A low-pressure high-precision pulse heating bonding device and bonding method

Abstract

The present invention relates to the field of bonding technology, specifically a small pressure high-precision pulse heating bonding device and bonding method, which aims to solve the technical problem that the existing bonding device cannot meet the requirements of small pressure high-precision bonding. The bonding device includes a frame, a servo motor and a vertically arranged slide rail are fixed on the frame, and a vertically arranged screw rod is rotatably installed, the servo motor drives the screw rod to rotate, a nut is mounted on the screw rod, an upper slider and a lower slider are slidably embedded in the slide rail, the nut is fixedly connected to the upper slider, a cylinder is fixed on the upper slider, the piston rod of the cylinder is vertically downward and fixedly connected to the lower slider, a bonding head is installed at the lower end of the piston rod, the cylinder is connected to a solenoid valve that controls its opening and closing and an electric proportional valve that controls its preset pressure, and the piston rod of the cylinder is in a maximum extension state; and also includes a controller, the controller is connected to the solenoid valve, the electric proportional valve and the servo motor. The bonding method adopts two-stage control of the preset force of the cylinder size and two-stage control of the speed of the servo motor.

Description

Technical Field

[0001] The invention relates to the field of bonding technology, in particular to a small-pressure high-precision pulse heating bonding device and a bonding method. Background Art

[0002] Bonding is a wire bonding method in the chip production process. It is generally used to connect the internal circuit of the chip with the package pin or the gold-plated copper foil of the circuit board with gold wire or aluminum wire before packaging. The current bonding pressure is generally at least 30N, but with the advancement of technology, the width of the FPC lead has developed to 0.0025mm, the bonding area has been reduced to 3.5mm×0.35mm, the minimum bonding pressure required has been reduced to 5N, and the maximum bonding pressure cannot exceed 10N, otherwise the FPC lead width will become thinner and the impact force will be too large, which will easily break the lead. The current bonding is divided into two methods: constant temperature bonding and pulse bonding. Compared with constant temperature bonding, pulse bonding has the advantages of higher temperature control accuracy, stronger controllability, faster temperature rise and fall speed, and more stable constant temperature state. Therefore, pulse bonding is mostly used in high-precision bonding occasions. The existing high-pressure pulse bonding is generally driven by a 40mm cylinder alone, and the bonding head is contacted with the product through the movement of the cylinder piston rod to complete the bonding. The pressure control accuracy of this large-diameter cylinder cannot reach ±1N, and cannot meet the requirements of small pressure bonding. If the 40mm large-diameter cylinder is replaced with a 25mm small-diameter cylinder, although the accuracy can be met, the pulse bonding needs to be equipped with transformers and copper braids and other structures, which have the following problems: First, when the bonding head starts to move downward, the copper braid provides a large extrusion force, and the maximum static friction between the cylinder piston rod and the guide device will be very large, and the small-diameter cylinder will find it difficult to complete the telescopic work; second, the bonding head moves slowly under the small pressure of the small-diameter cylinder, resulting in low bonding efficiency; third, under the action of the cylinder constant force, when the bonding head at the end of the piston rod contacts the product, the bonding head has a large speed and momentum, and the momentum is lost in a short time after contacting the product, the impact force generated will be very large, and the lead wire is easily broken; fourth, due to the variable force caused by the swing of the copper braid, the telescopic action of the piston rod of the small-diameter cylinder will be affected, making it unstable when telescopic, affecting the bonding accuracy.

[0003] In order to improve the bonding efficiency, there is already a patent application with application number "201110449205.4" and name "Bonding device for the pressure unit of the fully automatic COG bonding machine". It adopts a double-stroke action. The servo motor first descends at a relatively fast speed, and then the servo motor stops when it is about to contact the product, and the cylinder is started to extend and retract for bonding. This structure belongs to a constant temperature and high pressure bonding structure. If this structure is used for pulse low pressure bonding, although it can improve the bonding efficiency, the first, third and fourth technical problems mentioned above still exist. In addition, for a small-bore cylinder, when it is started to extend and retract when it is about to contact the product, the bonding pressure will fluctuate and be unstable, making it difficult to meet the bonding requirements. Summary of the invention

[0004] The invention aims to solve the technical problem that the existing bonding device cannot meet the requirements of low pressure and high precision bonding.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A small-pressure high-precision pulse heating bonding device comprises a frame, a servo motor and a vertically arranged slide rail are fixed on the frame, the servo motor is connected to a lead screw pair, the servo motor drives the lead screw of the lead screw pair to rotate, an upper slider and a lower slider are slidably embedded in the slide rail, the nut of the lead screw pair is fixedly connected to the upper slider, a cylinder is fixed on the upper slider, a piston rod of the cylinder is vertically downward and fixedly connected to the lower slider, a bonding head is installed at the lower end of the piston rod, the cylinder is connected to an electromagnetic valve for controlling its opening and closing and an electrical proportional valve for controlling its output pressure, and the piston rod of the cylinder is in a state of maximum extension; and a controller is also included, the controller is connected to the electromagnetic valve, the electrical proportional valve and the servo motor.

[0007] A bonding method of the above bonding device comprises the following steps:

[0008] S1, open the solenoid valve of the cylinder, and preset a pressure F1 to the cylinder through the electrical proportional valve. F1 ensures that when the cylinder is started, the piston rod can overcome the maximum static friction between the lower slider and the slide rail, and is always in the longest extension state without retraction;

[0009] S2, control the servo motor to make the upper slider and the lower slider slide downward along the slide rail at a speed of V1;

[0010] S3, after the lower slider starts to slide but before the bonding head contacts the product, reduce the preset force of the cylinder to F2, where F2 corresponds to the bonding pressure setting;

[0011] S4, when the bonding head is 3-5mm away from the product, control the servo motor to reduce the speed V1 to V2. V2 and F2 ensure that the instantaneous pressure of the bonding head when it just touches the product is less than the maximum bonding pressure that the product can withstand. Keep V2 and F2 to make the bonding head continue to move downward until the bonding head completely fits the surface of the product. Then the servo motor stops and the bonding head is bonded with the required bonding pressure.

[0012] S5. After bonding is completed, the control cylinder and servo motor are reset and wait for the next bonding.

[0013] The beneficial effects of the present invention are:

[0014] 1) The small-pressure high-precision pulse heating bonding device provided by the present invention is provided with a cylinder, a servo motor, a slide rail, and two slide blocks. The servo motor controls the stroke of the bonding head so that the bonding head contacts the product. The bonding pressure is controlled by the cylinder. The up and down movements of various structures are all integrated on the same slide rail. The structural integration is high and the assembly accuracy is also high.

[0015] 2) The low-pressure high-precision pulse heating bonding device provided by the present invention is additionally provided with an electrical proportional valve, which can control the cylinder to be bonded in two sections. The first section is a high pressure, which can overcome the maximum static friction force, and the second section is a low pressure, which can meet the bonding pressure requirements;

[0016] 3) The low-pressure high-precision pulse heating bonding device provided by the present invention cooperates with the cylinder and the servo motor, and the cylinder is in the maximum extension state throughout the whole process, which avoids the unstable pressure caused by starting the cylinder when it is about to contact the product, and also avoids the excessive impact force caused by the accelerated extension of the cylinder piston under the action of constant force. At the same time, it also solves the technical problem that the extension and retraction of the piston rod of a small-bore cylinder is easily affected by the copper braid;

[0017] 4) The bonding method provided by the present invention first presets a large pressure on the cylinder through an electric proportional valve so that the piston rod can overcome the maximum static friction force and move downward, and then adjusts the preset pressure of the cylinder to a small pressure that matches the bonding pressure, which can solve the technical problem that a small-diameter cylinder is difficult to extend and retract during pulse bonding;

[0018] 5) The bonding method provided by the present invention first allows the servo motor to move downward at a relatively high speed through a controller, so that the bonding head can descend faster, thereby improving the bonding efficiency. Then, the servo motor is allowed to move downward at a relatively low speed, which cooperates with the small pressure of the second section of the cylinder to avoid excessive impact force of the bonding head when contacting the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 is an axonometric view of the bonding device of the present invention;

[0021] Figure 2 is a front view of the bonding device of the present invention;

[0022] Figure 3 It is a left side view of the bonding device of the present invention.

[0023] In the figure:

[0024] 1┄ frame; 2┄ servo motor; 3┄ slide rail; 4┄ screw rod; 5┄ nut; 6┄ upper slider; 7┄ lower slider; 8┄ cylinder; 9┄ piston rod; 10┄ bonding head. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] Reference Figures 1 to 3 A low-pressure high-precision pulse heating bonding device of the present invention comprises a frame 1, a servo motor 2 and a vertically arranged slide rail 3 are fixed on the frame 1, the servo motor 2 is connected to a lead screw pair, the servo motor 2 drives the lead screw 4 of the lead screw pair to rotate, the slide rail 3 is slidably embedded with an upper slider 6 and a lower slider 7, the nut 5 of the lead screw pair is fixedly connected to the upper slider 6, a cylinder 8 is fixed on the upper slider 6, a piston rod 9 of the cylinder 8 is vertically downward and fixedly connected to the lower slider 7, a bonding head 10 is installed at the lower end of the piston rod 9, the cylinder 8 is connected to an electromagnetic valve for controlling its opening and closing and an electrical proportional valve for controlling its output pressure, and the piston rod 9 of the cylinder 8 is in a maximum extension state; it also comprises a controller, the controller is connected to the electromagnetic valve, the electrical proportional valve and the servo motor 2. When in use, the servo motor 2 works, driving the screw rod 4 to rotate, and the nut 5 moves axially along the screw rod 4 under the circumferential limit of the slider and the slide rail 3, thereby driving the upper slider 6 to move up and down. Since the piston rod 9 of the cylinder 8 is always in the maximum extension state, the lower slider 7 also slides up and down with the upper slider 6. This device is used for pulse bonding heating with low pressure and high precision. In the specific design, a small-bore cylinder 8 that is compatible with the bonding pressure is selected. Since the small-bore cylinder 8 has poor anti-interference ability, a low-friction cylinder 8 and a low-friction guide rail are used, which should be a relatively easy design for people in this field.

[0027] The bonding device provided by the present invention is compared with the bonding device provided by the patent application with the existing application number "201110449205.4" and the name "Bonding device of the pressure unit for the fully automatic COG bonding machine", and the main structural differences are: a. The cylinder 8 of the present application is always in the maximum extension state; b. The cylinder 8 of the present application is connected to an electrical proportional valve. The above two differences lead to completely different methods of use of the bonding device of the present invention and the device. With regard to point a, although the structure of the cylinder 8 of the present application is the structure of an ordinary cylinder 8, the piston rod 9 does not extend, and the cylinder 8 is mainly used to ensure the bonding pressure, which is an innovative point of the present application; with regard to point b, the present application is additionally provided with an electrical proportional valve, and two pressures are applied to the cylinder 8 during the operation of the cylinder 8, so as to solve the first technical problem in the background technology, which is another innovative point of the present application.

[0028] A bonding method of the above bonding device comprises the following steps:

[0029] S1. Open the solenoid valve of the cylinder 8, and preset a pressure F1 for the cylinder 8 through the electrical proportional valve. F1 ensures that the piston rod 9 can overcome the maximum static friction between the lower slider 7 and the slide rail 3 when the cylinder 8 is started, and is always in the longest extension state and will not retract. In specific implementation, F1 is obtained through debugging, which is a conventional test method for people in this field.

[0030] S2, control the servo motor 2 to make the upper slider 6 and the lower slider 7 slide downward along the slide rail 3 at a speed V1. The value of V1 is relatively large, and the main purpose is to improve the bonding efficiency.

[0031] S3. After the lower slider 7 starts to slide but before the bonding head 10 contacts the product, the preset force of the cylinder 8 is reduced to F2. F2 corresponds to the bonding pressure setting. Here, the change of the preset pressure only needs to be completed after the movement starts but before the product is contacted. It is preferred to adjust the preset pressure of the cylinder 8 when the product is about to be contacted, so that most of the operation maintains a high pressure and has stronger anti-interference ability.

[0032] S4, when the bonding head 10 is 3-5mm away from the product, the servo motor 2 is controlled to operate, and the speed V1 is reduced to V2. V2 and F2 ensure that the instantaneous pressure of the bonding head 10 when it just contacts the product is less than the maximum bonding pressure that the product can withstand. V2 and F2 are maintained to make the bonding head 10 continue to move downward until the servo motor 2 stops operating when the bonding head 10 completely fits the surface of the product, and the bonding head 10 is bonded with the required bonding pressure. Here, completely fitting the surface of the product means that the piston rod of the cylinder is in the maximum extension state but the cylinder body has no limiting force on the piston. Personnel in this field can use the servo motor to drive the cylinder to this state through debugging. Here, the momentum of the bonding head 10 becomes 0 in a short time after contacting the product. If the speed is large before contacting the product, then according to Ft=mv-mv', it can be concluded that the impact force will be very large, so the speed is reduced from V1 to V2 to reduce the momentum difference, thereby reducing the impact force. Here, the F in Ft corresponding to the momentum difference is impact force - preset pressure of cylinder 8 - gravity of bonding head 10. Therefore, if the required F is constant, if the preset pressure of cylinder 8 becomes smaller, the impact force will also become smaller. This is one of the reasons why the preset pressure of cylinder 8 is reduced from F1 to F2. Another reason is to meet the requirements of bonding pressure. In specific implementation, how much bonding pressure can be achieved by the preset force of cylinder 8 with a specific value is related to factors such as system errors of different devices. This corresponding relationship needs to be obtained through debugging, which should be an easy experimental method for people in this field.

[0033] S5. After bonding is completed, the control cylinder 8 and servo motor 2 are reset and wait for the next bonding.

[0034] Furthermore, the electric proportional valve uses current control to replace the commonly used voltage control, thereby achieving the effect of precise subdivision. In this way, its stability is guaranteed by program control, which is very suitable for high-precision pressure control of small pressures.

[0035] The bonding method of the present invention has three main innovative points: a. The cylinder 8 operates under two pressure stages; b. The servo motor 2 operates under two pressure stages. The following is a detailed description of the creativity of the above innovative points by comparing with the prior art:

[0036] The most common method currently used is to use a single cylinder 8 for driving. For small-pressure pulse bonding, if the cylinder 8 is directly replaced with a cylinder 8 of a small bore, the bonding is completed by extending and retracting the piston rod 9 of the cylinder 8. The most conventional method is to directly preset the cylinder 8 to a preset pressure corresponding to the small bonding pressure, and then let the piston rod 9 move downward under the action of a constant force. However, this cannot be achieved because the copper braid on the pulse bonding device will give a larger squeezing force to the pressing block when the gas is at the highest position, making the maximum static friction force at this moment very large. The small preset force of the cylinder 8 is not enough to overcome the maximum static friction force, and the cylinder 8 piston rod 9 will retract, which is not feasible.

[0037] For the bonding device provided in the patent application with application number "201110449205.4" and name "Bonding device for the pressure unit of the fully automatic COG bonding machine", the most direct idea is to replace the cylinder 8 with a small-bore cylinder 8, and the bonding head 10 with a pulse bonding head 10. The most common approach that can be thought of with the aid of this device is also a double-stroke operation, but this operation still has the three technical problems mentioned in the background technology, namely, points 1, 3, and 4, and is not feasible.

[0038] The present application overcomes conventional design thinking and allows both the cylinder 8 and the servo motor 2 to operate in two stages. The high pressure in the first stage of the cylinder 8 overcomes the first technical problem of the background technology, and the low pressure in the second stage of the cylinder 8 is used to meet the low pressure requirement of bonding; the rapid descent of the servo motor 2 in the first stage is used to solve the second technical problem of the background technology, and the low speed in the second stage of the servo motor 2 cooperates with the low pressure in the second stage of the cylinder 8 to solve the third technical problem of the background technology; the stroke of the servo motor 2 is from the beginning to the bonding head 10 contacting the product, and the two-stage combination of the two-stage of the cylinder 8 solves the fourth technical problem together, and also avoids the phenomenon of unstable pressure caused by the expansion and contraction of the cylinder 8 adjacent to the product.

[0039] Therefore, compared with the existing bonding technology, the present application overcomes the conventional design thinking and can simultaneously solve the four technical problems of the background technology, so that small-pressure and high-precision pulse bonding can be better completed.

[0040] The same or similar numbers in the drawings of the embodiments correspond to the same or similar parts; in the description of the present application, it should be understood that if the terms "upper", "lower", "left", "right", etc. indicate an orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0041] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A bonding method for a bonding device, characterized in that: The bonding device comprises a frame (1), a servo motor (2) and a vertically arranged slide rail (3) are fixed on the frame (1), the servo motor (2) is connected to a lead screw pair, the servo motor (2) drives a lead screw (4) of the lead screw pair to rotate, an upper slider (6) and a lower slider (7) are slidably embedded in the slide rail (3), a nut (5) of the lead screw pair is fixedly connected to the upper slider (6), a cylinder (8) is fixed on the upper slider (6), a piston rod (9) of the cylinder (8) is vertically downward and fixedly connected to the lower slider (7), a bonding head (10) is installed at the lower end of the piston rod (9), the cylinder (8) is connected to an electromagnetic valve for controlling its opening and closing and an electrical proportional valve for controlling its preset pressure, and the piston rod (9) of the cylinder (8) is in a maximum extension state; and a controller is also included, the controller is connected to the electromagnetic valve, the electrical proportional valve and the servo motor (2), and the bonding method comprises the following steps: S1, open the solenoid valve of the cylinder, and preset a pressure F1 to the cylinder (8) through the electrical proportional valve, F1 ensures that the piston rod (9) of the cylinder (8) can overcome the maximum static friction between the lower slider (7) and the slide rail (3) when the cylinder (8) is started, and is always in the longest extension state without retraction; S2, controlling the servo motor (2) to move so that both the upper slider (6) and the lower slider (7) slide downward along the slide rail (3) at a speed V1; S3, after the lower slider (7) starts to slide but before the bonding head (10) contacts the product, the preset force of the cylinder (8) is reduced to F2, where F2 corresponds to the bonding pressure setting; S4, when the bonding head (10) is 3-5 mm away from the product, the servo motor (2) is controlled to operate, and the speed V1 is reduced to V2. V2 and F2 ensure that the instantaneous pressure of the bonding head (10) when it just contacts the product is less than the maximum bonding pressure that the product can withstand. V2 and F2 are maintained to allow the bonding head (10) to continue to move downward until the bonding head (10) is completely in contact with the surface of the product. The servo motor (2) stops operating, and the bonding head (10) is bonded at the required bonding pressure. S5. After bonding is completed, the control cylinder (8) and the servo motor (2) are reset and wait for the next bonding.

2. The bonding method according to claim 1, characterized in that: The electric proportional valve is controlled by current.

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