Flip chip method and apparatus

Abstract

The application discloses a flip chip bonding method and device, comprising a vacuumizing and hot air blowing device, and a lower mold placed on the vacuumizing and hot air blowing device; a wafer positioning plate is arranged on the lower mold, a wafer is placed in a wafer groove on the wafer positioning plate, the openings on the steel mesh correspond to the wafer pads and cover the wafer, and the solder paste is coated on the wafer pads through the openings of the steel mesh; the upper mold is closed to tightly bond the BT plate and the wafer pad; the solder paste on the wafer pad is heated by the hot air blowing of the vacuumizing and hot air blowing device, and the hot air blowing reflow soldering between the BT plate and the wafer is realized. Through the above mode, the problems of uneven solder paste brushing of the existing steel mesh, uncontrollable floating of the chip bonding reflow soldering, and the like are solved, and the traditional single-chip bonding mode is changed, so that the efficiency is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of LED packaging technology and relates to a flip-chip die bonding method and apparatus. Background Technology

[0002] In modern electronics manufacturing, especially in the process of connecting chips to BT boards (substrates), a common and critical technique is to apply solder paste to the BT board, then precisely fix the chip onto the solder paste-covered pads of the BT board, and finally achieve a strong connection through reflow soldering.

[0003] In this process, a stencil is typically first applied to the BT board, onto which solder paste is then applied. The solder paste plays a crucial role, providing a key medium for the subsequent reliable connection between the chip and the BT board. Subsequently, the chips are individually secured to the solder paste-coated pads on the BT board using a swing arm and nozzle. This operation demands a high degree of precision and accuracy to ensure the correct position and orientation of the chips on the BT board.

[0004] However, in actual production, a series of severe challenges are encountered. One prominent problem is the uneven ink thickness on the front side of the BT board. This inconsistency in ink thickness leads to significant differences in the amount of solder paste on the BT board pads. This difference severely affects the performance of the solder paste during reflow soldering and the final connection quality.

[0005] Inconsistent solder paste amounts can lead to numerous adverse consequences. First, during reflow soldering, areas with excessive solder paste may experience solder balling. This not only causes chip floating (i.e., loose connections between the chip and the BT board, resulting in gaps), but can also cause the chip to be misaligned on the BT board, failing to achieve the precise positioning required by the design. This poses a significant threat to the performance and reliability of electronic devices, potentially leading to unstable signal transmission, increased resistance, or even equipment malfunction.

[0006] Furthermore, the slow speed of die bonding on a single die is a bottleneck for improving production efficiency in large-scale production. Slower die bonding speeds not only increase production costs but can also lead to longer production cycles, making it difficult to meet market demands in a timely manner.

[0007] Furthermore, the aforementioned issues of solder paste quantity variation and slow die bonding speed make quality control throughout the production process extremely difficult. It becomes impossible to effectively guarantee that the connection quality between each BT board and the chip meets the expected standards, thus increasing the defect rate and scrap rate, further amplifying production costs and resource waste.

[0008] Therefore, it is necessary to improve existing technologies to overcome their shortcomings. Summary of the Invention

[0009] The purpose of this invention is to provide a flip-chip die bonding method and apparatus to solve problems such as uneven solder paste application on existing stencils, uncontrollable die bonding reflow soldering leading to floating and chip misalignment.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A flip-chip die bonding device, comprising:

[0012] A vacuuming and hot air blowing fixture has a platform for placing a lower mold. The platform is provided with several small holes. The suction force or hot air blowing on the vacuuming and hot air blowing fixture acts on the lower mold through the small holes.

[0013] The lower mold is provided with a number of ventilation holes corresponding to the small holes. The lower mold is provided with a wafer positioning plate. The suction force of the vacuum and hot air blowing fixture or the hot air blowing through the small holes and ventilation holes acts on the wafer positioning plate to position or heat the wafer positioning plate.

[0014] A wafer positioning plate is provided with a plurality of wafer slots for placing wafers, the wafers being placed upside down in the wafer slots; the bottom of the wafer slots is provided with vacuum holes, the distribution density of the vacuum holes being lower than that of the vent holes on the lower mold; a stencil is provided on the wafer positioning plate, the openings of the stencil being aligned with the wafer pads, so that solder paste is applied to the wafer pads;

[0015] The upper mold presses against the BT board, bringing the BT board into contact with the chip pad coated with solder paste, and then closes with the lower mold to tightly bond the BT board and the chip pad.

[0016] As a further improvement of one embodiment of the present invention, the lower mold is provided with a groove, the wafer positioning plate is embedded in the groove, and the groove is provided with the vent hole.

[0017] As a further improvement of one embodiment of the present invention, positioning pins are provided at the four corners of the lower mold, and positioning holes adapted to the positioning pins are provided on both the BT plate and the upper mold.

[0018] As a further improvement of one embodiment of the present invention, the vacuuming and hot air blowing fixture is provided with a main pipe that is connected to all the small holes. The vacuuming and hot air blowing fixture has two air inlets that are connected to the main pipe. Each air inlet is provided with a valve. One air inlet is connected to a vacuuming device and the other air inlet is connected to a hot air blowing device.

[0019] A flip-chip bonding method, employing the flip-chip bonding apparatus as described above, includes the following steps:

[0020] Step 1: Select a wafer positioning board of appropriate size and spacing according to the BT board pad design and wafer size, place the wafer positioning board on the lower mold, and fix the lower mold on the vacuum and hot air blowing fixture;

[0021] Step 2: Place the wafer in the wafer slot of the wafer positioning plate with the wafer pad facing upwards, and use a vacuuming and hot air blowing fixture to fix the wafer in the wafer slot.

[0022] Step 3: Select the corresponding stencil and cover the chip with the stencil. The openings on the stencil should correspond to the chip pads. Apply solder paste to the chip pads through the openings on the stencil.

[0023] Step 4: Place the BT board on the lower mold, and cover the lower mold with the upper mold to achieve mold closing between the upper and lower molds, so that the BT board and the chip pad are tightly attached.

[0024] Step 5: Vacuuming and hot air blowing. The fixture is switched from vacuuming to hot air blowing. Hot air is blown and reflow soldered on the BT board and the wafer pad in the mold to complete the die bonding.

[0025] As a further improvement of one embodiment of the present invention, in step 1, the lower mold has a groove for placing a wafer positioning plate, the wafer positioning plate being sized to match the groove; the wafer positioning plate and the bottom surface of the groove are tightly fitted under vacuum, and the wafer positioning plate is in a horizontal state.

[0026] As a further improvement of one embodiment of the present invention, in step 2, a vacuum hole is provided in the wafer slot, and the distribution density of the vacuum hole is lower than that of the vent hole on the lower mold. The vacuuming and hot blowing fixture can separately vacuum or heat blow the wafer slot through the vacuum hole.

[0027] As a further improvement to one embodiment of the present invention, in step 3, solder paste is uniformly applied to the chip pad through the openings of the stencil using a scraper or a dispensing machine.

[0028] As a further improvement to one embodiment of the present invention, the hot air reflow soldering in step 5 requires the following steps:

[0029] Step 51: Set parameters: Based on the characteristics of the solder paste, the materials of the chip and BT board, and the process requirements, set the temperature profile for hot air reflow soldering;

[0030] Step 52, Reflow Stage: The temperature rises rapidly to the melting point of the solder paste, which melts and forms a good electrical and mechanical connection between the chip and the BT board;

[0031] Step 53, Cooling Stage: After the reflow stage, cooling is performed to solidify the solder joints and form a strong connection;

[0032] Step 54, Inspection and Testing: After reflow soldering is completed, remove the components for visual inspection to check for defects such as cold solder joints, short circuits, and solder balls.

[0033] As a further improvement of one embodiment of the present invention, the parameters in step 51 include the temperature and time of the preheating zone, the peak temperature and time of the reflux zone, and the cooling rate of the cooling zone.

[0034] The above technical solution has the following advantages: the wafer is limited by the wafer positioning plate, so there will be no floating or offset phenomenon, and a large amount of transfer can be performed. The use of solder paste on the wafer avoids the situation where the solder paste size of the stencil is uneven due to the unevenness of the BT board. The use of hot air heating avoids the temperature difference caused by the carrier absorbing heat during reflow soldering in the traditional process. Attached Figure Description

[0035] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0036] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0037] Figure 1 This is a schematic diagram of the flip-chip die bonding device provided by the present invention.

[0038] Figure 2 This is a schematic diagram of the wafer positioning plate structure provided by the present invention.

[0039] Figure 3 This is a schematic diagram of the lower mold structure provided by the present invention.

[0040] Figure 4 This is a schematic diagram of the process provided by the present invention.

[0041] In the diagram: 1-vacuuming and hot air blowing fixture; 2-lower mold; 21-groove; 22-vent hole; 23-positioning pin; 3-BT board; 4-upper mold; 5-wafer positioning plate; 51-wafer slot; 52-vacuum hole. Detailed Implementation

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0044] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention. Example

[0045] See Figure 4 As shown, a flip-chip die bonding method includes the following steps:

[0046] S1. Select a wafer positioning plate 5 of appropriate size and spacing based on the BT board 3 pad design and wafer dimensions, and place the wafer positioning plate 5 on the lower mold 2. The lower mold 2 is then fixedly installed in the vacuum and hot air blowing fixture. The placement of the wafer positioning plate 5 on the lower mold 2 typically has the following requirements:

[0047] Position accuracy: The wafer positioning plate must be precisely placed in the predetermined position and fully aligned with the relevant structures and markings of the lower mold to ensure the accuracy of subsequent wafer placement;

[0048] Levelness: Ensure that the wafer positioning plate is level after placement, and avoid tilting or twisting, otherwise it may affect the positioning accuracy of the wafer.

[0049] Tight fit: The contact surface with the lower mold should fit tightly without gaps or looseness to prevent displacement during operation;

[0050] Cleanliness: Before placement, the contact surfaces of the wafer positioning plate and the lower mold should be kept clean and free of dust, oil or other impurities to ensure good contact and positioning effect;

[0051] Orientation accuracy: According to design requirements, the placement orientation of the wafer positioning plate must be correct, and there are usually specific markings or features to indicate the correct orientation;

[0052] Stability: After placement, it should have sufficient stability and should not change position due to slight external forces or vibrations;

[0053] Size matching: The size of the chip positioning plate should be strictly matched with the size of the groove in the lower mold to ensure smooth embedding and not affect subsequent operations;

[0054] No damage: The chip positioning plate must not be damaged by collisions or scratches during placement, so as not to affect its positioning function.

[0055] S2. A plurality of wafer slots 51 are distributed on the wafer positioning plate 5, and a vacuum hole 52 is provided at the bottom of each wafer slot 51. The inverted wafer is fixed in the wafer slot 51 by vacuuming. In this state, the wafer pad is facing upward and fixed in the wafer slot. To achieve the above function, a vacuuming and heat blowing fixture 1 is used in this embodiment. The vacuuming and heat blowing fixture 1 can individually vacuum or heat blow the wafer slot through the vacuum hole.

[0056] S3. Place the stencil onto the chip pad, and then apply solder paste to the chip pad. The specific steps are as follows:

[0057] S31. Prepare the stencil: The purpose of the stencil is to control the application position and amount of solder paste. The stencil has openings that correspond to the chip pads.

[0058] S32. Cover with stencil: Place the stencil accurately above the chip pad, ensuring that the openings in the stencil are aligned with the chip pad.

[0059] S33. Applying Solder Paste: Apply solder paste to the chip pad through the openings in the stencil using appropriate tools (such as a squeegee or dispensing machine); this ensures that the solder paste is evenly applied to the designated area and controls the amount of solder paste used.

[0060] The advantage of applying solder paste after stencil application is that it allows for more precise control over the solder paste distribution, ensuring that each chip pad receives the appropriate amount of solder paste, thereby improving soldering quality and consistency.

[0061] Before using solder paste, stir it thoroughly to ensure its components are uniform, avoiding waste caused by uneven composition that prevents proper use of some paste. After each application, promptly clean any residual solder paste from the brush tool to ensure accurate control of the solder paste output for the next use.

[0062] S4. Place the BT board 3 on the lower mold 2, and then close the upper mold 4 on the lower mold 2. In this state, the BT board 3 is closed on the stencil and in contact with the chip pad. After the upper mold 4 and the lower mold 2 are closed, the BT board 3 and the chip pad are tightly attached.

[0063] S5. Vacuuming and Hot Air Blowing: The fixture 1 switches from vacuuming to hot air blowing mode, performing hot air reflow soldering on the BT board 3 and the wafer pad within the mold to complete die bonding. Specifically:

[0064] S51. Setting Parameters: Based on the characteristics of the solder paste, the materials of the chip and BT board, and the process requirements, set the temperature profile for hot air reflow soldering. This includes parameters such as the temperature and time of the preheating zone, the peak temperature and time of the reflow zone, and the cooling rate of the cooling zone.

[0065] S52. Preheating Stage: Start the equipment, hot air begins to blow out, and components enter the preheating zone. The purpose of this stage is to slowly increase the temperature, allowing the solvent in the solder paste to evaporate, reducing thermal shock, and simultaneously activating the flux.

[0066] S53, Reflow Stage: The temperature rises rapidly to the melting point of the solder paste, which melts and forms a good electrical and mechanical connection between the chip and the BT board.

[0067] S54. Cooling stage: After the reflow stage, cooling is performed to solidify the solder joints and form a strong connection.

[0068] S55. Inspection and Testing: After reflow soldering, remove the components for visual inspection to check for defects such as cold solder joints, short circuits, and solder balls. Simultaneously, electrical performance tests can be performed to ensure the quality and reliability of die bonding.

[0069] like Figures 1-3 As shown, a flip-chip bonding apparatus, applied in the aforementioned flip-chip bonding method, includes a vacuum and heat-blowing fixture 1, a lower mold 2, a BT plate 3, an upper mold 4, and a wafer positioning plate 5. The vacuum and heat-blowing fixture 1 can independently vacuum or heat-blow the wafer slot through vacuum holes. It includes a platform for placing the lower mold 2, with several small holes on the platform. A main pipe communicating with all the small holes is provided inside the vacuum and heat-blowing fixture 1. The fixture 1 has two air inlets connected to the main pipe, and a valve is provided at each air inlet. One air inlet is connected to a vacuuming device, and the other is connected to a heat-blowing device. During use, the valve controls only one air inlet to operate at a time. That is, when the vacuuming device is evacuating the mold, the air inlet of the heat-blowing device is closed, and the heat-blowing device does not need to be started; similarly, when the heat-blowing device is heat-blowing the mold, the air inlet of the vacuuming device is closed, and the vacuuming device does not need to be started.

[0070] As a key component, the lower mold 2 has a centrally located groove 21 that plays an important role. This groove 21 is specifically designed for embedding and placing the wafer positioning plate 5, providing precise space for the positioning and fixation of the wafer.

[0071] It is worth mentioning that the bottom surface of the groove 21 is carefully designed with several vent holes 22. These vent holes 22 are not randomly arranged, but precisely correspond to the small holes on the vacuuming and hot air blowing fixture 1. This ingenious design allows airflow to flow freely and smoothly between the small holes and the vent holes 22. Through this airflow interaction, key process steps such as vacuuming and heating are optimized, providing strong support for positioning and heating control during the manufacturing process.

[0072] The platform for the vacuum and hot air blowing fixture 1 is also ingeniously designed. It has a dedicated placement area for the lower mold 2, and several clamps are set within this area. These clamps can firmly fix the position of the lower mold 2, ensuring that the lower mold 2 will not move or shake at all during the entire manufacturing process, thereby guaranteeing the accuracy and stability of the processing.

[0073] Furthermore, four positioning pins 23 are distributed at the four corners of the lower mold 2. The BT plate 3 has positioning holes that mate with these four positioning pins 23, and the upper mold 4 also has corresponding positioning holes. Through these four positioning pins 23, the BT plate 3 and the upper mold 4 can achieve precise matching with the lower mold 2. This precise positioning mechanism not only ensures the accuracy of each component during assembly but also greatly improves production efficiency and reduces the generation of defective products due to positional deviations.

[0074] The surface of the wafer positioning plate 5 is covered with several wafer slots 51, providing dedicated placement positions for the wafers. Each wafer slot 51 is also carefully provided with vacuum holes 52 at its bottom. The distribution density of these vacuum holes 52 is lower than that of the vent holes 22 on the lower mold 2, allowing the wafer positioning plate 5 to be adsorbed into the groove of the lower mold 2, and allowing some gas to flow between the vacuum holes 52 and the vent holes 22.

[0075] As soon as the wafer is placed in the wafer tray 51, the vacuum equipment is activated. At this time, the vacuum hole 52 generates a strong suction force, which firmly fixes the wafer in the wafer tray 51, ensuring that the wafer will not shift or shake during subsequent processing, thus providing a strong guarantee for processing accuracy.

[0076] The chip is firmly positioned by the chip positioning plate 5, effectively preventing defects such as floating and offset, and also enabling mass transfer. This method uses solder paste to brush onto the chip, which effectively avoids the problem of uneven size and distribution of solder paste when brushing the stencil due to the unevenness of the BT board 3.

[0077] Once the BT board 3 is installed in place and the upper mold 4 and lower mold 2 are closed, the vacuum equipment stops operating, and the hot air blowing equipment starts immediately. The hot air blower heats the chip through the vacuum hole 52, causing the solder paste on the chip pad to melt rapidly.

[0078] It is worth mentioning that the gas flow between the vacuum hole 52 and the vent hole 22 plays a crucial regulating role in this process. Although the distribution density of the vacuum hole 52 is low, some gas can still flow between them. This gas exchange helps maintain the pressure balance inside the system and also promotes the uniform distribution of heat, improving heating efficiency and uniformity. The hot air heating method effectively avoids the temperature differences caused by the carrier absorbing heat during reflow soldering in traditional processes.

[0079] Once the solder paste has melted, the hot air blower stops operating, and the system enters the natural cooling phase. During this phase, the chip and BT board 3 gradually solidify and become fixed together under the action of the solder paste, forming a solid whole.

[0080] In this embodiment, the wafer and BT board are tightly bonded by the closing operation of the upper and lower molds. Subsequently, the original vacuum method is replaced by hot air reflow soldering, thereby completing the die bonding process efficiently and precisely. This novel die bonding method demonstrates significant advantages in improving die bonding efficiency and quality, and is expected to bring new development opportunities to related fields.

[0081] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0082] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0083] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flip-chip die bonding device, characterized in that... include: A vacuuming and hot air blowing fixture has a platform for placing a lower mold. The platform is provided with several small holes. The suction force or hot air blowing on the vacuuming and hot air blowing fixture acts on the lower mold through the small holes. The lower mold is provided with a number of ventilation holes corresponding to the small holes. The lower mold is provided with a wafer positioning plate. The suction force of the vacuum and hot air blowing fixture or the hot air blowing through the small holes and ventilation holes acts on the wafer positioning plate to position or heat the wafer positioning plate. A wafer positioning plate is provided with a plurality of wafer slots for placing wafers, and the wafer pads are placed in the wafer slots with the wafers facing upwards; the bottom of the wafer slots is provided with vacuum holes, and the distribution density of the vacuum holes is lower than that of the vent holes on the lower mold; a stencil is provided on the wafer positioning plate, and the openings of the stencil are aligned with the wafer pads so that solder paste is applied to the wafer pads. The upper mold presses against the BT board, bringing the BT board into contact with the chip pad coated with solder paste, and then closes with the lower mold to tightly bond the BT board and the chip pad.

2. The flip-chip die bonding device according to claim 1, characterized in that: The lower mold is provided with a groove, the wafer positioning plate is embedded in the groove, and the groove is provided with the vent hole.

3. The flip-chip die bonding device according to claim 1, characterized in that: Positioning pins are provided at the four corners of the lower mold, and positioning holes that are adapted to the positioning pins are provided on both the BT plate and the upper mold.

4. The flip-chip die bonding device according to claim 1, characterized in that: The vacuuming and hot air blowing fixture is equipped with a main pipe that is connected to all the small holes. The vacuuming and hot air blowing fixture has two air inlets that are connected to the main pipe. Each air inlet is equipped with a valve. One air inlet is connected to the vacuuming equipment, and the other air inlet is connected to the hot air blowing equipment.

5. A flip-chip bonding method, employing the flip-chip bonding apparatus according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Select a wafer positioning board of appropriate size and spacing according to the BT board pad design and wafer size, place the wafer positioning board on the lower mold, and fix the lower mold on the vacuum and hot air blowing fixture; Step 2: Place the wafer in the wafer slot of the wafer positioning plate with the wafer pad facing upwards, and use a vacuuming and hot air blowing fixture to fix the wafer in the wafer slot. Step 3: Select the corresponding stencil and cover the chip with the stencil. The openings on the stencil should correspond to the chip pads. Apply solder paste to the chip pads through the openings on the stencil. Step 4: Place the BT board on the lower mold, and cover the lower mold with the upper mold to achieve mold closing between the upper and lower molds, so that the BT board and the chip pad are tightly attached. Step 5: Vacuuming and hot air blowing. The fixture is switched from vacuuming to hot air blowing. Hot air is blown and reflow soldered on the BT board and the wafer pad in the mold to complete the die bonding.

6. The inverted fixing method according to claim 5, characterized in that: In step 1, the lower mold has a groove for placing a wafer positioning plate, and the wafer positioning plate is sized to match the groove. The wafer positioning plate and the bottom surface of the groove are tightly fitted under vacuum, and the wafer positioning plate is in a horizontal state.

7. The inverted fixing method according to claim 5, characterized in that: In step 2, a vacuum hole is provided in the wafer slot. The distribution density of the vacuum hole is lower than that of the vent hole on the lower mold. The vacuuming and hot air blowing fixture can separately vacuum or heat blow the wafer slot through the vacuum hole.

8. The inverted fixing method according to claim 5, characterized in that: In step 3, solder paste is evenly applied to the chip pad through the openings in the stencil using a scraper or dispensing machine.

9. The inverted fixing method according to claim 5, characterized in that: Step 5, hot air reflow soldering, requires the following steps: Step 51: Set parameters: Based on the characteristics of the solder paste, the materials of the chip and BT board, and the process requirements, set the temperature profile for hot air reflow soldering; Step 52, Reflow Stage: The temperature rises rapidly to the melting point of the solder paste, which melts and forms a good electrical and mechanical connection between the chip and the BT board; Step 53, Cooling Stage: After the reflow stage, cooling is performed to solidify the solder joints and form a strong connection; Step 54, Inspection and Testing: After reflow soldering is completed, remove the components for visual inspection to check for defects such as cold solder joints, short circuits, and solder ball defects.

10. The inverted fixing method according to claim 9, characterized in that: The parameters in step 51 include the temperature and time of the preheating zone, the peak temperature and time of the reflux zone, and the cooling rate of the cooling zone.

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