Laser welding method and system for Kovar alloy and copper

Abstract

Embodiments of the present invention disclose a laser welding method and system for Kovar alloy and copper. The method includes the following steps: Step 1: Cleaning the surfaces of the Kovar alloy and copper to be welded, placing the Kovar alloy and copper in close contact and securing them, and determining the welding path and weld depth; Step 2: Driving the laser in pulsed or continuous laser mode to weld along the welding path at a preset welding speed, melting the Kovar alloy and copper along the welding path, and adhering the Kovar alloy to the copper. This method offers advantages such as efficient energy transmission, precise control, excellent welding quality, and wide applicability. It can significantly improve welding efficiency and product quality, and is suitable for applications in electronic packaging, manufacturing, and other fields.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic device processing, and in particular to a laser welding method and system for Kovar alloy and copper. Background Art

[0002] Welding Kovar alloy to copper has important applications in electronic packaging and manufacturing. Kovar alloy, due to its excellent thermal expansion coefficient matching, is widely used in glass and ceramic packaging. Copper, on the other hand, is widely used in electrical and electronic equipment due to its excellent electrical and thermal conductivity. However, due to the significant differences in the physical and chemical properties of these two materials, welding them presents many challenges, such as stress and cracking in the heat-affected zone (HAZ) and brittleness caused by interfacial reactions. Therefore, finding an efficient and reliable welding method is crucial for improving production efficiency and product quality. Summary of the Invention

[0003] The technical problem to be solved by the embodiments of the present invention is to provide a laser welding method and system for Kovar alloy and copper to improve welding quality and welding efficiency.

[0004] In order to solve the above technical problems, an embodiment of the present invention provides a laser welding method for Kovar alloy and copper, comprising:

[0005] Step 1: Clean the surfaces of the Kovar alloy and copper to be welded, place the Kovar alloy and copper close together and secure them, and determine the welding path and weld depth; the weld depth refers to the weld depth on the Kovar alloy side or the copper side;

[0006] Step 2: Drive the laser to adopt pulse laser mode or continuous laser mode, so that the laser welds along the welding path at a preset welding speed, melts the Kovar alloy and copper on the welding path, and makes the Kovar alloy adhere to the copper.

[0007] Accordingly, an embodiment of the present invention further provides a laser welding system for Kovar alloy and copper, comprising:

[0008] Acquisition module: collects welding path and weld depth information between the Kovar alloy and copper to be welded; the weld depth information is weld depth information on the Kovar alloy side or the copper side;

[0009] Driving module: drives the laser to adopt pulse laser mode or continuous laser mode, controls the laser to weld along the welding path at a preset welding speed, melts the Kovar alloy and copper on the welding path, and makes the Kovar alloy adhere to the copper.

[0010] The beneficial effects of the present invention are as follows: the present invention can achieve high-density energy concentration and improve welding efficiency; the present invention can accurately adjust laser parameters to ensure the stability and consistency of welding quality; during the welding process of the present invention, the heat-affected zone is small, the weld joint strength is high, and defects such as cracks and pores are few; the present invention is not only suitable for the welding of Kovar alloy and copper, but also for the welding of other dissimilar metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 1 is a flow chart of a laser welding method for Kovar alloy and copper according to an embodiment of the present invention.

[0012] Figure 2 This is a schematic diagram of the welding interface of Example 1 of the present invention. DETAILED DESCRIPTION

[0013] It should be noted that, unless there is a conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention is further described in detail below with reference to the drawings and specific embodiments.

[0014] In the embodiments of the present invention, if there are directional indications (such as up, down, left, right, front, back, etc.), they are only used to explain the relative position relationship and movement status of the various components under a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0015] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one of these features.

[0016] Please refer to Figure 1 The laser welding method of Kovar alloy and copper according to an embodiment of the present invention includes steps 1 and 2. The present invention is applied in lasers for welding Kovar alloy and copper in electronic devices, and is also applicable to welding other dissimilar metals.

[0017] Step 1: Clean the surfaces of the Kovar and copper to be welded. Place the Kovar and copper close together and secure them. Determine the welding path and weld depth. The weld depth is determined for either the Kovar or copper side. In practice, the weld depth is user-defined and should comply with national design standards. Generally, it should be no less than 0.5 times the thickness of the parent metal. For example, if the Kovar thickness is 1 cm, the weld depth on the Kovar side should be ≥ 0.5 cm. Under the same laser power density, the ratio of the weld depth on the Kovar side to the weld depth on the copper side is approximately 33:74. Therefore, the user only needs to set the weld depth on one side.

[0018] Step 2: Drive the laser to adopt pulse laser mode or continuous laser mode, so that the laser (i.e., the laser beam of the laser is controlled) is welded along the welding path at a preset welding speed, melts the Kovar alloy and copper on the welding path, and combines the Kovar alloy and copper.

[0019] As an implementation method, taking the weld depth on the Kovar alloy side as an example, in the continuous laser mode, the preset welding speed is obtained according to the following formula:

[0020] ;

[0021] ;

[0022] ;

[0023] Where h is the weld depth on the Kovar side, k is the thermal conductivity of Kovar (W / m·K), η is the heat input efficiency of the laser, ρ is the material density of Kovar (kg / m³), c is the specific heat capacity of Kovar (J / kg·K), and v is the preset welding speed (m / s). is the laser power density (W / m²), P is the output power of the laser in continuous laser mode (W), A is the area of ​​the laser spot irradiated at the weld (m²), and d is the diameter of the laser spot irradiated at the weld. The value of η varies depending on the welding process. The heat input efficiency η of laser welding is 0.5.

[0024] As an implementation method, taking the weld depth on the Kovar alloy side as an example, in the pulse laser mode, the preset welding speed is obtained according to the following formula:

[0025] ;

[0026] ;

[0027] ;

[0028] Where h is the weld depth on the Kovar side, k is the thermal conductivity of Kovar, η is the heat input efficiency of the laser, ρ is the material density of Kovar, c is the specific heat capacity of Kovar, and v is the preset welding speed. is the average power density of the pulsed laser, is the peak output power of the pulsed laser mode of the laser, t p is the pulse width, and f is the pulse frequency. This is the duty cycle.

[0029] Similarly, if the user is specifying the weld depth for the copper side, the calculation is the same, substituting the specific heat capacity, material density, and thermal conductivity coefficient for copper. Kovar alloy has a thermal conductivity k of approximately 17 W / m·K, a density ρ of approximately 8300 kg / m³, and a specific heat capacity c of approximately 400 J / kg·K. Copper has a thermal conductivity k of approximately 400 W / m·K, a density ρ of approximately 8960 kg / m³, and a specific heat capacity c of approximately 385 J / kg·K.

[0030] As an embodiment, during welding, the ratio of the laser beam's spot area projected onto the Kovar alloy to the spot area projected onto the copper is 7:3. Because weld depths differ on the Kovar and copper sides at the same laser intensity, a 7:3 ratio of the spot area on the Kovar alloy to the spot area on the copper results in better fusion between the copper and Kovar alloy, and the strongest bonding strength between the Kovar and copper molecules in the weld zone (the ratio of Kovar and copper molecules in the butt joint is approximately 1:1) is achieved.

[0031] As an embodiment, during laser welding, shielding gas is blown into the weld at the same time. The gas flow rate is preferably 15 L / min. Blowing shielding gas has no effect on the weld depth, but mainly affects the protection effect of the weld.

[0032] The device configuration during the specific implementation of the present invention is as follows:

[0033] 1. One kilowatt fiber laser, single mode, wavelength 1064 nm.

[0034] 2. Laser head, equipped with focusing lens, with adjustable focal length.

[0035] 3. Laser control system, which can accurately control laser power, pulse frequency and scanning speed.

[0036] 4. Welding fixture, used to fix Kovar alloy and copper parts to ensure stability during welding.

[0037] 5. Shielding gas system (nitrogen) is used to protect the welding area and prevent oxidation.

[0038] Material preparation: Clean the surfaces of the Kovar alloy and copper to be welded, remove the oxide layer and dirt; tightly connect the Kovar alloy and copper parts and place them in the welding fixture.

[0039] Welding process parameter settings: Laser power upper limit: 1000 W; Welding speed range: 1-1000 mm / s, adjusted according to material thickness and welding requirements; Laser mode: CW (continuous wave) or PULSE (pulsed wave). Shielding gas flow rate: 10-20 L / min.

[0040] Welding process: 1. Start the laser and adjust the focal position so that the laser beam is focused on the butt joint area of ​​the Kovar alloy and copper. 2. The laser moves along the welding path, melting the butt joint area of ​​the Kovar alloy and copper to achieve welding. 3. During the welding process, the shielding gas system continuously supplies gas to protect the welding area.

[0041] Post-weld treatment: 1. After welding is completed, cool the welding area; 2. Inspect the weld joint and perform non-destructive testing (such as X-ray testing, ultrasonic testing) and mechanical property testing (such as tensile testing, microhardness testing), airtightness testing (such as helium testing, halogen method).

[0042] The laser welding system for Kovar alloy and copper according to the embodiment of the present invention can be directly applied to a fiber laser. The laser welding system for Kovar alloy and copper includes an acquisition module and a drive module.

[0043] The acquisition module collects the weld path and weld depth information between the Kovar alloy and copper to be welded. The weld depth information refers to the weld depth on either the Kovar side or the copper side. The weld path can be acquired using machine vision or directly input by the user. The weld depth information is directly input by the user.

[0044] Driving module: drives the laser to adopt pulse laser mode or continuous laser mode, controls the laser to weld along the welding path at a preset welding speed, melts the Kovar alloy and copper on the welding path, and combines the Kovar alloy and copper.

[0045] As an implementation method, in the continuous laser mode, the driving module obtains the preset welding speed according to the following formula:

[0046] ;

[0047] ;

[0048] ;

[0049] Where h is the weld depth on the Kovar side, k is the thermal conductivity of Kovar, η is the heat input efficiency of the laser, ρ is the material density of Kovar, c is the specific heat capacity of Kovar, and v is the preset welding speed. is the power density of the laser, P is the output power of the continuous laser mode of the laser, A is the laser spot area of ​​the laser, and d is the spot diameter of the laser.

[0050] As an implementation method, in the pulse laser mode, the driving module obtains the preset welding speed according to the following formula:

[0051] ;

[0052] ;

[0053] ;

[0054] Where h is the weld depth on the Kovar side, k is the thermal conductivity of Kovar, η is the heat input efficiency of the laser, ρ is the material density of Kovar, c is the specific heat capacity of Kovar, and v is the preset welding speed. is the average power density of the pulsed laser, is the peak output power of the pulsed laser mode of the laser, t p is the pulse width, and f is the pulse frequency.

[0055] As an embodiment, during welding, the driving module controls the ratio of the spot area of ​​the laser irradiated on the Kovar alloy to the spot area of ​​the laser irradiated on the copper to be 7:3.

[0056] As an embodiment, the laser welding system of Kovar alloy and copper further includes a gas supply module, which blows protective gas into the welding point during laser welding.

[0057] Example 1: Using continuous wave mode, laser power 100 W, welding speed 470 mm / s, shielding gas flow 15 L / min. Kovar alloy with a thickness of 0.11 mm and copper were welded to obtain a crack-free, highly airtight weld interface. Figure 2 shown.

[0058] Example 2: Using pulsed wave mode, a laser power of 80 W, a pulse frequency of 300 Hz, a welding speed of 3 mm / s, and a shielding gas flow rate of 10 L / min, a 0.15 mm thick Kovar alloy and copper were welded. The welded joint exhibited uniform microhardness and was free of porosity.

[0059] The present invention has the advantages of efficient energy transmission, precise control, excellent welding quality and wide applicability. It can significantly improve welding efficiency and product quality and is suitable for electronic packaging, manufacturing and other fields.

[0060] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A laser welding method for Kovar alloy and copper, characterized in that: include: Step 1: Clean the surfaces of the Kovar alloy and copper to be welded, place the Kovar alloy and copper close together and secure them, and determine the welding path and weld depth; the weld depth refers to the weld depth on the Kovar alloy side or the copper side; Step 2: Drive the laser to adopt pulse laser mode or continuous laser mode, so that the laser performs welding along the welding path at a preset welding speed, melts the Kovar alloy and copper on the welding path, and makes the Kovar alloy adhere to the copper; In continuous laser mode, the preset welding speed is obtained according to the following formula: ； ； ； Where h is the weld depth on the Kovar side, k is the thermal conductivity of Kovar, η is the heat input efficiency of the laser, ρ is the material density of Kovar, c is the specific heat capacity of Kovar, and v is the preset welding speed. is the power density of the laser, P is the output power of the continuous laser mode of the laser, A is the laser spot area of ​​the laser, and d is the spot diameter of the laser; In pulse laser mode, the preset welding speed is obtained according to the following formula: ； ； ； Where h is the weld depth on the Kovar side, k is the thermal conductivity of Kovar, η is the heat input efficiency of the laser, ρ is the material density of Kovar, c is the specific heat capacity of Kovar, and v is the preset welding speed. is the average power density of the pulsed laser, is the peak output power of the pulsed laser mode of the laser, t p is the pulse width, f is the pulse frequency, A is the laser spot area, and d is the laser spot diameter; During welding, the ratio of the spot area on the Kovar alloy to the spot area on the copper is 7:

3.

2. The laser welding method of Kovar alloy and copper according to claim 1, characterized in that: During laser welding, shielding gas is blown into the welding area at the same time.

3. A laser welding system for Kovar alloy and copper, characterized in that: The laser welding method for Kovar alloy and copper according to any one of claims 1 to 2 is adopted, wherein the system comprises: Acquisition module: collects welding path and weld depth information between the Kovar alloy and copper to be welded; the weld depth information is weld depth information on the Kovar alloy side or the copper side; Driving module: drives the laser to adopt pulse laser mode or continuous laser mode, controls the laser to weld along the welding path at a preset welding speed, melts the Kovar alloy and copper on the welding path, and makes the Kovar alloy adhere to the copper.

4. The laser welding system for Kovar alloy and copper according to claim 3, wherein: In continuous laser mode, the driver module obtains the preset welding speed according to the following formula: ； ； ； Where h is the weld depth on the Kovar side, k is the thermal conductivity of Kovar, η is the heat input efficiency of the laser, ρ is the material density of Kovar, c is the specific heat capacity of Kovar, and v is the preset welding speed. is the power density of the laser, P is the output power of the continuous laser mode of the laser, A is the laser spot area of ​​the laser, and d is the spot diameter of the laser.

5. The laser welding system for Kovar alloy and copper according to claim 3, wherein: In pulse laser mode, the driver module obtains the preset welding speed according to the following formula: ； ； ； Where h is the weld depth on the Kovar side, k is the thermal conductivity of Kovar, η is the heat input efficiency of the laser, ρ is the material density of Kovar, c is the specific heat capacity of Kovar, and v is the preset welding speed. is the average power density of the pulsed laser, is the peak output power of the pulsed laser mode of the laser, t p is the pulse width, f is the pulse frequency, A is the laser spot area of ​​the laser, and d is the laser spot diameter.

6. The laser welding system for Kovar alloy and copper according to claim 3, wherein: During welding, the driving module controls the ratio of the spot area of ​​the laser irradiated on the Kovar alloy to the spot area of ​​the laser irradiated on the copper to be 7:

3.

7. The laser welding system for Kovar alloy and copper according to claim 3, wherein: It also includes a gas supply module, which blows protective gas into the welding point during laser welding.

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