Component mounting device and component mounting method

Abstract

To provide a component mounting apparatus and a component mounting method that can reliably mount components on a substrate while applying a constant mounting load to the components.SOLUTION: In a component mounting method for mounting components on a substrate by holding components in a component holding part attached to a lower end of a shaft that is raised and lowered by a Z-axis motor, a thrust limit value of the Z-axis motor is set to a first limit value (ST32), the Z-axis motor is operated to lower the shaft (ST35), and if a rate of change of thrust of the Z-axis motor (ST36) measured by the thrust measurement unit (ST39) exceeds a predetermined threshold value (Yes in ST40), the thrust limit value of the Z-axis motor is changed to a second limit value, which is smaller than a first limit value (ST41).SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a component mounting apparatus and a component mounting method for mounting components on a board. [Background technology]

[0002] Known component mounting devices for mounting components on a board are those that absorb variations in mounting height position due to warpage or deformation of the board and mount the component while pressing it onto the mounting position on the board with a constant mounting load (for example, Patent Document 1). The component mounting device described in Patent Document 1 uses a servo motor to lower a nozzle that holds the component, and applies a constant mounting load to the component that has landed on the board by controlling the thrust of the servo motor so that it does not exceed a predetermined thrust limit value from the timing when the component reaches a predetermined height above the board. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-061991 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional technologies including Patent Document 1, the thrust force is controlled so as not to exceed a predetermined limit value from the time when the component reaches a predetermined height above the board, which causes the following problem: If the sliding resistance of the servo motor or shaft increases due to deterioration over time, the thrust required to lower the nozzle before the component lands on the board exceeds the thrust limit value, causing the nozzle to stop moving downward. Furthermore, if the placement load is reduced, the thrust limit value must be set small, which causes the nozzle to stop moving downward even with a slight increase in sliding resistance.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a component mounting apparatus and a component mounting method that can reliably mount components on a board while applying a constant mounting load to the components. [Means for solving the problem]

[0006] The component mounting device of the present invention is a component mounting device that holds a component with a component holder and mounts it on a board, and includes: a shaft having the component holder attached to its lower end; a motor that raises and lowers the shaft; a thrust measuring unit that measures the thrust of the motor; and a control unit that controls the motor to raise and lower the shaft. a threshold setting unit that sets a predetermined threshold; The control unit operates the motor to lower the shaft holding the component in the component holder, and determines whether the rate of change in the thrust of the motor measured by the thrust measuring unit is The aforementioned The thrust limit value of the motor is set to a first limit value before exceeding a predetermined threshold, and the thrust limit value of the motor is changed to a second limit value smaller than the first limit value after exceeding the predetermined threshold. The threshold setting unit sets the predetermined threshold between a pre-contact change rate, which is the maximum value of the change rate of the thrust of the motor before the component held by the component holder comes into contact with the board, and a post-contact change rate, which is the minimum value of the change rate of the thrust of the motor after the component held by the component holder comes into contact with the board. .

[0007] The component mounting method of the present invention is a component mounting method in which a component is held by a component holder attached to the lower end of a shaft that is raised and lowered by a motor and mounted on a board, the component mounting method comprising: setting a thrust limit value of the motor to a first limit value; operating the motor to lower the shaft; and, when a rate of change in the thrust of the motor measured by a thrust measuring unit exceeds a predetermined threshold, changing the thrust limit value of the motor to a second limit value that is smaller than the first limit value. The predetermined threshold is set between a pre-contact rate of change, which is the maximum value of the rate of change of the thrust of the motor before the component held by the component holder comes into contact with the board, and a post-contact rate of change, which is the minimum value of the rate of change of the thrust of the motor after the component held by the component holder comes into contact with the board. . [Effects of the Invention]

[0008] According to the present invention, components can be reliably mounted on a board while applying a constant mounting load to the components. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view showing a configuration of a main part of a component mounting apparatus according to an embodiment of the present invention; [Figure 2]FIG. 1 is a cross-sectional view showing the configuration of a main part of a mounting head provided in a component mounting apparatus according to an embodiment of the present invention. [Figure 3] FIG. 10 is an explanatory diagram showing the relationship of forces acting on a mounting unit of a mounting head provided in a component mounting apparatus according to an embodiment of the present invention. [Figure 4] FIG. 1 is a block diagram showing the configuration of a control system of a component mounting apparatus according to an embodiment of the present invention. [Figure 5] FIG. 1 is a block diagram showing the configuration of a control system for a mounting head attached to a component mounting apparatus according to an embodiment of the present invention. [Figure 6] FIG. 1A is an explanatory diagram showing the transition of the nozzle height position during component mounting by a component mounting device according to an embodiment of the present invention; FIG. 1B is an explanatory diagram showing the transition of the thrust force of a Z-axis motor; and FIG. 1C is an explanatory diagram showing the transition of the rate of change of the thrust force of a Z-axis motor. [Figure 7] FIG. 1A is an explanatory diagram showing the transition of the nozzle height position before and after a component comes into contact with a board during component mounting by a component mounting device according to an embodiment of the present invention; FIG. 1B is an explanatory diagram showing the transition of the thrust force of a Z-axis motor; and FIG. 1C is an explanatory diagram showing the transition of the rate of change of the thrust force of a Z-axis motor. [Figure 8] FIG. 10 is an explanatory diagram illustrating the setting of a contact determination value used in component mounting by a component mounting device according to an embodiment of the present invention. [Figure 9] 1 is a flow diagram of a method for manufacturing a mounting substrate according to an embodiment of the present invention; [Figure 10] 1 is a flow diagram of a method for determining a contact determination value according to an embodiment of the present invention; [Figure 11] 1 is a flow diagram of a component mounting method according to an embodiment of the present invention; [Figure 12] 1 is a flow diagram of a component mounting method according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described in detail below with reference to the drawings. The configurations, shapes, etc. described below are examples for the purpose of explanation and can be modified as appropriate depending on the specifications of the component mounting device and mounting head. In the following, corresponding elements in all drawings will be given the same reference numerals, and duplicated explanations will be omitted. In FIG. 1 and in some parts described below, two axes that are orthogonal to each other in a horizontal plane are shown: the X-axis in the substrate transport direction (the left-right direction in FIG. 1) and the Y-axis that is orthogonal to the substrate transport direction (the up-down direction in FIG. 1). In FIG. 2 and in some parts described below, the Z-axis (the up-down direction in FIG. 2) is shown as the height direction that is orthogonal to the horizontal plane.

[0011] First, the configuration of component mounting apparatus 1 will be described with reference to Figure 1. Component mounting apparatus 1 has the function of performing a component mounting operation in which components supplied from a component supply unit are mounted on a board to manufacture a mounted board. A board transport mechanism 3 is arranged along the X-axis in the center of base 2. Board transport mechanism 3 transports board P transported from upstream to the mounting operation position, positions it, and holds it. In addition, board transport mechanism 3 transports board P downstream after the component mounting operation has been completed.

[0012] Component supply units 4 are arranged on both sides (front and back along the Y axis) of the board transport mechanism 3. Each component supply unit 4 has multiple tape feeders 5 arranged along the X axis. Each tape feeder 5 of the component supply unit 4 pitch-feeds a component tape, on which pockets for storing components are formed, in a direction (tape feed direction) from the outside of the component supply unit 4 toward the board transport mechanism 3, thereby supplying components to a component supply position from which the components are picked up by a mounting head, which will be described below.

[0013] In FIG. 1, a Y-axis table 6 equipped with a linear drive mechanism is arranged along the Y-axis at both ends of the X-axis on the upper surface of base 2. A beam 7 similarly equipped with a linear drive mechanism is connected to Y-axis table 6 so as to be movable along the Y-axis. Beam 7 is arranged along the X-axis. A mounting head 8 is attached to beam 7 via plate 7a so as to be movable along the X-axis. Mounting head 8 is detachable from plate 7a. Mounting head 8 is equipped with a plurality of mounting units 20 (see FIG. 2). Component holders 29 (see FIG. 2) that suck and hold components are attached to the lower ends of mounting units 20, respectively.

[0014] The Y-axis table 6 and beam 7 constitute a head movement mechanism 9 that moves the mounting head 8 along the X-axis and Y-axis. The head movement mechanism 9 and mounting head 8 perform a mounting turn in which a component holder 29 attached to the mounting unit 20 sucks and removes a component from the tape feeder 5 arranged in the component supply unit 4, and mounts the component at a mounting position on the board P positioned by the board transport mechanism 3. In this way, multiple component holders 29 are attached to the mounting head 8, and each component holder 29 picks up a component supplied from the component supply unit 4 and mounts it on the board P.

[0015] In Fig. 1, a component recognition camera 10 is disposed between the component supply unit 4 and the board transport mechanism 3. When the mounting head 8 that has taken out a component from the component supply unit 4 moves above the component recognition camera 10, the component recognition camera 10 captures an image of the component held by the mounting head 8 and recognizes the holding posture of the component. A head camera 11 is attached to the plate 7a to which the mounting head 8 is attached. The head camera 11 moves integrally with the mounting head 8.

[0016] As the mounting head 8 moves, the head camera 11 moves above the board P positioned by the board transport mechanism 3, and captures an image of a board mark (not shown) provided on the board P to recognize the position of the board P. When the mounting head 8 mounts components on the board P, the mounting position is corrected taking into account the component recognition results by the component recognition camera 10 and the board position recognition results by the head camera 11.

[0017] 1, a touch panel 12 operated by the worker is installed at the position where the worker works in front of the component mounting device 1. The touch panel 12 displays various information on its display unit, and the worker inputs data and operates the component mounting device 1 using operation buttons and the like displayed on the display unit.

[0018] Next, the configuration of the mounting head 8 will be described with reference to Figure 2. The mounting head 8 has multiple mounting units 20 (four in the X direction in this case) arranged inside a mounting head base 8a. The mounting unit 20 is configured so that a shaft 21 extending in the vertical direction (Z-axis direction) is raised and lowered by a servo-controlled Z-axis motor 22, thereby raising and lowering a component holder 29.

[0019] Shaft 21 is connected to the lower side of Z-axis motor 22 via output unit 23. The lower end of shaft 21 is inserted into spline guide unit 24, which is rotatable in the θ direction by bearings 24a arranged above and below, and protrudes outward from the lower surface of mounting head base 8a. A component holder 29 is attached to the lower end of shaft 21 that protrudes from the lower surface of mounting head base 8a. In other words, component holder 29 is attached to the lower end of shaft 21, which is raised and lowered by Z-axis motor 22 (motor).

[0020] 2, return spring 25, which is a compression spring, is attached to shaft 21 between output portion 23 and spline guide portion 24. Return spring 25 exerts an upward repulsive force on output portion 23. That is, when component holder 29 is to be lowered, Z-axis motor 22 generates a downward thrust, which lowers shaft 21 against the repulsive force of return spring 25. When component holder 29 is to be raised, Z-axis motor 22 reduces the thrust it generates, and the return spring 25 raises output portion 23 with an upward repulsive force, which raises shaft 21.

[0021] A scale 26 protrudes upward from the top of Z-axis motor 22. The scale 26 moves up and down in accordance with the vertical movement of output unit 23, i.e., the vertical movement of shaft 21. A position detection sensor 27 that detects the movement of scale 26 is also disposed above Z-axis motor 22. Position detection sensor 27 outputs encoder pulses indicating the distance and direction of movement of scale 26 as position signals to servo control unit 40 (see FIG. 4). The vertical position (height position) of shaft 21 is detected from the position signal. In other words, scale 26 and position detection sensor 27 form encoder 28 that detects the height position of shaft 21 (or component holder 29).

[0022] Next, the relationship between the forces acting on mounting unit 20 will be described with reference to Fig. 3. Thrust Ft is generated by Z-axis motor 22, and acts in a direction that presses down shaft 21, which is connected via output unit 23. Weight W is the sum of the weights of the hatched parts that indicate the moving parts in the figure, that is, scale 26, output unit 23, shaft 21, component holder 29, etc., and acts in a direction that presses down shaft 21, just like thrust Ft.

[0023] Reaction force Fr is the reaction force of return spring 25, and acts in a direction pushing shaft 21 upward via output portion 23. Resistance Ff is an external resistive force from spline guide portion 24 and the like that slidably holds the above-mentioned movable portion, and acts upward on shaft 21 that is driven in the downward direction. Load Fa represents the load when component D held by component holder 29 is pressed against board P.

[0024] 3 shows a state in which component holder 29 is pressing component D held by it against board P during component mounting work. In this state, load Fa is expressed as Fa = Ft + W - Fr - Ff. When thrust Ft of Z-axis motor 22 is increased while component D is in contact with board P, load Fa increases in proportion to thrust Ft while reaction force Fr of return spring 25 remains constant. Furthermore, load Fa is zero before component D held by component holder 29 comes into contact with board P, and output unit 23 (shaft 21, component holder 29) descends in proportion to thrust Ft of Z-axis motor 22, increasing reaction force Fr of return spring 25 (Fr = Ft + W - Ff).

[0025] Next, the configuration of the control system of the component mounting apparatus 1 will be described with reference to Fig. 4. The main body control unit 30 provided in the component mounting apparatus 1 is connected to the board transport mechanism 3, tape feeder 5, mounting head 8, head moving mechanism 9, component recognition camera 10, head camera 11, and touch panel 12. The four mounting units 20 provided in the mounting head 8 each include a servo control unit 40. The servo control unit 40 is connected to a Z-axis motor 22 and an encoder 28.

[0026] Servo control unit 40 drives Z-axis motor 22 based on the vertical position of shaft 21 (component holder 29) detected by encoder 28, in accordance with a command from main body control unit 30. Methods for controlling Z-axis motor 22 by servo control unit 40 include position control and torque control. In the case of position control, servo control unit 40 controls Z-axis motor 22 so that the height of lift unit 37 matches the height commanded by main body control unit 30. In the case of torque control, servo control unit 40 controls thrust Ft of Z-axis motor 22 based on a command from main body control unit 30.

[0027] 4, the main body control unit 30 includes a main body storage unit 31, a threshold setting unit 32, and a mounting processing unit 33. The main body storage unit 31 is a storage device that stores mounting data 31a, thrust measurement results 31b, threshold information 31c, and the like. The mounting data 31a stores various information for each type of mounting board, such as information identifying the board P (board type number, size, material, thickness, etc.), the type of component D to be mounted on the board P, and the coordinates of the mounting position on the board P. The mounting data 31a also stores, for each mounting unit 20 (component holder 29), thrust limit values ​​(first limit value, second limit value) of the Z-axis motor 22 during component mounting.

[0028] Thrust force measurement result 31b stores the measurement result of thrust Ft of Z-axis motor 22 measured by thrust force measurement unit 42, which will be described later, or the rate of change ΔFt of thrust calculated from the measurement result of thrust Ft of Z-axis motor 22. Threshold value information 31c stores, for each type of mounting board, a contact determination value that is a threshold value for determining whether component D held by component holding unit 29 has come into contact with board P during component mounting.

[0029] 4, threshold setting unit 32 executes threshold setting processing to determine a contact determination value based on thrust force measurement result 31b and store the determined value as threshold information 31c. Mounting processing unit 33 controls each unit of component mounting apparatus 1 to perform component mounting work based on the component name, mounting position, etc. of component D to be mounted on board P included in mounting data 31a.

[0030] Next, the control system of the mounting head 8 will be described in detail with reference to Fig. 5. The mounting head 8 is equipped with four mounting units 20(#1) to (#4). Each mounting unit 20(#1) to (#4) is equipped with a Z-axis motor 22(#1) to (#4), an encoder 28(#1) to (#4), and a servo control unit 40(#1) to (#4). The four mounting units 20(#1) to (#4) have the same configuration, and the following description will be given using mounting unit 20(#1) as an example. Furthermore, the symbols (#1) to (#4) that identify the mounting units 20, etc. will be omitted where appropriate.

[0031] 5, servo control unit 40 includes motor driver 41, thrust measurement unit 42, thrust limiting unit 43, position detection unit 44, contact detection unit 45, and head storage unit 46. Head storage unit 46 is a storage device that stores a contact determination value 46a, a first limiting value 46b, a second limiting value 46c, and the like. Of the contact determination values ​​included in threshold information 31c, the contact determination value corresponding to the mounting board manufactured by component mounting apparatus 1 is stored as contact determination value 46a. Of the thrust limiting values ​​of Z-axis motor 22 included in mounting data 31a, the first limiting value 46b and the second limiting value 46c store the first limiting value and the second limiting value corresponding to mounting unit 20 (component holder 29), respectively.

[0032] Motor driver 41 is a drive control device for Z-axis motor 22, which is a servo motor, and supplies current (arrow a) to Z-axis motor 22 based on a preset operation pattern to drive Z-axis motor 22. Motor driver 41 then detects deviations from the target height position and target elevation speed determined by the operation pattern using pulse signals sent from encoder 28 (arrow b), and drives Z-axis motor 22 using servo control that feeds back the detected deviations.

[0033] 5, thrust measurement unit 42 has a function of measuring thrust Ft of Z-axis motor 22. That is, thrust Ft generated by Z-axis motor 22 is measured based on the current (arrow a) supplied to Z-axis motor 22 from motor driver 41 or the current value (arrow c) notified from motor driver 41. In this embodiment, thrust Ft of Z-axis motor 22 is limited by the function of thrust limiting unit 43 based on first limiting value 46b or second limiting value 46c stored in head memory unit 46.

[0034] The contact detection unit 45 calculates the rate of change ΔFt of thrust from the thrust Ft measured by the thrust measurement unit 42. Furthermore, when the calculated rate of change ΔFt of thrust exceeds a contact determination value 46a, the contact detection unit 45 determines that the component D has come into contact with the board P. That is, based on the contact determination value 46a and the thrust Ft of the Z-axis motor 22 (motor) measured by the thrust measurement unit 42, when the rate of change ΔFt of thrust of the Z-axis motor 22 exceeds the contact determination value 46a (predetermined value), the contact detection unit 45 determines (detects) that the component D held by the component holding unit 29 has come into contact with the board P.

[0035] 5, the thrust limiting unit 43 sets the first limiting value 46b in the motor driver 41 (arrow d) before the contact detecting unit 45 detects that the component D has come into contact with the board P. Furthermore, when the contact detecting unit 45 detects that the component D has come into contact with the board P, the thrust limiting unit 43 sets the second limiting value 46c in the motor driver 41 (arrow d).

[0036] That is, the thrust limiting unit 43 provided in the servo control unit 40 (control unit) operates the Z-axis motor 22 (motor) to lower the shaft 21, and sets the thrust limiting value of the Z-axis motor 22 to a first limiting value 46b before the contact detection unit 45 detects that the component D held by the component holding unit 29 has come into contact with the substrate P, and changes the thrust limiting value of the Z-axis motor 22 to a second limiting value 46c that is smaller than the first limiting value 46b after the contact detection unit 45 detects that the component D held by the component holding unit 29 has come into contact with the substrate P.

[0037] 5, position detector 44 counts encoder pulses (arrow e) from encoder 28 of Z-axis motor 22. This count value serves as position information indicating the height position (height position) of component holder 29. In other words, position detector 44 has a height position measurement function that detects the height position of component holder 29 based on the position signal from Z-axis motor 22.

[0038] 6 and 7, details of the component mounting operation will be described in which servo control unit 40 (control unit) controls Z-axis motor 22 to mount components D held by component holder 29 onto substrate P. For simplicity, the following description will be given taking as an example a case in which substrate P does not deform (bend) due to load Fa applied from above.

[0039] In the component mounting operation, servo control unit 40 lowers component D held by component holder 29 toward board P at a predetermined descending speed, and when the underside of component D contacts (lands on) board P, servo control unit 40 presses component D against board P with a predetermined load Fa for a predetermined pressing time Tc. Furthermore, servo control unit 40 releases component holder 29 from the suction state during pressing time Tc, releasing component D, and then raises component holder 29 to a predetermined standby position at a predetermined ascending speed after pressing time Tc has elapsed.

[0040] 6(a) and 7(a) show the time progression of the height position of the bottom surface of component D held by component holder 29. FIGS. 6(b) and 7(b) show the time progression of thrust Ft of Z-axis motor 22 measured by thrust measurement unit 42. FIGS. 6(c) and 7(c) show the time progression of rate of change ΔFt of thrust of Z-axis motor 22 calculated by contact detection unit 45. In FIGS. 6(a) to 6(c), a solid line indicates a good sliding state where resistance Ff of the moving part of mounting unit 20 is below a predetermined value, a dotted line indicates a good sliding state where resistance Ff is not poor but is somewhat large, and a dashed-dotted line indicates a poor sliding state where resistance Ff is large.

[0041] 6(a) to 6(c) show the time progression during the component mounting operation by mounting unit 20, in which component holding unit 29 descends (the time period indicated by ellipse f1 in FIG. 6(a)), brings held component D into contact with board P (time T2 indicated by circle f2 in FIG. 6(a)), mounts component D on board P (time T6 indicated by circle f3 in FIG. 6(a)), and then ascends. FIGS. 7(a) to 7(c) show an enlarged view of the time progression shown in FIGS. 6(a) to 6(c), around time T4 when contact detection unit 45 determines that component D has come into contact with board P (contact of component D is detected).

[0042] As shown in Figures 7(a) to 7(c), the thrust measurement unit 42 and the position detection unit 44 measure the height position and the thrust Ft of the Z-axis motor 22 at predetermined measurement intervals ΔT, respectively. For convenience, the measured values ​​and calculated values ​​are displayed as continuous lines in Figures 6(a) to 6(c). Note that Figure 8, which will be described later, also displays the rate of change ΔFt of the thrust of the Z-axis motor 22 as a continuous line.

[0043] First, the good sliding state shown by the solid lines in Figures 6(a) to 6(c) will be described. In Figure 6(a), servo control unit 40 controls position control to cause Z-axis motor 22 to lower component holder 29 (shaft 21) at a predetermined lowering speed until time T4 when contact detection unit 45 determines that component D held by component holder 29 has come into contact with board P. In this state, motor driver 41 controls thrust limiting unit 43 to set the thrust limit value of Z-axis motor 22 to first limiting value 46b.

[0044] As a result, until time T2 when component D comes into contact with board P, as shown in Fig. 6(b), thrust Ft of Z-axis motor 22 increases at a constant rate (ellipse g1) so as to cancel out reaction force Fr of return spring 25, which increases due to compression as component D descends. Then, as shown in Fig. 6(c), the rate of change ΔFt of thrust of Z-axis motor 22 until time T2 is constant and smaller than contact determination value 46a.

[0045] After time T2 when component D comes into contact with board P, the height position of the bottom surface of component D remains unchanged, as shown in FIG. 6(a). In the case of flexible board P, the height position of component D also drops by the amount of bending due to the bending of board P caused by an increase in the load Fa applied to board P from component D. On the other hand, as shown in FIG. 6(b), when component D comes into contact with board P, the board P prevents the shaft 21 from descending, but motor driver 41 increases the current supplied to Z-axis motor 22 to lower component D at the set lowering speed. As a result, thrust Ft of Z-axis motor 22 increases sharply (ellipse g2) from before component D comes into contact with board P (ellipse g1).

[0046] 7(c), as a result of the sudden increase in thrust Ft, the rate of change ΔFt of the thrust of Z-axis motor 22 increases and exceeds contact determination value 46a from time T3, which is a measurement interval time ΔT after time T2. When the state in which the rate of change ΔFt of the thrust of Z-axis motor 22 exceeds contact determination value 46a continues beyond determination time Tj, contact detection unit 45 determines that component D has come into contact with board P. In this example, measurement interval time ΔT is three times the measurement interval time ΔT, and contact detection unit 45 determines that component D has come into contact with board P when the rate of change ΔFt of the thrust of Z-axis motor 22, calculated every measurement interval time ΔT, exceeds contact determination value 46a four times in a row (time T4 indicated by circle h).

[0047] The determination by the contact detection unit 45 that the component D has come into contact with the board P is not limited to the case where the rate of change ΔFt of thrust force is equal to or greater than the contact determination value 46a four consecutive times. For example, the contact detection unit 45 may determine that the component D has come into contact with the board P when the average value of the rate of change ΔFt of thrust force calculated every measurement interval time ΔT for four consecutive times is equal to or greater than the contact determination value 46a.

[0048] Furthermore, the contact detection unit 45 may calculate a rate of change ΔFt of thrust relative to the thrust Ft of the Z-axis motor 22 measured before the judgment time Tj, and determine that the component D has come into contact with the board P if the rate of change ΔFt of thrust is equal to or greater than the contact judgment value 46a. In the example of FIG. 7(c), the rate of change ΔFt of thrust may be calculated from the thrust Ft of the Z-axis motor 22 measured at a time before the judgment time Tj from time T3 and the thrust Ft of the Z-axis motor 22 measured at time T3, and determine that the component D has come into contact with the board P if the rate of change ΔFt of thrust is equal to or greater than the contact judgment value 46a. In this case, it is determined that the component D has come into contact with the board P at time T3.

[0049] 7(b), when contact detection unit 45 determines that component D has come into contact with substrate P (time T4), thrust limiter 43 changes the thrust limit value of Z-axis motor 22 to second limit value 46c. In this manner, servo control unit 40 (controller) operates Z-axis motor 22 (motor) to lower shaft 21 on which component holder 29 holds component D, and sets the thrust limit value of Z-axis motor 22 to first limit value 46b before the rate of change ΔFt of thrust of Z-axis motor 22 measured by thrust measurement unit 42 exceeds contact determination value 46a (predetermined threshold value), and changes the thrust limit value of Z-axis motor 22 to second limit value 46c, which is smaller than first limit value 46b, after contact determination value 46a is exceeded.

[0050] Even after the thrust limit value of the Z-axis motor 22 is changed to the second limit value 46c, as shown in FIG. 7(b), the thrust Ft of the Z-axis motor 22 continues to increase and reaches the second limit value 46c at time T5 indicated by the circle i. When the thrust measurement unit 42 detects that the thrust Ft of the Z-axis motor 22 has reached the second limit value 46c, the servo control unit 40 controls the thrust Ft of the Z-axis motor 22 so that it remains constant at the second limit value 46c. As a result, the component D is pressed against the board P with a constant load Fa (Fa = Ft + W - Fr - Ff) corresponding to the thrust Ft of the Z-axis motor 22 (during the time period indicated by the ellipse g3 in FIG. 6(b)). In other words, the second limit value 46c is preset so that the load Fa applied to the component D during the component mounting operation is an appropriate value for mounting the component D on the board P.

[0051] In Figure 6(b), servo control unit 40 raises component holder 29 at a predetermined raising speed (ellipse g4) from time T6, when a preset pressing time Tc has elapsed after time T5, when thrust Ft of Z-axis motor 22 reaches second limit value 46c. That is, Z-axis motor 22 is controlled to decrease thrust Ft, and as shown in Figure 6(c), the rate of change ΔFt of thrust of Z-axis motor 22 becomes negative. In this manner, component D is mounted on board P.

[0052] Next, we will explain the poor sliding state shown by the dashed-dotted lines in Figures 6(a) to 6(c). In the case of poor sliding, during the time period when component holder 29 is lowered by position control (ellipse f1 shown in Figure 6(a)), thrust Ft of Z-axis motor 22 becomes larger than in the good sliding state so as to counteract the large resistance Ff added to reaction force Fr of return spring 25. Then, as shown in Figure 6(b), thrust Ft of Z-axis motor 22 reaches first limit value 46b at time T1 before component D comes into contact with board P.

[0053] If the thrust Ft of the Z-axis motor 22 (motor) reaches the first limit value 46b before the rate of change ΔFt of the thrust exceeds the contact determination value 46a, the contact detection unit 45 determines that the lowering state (sliding state) of the shaft 21 is poor. If the sliding state is determined to be poor, the servo control unit 40 stops the component mounting operation and raises the component holder 29 to the standby position. Then, the servo control unit 40 displays an error on the touch panel 12 indicating that the mounting unit 20 is experiencing a sliding problem.

[0054] Next, we will explain the large sliding state shown by the dotted lines in Figures 6(a) to 6(c). In the case of large sliding, the thrust Ft of Z-axis motor 22 during the time period when component holder 29 is lowered by position control is also larger than in the case of good sliding. Then, as shown in Figure 6(b), before component D comes into contact with board P, thrust Ft of Z-axis motor 22 exceeds second limit value 46c, but does not reach first limit value 46b, which is set as the thrust force limit value at that time.

[0055] When component D comes into contact with substrate P at time T2, similar to the good sliding state, thrust Ft of Z-axis motor 22 increases rapidly (ellipse g5). Thereafter, similar to the good sliding state, contact detection unit 45 determines that component D has come into contact with substrate P. Thereafter, control by servo control unit 40 is similar to that in the good sliding state, and detailed description thereof will be omitted.

[0056] In this way, when the servo control unit 40 detects that the component D has come into contact with the board P, it changes the thrust limit value of the Z-axis motor 22 from the first limit value 46b to the second limit value 46c, which is smaller than the first limit value 46b. The first limit value 46b is set in advance so that the thrust Ft of the Z-axis motor 22 does not exceed the thrust limit value before the component D comes into contact with the board P in a state where the resistance Ff of the movable part of the mounting unit 20 is large enough to cause a sliding failure.

[0057] As a result, even in a state where the resistance Ff of the movable part of the mounting unit 20 is on the rise and sliding is large, the component D can be reliably mounted on the board P while applying a constant mounting load (load Fa corresponding to the second limit value 46c) to the component D. In other words, even a low-load component with a mounting load smaller than the resistance Ff of the movable part can be reliably mounted on the board P.

[0058] In the above configuration, contact detection unit 45 detects that component D held by component holder 29 has come into contact with board P based on thrust Ft of Z-axis motor 22, but the present invention is not limited to this configuration. For example, contact detection unit 45 may be configured to detect that component D has come into contact with board P using a camera that captures an image of the vicinity of the lower end of component holder 29. Alternatively, contact detection unit 45 may be configured to detect that component D has come into contact with board P using a three-dimensional sensor that measures the distance from component holder 29 to board P.

[0059] Next, a method for setting contact determination value 46a (predetermined threshold value) by threshold setting unit 32 of main body control unit 30 will be described with reference to Fig. 8. First, with no board P held by board transport mechanism 3, threshold setting unit 32 causes mounting unit 20 to lower component holder 29 using position control, and measures the rate of change ΔFt in thrust of Z-axis motor 22. Hereinafter, the rate of change ΔFt in thrust of Z-axis motor 22 measured with no board P present will be referred to as the "pre-contact rate of change." The measurement result is stored in main body storage unit 31 as thrust measurement result 31b.

[0060] Next, with the board P held by the board transport mechanism 3, the threshold setting unit 32 causes the mounting unit 20 to lower the component holder 29 using position control and measure the rate of change ΔFt of the thrust of the Z-axis motor 22. After the component holder 29 comes into contact with the board P, the rate of change ΔFt of the thrust of the Z-axis motor 22 increases rapidly, similar to the period from time T3 to time T5 indicated by the ellipse g2 in FIG. 6(c). Hereinafter, the rate of change ΔFt of the thrust of the Z-axis motor 22 measured after the component holder 29 comes into contact with the board P will be referred to as the "post-contact rate of change." The measurement result is stored in the main body storage unit 31 as the thrust measurement result 31b.

[0061] 8 shows an example of the time transition of the pre-contact change rate and post-contact change rate measured by the mounting units 20(#1) to (#4). The threshold setting unit 32 sets the contact determination value 46a to a value between the maximum pre-contact change rate and the minimum post-contact change rate of the mounting units 20(#1) to (#4) and greater than the rate of change ΔFt of the thrust of the Z-axis motor 22 in the case of a sliding failure.

[0062] This makes it possible to properly detect that the component D has come into contact with the substrate P in the cases of good sliding and large sliding, and to properly detect that the component D is defective before it comes into contact with the substrate P in the case of poor sliding. Furthermore, by measuring the rate of change after contact on the actual substrate P, it is possible to set an appropriate contact determination value 46a even for a substrate P that has low hardness and is prone to bending.

[0063] The threshold setting unit 32 associates the set contact determination value 46a with information identifying the measured substrate P and stores it as threshold information 31c in the main body storage unit 31. The information identifying the substrate P includes the substrate type number, the size, material, thickness, and hardness of the substrate. That is, the threshold setting unit 32 sets the contact determination value 46a (predetermined threshold) based on information related to the hardness of the substrate. The threshold setting unit 32 also calculates the difference in the thrust Ft of the Z-axis motor 22 (motor) measured by the thrust measurement unit 42 at a predetermined time interval (measurement interval time ΔT) as the thrust change rate ΔFt.

[0064] In this way, the threshold setting unit 32 sets the contact judgment value 46a (predetermined threshold) between the maximum value of the pre-contact change rate, which is the change rate ΔFt of the thrust of the Z-axis motor 22 before the component D held by the component holding unit 29 comes into contact with the board P, and the minimum value of the post-contact change rate, which is the change rate ΔFt of the thrust of the Z-axis motor 22 after the component D held by the component holding unit 29 comes into contact with the board P.

[0065] Next, a description will be given of a method for manufacturing a mounted board in which components D are held by component holders 29 attached to the lower end of shaft 21 that moves up and down by Z-axis motor 22 (motor) and mounted on board P, with reference to the flow in Fig. 9. In Fig. 9, first, mounting processing unit 33 determines whether the mounted board to be manufactured has been manufactured in the past (ST1). If it has not been manufactured before (No in ST1), threshold setting unit 32 executes threshold setting steps (ST2 to ST5). Specifically, threshold setting unit 32 causes mounting units 20(1) to (4) to measure thrust Ft of Z-axis motor 22 when there is no board P on board transport mechanism 3 (ST2).

[0066] Next, with the board P held by the board transport mechanism 3, the threshold setting unit 32 causes the mounting units 20(1)-(4) to bring the component holders 29 into contact with the board P and measure the thrust Ft of the Z-axis motor 22 (ST3). The threshold setting unit 32 brings the component holders 29 into contact with the board P at multiple positions on the board P and measures the thrust Ft of the Z-axis motor 22. This makes it possible to determine an appropriate contact determination value 46a, taking into account the influence of the board hardness due to the mounting position, etc.

[0067] 9, threshold setting unit 32 then calculates a pre-contact change rate from thrust Ft of Z-axis motor 22 measured without substrate P, and calculates a post-contact change rate from thrust Ft of Z-axis motor 22 measured by bringing component holder 29 into contact with substrate P (ST4). Next, threshold setting unit 32 determines contact determination value 46a (predetermined threshold) based on the calculated pre-contact change rate and post-contact change rate (ST5: contact determination value determination step).

[0068] When the contact determination value 46a is set in the threshold setting steps (ST2 to ST5), the mounting processing unit 33 stores the contact determination value 46a in the head storage unit 46 of the servo control unit 40(1) to (4) of the mounting unit 20(1) to (4) (ST6: contact determination value acquisition step). That is, in the contact determination value acquisition step (ST6), the servo control unit 40(1) to (4) acquires the contact determination value 46a from the main body control unit 30.

[0069] In the case of a mounting board that has been manufactured beforehand (Yes in ST1), the threshold setting steps (ST2 to ST5) are skipped, and the contact determination value 46a that has been stored in advance in the threshold information 31c is stored in the head storage unit 46. Furthermore, even if the mounting board has not been manufactured beforehand, if there is a history of another mounting board having similar material, thickness, size, etc. to the substrate P and equivalent hardness, the threshold setting steps (ST2 to ST5) may be skipped, and the contact determination value 46a of the other mounting board included in the threshold information 31c may be used instead.

[0070] 9, the mounting processing unit 33 then controls the board transport mechanism 3 to load the board P that is the target of the component mounting operation and hold it at the mounting operation position (ST7: board load step). Next, the mounting processing unit 33 repeats the mounting turn to load the components D at the mounting position on the board P based on the mounting data 31a until all components D are mounted on the board (No in ST9) (ST8: component mounting step). Once all components D have been mounted (Yes in ST9), the mounting processing unit 33 controls the board transport mechanism 3 to load the board P for which the component mounting operation has been completed (ST10: board unload step). Next, if there is a board P that is the target of the component mounting operation (No in ST11), the process returns to the board load step (ST7), and the next board P is loaded at the mounting operation position.

[0071] Next, the contact determination value determination step (ST5) (contact determination value determination method) will be described in detail with reference to FIG. 8 along the flow of FIG. 10. First, the threshold setting unit 32 determines whether the maximum value of the calculated multiple pre-contact change rates is smaller than the minimum value of the calculated multiple post-contact change rates (ST21). If the maximum value of the pre-contact change rate is equal to or greater than the minimum value of the post-contact change rate (No in ST21), the threshold setting unit 32 determines whether there is a mounting unit 20 among the mounting units 20(1) to (4) whose maximum pre-contact change rate becomes smaller than the minimum value of the post-contact change rate when the mounting unit 20 is excluded (ST22). In other words, it determines whether the maximum pre-contact change rate becomes smaller than the minimum value of the post-contact change rate when the mounting unit 20 whose pre-contact change rate is equal to or greater than the minimum value of the post-contact change rate when the mounting unit 20 (hereinafter referred to as a "faulty mounting unit") is excluded.

[0072] If, after excluding the defective mounting unit, the maximum pre-contact change rate becomes smaller than the minimum post-contact change rate (Yes in ST22), the threshold setting unit 32 sets the defective mounting unit so that it cannot be used in component mounting work (ST23). Next, the threshold setting unit 32 causes the touch panel 12 to display information about the defective mounting unit that has been set as unusable and a message that the defective mounting unit should be maintained (ST24: defective unit display step). After the defective unit display step (ST24), or if the maximum pre-contact change rate is smaller than the minimum post-contact change rate (Yes in ST21), the threshold setting unit 32 determines whether the thrust change rate ΔFt when the mounting unit 20 has a sliding defect is smaller than the minimum post-contact change rate (ST25).

[0073] 10, if the rate of change in thrust force ΔFt in the case of poor sliding is smaller than the minimum value of the rate of change after contact (Yes in ST25), the threshold setting unit 32 sets the contact determination value 46a between the minimum value of the rate of change after contact and the rate of change in thrust force ΔFt in the case of poor sliding (ST26: contact determination value setting step) (see FIG. 8). Next, the threshold setting unit 32 associates the set contact determination value 46a with information identifying the substrate P of the mounting substrate (substrate type number, size, material, thickness, etc.), and stores the result as threshold information 31c in the main body storage unit 31 (ST27).

[0074] If the maximum pre-contact change rate does not become smaller than the minimum post-contact change rate even after excluding the defective mounted units (No in ST22), or if the rate of change in thrust ΔFt in the case of a sliding defect is equal to or greater than the minimum post-contact change rate (No in ST25), threshold setting unit 32 notifies touch panel 12 that an appropriate contact determination value 46a (predetermined threshold) cannot be set (ST28). At this time, threshold setting unit 32 may write a comment on touch panel 12 suggesting a measure to "use a carrier to place substrate P on, or use support pins to support substrate P from below after being transported to the mounting work position."

[0075] Next, the component mounting step (ST8) (component mounting method) will be described in detail with reference to the flow in Fig. 11 and Fig. 12. Here, one mounting turn in which the mounting unit 20 holds the component D and mounts it at the mounting position on the board P will be described. In Fig. 11, first, the mounting processing unit 33 stores the first limit value 46b and the second limit value 46c corresponding to the component D to be mounted by the mounting unit 20 in the head storage unit 46 of the servo control unit 40 based on the mounting data 31a (ST31: limit value acquisition step). That is, in the limit value acquisition step (ST31), the servo control unit 40 acquires the first limit value 46b and the second limit value 46c from the main body control unit 30.

[0076] Next, thrust limiting unit 43 sets the thrust limit value of Z-axis motor 22 to first limiting value 46b (ST32: first limiting value setting step). Next, mounting unit 20 picks up component D from tape feeder 5 (ST33) and moves to above the mounting position (ST34). Next, servo control unit 40 operates Z-axis motor 22 by position control to start descending shaft 21 (ST35: descent start step). As a result, component holder 29 holding component D starts descending toward the mounting position on board P. Note that the descent start step (ST35) may be executed before mounting unit 20 arrives above the mounting position (before ST34 is completed).

[0077] 11, next, thrust measurement unit 42 acquires thrust Ft of Z-axis motor 22 (ST36: first thrust acquisition step). Next, contact detection unit 45 determines whether the acquired thrust Ft of Z-axis motor 22 exceeds first limit value 46b (ST37: first limit value exceedance determination step). If it is determined that thrust Ft of Z-axis motor 22 exceeds first limit value 46b (Yes in ST37), servo control unit 40 stops the component mounting operation, raises component holder 29 to the standby position, and causes touch panel 12 to notify an error due to poor sliding (ST38: error notification step).

[0078] If it is determined that the thrust Ft of the Z-axis motor 22 does not exceed the first limit value 46b (No in ST37), the contact detection unit 45 calculates the thrust change rate ΔFt from the acquired thrust Ft of the Z-axis motor 22 (ST39: change rate calculation step).The contact detection unit 45 then determines whether the calculated thrust change rate ΔFt of the Z-axis motor 22 exceeds the contact determination value 46a (ST40: contact determination value excess determination step).

[0079] 11, if the rate of change ΔFt of the thrust of the Z-axis motor 22 does not exceed the contact determination value 46a (No in ST40), the process returns to the first thrust acquisition step (ST36), and the first limit value exceedance determination step (ST37), the rate of change calculation step (ST39), and the contact determination value exceedance determination step (ST40) are repeatedly executed. The first thrust acquisition step (ST36) is executed at every measurement interval time ΔT.

[0080] When the rate of change ΔFt of the thrust of the Z-axis motor 22 exceeds the contact determination value 46a (Yes in ST40), the contact detection unit 45 determines that the component D has come into contact with the board P. In this way, the first thrust acquisition process (ST36), the first limit value exceedance determination process (ST37), the rate of change calculation process (ST39), and the contact determination value exceedance determination process (ST40) are contact detection processes that detect that the component D has come into contact with the board P.

[0081] 11, in the contact detection process (ST36 to ST37, ST39 to ST40), when contact detection unit 45 detects that component D held by component holder 29 has come into contact with substrate P, thrust limiter 43 changes the thrust limit value of Z-axis motor 22 to second limit value 46c, which is smaller than first limit value 46b (ST41: second limit value setting process). That is, when the rate of change ΔFt of the thrust of Z-axis motor 22 measured by thrust measurement unit 42 exceeds a predetermined threshold value (contact determination value 46a), thrust limiter 43 changes the thrust limit value of Z-axis motor 22 to second limit value 46c, which is smaller than first limit value 46b.

[0082] 12, the thrust measurement unit 42 then acquires the thrust Ft of the Z-axis motor 22 (ST42: second thrust acquisition step). Next, the contact detection unit 45 determines whether the acquired thrust Ft of the Z-axis motor 22 exceeds the second limit value 46c (ST43: second limit value exceedance determination step). If it is determined that the thrust Ft of the Z-axis motor 22 does not exceed the second limit value 46c (No in ST43), the process returns to the second thrust acquisition step (ST42), and the thrust Ft of the Z-axis motor 22 is acquired after the measurement interval time ΔT.

[0083] 12, when it is determined that the thrust Ft of the Z-axis motor 22 exceeds the second limit value 46c (Yes in ST43), the servo control unit 40 stops the descent of the shaft 21 (ST44: descent stop step). Next, the servo control unit 40 maintains the thrust Ft of the Z-axis motor 22 at the second limit value 46c for a predetermined pressing time Tc (No in ST45) (see ellipse g3 in FIG. 6(b)). After the pressing time Tc has elapsed (Yes in ST45), the servo control unit 40 then raises the shaft 21 to the standby position (ST46: raising step). This allows the component D to be reliably mounted on the board P while applying a constant mounting load (load Fa determined by the second limit value 46c) to the component D for the pressing time Tc.

[0084] As described above, the component mounting device 1 of this embodiment includes a shaft 21 having a component holding portion 29 attached to its lower end, a Z-axis motor 22 (motor) that raises and lowers the shaft 21, a thrust measuring portion 42 that measures the thrust Ft of the Z-axis motor 22, and a servo control portion 40 (control portion) that controls the Z-axis motor 22 and raises and lowers the shaft 21.

[0085] Then, servo control unit 40 operates Z-axis motor 22 to lower shaft 21 on which component holder 29 holds component D, and sets the thrust limit value of Z-axis motor 22 to first limit value 46b before the rate of change ΔFt of the thrust of Z-axis motor 22 measured by thrust measurement unit 42 exceeds a predetermined threshold value (contact determination value 46a), and changes the thrust limit value of Z-axis motor 22 to second limit value 46c that is smaller than first limit value 46b after the predetermined threshold value is exceeded. This allows component D to be reliably mounted on board P while applying a constant mounting load (load Fa determined by second limit value 46c) to component D. [Industrial Applicability]

[0086] The component mounting apparatus and component mounting method of the present invention have the effect of being able to reliably mount components on a board while applying a constant mounting load to the components, and are useful in fields where components are mounted on boards. [Explanation of symbols]

[0087] 1. Component mounting equipment 21 Shaft 22 Z-axis motor (motor) 29 Parts holder D parts Ft Thrust P board ΔFt Thrust change rate

Claims

1. A component mounting device that holds components in a component holder and mounts them on a board, a shaft having the component holder attached to its lower end; a motor for raising and lowering the shaft; a thrust measuring unit that measures the thrust of the motor; a control unit that controls the motor to raise and lower the shaft; a threshold setting unit that sets a predetermined threshold, the control unit operates the motor to lower the shaft on which the component holder holds the component, sets a thrust limit value of the motor to a first limit value before a rate of change in the thrust of the motor measured by the thrust measuring unit exceeds the predetermined threshold, and changes the thrust limit value of the motor to a second limit value smaller than the first limit value after the rate of change in the thrust of the motor exceeds the predetermined threshold; the threshold setting unit sets the predetermined threshold between a pre-contact change rate, which is the maximum value of the change rate of the thrust of the motor before the component held by the component holding unit comes into contact with the board, and a post-contact change rate, which is the minimum value of the change rate of the thrust of the motor after the component held by the component holding unit comes into contact with the board.

2. The component mounting device according to claim 1 , wherein the threshold setting unit sets the predetermined threshold based on information about the hardness of the board.

3. 3. The component mounting device according to claim 1, wherein the threshold setting unit calculates a difference between the thrusts of the motor measured by the thrust measuring unit at predetermined time intervals as a rate of change.

4. A component mounting method in which a component is held by a component holder attached to the lower end of a shaft that is raised and lowered by a motor, and the component is mounted on a board, setting a thrust limit value of the motor to a first limit value; activating the motor to lower the shaft; When a rate of change in the thrust of the motor measured by a thrust measuring unit exceeds a predetermined threshold, the thrust limit value of the motor is changed to a second limit value that is smaller than the first limit value, a pre-contact change rate, which is the maximum value of the change rate of the thrust of the motor before the component held by the component holder comes into contact with the board, and a post-contact change rate, which is the minimum value of the change rate of the thrust of the motor after the component held by the component holder comes into contact with the board.

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