Resistance brazing device for electronic packaging and in-situ wettability detection and resistance brazing integrated method

Abstract

The invention belongs to the field of resistance brazing, and particularly relates to a resistance brazing device for electronic packaging and an in-situ wettability detection and resistance brazing integrated method. The device comprises a graphite block, parallel electrodes, a pressure head and a three-way high-speed camera, the graphite block comprises a positioning area and a heating area, and the positioning area is provided with a rectangular groove and an inverted T-shaped groove to realize accurate positioning of a substrate; the method comprises the following steps: firstly, carrying out wettability detection, inserting a substrate into a graphite block positioning area and placing brazing filler metal, electrifying a parallel electrode and applying pulse current for heating, and capturing dynamic changes of a wetting angle and a wetting area in real time by a three-way high-speed camera so as to adjust the brazing filler metal or optimize parameters; and then resistance welding is carried out, a substrate, brazing filler metal and a chip are sequentially placed, and after pressing is carried out through a pressing head, same-parameter electrification is carried out to complete welding. According to the method, millisecond-level efficient heating can be achieved, wettability detection is consistent with welding thermal conditions, in-situ dynamic observation of wetting behaviors is achieved, data distortion caused by thermal condition differences is eliminated, and the welding efficiency and quality are effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of resistance brazing technology, specifically relating to a resistance brazing apparatus for electronic packaging and an integrated method for in-situ wettability detection and resistance brazing. Background Technology

[0002] In the field of electronic packaging manufacturing, highly reliable and efficient material interconnect technologies are crucial, directly affecting the performance and lifespan of the final product. Brazing, as a commonly used and effective connection method, is widely used in electronic packaging interconnects due to its advantages such as the ability to connect dissimilar materials and good interface bonding. Traditional brazing processes, such as furnace brazing or flat-plate brazing, generally suffer from problems such as slow thermal response, large temperature gradients in the heating zone, and high energy consumption, making it difficult to meet the demands of modern electronic packaging for efficient and precise welding. In particular, for high thermal conductivity materials such as SiC and Cu, or heat-sensitive devices, the slow heating / cooling process may lead to excessive interface reaction, increased residual stress, or thermal damage to the device, affecting the interconnect quality and reliability.

[0003] The wetting behavior of the brazing filler metal is a core factor determining the quality of brazed joints. The dynamic changes in the wetting angle and wetting area directly reflect the interfacial reaction and spreading ability between the filler metal and the base metal. In existing technologies, wettability assessment usually employs independent testing methods (such as the droplet method) detached from the actual welding environment, or static microscopic observation after welding. However, the thermal cycling conditions (such as heating rate, peak temperature, holding time, and cooling rate) during independent testing often differ significantly from actual brazing process parameters, leading to inaccurate results reflecting the actual wetting dynamics at the weld interface. Furthermore, static microscopic observation lacks in-situ dynamic observation methods with multi-view, high spatiotemporal resolution for the wetting process (especially the key stages of filler metal melting, spreading, and solidification), making it difficult to capture and quantify transient changes in the wetting angle and real-time expansion of the spreading area. This limits researchers' in-depth understanding of the interfacial wetting mechanism and process optimization.

[0004] Therefore, developing an integrated method for in-situ wettability testing and resistance brazing, which allows for in-situ, multi-view, and dynamic real-time observation of the wetting behavior of the brazing filler metal under real welding thermodynamic conditions, is of great significance for improving the efficiency and quality of electronic packaging interconnection and promoting the advancement of packaging technology. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by proposing a resistance brazing apparatus for electronic packaging and an integrated method for in-situ wettability testing and resistance brazing, so as to achieve efficient and reliable interconnection of electronic packaging materials and provide a dedicated in-situ wettability testing method.

[0006] The present invention adopts the following technical solution: A resistance brazing apparatus for electronic packaging includes a graphite block, which is divided into a positioning area and a heating area from top to bottom. The positioning area is used to place a substrate, and parallel electrodes for heating the graphite block are provided on both sides of the heating area. A pressure head is provided on the top of the graphite block, which is used to press the chip to be connected and the solder onto the substrate. A camera assembly is provided around the graphite block, which is used to capture images of the front, side and top surfaces of the wetted sample throughout the wettability testing process.

[0007] To ensure precise positioning of the substrate and facilitate substrate replacement, a first groove and a second groove are respectively provided along the center lines of two sets of opposite sides on the upper surface of the graphite block. The cross-sectional shapes of the first groove and the second groove are rectangular and inverted "T" shaped, respectively. The first groove and the second groove constitute a positioning area, and the substrate can be quickly inserted into the positioning area along the second groove. The height H and width L of the positioning area satisfy: H=D+0.1mm, L=l+0.1mm, where D is the thickness of the substrate and L is the width of the substrate.

[0008] To better observe the dynamic changes in the wetting angle and wetting area of ​​the wetted sample, the imaging assembly includes a computer and three high-speed cameras electrically connected to the computer. The computer is used to acquire and analyze the video data from the three high-speed cameras in real time. The frame rate of the three high-speed cameras is 10-16000 FPS. The three high-speed cameras are located directly above, to the side, and in front of the graphite block, respectively. The first groove and the second groove provide the observation field of view for the three-way high-speed cameras, which facilitates the accurate recording of wetting angle and wetting area data.

[0009] To further improve heating efficiency, a stepped structure is provided on the adjacent sides of the two parallel electrodes. The graphite block is detachably clamped on the stepped structure between the two parallel electrodes, and the side of the parallel electrode in contact with the graphite block is a rough surface.

[0010] To further ensure precise positioning of the substrate, the height H and width L of the positioning area satisfy: H = D + 0.1 mm, L = l + 0.1 mm, where D is the thickness of the substrate and l is the width of the substrate.

[0011] To facilitate in-situ wettability testing and welding operations, a turntable bracket is provided on the top of the graphite block. The pressure head and the high-speed camera located directly above the graphite block are both mounted on the turntable bracket. Rotating the turntable bracket can rotate the pressure head or the high-speed camera to directly above the graphite block. The high-speed cameras located on the sides and front of the graphite block are fixed by a fixed bracket.

[0012] An integrated method for in-situ wettability testing and resistance brazing includes the following steps: Step 1: Using the resistance brazing device described above, insert the substrate into the positioning area along the second groove of the graphite block, and place the solder to be tested on the surface of the substrate. Step 2: Clamp the graphite block onto the parallel electrode, ensuring that the side of the graphite block is in full contact with the parallel electrode. Step 3: Turn on the camera assembly and apply a pulsed current to the parallel electrodes. The current flows through the graphite block and generates Joule heat. The heat is conducted through the graphite block to the wetting interface, causing the solder to be tested to heat up rapidly to above its melting point and wet the substrate. Cut off the current and remove the substrate after cooling. Step 4: Based on the images acquired by the camera assembly, observe and analyze the dynamic changes in the wetting angle and wetting area of ​​the wetted sample. If the solder has excellent performance, use the solder for subsequent welding work. Otherwise, adjust the solder composition or pulse parameters and repeat steps 1-4 until the performance of the tested solder meets the requirements for subsequent welding work. Step 5: Insert the substrate into the positioning area along the second groove of the graphite block, place the tested and qualified solder on the surface of the area to be soldered on the substrate, and place the chip to be connected above or to the side of the solder. Step 6: Clamp the graphite block onto the parallel electrode, ensuring that the side of the graphite block is in full contact with the parallel electrode. Step 7: Press the pressure head downwards to firmly connect the chip to the substrate, ensuring a tight connection between the chip and the substrate; Step 8: Apply a pulsed current to the parallel electrodes. The Joule heat generated by the current is conducted to the interconnect interface through the graphite block. The connection between the chip and the substrate is rapidly heated to above the melting point of the solder, causing the solder to melt and wet the base material. Cut off the current and remove the connected substrate and chip assembly after cooling. Repeating steps 5-8 above will enable mass welding of the substrate and the chip.

[0013] Furthermore, the thickness of the substrate and the chip is 0.5-4mm, and the cross-sectional dimensions are 5×5-30×30mm; the solder can be paste solder, foil solder or block solder, and the amount used each time is 20-300mg.

[0014] Furthermore, the substrate and chip comprise homogeneous or heterogeneous SiC, Cu, and ceramic materials.

[0015] Furthermore, in steps 3 and 7, the current applied is in the range of 800-1200A, the pulse width is in the range of 30ms-300ms, and the number of pulses is 5-20.

[0016] Compared with the prior art, the present invention has the following technical effects: This invention eliminates traditional external heat sources (such as hot plates and furnaces) and applies pulsed current (800-1200A) to a specially made graphite block through parallel electrodes. It utilizes the Joule effect to achieve rapid and uniform heating at the millisecond level (pulse width 30-300ms), with heat directly conducted to the brazing filler metal interface. The uniform temperature effectively reduces residual stress and interface defects, improves welding quality, and its thermal response speed is more than 10 times faster than traditional second-level heating, significantly shortening the welding cycle, improving welding efficiency, and increasing production capacity. This invention utilizes high-speed cameras (frame rate 10-16000 FPS) deployed on the top, front, and side surfaces of a graphite block, combined with a modular groove structure (first groove and second groove) to provide a field of view, simultaneously capturing the dynamic changes in wetting angle and wetting area. This invention achieves, for the first time, multi-view in-situ dynamic recording of the entire wetting process, overcoming the limitations of traditional static observation (such as post-weld microscopic analysis). The wettability detection and brazing interconnection of this invention are completed in the same device, and the thermal cycling conditions (heating rate, pulse width, peak temperature) of the two are completely consistent, realizing in-situ dynamic observation of the changes in wetting angle and wetting area, eliminating the distortion of detection data caused by differences in thermal conditions, providing wetting kinetic data under real welding conditions, and the detection data has high reliability and can be directly used for welding process optimization. It realizes efficient and reliable electronic packaging interconnection technology, and provides technical support for cutting-edge fields such as high-end chip packaging and third-generation semiconductors (SiC). Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the graphite block structure of the resistance brazing apparatus of the present invention; Figure 2 This is a schematic diagram illustrating the operation of the in-situ wettability detection method of the present invention; Figure 3 A schematic diagram of an image captured by the camera component; Figure 4 A schematic diagram illustrating the operation of resistance brazing. Figure 5 The cross-sectional morphology of the Cu-Cu interconnect sample; Figure 6 Shear properties and fracture morphology of Cu-Cu interconnect samples; In the figure: Graphite block 1, positioning area 11, heating area 12, first groove 13, second groove 14, parallel electrode 2, stepped structure 21, rough surface 22, pressure head 3, high-speed camera 4, turntable support 5, substrate 6, solder 7, chip 8. Detailed Implementation

[0018] The following detailed description illustrates the specific implementation method: Example

[0019] A resistance brazing apparatus for electronic packaging, such as Figure 1 As shown, the system includes a graphite block 1, which is divided into a positioning area 11 and a heating area 12 from top to bottom. The positioning area 11 is used to place the substrate 6. A first groove 13 and a second groove 14 are respectively opened along the center lines of two sets of opposite sides on the upper surface of the graphite block 1. The cross-sectional shapes of the first groove 13 and the second groove 14 are rectangular and inverted "T" shaped, respectively. The first groove 13 and the second groove 14 constitute the positioning area 11. The height H and width L of the positioning area 11 satisfy: H=D+0.1mm, L=l+0.1mm, where D is the thickness of the substrate 6 and l is the width of the substrate 6. The substrate 6 can be quickly inserted into the positioning area 11 along the second groove 14. Parallel electrodes 2 for heating the graphite block 1 are provided on both sides of the heating area 12. A stepped structure 21 is provided on the adjacent side of the two parallel electrodes 2. The graphite block 1 can be detachably clamped on the stepped structure 21 between the two parallel electrodes 2. The side of the parallel electrode 2 that contacts the graphite block 1 is roughened to a rough surface 22 by sanding with 500-2000# sandpaper.

[0020] The resistance brazing apparatus of this embodiment, such as Figure 2 As shown, it also includes a pressure head 3 and a camera assembly. The pressure head 3 is used to press the chip 8 and solder 7 onto the substrate 6. The camera assembly includes three high-speed cameras 4 with a frame rate of 10-16000 FPS. The three high-speed cameras 4 are used to capture images of the front, side, and top surfaces of the wetted sample throughout the wettability testing process. A turntable bracket 5 is mounted on the top of the graphite block 1. The pressure head 3 and one high-speed camera 4 are mounted on the turntable bracket 5. Rotating the turntable bracket 5 can rotate the pressure head 3 or the high-speed camera 4 to be directly above the graphite block 1. The other two high-speed cameras 4 are mounted on the side and front of the graphite block 1 respectively by fixed brackets. The camera assembly also includes a computer electrically connected to the three high-speed cameras 4. The computer is used to acquire and analyze the image data of the three high-speed cameras 4 in real time to observe the dynamic changes in the wetting angle and wetting area of ​​the wetted sample. The images captured by the three high-speed cameras are shown in the figure. Figure 3 As shown.

[0021] An integrated method for in-situ wettability testing and resistance brazing includes the following steps: In this embodiment, the electronic packaging interconnect material used is copper. The cross-sectional dimensions of the substrate 6 and the chip 8 are 10 mm × 10 mm and 5 mm × 5 mm, respectively, and the thicknesses are 1.0 mm and 0.5 mm, respectively. The solder 7 used is commercially available tin-based solder 7, in the form of foil. Step 1: Using the resistance brazing device described above, insert the substrate 6 into the positioning area 11 along the second groove 14 of the graphite block 1 to fix the position of the substrate 6. Use pliers to cut a 20mg piece from the foil-shaped Sn-based solder 7 as the solder to be tested. Place the solder to be tested 7 on the surface of the copper alloy substrate 6. Use a dropper to take 0.5ml of commercially available flux and drop it onto the surface of the solder to be tested 7. The entire interface is evenly wetted by capillary action. Step 2, as follows Figure 2 As shown, the graphite block 1 is clamped onto the stepped structure 21 of the two parallel electrodes 2, and the two sides of the graphite block 1 are in close contact with the rough surfaces 22 of the two parallel electrodes 2 respectively. Step 3, as follows Figure 2 As shown, adjust the position of the turntable bracket 5 so that the high-speed camera 4 on the top of the graphite block 1 is moved directly above the graphite block 1. Turn on the camera assembly and pass a pulse current to the parallel electrode 2. The current range is 800-1200A, the pulse width range is 30ms-300ms, and the number of pulses is 5-20. The current flows through the graphite block 1 and generates Joule heat. The heat is conducted through the graphite block 1 to the wetting interface, causing the solder 7 to be tested to heat up rapidly to above the melting point and wet the substrate 6. Cut off the current and take out the substrate 6 after cooling. Step 4: Based on the images acquired by the camera assembly, observe and analyze the dynamic changes in the wetting angle and wetting area of ​​the wetted sample. Specifically, if the wetting angle of the solder 7 is <20° and the wetting area is >100mm², then... 2 If the brazing filler metal 7 has good wettability, it can be used for subsequent welding work. Otherwise, adjust the composition of the brazing filler metal 7 or the pulse parameters, and repeat steps 1-4 above until the performance of the tested brazing filler metal 7 meets the requirements of subsequent welding work. Step 5: Insert the substrate 6 into the positioning area 11 along the second groove 14 of the graphite block 1 to fix the position of the substrate 6. Cut the foil-shaped solder 7 of the corresponding size according to the size of the chip 8. Use tweezers to place the solder 7 on the surface of the area to be soldered on the substrate 6. Then place the chip 8 to be connected on top of the solder 7. Use a dropper to take 0.5 ml of commercially available flux and drop it on the edge of the interconnect interface. The entire interface is evenly wetted by capillary action to prevent oxidation of the solder 7 and the interface. Step 6, as follows Figure 4 As shown, the graphite block 1 is clamped onto the stepped structure 21 of the two parallel electrodes 2, so that the two sides of the graphite block 1 are in close contact with the rough surfaces 22 of the two parallel electrodes 2 respectively. Step 7, as follows Figure 4 As shown, rotate the turntable support 5 to move the pressure head 3 directly above the graphite block 1, and apply a pressure of 15N downward to the chip 8 to be connected, so as to ensure the assembly relationship between the substrate 6 and the chip 8 connector. Step 8: Apply a pulsed current to the parallel motor. The current range is 800-1200A, the pulse width range is 30ms-300ms, and the number of pulses is 5-20. The Joule heat generated by the current is conducted to the interconnection interface through the graphite block 1, which causes the connection between the chip 8 and the substrate 6 to heat up rapidly to above the melting point of the solder 7, so that the solder 7 melts and wets the base material. Cut off the current and take out the substrate 6 and chip 8 assembly that are connected together after cooling. Repeating steps 5-8 above will enable mass welding of substrate 6 and chip 8.

[0022] Millisecond-level pulse heating is achieved by energizing the graphite block with parallel electrodes, increasing welding efficiency by more than 10 times, avoiding thermal damage and excessive interfacial reactions, and significantly reducing the formation of brittle intermetallic compounds (IMCs) (see...). Figure 5 (Cross-sectional morphology); Simultaneously, it integrates a three-dimensional high-speed camera to capture transient changes in wetting angle and wetting area in situ, breaking through the limitations of traditional static detection; Furthermore, through the integrated design of wettability inspection and brazing processes, it ensures that the detection conditions are completely consistent with the actual welding thermal environment, and precisely optimizes parameters based on dynamic data (such as adjusting the pulse width to improve the wetting angle), thereby increasing the joint shear strength by 15-30% ( Figure 6 This ensures high reliability of electronic packaging interconnects.

[0023] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A resistance brazing apparatus for electronic packaging, characterized in that: The graphite block (1) is divided into a positioning area (11) and a heating area (12) from top to bottom. The positioning area (11) is used to place the substrate (6). Parallel electrodes (2) for heating the graphite block (1) are provided on both sides of the heating area (12). A pressure head (3) is provided on the top of the graphite block (1). The pressure head (3) is used to press the chip (8) to be connected and the solder (7) onto the substrate (6). A camera assembly is provided around the graphite block (1). The camera assembly is used to capture images of the front, side and top surfaces of the wetted sample during the entire wettability detection process.

2. The resistance brazing apparatus according to claim 1, characterized in that: A first groove (13) and a second groove (14) are provided along the center lines of two sets of opposite sides on the upper surface of the graphite block (1). The cross-sectional shapes of the first groove (13) and the second groove (14) are rectangular and inverted "T" shaped, respectively. The first groove (13) and the second groove (14) constitute a positioning area (11). The substrate (6) can be quickly inserted into the positioning area (11) along the second groove (14).

3. The resistance brazing apparatus according to claim 1 or 2, characterized in that: The camera assembly includes a computer and three high-speed cameras (4) electrically connected to the computer. The computer is used to acquire and analyze the camera data of the three high-speed cameras (4) in real time. The three high-speed cameras (4) are located directly above, to the side and in front of the graphite block (1), respectively.

4. The resistance brazing apparatus according to claim 3, characterized in that: The two parallel electrodes (2) have a stepped structure (21) on their adjacent sides. The graphite block (1) is detachably clamped on the stepped structure (21) between the two parallel electrodes (2). The side of the parallel electrode (2) that contacts the graphite block (1) is a rough surface (22).

5. The resistance brazing apparatus according to claim 2, characterized in that: The height H and width L of the positioning area (11) satisfy: H=D+0.1mm, L=l+0.1mm, where D is the thickness of the substrate (6) and L is the width of the substrate (6).

6. The resistance brazing apparatus according to claim 3, characterized in that: The graphite block (1) is provided with a turntable bracket (5) on top. The pressure head (3) and the high-speed camera (4) located directly above the graphite block (1) are both mounted on the turntable bracket (5). Rotating the turntable bracket (5) can rotate the pressure head (3) or the high-speed camera (4) to directly above the graphite block (1). The high-speed camera (4) located on the side and in front of the graphite block (1) is fixed by a fixed bracket.

7. A method for integrating in-situ wettability testing and resistance brazing, characterized in that, Includes the following steps: Step 1: Using the above-mentioned resistance brazing device, insert the substrate (6) into the positioning area (11) along the second groove (14) of the graphite block (1), and place the solder (7) to be tested on the surface of the substrate (6). Step 2: Clamp the graphite block (1) onto the parallel electrode (2) so that the side of the graphite block (1) is in full contact with the parallel electrode (2); Step 3: Turn on the camera assembly and pass a pulse current through the parallel electrode (2). The current flows through the graphite block (1) to generate Joule heat. The heat is conducted through the graphite block (1) to the wetting interface, causing the solder (7) to be tested to heat up quickly to above its melting point and wet the substrate (6). Cut off the current and take out the substrate (6) after cooling. Step 4: Based on the image acquired by the camera component, observe and analyze the dynamic changes of the wetting angle and wetting area of ​​the wetted sample. If the performance of the solder (7) is excellent, then use the solder (7) for subsequent welding work. Otherwise, adjust the composition or pulse parameters of the solder (7) and repeat the above steps 1-4 until the performance of the tested solder (7) meets the requirements of subsequent welding work. Step 5: Insert the substrate (6) into the positioning area (11) along the second groove (14) of the graphite block (1), place the tested and qualified solder (7) on the surface of the soldering area of ​​the substrate (6), and place the chip (8) to be connected above or to the side of the solder (7). Step 6: Clamp the graphite block (1) onto the parallel electrode (2) so that the side of the graphite block (1) is in full contact with the parallel electrode (2); Step 7: Press the pressure head (3) downwards to firmly connect the chip (8) to the substrate (6), so that the chip (8) is tightly connected to the substrate (6); Step 8: Pulse current is applied to the parallel electrode (2). The Joule heat generated by the current is conducted to the interconnect interface through the graphite block (1). The connection between the chip (8) and the substrate (6) is rapidly heated to above the melting point of the solder (7), so that the solder (7) melts and wets the base material. The current is cut off. After cooling, the substrate (6) and chip (8) assembly connected together are taken out. Repeating steps 5-8 above will enable mass welding of the substrate (6) and the chip (8).

8. The method according to claim 5, characterized in that: The thickness of the substrate (6) and the chip (8) is 0.5-4mm, and the cross-sectional size is 5×5-30×30mm; the solder (7) can be paste solder (7), foil solder (7) or block solder (7), and the amount used each time is 20-300mg.

9. The method according to claim 5, characterized in that: The substrate (6) and the chip (8) comprise homogeneous or heterogeneous SiC, Cu and ceramic materials.

10. The method according to claim 5, characterized in that: In steps 3 and 7, the current applied is in the range of 800-1200A, the pulse width is in the range of 30ms-300ms, and the number of pulses is 5-20.

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