JP2003121555A - Object detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an object detector by which the existence of an object to be detected can be detected correctly, irrespective of the temperature change. SOLUTION: In the object detector, with which the existence of a ball 2 on the rear surface of a suction head 31 is detected by a light blocking-type optical sensor, light projected from a projection part 43a along an optical axis a is received by a light-receiving part 43b, an electrical signal according to its light-receiving quantity in a threshold storage part 46, and the existence of the ball 2 is decided by a decision part 44. Since a change in an output voltage of the light-receiving part 43b is corrected by the temperature change due to the elapse of the operating time, the threshold value is corrected by a threshold correction part 45, on the basis of the output voltage of the light- receiving part 43b in a state of the ball 2 not existing on the optical axis a. Thereby, detection errors due to the temperature change is excluded, and a correct detection result can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detecting device for detecting the presence or absence of an object to be detected such as a semiconductor chip or a solder ball by a light-shielding type optical sensor.

[0002]

2. Description of the Related Art In the field of electronic component manufacturing, a transfer operation of picking up parts such as semiconductor chips and conductive balls by a transfer head and transferring them to a predetermined position is repeated. In this transfer work, the inspection to confirm whether the holding state of the parts by the transfer head is normal,
It is performed at a predetermined timing during the work process. For example,
After the pick-up operation, it is inspected whether or not the component is correctly held on the transfer head, and after the component is transferred to the work such as the substrate, whether or not the component remains on the transfer head. It is inspected and the correctness of the state is judged by the presence or absence of the detection target object.

As a method of detecting the presence or absence of the object to be detected, there is known a method of using a light shielding type optical sensor having a light projecting portion and a light receiving portion. In this method, the light projected from the light projecting unit of the optical sensor along the optical axis is received by the light receiving unit, and when an object is present on the optical axis, the light is blocked and the amount of light received changes. By utilizing this, the presence or absence of the detection target object is detected.

[0004]

However, the method using the above-mentioned light-shielding type optical sensor has a drawback that the detection accuracy is not stable when the temperature changes during the operation of the apparatus. That is, the light emitting element and the light receiving element used in the light projecting section and the light receiving section of the optical sensor have the characteristic that the sensitivity changes with temperature. For example, the amount of light emitted by the light emitting element changes with temperature, and Even if light enters, if the temperature changes, the strength of the electric signal output from the light receiving element changes.

Further, the mechanical parts to which these optical sensors are attached are also deformed by the temperature change, and when the optical axis moves due to this deformation, an error may occur in the amount of light received by the light receiving portion. As described above, the conventional object detection device using the light-shielding type optical sensor has a problem that it is difficult to obtain a correct detection result due to the temperature change.

Therefore, an object of the present invention is to provide an object detecting device capable of correctly detecting the presence or absence of an object to be detected regardless of temperature changes.

[0007]

An object detecting apparatus according to claim 1 is an object detecting apparatus for detecting the presence or absence of an object to be detected by a light-shielding type optical sensor, and the object detecting apparatus projects light along an optical axis. The light section, the light receiving section that receives the light projected by the light projecting section, and outputs an electric signal corresponding to the received light amount, and the electric signal is compared with the threshold value stored in the threshold value storage section. The determination unit determines whether or not the detection target object is present, and the threshold value correction unit that corrects the threshold value based on the electric signal in the state where the detection target object does not exist on the optical axis.

An object detecting device according to a second aspect is an object detecting device for detecting the presence or absence of an object to be detected by a light-shielding type optical sensor, and a light projecting portion for projecting light along an optical axis, and the light projecting part. A light amount control unit that controls the amount of light projected by the light unit, a light receiving unit that receives the light of the light projecting unit and outputs an electric signal according to the received light amount, and this electric signal is stored in the threshold value storage unit. By determining the presence or absence of the detection target object by comparing with the threshold value, by controlling the light amount control unit based on the electrical signal in the state that the detection target object does not exist on the optical axis A light amount level correction unit for correcting the light amount level of the light projecting unit is provided.

An object detecting apparatus according to a third aspect of the present invention is an object detecting apparatus for detecting the presence or absence of an object to be detected by a light-shielding type optical sensor, and a light projecting section for projecting light along an optical axis, and the light projecting section. A light receiving element that receives the light of the light section and outputs a primary electric signal having a magnitude corresponding to the amount of received light, and an output conversion section that converts the primary electric signal output from this light receiving element into a secondary electron signal and outputs the secondary electron signal. A light receiving unit provided, a determination unit that determines the presence or absence of a detection target object by comparing the secondary electric signal with a threshold value stored in a threshold value storage unit, and the detection target object on the optical axis. And a conversion level adjustment unit that changes the conversion level of the output conversion unit so that the magnitude of the secondary electric signal in a nonexistent state becomes a predetermined value.

According to the present invention, the threshold value, the light emission level of the light projecting unit or the light emitting level of the light projecting unit is determined based on the output value of the light receiving unit in the state where the object to be detected does not exist on the optical axis connecting the light projecting unit and the light receiving unit. By correcting any of the output levels of the output value conversion circuit that converts the amount of received light into an output value, it is possible to eliminate a detection error due to a temperature change and obtain a correct detection result.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 is a front view of a conductive ball mounting apparatus according to a first embodiment of the present invention.
3 is a block diagram showing a ball detection function of the conductive ball mounting apparatus according to the first embodiment of the present invention, and FIGS. 3 and 4 are explanations of ball detection processing of the conductive ball mounting apparatus according to the first embodiment of the present invention. 5 and 5 are explanatory views of the head height detection process of the conductive ball mounting apparatus according to the first embodiment of the present invention.

First, the overall structure of the conductive ball mounting apparatus will be described with reference to FIG. In FIG. 1, a positioning table 5 as a positioning means is provided on the base 4. The positioning table 5 is composed of a Y table 6 and an X table 7. A holder 8 is provided on the X table 7, and the holder 8 holds the work 9. Therefore, the work 9 is positioned at a predetermined position by driving the positioning table 5.

A ball supply unit 10 for the conductive balls 2 is arranged at the end of the base 4 opposite to the positioning table 5. The ball supply unit 10 comprises a ball tank 11, and a mesh plate 12 is provided on the bottom of the ball tank 11 at the top.
Is attached to the container 13 that is horizontally expanded. The mesh plate 12 is provided with an innumerable number of openings of sizes that the conductive balls 2 cannot pass through. Conductive balls 2 (hereinafter simply referred to as “balls” 2) are stored on the uppermost mesh plate 12. A nozzle 14 is arranged at the bottom of the ball tank 11, and the nozzle 14 is connected to a gas supply source (not shown). By supplying the gas to the nozzle 14, the gas blown upward from the nozzle 14 passes through the openings of the mesh plate 12 and is blown into the layer of the ball 2 to fluidize the ball 2.

Next, the suction head 31 for mounting the ball 2 will be described. Reference numeral 20 shown in FIG. 1 is a moving means for moving the suction head 31 between the ball supply unit 10 and the positioning table 5. The suction head 31 is a block 30.
The suction head 31 has a plurality of suction holes 31a on its lower surface. The block 30 is mounted on a vertical guide rail 25 provided on the front surface of the bracket 24 so as to be vertically movable.

A nut 28 is integrally provided on the block 30, and a vertical feed screw 26 is screwed onto the nut 28. Therefore, when the Z-axis motor 27 drives forward and backward and the feed screw 26 rotates forward and backward, the suction head 31 is guided by the guide rail 25 and moves up and down. Therefore, Z
The shaft motor 27 and the feed screw 26 serve as an elevating means for elevating the suction head 31.

A nut (not shown) provided on the back surface of the bracket 24 is screwed onto the horizontal feed screw 22.
Reference numeral 21 is a holding table for the feed screw 22. Therefore, when the X-axis motor 23 rotates forward and backward, the feed screw 22 rotates forward and backward, and the suction head 31 held by the bracket 24 horizontally moves between the positioning table 5 and the ball supply unit 10.

On the side of the ball supply unit 10 on the base 1,
The inspection unit 40 is provided. The inspection unit 40 includes the support base 4
1 is provided with a light-shielding type optical sensor 43 attached to a bracket 42 provided on the upper surface of the suction head 31. The balls 2 are excessively sucked on the lower surface of the suction head 31 and remain on the lower surface of the suction head 31 after mounting. The presence or absence of the ball 2 is detected by the optical sensor 43.

Next, an object detecting device using the optical sensor 43 will be described with reference to FIG. Here, an example in which the ball 2 held by the suction head 31 is detected as the detection target will be described. The optical sensor 43 includes a light projecting portion 43 attached to both ends of a bifurcated bracket 42.
a and a light receiving section 43b. The light projecting unit 43a projects light such as laser light for object detection along the optical axis a reaching the light receiving unit 43b.

The light receiving section 43b receives the light projected by the light projecting section 43a and outputs an electric signal corresponding to the amount of the received light. The output electronic signal is sent to the determination unit 44, and the determination unit 44 uses the output value of this electrical signal as the threshold storage unit 46.
Ball 2 by comparing with the threshold stored in
The presence or absence of is determined. Then, the determination result is transmitted to the control unit 47 of the conductive ball mounting device.

Ball presence / absence determination using this threshold value will be described with reference to FIG. FIG. 3A shows the output value (output voltage V) of the electric signal output from the light receiving section 43b and the light blocking degree α, that is, from the light projecting section 43a along the optical axis a according to the amount of light received by the light receiving section 43b. The projected light is the light receiving unit 4.
3 is a graph showing the relationship with the degree of being blocked by a detection target object before reaching 3b. As shown in the graph, between the light blocking degree α and the output voltage V, V = V1
There is a relationship of (1-α).

FIG. 3B shows three different light blocking states. In (a), the light blocking degree α = 0, that is, the light projecting unit 43
This shows a state in which there is no light-shielding object between a and the light receiving portion 43b, and the output voltage V1 in this case has a value indicating the reference state in the ball presence / absence determination, as will be described later.
On the other hand, (C) shows a state in which the light blocking degree α = 1, that is, the light from the light projecting portion 43a is completely blocked by the ball 2 on the way and is not received by the light receiving portion 43b at all.
In this case, the output voltage from the light receiving section 43b becomes zero.

Then, (b) is in an intermediate state between (a) and (c), that is, the light projecting portion 43 by the ball 2 to be detected.
The state where the light from a is blocked to some extent (light blocking degree α = α1) is shown. In the detection of the ball 2, there is a lower limit (α1) of the light blocking degree α, which can be judged as the presence of the ball 2. Therefore, this lower limit
An output voltage corresponding to 1 is set as a threshold value TH1 for presence / absence determination in ball detection. In the presence / absence determination of a ball, if the output voltage V is higher than this threshold value TH1, there is no ball, and if it is equal to or lower than the threshold value TH1. Judge that there is a ball.

In FIG. 2, the electric signal (output voltage V) from the light receiving portion 43b is transmitted not only to the judging portion 44 but also to the threshold value correcting portion 45. The function of the threshold correction unit 45 will be described with reference to FIG. FIG. 4A shows the relationship between the output value (output voltage V) of the electric signal and the light blocking degree α at the start of operation of the conductive ball mounting device (similar to the graph shown in FIG. 3A). The output voltage V1 is obtained in the state where the light blocking degree α = 0.

By the way, the light projecting portion 43a of the optical sensor 43,
The light emitting element and the light receiving element used in the light receiving section 43b have a characteristic that the sensitivity changes with temperature. For example, the amount of light emitted by the light emitting element changes with temperature, and the temperature changes even if the same amount of light enters. Then, the strength of the electric signal output from the light receiving element changes. Further, the bracket 42 to which the optical sensor 43 is attached also deforms due to the temperature change, and when the optical axis moves due to this deformation, the light receiving unit 43.
An error may occur in the amount of received light due to b.

At the time of continuous operation, the output voltage obtained at the light-shielding degree α = 0 is V1 at the time of starting the operation of the apparatus, as shown in FIG. From V1 to V2, which is smaller than V1. In this case, the graph showing the relationship between the output voltage V and the light blocking degree α changes from the straight line L1 to the straight line L2.

However, as described above, the output voltage V and the light blocking degree α are
If the initially set threshold value TH1 is used as it is in a state where the relationship between and is changed, the light blocking degree α2 corresponding to the threshold value TH1 on the straight line L2 is larger than the preset appropriate light blocking degree α1. Get smaller. Therefore, the shading degree α
The light-shielding state between 1 and α2, which should normally be judged as no ball, results in inappropriately judging that there is a ball by using the threshold value TH1.

In order to prevent such an inconvenience, in the ball detection shown in the present embodiment, the light receiving portion 43a in the state where the ball 2 does not exist on the optical axis a and the light blocking degree α = 0.
The threshold value TH is corrected by the threshold value correction unit 45 based on the output voltage V. That is, if the output voltage V decreases from V1 to V2, the threshold TH is corrected from TH1 to TH2 according to the decrease rate,
The corrected new threshold value TH2 is stored in the threshold value storage unit 46.
To memorize. This threshold value correction process is performed by a command from the control unit 47.

Then, the subsequent ball presence / absence determination is performed using a new threshold value TH2. Thereby, the light receiving unit 4
Regardless of the change in the light receiving state of 3b, the threshold value TH corresponding to the light blocking degree α1 that is appropriate for determining the presence or absence of the ball is set, and accurate ball detection can be performed.

Although the above description shows an example in which the ball 2 is detected as the detection target object, the suction head 31 is set by setting the lower end of the suction head 31 as the detection target object.
It is possible to detect whether or not the height position of the is equal to the predetermined height position. As shown in FIG. 5, the light projecting portion 43a
When the suction head 31 is gradually lowered between the light receiving section 43b and the light receiving section 43b, the suction head 31 moves the light from the light projecting section 43a to the optical axis a.
By blocking the light emitted along the line, the light blocking degree α changes similarly to the case shown in FIGS. 3 and 4.

(A) and (c) show the states of 0 and 1 respectively. In (b) between (a) and (c), the lower end surface of the suction head 31 is the optical axis. It shows a state in which it matches a. In this (C) state, the light from the light projecting portion 43a is blocked with the light blocking degree α = α1 ′. Therefore, the output voltage corresponding to the light-shielding degree α1 ′ is set to the threshold value TH for detection determination in the lower surface position detection of the suction head 31.
Set as 1 ', and in the head height detection,
By detecting that the output voltage V matches the threshold value TH1 ′, it can be determined that the lower surface of the suction head 31 matches the height of the optical axis a.

Therefore, by setting the optical axis a at a desired head height position, it is possible to detect whether or not the height position of the suction head 31 is proper. Also in this case, similarly to the example shown in FIG. 4, the light blocking degree α = 0.
Based on the output voltage V of the light receiving section 43a in the state of
By correcting the threshold value TH ′ by the threshold value correction unit 45, the light-shielding degree α1 ′ is always suitable for head height detection regardless of the change in the light-receiving state of the light-receiving unit 43b caused by the temperature change or the like. The threshold TH thus set is set, and accurate head height detection can be performed.

(Second Embodiment) FIG. 6 is a block diagram showing a ball detecting function of a conductive ball mounting apparatus according to a second embodiment of the present invention. In FIG. 6, the bracket 42 includes a light projecting portion 43 of the optical sensor 43 similar to that of the first embodiment.
a, the light receiving portion 43b is attached. Projector 43a
Is a light amount control unit 4 that controls the amount of light projected onto the light receiving unit 43b.
It is possible to increase or decrease by 9.

The electric signal output from the light receiving section 43b is sent to the judging section 44, and the presence / absence of the ball 2 is judged based on this electric signal as in the first embodiment. Similar to the example shown in FIG. 4, the output voltage V output from the light receiving unit 43b fluctuates during continuous operation, but in the second embodiment, the light blocking degree α = 0 where the ball 2 does not exist on the optical axis a. The output voltage in the state is received by the light amount level correction unit 48, and the light amount control unit 49 is controlled based on the output voltage V1 to correct the light amount level of the light projecting unit 43a.

That is, according to a command from the control unit 47,
The light amount level correction unit 48 controls the light amount control unit 49 to change the light amount level projected from the light projecting unit 43a according to the rate of decrease in the output voltage V from the light receiving unit 43b. As a result, regardless of temperature fluctuations due to the passage of operating time,
The light receiving section 43b always outputs a constant output voltage V1 in the state where the light blocking degree α = 0. Therefore, the presence / absence of a ball can be accurately determined without changing the preset threshold value TH1.

(Third Embodiment) FIG. 7 is a block diagram showing a ball detecting function of a conductive ball mounting apparatus according to a third embodiment of the present invention. In FIG. 7, a light emitting portion 43a and a light receiving portion 43b ′ of the optical sensor 43 are attached to the bracket 42. The light projecting section 43a is similar to that shown in the first embodiment, and irradiates the light receiving section 43b 'with light.

The light receiving portion 43b 'receives the projected light and outputs an electric signal (primary electric signal) having a magnitude corresponding to the amount of received light, and a primary electric signal from the light receiving element 43c. The output conversion unit 43d that outputs the output voltage (secondary electric signal) converted at the conversion level of is provided.
The conversion level of the output conversion unit 43d is the conversion level adjustment unit 5
The output voltage from the light receiving portion 43b 'can be set to a desired output value even when the amount of light received by the light receiving element 43c changes. At this time, the light receiving element 43 is included in the conversion level adjusting unit 50.
A primary electric signal indicating the amount of light received by c is sent, and the conversion level is changed according to the amount of received light. The output voltage converted by the output conversion unit 43d is the determination unit 44.
And the presence / absence of the ball 2 is determined as in the first embodiment.

Similar to the example shown in FIG. 4, during continuous operation, the amount of light received by the light receiving element 43c fluctuates, and the value of the output voltage also changes from V1 to V2. Third Embodiment
Then, the conversion level adjustment unit 50 changes the conversion level of the output conversion unit 43b so that the output voltage in the state where the light blocking degree α = 0 where the ball 2 does not exist on the optical axis a is always a predetermined value. That is, according to the change in the amount of light received by the light receiving element 43c due to the passage of operating time, the output conversion unit 43
The conversion level of d is changed.

As a result, regardless of the elapse of the operating time, the light receiving section 43b 'always outputs a constant output voltage V1 (predetermined value) in the state where the light blocking degree α = 0. Therefore, it is possible to perform appropriate ball presence / absence determination without changing the preset threshold value TH1.

[0039]

According to the present invention, the threshold value and the light emission of the light projecting unit are based on the output value of the light receiving unit in the state where the object to be detected does not exist on the optical axis connecting the light projecting unit and the light receiving unit. Since either the level or the output level of the output value conversion circuit that converts the amount of light received by the light receiving unit into an output value is corrected, it is possible to eliminate detection errors due to temperature changes and obtain correct detection results. it can.

[Brief description of drawings]

FIG. 1 is a front view of a conductive ball mounting device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a ball detection function of the conductive ball mounting apparatus according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of ball detection processing of the conductive ball mounting apparatus according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of ball detection processing of the conductive ball mounting apparatus according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of head height detection processing of the conductive ball mounting apparatus according to the first embodiment of the present invention.

FIG. 6 is a block diagram showing a ball detection function of a conductive ball mounting device according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a ball detection function of a conductive ball mounting device according to a third embodiment of the present invention.

[Explanation of symbols]

40 Inspection Department 43 Optical sensor 43a Projector 43b Light receiving part 43d output converter 44 Judgment unit 45 Threshold correction unit 46 threshold storage 47 Control unit 48 Light level correction unit 49 Light intensity controller 50 Conversion level adjuster

Claims (3)

[Claims] 1. An object detection device for detecting the presence or absence of an object to be detected by a light-shielding type optical sensor, comprising a light projecting section for projecting light along an optical axis, and a light projecting section for projecting light. A light receiving unit that receives light and outputs an electric signal corresponding to the received light amount, and a judging unit that judges the presence or absence of a detection target object by comparing the electric signal with a threshold value stored in a threshold value storage unit, An object detection apparatus, comprising: a threshold value correction unit that corrects the threshold value based on the electric signal in a state where no detection target object exists on the optical axis. 2. An object detection device for detecting the presence or absence of an object to be detected by a light-shielding type optical sensor, comprising a light projecting section for projecting light along an optical axis, and an amount of light projected by this light projecting section. A light amount control unit for controlling, a light receiving unit for receiving light from the light projecting unit and outputting an electric signal according to the received light amount, and comparing the electric signal with a threshold value stored in a threshold value storage unit. A determination unit that determines the presence or absence of a detection target object by controlling the light amount control unit based on the electric signal in the state where the detection target object does not exist on the optical axis, and corrects the light amount level of the light projecting unit. An object detection device, comprising: 3. An object detecting device for detecting the presence or absence of an object to be detected by a light-shielding type optical sensor, which comprises a light projecting section for projecting light along an optical axis, and a light projecting section for receiving light from the light projecting section. A light-receiving element including a light-receiving element that outputs a primary electric signal having a magnitude corresponding to the amount of received light and an output conversion section that converts the primary electric signal output from the light-receiving element into a secondary electron signal and outputs the secondary electron signal. A determination unit that determines the presence or absence of the detection target object by comparing the next electric signal with the threshold value stored in the threshold value storage unit, and the secondary electric power in a state where the detection target object does not exist on the optical axis. An object detection apparatus, comprising: a conversion level adjusting unit that changes a conversion level of the output converting unit so that a signal magnitude becomes a predetermined value.