A rolling method of a molybdenum copper alloy heat sink for electronic packaging

Abstract

The present application relates to a kind of molybdenum copper alloy heat sink for electronic packaging rolling method, the rolling method includes the following steps: (1) molybdenum copper alloy blank is carried out first one-way rolling treatment, obtains after rolling blank;(2) the after rolling blank of step (1) obtained is carried out second one-way rolling treatment, obtains molybdenum copper alloy heat sink.The rolling method provided by the present application can not only solve the cracking problem in the rolling process of molybdenum copper alloy, but also can reduce the linear expansion coefficient of alloy material, the linear expansion coefficient of product changes with temperature is more stable, meet the subsequent packaging requirements of heat sink material, effectively improve the operating efficiency and service life of chip.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging materials technology, and specifically to a rolling method for a molybdenum-copper alloy heat sink for electronic packaging. Background Technology

[0002] With the rapid development of very large-scale integrated circuits, the integration density of semiconductor chips is increasing, and the required operating speed is also accelerating. Therefore, improving the efficient heat dissipation of chips is currently a key research area. Molybdenum-copper alloy is a "pseudo-alloy" composed of two immiscible metals, molybdenum and copper, typically prepared from molybdenum and copper powders using powder metallurgy. Molybdenum-copper alloy possesses the high strength, hardness, and low coefficient of thermal expansion of pure molybdenum, as well as the good electrical and thermal conductivity of copper. Therefore, it exhibits excellent comprehensive properties such as high-temperature resistance, electrical and thermal conductivity, and ease of processing. In the field of electronic packaging, it can effectively conduct heat from electronic devices, helping to cool IGBT modules, LED chips, and other products, thereby improving chip operating efficiency and extending their lifespan.

[0003] Currently, molybdenum-copper alloys used in electronic packaging heat sinks are typically prepared into blanks using melt infiltration or high-temperature liquid-phase sintering, followed by conventional biaxial alternating hot rolling to the target thickness. However, because molybdenum-copper alloys are "pseudo-alloys" composed of two immiscible metals, molybdenum and copper, they are extremely prone to cracking during conventional biaxial alternating hot rolling. Furthermore, the coefficient of linear expansion of products prepared by conventional biaxial alternating hot rolling varies significantly and unevenly with increasing temperature, which is detrimental to subsequent packaging of the heat sink material, easily leading to packaging failure and ultimately severely impacting the chip's operating efficiency and lifespan.

[0004] CN102489508A discloses a cross-rolling method for molybdenum-copper alloy foil. A sintered molybdenum-copper alloy slab with a thickness of 0.8-4 mm is subjected to multi-pass cold rolling. When the rolling deformation is 60-90%, 90° cross-rolling is performed, and the deformation is still controlled within 60-90%. The cross-rolled foil is then annealed at a temperature of 600-850℃. However, the cross-rolling method described above not only easily leads to foil cracking but also results in an unstable coefficient of linear expansion, which is detrimental to the subsequent encapsulation of heat sink materials.

[0005] CN102873095A discloses a method for preparing molybdenum-copper alloy foil, comprising: (1) preparing a sintered molybdenum-copper alloy billet using conventional methods; (2) preheating the molybdenum-copper alloy billet to 40-300℃ and holding it at that temperature for 5-30 minutes; (3) preheating the rolls of a rolling mill to 40-80℃; and (4) rolling the preheated molybdenum-copper alloy billet on a rolling mill to obtain molybdenum-copper alloy foil. Although the above method can produce molybdenum-copper alloy foil, it cannot achieve the precision required for packaging materials, and it also suffers from the problem that the coefficient of linear expansion changes significantly with increasing temperature.

[0006] Therefore, providing a rolling method for molybdenum-copper alloy heat sinks for electronic packaging is of great significance. Summary of the Invention

[0007] To address the above problems, the present invention aims to provide a rolling method for molybdenum-copper alloy heat sinks for electronic packaging. Compared with the prior art, the rolling method provided by the present invention can not only solve the cracking problem in the rolling process of molybdenum-copper alloy, but also stabilize the linear expansion coefficient of the alloy material, meet the subsequent packaging requirements of the heat sink material, and effectively improve the operating efficiency and service life of the chip.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a rolling method for a molybdenum-copper alloy heat sink for electronic packaging, the rolling method comprising the following steps:

[0010] (1) The molybdenum-copper alloy billet is subjected to a first unidirectional rolling process to obtain the rolled billet;

[0011] (2) The rolled billet obtained in step (1) is subjected to a second unidirectional rolling process to obtain a molybdenum-copper alloy heat sink.

[0012] The rolling method provided by this invention controls the precision of heat sink processing by performing two rolling processes. First, a first unidirectional rolling process is used for rough rolling to bring the billet thickness close to the target thickness. Then, a second unidirectional rolling process is used for finish rolling to bring the billet thickness to the target thickness while maintaining a small tolerance, thus enabling the heat sink to meet the chip packaging requirements. On the other hand, by controlling each rolling process to be unidirectional, the billet maintains a unidirectional fibrous structure at the microscopic level, and the coordinated deformation of the molybdenum and copper alloys is regulated. Compared with existing bidirectional rolling or cross rolling methods, this invention can effectively prevent billet cracking and prevent the coefficient of linear expansion of the alloy from changing significantly with increasing temperature by performing two unidirectional rolling processes. This is beneficial for the subsequent packaging of heat sink materials and improves the operating efficiency and service life of the chip.

[0013] Preferably, the mass percentage of copper in the molybdenum-copper alloy billet in step (1) is 5-40%, for example, it can be 5%, 15%, 20%, 25%, 30%, 35% or 40%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] Preferably, the thickness of the molybdenum-copper alloy billet in step (1) is 15-20 mm, for example, it can be 15 mm, 16 mm, 17 mm, 18 mm, 19 mm or 20 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, step (1) the first unidirectional rolling process includes at least one hot rolling process, such as one, two, three, four or five passes, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] Preferably, the hot rolling process is performed in the same direction for each pass.

[0017] In this invention, controlling the first unidirectional rolling process includes at least one hot rolling process, and controlling the direction of the hot rolling process to be the same, can maintain the coordinated deformation of the molybdenum-copper alloy at high temperature, achieve a uniform unidirectional fibrous structure, thereby preventing cracking and an increase in the coefficient of linear expansion.

[0018] Preferably, the amount of pressure applied in each pass of the hot rolling process in step (1) is 0.5-1 mm, for example, it can be 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] In this invention, it is preferable to control the amount of heat reduction during hot rolling within a specific range, which can ensure that the thickness of the billet meets the target requirements while allowing the two metals, molybdenum and copper, to deform more harmoniously and prevent the coefficient of linear expansion from changing too much with increasing temperature.

[0020] Preferably, the hot rolling temperature is 320-350℃, for example, it can be 320℃, 325℃, 330℃, 335℃, 340℃, 345℃ or 350℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] In this invention, it is preferable to control the temperature of the hot rolling process within a specific range. On the one hand, this can achieve a good rolling effect and prevent the billet from cracking; on the other hand, it can avoid copper volatilization and ensure that the proportion of molybdenum-copper alloy meets the packaging requirements.

[0022] Preferably, after each hot rolling process in step (1), a tempering process is performed.

[0023] Preferably, the tempering temperature is 320-350℃, for example, it can be 320℃, 325℃, 330℃, 335℃, 340℃, 345℃ or 350℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] In this invention, it is preferable to perform tempering after each hot rolling process, and control the tempering temperature within a specific range to avoid the billet cooling between adjacent unidirectional hot rolling processes, which could lead to billet cracking or a large change in the coefficient of linear expansion with increasing temperature.

[0025] Preferably, the endpoint of the first unidirectional rolling process in step (1) is: the thickness of the billet is greater than the target thickness, and the difference between the two is 0.3-0.5 mm, for example, it can be 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm or 0.5 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, step (2) the second unidirectional rolling process includes at least one cold rolling process, such as one, two, three, four or five passes, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the rolling direction of the second unidirectional rolling process is the same as that of the first unidirectional rolling process.

[0028] Preferably, the direction of each cold rolling process is the same.

[0029] In this invention, by controlling the rolling direction of the second unidirectional rolling process to be the same as that of the first unidirectional rolling process, and the direction of each cold rolling process to be the same, the microstructure of the billet can be maintained as unidirectional fibrous, thus avoiding a large change in the linear expansion coefficient of the billet with increasing temperature.

[0030] Preferably, the reduction in pressure for each cold rolling pass is 0.01-0.02 mm, for example, it can be 0.01 mm, 0.012 mm, 0.014 mm, 0.016 mm, 0.018 mm or 0.02 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] In this invention, it is preferable to control the amount of cold rolling within a specific range, which can coordinate the deformation of the two alloys, molybdenum and copper, and prevent the coefficient of linear expansion from changing too much with increasing temperature.

[0032] Preferably, the temperature of the cold rolling process is 10-40℃, for example, it can be 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the endpoint of the second unidirectional rolling process in step (2) is: the tolerance between the thickness of the billet and the target thickness is ±0.05mm, for example, it can be ±0.01mm, ±0.02mm, ±0.03mm, ±0.04mm or ±0.05mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] As a preferred embodiment of the present invention, the rolling method includes the following steps:

[0035] (1) The molybdenum-copper alloy billet is hot rolled at 320-350℃ for at least one pass, with the direction of each hot rolling pass being the same and the reduction amount of each hot rolling pass being 0.5-1mm. After each hot rolling pass, the billet is tempered at 320-350℃ until the thickness of the billet is greater than the target thickness and the difference between the two is 0.3-0.5mm, to obtain the rolled billet; the mass percentage of copper in the molybdenum-copper alloy billet is 5-40%, and the thickness of the molybdenum-copper alloy billet is 15-20mm.

[0036] (2) The rolled billet obtained in step (1) is subjected to at least one cold rolling process at 10-40°C. The direction of the cold rolling process is the same as that of the hot rolling process. The direction of the cold rolling process is the same for each pass. The amount of cold rolling is 0.01-0.02 mm for each pass until the thickness of the billet is within ±0.05 mm of the target thickness, thus obtaining a molybdenum-copper alloy heat sink.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The rolling method provided by this invention, through a first unidirectional rolling process and a second unidirectional rolling process, can control the microstructure of molybdenum-copper alloy to be unidirectional fibrous, while simultaneously regulating the coordinated deformation of the two metals, molybdenum and copper. This effectively solves the cracking problem during the rolling process of molybdenum-copper alloy, stabilizes the linear expansion coefficient of the alloy material, and under optimal conditions, the change in the linear expansion coefficient between the 20-100℃ range and the 20-800℃ range is ≤0.03℃. -1 This meets the subsequent packaging requirements of heat sink materials, effectively improving the chip's operating efficiency and lifespan. Detailed Implementation

[0039] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0040] Example 1

[0041] This embodiment provides a rolling method for a molybdenum-copper alloy heat sink for electronic packaging, the rolling method comprising the following steps:

[0042] (1) The molybdenum-copper alloy billet is hot rolled at 335°C for 20 passes. The direction of each hot rolling pass is the same, and the reduction of each hot rolling pass is 0.74 mm. After each hot rolling pass, the billet is tempered at 335°C until the thickness of the billet is greater than the target thickness and the difference between the two is 0.4 mm, to obtain the rolled billet. The mass percentage of copper in the molybdenum-copper alloy billet is 20%, and the thickness of the molybdenum-copper alloy billet is 17 mm.

[0043] (2) The rolled billet obtained in step (1) is subjected to 27 cold rolling passes at 25°C. The direction of the cold rolling is the same as that of the hot rolling. The direction of the cold rolling is the same for each pass. The amount of cold rolling is 0.015 mm for each pass until the thickness of the billet is within ±0.05 mm of the target thickness. The target thickness is 1.8 mm, thus obtaining a molybdenum-copper alloy heat sink.

[0044] Example 2

[0045] This embodiment provides a rolling method for a molybdenum-copper alloy heat sink for electronic packaging, the rolling method comprising the following steps:

[0046] (1) The molybdenum-copper alloy billet is hot rolled at 320°C for 26 passes. The direction of each hot rolling pass is the same, and the reduction of each hot rolling pass is 0.5 mm. After each hot rolling pass, the billet is tempered at 320°C until the thickness of the billet is greater than the target thickness and the difference between the two is 0.3 mm, to obtain the rolled billet. The mass percentage of copper in the molybdenum-copper alloy billet is 5%, and the thickness of the molybdenum-copper alloy billet is 15 mm.

[0047] (2) The rolled billet obtained in step (1) is subjected to 30 cold rolling passes at 15°C. The direction of the cold rolling is the same as that of the hot rolling. The direction of the cold rolling is the same for each pass. The amount of cold rolling is 0.01 mm for each pass until the thickness of the billet is within ±0.05 mm of the target thickness. The target thickness is 1.7 mm, thus obtaining a molybdenum-copper alloy heat sink.

[0048] Example 3

[0049] This embodiment provides a rolling method for a molybdenum-copper alloy heat sink for electronic packaging, the rolling method comprising the following steps:

[0050] (1) The molybdenum-copper alloy billet is hot rolled at 350°C for 35 passes, with the direction of each hot rolling pass being the same and the reduction amount of each hot rolling pass being 0.5 mm. After each hot rolling pass, it is tempered at 350°C until the thickness of the billet is greater than the target thickness and the difference between the two is 0.5 mm, to obtain the rolled billet; the mass percentage of copper in the molybdenum-copper alloy billet is 40%, and the thickness of the molybdenum-copper alloy billet is 20 mm.

[0051] (2) The rolled billet obtained in step (1) is subjected to 25 cold rolling passes at 35°C. The direction of the cold rolling is the same as that of the hot rolling. The direction of the cold rolling is the same for each pass. The amount of cold rolling is 0.02 mm for each pass until the thickness of the billet is within ±0.05 mm of the target thickness. The target thickness is 2 mm, thus obtaining a molybdenum-copper alloy heat sink.

[0052] Example 4

[0053] This embodiment provides a rolling method for a molybdenum-copper alloy heat sink for electronic packaging. The only difference from Embodiment 1 is that the reduction amount of each hot rolling process is 3.7 mm, and a total of 4 hot rolling processes are performed.

[0054] Example 5

[0055] This embodiment provides a rolling method for a molybdenum-copper alloy heat sink for electronic packaging. The only difference from Embodiment 1 is that the reduction amount of each cold rolling process is 0.05 mm, and a total of 8 cold rolling processes are performed.

[0056] Example 6

[0057] This embodiment provides a rolling method for a molybdenum-copper alloy heat sink for electronic packaging. The only difference from Embodiment 1 is that the temperature of each hot rolling process is 400°C.

[0058] Comparative Example 1

[0059] This comparative example provides a rolling method for a molybdenum-copper alloy heat sink for electronic packaging. The only difference from Example 1 is that the hot rolling process in each pass of step (1) is bidirectional rolling.

[0060] Comparative Example 2

[0061] This comparative example provides a rolling method for a molybdenum-copper alloy heat sink for electronic packaging. The only difference from Example 1 is that the cold rolling process in each pass of step (2) is bidirectional rolling.

[0062] The molybdenum-copper alloy heat sinks prepared in Examples 1-6 and Comparative Examples 1-2 were subjected to full inspection to observe whether there were cracks. The results are shown in Table 1.

[0063] The coefficient of linear expansion of the molybdenum-copper alloy heat sinks prepared in Examples 1-6 and Comparative Examples 1-2 was tested using a dynamic thermal analyzer, and the results are shown in Table 1.

[0064] Table 1

[0065]

[0066] The following points can be observed from the data in Table 1:

[0067] (1) As can be seen from the data in Examples 1-3, under preferred conditions, the rolling method provided by this invention can make the linear expansion coefficient of the product tend to stabilize as the temperature increases, with the change in the linear expansion coefficient between the 20-100℃ range and the 20-800℃ range being ≤0.03℃. -1 And it does not crack.

[0068] (2) As can be seen from the comparison between Example 1 and Examples 4-5, the shrinkage amount of hot rolling in Example 1 is 0.74 mm and the shrinkage amount of cold rolling is 0.015 mm. Compared with the shrinkage amount of 3.7 mm for hot rolling and 0.05 mm for cold rolling in Example 4, the linear expansion coefficient of Example 1 is more stable as the temperature increases, and product cracking can be effectively avoided. It can be seen that the present invention preferably controls the shrinkage amount of hot rolling and cold rolling within a specific range, which can improve the yield of the product, stabilize the linear expansion coefficient of the product, and is more conducive to subsequent packaging.

[0069] (3) As can be seen from the comparison between Example 1 and Example 6, the hot rolling temperature in Example 1 is 335°C, which is higher than the hot rolling temperature in Example 6 of 400°C. The linear expansion coefficient of the product in Example 1 is more stable as the temperature increases. Therefore, it can be seen that the present invention preferably controls the hot rolling temperature within a specific range, which can stabilize the linear expansion coefficient of the product and is more conducive to subsequent packaging.

[0070] (4) As can be seen from the comparison between Example 1 and Comparative Example 1-2, the linear expansion coefficient of the product obtained by the present invention is more stable than that of the product obtained by the bidirectional rolling process of Comparative Example 1-2, which effectively avoids the cracking problem of the product and is more conducive to subsequent packaging.

[0071] In summary, the rolling method provided by this invention can not only solve the cracking problem in the rolling process of molybdenum-copper alloy, but also stabilize the linear expansion coefficient of the alloy material, meet the subsequent packaging requirements of heat sink materials, and effectively improve the operating efficiency and service life of the chip.

[0072] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A rolling method for a molybdenum-copper alloy heat sink for electronic packages, characterized by, The rolling method includes the following steps: (1) The molybdenum-copper alloy billet is subjected to a first unidirectional rolling process to obtain the rolled billet; (2) The rolled billet obtained in step (1) is subjected to a second unidirectional rolling process to obtain a molybdenum-copper alloy heat sink; Step (1) The first unidirectional rolling process includes at least one hot rolling process; each hot rolling process is followed by a tempering process; the tempering process temperature is 320-335℃; the hot rolling process in each pass is in the same direction; the hot rolling process temperature is 320-335℃. In step (1), the reduction in pressure for each hot rolling pass is 0.5-1 mm; Step (2) The second unidirectional rolling process includes at least one cold rolling pass; the rolling direction of the second unidirectional rolling process is the same as that of the first unidirectional rolling process; the direction of each cold rolling pass is the same; the temperature of the cold rolling process is 15-25℃; The reduction in cold rolling for each pass is 0.01-0.02 mm.

2. The rolling method of the molybdenum-copper alloy heat sink for electronic packaging according to claim 1, characterized by, The mass percentage of copper in the molybdenum-copper alloy billet described in step (1) is 5-40%.

3. The rolling method of the molybdenum-copper alloy heat sink for electronic packaging according to claim 2, characterized by, The thickness of the molybdenum-copper alloy billet in step (1) is 15-20 mm.

4. The rolling method of the molybdenum-copper alloy heat sink for electronic packaging according to claim 1, characterized by, Step (1) The endpoint of the first unidirectional rolling process is: the thickness of the billet is greater than the target thickness, and the difference between the two is 0.3-0.5 mm.

5. The rolling method of the molybdenum-copper alloy heat sink for electronic packaging according to claim 1, characterized by, Step (2) The endpoint of the second unidirectional rolling process is: the tolerance between the thickness of the billet and the target thickness is ±0.05mm.

6. The rolling method according to claim 1, characterized in that, The rolling method includes the following steps: (1) The molybdenum-copper alloy billet is hot rolled at 320-335℃ for at least one pass, with the direction of each hot rolling pass being the same and the reduction amount of each hot rolling pass being 0.5-1mm. After each hot rolling pass, the billet is tempered at 320-335℃ until the thickness of the billet is greater than the target thickness and the difference between the two is 0.3-0.5mm, to obtain the rolled billet. The mass percentage of copper in the molybdenum-copper alloy billet is 5-40%, and the thickness of the molybdenum-copper alloy billet is 15-20mm. (2) The rolled billet obtained in step (1) is subjected to at least one cold rolling process at 15-25°C. The direction of the cold rolling process is the same as that of the hot rolling process. The direction of the cold rolling process is the same for each pass. The amount of cold rolling is 0.01-0.02 mm for each pass until the thickness of the billet is within ±0.05 mm of the target thickness, thus obtaining a molybdenum-copper alloy heat sink.

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