JPH0450642A - Object surface condition inspection device - Google Patents

Abstract

PURPOSE:To make it possible to perform accurate inspection of the condition of a surface even if the surface of an object is inclined by selecting either of a first sensor for receiving the reflected light which is returned through a scanning optical system containing a mirror that is provided in the required direction in the vicinity of the surface of the object under inspection or a second sensor for receiving the reflected light which is returned on the same path as the emitting path. CONSTITUTION:A mirror 29 is provided in parallel with the scanning direction of a laser beam which scans a surface 50 of an object under inspection in the close proximity with the surface 50. A first sensor 35A receives the reflected light which is returned through a scanning optical system 31. The reflected light is one of the reflected light from the surface 50 and is further reflected from the mirror 29. A second sensor 35B receives the reflected light which is returned on the same path as the emitting path. The outputs of the sensors 35A and 35B are compared. Either of the sensor 35A or the sensor 35B, e.g. the darker sensor, is selected with a selecting means 47. As a result, the inspections for the design of the surface of the object, the wiring condition, the arranging state and the arranging direction of the mounted components such as resistors and capacitors, the position deviation, the chipping and the floating of elements and the like can be judged automatically, efficiently and accurately without contact.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an object surface condition inspection device, and in particular, an object of the present invention is to easily inspect the position and arrangement direction of parts placed on the surface of an object to be inspected. A light source, a scanning optical system that directs a laser beam from the laser light source to the surface of the object to be inspected and scans the surface in a fixed direction, a moving stage on which the object to be inspected is placed, and a scanning optical system that scans the surface of the object to be inspected. A mirror is provided approximately parallel to the scanning direction of the laser beam and close to the surface of the object to be inspected. Of the light reflected from the surface of the object to be inspected, the reflected light further reflected by the mirror is transmitted to the scanning optical system. a first sensor that receives reflected light that returns through the scanning system; out of the reflected light from the surface of the object to be inspected, the reflected light that returns via the scanning optical system along the same path as the irradiation path of the laser beam; The device is configured to include a second sensor that receives light and a selection device that compares the outputs of the first sensor and the second sensor and selects one of them as necessary.

(Prior Art) The present invention relates to an object surface condition inspection device, and more particularly to an object surface condition inspection device that can easily inspect the position and arrangement direction of components in a mounted object such as an electronic component. It is.

Inspection of the surface condition of an object, such as the design of the surface of the object to be inspected, the wiring condition, the placement of mounted components such as resistors, capacitors, transistors, and solder, their placement direction, misalignment, chipping and lifting of elements, etc. Various methods have been proposed for automatic, non-contact, efficient and accurate measurement and judgment, and one example is the light cutting method shown in Figure 7. It is being

In FIG. 7, a slit light is irradiated from directly above the object to be inspected 10, and the light cutting line is diagonally directed from a TV (television).
The camera 13 takes an image. In the case of the object shape shown in Fig. 7,
As shown in FIG. 8, the portion corresponding to the height portion is, for example,
It is monitored by the TV camera 13 as a brightness image. This image pattern is scanned in the horizontal direction (y direction) for each line (vertical direction) and the overall shape (height) is detected by trigonometry.

However, the above-mentioned optical cutting method has the disadvantage that x-y scanning takes time and the measurement speed is very slow. Even if the process of calculating the height from the detected image is performed in real time using hardware, it takes a small amount of time to measure the height of one line (
The reality is that both take about 1730 seconds (time for one frame). This measurement speed is not sufficient to meet the demands for faster processing.

In order to improve the drawbacks of the prior art, an inspection method as shown in FIG. 9 has been proposed.

That is, in the inspection apparatus shown in FIG. 9, a laser light source (for example,
The laser beam L2 from the semiconductor laser) 21 is converted into parallel light by the collimating lens 23 and irradiated almost perpendicularly onto the surface of the object to be inspected, and the laser beam is scanned in a fixed direction over the surface of the object to be inspected. Scanning optical system 3
1. To give a specific example of the scanning optical system 31, a laser beam is incident on a deflection mirror 25 made of a polygon mirror (rotating polygon mirror). The reflected light L4 by the polygon mirror 25 is reflected by the parabolic mirror 27 in a predetermined direction. As is well known, the parabolic mirror 27 also has the function of forming an image at its focal length.

Therefore, the stage 51 is movable within the orthogonal x-y plane.
The object to be inspected 50 placed above is placed at the focal length of the parabolic mirror 27 . In the example of FIG. 9, since the object to be inspected 50 is placed in a horizontal plane, the parabolic mirror 27 and the object to be inspected 50 are arranged in such a way that the scanning beam L can be vertically incident on it from above. A first mirror M is provided in between.

The mirror 29 placed near the object to be inspected 50 forms an inclination angle β that is substantially perpendicular to the object to be inspected. Further, the mirror 29 is arranged in the vicinity (at a distance d) of the irradiation beam L on the object to be inspected 50.

As a result, the mirror 29 allows the forward path (irradiation beam Ls) to be
A type of retroreflection system is formed that is approximately parallel to the path and close to the outgoing path. The mirror 50 detects scattered light reflected by the object 50 to be inspected. That is, the mirror 29 is viewed from an oblique direction.
The light reflected towards is reflected by this mirror,
A return path close to and substantially parallel to the outbound path, that is, via the first mirror MI, the parabolic mirror 27, and the polygon mirror 25, the second mirror M2, the third mirror M, and the converging lens 33 to the photodetector 35. It is forced to converge. A photodetector 35 is placed at the focal length of the converging lens 33.

As a result, the reflected light (signal light) from the object to be inspected 50 is reimaged on the photodetector 35 as a beam spot.

Since the optical system shown in FIG. 9 is a re-imaging system as described above,
Even though the beam is scanned, the reflected light can be focused on one location (photodetector 35). At this time, mirror 2
9 forms a predetermined inclination angle β with respect to the object to be inspected 50, so the position of the imaging beam spot P on the photodetector 35 changes depending on the height of the object to be inspected 50. That is, photodetector 3
By measuring the position of the beam spot P 5, the height distribution of the surface 50 of the object to be inspected can be detected.

As the photodetector 35, for example, a light spot position detection element PSD (Position 5ensi) which is known per se is used.
tiveDetector) (for example, commercially available from Hamamatsu Photonics). This is a -type photodiode and typically has two output terminals, each with an output current of I.

(2), the position of the light (corresponding to the height information of the object to be detected 50) and the intensity (corresponding to the shading information of the object to be detected 50) are expressed by the following equation.

Light intensity = 1t+Ib (2)
Therefore, the position and intensity of the light spot can be detected from the output signal. The response time (detection time) is extremely short, about 500 nsec. Therefore, even if the processing time in the signal processing circuit 45 is included, one light spot can be measured in 1 μsec or less.

Incidentally, as described above, since the PSD can simultaneously detect the light intensity, it is also possible to measure the shading information of the object to be measured.

In such an inspection device, compared to the conventional example described above, the height and brightness of the inspection object can be measured simultaneously, and the information can be inputted into an image to determine defects. It has the following drawbacks.

That is, if something such as a tantalum capacitor is mounted on the surface of the object to be inspected, the capacitor 100 is fixed to a substrate 103 with solder or the like as shown in FIG. Therefore, in order to clarify the polarity, a notch 101 is usually provided in a part of the main body 100, or a mark 102 having a color such as white, yellow, or red is provided on the upper surface of the main body 100. .

Further, since the capacitor 100 is usually black or dark brown, depending on its constituent material, the mark can be easily identified.

Therefore, when an inspection is performed using the apparatus shown in FIG. 9, since the light reflected from the mark section 102 and the light reflected from the main body section 100 have different brightnesses, the two can be easily distinguished on the arithmetic circuit. In other words, there is no problem if the capacitor 100 is correctly installed perpendicular to the board as shown in Figure 10, but in many cases the capacitor is installed at an angle as shown in Figure 11, and in reality It is determined that the inclination is up to ±20 degrees to be suitable as a mounted component.

In such a case, if the inspection is carried out using the apparatus shown in FIG. When the beam light reflection angle is in a regular reflection relationship, depending on the material of the main body of the capacitor 100, if the material is made of a glossy material, the reflected beam light from the main body becomes The mark portion 102 also becomes brighter, making it difficult to distinguish between the background and the mark portion 102.
The drawback was that it became impossible to recognize the existence of 2.

Therefore, it has been impossible to accurately detect the arrangement direction of the mounted components, especially the polarity direction of the capacitor.

[Problems to be Solved by the Invention] The purpose of the present invention is to improve the drawbacks of the above-mentioned conventional techniques, and improve the surface condition of an object, such as the design of the surface of an object to be inspected.
Automatic, non-contact, efficient and non-contact inspection of wiring conditions, placement of mounted components such as resistors, capacitors, transistors, solders, etc., their placement direction, misalignment, chipped or lifted elements, etc. To provide an object surface condition inspection device which is a method for accurate measurement and judgment, and which can accurately execute the above inspection even when the surface of the object to be inspected or the mounted component itself is inclined. It is something to do.

(Means for Solving the Problems) In order to achieve the above object, the present invention employs the following technical configuration.

That is, a laser light source 21, a scanning optical system 31 that directs a laser beam from the laser light source to the surface of the object to be inspected and scans the surface in a fixed direction, a moving stage 51 on which the object to be inspected is placed, and A mirror 29 is provided approximately parallel to the scanning direction of the laser beam that scans the surface of the object to be inspected and close to the surface of the object to be inspected; A first receiving the reflected light that returns through the scanning optical system 31.
a second sensor 35B that receives reflected light from the surface of the object to be inspected that returns via the scanning optical system 31 along the same path as the irradiation path of the laser beam; The object surface condition inspection device 1 has a selection means 47 that compares the outputs of the first sensor and the second sensor and selects one of them as necessary.

In the present invention, the scanning optical system may have the same configuration as the scanning optical system in the conventional example shown in FIG.

A specific example of the object surface condition inspection device according to the present invention is as shown in FIG. ), a second sensor 35B is provided that receives the reflected light that returns along the same path as the incident irradiation path of the laser beam, and the outputs of the first sensor and the second sensor are compared. A selection means 47 is provided to select one of them as required.

Furthermore, in the present invention, one of the signals output from the first and second sensors further includes information regarding the height of the surface of the object to be inspected. The specific position and direction of the surface of the object to be inspected, the state of the surface, etc. can be easily and accurately inspected.

[For production]

In the present invention, as a result of adopting the above-mentioned technical configuration, the design of the surface of the object to be inspected, the wiring state, the arrangement of mounted components such as resistors, capacitors, transistors, solders, etc., the arrangement direction, and the arrangement position thereof can be improved. It has become possible to obtain an object surface condition inspection device that can automatically and non-contactly, efficiently and accurately measure and judge inspections for deviations, chipping and lifting of elements, etc.

〔Example〕

A specific example of the object surface condition inspection apparatus according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an integrated example of the object surface condition inspection device according to the present invention, and the same members as those used in the conventional example shown in FIG. 9 are given the same reference numerals to indicate their functions. Explanation regarding the configuration will be omitted.

As described above, the characteristic part of the present invention is that the input path of the laser beam L3 irradiated onto the surface of the object to be inspected is L3→L4→
A second sensor 35B is provided to detect the reflected light returning through the same path as L, and if the surface of the object to be inspected or the surface of the mounted component 100 is perpendicular to the input laser beam. , the front surface of the object to be inspected will be inspected from directly above, and if the surface of the object to be inspected or the surface of the mounted component 1000 is tilted, a part of the laser beam diffusely reflected from the surface will be It returns along the same route and is input to the second sensor 35B.

Note that the first sensor 35B normally receives reflected light from the mirror 29, and the reflected light contains information related to the brightness of the surface of the object to be inspected and the surface of the object to be inspected itself or the mounted components. The fact that information regarding height is included is the same as explained in the conventional example.

That is, in the present invention, the first sensor and the second sensor always work together as a pair to inspect the surface of the object to be inspected.

To describe the object surface condition inspection apparatus according to the present invention more specifically, in FIG. A second lens 40 (
The first lens is 33) and the second optical sensor (PSD)
35B (the aforementioned optical sensor-35A is shown as the first optical sensor). That is, the object to be inspected 5
The reflected light reflected at 0 travels backwards, following exactly the same optical path as the forward path of the beam, and enters the polarizing beam splitter 38. It is preferable that a λ/4 plate 36 is provided in front of the polarizing beam splitter 38 (on the opposite side from the light source 21). This is preferably provided in order to prevent the polarized light from entering the laser since the polarized light is preserved and returned when the mirror surface is used.

The polarizing beam splitter 38 allows, for example, P polarized light to pass through, and S polarized light to pass through.
Polarized light is reflected, so if the outgoing beam (linearly polarized light) is P-polarized, on the return journey, the extra diffused light is converted to S-polarized light by the λ/4 plate 36, so it is converted to S-polarized light by the beam splitter 38. It is reflected and enters the second PSD 35B via the second lens 40. In this way, excess diffused light can be taken out to the second PSD 35B.

Note that this is no different from a normal re-imaging system, so even if the height of the object to be measured changes, the position of the light spot does not change.

In order to remove noise light, a pinhole is provided in front of the second PSD 35B.

Therefore, in the present invention, considering the case where the tantalum capacitor 100 is correctly installed vertically as shown in FIG.
The second sensor 35B receives bright reflected light, and the first sensor 35A receives reflected light that is darker than the reflected light received by the second sensor 35B.

Also, when scanning the main body portion 100, the second sensor 35B receives bright reflected light, and the first sensor 35A receives reflected light that is darker than the reflected light received by the second sensor 35B. However, the level is mark part 102
Naturally, it is smaller than the portion of .

Next, as shown in FIG. 11, the tantalum capacitor 100 is installed tilted at a certain angle, and that angle is the angle of incidence of the laser beam on the surface of the object to be inspected and the reflection of the beam light on the mirror 29. Considering the case where there is a regular reflection relationship with the corner, when scanning the mark portion 102, the first sensor 35A receives the bright reflected light, and the second sensor 35B receives the bright reflected light from the first sensor 35A. Receives reflected light that is darker than the reflected light it receives.

Also, when scanning the main body portion 100, the first sensor 35A receives bright reflected light, and the second sensor 35B receives reflected light that is darker than the reflected light received by the first sensor 35A. However, in such a case, since the reflected light from the main body portion 100 is also strong, the mark portion 10
2 or the main body portion 10 becomes difficult. However, the level of light received by the second sensor 35B is naturally higher for the light reflected from the mark portion 102 than for the light reflected from the main body portion 100.

Therefore, in the present invention, the first sensor 35A constantly compares the information related to brightness outputted from the second sensor 35B, for example, the output voltage, and selectively adopts one of the information, which will be described later. I am trying to do some image processing.

In the present invention, for example, the first sensor 35A may always select the darker information among the brightness-related information output from the second sensor 35B to perform calculation processing. good.

The criteria for such selection can be determined as appropriate depending on the purpose of processing, and in some cases, brighter information may be selectively adopted for processing.

As an example of the selection means, as shown in FIG.
The sensor 35A inputs information related to brightness outputted from the second sensor 35B, such as the output voltage, to the comparison and selection circuit 47 via appropriate amplification means or inverter means 45, 46, and outputs either one of them. It may be something that has been made into

FIG. 2 is a diagram showing a specific example of such selection means 47.

That is, the first sensor 35A is the second sensor 35B.
The output from the comparator 60 is inputted to each input terminal of the comparator 60, and a part of the output of the comparator 60 is inputted to the analog switch 62.
The other part is connected to one switch 63 of the analog switch 62 via an inverter 61, and the other part is connected to the other switch 64 of the analog switch 62.

When selecting the output of the sensor whose reflected light level is lower in the circuit, the comparator 60
The configuration may be such that the signal with the lower output voltage is selected by adjusting as appropriate.

The reverse is also possible.

In the present invention, as described above, the first sensor 35
The reflected light input to A contains information regarding the height of the surface of the object to be inspected based on trigonometry.
By measuring the voltage that changes depending on the position of the spot forming the focal point on the first sensor 35A, it is possible to immediately detect the height. Therefore, in the present invention, it is also preferable to perform the inspection by simultaneously utilizing the information regarding the height.

Note that it is clear from the configuration that the output information of the second sensor 35B does not include information regarding the height.

In the present invention, information regarding the height can be effectively used to confirm a specific position on the surface of the object to be inspected or the arrangement position of the mounted component.

Therefore, the information regarding the height is arithmetic-processed and image-processed independently of the above-mentioned selection means.

FIG. 3 shows a schematic block diagram of the signal processing process of the present invention.

That is, information S regarding the brightness from the first sensor 35A and information S regarding the brightness from the second sensor 35B.
2 to the selection means 47 to selectively output one of them, and input the output to the image processing means 66 to identify the mark part and the main body part, and display the result as an image on the display device. This is what is displayed. In order to match the output level of the second sensor 35B with the output level of the first sensor 35A, it is preferable to input the signal to the selection means 47 via a sensitivity adjustment amplifier 65 as appropriate, for example.

On the other hand, the information H regarding the height from the first sensor 35A is directly input to the line image processing means 66 to display the position of a specific portion on the surface of the object to be inspected or the arrangement position of the mounted component.

To describe an example of the method for carrying out the inspection process according to the present invention, if the resolution is 125 μm when inspecting the arrangement position and arrangement direction of mounted components on a 250++n x 300sv+ board, 12 megabytes of memory will be required. is prepared, and after scanning the entire surface of the substrate with a laser beam and storing all of the above information in the memory, image processing to be described later is executed to inspect the surface of the object to be inspected.

That is, as shown in FIG. 4, after the image input is completed (step a), the height information is first retrieved from the stored information and processed. (Step C). At this time, it is also preferable to compare with preset information regarding the position of each mounted component to determine whether each component is accurately placed.

Next, in the present invention, it is determined whether the arrangement direction of each mounted component is accurate or not, and an inspection window is set on software on each component (step d). ). The inspection window varies depending on the size of the mounted component to be inspected, as shown in FIG. And windows 70 and 71 smaller than that size
and

Here, the window 70 is provided at a position corresponding to the mark portion described above, and the window 71 is provided at a position corresponding to the main body portion other than the mark portion.

Therefore, the information regarding brightness is read out from the memory, the information regarding the brightness in each window is binarized, and the number of pixels is counted (step e).

Now, suppose that the number of pixels of level 1, which is bright in the window 70, is the majority, and the number of pixels of level O, which is dark in the meaning 71, is the majority, and based on the preset information, If it is defined that the tantalum capacitor at that position is installed in the correct direction if it is bright in the window 70 and dark in the meaning 71 at that position, then compare these definitions. It is determined that the capacitor in this position is correctly installed (step f).

These steps are repeated to inspect the entire substrate, and if the inspection is not completed, the process returns to step b and the above steps are repeated (step g).

When the inspection of the entire board is completed, the process ends.

The outline of the system configuration of the object surface condition inspection apparatus according to the present invention is shown in FIG.

Although one specific example of the present invention is shown above, the present invention is not limited to this, and instead of simply selecting a dark level or a bright level, for example, a method of conditionally selecting the level may also be considered. It will be done.

That is, the darker one may be selected only when the darker one is equal to or greater than a specific value, and the brighter one may be selected otherwise.

In such a method, shadows of parts and the like are not selected, so a more desirable effect can be obtained.

On the other hand, instead of selecting one of the levels in advance using hardware as described above, it is also possible to adopt a method of processing using software.

〔effect〕

Since the present invention adopts the above-mentioned configuration, the drawbacks of the conventional technology are completely eliminated, and the design of the surface of the object to be inspected, the wiring condition, and the arrangement of mounted components such as resistors, capacitors, transistors, and solder can be improved. To obtain an object surface condition inspection device that can automatically, non-contact, efficiently and accurately measure and judge the situation or the arrangement direction thereof, deviation of the arrangement position, chipping or lifting of elements, etc. things became possible.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the principle of an object surface condition inspection apparatus according to the present invention, and is a diagram showing a specific example of the present invention. FIG. 2 is a diagram showing a signal selection means according to the present invention. FIG. 3 is a block diagram showing an example of a signal processing circuit according to the present invention. FIG. 4 is a flowchart showing the procedure of the inspection method according to the present invention. FIG. 5 is a diagram showing an example of a window used for inspection processing in the present invention. FIG. 6 is a system configuration diagram of an object surface condition inspection apparatus according to the present invention. FIG. 7 is a diagram showing an example of a conventional object surface condition inspection device. FIG. 8 is a diagram showing an example of a monitor image obtained by the method of FIG. 7. FIG. 9 is a diagram showing another example of the conventional object surface condition inspection device. FIGS. 10 and 11 are diagrams showing examples of mounting shapes of tantalum capacitors. 21... Laser light source, 23... Collimating lens, 25... Deflection mirror, polygon mirror 27... Parabolic mirror, 29... Mirror, 31... Scanning optical system, 33.40. ...Lens, 35A...First sensor 35B...Second sensor 36...1/4 wavelength plate, 38...Polarizing lens splitter 44...Mask, 44a...Beam spot, 45.46...Amplifier, inverter, 47...Selection means, 60...Comparator, 61...Inverter, 62...Analog switch, 63.64...Switch, 65...Sensitivity adjustment Amplifier, 66... Image processing means, 70.71... Processing window, 100... Tantalum capacitor body part, 101...
・The cutout is the part, 102... mark part. FIG. 2 shows an example of the signal selection means used in the invention. FIG. 3 shows an example of the signal processing circuit in the invention. FIG. 3 shows an example of the procedure of the inspection method in the invention. The same figure shows an example of a processing window used in the inspection of the present invention. The same figure shows the system configuration of the inspection device in the present invention.

Claims (1)

[Claims] 1. A laser light source, a scanning optical system that directs a laser beam from the laser light source toward the surface of an object to be inspected and scans the surface in a fixed direction, and movement for placing the object to be inspected. A stage, a mirror provided approximately parallel to the scanning direction of the laser beam scanning the surface of the object to be inspected and close to the surface of the object to be inspected, of the reflected light from the surface of the object to be inspected. A first sensor that receives the reflected light that is further reflected back through the scanning optical system, and irradiation of the laser beam through the scanning optical system among the reflected light from the surface of the object to be inspected. a second sensor that receives the reflected light that returns along the same route as the route; and a selection unit that compares the outputs of the first sensor and the second sensor and selects one of them as necessary. An object surface condition inspection device characterized by comprising: 2. The object surface state inspection device according to claim 1, wherein the signals output from the first and second sensors include information regarding the brightness of the surface of the object to be inspected. 3. The object surface state according to claim 2, wherein one of the signals output from the first and second sensors further includes information regarding the height of the surface of the object to be inspected. Inspection equipment. 4. The object surface according to claim 3, further comprising arithmetic processing means for processing the information regarding the height without going through the selection means, and also processing the information regarding the brightness from the selection means. Condition inspection device. 5. The object surface condition inspection apparatus according to claim 4, wherein the arithmetic processing means includes means for detecting the position and arrangement direction of a specific portion placed on the surface of the object to be inspected.