Method for precise pressure calibration of a power semiconductor wire bonder

Abstract

The application provides a method for accurately calibrating pressure of a power semiconductor wire bonding machine, comprising the following steps: S1: preparation, placing a pressure sensor directly below a welding head E wedge, and controlling the welding head to drop to a fixed position; S2: recording, recording the current pressure sensor value, which is the weight value of the welding head at this time; S3: adjusting current, adjusting the current in the coil of the lower pressure generator to a reverse current; S4: increasing current, gradually increasing the current from small to large, and observing the value of the pressure sensor at the same time, at this time, the value of the pressure sensor will gradually decrease. The method for accurately calibrating pressure of the power semiconductor wire bonding machine can obtain the direct relationship between current and pressure through the pressure sensor, accurately control the pressure by changing the current in the control, and accurately cooperate with the ultrasonic wave to complete the pressure step output in the welding process, thereby improving the welding quality.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging and testing technology, and in particular to a method for accurately calibrating the pressure of a power semiconductor wire bonding machine. Background Technology

[0002] The production process of power semiconductor products is divided into three stages: design, manufacturing, and packaging and testing. In the packaging and testing stage, the main processing technologies are Die Bond and Wire Bond. The main purpose of wire bonding is to use an ultrasonic device to weld thick aluminum wires (100um-500um) to the bonding points between the chip and the lead frame under the action of external force. During the wire bonding process, the wedge of the welding head needs to press the aluminum wire with a certain pressure, and then the wedge conducts ultrasonic waves to perform welding. Furthermore, it is necessary to precisely control the pressure pressing the aluminum wire during the welding process to ensure the reliability of the welded product.

[0003] Traditional ultrasonic wire bonding equipment uses a spring mechanism and a displacement mechanism to set the pressure. The entire control is based on the basic principle and lacks adjustability. The pressure is directly related to the downward displacement. However, insufficient pressure during the process can lead to poor soldering, while excessive pressure can damage the wafer surface. To solve the above problems, we propose a method for accurately calibrating the pressure of a power semiconductor wire bonding machine. Summary of the Invention

[0004] The purpose of this invention is to provide a method for accurately calibrating the pressure of a power semiconductor wire bonding machine. This method can obtain the direct relationship between current and pressure through a pressure sensor, and precisely control the pressure by changing the current during control. In the welding process, it can accurately coordinate with ultrasonic waves to complete the pressure step output, thereby improving the welding quality.

[0005] The embodiments of the present invention are implemented as follows:

[0006] This invention provides a method for accurately calibrating the pressure of a power semiconductor wire bonding machine, comprising the following steps:

[0007] S1: Preliminary Preparations

[0008] Place the pressure sensor directly below the E-cutting blade of the welding head to control the welding head to descend to a fixed position;

[0009] S2: Record

[0010] Record the current pressure sensor value, which is the weight of the welding head at this time.

[0011] S3: Adjust current

[0012] Adjust the current in the coil of the pressure generator to a reverse current;

[0013] S4: Increase current

[0014] Gradually increase the current from small to large while observing the pressure sensor readings. The pressure sensor readings will gradually decrease.

[0015] S5: Zeroing

[0016] When the pressure sensor reading is 0, record the current value at that time;

[0017] S6: Reduce current

[0018] With the pressure sensor value in S5 set to 0 as the base value, the current is gradually decreased. For every 0.5N increase in pressure by the pressure sensor, the corresponding current value is recorded, until the current reaches 20N.

[0019] S7: Calibration complete

[0020] Fit the data, record it in a table, and store it in the controller to complete the calibration.

[0021] Optionally, the welding head includes a displacement sensor, a pressure generator, an ultrasonic transducer, an aluminum wire feed tube, a chopping knife, and a cutting knife. The displacement sensor and the pressure generator are rigidly connected to the drive arm as a whole, while the ultrasonic transducer, the aluminum wire feed tube, the chopping knife, and the cutting knife are flexibly connected to the drive arm as a whole, and can move up and down slightly relative to the displacement sensor and the pressure generator.

[0022] Optionally, the displacement sensor can detect the relative position of the ultrasonic transducer, aluminum wire feed tube, chopping knife, cutting knife, and the overall displacement sensor and pressure generator.

[0023] Optionally, the cutter is installed close to the chopping blade but not in contact with it, and the aluminum wire feeding tube is installed close to the other side of the chopping blade but not in contact with it. The aluminum wire passes through the aluminum wire feeding tube and is placed directly below the end of the chopping blade.

[0024] Optionally, the ultrasonic transducer and the chopping blade are tightly fixedly connected, the chopping blade passes through one end of the ultrasonic transducer, and the ultrasonic transducer is adapted to a matching ultrasonic generator.

[0025] Optionally, a coil is provided in the middle of the lower pressure generator, and the coil in the middle of the lower pressure generator is electrically connected to a control circuit.

[0026] Optionally, in step S1, for the welding head to reach the fixed position, the bottom end of the welding head's cutting edge must first contact the pressure sensor directly above it, and then it continues to descend, with the distance measured by the displacement sensor.

[0027] Optionally, in step S5, when the value of the pressure sensor is 0, the downward pressure generator counteracts the weight of the welding head under the action of reverse current.

[0028] Optionally, in step S6, the current value is recorded whenever the pressure sensor increases by 0.5N, up to a point of 20N.

[0029] Optionally, the displacement sensor is calibrated at a distance of two millimeters.

[0030] The beneficial effects of this invention include: This invention provides a method for accurately calibrating the pressure of a power semiconductor wire bonding machine. The method involves setting the coil current of the pressure generator to a reverse current and gradually increasing the current while observing the pressure sensor readings. The pressure sensor readings gradually decrease until they reach zero. At this point, the pressure sensor readings are offset by the weight of the welding head under the reverse current, thus establishing a base current value. The current is gradually decreased, and the pressure sensor readings and current readings are recorded. The data is then fitted, and the direct relationship between current and pressure is obtained through the pressure sensor. In the control process, the pressure is precisely controlled by changing the current. During the welding process, the pressure can be precisely coordinated with ultrasonic waves to complete the pressure step output, improving welding quality. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the welding head structure of a method for accurately calibrating the pressure of a power semiconductor wire bonding machine according to the present invention.

[0033] Icons: 1. Displacement sensor; 2. Downward pressure generator; 3. Ultrasonic transducer; 4. Aluminum wire feed tube; 5. Cleaver; 6. Cutting knife. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0036] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," not that the structure must be completely horizontal, but can be slightly tilted.

[0037] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] like Figure 1 As shown, this embodiment of the invention provides a method for accurately calibrating the pressure of a power semiconductor wire bonding machine, comprising the following steps:

[0039] S1: Preliminary Preparations

[0040] Place the pressure sensor directly below the welding head E-cleaver 5 and control the welding head to descend to a fixed position;

[0041] S2: Record

[0042] Record the current pressure sensor value, which is the weight of the welding head at this time.

[0043] S3: Adjust current

[0044] Adjust the current in the coil of the downpressure generator 2 to a reverse current;

[0045] S4: Increase current

[0046] Gradually increase the current from small to large while observing the pressure sensor readings. The pressure sensor readings will gradually decrease.

[0047] S5: Zeroing

[0048] When the pressure sensor reading is 0, record the current value at that time;

[0049] S6: Reduce current

[0050] With the pressure sensor value in S5 set to 0 as the base value, the current is gradually decreased. For every 0.5N increase in pressure by the pressure sensor, the corresponding current value is recorded, until the current reaches 20N.

[0051] S7: Calibration complete

[0052] Fit the data, record it in a table, and store it in the controller to complete the calibration.

[0053] In one embodiment of the present invention, the welding head includes a displacement sensor 1, a pressure generator 2, an ultrasonic transducer 3, an aluminum wire feed tube 4, a chopping knife 5, and a cutting knife 6. The displacement sensor 1 and the pressure generator 2 are rigidly connected to the drive arm as a whole, while the ultrasonic transducer 3, the aluminum wire feed tube 4, the chopping knife 5, and the cutting knife 6 are softly connected to the drive arm as a whole, and can move up and down slightly relative to the displacement sensor 1 and the pressure generator 2.

[0054] As one embodiment of the present invention, the displacement sensor 1 can detect the relative position of the ultrasonic transducer 3, the aluminum wire feeding tube 4, the chopping knife 5, the cutting knife 6 relative to the displacement sensor 1 and the downward pressure generator 2.

[0055] In one embodiment of the present invention, the cutter 6 is installed close to the chopping blade 5 but not in contact with it, and the aluminum wire feeding tube 4 is installed close to the other side of the chopping blade 5 but not in contact with it. The aluminum wire passes through the aluminum wire feeding tube 4 and is placed directly below the end of the chopping blade 5.

[0056] In one embodiment of the present invention, the ultrasonic transducer 3 and the cutting blade 5 are tightly fixedly connected, the cutting blade 5 penetrates one end of the ultrasonic transducer 3, and the ultrasonic transducer 3 is adapted to be equipped with a matching ultrasonic generator.

[0057] In one embodiment of the present invention, a coil is provided in the middle of the pressure generator 2, and the coil in the middle of the pressure generator 2 is electrically connected to a control circuit.

[0058] In one embodiment of the present invention, when the welding head is to reach a fixed position in step S1, the bottom end of the welding head's cutting blade 5 is first brought into contact with the pressure sensor directly above it, and then it continues to descend, with the distance measured by the displacement sensor 1.

[0059] In one embodiment of the present invention, when the value of the pressure sensor is 0 in step S5, the downward pressure generator 2 counteracts the weight of the welding head under the action of reverse current.

[0060] In one embodiment of the present invention, in step S6, the current value is recorded whenever the pressure sensor increases by 0.5N, up to a value of 20N.

[0061] As one embodiment of the present invention, the displacement sensor 1 is calibrated to a distance of two millimeters.

[0062] It should be noted that this invention is a method for accurately calibrating the pressure of a power semiconductor wire bonding machine. The method involves setting the coil current of the pressure generator 2 to a reverse current and gradually increasing the current while observing the pressure sensor readings. The pressure sensor readings gradually decrease, and when the reading reaches 0, the reverse current counteracts the weight of the welding head, thus establishing a base current value. The current is then gradually decreased, and the pressure sensor and current values ​​are recorded. The data is then fitted, and the direct relationship between current and pressure is obtained through the pressure sensor. In the control process, the pressure is precisely controlled by changing the current. During the welding process, the pressure can be precisely coordinated with ultrasonic waves to achieve pressure step output, thereby improving welding quality.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the present 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 method for accurately calibrating the pressure of a power semiconductor wire bonding machine, characterized in that, Includes the following steps: S1: Preliminary Preparations Place the pressure sensor directly below the welding head E cleaver (5) and control the welding head E to descend to a fixed position; S2: Record Record the current pressure sensor value, which is the weight of the welding head E at this time. S3: Adjust current Adjust the current in the coil of the pressure generator (2) to a reverse current; S4: Increase current Gradually increase the current from small to large while observing the pressure sensor readings. The pressure sensor readings will gradually decrease. S5: Zeroing When the pressure sensor value is 0, the pressure generator (2) at this time cancels the weight of the welding head E under the action of reverse current, and the current value at this time is recorded. S6: Reduce current Using the current value of 0 from the pressure sensor in S5 as the base value, gradually decrease the current, and record the corresponding current value every time the pressure sensor increases by 0.5N. Up to 20N; S7: Calibration complete Fit the data, record it in a table, and store it in the controller to complete the calibration; By obtaining the direct relationship between current and pressure through a pressure sensor, the pressure can be precisely controlled by changing the current during the control process. In the welding process, it can be precisely coordinated with ultrasonic waves to complete the pressure step output, thereby improving the welding quality.

2. The method for accurately calibrating the pressure of a power semiconductor wire bonding machine according to claim 1, characterized in that: The welding head E includes a displacement sensor (1), a pressure generator (2), an ultrasonic transducer (3), an aluminum wire feed tube (4), a chopping knife (5), and a cutting knife (6). The displacement sensor (1) and the pressure generator (2) are rigidly connected to the drive arm as a whole, while the ultrasonic transducer (3), the aluminum wire feed tube (4), the chopping knife (5), and the cutting knife (6) are softly connected to the drive arm as a whole, and can move up and down slightly relative to the displacement sensor (1) and the pressure generator (2).

3. The method for accurately calibrating the pressure of a power semiconductor wire bonding machine according to claim 2, characterized in that: The displacement sensor (1) can detect the relative position of the ultrasonic transducer (3), aluminum wire feeding tube (4), cleaver (5), cutter (6) relative to the displacement sensor (1) and the pressure generator (2).

4. The method for accurately calibrating the pressure of a power semiconductor wire bonding machine according to claim 2, characterized in that: The cutter (6) is installed close to the chopping blade (5) but not in contact with it, and the aluminum wire feeding tube (4) is installed close to the other side of the chopping blade (5) but not in contact with it. The aluminum wire passes through the aluminum wire feeding tube (4) and is placed directly below the end of the chopping blade (5).

5. The method for accurately calibrating the pressure of a power semiconductor wire bonding machine according to claim 2, characterized in that: The ultrasonic transducer (3) and the chopping knife (5) are tightly fixedly connected. The chopping knife (5) passes through one end of the ultrasonic transducer (3). The ultrasonic transducer (3) is adapted to a matching ultrasonic generator.

6. The method for accurately calibrating the pressure of a power semiconductor wire bonding machine according to claim 2, characterized in that: A coil is provided in the middle of the lower pressure generator (2), and the coil in the middle of the lower pressure generator (2) is electrically connected to a control circuit.

7. The method for accurately calibrating the pressure of a power semiconductor wire bonding machine according to claim 1, characterized in that: In step S1, for the welding head E to reach the fixed position, the bottom end of the cutting edge (5) of the welding head E should first contact the pressure sensor directly above it, and then continue to descend, and the distance should be measured by the displacement sensor (1).

8. The method for accurately calibrating the pressure of a power semiconductor wire bonding machine according to claim 7, characterized in that: The displacement sensor (1) is calibrated to a distance of two millimeters.

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