JPH07136868A - Pressing force controller in part mounting device - Google Patents

Abstract

PURPOSE:To provide a pressing force controller, which determined by itself a proper pressing force value to be applied to individual part to be mounted and mounts the part with the pressing force of this value, in a part mounting device. CONSTITUTION:A part mounting device, in which an electronic part on a printed circuit board is pressed onto the printed circuit board side so as to be press- fitted onto a mounting face by means of a pressing mechanism (pulse motor 104 and the like), is provided with a pressing force detector 208 measuring pressing force working on the electronic part in the actual mounting action. The device is provided with a control means consisting of a microcomputer 51, which determines an inflection point for this measured pressing force and controls driving of the pulse motor 104 so that the pressing force proper for the installation of the part is applied to the electronic part on the basis of the determined inflection point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component, particularly a QFP (Quad Flat Pa) having a large number of lead terminals.
(cage) and the like on a pressurizing force control device in a component mounting device for mounting a printed circuit board and the like on a printed board.

[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 attached to a reciprocating device capable of movement control in the X-axis, Y-axis, and Z-axis directions.

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

Then, 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 substrate surface to fix the electronic component to the printed circuit board or Temporarily fix.
Alternatively, the electronic component is held in contact with the printed circuit board, and high-energy light such as laser light or hot air is applied or applied to melt the solder, thereby soldering the electronic component.

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

By the way, in the conventional surface mounting apparatus, the raising / lowering operation of the suction head mechanism is performed by driving the cam mechanism. Here, the cam mechanism is a cam mechanism that prevents excessive impact force or pressure from acting on the electronic components when the suction nozzle is pressed against the electronic components on the component supply device and when the suctioned electronic components are pressed against the printed circuit board. The curve is designed.

However, with the recent miniaturization and diversification of electronic parts, the shape, size (thickness), and
In addition, there are a wide variety of materials, and the mechanical properties of electronic components to be surface-mounted greatly differ depending on the type of electronic component. Further, as described above, when soldering is performed while holding the electronic component without immediately raising the suction head after mounting the electronic component, the lead terminals of the electronic component should be in an appropriate state and all lead terminals should be It must be in contact with the printed circuit board.

Therefore, in order to automatically carry out surface mounting corresponding to the type of electronic component, the pressing force at the time of adsorption and holding and the pressing force applied at the time of surface mounting are set to appropriate values for each type of electronic component. Need to control.

Therefore, for example, it is considered that the suction head is provided with a pressing force detector for detecting the pressing force to control the pressing force applied to the electronic component when mounting the electronic component on the printed circuit board. . Specifically, the optimum pressure value is set as a target value in advance for each type of electronic component, and the pressure value is detected by the detector to detect the difference (deviation) from the target value. It is possible to control the descending speed and the descending distance of the suction head so that the deviation becomes zero.

[0010]

However, although the above-described pressure control device by feedback control enables surface mounting of many kinds of electronic parts, it sufficiently copes with variations among the same kind of electronic parts. I can't. For example, in an electronic component having a large number of lead terminals, as shown in FIG. 9, variations in the flatness of the tip portions of the lead terminals 500 (such as lifting of the terminal tip portions indicated by g in the figure) occur. However, in such an electronic component 501, some lead terminals come into contact with the printed circuit board prior to the other terminals to be deformed. Therefore, based on the target pressure value set uniformly for the same type of electronic component, If feedback control is performed, it is judged that the pressure value has reached the target pressure value before other terminals come into contact with the printed circuit board, and no further drop is made. There is a possibility that soldering may be performed even though they are not in contact with each other.

Further, in order to prevent the lead terminal from being bent back due to the suction nozzle descending too much, as shown in FIG. 10, a pressing force control device having a stopper member 503 attached to the tip end portion of the nozzle 502 is provided. Proposed.

However, as described above, the stopper member 50
When 3 is provided, the suction jig becomes large, and the contact space of the stopper member 503 needs to be provided on the printed circuit board, so that the printed circuit board design is restricted. In addition, when mounting the electronic component, it is general that the suction state of the electronic component is photographed by a video camera and the position is corrected, but this stopper member 503 is used.
However, there is also a drawback that it becomes an obstacle in recognizing the adsorption state. Further, in an electronic component in which the flatness of the lead terminals varies greatly, and particularly the lead shape is largely displaced upward, there is a possibility that the stopper member 503 may cause a lead terminal that does not contact the printed circuit board due to insufficient pushing amount. There is.

In view of the above-mentioned circumstances, the present invention is a component that can judge the appropriate pressure value to be applied to each component to be mounted by itself and mount the component with the pressure of that value. An object is to provide a pressing force control device in a mounting device.

[0014]

In order to solve the above-mentioned problems, a pressing force control device in a component mounting apparatus of the present invention applies a component on a mounting surface to a mounting surface side by a pressure mechanism, In a component mounting apparatus for crimping a component onto a mounting surface, a means for measuring a pressing force applied to the component during an actual mounting operation, a means for determining an inflection point of the measured pressing force, and It is characterized by further comprising: control means for controlling so that a pressing force suitable for mounting the component is applied to the component based on the bending point.

[0015]

The time when the inflection point occurs in the pressing force value measured during the mounting operation of each component corresponds to the time when all the lead terminals of the component come into contact with the mounting surface.
Therefore, the time when the above-mentioned inflection point occurs is the time when the pressing force suitable for mounting the component is applied to the component,
By maintaining the pressing force at the time when it is determined as this inflection point, or by applying a pressing force slightly higher or lower than this pressing force depending on various conditions, it is suitable for each individual component. The component can be mounted with the applied pressure.

Therefore, the drawbacks of the conventional feedback control, which cannot sufficiently deal with the unevenness of the flatness of the lead terminals of the individual parts, can be solved, and the stopper member is not necessary. Problems caused by using it will be eliminated.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments.

FIG. 1 is a perspective view showing a component mounting apparatus 301 for pressing a component on the mounting surface toward the mounting surface by a pressure mechanism to press the component on the mounting surface.

The component mounting device 301 includes a printed circuit board 3
A pair of conveyors 303, 304 for transporting 02,
A component tray 305 for mounting electronic components, a tape feeder unit 306 for supplying electronic components stored in a tape form, a component magazine 307 for supplying vertically stacked electronic components, and mounting these electronic components on a printed circuit board 302. X suction head mechanism 308
A drive device 309 that reciprocates in the axial direction and a drive device 310 that reciprocates in the Y-axis direction are provided.

FIG. 2 is an enlarged perspective view of the suction head mechanism 308 and its peripheral equipment. The suction head body 101 of the suction head mechanism 308 is connected to the ball screw 103 by the support body 102, and can be reciprocated in the Z-axis direction by driving the motor 104. Further, the support 105 that supports them is connected to the drive device 309 by the connecting member 106, and is capable of reciprocating in the X-axis direction.

FIG. 3 is a vertical sectional side view showing the internal structure of the suction head body 101. This head body 101
Includes an outer cylinder 201, a middle cylinder 202, and an inner cylinder 205.

The outer cylinder 201 is connected to the ball screw 103 by the support 102, and the pulse motor 104
Is rotated to reciprocate in the Z-axis direction. A motor 2 for rotating electronic parts is provided on the upper portion of the outer cylinder 201.
04 are arranged. The rotation shaft of the motor 204 is connected to the center of the upper portion of the middle cylinder 202 arranged inside the outer cylinder 201.

The middle cylinder 202 is a bearing 2 provided in the outer cylinder 201.
Although it is rotatably supported around the Z axis by 03, it cannot move in the Z axis direction. Also, the middle cylinder 2
A rear portion side of the inner cylinder 205 is inserted into the inner cylinder 02, and the inner cylinder 205 is supported by the middle cylinder 202 so as to be slidable in the Z-axis direction but not rotatable around the Z-axis. In the upper space of the middle cylinder 202, the pressing jig 210
It is slidable in the axial direction. The coil spring 20 is provided between the pressing jig 210 and the upper inner wall of the middle cylinder 202.
9, the inner cylinder 205 is biased downward by the coil spring 209.

A pressing force detector (load converter) 208 is attached to the rear end of the inner cylinder 205, and the pressure applied to the inner cylinder 205 in the Z-axis direction is determined by the pressing force detector 208 and the pressing jig. The pressure generated between the pressure sensor 210 and the pressure sensor 210 is detected by the applied pressure detector 208. Further, an exhaust pipe 206 is provided so as to project from the side surface of the inner cylinder 205 on the rear end side, and the exhaust pipe 206 is provided from openings 207 formed on the side portions of the outer cylinder 201 and the middle cylinder 202, respectively. It is put out of the cylinder. The exhaust pipe 206 is connected to an exhaust device (not shown), and the exhaust device exhausts the air in the inner cylinder 205 to reduce the pressure.
The electronic component 212 can be suction-held at the tip of the inner cylinder 205.

A suction jig 211 is detachably attached to the tip of the inner cylinder 205. The suction jig 211 is selected according to the electronic component 212 to be mounted from among those prepared in advance as a device capable of exhibiting an optimum suction action according to the shape of the electronic component 212, and is attached to the inner cylinder 205. Further, the electronic component 212 can be rotated at a predetermined angle by driving the motor 204 while the electronic component 212 is adsorbed to the inner cylinder 205.

Next, a series of component mounting operations in the component mounting apparatus configured as described above will be described.

First, the suction head mechanism 308 is moved above the component tray 305 by the driving devices 309 and 310, and the head main body 101 is lowered by the rotation of the motor 104 to push the suction jig 211 to the upper part of the electronic component 212. Then, the inside of the inner cylinder 205 is decompressed by the exhaust device to suck and hold the electronic component 212. After that, the suction head body 1
01 moves up while holding the electronic component 212 by suction, and moves to a position above the mounting position of the printed circuit board 302 by the driving devices 309 and 310. Then, the suction head main body 101 is lowered by the rotation of the motor 104, and the electronic component 2
12 is pressed against the printed circuit board.

At this time, the inner cylinder 205 slightly moves up and down according to the pressure applied to the electronic component 212, so that the pressure detector 208 is distorted by the pressure, and the pressure applied to the electronic component 212 is converted into an electric signal. And output. Then, based on the pressing force detected by the pressing force detector 208, an inflection point is calculated by a microcomputer (pressing force control device) described later, and based on this inflection point, the suction head main body 101 descends at an appropriate pressing force. Control to stop the operation.
After the electronic component 212 is pressed against the printed board in this way, the suction pressure of the electronic component 212 is released by manipulating the atmospheric pressure inside the inner cylinder 205.
By raising 01, a series of mounting operations is completed.

Next, the pressure control device will be described.

The pressing force control device detects the pressing force applied to the electronic component 212 by the pressing force detector 208, and based on this detection value, the movement of the suction head main body 101 in the Z-axis direction in the suction head mechanism 308, That is, the rotation of the pulse motor 104 is controlled.

FIG. 4 shows a block diagram of the pressure control device. The operation of this pressure control device is shown in the flowchart of FIG.

The microcomputer 51 has a ROM for storing a program for controlling the pressing force, a RAM for holding a pressing force detection value and a difference calculation value necessary for inflection point determination, and various kinds of data read from the RAM according to the program. CP that issues the command necessary to execute the pressure control based on the data
U (not shown) and the like.

First, the microcomputer 51 sets a predetermined lowering speed according to the type of the electronic component 212 sucked and held by the suction head body 101, and sends this speed command signal to the pulse generator 52. Then, the pulse generator 52
Generates a pulse wave according to the speed command and outputs it to the driver 53. The driver 53 drives the pulse motor 54 according to the pulse wave, and the descent of the suction head body 101 is thereby started (step 1).

The pressing force detector 208 detects the pressing force applied to the electronic component 212 and converts it into an electric signal. The pressing force detection signals that are sequentially output are sampled by the A / D converter 56, converted into digital signals, and input to the microcomputer 51 (step 2). The microcomputer 51 stores the pressing force detection value in the RAM and calculates the difference between the stored pressing force detection value and the newly input pressing force detection value to obtain the change amount of the pressing force value. Ask (step 3). Then, the noise component is removed from the change amount, and the change amount is RA.
It is stored in M (step 4), and it is determined whether or not it is in a steady state (whether the amount of change is constant) by comparison with the previously stored amount of change (step 5). The point at which the amount of change becomes constant is the inflection point of the pressing force.

If it is determined in step 5 that the steady state is not reached, the above steps 2 to 5 are repeated. On the other hand, if the steady state is determined, the suction head body 101
Is stopped (step 6), and the pressure control is terminated. After that, as described above, the pressure inside the inner cylinder 205 is operated to release the suction holding of the electronic component 212, and the suction head main body 101 is raised. The difference calculation in step 3 and the noise removal processing in step 4 may be performed in reverse order.

In this embodiment, the inflection point of the pressing force value is obtained by the difference calculation of the sampling values as described above.
Hereinafter, this will be specifically described.

FIG. 6 shows the measured value (detection voltage) of the pressing force received when the electronic component comes into contact with the printed circuit board and is further pushed down, and its change amount (voltage change amount ΔV).
Is shown. The horizontal axis in FIG. 6 represents the amount of depression, and the 0 point indicates the point where the tip of one of the lead terminals contacts the printed circuit board. The vertical axis represents the voltage value and the voltage change amount ΔV corresponding to the pressing force detected by the load converter, and is set to 1 mV≈1 gf. Here, the graph (a) shows the detected voltage value with respect to the depression amount, the graphs (b) to (e) show the voltage change amount ΔV obtained by the difference calculation, and (b) shows the difference Δ of the depression amount.
Z is 10 μm, (c) is ΔZ is 20 μm, (c) is ΔZ
Is 30 μm, (d) is ΔZ of 40 μm, and (e) is ΔZ of 50 μm.

The above voltage change amount is calculated by the following equation 1.

[0039]

[Formula 1] ΔV (Z) = V (Z) −V (Z−ΔZ))

For the above-mentioned pressure measurement, a thickness of 35
An electronic component 212 having a total of 144 copper leads each having a width of 150 μm and a width of 150 μm was used.
Then, the distance from the tip of the lead of this electronic component to the lower surface of the component main body was about 160 μm on average when actually measured. Further, what is located on the electronic part 212 is the suction jig 211, and a stopper member as in the prior art is not provided.

In the graph of the voltage change amount of FIG. 6, the voltage change amount continues to increase from the point where the push-down amount is 0 (up to point P) and the constant amount is constant (point P). From the point to the Q point) and a rapid increase section (a section after the Q point) where the amount of change sharply increases. Hereinafter, the relationship between these sections and the state of the electronic component on the printed circuit board will be described.

FIG. 8A shows a state in which the tips of the lead terminals have started to contact the printed circuit board 302, FIG. 8B shows a state in which all the lead terminals have contacted the printed circuit board, and FIG. As a result, the lead terminals warp and the lower surface of the component body contacts the printed circuit board 302.

The above-mentioned increase section occurs when the state shown in FIG. 9A shifts to the state shown in FIG. This is because the lead terminals have variations in flatness, and thus the number of lead terminals contacting the printed board increases as the electronic component is lowered.

The above-mentioned steady section occurs when the state shown in FIG. 9B shifts to the state shown in FIG. This is because all the lead terminals are in contact with the printed circuit board in the state of FIG. 7B, and even if the electronic component is pushed down, the pressure increases only in proportion to the bending amount of each lead terminal. Since the pressing force increases in proportion to the amount, the increasing tendency of the difference amount cannot be seen.

The abrupt increase section occurs when the pushing-down force is further applied to the electronic component in the state of FIG. This is because the main body of the electronic component 212 is made of a hard material such as resin and has almost no elasticity.

As described above, the distance from the lower surface of the electronic component body to the tip of the lead terminal is about 160 μm, but in the graph of FIG.
It occurs when μm. The value of 40 μm of the difference is due to the variation of the flatness of the lead terminals and the error of the parallelism of the measuring device.

Here, the state most suitable for mounting electronic components is the state shown in FIG. 8B. That is, all lead terminals are in contact with the printed circuit board and are not over-pressed. Therefore, in such a state, that is, when the steady section is entered in the graph of FIG. 6, in other words, when the point P (inflection point) of the graph is detected, the rotation of the pulse motor 104 is stopped. It is sufficient to stop the lowering of the suction head body 101.

In order to obtain the point P (inflection point) of the graph, mathematically, a second derivative operation may be performed, but the graph (a) of the detected voltage is a curve that rises smoothly,
Moreover, since it becomes a straight line that increases monotonically when it rises, and it is necessary to consider that noise is included in the measurement, the second derivative operation is not the best. For this reason, in the present embodiment, it is determined whether or not the vehicle enters the steady section by the difference calculation shown in the above-mentioned formula 1.

In order to determine whether or not the steady section is entered based on the difference value, new sampling values that are sequentially input and old values stored in the memory (for example, ΔZ value is 50
.mu.m, a difference value is calculated by comparison with a sampling value at a position 50 .mu.m before), and further, this difference value and
Since it is necessary to judge whether it is the steady state or the increase state with the new difference value calculated in the same way as above with the next new sampling value, the position slightly lowered from the ideal stop position is judged as the inflection point Tend to be.

Therefore, depending on the electronic parts to be handled, the lowering operation of the suction head body 101 is delayed from the ideal inflection point position, and it is expected that the suction head body 101 is pushed too far. In such a case, after the stopping operation, the pulse motor 104 may be reversely rotated by a predetermined amount to slightly raise the suction head body 101. It should be noted that the above-mentioned amount of rise is not more than the amount by which the lead terminal can be restored due to its spring property so that the lead terminal is not separated from the printed board by this rise.

Further, the above-mentioned tendency of excessive indentation is Δ
It becomes more remarkable as the Z value is increased. On the other hand, the smaller the ΔZ value, the more difficult it becomes to distinguish between the increasing section and the steady section as shown in graphs (c) to (e). Therefore, the ΔZ value is determined depending on the electronic parts to be handled by comparing and weighing the distinguishability and the delay characteristic of inflection point detection. If the lead terminal has a relatively high resistance, the ΔZ value can be increased. If the lead terminals have resistance, Δ
This is because, even if the Z value is increased to some extent, the above-mentioned increase section appears relatively conspicuously.

Further, depending on the amount of inclination of the printed circuit board set in the component mounting apparatus with respect to the Z axis, it is conceivable that some of the lead terminals will already warp when all of the lead terminals come into contact with the printed circuit board. ,
It is necessary to make the inclination of the printed circuit board with respect to the Z axis as small as possible. When the levelness cannot be sufficiently ensured on the conveyors 303 and 304 which convey the printed circuit board 302, for example, a vacuum suction device having the levelness is arranged below the stop position of the printed circuit board and the printed circuit board is conveyed. The printed circuit board may be temporarily fixed by vacuum suction to perform the electronic component mounting operation.

[0053]

As described above, according to the present invention, an appropriate pressing force value to be applied to each component to be mounted is judged by itself, and the component is mounted with the pressing force of that value. Therefore, the drawbacks of the conventional feedback control and the drawbacks of using the stopper member can be eliminated.

[Brief description of drawings]

FIG. 1 is a perspective view showing an appearance of a component mounting apparatus.

FIG. 2 is a perspective view showing an appearance of a suction head mechanism.

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

FIG. 4 is a block diagram showing a pressure control device of the present invention.

FIG. 5 is a flowchart showing a pressing force control operation of the present invention.

FIG. 6 is a graph showing a measured value (detection voltage) of a pressing force received when an electronic component comes into contact with a printed circuit board and is further depressed, and a change amount thereof (voltage change amount ΔV).

FIG. 7 is a perspective view showing an electronic component sucked by a suction jig having no stopper member.

FIG. 8A to FIG. 8C are explanatory diagrams showing states of lead terminals due to a drop of an electronic component.

FIG. 9 is a perspective view showing an electronic component having different lead terminals.

FIG. 10 is a perspective view showing an electronic component sucked by a suction jig provided with a stopper member.

[Explanation of symbols]

 51 Microcomputer 52 Pulse Generator 53 Driver 56 A / D Converter 101 Adsorption Head Main Body 104 Pulse Motor 208 Pressurization Pressure Detector 212 Electronic Component 302 Printed Circuit Board

Claims (1)

[Claims] 1. A component mounting apparatus that presses a component on a mounting surface to a mounting surface side by a pressure mechanism to crimp the component to the mounting surface, and measures a pressure applied to the component during an actual mounting operation. Means, a means for determining an inflection point of the pressing force, and a control means for controlling so that a pressing force appropriate for mounting the component is applied to the component based on the inflection point A pressure control device in a component mounting device.