent processing and assembly process; the warped substrate cannot be accurately attached to components such as chips and heat sinks, which can easily cause welding voids during the welding process and may also cause delamination problems in the molding process, thereby reducing the reliability of packaging and yield.

[0006] (3) Impact on service life and reliability: High internal stress can also shorten the service life of the substrate and even cause early failure. In actual service, the substrate will face harsh conditions such as high and low temperature shocks and high current operation. The initial internal stress will be superimposed with the thermal stress generated by the operating conditions, which will accelerate the fatigue failure process of the material.

[0007] Therefore, it is urgent to reduce the internal stress of copper-clad ceramic substrates. Summary of the Invention

[0008] To address the aforementioned shortcomings, this invention provides a production method for improving the thermal cycling reliability of copper-clad ceramic substrates, thereby extending product lifespan.

[0009] The technical solution is: a production method to improve the thermal cycling reliability of copper-clad ceramic substrates. The method involves stabilizing the copper-clad ceramic substrate after circuit forming through thermal cycling before cutting and dividing it into independent carrier board units.

[0010] Furthermore, the method includes the following steps: S4, thermal cycling stabilization treatment, forming a copper-clad ceramic plate after thermal cycling stabilization treatment, including the following steps: S41, take N copper-clad ceramic plates after circuit forming and place them in the fixture to form a thermal cycling stabilization treatment fixture; S42, The heat cycle stabilization treatment fixture is placed in the internal atmosphere of the treatment for heat cycle stabilization treatment; S5: The copper-clad ceramic plate after the thermal cycling stabilization treatment is cut into several independent carrier plate units. N is a natural number.

[0011] Furthermore, in S42, the conditions for thermal cycling stabilization treatment are as follows: in the first heating stage, the temperature is increased to 80℃~120℃ in 50 min~100 min; in the second heating stage, the temperature is increased to 320℃~380℃ in 75 min~150 min; in the holding stage, the temperature is held for 30 min~100 min; in the first cooling stage, the temperature is reduced to 80℃~120℃ in 30 min~100 min; and then reduced to room temperature in 50 min~100 min.

[0012] Furthermore, in S42, the atmosphere is nitrogen.

[0013] Furthermore, in S31, the composition of the fluoride aqueous solution is: HF 10wt%~30wt%, NH4F 5wt%~15wt%, and the balance is pure water.

[0014] Furthermore, in S41, the thermal cycling stabilization treatment fixture includes N+1 fixture module units, the N copper-clad ceramic plates after circuit forming, and a weight, arranged sequentially from bottom to top as follows: the first fixture module unit, the first copper-clad ceramic plate after circuit forming, the second fixture module unit, the second copper-clad ceramic plate after circuit forming, ... the Nth fixture module unit, the Nth copper-clad ceramic plate after circuit forming, the N+1th fixture module unit, and the weight; Each fixture module unit includes a base plate and two pads connected to the upper surface of the base plate. The thickness of the base plate is denoted as h1, the height of the pads is h2, and a groove is formed between the two pads, where h2>0.

[0015] Furthermore, the range of h2 is 0.2mm to 0.75mm.

[0016] Furthermore, in S32, the weight is a dock block with a weight of 5 kg to 10 kg.

[0017] Furthermore, h1 ranges from 0.5 mm to 2 mm.

[0018] Furthermore, the copper-clad ceramic plate after the circuit is formed is formed through the following steps: S1, High-temperature sintered copper-clad ceramic plate: After stacking the ceramic substrate and oxygen-free copper sheet, it is placed in a high-temperature sintering furnace and directly bonded at 1065℃~1085℃ under a nitrogen protective atmosphere to form a sintered copper-clad ceramic plate. S2, image transfer: photoresist is coated on the copper layer surface of the sintered copper-clad ceramic board, and the copper-clad ceramic board after image transfer is formed by exposure and development. S3, Etching: The substrate after image transfer is immersed in etching solution for etching, and after etching, a copper-clad ceramic board with circuitry is formed.

[0019] Beneficial effects of the invention: This invention involves stabilizing the etched product through thermal cycling to release residual internal stress from the manufacturing process, preventing stress accumulation during subsequent use, improving thermal cycling performance by more than 20%, and extending the product's lifespan. Attached Figure Description

[0020] Figure 1 This is a schematic cross-sectional view of the fixture module unit of the present invention; Figure 2 This is a top view schematic diagram of the fixture module unit of the present invention; Figure 3 This is a schematic diagram of the thermal cycling stabilization treatment fixture in an embodiment of the present invention; Explanation of reference numerals in the attached diagram: 1. Base plate, 2. Pad strip, 3. Groove, 4. Copper-clad ceramic plate after circuit forming, 5. Weight. Detailed Implementation

[0021] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and not for limiting the claims of the present invention.

[0022] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "longitudinal," "lateral," "horizontal," "inner," "outer," "front," "rear," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "open," "installed," "connected," and "communicate" should be interpreted broadly. For example, they can refer to fixed connection, detachable connection, or integral connection; they can refer to direct connection or indirect connection through an intermediate medium; and they can refer to the connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] Unless otherwise specified, all inventions are existing technologies.

[0025] Please refer to Figures 1-2 A fixture module unit includes a base plate 1 and two pads 2 of the same height connected to the upper surface of the base plate 1. The thickness of the base plate 1 is denoted as h1, the height of the pads 2 is h2, and a groove 3 is formed between the two pads 2.

[0026] Example 1 A method for producing a copper-clad ceramic substrate after circuit formation includes the following steps: S1, High-temperature sintered copper-clad ceramic plate: A ceramic substrate (thickness of 0.38 mm) and an oxygen-free copper sheet (thickness of 0.2 mm) are stacked and placed in a high-temperature sintering furnace, and directly bonded at 1065°C under a nitrogen protective atmosphere to form a sintered copper-clad ceramic plate.

[0027] S2, Image Transfer: A layer of photoresist is uniformly coated on the copper layer surface of the sintered copper-clad ceramic substrate. Then, a preset circuit pattern mask is precisely projected onto the photoresist layer using an exposure machine, causing the photosensitive adhesive in the pattern area to undergo a photopolymerization reaction. Subsequently, the photoresist in the unexposed areas is removed with a developer, exposing the copper layer surface that needs to be etched away. The remaining cured photoresist serves as an anti-etching protective layer for subsequent etching processes, forming the copper-clad ceramic substrate after pattern transfer.

[0028] S3, Etching; The substrate after image transfer is immersed in the etching solution. The etching solution reacts with the exposed copper layer in an oxidation-reduction reaction, completely dissolving and removing the copper layer that is not protected by photoresist, leaving only the required circuit pattern, forming the copper-clad ceramic board 4 after circuit formation.

[0029] Example 2 A method for improving the thermal cycling reliability of copper-clad ceramic substrates includes the following steps: S4, thermal cycling stabilization treatment, includes the following steps: S41, randomly select 10 copper-clad ceramic boards 4 after circuit forming in Example 1, and place one copper-clad ceramic board 4 after circuit forming on Figure 1 On the pad 2 of the fixture module unit, another fixture module unit is placed on it, and then another copper-clad ceramic plate 4 with circuit forming is placed on the fixture module unit. This process is repeated until all the copper-clad ceramic plates 4 with circuit forming are placed. Then, another fixture module unit is placed on the last copper-clad ceramic plate 4 with circuit forming, and then a weight 5 is placed on the pad 2 of the fixture module unit to form a thermal cycling stabilization treatment fixture.

[0030] In this embodiment, the dimensions of the base plate 1 are: 138mm (width) * 190mm (length) * 1mm (thickness), and the thickness of the base plate 1 is denoted as h1, i.e., h1 = 1mm. The dimensions of the pad strip 2 are 3mm (width) * 190mm (length) * 0.25mm (thickness), i.e., h2 = 0.25mm. The weight block 5 is a dock block with a weight of 5 kg.

[0031] S42, the heat cycle stabilization treatment fixture is placed in an oven and subjected to low-temperature heat treatment under a nitrogen atmosphere according to the parameters of Example 2 in Table 1.

[0032] S5: Cutting. Using cutting equipment, the large copper-clad ceramic board is divided into independent carrier board units according to the preset shape and size of a single carrier board.

[0033] Example 3 Compared with Example 2, the difference is that in S42, low-temperature heat treatment is performed according to the parameters of Example 3 in Table 1.

[0034] Example 4 Compared with Example 2, the difference is that in S42, low-temperature heat treatment is performed according to the parameters of Example 4 in Table 1.

[0035] Example 5 Compared with Example 2, the difference is that in S42, low-temperature heat treatment is performed according to the parameters of Example 5 in Table 1.

[0036] Example 6 The difference compared to Example 2 is that h2 = 0.5 mm.

[0037] Example 7 Compared with Example 2, the difference is that in S42, low-temperature heat treatment is performed according to the parameters of Example 5 in Table 1.

[0038] Comparative Example 1 The difference compared to Example 2 is that h2=0.

[0039] Comparative Example 2 Compared with Example 2, the difference is that the low-temperature heat treatment process is as follows: the temperature is increased from 25°C to 360°C at a rate of 1.44°C / min, held for 60min, and then cooled to room temperature (25°C) for 300min.

[0040] Comparative Example 3 Compared with Example 2, the difference is that: after randomly selecting 10 copper-clad ceramic boards 4 after circuit forming in Example 1, S4 is not performed, and the cutting process in S5 is directly started.

[0041] Table 1-1 Temperature Parameters for Low-Temperature Heat Treatment (Part 1) Table 1-2 Temperature Parameters for Low-Temperature Heat Treatment (Part Two) Independent carrier plate units (10 independent carrier plate units randomly selected from each example or comparative example) from Examples 2-8 and Comparative Examples 1-3 were subjected to a -55-150℃ thermal cycling test, and the results are shown in Table 2 below.

[0042] Table 2 Thermal Cycling Test As can be seen from Table 2, the specific temperature curve of the present invention has a significant effect on thermal cycling stabilization treatment. After stress release, warpage is significantly reduced and thermal cycling performance is significantly improved.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A production method for improving the thermal cycling reliability of copper-clad ceramic substrates, characterized in that, This method involves stabilizing the copper-clad ceramic board after circuit formation through thermal cycling before cutting and dividing it into independent carrier board units.

2. The production method for improving the thermal cycling reliability of copper-clad ceramic substrates according to claim 1, characterized in that, The method includes the following steps: S4, thermal cycling stabilization treatment, forming a copper-clad ceramic plate after thermal cycling stabilization treatment, including the following steps: S41, take N copper-clad ceramic plates after circuit forming and place them in the fixture to form a thermal cycling stabilization treatment fixture; S42, The heat cycle stabilization treatment fixture is placed in the internal atmosphere of the treatment for heat cycle stabilization treatment; S5: The copper-clad ceramic plate after the thermal cycling stabilization treatment is cut into several independent carrier plate units. N is a natural number.

3. The production method for improving the thermal cycling reliability of copper-clad ceramic substrates according to claim 2, characterized in that, In S42, the conditions for thermal cycling stabilization treatment are as follows: First heating stage, heating to 80℃~120℃ in 50 min~100 min; Second heating stage, heating to 320℃~380℃ in 75 min~150 min; Heating stage, holding for 30 min~100 min; First cooling stage, cooling to 80℃~120℃ in 30 min~100 min; Cooling to room temperature in 50 min~100 min.

4. The production method for improving the thermal cycling reliability of copper-clad ceramic substrates according to claim 2, characterized in that, In S42, the atmosphere is nitrogen.

5. The production method for improving the thermal cycling reliability of copper-clad ceramic substrates according to claim 2, characterized in that, In S31, the composition of the fluoride aqueous solution is: HF 10wt%~30wt%, NH4F 5wt%~15wt%, and the balance is pure water.

6. The production method for improving the thermal cycling reliability of copper-clad ceramic substrates according to claim 3, characterized in that, In S41, the thermal cycling stabilization treatment fixture includes N+1 fixture module units, the N copper-clad ceramic plates after circuit forming, and a weight, arranged sequentially from bottom to top as follows: the first fixture module unit, the first copper-clad ceramic plate after circuit forming, the second fixture module unit, the second copper-clad ceramic plate after circuit forming, ... the Nth fixture module unit, the Nth copper-clad ceramic plate after circuit forming, the N+1th fixture module unit, and the weight; Each fixture module unit includes a base plate and two pads connected to the upper surface of the base plate. The thickness of the base plate is denoted as h1, the height of the pads is h2, and a groove is formed between the two pads, where h2>0.

7. The production method for improving the thermal cycling reliability of copper-clad ceramic substrates according to claim 6, characterized in that, The range of h2 is 0.2mm to 0.75mm.

8. The production method for improving the thermal cycling reliability of copper-clad ceramic substrates according to claim 6, characterized in that, In S32, the weight is a dock block with a weight of 5 kg to 10 kg.

9. The production method for improving the thermal cycling reliability of copper-clad ceramic substrates according to claim 6, characterized in that, The range of h1 is 0.5mm to 2mm.

10. The production method for improving the thermal cycling reliability of copper-clad ceramic substrates according to any one of claims 1-9, characterized in that, The copper-clad ceramic plate after the circuit is formed is formed through the following steps: S1, High-temperature sintered copper-clad ceramic plate: After stacking the ceramic substrate and oxygen-free copper sheet, it is placed in a high-temperature sintering furnace and directly bonded at 1065℃~1085℃ under a nitrogen protective atmosphere to form a sintered copper-clad ceramic plate. S2, image transfer: photoresist is coated on the copper layer surface of the sintered copper-clad ceramic board, and the copper-clad ceramic board after image transfer is formed by exposure and development. S3, Etching: The substrate after image transfer is immersed in etching solution for etching, and after etching, a copper-clad ceramic board with circuitry is formed.

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