A method for packaging a stacked hall chip
By optimizing the Hall chip packaging process, including thinning and dicing, loading and baking, bonding, dispensing and curing, and three-stage temperature control, the problem of defect rate caused by stress during the molding process of Hall wafers was solved, achieving higher packaging yield and stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHIZHOU HISEMI ELECTRONICS TECH CO LTD
- Filing Date
- 2022-01-20
- Publication Date
- 2026-05-22
AI Technical Summary
Traditional packaging methods subject Hall effect wafers to stress during the molding process, resulting in a high defect rate, especially when packaging stacked Hall effect element chips.
The process involves thinning and dicing, loading and baking, first cleaning, bonding, second cleaning, dispensing and curing, molding, electroplating and rib cutting. Combined with a three-stage temperature control process and optimized dispensing technology, the stress on the Hall wafer is reduced by slow heating, constant temperature and slow cooling to ensure complete curing of the silver paste.
This improved the yield rate of Hall effect chips, reduced the possibility of bonding wire and silver paste breakage, and significantly enhanced packaging stability and product quality.
Smart Images
Figure CN114388692B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a packaging method, and more particularly to a method for packaging a stacked Hall effect chip. Background Technology
[0002] In IC chips, Hall effect elements are semiconductor devices that detect magnetic field signals based on the Hall effect. They can convert magnetic field signals into electrical signals, facilitating signal processing for various applications and having a wide range of applications. Currently, Hall effect chip packaging still uses traditional methods. Because the melting and solidification of the molding compound during the molding process exerts extremely strong stress on the Hall wafer in direct contact, the defect rate after chip packaging is relatively high. Moreover, the stress effect is even more pronounced when packaging stacked Hall effect chip chips using traditional packaging processes. In view of the above shortcomings, it is necessary to design a stacked Hall effect chip packaging method. Summary of the Invention
[0003] The purpose of this invention is to provide a stacked Hall chip packaging method that avoids damage to the Hall wafer caused by stress generated after the molding compound has cured, thereby improving the product yield.
[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for packaging a stacked Hall effect chip, the packaging method comprising the following steps:
[0005] 1) Thinning and dicing: First, the first wafer is thinned to 100um by grinding with a grinding machine, and the Hall wafer is thinned to 230um by grinding. An insulating film is attached to the back of the Hall wafer, and then the first wafer and the Hall wafer are cut into first wafer and Hall wafer respectively by a dicing machine.
[0006] 2) Loading and Baking: First, place the first wafer obtained in step 1) on a wafer mounter. Then, fix the first wafer to the top of the lead frame using a loading process and place it in an oven with pure nitrogen continuously purging for baking. After natural cooling, use a square rubber nozzle with a roughened, anti-fouling surface to place the Hall wafer on top of the first wafer. Finally, place the lead frame containing the first wafer and the Hall wafer into the oven and continuously purge with pure nitrogen. After baking, remove it and allow it to cool naturally to room temperature to obtain the Hall chip frame. The loading process is as follows:
[0007] a) Use a dispensing gun to extrude silver paste onto the top of the lead frame to form a dispensing position. The lifting time of the dispensing gun is 10-15ms and the lifting height is 550-600um.
[0008] b) Using a square rubber nozzle with a roughened, anti-contamination surface, pick up the first wafer and move it directly above the dispensing position. The square rubber nozzle presses the first wafer down to fit it against the dispensing position. The pressing time of the square rubber nozzle is 20-30ms and the pressing height is 10-20um.
[0009] 3) First cleaning: Place the Hall chip frame obtained in step 2) into a plasma cleaner for automatic cleaning for 30-35 minutes;
[0010] 4) Bonding: Place the Hall chip frame obtained in step 3) on a bonding machine equipped with 25um soft copper wires, and connect the first wafer and the Hall wafer with 25um soft copper wires using BSOB bonding. The first wafer is provided with solder joints, and the Hall wafer is provided with ball placement points. The Hall wafer is connected to the first wafer by leading wires from the side of the ball placement points using 25um soft copper wires.
[0011] 5) Second cleaning: Place the Hall chip frame obtained in step 4) into a plasma cleaner for automatic cleaning for 30-35 minutes;
[0012] 6) Dispensing and curing: Place the Hall chip frame obtained in step 5) onto the dispensing machine. The dispensing machine first drives the dispensing needle to move directly above the Hall wafer, then drives the dispensing needle to move down to contact the Hall wafer and dispense glue at the center of the Hall wafer. Finally, place the Hall chip frame in the oven for a three-stage temperature control process.
[0013] 7) Molding: Place the Hall chip frame obtained in step 6) on a molding machine to mold the chip frame. Then place the molded chip frame into a material box and bake it in an oven for 6-6.5 hours. The oven temperature is 170-175℃.
[0014] 8) Electroplating: First, the plastic-encapsulated chip frame obtained in step 7) is electroplated with tin, and then the plastic-encapsulated chip frame is placed in an oven and baked for 3-3.5 hours at a temperature of 150-155°C.
[0015] 9) Rib cutting: The encapsulated chip frame obtained in step 8) is continuously fed to the mold to cut the central rib and the single-sided carrier to obtain the Hall chip.
[0016] The invention is further improved as follows:
[0017] Furthermore, the baking process in step 1) is as follows:
[0018] a) The first stage is the heating stage, where the temperature rises from 50℃ to 173℃-177℃, and the heating time is 30-35 minutes.
[0019] b) The second stage is the constant temperature heating stage, with a temperature of 173℃-177℃ and a constant temperature time of 90-95min;
[0020] c) The third stage is the cooling stage, where the temperature drops from 173℃-177℃ to 50℃, and the cooling time is 25-30 minutes.
[0021] Furthermore, the three-stage temperature control process in step 6) is as follows:
[0022] a) The first stage is the heating stage, where the temperature rises from 50℃ to 148℃-152℃, and the heating time is 30-35 minutes.
[0023] b) The second stage is the constant temperature heating stage, with a temperature of 148℃-152℃ and a constant temperature time of 60-65min;
[0024] c) The third stage is the cooling stage, where the temperature drops from 148℃-152℃ to 50℃, and the cooling time is 30-35 minutes.
[0025] Furthermore, the dispensing needle includes a glue tube, a needle, and a rubber nozzle. The needle is located at the bottom of the glue tube, and the rubber nozzle is located at the bottom of the glue tube and outside the needle. The axis of the rubber nozzle coincides with the axis of the needle.
[0026] Furthermore, the rubber nozzle also includes a connecting part and a shaping part. The connecting part is located at the bottom of the rubber tube and is penetrated by the needle. The shaping part is located at the bottom of the connecting part and is integrally connected to the connecting part.
[0027] Furthermore, the height difference between the bottom surface of the shaping part and the bottom surface of the needle is 0.4-0.5mm.
[0028] Furthermore, the cross-sectional shape of the shaping part is trumpet-shaped.
[0029] Beneficial effects: Shortening the dispensing gun's lift-up time and increasing its lift-up height allows for the rapid formation of stable, raised silver paste droplets on the upper surface. Further control of the rectangular rubber nozzle's downward pressure (10-20µm) flattens the silver paste droplet, improving the welding effect and efficiency of the first wafer. Optimizing the baking process with heating, constant temperature, and cooling ensures complete silver paste curing while effectively reducing stress on the first wafer through slow heating and cooling, thus improving product yield. Dispensing is performed on the Hall effect wafer using a dispensing needle, with a trumpet-shaped shaping part on the needle shaping the dispensed adhesive. The adhesive is applied in smaller quantities at both ends of the Hall effect wafer and more in the middle. A three-stage isothermal process is used to cure the adhesive. The heating stage is longer and the temperature rises slowly, allowing the adhesive to gradually extend towards both ends of the Hall effect wafer under surface tension until it reaches equilibrium. The holding stage is a constant temperature stage, extending the holding time to ensure complete adhesive curing. Maintaining a longer cooling time and lowering the temperature to 50°C maximizes the release of stress generated during adhesive curing, thereby improving packaging stability. Furthermore, the three-stage temperature control technology maximizes stress release from molding and soldering process parameters, improving yield. The dispensing curing process applies adhesive to the Hall effect wafer, forming a unified whole with the adhesive, preventing stress from the cured molding compound from damaging the Hall effect wafer and further improving product yield. Attached Figure Description
[0030] Figure 1 A flowchart of the present invention is shown.
[0031] Figure 2 A schematic diagram of the dispensing needle structure of the present invention is shown.
[0032] In the diagram: 1. Glue cartridge; 2. Needle; 3. Rubber nozzle; 301. Connecting part; 302. Detailed Implementation
[0033] Example 1
[0034] like Figure 1 , Figure 2 As shown, a method for packaging a stacked Hall effect chip includes the following steps:
[0035] 1) Thinning and dicing: First, the first wafer is thinned to 100um by grinding with a grinding machine, and the Hall wafer is thinned to 230um by grinding. An insulating film is attached to the back of the Hall wafer, and then the first wafer and the Hall wafer are cut into first wafer and Hall wafer respectively by a dicing machine.
[0036] 2) Loading and Baking: First, place the first wafer obtained in step 1) on a wafer mounter. Then, fix the first wafer to the top of the lead frame using a loading process and place it in an oven with pure nitrogen continuously purging for baking. After natural cooling, use a square rubber nozzle with a roughened, anti-fouling surface to place the Hall wafer on top of the first wafer. Finally, place the lead frame containing the first wafer and the Hall wafer into the oven and continuously purge with pure nitrogen. After baking, remove it and allow it to cool naturally to room temperature to obtain the Hall chip frame. The loading process is as follows:
[0037] a) Use a dispensing gun to extrude silver paste onto the top of the lead frame to form a dispensing position. The lifting time of the dispensing gun is 10ms and the lifting height is 550um.
[0038] b) Using a square rubber nozzle with a roughened, anti-contamination surface, pick up the first wafer and move it directly above the dispensing position. The square rubber nozzle presses the first wafer down to fit it against the dispensing position. The pressing time of the square rubber nozzle is 20ms and the pressing height is 10um.
[0039] 3) First cleaning: Place the Hall chip frame obtained in step 2) into a plasma cleaner for automatic cleaning for 30 minutes;
[0040] 4) Bonding: Place the Hall chip frame obtained in step 3) on a bonding machine equipped with 25um soft copper wires, and connect the first wafer and the Hall wafer with 25um soft copper wires using BSOB bonding. The first wafer is provided with solder joints, and the Hall wafer is provided with ball placement points. The Hall wafer is connected to the first wafer by leading wires from the side of the ball placement points using 25um soft copper wires.
[0041] 5) Second cleaning: Place the Hall chip frame obtained in step 4) into a plasma cleaner for automatic cleaning for 30 minutes;
[0042] 6) Dispensing and curing: Place the Hall chip frame obtained in step 5) onto the dispensing machine. The dispensing machine first drives the dispensing needle to move directly above the Hall wafer, then drives the dispensing needle to move down to contact the Hall wafer and dispense glue at the center of the Hall wafer. Finally, place the Hall chip frame in the oven for a three-stage temperature control process.
[0043] 7) Molding: Place the Hall chip frame obtained in step 6) on a molding machine to mold the chip frame. Then place the molded chip frame into a material box and bake it in an oven at 170°C for 6 hours.
[0044] 8) Electroplating: First, the plastic-encapsulated chip frame obtained in step 7) is electroplated with tin, and then the plastic-encapsulated chip frame is placed in an oven and baked for 3 hours at a temperature of 150°C.
[0045] 9) Rib cutting: The encapsulated chip frame obtained in step 8) is continuously fed to the mold to cut the central rib and the single-sided carrier to obtain the Hall chip.
[0046] The baking process in step 1) is as follows:
[0047] a) The first stage is the heating stage, where the temperature rises from 50℃ to 173℃, and the heating time is 30 minutes;
[0048] b) The second stage is the constant temperature heating stage, with a temperature of 173℃ and a constant temperature time of 90min;
[0049] c) The third stage is the cooling stage, where the temperature drops from 173℃ to 50℃ in 25 minutes.
[0050] The three-stage temperature control process in step 6) is as follows:
[0051] a) The first stage is the heating stage, where the temperature rises from 50℃ to 148℃ in 30 minutes;
[0052] b) The second stage is the constant temperature heating stage, with a temperature of 148°C and a holding time of 60 minutes;
[0053] c) The third stage is the cooling stage, where the temperature drops from 148℃ to 50℃ over a period of 30 minutes.
[0054] The dispensing needle of the present invention includes a glue cartridge 1, a needle 2, and a rubber nozzle 3. The needle 2 is disposed at the bottom of the glue cartridge 1, and the rubber nozzle 3 is disposed at the bottom of the glue cartridge 1 and located outside the needle 2. The axis of the rubber nozzle 3 coincides with the axis of the needle 2. The rubber nozzle 3 also includes a connecting part 301 and a shaping part 302. The connecting part 301 is disposed at the bottom of the glue cartridge 1 and is penetrated by the needle 2. The shaping part 302 is located at the bottom of the connecting part 301. The shaping part 302 and the connecting part... The 301 components are integrated and connected. The height difference between the bottom surface of the shaping part 302 and the bottom surface of the needle 2 is 0.4mm. The cross-sectional shape of the shaping part 302 is trumpet-shaped. When dispensing, the shaping part 302 contacts the Hall wafer and undergoes a deformation of 0.1mm, which ensures that the adhesive does not leak out of the shaping part and ensures the stability of dispensing. The axes of the needle 2, the rubber nozzle 3 and the Hall wafer are respectively aligned, which ensures that the adhesive falls at the center of the Hall wafer, thereby ensuring the uniformity of dispensing.
[0055] Example 2
[0056] like Figure 1 , Figure 2 As shown, a method for packaging a stacked Hall effect chip includes the following steps:
[0057] 1) Thinning and dicing: First, the first wafer is thinned to 100um by grinding with a grinding machine, and the Hall wafer is thinned to 230um by grinding. An insulating film is attached to the back of the Hall wafer, and then the first wafer and the Hall wafer are cut into first wafer and Hall wafer respectively by a dicing machine.
[0058] 2) Loading and Baking: First, place the first wafer obtained in step 1) on a wafer mounter. Then, fix the first wafer to the top of the lead frame using a loading process and place it in an oven with pure nitrogen continuously purging for baking. After natural cooling, use a square rubber nozzle with a roughened, anti-fouling surface to place the Hall wafer on top of the first wafer. Finally, place the lead frame containing the first wafer and the Hall wafer into the oven and continuously purge with pure nitrogen. After baking, remove it and allow it to cool naturally to room temperature to obtain the Hall chip frame. The loading process is as follows:
[0059] a) Use a dispensing gun to extrude silver paste onto the top of the lead frame to form a dispensing position. The lifting time of the dispensing gun is 15ms and the lifting height is 600um.
[0060] b) Using a square rubber nozzle with a roughened, anti-contamination surface, pick up the first wafer and move it directly above the dispensing position. The square rubber nozzle presses the first wafer down to fit it against the dispensing position. The pressing time of the square rubber nozzle is 30ms and the pressing height is 20um.
[0061] 3) First cleaning: Place the Hall chip frame obtained in step 2) into a plasma cleaner for automatic cleaning for 35 minutes;
[0062] 4) Bonding: Place the Hall chip frame obtained in step 3) on a bonding machine equipped with 25um soft copper wires, and connect the first wafer and the Hall wafer with 25um soft copper wires using BSOB bonding. The first wafer is provided with solder joints, and the Hall wafer is provided with ball placement points. The Hall wafer is connected to the first wafer by leading wires from the side of the ball placement points using 25um soft copper wires.
[0063] 5) Second cleaning: Place the Hall chip frame obtained in step 4) into a plasma cleaner for automatic cleaning for 35 minutes;
[0064] 6) Dispensing and curing: Place the Hall chip frame obtained in step 5) onto the dispensing machine. The dispensing machine first drives the dispensing needle to move directly above the Hall wafer, then drives the dispensing needle to move down to contact the Hall wafer and dispense glue at the center of the Hall wafer. Finally, place the Hall chip frame in the oven for a three-stage temperature control process.
[0065] 7) Molding: Place the Hall chip frame obtained in step 6) on a molding machine to mold the chip frame. Then place the molded chip frame into a material box and bake it in an oven at 175°C for 6.5 hours.
[0066] 8) Electroplating: First, the plastic-encapsulated chip frame obtained in step 7) is electroplated with tin, and then the plastic-encapsulated chip frame is placed in an oven and baked for 3.5 hours at a temperature of 155°C.
[0067] 9) Rib cutting: The encapsulated chip frame obtained in step 8) is continuously fed to the mold to cut the central rib and the single-sided carrier to obtain the Hall chip.
[0068] The baking process in step 1) is as follows:
[0069] a) The first stage is the heating stage, where the temperature rises from 50℃ to 177℃ in 35 minutes;
[0070] b) The second stage is the constant temperature heating stage, with a temperature of 177℃ and a constant temperature time of 95 minutes;
[0071] c) The third stage is the cooling stage, where the temperature drops from 177℃ to 50℃ over a period of 30 minutes.
[0072] The three-stage temperature control process in step 6) is as follows:
[0073] a) The first stage is the heating stage, where the temperature rises from 50℃ to 152℃ in 35 minutes;
[0074] b) The second stage is the constant temperature heating stage, with a temperature of 152℃ and a constant temperature time of 65min;
[0075] c) The third stage is the cooling stage, where the temperature drops from 152℃ to 50℃ over a period of 35 minutes.
[0076] The dispensing needle of the present invention includes a glue cartridge 1, a needle 2, and a rubber nozzle 3. The needle 2 is disposed at the bottom of the glue cartridge 1, and the rubber nozzle 3 is disposed at the bottom of the glue cartridge 1 and located outside the needle 2. The axis of the rubber nozzle 3 coincides with the axis of the needle 2. The rubber nozzle 3 also includes a connecting part 301 and a shaping part 302. The connecting part 301 is disposed at the bottom of the glue cartridge 1 and is penetrated by the needle 2. The shaping part 302 is located at the bottom of the connecting part 301. The shaping part 302 and the connecting part... The 301 components are integrated. The height difference between the bottom surface of the shaping part 302 and the bottom surface of the needle 2 is 0.5mm. The cross-sectional shape of the shaping part 302 is trumpet-shaped. When dispensing, the shaping part 302 contacts the Hall wafer and undergoes a deformation of 0.2mm, which ensures that the adhesive does not leak out of the shaping part and ensures the stability of dispensing. The axes of the needle 2, the rubber nozzle 3 and the Hall wafer are respectively aligned, which ensures that the adhesive falls at the center of the Hall wafer, thereby ensuring the uniformity of dispensing.
[0077] Example 3
[0078] like Figure 1 , Figure 2 As shown, a method for packaging a stacked Hall effect chip includes the following steps:
[0079] 1) Thinning and dicing: First, the first wafer is thinned to 100um by grinding with a grinding machine, and the Hall wafer is thinned to 230um by grinding. An insulating film is attached to the back of the Hall wafer, and then the first wafer and the Hall wafer are cut into first wafer and Hall wafer respectively by a dicing machine.
[0080] 2) Loading and Baking: First, place the first wafer obtained in step 1) on a wafer mounter. Then, fix the first wafer to the top of the lead frame using a loading process and place it in an oven with pure nitrogen continuously purging for baking. After natural cooling, use a square rubber nozzle with a roughened, anti-fouling surface to place the Hall wafer on top of the first wafer. Finally, place the lead frame containing the first wafer and the Hall wafer into the oven and continuously purge with pure nitrogen. After baking, remove it and allow it to cool naturally to room temperature to obtain the Hall chip frame. The loading process is as follows:
[0081] a) Use a dispensing gun to extrude silver paste onto the top of the lead frame to form a dispensing position. The lifting time of the dispensing gun is 13ms and the lifting height is 570um.
[0082] b) Using a square rubber nozzle with a roughened, anti-contamination surface, pick up the first wafer and move it directly above the dispensing position. The square rubber nozzle presses the first wafer down to fit it against the dispensing position. The pressing time of the square rubber nozzle is 25ms and the pressing height is 15um.
[0083] 3) First cleaning: Place the Hall chip frame obtained in step 2) into a plasma cleaner for automatic cleaning for 33 minutes;
[0084] 4) Bonding: Place the Hall chip frame obtained in step 3) on a bonding machine equipped with 25um soft copper wires, and connect the first wafer and the Hall wafer with 25um soft copper wires using BSOB bonding. The first wafer is provided with solder joints, and the Hall wafer is provided with ball placement points. The Hall wafer is connected to the first wafer by leading wires from the side of the ball placement points using 25um soft copper wires.
[0085] 5) Second cleaning: Place the Hall chip frame obtained in step 4) into a plasma cleaner for automatic cleaning for 33 minutes;
[0086] 6) Dispensing and curing: Place the Hall chip frame obtained in step 5) onto the dispensing machine. The dispensing machine first drives the dispensing needle to move directly above the Hall wafer, then drives the dispensing needle to move down to contact the Hall wafer and dispense glue at the center of the Hall wafer. Finally, place the Hall chip frame in the oven for a three-stage temperature control process.
[0087] 7) Molding: Place the Hall chip frame obtained in step 6) on a molding machine to mold the chip frame. Then place the molded chip frame into a material box and bake it in an oven at 173°C for 6.3 hours.
[0088] 8) Electroplating: First, the plastic-encapsulated chip frame obtained in step 7) is electroplated with tin, and then the plastic-encapsulated chip frame is placed in an oven and baked for 3.3 hours at a temperature of 153°C.
[0089] 9) Rib cutting: The encapsulated chip frame obtained in step 8) is continuously fed to the mold to cut the central rib and the single-sided carrier to obtain the Hall chip.
[0090] The baking process in step 1) is as follows:
[0091] a) The first stage is the heating stage, where the temperature rises from 50℃ to 175℃ in 33 minutes;
[0092] b) The second stage is the constant temperature heating stage, with a temperature of 175℃ and a constant temperature time of 93min;
[0093] c) The third stage is the cooling stage, where the temperature drops from 175℃ to 50℃ in 27 minutes.
[0094] The three-stage temperature control process in step 6) is as follows:
[0095] a) The first stage is the heating stage, where the temperature rises from 50℃ to 150℃ in 33 minutes;
[0096] b) The second stage is the constant temperature heating stage, with a temperature of 150℃ and a constant temperature time of 63min;
[0097] c) The third stage is the cooling stage, where the temperature drops from 150℃ to 50℃ in 33 minutes.
[0098] The dispensing needle of the present invention includes a glue cartridge 1, a needle 2, and a rubber nozzle 3. The needle 2 is disposed at the bottom of the glue cartridge 1, and the rubber nozzle 3 is disposed at the bottom of the glue cartridge 1 and located outside the needle 2. The axis of the rubber nozzle 3 coincides with the axis of the needle 2. The rubber nozzle 3 also includes a connecting part 301 and a shaping part 302. The connecting part 301 is disposed at the bottom of the glue cartridge 1 and is penetrated by the needle 2. The shaping part 302 is located at the bottom of the connecting part 301. The shaping part 302 and the connecting part 301 are connected. The 01 components are connected as one unit. The height difference between the bottom surface of the shaping part 302 and the bottom surface of the needle 2 is 0.45mm. The cross-sectional shape of the shaping part 302 is trumpet-shaped. When dispensing, the shaping part 302 contacts the Hall wafer and undergoes a deformation of 0.18mm, which ensures that the glue does not leak out of the shaping part and also ensures the stability of dispensing. The axes of the needle 2, the rubber nozzle 3 and the Hall wafer are respectively coincident, which can ensure that the glue falls at the center of the Hall wafer, thereby ensuring the uniformity of dispensing.
[0099] Table 1. Details of Production Quantity and Testing Quantity
[0100]
[0101] Table 1 shows that the traditional packaging process and the process of this invention are basically the same in terms of packaging yield. However, in terms of testing yield, the yield of the process of this invention is nearly 2 percentage points higher than that of the traditional process, which is a significant improvement.
[0102] Table 2 Detailed List of Testing Items
[0103]
[0104] Table 2 shows that, in terms of leakage current detection, continuity detection, and Hall saturation voltage, the process of this invention uses a loading process and a three-stage temperature control process, which releases the stress on the silver paste and bonding wires between the first wafer and the Hall wafer, reducing the possibility of bonding wire and silver paste breakage. Therefore, the number of defects in leakage current detection, continuity detection, and Hall saturation voltage is much lower than that of the traditional process. In the critical Gaussian voltage detection project, the process of this invention injects adhesive onto the Hall wafer and uses a three-stage temperature control process for curing, which can effectively protect the Hall wafer and release stress, preventing damage to the Hall wafer caused by stress generated during chip encapsulation. This represents a significant improvement over the traditional process.
[0105] This invention is not limited to the specific embodiments described above. Any modifications made by those skilled in the art based on the above concept without creative effort are within the scope of protection of this invention.
Claims
1. A method for packaging a stacked Hall effect chip, characterized in that... The encapsulation method includes the following steps: 1) Thinning and dicing: First, the first wafer is thinned to 100um by grinding with a grinding machine, and the Hall wafer is thinned to 230um by grinding. Insulating adhesive is pasted on the back of the Hall wafer, and then the first wafer and the Hall wafer are cut into first wafer and Hall wafer respectively by a dicing machine. 2) Loading and Baking: First, place the first wafer obtained in step 1) on a wafer mounter. Then, fix the first wafer to the top of the lead frame using a loading process and place it in an oven with pure nitrogen continuously purging for baking. After natural cooling, use a square rubber nozzle with a roughened, anti-fouling surface to place the Hall wafer on top of the first wafer. Finally, place the lead frame containing the first wafer and the Hall wafer into the oven and continuously purge with pure nitrogen. After baking, remove it and allow it to cool naturally to room temperature to obtain the Hall chip frame. The loading process is as follows: a) Use a dispensing gun to extrude silver paste onto the top of the lead frame to form a dispensing position. The lifting time of the dispensing gun is 10-15ms and the lifting height is 550-600um. b) Using a square rubber nozzle with a roughened, anti-contamination surface, pick up the first wafer and move it directly above the dispensing position. The square rubber nozzle presses the first wafer down to fit it against the dispensing position. The pressing time of the square rubber nozzle is 20-30ms and the pressing height is 10-20um. 3) First cleaning: Place the Hall chip frame obtained in step 2) into a plasma cleaner for automatic cleaning for 30-35 minutes; 4) Bonding: Place the Hall chip frame obtained in step 3) on a bonding machine equipped with 25um soft copper wires, and connect the first wafer and the Hall wafer with 25um soft copper wires using BSOB bonding. The first wafer is provided with solder joints, and the Hall wafer is provided with ball placement points. The Hall wafer is connected to the first wafer by leading wires from the side of the ball placement points using 25um soft copper wires. 5) Second cleaning: Place the Hall chip frame obtained in step 4) into a plasma cleaner for automatic cleaning for 30-35 minutes; 6) Dispensing and curing: Place the Hall chip frame obtained in step 5) onto the dispensing machine. The dispensing machine first drives the dispensing needle to move directly above the Hall wafer, then drives the dispensing needle to move down to contact the Hall wafer and dispense glue at the center of the Hall wafer. Finally, place the Hall chip frame in the oven for a three-stage temperature control process. 7) Molding: Place the Hall chip frame obtained in step 6) on a molding machine to mold the chip frame. Then place the molded chip frame into a material box and bake it in an oven for 6-6.5 hours. The oven temperature is 170-175℃. 8) Electroplating: First, the plastic-encapsulated chip frame obtained in step 7) is electroplated with tin, and then the plastic-encapsulated chip frame is placed in an oven and baked for 3-3.5 hours at a temperature of 150-155°C. 9) Rib cutting: The encapsulated chip frame obtained in step 8) is continuously fed to the mold to cut the central rib and the single-sided carrier to obtain the Hall chip.
2. The stacked Hall chip packaging method as described in claim 1, characterized in that... The baking process in step 1) is as follows: a) The first stage is the heating stage, where the temperature rises from 50℃ to 173℃-177℃, and the heating time is 30-35 minutes; b) The second stage is the constant temperature heating stage, with a temperature of 173℃-177℃ and a constant temperature time of 90-95min; c) The third stage is the cooling stage, where the temperature drops from 173℃-177℃ to 50℃, and the cooling time is 25-30 minutes.
3. The stacked Hall chip packaging method as described in claim 1, characterized in that... The three-stage temperature control process in step 6) is as follows: a) The first stage is the heating stage, where the temperature rises from 50℃ to 148℃-152℃, and the heating time is 30-35 minutes. b) The second stage is the constant temperature heating stage, with a temperature of 148℃-152℃ and a constant temperature time of 60-65min; c) The third stage is the cooling stage, where the temperature drops from 148℃-152℃ to 50℃, and the cooling time is 30-35 minutes.
4. The stacked Hall chip packaging method as described in claim 1, characterized in that... The dispensing needle includes a glue tube, a needle, and a rubber nozzle. The needle is located at the bottom of the glue tube, and the rubber nozzle is located at the bottom of the glue tube and outside the needle. The axis of the rubber nozzle coincides with the axis of the needle.
5. The stacked Hall chip packaging method as described in claim 4, characterized in that... The rubber nozzle also includes a connecting part and a shaping part. The connecting part is located at the bottom of the rubber tube and is penetrated by the needle. The shaping part is located at the bottom of the connecting part and is integrally connected to the connecting part.
6. The stacked Hall chip packaging method as described in claim 5, characterized in that... The height difference between the bottom surface of the shaping part and the bottom surface of the needle is 0.4-0.5mm.
7. The stacked Hall chip packaging method as described in claim 5, characterized in that... The cross-sectional shape of the shaping part is trumpet-shaped.