JP3172286B2 - Pressing force measuring device in electronic component mounting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component mounting apparatus for mounting various electronic components, such as semiconductor chips, which are vulnerable to pressing force, at predetermined positions on a printed circuit board. The present invention relates to an apparatus for measuring a pressing force acting on a part.

[0002]

2. Description of the Related Art Conventionally, an apparatus for automatically surface mounting electronic components 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 components. The mechanism is X axis, Y axis and Z axis.
It is attached to a reciprocating device that can control the movement in the axial direction.

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

When the electronic component contacts the printed circuit board, the suction head mechanism is further driven downward to press the electronic component against an adhesive layer or a solder paste layer on the surface of the printed circuit board, and fix the electronic component to the printed circuit board. Alternatively, it is temporarily fixed.

Thereafter, the suction head mechanism is returned to the component supply device, and the operation shifts to the surface mounting operation of the next electronic component.

[0006]

Incidentally, in the conventional surface mounting apparatus, the lifting and lowering operation of the suction head mechanism is performed by driving the cam mechanism. Here, the cam mechanism presses the suction nozzle against the electronic component on the component supply device, and when pressing the sucked electronic component against the printed circuit board, an excessive impact force or pressing force is not applied to the electronic component. The cam curve is designed.

However, with the diversification of types of electronic components in recent years, the shapes, dimensions (thickness), and materials of electronic components have been diversified. For example, delicate electronic components such as IC (LSI) bare chips have also appeared, and the mechanical properties of electronic components to be surface-mounted by a surface mounting apparatus greatly differ depending on the type of electronic component.

Therefore, in the surface mounting using the surface mounting apparatus, it is necessary to limit the pressing force applied at the time of suction holding and at the time of surface mounting to an appropriate value for each type of electronic component.

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

However, an apparatus employing a drive method using a linear motor has a problem that the apparatus is complicated and heavy. Further, in a device using a compression spring or a device using an electropneumatic regulator, it is difficult to accurately control the pressing force actually acting on the electronic component.

An object of the present invention is to provide an electronic component mounting apparatus having a simple configuration capable of accurately controlling a pressing force acting on an electronic component.

[0012]

An electronic component mounting apparatus according to the present invention provides a suction head mechanism (4) for sucking and holding an electronic component.
A head lifting mechanism (5) for moving the suction head mechanism up and down toward the printed circuit board at the electronic component mounting position; and a lifting and lowering of the printed circuit board between the standby position below the suction head mechanism (4) and the electronic component mounting position. It has a substrate lifting mechanism (8) for moving.

The substrate elevating mechanism (8) has a pin erected plate (89) disposed on an elevating plate (85) to which the reciprocating device is linked, and a pin erecting plate (89) between And a force sensor (6) interposed therebetween. A plurality of board support pins (87) that should directly support the printed board are pierced and erected in the pin erected plate (89) so as to be able to move up and down.

A force sensor (6) constituting a pressing force measuring device
Is a pair of electrodes disposed on both sides of the pressure-sensitive conductive rubber sheet (61), and the base end of each substrate support pin (87) is in contact with the surface of the force sensor (6). I have. The pair of electrodes are connected to a measurement circuit (9), and are connected to a pressure-sensitive conductive rubber sheet.
The pressing force acting on (61) is measured.

[0015]

[Advantage] When mounting electronic components, a suction head mechanism is used.
With (4) raised, the printed circuit board is first set to the standby position. Next, the board lifting / lowering mechanism (8) operates to raise the printed board from the standby position to the electronic component mounting position,
Positioned.

Next, the suction head mechanism (4) holding the electronic components by suction is lowered toward the printed board at the electronic component mounting position by driving the head lifting / lowering mechanism (5). The suction head mechanism (4) is further driven downward by the head lifting / lowering mechanism (5) even after the electronic component comes into contact with the printed circuit board, whereby the electronic component is pressed against the printed circuit board.

At this time, the pressing force received by the electronic component also acts on the printed circuit board, and the pressing force received by the printed circuit board is received by a plurality of substrate support pins (87). The force received by each substrate support pin (87) directly acts on the pressure-sensitive conductive rubber sheet (61) of the force sensor (6). As a result, the pressure-sensitive conductive rubber sheet (61) is deformed in the thickness direction, and the electric resistance value in the thickness direction changes. Therefore, the measurement circuit (9)
By applying a constant current between the pair of electrodes, the change in resistance can be detected as a change in voltage. By detecting this voltage change by the measuring circuit (9), the pressing force acting on the pressure-sensitive conductive rubber sheet (61), that is, the pressing force received by the electronic component is measured.

The output of the measuring circuit (9) can be used for drive control of the head lifting / lowering mechanism (5) at the time of mounting the electronic component, whereby the pressing force acting on the electronic component is suppressed to a regulated value or less. Thus, damage to the parts due to excessive pressing force is prevented.

[0019]

In the electronic component mounting apparatus according to the present invention, the suction head mechanism (4) has a conventional structure and the substrate lifting mechanism (8) has a simple structure in which a force sensor (6) is incorporated. The pressing force acting on the part can be accurately measured.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIGS. 1 to 5 show a specific configuration of an electronic component automatic mounting apparatus (2) in which the present invention is to be implemented. First, the mechanism of the apparatus will be described.

As shown in FIG. 1, an electronic component automatic mounting device (2)
Is a board transfer mechanism for transferring the printed circuit board (31) from the supply side (left side) to the unloading side (right side) on the machine base (20).
(7) and a board elevating mechanism (8) for moving the printed board (31) up and down at the electronic component mounting position as described later. The board transfer mechanism (7) includes a pair of guide rails (32) and (33) for guiding the horizontal movement of the printed board (31).

Further, a component tray (30) for mounting electronic components is provided on the machine base (20), and further, tapes (38) are provided on both sides of the conveyors (32) and (33). A tape feeder unit (37) for feeding the electronic components one pitch at a time and a component magazine (39) for storing the electronic components in a vertically stacked state are arranged.

An XY table for moving the suction head mechanism (4) in the X-axis direction and the Y-axis direction is composed of a pair of Y-axis guide bodies (35) which are installed on the machine base (20) in the Y-axis direction. (36) and an X that is slidably engaged with the guide body and is driven in the Y-axis direction.
The suction head mechanism (4) includes an axial guide body (34).
It is mounted on the X-axis direction guide body (34) so as to be able to reciprocate in the X-axis direction.

As shown in FIG. 2, the suction head mechanism (4)
A Z-axis guide body (53) slidably engaged with the axial guide body (34), the Z-axis guide body (53) includes:
A ball screw (52) vertically supported by a pair of bearings (55) (56) is arranged. An elevating block (54), which is slidably engaged with the Z-axis direction guide body (53) and guided up and down, is screwed to the ball screw (52).

A motor (51) installed on a Z-axis direction guide (53) is connected to the upper end of the ball screw (52). A support arm (40) projecting from the suction head mechanism (4) is fixed to the lifting block (54). Therefore, when the ball screw (52) rotates by driving the motor (51),
The lifting block (54) is driven up and down by the screw thrust, and the suction head mechanism (4) is moved up and down accordingly.

The suction head mechanism (4) includes an outer cylinder (44) vertically supported by a support arm (40) via bearings (401) and (402) as shown in FIG. The inner cylinder (45) is disposed inside the parentheses. The inner cylinder (45) can move axially with respect to the outer cylinder (44) and cannot rotate relative to the outer cylinder (44) via bearings (403) (403) disposed between the inner cylinder (45) and the outer cylinder (44). Is engaged. Also, inner cylinder
A spring (49) is interposed between the (45) and the outer cylinder (44), and the inner cylinder (45)
Is urged downward with respect to the outer cylinder (44).

The central hole (46) of the inner cylinder (45) is connected to a vacuum pump (not shown). Also, at the lower end of the inner cylinder (45),
A pair of narrow pressure arms (42) (4) that hold the suction nozzle (41)
2) is installed.

As shown in FIG. 4, the pair of narrow pressure arms (42) are pivotally connected to the lower end of the inner cylinder (45), and a spring (43) is stretched between the two arms. As a result, the suction nozzle (41) is detachably held by the two narrow pressure arms (42) and (42) with a narrow pressure, and in the held state, the nozzle hole and the central hole (46) of the inner cylinder (45) are held. Will be in communication.

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

The substrate lifting mechanism (8) is provided with the substrate transport mechanism.
The base (82) is disposed below a pair of guide rails (32) and (33) constituting the (7), and is fixed at a fixed height position by four columns (81) as shown in FIG. ), Four shafts (84) whose up and down movement are respectively guided by guide members (83) provided at the four corners of the base (82), and a lifting and lowering fixed to the upper ends of these shafts (84). Board (85). An air cylinder (88) is provided on the base (82), and the rod end of the air cylinder (88) is connected and fixed to the back surface of the elevating plate (85).

On a lifting plate (85), a force sensor (6) described later is provided.
A pin planting plate (89) is installed via the. Pin standing board (89)
Has a number of holes (86) formed at a constant pitch, and a plurality of substrate support pins (87) are removably fitted in these holes (86).

Accordingly, the lifting plate (85) is provided with four shafts (8).
4) is driven up and down by the air cylinder (88) while being guided by the guide member (83), whereby the plurality of substrate support pins (87) move up and down.

As shown in FIG. 6, the force sensor (6) comprises a first electrode film (62) comprising a plurality of strips extending in one direction, on both sides of a pressure-sensitive conductive rubber sheet (61). A second electrode film (63) composed of a multiplicity of strip electrode strips extending in a direction orthogonal to the strip electrode strip is adhered, and insulating films (64) and (65) are arranged on both sides thereof. You. Thus,
X is formed by the first and second pair of electrode films (62) and (63).
A Y matrix is formed.

Further, connectors (66) and (67) for electrically connecting the base ends of the respective strip electrode pieces are attached to the respective electrode films (62) and (63). Although the electrode films (62) and (63) are composed of a number of strips of electrode strips and have a comb shape as described above, they are drawn in a rectangular sheet shape in FIG. 5 and FIG. In FIG. 6, each strip electrode piece is simplified by drawing it with one line.

FIG. 7 shows the configuration of a measuring circuit (9) to be connected to the above-mentioned force sensor (6). Selection circuits (91) and (92) are connected to the electrode films (62) and (63) via connectors (66) and (67), and the selection circuits are switched and controlled by a microcomputer described later.
The above-described XY matrix constituted by the electrode films (62) and (63) is line-sequentially scanned, and one intersection of the XY matrix is selected at any time.

The electric resistance R _XY in the thickness direction of the pressure-sensitive conductive rubber sheet (61) at the selected intersection is provided with a constant current source (93).
Is supplied, the potential difference generated across the resistor is amplified by the differential amplifier (94), and the voltage signal V
Output as ₀ .

The sense of an arbitrary position is pressed in the pressure introducing conductive rubber sheet (61), when the sheet thickness is changed, the changed portion of the thickness of the resistance value changes, appears as a change of the voltage signal V ₀ . Therefore, by detecting the change in the voltage signal V ₀ , the distribution of the pressing force acting on the pressure-sensitive conductive rubber sheet (61) can be measured.

FIGS. 8 and 9 show the electronic component mounting operation in the electronic component automatic mounting apparatus (2) described above. Here, the board transfer mechanism (7) is provided with a pair of guide rails (32) (3
A number of rollers (72) are arranged along 3), and these rollers
(72) is driven by a motor (71), and the printed circuit board (31)
Is transported in the horizontal direction.

The substrate elevating mechanism (8) moves the plurality of substrate support pins (87) on the elevating plate (85) up and down by driving the air cylinder (88) as described above. 8
As described above, in the process of transporting the printed board (31) in the horizontal direction, the elevating plate (85) and the board support pins (87) are waiting at the lower end. The number and positions of the board support pins (87) are appropriately determined according to the shape of the printed board (31) and the electronic component mounting position.

When the printed board (31) is transported to a standby position just below the electronic component mounting position and is positioned by a known positioning mechanism, the air cylinder (88) of the board lifting / lowering mechanism (8) operates as shown in FIG. Then, the lifting plate (85) and the substrate support pins (87) are raised. As a result, the printed board (31) is lifted by the plurality of board support pins (87), and both ends of the board are stopped by the stoppers (32a) (33) of the guide rails (32) (33).
In the state of contact with a), the electronic component is set at a predetermined electronic component mounting position.

Next, the suction head mechanism (4) is lowered by the drive of the head lifting / lowering mechanism, and the electronic component (3) held by the suction nozzle (41) is mounted at a predetermined position on the printed board (31).
The head lifting mechanism drives the suction head mechanism (4) downward even after the electronic component (3) comes into contact with the printed board (31), thereby pressing the electronic component (3) onto the printed board (31). .

At this time, the pressing force acting on the electronic component (3) acts as a load on the printed board (31), and the load is applied to a plurality of board supporting pins () supporting the printed board (31). 87).

Since each substrate support pin (87) is vertically movably fitted to the pin planting plate (89), the force acting on the substrate support pin (87) is directly applied to the pressure-sensitive conductive member of the force sensor (6). Rubber sheet
(61).

FIG. 10 shows a state in which the pressure-sensitive conductive rubber sheet (61) is pressed by the base end of the substrate support pin (87), and the thickness is changed. As described above, the pressure-sensitive conductive rubber sheet (61) has a property that the resistance value changes according to the received load. For example, when the printed board (31) is supported by the six board support pins (87), FIG. Alternatively, a resistance value distribution as shown in FIG. 12 occurs. FIG. 11 shows a resistance value distribution in a state where the printed board (31) is raised by the board lifting / lowering mechanism (8) and pressed against the stoppers (32a) (33a) of the guide rails (32) (33) with a constant force. Figure 1
Then, the electronic components are operated by the operation of the head lifting mechanism
(3) shows a resistance value distribution in a state of being pressed on the printed circuit board (31).

In FIG. 11, low peaks of substantially the same level are generated at locations corresponding to the six board support pins, whereas in FIG. 12, locations A corresponding to the mounting position of the electronic component (3) are shown. And there are high mountains. Therefore, when the pressure distribution of FIG. 11 is subtracted from the pressure distribution of FIG. 12 and the result is integrated over the entire pressure-sensitive conductive rubber sheet, the total value of the pressing force acting on the pressure-sensitive conductive rubber sheet, that is, the electronic component ( The pressing force received by 3) is detected.

FIG. 13 shows a drive system of a suction head mechanism lifting / lowering drive motor (51) of the automatic electronic component mounting apparatus (2). In controlling the suction head mechanism elevating drive motor (51), a force sensor provided in the substrate elevating mechanism (8) is used.
The output of (6) is supplied to the measuring circuit (9), and the voltage signal V ₀ obtained by this is supplied to the microcomputer (1) via the A / D converter (13).

Here, the microcomputer (1) switches and controls the measuring circuit (9), and thereby, as described above, the n × m (n) pixels (n) sequentially obtained from the XY matrix of the pressure-sensitive conductive rubber sheet (61). , M is the number of electrodes) to calculate the pressing force acting on the printed circuit board.

Further, the microcomputer (1) creates a motor control signal based on the calculated pressing force (hereinafter, referred to as a pressing force detection signal), and the signal is transmitted via the D / A converter (11) to the motor driver (1). 12), whereby the motor (51)
Is controlled.

In the control of the pressing force by the microcomputer (1), a pressing force having a step-like, ramp-like, or first-order lag-like waveform preset in the microcomputer (1) as shown in FIG. The motor (51) is feedback-controlled. That is, a deviation between the pressing force detection signal and the target value is determined by a driving system including the motor (51).
Enter in (21). Further, the pressing force obtained from the control target (22) including the electronic components and the printed circuit board is the force sensor.
It is detected by (6) and fed back to the microcomputer (1).

FIG. 15 shows an example of a pressing force detection signal by the above feedback control. The electronic component (3) and the printed circuit board (31) come into contact with each other at a point A in the figure, and accordingly, the pressing force detection signal rises to a point B slightly exceeding the target value level L. At this time, the rise time t ₀ of the pressing force detection signal
By taking the output of the force sensor into the microcomputer (1) with a sampling cycle much shorter than the above and executing the above-mentioned feedback control, the pressing force acting on the electronic component (3) is suppressed to an allowable value or less. Can be done.

The end point of the force control may be determined, for example, by lowering the target value to be output by the microcomputer to zero at an appropriate position, or by measuring the time elapsed from the point A or B in FIG. An appropriate time can be set by, for example, rotating the motor (51) in the ascending direction of the suction head mechanism (4) when a predetermined time has elapsed.

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

According to the electronic component automatic mounting device (2),
The pressing force acting on the electronic component is accurately measured, and by controlling the pressing force based on the measurement result, damage to the component due to excessive pressing force is reliably prevented.

The description of the above embodiments is for the purpose of illustrating the present invention, and should not be construed as limiting the invention described in the appended claims or reducing the scope thereof. 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 control of the head lifting / lowering mechanism 5 based on the detection signal of the force sensor 6 is not limited to the above-described feedback control, and it goes without saying that various known control methods can be adopted.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an external appearance of an electronic component automatic mounting apparatus according to the present invention.

FIG. 2 is a perspective view illustrating a configuration of a head lifting mechanism.

FIG. 3 is a sectional view of a suction head mechanism.

FIG. 4 is an enlarged sectional view of a nozzle portion of the suction head mechanism.

FIG. 5 is a perspective view of a substrate lifting mechanism.

FIG. 6 is an exploded perspective view showing a configuration of a force sensor.

FIG. 7 is a circuit diagram showing a configuration of a measurement circuit.

FIG. 8 is a partially cutaway front view showing the substrate elevating mechanism during conveyance of the printed circuit board.

FIG. 9 is a partially cutaway front view showing the board lifting / lowering mechanism in a state where the printed board is set at an electronic component mounting position.

FIG. 10 is an enlarged sectional view of the force sensor in a state where a pressing force is applied.

FIG. 11 is a graph showing a resistance value distribution of a pressure-sensitive conductive rubber sheet to which an initial pressing force has acted.

FIG. 12 is a graph showing a resistance value distribution of a pressure-sensitive conductive rubber sheet when an electronic component is mounted.

FIG. 13 is a block diagram illustrating a motor drive system of the electronic component automatic mounting apparatus.

FIG. 14 is a block diagram illustrating a pressing force control system of the electronic component automatic mounting apparatus.

FIG. 15 is a graph showing a change in a pressing force when a component is mounted.

[Explanation of symbols]

 (2) Electronic component automatic mounting device (3) Electronic components (31) Printed circuit board (4) Suction head mechanism (5) Head lifting mechanism (6) Force sensor (61) Pressure-sensitive conductive rubber sheet (62) Electrode film (63) ) Electrode film (7) Substrate transport mechanism (8) Substrate lifting mechanism

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-287338 (JP, A) JP-A-1-302900 (JP, A) JP-A-1-150829 (JP, A) JP-A-62-162 271689 (JP, A) JP-A-4-58124 (JP, A) JP-A-5-191097 (JP, A) JP-A-4-107997 (JP, A) JP-A-3-126100 (JP, U) 63-17984 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 5/00 H05K 13/04

Claims (1)

(57) [Claims] A suction head mechanism for sucking and holding an electronic component, and a head lifting mechanism for moving the suction head mechanism up and down toward a printed circuit board at an electronic component mounting position.
And a board elevating mechanism (8) for moving the printed board up and down between the standby position below the suction head mechanism (4) and the electronic component mounting position. In an electronic component mounting apparatus configured by arranging a plurality of board support pins (87) for directly supporting a printed board on a board (85), a plurality of board support pins (87) are mounted on a lift board (85). Pin support plate (8) through which the board support pins (87)
9) is arranged, and between the lifting plate (85) and the pin planting plate (89),
A force sensor (6) having a pair of electrodes disposed on both sides of the pressure-sensitive conductive rubber sheet (61) is interposed, and the base end of each substrate support pin (87) contacts the surface of the force sensor (6). The pair of electrodes are connected to a measurement circuit (9), and the pressure-sensitive conductive rubber sheet is
A pressing force measuring device for an electronic component mounting device, wherein the pressing force acting on (61) is measured.