AMB ceramic substrate warping control method based on double-hardness copper layer regulation and control

Abstract

The invention discloses an AMB ceramic substrate warping control method based on double-hardness copper layer regulation and control, which comprises the following steps: copper sheet grading pretreatment: carrying out annealing treatment on an oxygen-free copper sheet to obtain two copper materials with different grain sizes and hardness, and respectively marking the same kind of copper materials before annealing treatment as X copper and Z copper; hardness-differentiated copper-clad brazing is conducted, specifically, X copper and Z copper are coated on the two faces of the ceramic substrate respectively, brazing connection is conducted, the X copper is applied to the pattern face side, and the Z copper is applied to the non-pattern face side; and carrying out graphical processing to obtain the AMB ceramic substrate of which the residual copper rate of the graphical surface is higher than that of the non-graphical surface. The warping degree of the AMB ceramic substrate product is reduced, the qualified rate and the yield of the product are improved, and the cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of AMB product processing technology, specifically to a method for controlling the warpage of AMB ceramic substrates based on dual-hardness copper layer modulation. Background Technology

[0002] AMB ceramic substrates are widely used in the packaging of power devices such as IGBTs and SiC modules due to their advantages such as high thermal conductivity and high insulation.

[0003] However, during the AMB manufacturing process, after the AMB product is patterned, there will be a difference in the residual copper content on both sides of the ceramic substrate. Generally, the residual copper content is lower on the patterned side and higher on the non-patterned side. In this case, the ceramic substrate is subjected to an unbalanced tension from the copper sheets on both sides. The side with a higher residual copper content will exert a greater tension on the ceramic substrate than the side with a lower residual copper content, resulting in substrate warping. Excessive substrate warping will affect the user experience.

[0004] Therefore, there is an urgent need for a method to control the warpage of AMB ceramic substrates without sacrificing the performance of the copper layer. Summary of the Invention

[0005] The purpose of this invention is to provide a warpage control method for AMB ceramic substrates based on dual-hardness copper layers. By applying X copper and Z copper with different hardness and different grain sizes to the patterned and non-patterned surfaces of the ceramic substrate after copper annealing, the patterned surface of the AMB ceramic substrate can resist the tensile force of the non-patterned surface on the substrate, thereby controlling the warpage.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following solution: A method for controlling the warpage of AMB ceramic substrates based on dual-hardness copper layer modulation includes the following steps: (1) Copper sheet grading pretreatment: Oxygen-free copper sheets are annealed to obtain two types of copper materials with different grain sizes and hardness. The copper materials of the same type before annealing are marked as X copper and Z copper respectively. (2) Hardness differential copper plating brazing: X copper and Z copper are respectively coated on both sides of the ceramic substrate and brazed together, wherein X copper is applied to the patterned side and Z copper is applied to the non-patterned side. (3) Patterning process: AMB ceramic substrates with a higher residual copper ratio on the patterned surface than on the non-patterned surface are obtained.

[0007] The purpose of step (1) is to anneal different types of oxygen-free copper sheets, thereby selecting the same type of copper material that has not undergone annealing treatment and labeling them as X copper and Z copper according to the grain size and hardness. At the same time, X copper and Z copper before annealing treatment are selected to be coated on the patterned and non-patterned surfaces of the ceramic substrate, so that after brazing, the hardness of X copper and Z copper changes, and finally the residual copper rate of the patterned surface is higher than that of the non-patterned surface, thus controlling the warping degree of the AMB ceramic substrate.

[0008] Further, the annealing process described in step (1) includes: S10. Place the oxygen-free copper sheet in a vacuum sintering furnace with a vacuum degree ≤1×10⁻²Pa and hold it at the first temperature range of 800~900℃ for 20~40min; S11. After cooling to room temperature, the copper sheets were screened for grain size and hardness tests.

[0009] Furthermore, the X copper is a copper material with a grain size of <100μm and a Vickers hardness of 45~55HV; the Z copper is a copper material with a grain size of <400μm and a Vickers hardness of 35~45HV.

[0010] Furthermore, the brazing process described in step (2) includes two stages of heating: S20. Under a vacuum degree of 10 ⁻3 ~10 ⁻4 When Pa is reached, start heating, first raise the temperature to 100~450℃, then hold the temperature in the second temperature range for 40~60 minutes. S21. Continue heating to the third temperature range of 800~900℃ and hold for 20~40 minutes. After holding, cool under partial pressure.

[0011] Furthermore, the vacuum degree during the heating and heat preservation is ≤5×10⁻²Pa.

[0012] Furthermore, the heating rate in the second temperature range is 5~10℃ / min, and the heating rate in the third temperature range is 15~20℃ / min.

[0013] Furthermore, during partial pressure cooling, nitrogen gas is introduced to a furnace pressure of 5000 Pa, and the cooling rate is 5~10℃ / min.

[0014] Furthermore, the oxygen-free copper sheet has a thickness of 0.4~1.0 mm, an oxygen content of ≤10 ppm, and a purity of ≥99.99%.

[0015] Furthermore, the ceramic substrate is made of Al2O3, AlN, or Si3N4 material, with a thickness of 0.25~1.0mm.

[0016] The beneficial effects of this invention are as follows: This invention is an AMB ceramic substrate warpage control method based on dual-hardness copper layer regulation. Multiple oxygen-free copper sheets are pre-annealed to determine their grain size and hardness parameters. Copper sheets of the same type that have not undergone annealing are labeled as X copper and Z copper. The patterned surface of the ceramic substrate is covered with the harder X copper, and the non-patterned surface is covered with the softer Z copper. After sequential brazing and patterning, the copper sheet on the patterned surface has greater hardness to resist the tensile force on the non-patterned side. Therefore, by controlling the hardness of the copper sheets after sintering, the warpage of the AMB ceramic substrate product is reduced, improving the product yield and pass rate, and reducing costs. Attached Figure Description

[0017] Figure 1 This is a thermal warpage hysteresis curve diagram of Embodiment 2 of the present invention; Figure 2 This is a comparative thermal warpage hysteresis curve; Figure 3 This is a photograph of the brazed object in Embodiment 2 of the present invention; Figure 4 This is a graphical representation of the physical object in Embodiment 2 of the present invention. Detailed Implementation

[0018] 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 only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0020] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0021] Furthermore, for clarity and brevity, descriptions of well-known structures, functions, and configurations may have been omitted. Those skilled in the art will recognize that various changes and modifications can be made to the examples described herein without departing from the spirit and scope of this disclosure.

[0022] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0023] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0024] Example 1: Grading and Pretreatment of Copper Sheets Select multiple oxygen-free copper sheets with a thickness of 0.4~1.0mm, an oxygen content ≤10ppm, and a purity ≥99.99%, and set them aside for use; Place the oxygen-free copper sheet in a vacuum sintering furnace with a vacuum degree ≤1×10⁻²Pa and hold it at the first temperature range of 800~900℃ for 20~40min; After cooling to room temperature, the copper sheets were screened for grain size and hardness was tested using a hardness tester. Two types of copper materials with different grain sizes and hardness were obtained. The copper material with a grain size <100μm and a Vickers hardness of 45~55HV was marked as X copper, and the copper material with a grain size <400μm and a Vickers hardness of 35~45HV was marked as Table 1.

[0025] Table 1. Grain size and Vickers hardness before and after annealing It should be noted that here, the copper material before and after annealing is measured through annealing treatment. Based on the grain size and hardness value, the copper material that has not undergone annealing treatment is marked as X copper and Z copper, and then subjected to subsequent copper plating, brazing and patterning processing.

[0026] Example 2: A method for controlling the warpage of AMB ceramic substrates based on dual-hardness copper layer modulation Based on Example 1, after selecting X copper and Z copper that meet the requirements, X copper and Z copper of the same hardness and without annealing treatment are selected for later use. The following steps are performed: Differentiated hardness copper plating brazing: X copper and Z copper are respectively coated on both sides of the ceramic substrate and brazed together, wherein X copper is applied to the patterned side and Z copper is applied to the non-patterned side.

[0027] (a) The brazing process includes two stages of heating: 1) In a vacuum of 10⁻ 3 ~10⁻ 4 When Pa, start heating, first raise the temperature to 100~450℃, then hold the temperature in the second temperature range for 40~60min, with a heating rate of 5~10℃ / min; 2) Continue heating to the third temperature range of 800~900℃ and hold for 20~40 minutes. The heating rate is 15~20℃ / min. After holding, perform partial pressure cooling. When performing partial pressure cooling, purge nitrogen to the furnace pressure of 5000Pa and cool at a rate of 5~10℃ / min.

[0028] The vacuum degree during heating and heat preservation is ≤5×10⁻²Pa.

[0029] It should be noted that the ceramic substrate here is made of Al2O3, AlN or Si3N4 material, with a thickness of 0.25~1.0mm.

[0030] (ii) Patterning process: The substrate with X copper on the patterned side and Z copper on the non-patterned side is patterned to obtain an AMB ceramic substrate with a higher residual copper ratio on the patterned side than on the non-patterned side.

[0031] Comparative Example The method of this comparative example is consistent with that of Example 2. The difference is that the comparative example uses copper with normal hardness after annealing in Example 1, namely Z copper. Z copper is applied to the patterned and non-patterned surfaces of the ceramic substrate for brazing and patterning.

[0032] In addition, performance tests were performed on six AMB ceramic substrates after brazing in Example 2 and the comparative example, including warpage value, thermal warpage, peel strength, and thermal cycling life. (See attached figures.) Figure 1 , Figure 3 And Table 2.

[0033] Table 2. Performance data comparison between Example 2 and the comparative example. As shown in Table 2, in Example 2, the patterned surface uses X copper with high hardness, and the non-patterned surface uses Z copper with low hardness. The comparative example uses Z copper with the same hardness. After brazing and patterning, the average warpage value in Example 2 is 24.85% lower than that in the comparative example, making each warpage value significantly lower than that in the comparative example. At the same time, the average peel strength is 5.52% lower than that in the comparative example, and the peel strength is basically the same. In the hot and cold cycling, there is no significant difference between Example 2 and the comparative example.

[0034] The thermal warpage hysteresis curves in Example 2 and the comparative example are shown below. Figure 1 and Figure 2 In Example 2, the maximum value does not exceed 300 μm, while the thermal warpage of the comparative example is 300~500 μm. This indicates that the warpage performance of the AMB ceramic substrate with dual hardness copper layer control in Example 2 is significantly better than that of the comparative example in a heated environment. Figure 3 and Figure 4 The images shown are actual pictures of the objects after brazing and graphic processing in Example 2.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for controlling the warpage of AMB ceramic substrates based on dual-hardness copper layer modulation, characterized in that, Includes the following steps: (1) Copper sheet grading pretreatment: Oxygen-free copper sheets are annealed to obtain two types of copper materials with different grain sizes and hardness. The copper materials of the same type before annealing are marked as X copper and Z copper respectively. (2) Hardness differential copper plating brazing: X copper and Z copper are respectively coated on both sides of the ceramic substrate and brazed together, wherein X copper is applied to the patterned side and Z copper is applied to the non-patterned side. (3) Patterning process: AMB ceramic substrates with a higher residual copper ratio on the patterned surface than on the non-patterned surface are obtained.

2. The AMB ceramic substrate warpage control method based on dual-hardness copper layer modulation according to claim 1, characterized in that, The annealing process described in step (1) includes: S10. Place the oxygen-free copper sheet in a vacuum with a degree ≤1×10⁻⁶. -2 In a vacuum sintering furnace with Pa, the temperature is held in the first temperature range of 800~900℃ for 20~40 minutes. S11. After cooling to room temperature, the copper sheets were screened for grain size and hardness tests.

3. The method for controlling the warpage of AMB ceramic substrates based on dual-hardness copper layer modulation according to claim 1, characterized in that, The X copper is a copper material with a grain size of <100μm and a Vickers hardness of 45~55HV; the Z copper is a copper material with a grain size of <400μm and a Vickers hardness of 35~45HV.

4. The AMB ceramic substrate warpage control method based on dual-hardness copper layer modulation according to claim 1, characterized in that, The brazing process described in step (2) includes two stages of heating: S20. Under a vacuum degree of 10 -3 ~10 -4 When Pa is reached, start heating, first raise the temperature to 100~450℃, then hold the temperature in the second temperature range for 40~60 minutes. S21. Continue heating to the third temperature range of 800~900℃ and hold for 20~40 minutes. After holding, cool under partial pressure.

5. The AMB ceramic substrate warpage control method based on dual-hardness copper layer modulation according to claim 4, characterized in that, The vacuum degree during heating and heat preservation is ≤5×10⁻⁵. -2 Pa.

6. The AMB ceramic substrate warpage control method based on dual-hardness copper layer modulation according to claim 4, characterized in that, The heating rate in the second temperature range is 5~10℃ / min, and the heating rate in the third temperature range is 15~20℃ / min.

7. The AMB ceramic substrate warpage control method based on dual-hardness copper layer modulation according to claim 4, characterized in that, During partial pressure cooling, nitrogen is introduced to a furnace pressure of 5000 Pa, and the cooling rate is 5~10℃ / min.

8. The AMB ceramic substrate warpage control method based on dual-hardness copper layer regulation according to claim 4, characterized in that, The oxygen-free copper sheet has a thickness of 0.4mm to 1.0mm, an oxygen content of ≤10ppm, and a purity of ≥99.99%.

9. The AMB ceramic substrate warpage control method based on dual-hardness copper layer modulation according to claim 4, characterized in that, The ceramic substrate is made of Al2O3, AlN or Si3N4 material, with a thickness of 0.25mm to 1.0mm.

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