JPH1123485A - Method and apparatus for inspecting substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a size of an object to be measured with the use of an inexpensive means by enhancing a resolution and make a substrate-inspecting apparatus itself compact. SOLUTION: A luminous flux generated from a laser light source 1 is enlarged by a cylindrical lens and then turned to a plane parallel luminous flux by a plano-convex lens 2. The plane parallel luminous flux is reflected by a mirror 3 and projected to a solder 5 with a fixed angle θ. As a result, bright- lines linearly appear on a substrate 6 including on the solder 5, and a break of the bright-lines is brought about due to a height of the solder 5. The bright- lines are picked up by a one-dimensional sensor 4 arranged above the substrate 6 along the linear bright-lines. A state of the picked-up bright-lines is formed into an image by an image-analyzing means, and a size of the solder 5 is operated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an apparatus for inspecting the state of solder application on a printed circuit board.

[0002]

2. Description of the Related Art At present, printing accuracy of cream solder on a printed circuit board is improved, and cream solder is printed at a finer pitch. If the height and thus volume of the cream solder are accurately measured and controlled, the yield of component mounting on a printed circuit board can be improved.

As a method for inspecting the state of the solder applied to the printed circuit board, there is a light cutting method. 3 (a) to 3 (c), a conventional method of inspecting a substrate by a light cutting method will be described.

Generally, in this light cutting method, radial light generated by a laser or the like is magnified by a convex lens or the like, and is directly irradiated at a certain angle to a laser radiation surface and an inspection surface of an object to be measured. On the other hand, the unevenness of the bright line formed by the height of the part is measured two-dimensionally and the height is calculated.

In FIG. 3A, a laser beam 10 emitted from a laser light source (not shown) is thinly opened in a narrow fan shape by a predetermined method, and is irradiated on a solder 30 mounted on a substrate 20.

Then, as shown in FIG. 3B, the difference in the position of the bright line of the laser beam 10 due to the difference in the height of the solder 30 occurs. The shift of the bright line, which is the difference in the position of the bright line of the laser beam 10, is detected by an optical sensor 40 (for example, an image pickup tube, a two-dimensional CCD camera that is a solid-state image sensor, an area CCD camera, a two-dimensional sensor, etc.) from above. An image is taken and x, which is the difference between the bright line on the solder 30 and the bright line on the substrate, is measured by this graphic analysis.

Next, as shown in FIG. 3C, if the incident angle of the laser is θ, the height h of the solder 30 to be obtained is:
Using the measurement result x obtained above, h = x · tan θ (1) can be obtained.

The volume of the solder 30 can be measured from the height h of the solder 30 and the bottom area of the solder 30.

[0009]

However, in the above-mentioned conventional light cutting method, the size of the luminescent spot depends on the thickness of the beam of the laser beam 10. Therefore, in order to increase the height accuracy of the cream solder to be measured, In addition, it is necessary to reduce the beam diameter, and when the beam diameter is reduced by the lens, there is a disadvantage that the depth of focus is reduced and the resolution changes depending on the position and height of the measurement object. Further, in order to increase the resolution by using an optical sensor, it is necessary to use an area type CCD camera having a large number of pixels, which is expensive. Further, even when the area-type CCD camera or the like is used, there is a limit in resolution as compared with, for example, the case where a one-dimensional line-type CCD camera is used.

Further, the laser beam 10 must be incident on the object at a certain angle from the front, and the shift of the bright line must be measured from the upper surface of the object from a direction different from the incident direction. It is necessary to install the optical sensors at a certain distance from each other, and there is a problem that the board inspection apparatus itself becomes thick.

Therefore, the present invention measures the size of the object to be measured on the substrate by increasing the resolution using inexpensive means, and
An object of the present invention is to make a board inspection apparatus itself compact.

[0012]

According to a first aspect of the present invention, there is provided a method for inspecting a substrate, comprising the steps of: applying a light beam having a planar spread to a substrate including a bright line portion on an object to be measured; A light irradiation step of projecting the substrate from obliquely above the substrate so that the bright lines are arranged on a straight line, and an imaging step of photographing the state of the bright line from above the substrate along the bright line on the straight line, Analyzing the state of the captured bright line to calculate the dimensions of the object to be measured.

According to a second aspect of the present invention, in the substrate inspection method according to the first aspect of the present invention, the imaging step includes the step of using the one-dimensional sensor to scan the substrate along the bright line on the straight line. The state of the bright line is photographed from above.

According to a third aspect of the present invention, there is provided a substrate inspection method according to any one of the first to second aspects, wherein the image analysis step calculates a gap between bright lines. The height of the measurement object is calculated using a light irradiation angle with respect to the substrate.

According to a fourth aspect of the present invention, in the substrate inspection method according to any one of the first to third aspects, the light irradiation step emits a light beam, and the emitted light beam is enlarged. The expanded light beam is converted into a light beam having a planar spread.

According to a fifth aspect of the present invention, there is provided the substrate inspection apparatus according to any one of the first to fourth aspects, wherein the phase of the light beam having the planar spread is changed. Is what you do.

According to a sixth aspect of the present invention, there is provided the substrate inspection apparatus, wherein the luminous flux having a planar spread is arranged such that the bright lines are linearly arranged on the substrate including the bright line portion on the object to be measured. Light irradiating means for projecting the substrate obliquely from above, imaging means arranged above the substrate along the bright line on the straight line, and imaging the state of the bright line; Image analyzing means for analyzing the state and calculating the dimensions of the measurement object.

In a seventh aspect of the present invention, there is provided the board inspection method according to the sixth aspect, wherein the imaging means is a one-dimensional sensor.

According to an eighth aspect of the present invention, in the substrate inspection apparatus according to any one of the sixth to seventh aspects, the image analysis means calculates an interval between bright line breaks. The height of the object to be measured is calculated using the light irradiation angle with respect to.

A ninth aspect of the present invention is the substrate inspection apparatus according to any one of the sixth to eighth aspects, wherein the light irradiating means includes a light source that emits a light beam, and the emitted light beam. And means for converting the expanded light beam into a light beam having a planar spread.

According to a tenth aspect of the present invention, there is provided a substrate inspection apparatus according to any one of the sixth to ninth aspects.
Vibration means for changing the phase of the light beam having the planar spread is further added.

Therefore, according to the present invention, the imaging means:
It suffices if the condition of the bright line on the straight line appearing on the substrate can be imaged, and the light irradiating means is configured to project the luminous flux from obliquely above the substrate, and the photographing means is arranged at an upper position along the bright line of the substrate. Therefore, it is not necessary to dispose the light irradiating means and the photographing means separately.

According to the fifth or tenth aspect of the present invention, since the light beam has the same function as described above and the light beam is vibrated, the light beam having a changed phase is irradiated on the object to be measured.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2A to 2C show an embodiment of the present invention. In this embodiment, a case where the height and the volume of the cream solder are measured with the cream solder as the measurement object will be described.

FIG. 1 is a schematic perspective view of a substrate inspection apparatus according to this embodiment. In FIG. 1, the substrate inspection apparatus of the present invention irradiates a cream flux 5 printed on a substrate 6 with a light beam having a planar spread using a light irradiating means (not shown), and a one-dimensional sensor 4 serving as an imaging means. However, the break of the bright line caused by the height of the cream solder 5 is measured, and the image analysis means (not shown) calculates the size of the solder 5 using the measurement result.

FIG. 2A is a schematic side view of the substrate inspection apparatus of the present embodiment. In FIG. 2A, the light irradiating means is composed of a laser light source 1, a cylindrical lens, a plano-convex lens 2, and a mirror 3. The light is projected obliquely onto the substrate 6 so that the bright lines are arranged on the substrate 6 in a straight line.

The laser light source 1 emits a light beam having a uniform phase. The laser light source 1 is arranged on the same straight line as a one-dimensional sensor 4 described below. In this embodiment, a laser is indirectly applied to the solder 5. Irradiation.

A cylindrical lens (not shown) is stored, for example, at the tip of the laser light source 1 and expands a light beam emitted from the laser light source 1. The plano-convex lens 2 converts the expanded light beam into a parallel light beam having a planar spread.
The mirror 3 irradiates the solder 5 with a parallel light beam having a planar spread at a certain incident angle θ.

The one-dimensional sensor 4 serving as an image pickup means is a one-dimensional line sensor type CCD in which the sensors are arranged one-dimensionally, and is arranged on the substrate 6 along the linear bright line. Then, the state of the bright line a arranged in a straight line as shown in FIG.

An image analysis means (not shown) forms an image of the state of the captured bright line, and reads the length x of the cut line b of the bright line a arranged in a straight line as shown in FIG. 2B. Then, assuming that the incident angle of the parallel light beam is θ and the height of the solder 5 is h, the height of the solder 5 is obtained by h = x · tan θ, and the measurement result and the area of the solder 30 which are known in advance are obtained. Calculate volume from.

Here, the reason why the light incident on the plano-convex lens 2 is converted into a parallel light beam will be described. If the incident light is not a parallel light beam, the resolution will vary depending on the position of the object, and the parallel light beam will ease the conditions for the light beam, thereby providing the advantage that the light beam can be made wider than the measurement target range. Because.

In the above configuration, the light beam emitted from the laser light source 1 is expanded by a cylindrical lens, and the expanded light beam is converted into a plane and parallel light beam by the plano-convex lens 2. The luminous flux converted into a parallel luminous flux on this surface is reflected by the mirror 3 and irradiates the solder 5 at a certain angle θ, and the bright lines a are arranged in a straight line as shown in FIG. A break b in the bright line caused by the height of 5 appears.

Then, the state of the bright lines a arranged in a straight line is imaged by the one-dimensional sensor 4, and the image analyzing means forms an image of the state of the bright lines thus captured, and obtains the height h of the solder 5.
Further, the volume is calculated from the measurement result and the area of the solder 5 known in advance.

Therefore, according to the present invention, the imaging means:
It is only necessary to be able to image the state of the bright line a on the straight line appearing on the substrate 6, so a one-dimensional sensor is sufficient.

The light irradiating means projects a light beam from obliquely above the substrate 6.
The light irradiation means and the one-dimensional sensor 4 do not need to be separated from each other, so that the apparatus can be made compact.

Next, a modification of this embodiment will be described.
In this embodiment, a vibration device (not shown) is added in order to avoid speckle noise from a rough surface peculiar to the coherence of the laser. For example, as the vibration device, the mirror 3
A piezoelectric buzzer is attached to the device and vibrated at a predetermined frequency.

Therefore, the phase of the light beam incident on the solder 5 varies, so that speckle noise can be avoided, and time averaging and spatial averaging are performed.
The conditions of the surface accuracy of the optical components and mirrors to be used are relaxed, so that inexpensive elements can be used, and the economic effect is further improved.

In the above embodiment, the light is bent by using the mirror 3 and the light flux is incident on the solder 5.
Alternatively, the solder 5 may be directly irradiated with a light beam having a spread on a plane without passing through.

In the above embodiment, the area of the solder 5 is known in advance. For example, the area of the solder 5 is obtained from the measurement result of the one-dimensional sensor expressed as a surface by moving the substrate 6. You can do it.

Further, the incident angle of the incident light beam may be changed according to the pitch between the solders 5.

In the above embodiment, the height of the solder applied to the printed circuit board was measured. However, other than this, the height of the board required for the height, for example, the height of the pattern of the solar cell,
The present invention can also be applied to the height of a glass partition wall formed in a high-definition lattice.

[0042]

As described above, according to the present invention,
The imaging means only needs to be able to image the state of the bright line on the straight line appearing on the substrate. For example, a one-dimensional sensor is sufficient.
Further, the light irradiating means is configured to project a light beam from obliquely above the substrate, and the photographing means may be arranged at an upper position along the bright line of the substrate. No need to provide a compact device.

According to the second or seventh aspect of the present invention, the one-dimensional sensor has the above-mentioned effects, and the one-dimensional sensor is inexpensive even at a high resolution. This has the effect of achieving

Further, according to the invention according to claim 5 or claim 10 of the present invention, while having the above effects, for example, speckle noise from a rough surface peculiar to the coherence of a laser is prevented. In addition to this, the conditions of the surface accuracy of the optical components, mirrors, and the like to be used are relaxed, so that it is possible to use inexpensive elements.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a board inspection apparatus (an embodiment).

FIG. 2 (a) is a schematic side view of a substrate inspection apparatus (embodiment example), and FIG. 2 (b) is a plan view of a substrate including a solder portion by performing optical cutting using the substrate inspection apparatus (embodiment example). ),
(C) is a side view of the substrate including the solder portion by performing optical cutting using the above-described substrate inspection apparatus (embodiment example).

3A is a schematic perspective view of a board inspection apparatus (conventional example), FIG. 3B is a plan view of a board including a solder portion by performing optical cutting using the board inspection apparatus (conventional example),
(C) is a side view of a substrate including a solder portion, which is subjected to light cutting using the above-described substrate inspection apparatus (conventional example)

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light source (light irradiation means) 2 ... Plano-convex lens (light irradiation means) 3 ... Mirror (light irradiation means) 4 ... One-dimensional sensor (imaging means) 5 ... Solder (object to be measured)

Claims (10)

[Claims] 1. A light irradiation process in which a light beam having a planar spread is projected obliquely upward onto a substrate, including a bright line portion on a measurement object, such that bright lines are arranged in a straight line on the substrate. An imaging step of capturing the state of the bright line from above the substrate along the bright line on the straight line; an image analyzing step of analyzing the state of the captured bright line to calculate a dimension of the measurement object; A substrate inspection method, comprising: 2. The substrate inspection method according to claim 1, wherein in the imaging step, a state of the bright line is photographed from above the substrate along the bright line on the straight line using a one-dimensional sensor. . 3. The image analysis process according to claim 1, wherein an interval between the bright lines is calculated, and a height of the measurement object is calculated using a light irradiation angle with respect to the substrate. 3. The substrate inspection method according to 2. 4. The light irradiation process according to claim 1, wherein the light irradiating step emits a light beam, expands the emitted light beam, and converts the expanded light beam into a light beam having a planar spread. The substrate inspection method according to claim 1. 5. The method according to claim 1, wherein the phase of the light beam having the planar spread is changed.
The substrate inspection method according to the above section. 6. A light irradiating means for projecting a light beam having a planar spread from an obliquely upward direction onto a substrate, including a bright line portion on an object to be measured, such that bright lines are arranged in a straight line on the substrate. And disposed above the substrate along the bright line on the straight line,
A board inspection apparatus, comprising: an imaging unit that captures the state of the bright line; and an image analysis unit that analyzes the state of the bright line captured by the imaging unit to calculate the dimension of the measurement target. 7. The board inspection apparatus according to claim 6, wherein the imaging unit is a one-dimensional sensor. 8. The image analysis means according to claim 6, wherein the distance between the breaks of the bright line is calculated, and the height of the object to be measured is calculated using the light irradiation angle with respect to the substrate. A substrate inspection apparatus according to item 1. 9. The light irradiating means includes: a light source for emitting a light beam; a means for expanding the emitted light beam; and a means for converting the expanded light beam to a light beam having a planar spread. The substrate inspection apparatus according to any one of claims 6 to 8, wherein 10. The substrate inspection apparatus according to claim 6, further comprising a vibration unit for changing a phase of the light beam having the planar spread.