JPH06221822A - Inspecting apparatus of packaged printed circuit board - Google Patents

Abstract

PURPOSE:To improve the inspecting precision of a device sensing a light reflected vertically from a packaged printed circuit board along a minute beam light, in particular, regarding an inspecting apparatus wherein the minute beam light is made to scan vertically on the board, the reflected light therefrom is sensed from a plurality of directions and a packaged state is inspected. CONSTITUTION:A minute beam light emitted from a light source 1 is made to scan on a packaged printed circuit board 6 through the intermediary of a polygon mirror 3 and a projecting ftheta lens 5. A light reflected in the vertical direction from the board is led to a photodiode 26 through the projecting ftheta lens 5, the polygon mirror 3, a tunnel mirror 23, a lens 24 and a diaphragm 25. By using a divided type photodiode so divided as to generate electric outputs discrete from each other as the photodiode, the direction of slant of a soldered face is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounted printed circuit board inspection device, which irradiates a mounted printed circuit board with a fine beam of light and detects the reflected light to displace the mounted parts. The purpose is to inspect for missing items, defective solder, etc.

[0002]

2. Description of the Related Art In recent years, a non-contact method using the principle of triangulation has been used for inspecting displacement of parts of mounted printed circuit boards, defective parts, solder defects, etc.
Scan the printed circuit board while irradiating a narrowed beam light vertically onto the mounted printed circuit board, and receive the diffused reflected light from the irradiation position of the minute beam light by the photoelectric conversion element to inspect the surface shape of the circuit board. Is being done.

[0003]

In the conventional mounting printed circuit board inspection apparatus described above, of the reflected light diffused from the irradiation position of the minute beam light, it is reflected in the optical axis direction (substantially vertical direction) of the minute beam light. The reflected light is also led to the photoelectric conversion element to be used as brightness data for detecting the sticking of solder. The present invention provides an inspection apparatus that uses reflected light in such a vertical direction to further improve the detection accuracy, acquire the three-dimensional shape of the mounted printed circuit board to be inspected, and inspect it. To aim.

[0004]

In order to achieve this object, the mounted printed circuit board inspecting apparatus of the present invention includes a reflected light diffused from an irradiation position of a beam light vertically irradiated onto the mounted printed circuit board. A photoelectric conversion unit that receives reflected light in a vertical direction along the irradiation optical axis of the light beam and converts the reflected light into an electric output according to the amount of received light, and the photoelectric conversion units have mutually independent electric outputs. It is characterized by using a photodiode divided as described above.

[0005]

According to the above structure, among the reflected light diffused from the beam light irradiation position, the reflected light reflected in the vertical direction along the irradiation optical axis of the beam light is a photoelectric conversion element for electrically outputting each independently. By receiving the light and comparing the outputs, the tilt direction and tilt angle of the solder surface can be detected.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. An apparatus for inspecting a mounted printed circuit board to which the present invention is applied is shown in FIG. In FIG. 1, reference numeral 1 is a light source for generating a minute beam of light with which the mounted printed circuit board 6 is irradiated. Reference numeral 2 is a collimating lens system for converging the minute light beam from the light source 1 into a parallel light beam. 3 deflects the parallel light flux, and
It is a polygon mirror for deflecting the reflected light from the mounted printed circuit board 6. A polygon motor 4 drives the polygon mirror 3 to rotate. Reference numeral 5 denotes a light projecting fθ lens that collects the parallel light beam deflected by the polygon mirror 3 and irradiates the mounted printed circuit board 6 substantially vertically. Reference numeral 6 is a mounted printed circuit board to be inspected.

Reference numerals 7, 8, 9, and 10 receive reflected light from the minute beam light irradiation position on the mounted printed circuit board 6 from four directions, and receive the reflected light, respectively.
It is an optical path correction optical system that corrects the optical path of the reflected light in order to lead to 12, 13, and 14. Light receiving fθ lens 11, 12,
Reference numerals 13 and 14 are for guiding the reflected light that has passed through the optical path correction optical systems 7, 8, 9, and 10 to the polygon mirror 3. 15, 16, 17 and 18 are the light receiving fθ lens 11 and
It is a PSD (semiconductor position detecting element) lens for collecting the reflected light that has passed through 12, 13, and 14 and is deflected by the polygon mirror 3. 19, 20, 21, 22 are PS
It is a PSD that receives the reflected light condensed by the D lenses 15, 16, 17, and 18 and generates an electrical output according to the light receiving position.

Reference numeral 23 denotes the mounted print which has returned from the reflected light from the minute beam light irradiation position on the mounted printed circuit board 6 along the light projection optical axis through the light projecting fθ lens 5 and the polygon mirror 3. It is a tunnel mirror that deflects reflected light in a direction perpendicular to the substrate 6. Reference numeral 24 is a lens for collecting the reflected light deflected by the tunnel mirror 23. Reference numeral 25 is a diaphragm that blocks reflected light from directions other than the vertical direction. A photodiode 26 receives the reflected light in the vertical direction and converts the received light amount into an electrical output.

Reference numeral 27 is a table for fixing the mounted printed circuit board 6. A ball screw 28 moves the table 27 in the sub-scanning direction (arrow y direction) by rotating. A ball screw motor 29 rotates the ball screw 28. Reference numeral 30 is a guide rail for guiding the table 27. The operation of the mounted printed circuit board inspection device configured as described above will be described.

The minute light beam emitted from the light source 1 becomes a parallel light beam by the collimating lens system 2, passes through the holed portion of the tunnel mirror 23, is deflected by the polygon mirror 3, and is condensed by the light projecting fθ lens 5. The light beam is emitted substantially vertically on the mounted printed circuit board 6 as an optical axis. At this time, the minute light beam generated from the light source 1 scans the mounted printed circuit board 6 in the main scanning direction (arrow x direction) in the figure as the polygon mirror 3 rotated by the polygon motor 4 rotates. . And
The reflected light diffused from the scanning position on the mounted printed circuit board 6 is guided to the light receiving fθ lenses 11, 12, 13, and 14 by the optical path correction optical systems 7, 8, 9, and 10.

The optical path correcting optical systems 7, 8, 9 and 10 of the reflected light diffused from the irradiation position on the mounted printed circuit board 6 regardless of the change of the scanning position of the minute beam light,
A scanning direction when the angle formed by the minute beam light irradiation optical axis and the reflected light optical axis (hereinafter, tilt angle) is substantially constant, and the reflected light axis is projected on a plane perpendicular to the minute beam light irradiation optical axis. The reflected light whose angle (hereinafter, allocation angle) is substantially constant,
That is, the reflected light whose direction vector is substantially constant is received. Then, regardless of the change in the scanning position, the light is incident on the light receiving fθ lenses 11, 12, 13, and 14 at substantially the same position as the minute beam light irradiation optical axis with respect to the position in the main scanning direction (arrow x direction), Further, even if the scanning position changes, the reflected light reception f
The reflected light is guided so that the incident position of the θ lens in the sub-scanning direction (direction of arrow y) does not change.

Since the light receiving fθ lens 13 has the same shape as the light projecting fθ lens 5, the reflected light is guided to the polygon mirror 3 along the same route as the minute beam light of the light projected. Then, an image of the reflected light is formed at a position on the PSD 21 which is deflected by the polygon mirror 3 and which corresponds to the height of the irradiation position of the minute beam light on the printed circuit board 6 regardless of the change of the scanning position of the minute beam light. To be imaged. Other optical path correction optical system 7,
The same applies to 8, 10 and the optical path correction optical system 7,
The reflected light received by the light receiving elements 8 and 10 is the light receiving fθ lens 11 and 1
2, 14 and PSD lenses 15, 16, and 18, and are led to PSDs 19, 20, and 22.

In this way, the reflected light from the mounted printed circuit board 6 is PSD depending on the height of the irradiation position of the minute beam light.
Since the image is formed at the upper position, PSD19, 2 at this time
The height of the minute beam light irradiation position is obtained using the electrical outputs from 0, 21, and 22. Data such as selection to be described later is applied to the data measured by the PSDs 19, 20, 21, and 22 arranged in these four directions, and the correct height is measured regardless of the surface state of the measurement target. You can

Reflected light reflected from the irradiation position of the minute beam light in the direction of the optical axis of the minute beam light irradiation (substantially vertical direction) passes through the projection fθ lens 5, the polygon mirror 3, the tunnel mirror 23, the lens 24, and the diaphragm 25. It is led to the photodiode 26 via the. At this time, the reflected light in the vertical direction is
The light is projected by the fθ lens 5 and the lens 24, and the collected reflected light is received by the photodiode 26. A stop 25 provided between the lens 24 and the photodiode 26 blocks light other than the reflected light in the optical axis direction of the minute beam light irradiation. Therefore, only the light amount of the reflected light reflected from the irradiation position of the minute beam light in the optical axis direction of the minute beam light irradiation can be accurately measured.

Thus, the four PSDs 19, 20, 2
With 1 and 22, four brightness data and height data can be acquired for one measurement point from four directions. As a method of selecting four luminance data, there is a method of obtaining the maximum value of the four data. The height data can be selected and processed by, for example, removing the data for which the measurement accuracy cannot be guaranteed and then averaging the remaining data, or if there are many remaining data, the maximum level data and the minimum level data are used. There is a method of removing and averaging the remaining data.

Further, since the photodiode 26 receives the light reflected in the vertical direction from the mounted printed circuit board 6, the light reflected in the vertical direction is reflected when the inclination of the solder surface is gentle or when no solder is attached. Since the output becomes large, the output becomes large. On the contrary, when the inclination of the solder surface is steep, the reflected light in the vertical direction becomes small and the output becomes small. For this reason,
When the PSD output is too small to measure the height of the solder surface correctly, the brightness information of the photodiode 26 can be referred to.

Then, the selected height and brightness information is compared with the height and brightness information obtained and stored in advance as a reference from the mounted printed circuit board to determine the mounted state of the mounted printed circuit board. The quality can be inspected.

In the mounted printed circuit board inspection apparatus having the above structure, the role of the photodiode 26 is to detect whether the solder surface is an inclined surface or a flat surface from the amount of received light. However, even if the single photodiode 26 can determine the slope and the plane of the solder surface, it cannot determine which slope the slope is. Therefore, in the mounting board inspection apparatus of the present embodiment, a four-division photodiode is used as the photodiode 26. Since the output of the portion in the direction in which the solder surface is inclined is the largest of the four divided portions using the 4-division photodiode, the inclination direction of the solder surface can be determined.

A detailed description will be given below with reference to FIG. FIG. 2 is an explanatory diagram of a configuration using a 4-division photodiode.
Reference numeral 37 is a four-divided photodiode, 38 is a solder surface of a printed circuit board on which mounting is completed, and 39 is a lead tip. For simplicity, the light projecting fθ lens, polygon mirror, tunnel mirror, lens, and diaphragm are omitted. The principal ray of the reflected light is represented by a solid line with an arrow, and the ambient light is represented by a broken line.
The four-divided photodiode 37 receives the peripheral light represented by the broken line, but when the solder surface is inclined, the principal ray of the reflected light does not face the direction of the minute beam light irradiation optical axis A, and the So that it tilts in the direction in which the solder surface is tilted. Further, since the amount of the peripheral light decreases as the distance from the principal ray increases, the four-division photodiode that receives the peripheral light has the maximum received light amount in the divided portion in the direction in which the solder surface is inclined. In FIG. 2, the amount of light received by the division unit 3 is maximum. That is, the direction in which the solder surface is tilted can be known by detecting the amount of received light of the divided portions 1 to 4 and examining the divided portion having the maximum light amount. In addition, the tilt angle of the solder surface can be obtained by performing an operation on the amount of received light of each of the division units 1 to 4.

An example of a 4-division photodiode has been described above, but a photodiode having a division number of 4 or more may be used, or a plurality of single photodiodes may be arranged to detect the amount of received light. It doesn't matter. Further, the position of the principal ray of the reflected light may be obtained by using a two-dimensional PSD instead of the photodiode.

In the mounting printed circuit board inspection apparatus shown in FIG. 1, the amount of reflected light in the sub-scanning direction perpendicular to the mounted printed circuit board is in the sub-scanning direction of the projection fθ lens 5. If the length of the light projecting fθ lens in the sub-scanning direction is too small because of the width, the amount of light received by the photodiode is reduced and the inspection accuracy is reduced.

Therefore, as shown in FIG. 3, a special cylindrical lens 40 is arranged in order to increase the received light amount of the reflected light in the vertical direction. In the figure, the reflected light in the direction perpendicular to the mounted printed circuit board is shown by the solid line, and the minute light beam of the projected light is shown by the dotted line. The special cylindrical lens 40 is a lens having a curvature only in the sub-scanning direction, and has a shape in which a part of the apex of the R surface is cut to form a flat surface. By placing the special cylindrical lens, it is possible to collect the reflected light in the sub-scanning direction in the vertical direction with respect to the mounted printed circuit board, and improve the inspection accuracy of the photodiode 26.

At this time, the minute beam light after passing through the projection fθ lens 5 is applied to the mounted printed circuit board 6 through the special cylindrical lens 40, but since it passes through the flat surface portion of the special cylindrical lens 40, the special cylindrical lens 40 Mounted printed circuit board 6 without being affected by 40
Is irradiated. Further, since the reflected light in the direction perpendicular to the mounted printed circuit board 6 passes through the R surface portion of the special cylindrical lens 40, the light in the sub-scanning direction is condensed,
The amount of light that guarantees the inspection accuracy of the photodiode can be secured.

[0024]

As described above, according to the present invention, of the reflected light of the minute beam light vertically radiated to the mounted printed circuit board, the reflected light in the substantially vertical direction along the optical axis of the minute beam is received. In a device for inspecting a mounted printed circuit board that inspects the surface shape, the divided photoelectric conversion elements that output electrical signals different from each other are used to receive the reflected light in the vertical direction, thereby changing the inclination direction of the solder surface. The inspection accuracy can be improved by increasing the amount of received light by using a cylindrical lens that is processed so as not to affect detection or scanning of the substrate with minute beam light.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an inspection device for a mounted printed circuit board to which the present invention is applied.

FIG. 2 is an explanatory view of a main part of an inspection device for a mounted printed circuit board according to an embodiment of the present invention.

FIG. 3 is an explanatory view of main parts of the device.

[Explanation of symbols]

 1 Light Source 2 Collimator Lens System 3 Polygon Mirror 4 Polygon Motor 5 Projection fθ Lens 6 Mounted Printed Circuit Board 7, 8, 9, 10 Optical Path Correction Optical System 11, 12, 13, 14 Light Receiving fθ Lens 15, 16, 17, 18 Lens for PSD 19, 20, 21, 22 PSD 23 Tunnel mirror 24 Lens 25 Aperture 26 Photodiode 37 37 4-division photodiode 40 Special cylindrical lens

Front page continued (72) Inventor Yuji Ono 2-10, Shoucho, Takamatsu-shi, Kagawa Matsushita Electronics Co., Ltd. (72) Hidenori Nagata 2-2-10, Shoucho, Takamatsu, Kagawa Matsushita Kotobuki Electronics Industry Co., Ltd.

Claims (2)

[Claims] 1. An amount of received light that receives reflected light in a vertical direction along an irradiation optical axis of the beam light among reflected light diffused from an irradiation position of the beam light vertically irradiated on the mounted printed circuit board. A photoelectric conversion means for converting into an electrical output according to the above, and a photodiode which is divided so as to provide an independent electrical output to the photoelectric conversion means is used. 2. A reflected light in a vertical direction along an irradiation optical axis of the light beam, of reflected light diffused from an irradiation position of the light beam scanned while vertically irradiating the mounted printed circuit board. Is provided with a photoelectric conversion means for converting into an electrical output according to the amount of received light, using a cylindrical lens having a plane through which the light beam for scanning on the substrate is used, and the reflected light reflected in the vertical direction is A device for inspecting a printed circuit board that has been mounted, characterized in that it collects light.