JPH05191097A - Pressure control device of component mounting device - Google Patents

Abstract

PURPOSE:To provide a component mounting device of simple structure which is able to accurately control pressure applied onto a component. CONSTITUTION:In a component mounting device which mounts an electronic component on the surface of a printed board with a suction head mechanism 4 linked to a head lift mechanism, a pressure sensor 6 is provided to measure pressure which acts on the electronic component attendant on a mounting operation, a microcomputer 1 forms control signals corresponding to the difference between a target value and a measured value of pressure applied onto the electronic component, and a head lift motor 51 is controlled in rotary speed basing on the control signal concerned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides various kinds of parts, such as electronic parts such as semiconductor chips and minute chip parts made of brittle material, which are vulnerable to pressure, at predetermined positions on a mounting surface such as a printed circuit board. The present invention relates to a component mounting device for mounting, and particularly to a device for controlling a pressing force when mounting a component.

[0002]

2. Description of the Related Art Conventionally, an apparatus for automatically surface-mounting an electronic component at a predetermined position on a printed circuit board is equipped with a suction head mechanism having a suction nozzle for vacuum-sucking the electronic component. The mechanism is X-axis, Y-axis and Z
It is attached to a reciprocating device capable of axial movement control.

In surface mounting using the above-mentioned surface mounting apparatus, first, the suction head mechanism is moved to the component supply section of the electronic component supply device, the electronic component is vacuum-sucked by the suction nozzle, and then the electronic component is printed. The electronic head is moved to a position above the board, the suction head mechanism is lowered, and the electronic component is set at a predetermined position on the surface of the printed board.

When the electronic component comes into contact with the printed circuit board, the suction head mechanism is further driven downward to press the electronic component against the adhesive layer or the solder paste layer on the surface of the substrate to fix the electronic component to the printed circuit board. Or temporarily fix it.

After that, the suction head mechanism is returned to the component supply device, and the operation for surface mounting the next electronic component is started.

[0006]

By the way, in the conventional surface mounting apparatus, the lifting / lowering operation of the suction head mechanism is performed by driving the cam mechanism. Here, the cam mechanism, when the suction nozzle is pressed against the electronic component on the component supply device, and when the sucked electronic component is pressed against the printed circuit board, so that excessive impact force or pressure does not act on the electronic component, The cam curve is designed.

However, with the recent diversification of types of electronic parts, the shapes, dimensions (thicknesses) and materials of electronic parts are diverse. For example, delicate electronic parts such as IC (LSI) bare chips have appeared, and the mechanical properties of electronic parts to be surface-mounted by a surface-mounting device greatly differ depending on the type of electronic parts.

Therefore, in the surface mounting using the surface mounting apparatus, it is necessary to limit the pressure applied to each of the electronic components at the time of suction holding and at the time of surface mounting to an appropriate value.

Therefore, as the surface mounting device, a device in which the suction head mechanism is driven by a linear motor (Japanese Patent Laid-Open No. 60-66500,
JP 63-232496), using a compression spring as a drive source
(JP-A-63-22292), which uses an electropneumatic regulator
(Japanese Patent Laid-Open No. 1-246899) and the like have been proposed.

However, the apparatus employing the linear motor drive system has a problem that the apparatus is complicated and heavy. In addition, it is difficult to accurately control the pressing force actually applied to the electronic component in the device using the compression spring and the device using the electropneumatic regulator.

An object of the present invention is to provide a component mounting apparatus having a simple structure capable of accurately controlling the pressure applied to the component.

[0012]

A pressing force control device in a component mounting apparatus according to the present invention applies a target value setting means for setting a target value of a pressing force to be applied to a component and an actual mounting operation to the component. And a drive control means for driving the pressurizing mechanism according to the deviation of the measured value from the target value of the pressing force.

A component mounting apparatus for surface mounting electronic components includes a suction head mechanism for sucking and holding electronic components, and a reciprocating device for reciprocating the suction head mechanism toward a printed circuit board. The reciprocating device constitutes the pressing mechanism.

In the target value setting means, a step-like waveform or a ramp-like or first-order lag-like waveform in which the rising of the pressing force gradually increases toward the final target value is set as the target value of the pressing force. ing.

The pressing force control device in the component mounting apparatus according to the present invention is realized by, for example, a feedback control system that controls the pressurizing mechanism to a target value based on the detected value of the pressing force.

[0016]

When the component mounting apparatus presses the component on the mounting surface toward the mounting surface and presses the component onto the mounting surface, the pressing force acting on the component is, for example, a stepped waveform target. The value increases according to the input of the value, and the change in the pressing force until the target value is reached is detected. Then, a deviation between the detected pressing force and the target value is calculated, and a control signal corresponding to the deviation is fed back to the pressurizing mechanism in real time to adjust the pressing force.

As a result, the pressing force is controlled to a value that follows the target value as much as possible, and damage to parts due to the action of excessive pressing force is prevented.

If a ramp-shaped or first-order lag waveform is set as the target value of the pressing force, even if the parts or the parts mounting surface is made of a material having extremely high hardness, the parts receive the pressing force. Rises slowly, and excessive overshoot is prevented from occurring.

[0019]

According to the pressing force control device in the component mounting apparatus of the present invention, the feedback control system including the pressing force measuring means is simply formed to realize a simple structure.
It is possible to accurately limit the pressure applied to the parts.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 to FIG. 8 show a specific structure of an electronic component surface mounting apparatus for carrying out the present invention. First, the mechanism of the apparatus will be described.

As shown in FIG. 4, the surface mounting apparatus (2) is provided with a pair of conveyors (32) (33) for transporting the printed circuit board (31) on the machine base and mounting electronic parts. And a tape feeder unit (37) for feeding the electronic parts housed in the tape (38) one pitch at a time on both sides of the conveyor (32) (33) with a parts tray (30) for There is a parts magazine (39) that stores the parts vertically stacked.

The XY table for moving the suction head mechanism (4) for sucking and holding electronic parts in the X-axis direction and the Y-axis direction is a pair of Y-axis directions which are erected on the machine base in the Y-axis direction. A guide body (35) (36) and an X-axis direction guide body (34) slidably engaged with the guide body and driven in the Y-axis direction,
The suction head mechanism (4) is mounted on the X-axis direction guide body (34) so as to be capable of reciprocating in the X-axis direction.

As shown in FIG. 5, the suction head mechanism (4) is X-shaped.
It is held on the axial guide body (34) via a head lifting mechanism (5). The head lifting mechanism (5) includes a Z-axis direction guide body (5) slidably engaged with the X-axis direction guide body (34).
3), and a pair of bearings (5
5) A ball screw (52) is arranged vertically supported by (56). The ball screw (52) has a Z-axis direction guide body.
An elevating block (54) slidably engaged with (53) and guided for vertical movement is screwed.

A motor (51) installed on the Z-axis direction guide body (53) is connected to the upper end of the ball screw (52). A support arm (40) protruding from the suction head mechanism (4) is fixed to the lifting block (54).

Therefore, when the ball screw (52) is rotated by the drive of the motor (51), the lifting block is lifted by the screw thrust.
The (54) is driven up and down, and along with this, the suction head mechanism (4)
Will move up and down.

As shown in FIG. 6, the suction head mechanism (4) comprises an outer cylinder (44) vertically supported by a support arm (40) via bearings (401) (402). ), The inner cylinder (45) is arranged inside, and is engaged with the outer cylinder (44) so as to be axially movable and non-rotatable.

The central hole (46) of the inner cylinder (45) is connected to a vacuum pump (not shown). Further, a pair of pinching arms (42) (42) for pinching and holding the suction nozzle (41) is provided at the lower end of the inner cylinder (45).
Is attached.

A disk-shaped spring plate member (61) as shown in FIG. 7 is screwed and fixed at the outer peripheral portion to the opening end surface of the drum member (49) integrally provided at the lower end portion of the outer cylinder (44). The spring plate member
The inner peripheral portion of the (61) is screwed and fixed to the inner cylinder (45).
In addition, the strain gauges (62) (62) are attached to the surface of the spring plate member (61).
Is adhered to form a pressure sensor (6) for measuring the impact force or the applied pressure to the electronic component as described later.

The pair of pinching arms (42, 42) are pivotally connected to the lower end of the inner cylinder (45) as shown in FIG. 8, and a spring (43) is stretched between both arms. As a result, the suction nozzle (41) is removably clamped and held by both clamping arms (42) and (42), and in the state where it is retained, the nozzle hole has the inner cylinder (45).
It will communicate with the central hole (46) of the.

As shown in FIG. 6, a pulley (47) driven by a timing belt (48) is attached to the outer cylinder (44), and the outer cylinder (44) is rotated at a predetermined angle by a drive mechanism (not shown). The direction of the electronic component (3) held by the suction nozzle (41) can be arbitrarily changed by rotating the electronic component (3) by only rotating it.

The operation of the surface mount device (2) is controlled by the microcomputer (1) shown in FIG.
That is, in the control of the elevation drive motor (51) of the surface mount device (2), the output signal of the pressure sensor (6) is supplied to the microcomputer (1) via the A / D converter (13),
In response to this, the microcomputer (1) creates a motor control signal, and this signal is sent to the motor driver (12) via the D / A converter (11), which controls the rotation of the motor (51). Will be done.

The control of the motor (51) based on the detection signal of the pressure sensor (6) will be described below. The motor (51)
The control of (1) is made up of two speed control in the first half and pressure control in the second half before and after the time when the electronic component (3) collides with the surface of the printed circuit board (31) and an impact force is generated.

Speed Control In the speed control of this embodiment, the suction head mechanism is used.
Electronic component (3) held by (4) printed circuit board (31)
The speed of lowering is at least the printed circuit board.
After approaching (31), control to a constant value. FIG. 3 shows the speed control procedure.

First, the microcomputer recognizes the type of the electronic component held by the suction head mechanism from the information registered in advance (S1), and according to the type, the standard without the risk of damage due to impact force. A typical descent speed (S
2).

Next, the electronic component is actually mounted on the printed circuit board at the standard lowering speed.
(S3), the peak value of the impact force at that time is sampled by the detection signal from the pressure sensor (S4).

FIG. 11 is a graph plotting a plurality of sampling results, and it can be seen that there is a linear relationship between the peak value of the impact force and the collision speed. Therefore, the slope of the straight line in FIG. 11, that is, the peak value of the impact force / the coefficient of the descent rate is found from the sampling data obtained by the trial of the mounting operation (S3).

Therefore, as shown in FIG. 3, based on the coefficient of the impact force peak value / falling speed (S5), an optimum collision velocity slightly lower than the allowable limit of the impact force received by the electronic component to be mounted is set. (S6), a control signal for realizing the motor rotation speed corresponding to the collision speed is generated, and the D / A
Send to converter. As a result, the suction head mechanism descends and the electronic component collides with the printed circuit board.

It is judged whether or not the value of the rising process of the impact force at the time of collision exceeds a predetermined value (S8), and when it exceeds the predetermined value, the pressure control described later is switched to (S9).

Pressure control In the pressure control, the electronic component (3) installed on the surface of the printed board (31) by the speed control is further added to the printed board (31).
It is a control that is performed in the process of pressing to the side and completing the mounting of electronic parts, and the motor (51) is feedback-controlled with the rising waveform of the pressing force preset in the microcomputer (1) as the target value, It suppresses the pressure applied to parts to below the specified value.

FIG. 2 shows a feedback control system for pressure control. In the microcomputer (1),
A change in the pressing force that rises stepwise to a predetermined target value is set in advance, and a deviation from the pressing force detected by the pressure sensor (6) is set as a target value, and a drive system including the motor (51) is set. Enter in (21). Further, the pressing force obtained from the controlled object (22) including the electronic parts and the printed circuit board is detected by the pressure sensor (6) and fed back to the microcomputer (1).

FIG. 12 shows a step input response in the above pressure control. The output of the pressure sensor rises from the time when the electronic component held by the suction nozzle comes into contact with the printed circuit board, then increases toward the target value, and a peak is generated. At this time, during the period t0 from the starting point A of the pressure sensor output to the peak point B, the pressure sensor output is taken into the microcomputer at a sufficiently short sampling cycle to obtain the output sensor output value and the target value. A control signal corresponding to the deviation is generated in real time and supplied to the head lifting mechanism.

As a result, a large peak does not occur in the output of the pressure sensor, and the maximum pressure applied to the electronic component can be suppressed below the allowable value. Then, after that, the electronic component is pressed against the solder paste layer on the printed circuit board and surface-mounted without being damaged by the action of the appropriate pressing force that matches the target value.

At the end of the pressure control, for example, the pressing force pattern as the target value to be output by the microcomputer is lowered to zero at an appropriate position as shown in FIG. 12, or the rise of the pressure sensor output is started. It is possible to set an appropriate time point by a method of measuring an elapsed time from the time point A or the peak time point B, and reversing the lifting motor (51) when a certain time has elapsed.

The pressure control is performed by the suction head mechanism (4).
The electronic component suction operation is also executed, and damage to the electronic component due to pressurization of the suction nozzle is prevented.

When the mounting of the electronic component is completed, the process proceeds to the mounting operation of the next electronic component, and the same processing is repeated.

FIG. 9 shows another example of the structure of the suction head mechanism (4). Here, the drum member is attached to the upper end of the outer cylinder (44).
(404) is attached, the disk-shaped spring plate member (63) is fixed to the lower opening end surface of the drum member (404), and the strain gauge (64) is provided on the surface of the spring plate member (63). Is attached. In addition, a coil spring (405) and a pressing member (406) are installed in the outer cylinder (44) to urge the upper end of the inner cylinder (45) toward the back surface of the spring plate member (63). ing.

In the suction head mechanism, the strain gauge (64) receives a load corresponding to the biasing force of the coil spring (405) as a preload. Therefore, the pressing force received by the electronic component is calculated by subtracting the biasing force of the coil spring (405) from the pressing force detected by the strain gauge, or the biasing force of the coil spring (405) is used as a reference point (zero point) to determine the electronic force. It is necessary to measure the pressure applied to the parts.

The strain gauges (62) and (64) are not limited to those made of a general metal resistance wire, but semiconductor strain gauges can be adopted.

FIG. 10 shows still another example of the structure of the suction head mechanism (4). Here, as a pressure sensor, FIG.
Instead of the strain gauge of, the piezoelectric element (65) is attached to the outer cylinder (44).
And the inner cylinder (45). The piezoelectric element (65) is made of a piezoelectric material such as quartz or lead zirconate titanate, and generates an electric potential according to an external force acting. Therefore, the pressure applied to the electronic component can be detected by measuring the potential.

Further, instead of the piezoelectric element (65), a pressure-sensitive conductive rubber can be arranged. Pressure-sensitive conductive rubber is
It has a property that the resistance value changes depending on the load received. By measuring the change in the resistance value, it is possible to detect the pressing force applied to the parts.

The target value of the pressing force is not limited to the one having a waveform which rises stepwise, and the ramp-shaped waveform A as shown in FIG. 13 or the first-order lag-shaped waveform A as shown in FIG.
Can be set. These waveforms are particularly effective when the material of the electronic component and the printed circuit board is made of a material having high hardness such as ceramics, and a stepped waveform may cause a large overshoot.

The waveform B in FIG. 13 shows the response of the pressing force to the ramp-shaped target value waveform A. The waveform B in FIG. 14 shows the response of the pressing force to the target value waveform A obtained by processing the target value waveform in FIG. 13 with a first-order lag filter.

In the response waveform B of FIG. 13, the overshoot at the time of rising is suppressed to a low level, and the fluctuation range after that is significantly reduced. Furthermore, in the response waveform B of FIG. 14, the overshoot at the time of rising has completely disappeared.

According to the surface mounting apparatus described above, by applying an appropriate pressing force to the electronic component, reliable and quick surface mounting operation can be realized without damaging the electronic component.

The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope. Further, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope described in the claims.

For example, the present invention can of course be implemented in various component mounting apparatuses other than the surface mounting apparatus, such as an automatic assembly apparatus using a robot.

[Brief description of drawings]

FIG. 1 is a block diagram showing a motor drive system of a surface mounting device to which the present invention is applied.

FIG. 2 is a control block diagram showing a pressure control system.

FIG. 3 is a flowchart showing a speed control procedure.

FIG. 4 is a perspective view showing an appearance of a surface mount device.

FIG. 5 is a perspective view showing an appearance of a suction head mechanism attached to a head lifting mechanism.

FIG. 6 is a cross-sectional view of a suction head mechanism.

FIG. 7 is a partially cutaway perspective view showing the configuration of a pressure sensor.

FIG. 8 is an enlarged sectional view of a nozzle portion of the suction head mechanism.

FIG. 9 is a cross-sectional view showing another configuration of the suction head mechanism.

FIG. 10 is a sectional view showing still another configuration of the suction head mechanism.

FIG. 11 is a graph showing a relationship between a collision speed and a peak value of impact force.

FIG. 12 is a waveform diagram of a pressure sensor output by pressure control.

FIG. 13 is a waveform diagram showing a response of a pressing force to a ramp-shaped target value waveform in pressure control.

FIG. 14 is a waveform diagram showing a response of a pressing force to a first-order delay target value waveform in pressure control.

[Explanation of symbols]

 (1) Microcomputer (2) Surface mount device (3) Electronic component (4) Suction head mechanism (41) Suction nozzle (5) Head lifting mechanism (51) Motor (6) Pressure sensor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Michio Kunimitsu 2-18-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A target for setting a target value of a pressing force to be applied to a component in a component mounting apparatus that presses a component on the mounting surface toward the mounting surface by a pressure mechanism to crimp the component to the mounting surface. A value setting means, a measuring means for measuring a pressing force applied to a component by an actual mounting operation, and a drive control means for driving a pressurizing mechanism according to a deviation of the measured value from a target value of the pressing force. A pressure control device for a component mounting device, which is characterized in that 2. A component mounting device includes a suction head mechanism for suction-holding an electronic component, and a reciprocating device that reciprocates the suction head mechanism toward a printed circuit board. The pressing force control device according to claim 1, which is configured. 3. The ramp-shaped or first-order lag waveform in which the rise of the pressing force gradually increases toward the final target value is set in the target value setting means as the target value of the pressing force. The pressure control device described.