Joining device

Abstract

To control the height of an object to be joined at high precision.SOLUTION: A joining device comprises: a heater chip 2 pressing an object to be joined from above to heat the same; a temperature sensor 3 detecting a temperature of the heater chip 2; a power source 8 feeding an electric current to the heater chip 2 to generate heat; a position derivation part 6 deriving a position in a height direction of the heater chip 2 corresponding to the temperature of the heater chip 2; and a lift control part 7 performing displacement control in the height direction of the heater chip 2 so as to cancel a displacement magnitude in the height direction of the heater chip 2 caused by heat expansion based on a derivation result of the position derivation part 6.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a pulse heat bonding apparatus.

Background Art

[0002] In a pulse heat bonding apparatus, the temperature of a heater tip is detected by a thermocouple attached to the electrode (heater tip) that presses the objects to be bonded, and the current supplied to the heater tip is controlled so that this temperature becomes a preset temperature.

[0003] During bonding, sinking occurs due to the melting of the objects to be bonded, so the height of the objects to be bonded changes. Depending on the product, it may be required to make the height of the objects to be bonded uniform. Therefore, conventionally, the displacement of the heater tip in the height direction was detected and the height direction of the heater tip was controlled to achieve a uniform height of the objects to be bonded (see Patent Document 1).

[0004] However, the heater tip, which becomes high temperature due to the generated Joule heat, expands thermally, so the position in the height direction of the contact surface with the objects to be bonded changes. When performing micro displacement control on the order of μm as disclosed in Patent Document 1, the influence of the thermal expansion of the heater tip cannot be ignored, and displacement control with high accuracy cannot be performed.

[0005] Conventionally, as a technique for reducing the influence of the thermal expansion of the heater tip, a bonding system disclosed in Patent Document 2 is known. In the bonding system disclosed in Patent Document 2, first, the heater tip is heated from room temperature to temperature TM1, and one of the two objects to be bonded held by the heater tip is heated. With the heater tip in the state of being heated to temperature TM1, the heater tip is lowered to bring the two objects to be bonded into contact. While maintaining the height of the heater tip at that time, the heater tip is further heated to temperature TM2 (TM1 < TM2) to bond the two objects to be bonded.

[0006] In the bonding system disclosed in Patent Document 2, by contacting two objects to be bonded while the temperature is raised from room temperature to temperature TM1, the influence of thermal expansion caused by the temperature rise from room temperature to temperature TM1 can be eliminated, and the amount of thermal expansion of the heater chip caused by the temperature rise from temperature TM1 to temperature TM2 can be kept small (e.g., a few μm).

[0007] However, even the technology disclosed in Patent Document 2 cannot eliminate the effects of thermal expansion on the order of μm, so when performing the above-mentioned micro-displacement control, the effects of thermal expansion of the heater chip cannot be ignored, and displacement control cannot be performed with high precision. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2007-173522 A [Patent Document 2] JP 2017-34282 A Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the above-mentioned problems, and has an object to provide a bonding apparatus that can control the height of the workpieces with higher accuracy than ever before. [Means for solving the problem]

[0010] The bonding apparatus of the present invention includes a heater chip configured to press and heat an object to be bonded from above, a temperature sensor configured to detect the temperature of the heater chip, a power source configured to supply a current to the heater chip to generate heat, a position deriving unit configured to derive a position in a height direction of the heater chip corresponding to the temperature of the heater chip, and a lifting control unit configured to control a displacement in a height direction of the heater chip so as to offset a displacement amount in a height direction of the heater chip due to thermal expansion based on a result derived by the position deriving unit. The position deriving unit derives the position of the heater chip in the height direction from the temperature detected by the temperature sensor based on a known relationship between the temperature of the heater chip and the position of the heater chip in the height direction. It is characterized by the above. In one configuration example of the bonding apparatus of the present invention, the lift control unit controls the displacement of the heater chip in the height direction during a heating period in which the heater chip is heated to heat the workpiece and during a cooling period in which the heater chip is cooled to cool the workpiece after the heating period. Uko The present invention is characterized by the following: 。 Effect of the Invention

[0011] According to the present invention, by providing a position deriving unit and a lifting control unit, it is possible to control the height of the workpiece with higher accuracy than in the past. In the present invention, it is possible to realize a high-quality finished appearance in soldering or ACF (Anisotropic Conductive Film) bonding, and to obtain highly reliable bonding. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing the relationship between the temperature of a heater chip and the position in the height direction of the heater chip. [Diagram 2] FIG. 2 is a block diagram showing the configuration of a joining device according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a flowchart illustrating the operation of the joining device according to the embodiment of the present invention. [Figure 4] FIG. 4 is an enlarged cross-sectional view of the heater chip and the workpiece when the temperature rise starts. [Diagram 5]FIG. 5 is a diagram showing an example of a temperature profile. [Figure 6] FIG. 6 is an enlarged cross-sectional view of the heater chip and the object being bonded during bonding. [Figure 7] FIG. 7 is an enlarged cross-sectional view of the heater chip and the workpiece after bonding is completed. [Figure 8] FIG. 8 is a diagram showing another example of a temperature profile. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Principle of the invention] The temperature T of the heater chip and the height position Z of the center of the heater chip (position of the lower tip) due to thermal expansion have a linear relationship, for example, as shown in the following equation (Figure 1). Z = a T + b (1)

[0014] a is the slope and b is the intercept. Since the constants a and b vary depending on the object to be bonded and the bonding device, if the constants a and b are determined and set by prior experiments for the object to be bonded and the bonding device, the position in the height direction can be corrected in real time during bonding, and the effect of thermal expansion of the heater chip due to temperature rise can be eliminated. However, Figure 1 and formula (1) are only one example of the relationship between temperature T and position Z, and the present invention is not limited to this. The relationship between temperature T and position Z obtained by prior experiments may be stored.

[0015] [Example] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 2 is a block diagram showing the configuration of a bonding device according to an embodiment of the present invention. The bonding device is composed of a head unit 1, a heater tip 2, a temperature sensor 3 for detecting the temperature of the heater tip 2, a lifting mechanism 4 for moving the heater tip 2 up and down by an electric motor, a displacement sensor 5 for detecting the amount of sinking of the heater tip 2, a position deriving unit 6 for deriving the position in the height direction of the heater tip 2 (the position of the lower end) corresponding to the temperature of the heater tip 2, a lifting control unit 7 for controlling the lifting and lowering of the heater tip 2, a power source 8 for supplying current to the heater tip 2, a power source control unit 9 for controlling the amount of current flowing from the power source 8 to the heater tip 2, and a holding table 10 for placing the objects to be bonded.

[0016] A heater chip 2 made of a high resistance material such as molybdenum is attached to the lower end of the head unit 1. A temperature sensor 3 made of a thermocouple is fixed near the tip of the heater chip 2. In addition, the head unit 1 is provided with a lifting mechanism 4 and a displacement sensor 5.

[0017] The operation of the bonding apparatus of this embodiment will be described below. Fig. 3 is a flow chart for explaining the operation of the bonding apparatus, and Fig. 4 is an enlarged cross-sectional view of the heater chip 2 and the object to be bonded when the temperature rise starts.

[0018] An electric conductor 21 is formed on a glass plate 20 placed on a holding table 10 of the bonding device. Meanwhile, solder 22 is printed in advance on a portion to be bonded of a terminal 23 made of a conductor. When the portion to be bonded of the electric conductor 21 and the portion to be bonded of the terminal 23 are positioned to face each other and the terminal 23 is placed on the electric conductor 21, for example, when a user issues an instruction to start bonding, the lift control unit 7 controls the lift mechanism 4 of the head unit 1 to lower the heater tip 2 (step S100 in FIG. 3).

[0019] As a result, the objects to be bonded (conductor 21, solder 22, and terminal 23) are sandwiched and pressed from above and below by the heater chip 2 and the holder 10 (FIG. 4). At this time, a load cell (not shown) is provided in the head unit 1 so that the magnitude of the load applied to the objects to be bonded can be detected. The lifting control unit 7 controls the lifting mechanism 4 so that the detected load becomes a predetermined value.

[0020] The power supply control unit 9 controls the amount of current supplied from the power supply 8 to the heater chip 2 so that the temperature of the heater chip 2 detected by the temperature sensor 3 coincides with the temperature indicated by a preset temperature profile (step S101 in FIG. 3). The pulse current supplied from the power supply 8 flows, for example, from terminal 20a to terminal 20b of the heater chip 2, causing the heater chip 2 to generate heat. An example of the temperature profile is shown in FIG. 5.

[0021] When the heater chip 2 generates heat, as shown in FIG. 6, the heater chip 2 thermally expands downward in the height direction, increasing its displacement. The position derivation unit 6 calculates the latest position Z in the height direction of the center of the heater chip 2, which corresponds to the latest temperature T of the heater chip 2 detected by the temperature sensor 3, by using the linear equation of equation (1) (step S102 in FIG. 3). The position derivation unit 6 also calculates the position Z0 in the height direction of the center of the heater chip 2 at the start of heating, which corresponds to the temperature T0 of the heater chip 2 detected by the temperature sensor 3 at the start of heating, by using the linear equation of equation (1).

[0022] Then, the lift control unit 7 controls the lift mechanism 4 to lift the heater chip 2, and performs height displacement control so that the absolute value of the amount of lift of the heater chip 2 from the start of heating due to this lift is equal to the absolute value of the difference (amount of lowering) between the height position Z0 of the center part of the heater chip 2 at the start of heating and the latest position Z, thereby correcting the height position of the heater chip 2 (step S103 in FIG. 3). That is, the heater chip 2 is moved to the opposite side to the thermal expansion of the heater chip 2, which causes the lower side to swell.

[0023] The lifting mechanism 4 is controlled by applying a pulse signal to an electric motor (not shown) of the lifting mechanism 4. The lifting mechanism 4 lifts the heater chip 2 by, for example, X μm per pulse of the drive signal. In this way, the displacement of the heater chip 2 in the height direction due to thermal expansion can be offset.

[0024] The bonding apparatus repeatedly performs the processes of steps S101 to S103 until the current supply stop timing determined by the temperature profile. Next, when it is time to stop power supply determined by the temperature profile (YES in step S104 in FIG. 3), the power supply control unit 9 stops power supply from the power supply 8 to the heater chip 2 (step S105 in FIG. 3).

[0025] When the current supply is finished, a cooling period begins in which the heater chip 2 is lowered and the bonded object is cooled while being pressurized by the heater chip 2. Even during this cooling period, the heater chip 2 is still at a higher temperature than when the heating started, and so its position in the height direction is displaced due to thermal expansion.

[0026] Therefore, similarly to step S102, the position derivation unit 6 calculates the latest position Z in the height direction of the heater chip 2 corresponding to the latest temperature T of the heater chip 2 detected by the temperature sensor 3 by using formula (1) (step S106 in FIG. 3).

[0027] Then, the lifting control unit 7 controls the lifting mechanism 4 to lift the heater chip 2, and corrects the heightwise position of the heater chip 2 by controlling the heightwise displacement so that the absolute value of the amount of rise of the heater chip 2 from the start of heating due to this rise is equal to the absolute value of the difference (amount of descent) between the heightwise position Z0 of the center of the heater chip 2 at the start of heating and the latest position Z (step S107 in Figure 3).

[0028] The lift control unit 7 repeats the processes of steps S106 and S107 until a certain time has elapsed since the power supply was stopped and the cooling period has ended, or until the temperature of the heater chip 2 has dropped to a predetermined temperature and the cooling period has ended.

[0029] After the cooling period ends (YES in step S108 in FIG. 3), the lift control unit 7 controls the lift mechanism 4 to lift the heater tip 2 and separate it from the objects to be bonded (step S109 in FIG. 3). In this way, bonding of the objects to be bonded is completed. FIG. 7 shows the state at the end of bonding. It can be seen that the height of the solder 22 has changed compared to the state at the start of the temperature rise shown in FIG. 4.

[0030] As described above, in this embodiment, by correcting the height direction position of the heater chip 2 in real time during bonding, it is possible to eliminate the influence of thermal expansion of the heater chip 2 due to temperature rise, and to realize a uniform height of the bonded objects. In this embodiment, since the height direction position of the heater chip 2 is corrected even during the cooling period, the sinking amount of the bonded objects can be controlled with high precision.

[0031] In this embodiment, the heating is stopped by stopping the current supply to the heater chip 2 at the predetermined timing to stop the current supply after the heater chip 2 is heated to a constant temperature as shown in Fig. 5. However, the current supply may be controlled so that the temperature gradually decreases without immediately stopping the current supply at the end of the heating period. The temperature profile in this case is shown in Fig. 8.

[0032] In this embodiment, the position derivation unit 6 calculates the position Z of the heater chip 2 corresponding to the temperature T of the heater chip 2 by formula (1), but as described above, Fig. 1 and formula (1) are one example of the relationship between the temperature T and the position Z. The relationship between the temperature T and the position Z obtained from the results of a preliminary test measurement may be registered in advance in the position derivation unit 6, and the position derivation unit 6 may derive the position Z of the heater chip 2 corresponding to the temperature T of the heater chip 2 based on this known relationship.

[0033] In this embodiment, for the sake of simplicity, the micro-displacement control disclosed in Patent Document 1 is not described. However, it goes without saying that the micro-displacement control in which the displacement in the height direction of the heater tip 2 is detected by the displacement sensor 5 and the elevation control unit 7 controls the heater tip 2 in the height direction to make the height of the workpiece uniform, and the correction of the height direction position in this embodiment may be performed simultaneously.

[0034] The position deriving unit 6, lift control unit 7, and power supply control unit 9 described in this embodiment can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface with the outside. In such a computer, a program for realizing the joining method of the present invention is stored in the storage device. The CPU executes the processing described in this embodiment according to the program stored in the storage device. [Industrial Applicability]

[0035] The present invention can be applied to a pulse heat type joining device. [Explanation of symbols]

[0036] 1...head unit, 2...heater chip, 3...temperature sensor, 4...lifting mechanism, 5...displacement sensor, 6...position derivation unit, 7...lifting control unit, 8...power supply, 9...power supply control unit, 10...holding base.

Claims

1. A heater tip configured to press and heat the object to be bonded from above; a temperature sensor configured to detect a temperature of the heater tip; a power source configured to provide current to the heater chip to generate heat; a position deriving unit configured to derive a position in a height direction of the heater chip corresponding to a temperature of the heater chip; a lift control unit configured to control a displacement of the heater chip in the height direction so as to offset a displacement amount of the heater chip in the height direction caused by thermal expansion based on a result derived by the position derivation unit, The bonding apparatus is characterized in that the position derivation unit derives the height position of the heater chip from the temperature detected by the temperature sensor based on a known relationship between the temperature of the heater chip and the height position of the heater chip.

2. The joining device according to claim 1, The bonding apparatus is characterized in that the lifting control unit controls a displacement of the heater tip in a height direction during a heating period in which the heater tip is heated to heat the workpiece, and during a cooling period in which the heater tip is cooled to cool the workpiece after the heating period.

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