JP2017072385A - Three-dimensional measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-dimensional measurement device with which it is possible to improve a measurement speed while maintaining necessary measurement accuracy when performing three-dimensional measurement utilizing a phase shift method.SOLUTION: A substrate inspection device 1 comprises a lighting device 4 for irradiating the surface of a printed circuit board 2 with a prescribed light pattern from diagonally above, a camera 5 for capturing the image of a portion of the printed circuit board 2 that is irradiated with the light pattern, and a control device 6 for executing various control, image process, and arithmetic process in the substrate inspection device 1. For an inspection area that includes cream solder that satisfies a prescribed determination condition, the control device 6 acquires image data by a four-time image-capturing method and executes three-dimensional measurement with high accuracy; on the other hand, for other than this inspection area, the control device 6 acquires image data by a two-time image-capturing method and thereby executes three-dimensional measurement in a short time.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a three-dimensional measurement apparatus that performs three-dimensional measurement using a phase shift method.

  Generally, when an electronic component is mounted on a printed circuit board, cream solder is first printed on a predetermined electrode pattern disposed on the printed circuit board. Next, an electronic component is temporarily fixed on the printed circuit board based on the viscosity of the cream solder. Thereafter, the printed circuit board is guided to a reflow furnace, and soldering is performed through a predetermined reflow process. In recent years, it is necessary to inspect the printed state of the cream solder in a stage before being led to the reflow furnace, and a three-dimensional measuring device is sometimes used for such inspection.

  In recent years, various so-called non-contact type three-dimensional measuring apparatuses using light have been proposed. For example, a technique related to a three-dimensional measuring apparatus using a phase shift method has been proposed.

  In the three-dimensional measuring apparatus using the phase shift method, a combination of a light source that emits predetermined light and a grating that converts light from the light source into a light pattern having a sinusoidal (stripe) light intensity distribution. The light pattern is irradiated onto the printed circuit board (object to be measured) by the irradiation means. And it observes using the imaging means which has arrange | positioned the point on a board | substrate directly above. As the imaging means, a CCD camera or the like including a lens and an imaging element is used.

  Under the above configuration, the light intensity (luminance) I of each pixel on the image data picked up by the image pickup means is given by the following equation (U1).

I = f · sinφ + e (U1)
Where f: gain, e: offset, and φ: phase of the light pattern.

Here, the phase of the light pattern is changed in, for example, four stages (φ + 0, φ + 90 °, φ + 180 °, φ + 270 °) by transferring or switching the grating, and intensity distributions I ₀ , I ₁ , corresponding to these are changed. Image data having I ₂ and I ₃ is captured, f (gain) and e (offset) are canceled based on the following equation (U2), and the phase φ is obtained.

φ = tan ⁻¹ [(I ₁ −I ₃ ) / (I ₂ −I ₀ )] (U2)
And using this phase (phi), the height (Z) in each coordinate (X, Y) on a printed circuit board is calculated | required based on the principle of triangulation (for example, refer patent document 1).

  On the other hand, in recent years, instead of the four-time imaging method described above, a three-time imaging method has been proposed in which the phase of the light pattern is changed in three stages and the phase φ is acquired from three types of image data (for example, , See Patent Document 2).

JP-A-5-280945 JP 2002-81924 A

  However, since the four-time imaging method performs measurement based on more image data, high-accuracy measurement is possible, but measurement (particularly, acquisition of image data) takes time. On the other hand, the three-time imaging method shortens the measurement time, but the measurement accuracy may be insufficient for a relatively small size cream solder (measurement target).

  Therefore, much time is required for the measurement in the inspection of the printed circuit board including the relatively small-sized cream solder that requires high-precision measurement.

  For example, if it is assumed that the time required for one imaging is [10 msec] and the time required for one grid switching is [20 msec] for each predetermined measurement area (imaging area), the predetermined measurement is performed. In the case of the four-time imaging method, the time required until all the imaging processes related to the region (the last imaging process) are completed, as shown in FIG. 8A, [time required for imaging process [10 ms] × 4 times] + [time required for switching the grid [20 ms] × 3 times] = total [100 msec]. On the other hand, in the case of the three-time imaging method, as shown in FIG. 8B, [time required for imaging processing [10 ms] × 3 times] + [time required for grid switching [20 ms] × 2 times] = Total [70 msec].

  Of course, when a large number of measurement areas are set on a single printed board, the time required to measure the single printed board is several times as long.

  Note that the above-described problem is not limited to the height measurement of cream solder or the like printed on a printed circuit board, but is inherent in the field of other three-dimensional measurement devices.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to improve measurement speed while maintaining necessary measurement accuracy in performing three-dimensional measurement using the phase shift method. It is to provide a three-dimensional measuring apparatus.

  Hereinafter, each means suitable for solving the above-described problem will be described separately. In addition, the effect specific to the means to respond | corresponds as needed is added.

Means 1. Irradiation means capable of irradiating an object to be measured (for example, a printed circuit board) with a light pattern having a striped light intensity distribution;
Imaging means capable of imaging a predetermined measurement region (measurement area) on the object to be measured irradiated with the light pattern;
By controlling the irradiation unit and the imaging unit, the phase of the light pattern is changed in a plurality of ways, and a plurality of images (image data) relating to the measurement area captured under each light pattern can be acquired. An image acquisition means configured to change the number of images to be acquired (captured) for the measurement area according to the measurement area;
Based on the image acquired by the image acquisition means, provided with an image processing means capable of performing three-dimensional measurement on a measurement target (for example, cream solder) in the measurement region by a phase shift method,
The image acquisition means includes
When the measurement object satisfying a predetermined determination condition is included in the measurement region, the first predetermined number of images obtained by irradiating and imaging a light pattern with a first predetermined number (for example, four) of phases. Get an image,
When the measurement target satisfying the determination condition is not included in the measurement region, the light pattern is irradiated and imaged with a second predetermined number (for example, three) of phases smaller than the first predetermined number. A three-dimensional measuring apparatus that acquires the second predetermined number of images.

  In general, various types of cream solder of different sizes are printed on a printed circuit board measured by a three-dimensional measuring apparatus, and the types and arrangements thereof are different for each measurement region. In other words, there may be a measurement region that does not require high-precision measurement even for a printed circuit board that includes relatively small-sized cream solder that requires high-precision measurement.

  Nevertheless, in the past, all the measurement areas set on the printed circuit board have the same preset imaging method (for example, four times imaging method and high measurement accuracy are required for high-precision measurement). If the measurement is performed in a shorter time, the measurement is performed uniformly by the three-time imaging method).

  On the other hand, according to the means 1, the measurement region including the measurement target that satisfies the predetermined determination condition (for example, the size is less than the predetermined value) is based on the first predetermined number (for example, four) of images. While highly accurate 3D measurement is performed, for other measurement areas, 3D measurement is performed in a short time based on a second predetermined number (for example, three) of images smaller than the first predetermined number. can do.

  As a result, when performing three-dimensional measurement using the phase shift method, the measurement speed is improved while maintaining the measurement accuracy required for measurement objects (measurement objects that require high-accuracy measurement) that satisfy the predetermined criteria. Can be achieved.

  In the “predetermined determination condition”, the size of the measurement target is less than a predetermined value (for example, “area”, “volume”, “perimeter” or “short side length” is less than a predetermined value. And that the measurement target belongs to a predetermined attribute (for example, the type of component mounted on the cream solder to be measured is a predetermined type). Whether or not a measurement target satisfying a predetermined determination condition is included in the measurement region is determined based on design data (gerber data or the like) related to the measurement object stored in advance in a predetermined storage unit. be able to.

Mean 2. When the image acquisition means acquires the first predetermined number of images (for example, four),
The image processing means includes
For the measurement target that satisfies the determination condition in the measurement region, based on the first predetermined number of images, three-dimensional measurement is performed by a phase shift method,
For the measurement target that does not satisfy the determination condition in the measurement region, the measurement unit 1 performs three-dimensional measurement by a phase shift method based on the second predetermined number (for example, three) of images. The three-dimensional measuring apparatus described.

  According to the above means 2, three-dimensional measurement can be performed in a short time on the basis of a smaller number of images for a measurement target that does not satisfy the predetermined determination condition (measurement target that does not require much measurement accuracy). As a result, the measurement speed can be further improved.

  In addition, when the first predetermined number of images (for example, four types) are acquired, the light is measured with the measurement accuracy for the “measurement target that does not satisfy the predetermined determination condition” and the second predetermined number (for example, three types) of phases. When three-dimensional measurement is performed on the basis of a second predetermined number of images that are irradiated and imaged with a pattern, the measurement accuracy for “a measurement object that does not satisfy a predetermined determination condition” can be made equal.

  Means 3. The three-dimensional measuring apparatus according to means 1 or 2, further comprising condition setting means capable of setting the determination condition based on an external operation.

  According to the means 3, a predetermined determination condition can be arbitrarily set, and convenience and versatility can be improved.

  Means 4. 4. The three-dimensional measuring apparatus according to claim 3, further comprising a scheduled time display unit capable of displaying a scheduled time for measuring the object to be measured under the determination condition set by the condition setting unit.

  According to the above means 4, it is not necessary to actually operate the three-dimensional measuring apparatus many times in advance in order to find the optimum determination condition that satisfies the measurement time and measurement accuracy required by the operator. As a result, convenience can be improved.

Means 5. The image acquisition means includes
When the measurement target satisfying the determination condition is included in the measurement region, the first predetermined number of four or three types of images obtained by irradiating a light pattern with three or three phases are imaged. Get an image,
When the measurement target that satisfies the determination condition is not included in the measurement area, two images obtained by irradiating a light pattern with two phases as the second predetermined number are acquired. The three-dimensional measuring apparatus according to any one of means 1 to 4, which is characterized.

  According to the above means 5, three-dimensional measurement can be performed in a short time based on fewer images for a measurement target that does not satisfy the predetermined determination condition (measurement target that does not require much measurement accuracy). As a result, the measurement speed can be further improved.

Means 6. The image acquisition means includes
When the measurement target satisfying a specific condition among the determination conditions is included in the measurement region, four images captured by irradiating a light pattern with four phases as the first predetermined number Get
When the measurement target that satisfies the determination condition is included in the measurement region, but the measurement target that satisfies the specific condition is not included, the first predetermined number of light is transmitted in three phases. Acquire three images captured by irradiating the pattern,
When the measurement target that satisfies the determination condition is not included in the measurement area, two images obtained by irradiating a light pattern with two phases as the second predetermined number are acquired. The three-dimensional measuring apparatus according to any one of means 1 to 4, which is characterized.

  According to the means 6, in addition to the function and effect of the means 5, it is possible to deal with the difference in measurement object more finely and to further improve the measurement speed.

Furthermore, in the means 6 under the structure of the means 2,
“When the image acquisition means has acquired four images,
The image processing means includes
For the measurement object that satisfies the specific condition in the measurement region, based on four images, three-dimensional measurement is performed by the phase shift method,
For the measurement object that does not satisfy the specific condition in the measurement region and satisfies the determination condition, based on three images, perform three-dimensional measurement by a phase shift method,
For a measurement target that does not satisfy the determination condition in the measurement region, based on two images, three-dimensional measurement is performed by a phase shift method,
In the case where the image acquisition means acquires three images,
The image processing means includes
For the measurement object that satisfies the determination condition in the measurement region, based on three images, three-dimensional measurement is performed by the phase shift method,
For a measurement target that does not satisfy the determination condition in the measurement region, if three-dimensional measurement is performed by the phase shift method based on two images, further improvement in measurement accuracy can be achieved.

Means 7. The image processing means includes
The relationship between gain and offset determined by predetermined imaging conditions,
By using the gain or offset value related to the pixel determined from the luminance value of each pixel on the image,
The three-dimensional measurement apparatus according to means 5 or 6, wherein the three-dimensional measurement by the phase shift method can be executed based on two kinds of images.

  According to the means 7, the relationship between the gain A and the offset B determined by a predetermined imaging condition [for example, A = K (proportional constant) × B] and the luminance value V (x of each pixel (x, y) on the image. , Y) and the gain A (x, y) or the value of the offset B (x, y) relating to the pixel (x, y) determined by the phase shift method based on two images. Three-dimensional measurement can be performed.

  As a result, the measurement time can be drastically shortened as compared with the prior art that requires four or three images.

  In general, the “irradiation means” includes a light source that emits predetermined light and a grating that converts light from the light source into a light pattern having a striped light intensity distribution, and the light pattern is applied to an object to be measured. It is configured to be able to irradiate.

  The light emitted from the light source is first attenuated when passing through the grating, then attenuated when reflected by the measurement object (measurement target), and finally A / D conversion (analog- After being attenuated during digital conversion, it is acquired as the luminance value of each pixel of the image.

  Therefore, the luminance value of each pixel of the image captured by the imaging means is the brightness (luminance) of the light source, the attenuation rate when the light emitted from the light source passes through the grating, and the light is reflected by the object to be measured. It can be expressed by multiplying the reflectance at the time, the conversion efficiency at the time of A / D conversion (analog-digital conversion) in the imaging means, and the like.

For example, the brightness of the light source (uniform light): L
Transmittance of lattice: G = αsinθ + β
α and β are arbitrary constants.

Reflectance at coordinates (x, y) on the measurement object: R (x, y)
Conversion efficiency of each pixel of the imaging means (imaging device): E
The luminance value of the pixel on the image corresponding to the coordinate (x, y) on the object to be measured: V (x, y)
Gain of light pattern at coordinates (x, y) on the measurement object: A (x, y)
Offset of light pattern at coordinates (x, y) on the measurement object: B (x, y)
In this case, it can be expressed by the following formula (F1).

Here, the gain A (x, y) is a luminance value V (x, y) _MAX due to light of “sin θ = 1” and a luminance value V (x, y) _MIN due to light of “sin θ = −1”. Can be expressed from the difference between
For example, transmittance when the grating is θ = 0 (= average transmittance): Gθ _{= 0}
Transmittance when the grating is θ = π / 2 (= maximum transmittance): Gθ ₌ π _{/ 2}
Transmittance when the grating is θ = −π / 2 (= minimum transmittance): Gθ ₌ −π _{/ 2}
In this case, it can be expressed by the following formula (F2).

The offset B (x, y) is the luminance value V (x, y) in the light of “sin θ = 0”, and the luminance value V (x, y) _{MAX in} the light of “sin θ = 1” Since it is an average value with the luminance value V (x, y) _MIN by the light of “sin θ = −1”, it can be expressed by the following formula (F3).

That is, the maximum value V (x, y) _MAX , the minimum value V (x, y) _MIN , and the average value V (x, y) _AV of the luminance value are expressed by the following equations (F4), (F5), and (F6), respectively. The relationship is as shown in the graph of FIG.

As can be seen from FIG. 3, the average value V (x, y) of the maximum value V (x, y) _MAX of the luminance value and the minimum value V (x, y) _MIN of the luminance value at a predetermined coordinate (x, y). y) _AV becomes an offset B (x, y), the difference between the offset B (x, y) and the maximum value V (x, y) _MAX , and the offset B (x, y) and the minimum value V ( x, y) The difference from _MIN is the gain A (x, y).

  Further, since the luminance value V (x, y) changes in proportion to the brightness L or the reflectance R (x, y) of the light source, for example, at the coordinate position where the reflectance R is halved, the gain A and the offset The value of B is also halved.

  Next, after formulating the above formulas (F2) and (F3) into the following formulas (F2 ′) and (F3 ′) and arranging them together, the following formula (F7) can be derived.

  Further, when the above equation (F7) is solved for A (x, y), the following equation (F8) is obtained, which can be expressed as a graph shown in FIG.

  That is, when one of the brightness L or the reflectance R (x, y) of the light source is fixed and the other is changed, the offset B (x, y) increases and decreases and the offset B (x, y) ), The gain A (x, y) also increases / decreases. If one of the gain A and the offset B is known from the equation (F8), the other can be obtained. Here, the proportionality constant K is determined by the transmittance G of the grating irrespective of the brightness L and the reflectance R of the light source. In other words, the following means 8 and 9 can be used in other words.

  Means 8. 8. The three-dimensional measuring apparatus according to claim 7, wherein the relationship between the gain and the offset is a relationship in which the gain and the offset are uniquely determined from each other.

  If the relationship between the gain A and the offset B is uniquely determined, for example, by creating a numerical table or table data representing the relationship between the gain A and the offset B, the offset B from the gain A or the offset The gain A can be obtained from B.

  Means 9. The three-dimensional measuring apparatus according to claim 7, wherein the gain and the offset are in a proportional relationship between the gain and the offset.

  If the gain and the offset are in a proportional relationship, for example, it can be expressed by a relational expression such as A = K × B + C [where C is the dark current (offset) of the camera]. The gain A can be obtained from B. As a result, it can be set as the following means 10.

Means 10. When the luminance values of the pixels of the two images when the relative phase relationships of the light patterns relating to the two images are 0 and γ, respectively, are V ₀ and V ₁ , respectively,
The image processing means includes
The three-dimensional measurement according to any one of means 7 to 9, wherein a phase θ satisfying a relationship of the following formulas (1), (2), and (3) is obtained, and three-dimensional measurement is performed based on the phase θ: apparatus.

V ₀ = Asinθ + B (1)
V ₁ = Asin (θ + γ) + B (2)
A = KB (3)
However, γ ≠ 0, A: gain, B: offset, K: proportional constant.

  According to the means 10, the following formula (4) can be derived by substituting the formula (3) into the formula (1).

V ₀ = KBsinθ + B (4)
When this is solved for the offset B, the following equation (5) can be derived.

B = V ₀ / (Ksinθ + 1) (5)
Further, the following formula (6) can be derived by substituting the above formula (3) into the above formula (2).

V ₁ = KBsin (θ + γ) + B (6)
By substituting the above equation (6) into the above equation (5) and rearranging as shown in the following [Equation 7], the following equation (7) can be derived.

Here, when “V ₀ cos γ−V ₁ = a”, “V ₀ sin γ = b”, and “(V ₀ −V ₁ ) / K = c” are set, the above equation (7) becomes the following equation (8): It can be expressed as

asinθ + bcosθ + c = 0 (8)
Here, as shown in the following [Equation 8], when the above equation (8) is solved for the phase θ, the following equation (9) shown in the following [Equation 9] can be derived.

  Therefore, “the phase θ satisfying the relationship of the following formulas (1), (2), (3) in the above-mentioned means 10 and performing three-dimensional measurement based on the phase θ” means “the following formula ( In other words, the phase θ is obtained based on 9) and three-dimensional measurement is performed based on the phase θ ”. Of course, the algorithm for obtaining the phase θ is not limited to the above equation (9), and any other configuration may be adopted as long as the relationship of the above equations (1), (2), and (3) is satisfied. May be.

  If the dark current C of the camera described above is taken into account, the measurement accuracy can be further improved.

  Means 11. The three-dimensional measuring apparatus according to means 10, wherein γ = 180 °.

  According to the means 11, three-dimensional measurement is performed based on two images captured under two light patterns whose phases are different by 180 °.

  By setting γ = 180 ° in the above formula (2), the following formula (10) is derived.

V ₁ = Asin (θ + 180 °) + B
= -Asinθ + B (10)
Then, the following formula (11) can be derived from the above formulas (1) and (10). When this is solved for the offset B, the following formula (12) can be derived.

V ₀ + V ₁ = 2B (11)
B = (V ₀ + V ₁ ) / 2 (12)
Furthermore, the following formula (13) can be derived by substituting the above formula (12) into the above formula (3).

A = KB
= K (V ₀ + V ₁ ) / 2 (13)
Further, when the above equation (1) is arranged for “sin θ”, the following equation (1 ′) is obtained.

sin θ = (V ₀ −B) / A (1 ′)
Then, the following formula (14) can be derived by substituting the above formulas (12) and (13) into the above formula (1 ′).

sin θ = {V ₀ − (V ₀ + V ₁ ) / 2} / {K (V ₀ + V ₁ ) / 2}
= (V ₀ −V ₁ ) / K (V ₀ + V ₁ ) (14)
Here, when the above equation (14) is solved for the phase θ, the following equation (15) can be derived.

θ = sin ⁻¹ [(V ₀ −V ₁ ) / K (V ₀ + V ₁ )] (15)
That is, the phase θ can be specified by the known luminance values V ₀ and V ₁ and the constant K.

  Thus, according to the means 11, the phase θ can be obtained based on a relatively simple arithmetic expression, and further processing speed can be increased when performing the three-dimensional measurement of the measurement target.

  Means 12. The three-dimensional measuring apparatus according to means 10, wherein γ = 90 °.

  According to the means 12, three-dimensional measurement is performed based on two images captured under two light patterns whose phases are different by 90 °.

  By setting γ = 90 ° in the above equation (2), the following equation (16) is derived.

V ₁ = Asin (θ + 90 °) + B
= Acosθ + B (16)
When the above equation (16) is arranged for “cos θ”, the following equation (17) is obtained.

cos θ = (V ₁ −B) / A (17)
Further, when the above equation (1) is arranged with respect to “sin θ”, as described above, the following equation (1 ′) is obtained.

sin θ = (V ₀ −B) / A (1 ′)
Next, when the above formulas (1 ′) and (17) are substituted into the following formula (18), the following formula (19) is obtained. Further, by arranging this, the following formula (20) is derived.

sin ² θ + cos ² θ = 1 (18)
{(V ₀ −B) / A} ² + {(V ₁ −B) / A} ² = 1 (19)
(V ₀ −B) ² + (V ₁ −B) ² = A ² (20)
Then, when the above equation (3) is substituted into the above equation (20), the following equation (21) is obtained, and by further arranging this, the following equation (22) is derived.

(V ₀ −B) ² + (V ₁ −B) ² = K ² B ² (21)
(2-K ² ) B ² -2 (V ₀ + V ₁ ) B + V ₀ ² V ₁ ² = 0 (22)
Here, when the above equation (22) is solved for the offset B, the following equation (23) can be derived.

That is, the offset B can be specified by the known luminance values V ₀ and V ₁ and the constant K.

  Further, when the above formulas (1 ′) and (17) are substituted into the following formula (24), the following formula (25) is obtained, and by further arranging this, the following formula (26) is derived.

tanθ = sinθ / cosθ (24)
= {(V ₀ -B) / A} / {(V ₁ -B) / A} (25)
= (V ₀ -B) / (V ₁ -B) (26)
Then, when the above equation (26) is solved for the phase θ, the following equation (27) can be derived.

θ = tan ⁻¹ {(V ₀ −B) / (V ₁ −B)} (27)
That is, the phase θ can be specified by the known luminance values V ₀ and V ₁ and the constant K by using the above equation (23).

Thus, according to the means 12, the phase θ can be obtained based on the arithmetic expression using “tan ⁻¹ ”, so that it is possible to perform three-dimensional measurement in a range of 360 ° from −180 ° to 180 °. The measurement range can be made larger.

  Means 13. The three-dimensional measuring apparatus according to any one of means 7 to 12, further comprising a relation grasping means for grasping a relation between the gain and the offset in advance.

  As the relationship grasping means, for example, a configuration for grasping the relationship between gain and offset by calibration in advance can be cited. For example, the reference plate is irradiated with light patterns whose phases are changed in three or four ways, and the gain A and the offset B in each pixel are specified based on the three or four images picked up under these patterns. A constant K is determined from Equation (3). According to such a configuration, it is possible to perform more accurate measurement at each pixel.

  Further, as the relationship grasping means, for example, a configuration for grasping the relationship between the gain and the offset based on an image picked up at the time of measurement (measurement) performed separately can be given. According to such a configuration, the labor of calibration can be omitted, and the measurement time can be further shortened.

  Here, the “images taken at the time of separately performed measurement” include, for example, four or three images picked up under a light pattern whose phase has been changed in four or three ways, as well as two ways. Also included are two kinds of images taken under the light pattern whose phase is changed.

In the case where the relationship between the gain and the offset is grasped based on the two images captured under the light patterns whose phases are changed in two ways, for example, all the pixels of the image using the above equation (12) or the like. An offset B is obtained for, a luminance value V of a pixel having the same offset B value is extracted, and a histogram thereof is created. Then, the maximum value V _MAX and the minimum value V _MIN of the luminance value are determined from the histogram.

As described above, the average value of the maximum value V _MAX and the minimum value V _MIN of the luminance value is the offset B, and the half of the difference between the maximum value V _MAX and the minimum value V _MIN is the gain A. Based on this, the constant K can be determined from the above equation (3).

  Means 14. The measurement object is cream solder printed on a printed circuit board as the object to be measured, or a solder bump formed on a wafer substrate as the object to be measured. The three-dimensional measuring device according to any one of the above.

  According to the means 14, the height of the solder paste printed on the printed circuit board or the solder bump formed on the wafer substrate can be measured. As a result, in the inspection of cream solder or solder bumps, the quality of cream solder or solder bumps can be determined based on the measured values. Therefore, in such an inspection, the effect of each means described above is exhibited, and the quality determination can be performed with high accuracy. As a result, it is possible to improve the inspection accuracy in the solder printing inspection apparatus or the solder bump inspection apparatus.

It is a schematic perspective view which shows a board | substrate inspection apparatus typically. It is a block diagram which shows the electric constitution of a board | substrate inspection apparatus. It is a graph which shows the relationship between the brightness or reflectance of a light source, and a luminance value. It is a graph which shows the relationship between a gain and an offset. It is a figure which shows a condition setting screen. It is a flowchart which shows a test | inspection routine. It is a schematic diagram which shows the example of 1 aspect of the printed circuit board for demonstrating the arrangement | positioning relationship etc. of cream solder or a test | inspection area. (A)-(c) is a timing chart for demonstrating the processing operation of a camera and an illuminating device. It is a distribution table showing the distribution of the number of luminance values included in each data section. It is the histogram showing distribution of the number of the luminance values contained in each data section. It is a figure which shows the condition setting screen in another embodiment. It is a figure which shows the condition setting screen in another embodiment.

[First Embodiment]
Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram schematically illustrating a substrate inspection apparatus 1 including a three-dimensional measurement apparatus according to the present embodiment. As shown in FIG. 1, the board inspection apparatus 1 includes a mounting table 3 for mounting a printed board 2 as an object to be measured on which a cream solder as a measurement target is printed, and a surface oblique to the surface of the printed board 2. An illumination device 4 as an irradiating unit that irradiates a predetermined light pattern from above, and a camera 5 as an imaging unit for imaging a portion irradiated with the light pattern on the printed circuit board 2 (that is, reflected light from the portion). And a control device 6 for performing various controls, image processing, and arithmetic processing in the substrate inspection apparatus 1 such as drive control of the illumination device 4 and the camera 5. The control device 6 constitutes an image acquisition unit and an image processing unit in the present embodiment.

  The mounting table 3 is provided with motors 15 and 16, and the motors 15 and 16 are driven and controlled by the control device 6, so that the printed circuit board 2 mounted on the mounting table 3 can move in any direction ( X-axis direction and Y-axis direction).

  The illumination device 4 includes a light source 4a that emits predetermined light, and a liquid crystal lattice 4b that converts light from the light source 4a into a light pattern having a sinusoidal (stripe) light intensity distribution. On the other hand, it is possible to irradiate a striped light pattern whose phase changes in a plurality of ways from obliquely above.

  More specifically, in the illuminating device 4, the light emitted from the light source 4a is guided to a pair of condensing lenses by an optical fiber, and is converted into parallel light there. The parallel light is guided to the projection lens through the liquid crystal grating 4b. Then, a striped light pattern is irradiated onto the printed circuit board 2 from the projection lens.

  The liquid crystal lattice 4b includes a liquid crystal layer formed between a pair of transparent substrates, a common electrode disposed on one transparent substrate, and a plurality of strips arranged in parallel on the other transparent substrate so as to face the common electrode. Each of the grids corresponding to each band electrode by controlling on and off the switching elements (thin film transistors, etc.) connected to each band electrode by a drive circuit and controlling the voltage applied to each band electrode. The light transmittance of the line is switched to form a striped lattice pattern composed of a “bright portion” having a high light transmittance and a “dark portion” having a low light transmittance. And the light irradiated on the printed circuit board 2 via the liquid crystal grating 4b becomes a light pattern having a sinusoidal light intensity distribution due to blur caused by diffraction action or the like. Note that the lattice mode of the liquid crystal lattice 4b is switched and controlled by the control device 6 (lattice control means).

  The camera 5 includes a lens, an image sensor, and the like. A CMOS sensor is used as the image sensor. Of course, the imaging device is not limited to this, and a CCD sensor or the like may be employed, for example.

  Image data captured by the camera 5 is converted into a digital signal inside the camera 5, input to the control device 6 in the form of a digital signal, and stored in an image data storage device 24 described later. Then, the control device 6 performs image processing, inspection processing, and the like, which will be described later, based on the image data.

  Next, the electrical configuration of the control device 6 will be described. As shown in FIG. 2, the control device 6 is an “input” composed of a CPU and input / output interface 21 (hereinafter referred to as “CPU etc. 21”) that controls the entire board inspection apparatus 1, a keyboard, a mouse, a touch panel, and the like. An input device 22 as a "means", a display device 23 as a "display means" having a display screen such as a CRT or a liquid crystal, an image data storage device 24 for storing image data captured by the camera 5, and various calculation results. A calculation result storage device 25 for storing data and a setting data storage device 26 for storing various information such as Gerber data (design data) and calibration data described later are provided. These devices 22 to 26 are electrically connected to the CPU 21 or the like.

  Next, the inspection procedure of the printed circuit board 2 by the substrate inspection apparatus 1 will be described in detail. First, calibration performed before starting the inspection of the printed circuit board 2 will be described. The calibration is for grasping the variation (phase distribution) of the light pattern.

  In the liquid crystal lattice 4b, due to variations in characteristics (offset, gain, etc.) of the transistors connected to the strip electrodes, the voltages applied to the strip electrodes also vary. ", The light transmittance (luminance level) varies for each line corresponding to each strip electrode. As a result, the light pattern irradiated onto the object to be measured does not have a sinusoidal ideal light intensity distribution, and an error may occur in the three-dimensional measurement result.

  Therefore, so-called calibration or the like is performed to grasp the variation (phase distribution) of the light pattern in advance.

  As a calibration procedure, first, apart from the printed circuit board 2, a height position 0 and a flat reference surface are prepared. The reference surface has the same color as the cream solder to be measured. That is, the reflectances of the cream solder and the light pattern are equal.

  Then, while irradiating a light pattern with respect to the said reference surface, the reflected light is imaged with the camera 5, and the image data containing the luminance value of each coordinate is obtained. In the present embodiment, when calibration is performed, the phase of the light pattern is shifted by 90 °, and four types of image data captured under each light pattern are acquired.

  Then, the control device 6 calculates the phase θ of the light pattern at each pixel (coordinate) from the above four types of image data, and stores this in the setting data storage device 26 as calibration data.

  Furthermore, in the present embodiment, the gain A and the offset B of the light pattern in each pixel and the relationship between them are specified from the above four types of image data (see FIGS. 3 and 4), and this is used as calibration data as a setting data storage device. 26.

Here, the procedure for calculating the gain A and the offset B will be described in more detail. The relationship between the luminance values (V ₀ , V ₁ , V ₂ , V ₃ ) at each pixel of the four types of image data and the gain A and the offset B is expressed by the following equations (H1), (H2), (H3), It can be represented by (H4).

Then, the luminance values (V ₀ , V ₁ , V ₂ , V ₃ ) of the four kinds of image data are added, and the above equations (H1), (H2), (H3), and (H4) are expressed by the following [Equation 12]. The following formula (H5) can be derived by arranging as shown in FIG.

  Moreover, the following formula (H6) can be derived from the above formulas (H1) and (H3).

  Moreover, the following formula (H7) can be derived from the above formulas (H2) and (H4).

  Then, as shown in [Equation 15] below, when the above formulas (H6) and (H7) are substituted into the following formula (H8) and rearranged, the following formula (H9) can be derived.

  Further, the proportional constant K of the gain A and the offset B is calculated based on the following formula (H10) derived from the above formulas (H5) and (H9).

  Then, the gain A, the offset B, and the proportionality constant K of the light pattern in each pixel calculated as described above are stored in the setting data storage device 26 as calibration data. Of course, only the proportionality constant K may be stored as calibration data. Therefore, the above-described series of processing functions for determining the proportionality constant K constitutes the relationship grasping means in this embodiment.

  In the present embodiment, the calibration is performed based on the four types of image data captured under the four types of light patterns whose phases are different by 90 °. The calibration may be performed based on three types of image data captured under three different light patterns.

  Moreover, when performing calibration, it is good also as a structure performed by changing the brightness | luminance of a light source in multiple times. With this configuration, the dark current (offset) C of the camera 5 as shown in the following formula (28) can be obtained.

A = KB + C (28)
However, A: Gain, B: Offset, C: Dark current (offset) of the camera, K: Proportional constant.

  Alternatively, the relationship between the gain A and the offset B is not obtained as an equation, but by creating a numerical table or table data that represents the relationship between the gain A and the offset B, the gain A can be gained from the offset B or the offset B. You may comprise so that A can be calculated | required.

  Further, instead of calibration, four (or three) image data respectively captured under light patterns whose phases are changed in four (or three) phases at the time of measurement (measurement) performed separately are obtained. A configuration may be used in which the relationship between the gain A and the offset B (proportional constant K) is obtained.

  Next, the condition setting process performed before starting the inspection of the printed circuit board 2 will be described. In the condition setting process, a predetermined determination condition to be referred to when the control device 6 serving as an image acquisition unit determines the number of image data (number of imaging) to be acquired (imaged) for each inspection area (measurement area) is set in advance. Is to do. Therefore, the condition setting means in the present embodiment is configured by the function of the control device 6 (including the input device 22 and the display device 23) that executes the condition setting process.

  As will be described later, in the present embodiment, when cream solder satisfying the determination condition set here is included in the inspection area, the light pattern whose phase is changed in four ways as the first predetermined number is used. When four types of image data respectively captured below are acquired, but the cream solder satisfying the determination condition is not included in the inspection area, the light pattern having the phase changed in two ways as the second predetermined number It is the structure which acquires the two types of image data each imaged below.

  The condition setting process in the present embodiment is performed via a condition setting screen 230 (see FIG. 5) displayed on the display device 23. The condition setting screen 230 includes a plurality of item fields that can be set as determination conditions.

  More specifically, an “attribute” item field 231 that can be set as one of the determination conditions that the electronic component mounted on the cream solder is a predetermined type, the determination condition that the volume of the cream solder is less than the predetermined value "Volume" item column 232 that can be set as one of the above, "Area" item column 233 that can be set as one of the determination conditions that the area of the cream solder is less than a predetermined value, and the peripheral length of the cream solder is a predetermined value “Perimeter” item field 234 that can be set as one of the determination conditions, and “short side length” that can be set as one of the determination conditions that the short side length of the cream solder is less than a predetermined value An item column 235 is provided.

  Each item column 231 to 235 is provided with a check box 236 for selecting the item. In the present embodiment, a plurality of items can be selected simultaneously, such as “attribute” and “volume”. However, in this embodiment, when a plurality of items (conditions) are selected, if any one of the items is satisfied, the determination condition is satisfied (so-called OR condition). Of course, instead of this, it may be configured to satisfy the determination condition by satisfying all of the plurality of items (conditions) (so-called AND condition).

  In the “attribute” item column 231, the types of electronic components that are the determination conditions are SOP (Small Outline Package), SOJ (Small Outline Transducer), SFP (Quad Flat Package), QFP (Quad Flat Package), PLCC. (Plastic leaded chip carrier) and BGA (Ball grid array). Of course, the types of electronic components that are the determination conditions are not limited to these, and other types such as LGA (Land Grid Array) may be set as the determination conditions.

  In the “attribute” item column 231, check boxes 237 for selecting these types are provided corresponding to the types of electronic components. Here, a predetermined type of electronic component selected by checking the check box 237 is set as one of the determination conditions and stored in the setting data storage device 26.

  Note that the check box 237 of each product type can be input (selectable) only after the check box 236 in the “attribute” item column 231 is checked and the “attribute” item is selected. In the present embodiment, a plurality of types can be selected simultaneously, such as “SOP” and “SOJ”. However, in the present embodiment, when a plurality of types (conditions) are selected, if any one type is satisfied, the determination condition is satisfied (a so-called OR condition).

  On the other hand, each of the item fields 232 to 235 for “volume”, “area”, “perimeter” and “short side length” is provided with an input field 238 for inputting a numerical value as a determination condition. Here, the numerical value input in the input field 238 is set as one of the determination conditions and stored in the setting data storage device 26. Each input field 238 can be numerically input (selectable) only by checking the check box 236 of each corresponding item field 232 to 235 and selecting the item.

For example, where the case of setting the determination condition that "" volume "is" 1 mm ³ "less than" is the "" volume "is" 1 mm ³ "less than" cream solder contained in the inspection area In the case where the image data is acquired by the four-time imaging method, and the cream solder whose “volume” is less than “1 mm ³ ” is not included in the inspection area, the image data is acquired by the two-time imaging method. Will be acquired.

  Next, the inspection routine performed for each inspection area will be described in detail with reference to the flowchart of FIG. This inspection routine is executed by the control device 6 (CPU 21 or the like).

  The control device 6 first drives and controls the motors 15 and 16 to move the printed circuit board 2 so that the field of view of the camera 5 is adjusted to a predetermined inspection area on the printed circuit board 2. The inspection area is one area in which the surface of the printed circuit board 2 is divided in advance with the size of the field of view of the camera 5 as one unit.

  In step S101, it is determined whether or not cream solder that satisfies the predetermined determination condition (for example, the volume is less than a predetermined value) set in the condition setting process is included in the inspection area. This determination is made with reference to pre-stored Gerber data.

  The Gerber data stores, for example, the lands provided on the printed circuit board 2 and the position, size, shape, etc. of ideal cream solder printed on the lands. The type of electronic component to which it belongs is stored.

  Here, when the cream solder satisfying the determination condition is included in the inspection area, the process proceeds to step S102, and image data is acquired for the inspection area by the four-time imaging method. That is, four types of image data obtained by irradiating a light pattern with four phases and capturing images are acquired.

  More specifically, the control device 6 first switches and controls the liquid crystal lattice 4b of the illumination device 4, and sets the position of the lattice formed on the liquid crystal lattice 4b to a predetermined reference position (position of phase “0 °”). .

  When the switching setting of the liquid crystal lattice 4b is completed, the control device 6 starts the first imaging process under a light pattern having a phase “0 °” at a predetermined timing Ta1 (see FIG. 8A).

  Specifically, the light source 4a of the illuminating device 4 is caused to emit light and irradiation of the light pattern is started, and the camera 5 is driven and controlled to start imaging the inspection area portion irradiated with the light pattern. The procedure of the imaging process is the same in the second to fourth imaging processes described later.

  And the control apparatus 6 complete | finishes the 1st imaging process in the timing Ta2 after predetermined time (this embodiment 10 msec) progress from imaging start. That is, the irradiation of the light pattern is finished, and the first imaging related to the light pattern is finished. Here, the image data captured by the camera 5 is transferred to and stored in the image data storage device 24 (the same applies hereinafter).

  At the same time, the control device 6 starts the switching process of the liquid crystal lattice 4b of the illumination device 4 at the timing Ta2. Specifically, the process of switching the position of the grating formed on the liquid crystal grating 4b from the reference position (position of phase “0 °”) to the position of phase “90 °” in which the phase of the light pattern is shifted by a quarter pitch. To start.

  And the control apparatus 6 complete | finishes this switching process in the timing Ta3 after predetermined time (20 msec in this embodiment) progresses from the start (timing Ta2) of the switching process of the liquid crystal lattice 4b.

  Simultaneously with the completion of the switching process of the liquid crystal lattice 4b, the control device 6 starts the second imaging process under the light pattern having the phase “90 °” at the timing Ta3, and starts a predetermined time (in this embodiment, from the start of imaging). At the timing Ta4 after elapse of 10 msec), the second imaging process is terminated.

  Simultaneously with the end of the second imaging process, the control device 6 starts the switching process of the liquid crystal lattice 4b of the illumination device 4 at timing Ta4. Specifically, the process of switching the position of the grating formed on the liquid crystal grating 4b of the illumination device 4 from the position of the phase “90 °” to the position of the phase “180 °” in which the phase of the light pattern is shifted by a quarter pitch. To start.

  Simultaneously with the completion of the switching process of the liquid crystal lattice 4b, the control device 6 starts the third imaging process under the light pattern having the phase “180 °” at the timing Ta5, and starts the imaging for a predetermined time (in the present embodiment). At the timing Ta6 after elapse of 10 msec), the third imaging process is terminated.

  At the same time, the control device 6 starts switching processing of the liquid crystal lattice 4b of the illumination device 4 at timing Ta6. Specifically, the process of switching the position of the grating formed on the liquid crystal grating 4b from the position of the phase “180 °” to the position of the phase “270 °” in which the phase of the light pattern is shifted by a quarter pitch is started.

  Next, the control device 6 ends the switching process at a timing Ta7 after a predetermined time (20 msec in the present embodiment) has elapsed from the start of the switching process of the liquid crystal lattice 4b (timing Ta6).

  Simultaneously with the completion of the switching process of the liquid crystal lattice 4b, the control device 6 starts the fourth imaging process under the light pattern with the phase “270 °” at the timing Ta7, and starts the imaging for a predetermined time (in this embodiment). At the timing Ta8 after elapse of 10 msec), the fourth imaging process is terminated.

  In this way, by performing the above-described series of imaging processes, image data for four screens each captured under a light pattern whose phase has been changed in four ways is acquired.

  On the other hand, if it is determined in step S101 that cream solder satisfying the determination condition is not included in the inspection area, the process proceeds to step S103, and image data is acquired for the inspection area by the twice imaging method. . That is, two types of image data obtained by irradiating light patterns with two phases and capturing images are acquired.

  More specifically, the control device 6 first switches and controls the liquid crystal lattice 4b of the illumination device 4, and sets the position of the lattice formed on the liquid crystal lattice 4b to a predetermined reference position (position of phase “0 °”). .

  When the switching setting of the liquid crystal lattice 4b is completed, the control device 6 starts the first imaging process under a light pattern with a phase “0 °” at a predetermined timing Tc1 (see FIG. 8C).

  Specifically, the light source 4a of the illuminating device 4 is caused to emit light and irradiation of the light pattern is started, and the camera 5 is driven and controlled to start imaging the inspection area portion irradiated with the light pattern. The procedure of the imaging process is the same in the second imaging process described later.

  And the control apparatus 6 complete | finishes the 1st imaging process in the timing Tc2 after predetermined time (this embodiment 10 msec) progress after imaging start. That is, the irradiation of the light pattern is finished, and the first imaging related to the light pattern is finished. Here, the image data captured by the camera 5 is transferred to and stored in the image data storage device 24 (the same applies hereinafter).

  At the same time, the control device 6 starts the switching process of the liquid crystal lattice 4b of the illumination device 4 at the timing Tc2. Specifically, the process of switching the position of the grating formed on the liquid crystal grating 4b from the reference position (position of phase “0 °”) to the position of phase “180 °” in which the phase of the light pattern is shifted by a half pitch. To start.

  Then, the control device 6 ends the switching process at a timing Tc3 after a predetermined time (20 msec in this embodiment) has elapsed from the start of the switching process of the liquid crystal lattice 4b (timing Tc2).

  Simultaneously with the completion of the switching process of the liquid crystal lattice 4b, the control device 6 starts the second imaging process under the light pattern with the phase “180 °” at the timing Tc3, and starts the imaging for a predetermined time (in this embodiment). At the timing Tc4 after elapse of 10 msec), the second imaging process is terminated.

  As described above, by performing the above-described series of imaging processes, image data for two screens each captured under the light pattern whose phase is changed in two ways is acquired.

  Here, a specific example will be described. For example, the printed circuit board 2 illustrated in FIG. 7 has a relatively small size corresponding to a relatively small land (not shown) on which electronic components such as BGA, SOP, and QFP, which are predetermined determination conditions, are mounted. Cream solder Js is printed, and cream solder Jb having a relatively large size is printed corresponding to a relatively large land (not shown) on which electronic components such as resistors, capacitors, and transistors are mounted.

  Therefore, in the printed circuit board 2, the inspection area W1 including only the relatively small cream solder Js satisfying the predetermined determination condition, the relatively small cream solder Js satisfying the determination condition, and the determination condition. With respect to the inspection area W2 including the relatively large cream solder Jb that does not satisfy the above, image data is acquired by the four-time imaging method. On the other hand, the inspection areas W3 and W4 that do not include the relatively small cream solder Js that satisfies the determination condition and include only the relatively large cream solder Jb that does not satisfy the determination condition are imaged by the two-time imaging method. Data is acquired.

  In step S104, the control device 6 performs three-dimensional measurement (height measurement) by the phase shift method based on the image data acquired in step S102 or step S103.

First, a case where four types of image data are acquired in step S102 will be described. The control device 6 calculates the phase θ _{1 of the} light pattern associated with each pixel from the above four image data (the luminance value of each pixel) by the phase shift method.

Here, the luminance values V ₁₀ , V ₁₁ , V ₁₂ , and V ₁₃ relating to the respective pixels of the four types of image data are represented by the following formulas (H1 ′), (H2 ′), (H3 ′), and (H4 ′). Can be represented by

When the above equations (H1 ′), (H2 ′), (H3 ′), and (H4 ′) are solved for the phase θ ₁ , the following equation (H11) can be derived.

Subsequently, the control device 6 compares the phase θ _{1 of} each pixel calculated as described above with the calibration data (phase of each pixel based on calibration) stored in the setting data storage device 26. The amount of displacement of pixels having the same phase is calculated, and based on the principle of triangulation, height data (z) relating to each pixel (x, y) in the inspection area is calculated, and the height data (z) Is stored in the calculation result storage device 25.

  For example, when the measured value (phase) at the pixel to be measured (x, y) is “10 °”, the position where the value of “10 °” is on the data stored by calibration is detected. To do. Here, if “10 °” exists adjacent to the pixel to be measured (x, y) by three pixels, it means that the stripe of the light pattern has shifted by three pixels. Based on the principle of triangulation, the height data (z) of the pixel to be measured (x, y) can be obtained based on the irradiation angle of the light pattern and the amount of deviation of the stripe of the light pattern.

Next, a case where two types of image data are acquired in step S103 will be described. The control device 6 uses the phase shift method to store the two types of image data (the luminance value of each pixel), the calibration data stored in the setting data storage device 26 (the proportional constant K of each pixel based on the calibration), and the like. Is used to calculate the phase θ _{2 of the} light pattern associated with each pixel.

Here, when the luminance values V ₂₀ and V ₂₁ relating to each pixel of the above _two types of image data are used, the phase θ _{2 of the} light pattern relating to each pixel is expressed by the following equation (H12) based on the above equation (15). Can be represented by

θ ₂ = sin ⁻¹ [(V ₂₀ −V ₂₁ ) / K (V ₂₀ + V ₂₁ )] (H12)
However, K: proportionality constant.

Subsequently, the control device 6 compares the phase θ _{2 of} each pixel calculated in this way with the calibration data (phase of each pixel based on calibration) stored in the setting data storage device 26 as described above. Then, the shift amount of the pixels having the same phase is calculated, the height data (z) relating to each pixel (x, y) of the inspection area is calculated based on the principle of triangulation, and the height data ( z) is stored in the calculation result storage device 25.

  Next, in Step S105, the control device 6 performs cream solder quality determination processing based on the three-dimensional measurement result (height data at each coordinate) in Step S104. Specifically, the control device 6 detects the cream solder printing range higher than the reference surface based on the measurement result of the inspection area obtained as described above, and the height of each part within this range. Is integrated to calculate the amount of cream solder printed.

  Subsequently, the control device 6 compares the data such as the position, area, height or amount of the cream solder thus obtained with reference data (gerber data or the like) stored in the setting data storage device 26 in advance. Judgment is made, and whether or not the printing state of the cream solder in the inspection area is good or bad is determined depending on whether or not the comparison result is within an allowable range.

  While such processing is being performed, the control device 6 drives and controls the motors 15 and 16 to move the printed circuit board 2 to the next inspection area. Thereafter, the above series of processing is performed in all inspection areas. By being repeatedly performed, the inspection of the entire printed circuit board 2 is completed.

  As described above in detail, according to the present embodiment, image data is acquired by the four-time imaging method for the inspection area including cream solder that satisfies a predetermined determination condition (for example, the size is less than a predetermined value) with high accuracy. On the other hand, three-dimensional measurement can be executed in a short time by acquiring image data by the two-time imaging method for other inspection areas.

  As a result, when performing three-dimensional measurement using the phase shift method, the measurement speed is improved while maintaining the measurement accuracy required for cream solder (cream solder that requires high-accuracy measurement) that satisfies the predetermined criteria. Can be achieved.

  In the present embodiment, for an inspection area that does not include cream solder satisfying a predetermined determination condition, a relationship between a gain A and an offset B determined by a predetermined imaging condition [for example, A = K (proportional constant) × B], A value of gain A (x, y) or offset B (x, y) relating to the pixel (x, y) determined from the luminance value V (x, y) of each pixel (x, y) on the image data; Is used to measure the height by the phase shift method based on the image data acquired by the twice imaging method.

  Thereby, it is possible to further shorten the time required until all the imaging processes (final imaging process) related to the predetermined inspection area are completed. As shown in FIG. 8C, in the case of the two-time imaging method, the time required to finish all the imaging processes related to a predetermined inspection area is [time required for imaging process [10 ms] × 2 times]. + [Time required for switching process of liquid crystal lattice 4b [20 ms] × 1 time] = total [40 msec].

[Second Embodiment]
Hereinafter, the second embodiment will be described with reference to the drawings. In addition, about the same component as 1st Embodiment, the same code | symbol is attached | subjected and the detailed description is abbreviate | omitted.

  In the first embodiment, the relationship between the gain A and the offset B (proportional constant K) of the light pattern in each pixel is calibrated in advance (four images captured under four light patterns whose phases have been changed). However, instead of this, in the second embodiment, the relationship between the gain A and the offset B (proportional constant K) of the light pattern is separately measured by the two-time imaging method ( In the actual measurement), the image data is obtained on the basis of two kinds of image data respectively captured under the light patterns whose phases are changed in two ways.

  As the procedure, first, the offset B is obtained for all the pixels of the image data using the above equation (12). Next, the luminance value V (= Asin θ + B) of the pixels having the same offset B value is extracted, and a histogram thereof is created. An example is shown in the tables of FIGS. 9 and 10 exemplify a case where the gain A is “1” and the offset B is “0”. FIG. 9 is a distribution table in which the luminance value V is divided into data sections having a width of “0.1” and the number of luminance values included in the data section is represented. FIG. 10 is a histogram in which the luminance values are plotted. .

Based on this histogram, the maximum value V _MAX and the minimum value V _MIN of the luminance value are determined. By using the characteristic of “sin θ”, two peaks generated in the histogram can be determined as the maximum value V _MAX and the minimum value V _MIN of the luminance values, respectively. In the example shown in FIGS. 9 and 10, the number of luminance values V that fall within the data section where the luminance value V is “−1.0 to −0.9” and “0.9 to 1.0” is “51”, respectively. Here are two peaks.

Subsequently, the gain A and the offset B are calculated based on the maximum value V _MAX and the minimum value V _MIN of the luminance values. As described above, the average value of the maximum value V _MAX and the minimum value V _MIN of the luminance value is the offset B, and the half of the difference between the maximum value V _MAX and the minimum value V _MIN is the gain A. That is, as shown in FIG. 9, the intermediate value between the two peaks is the offset B, and half of the width of the two peaks is the gain A.

  The proportionality constant K can be determined based on the gain A and the offset B values obtained in this way [see the above formula (3)]. Therefore, the above-described series of processing functions for determining the proportionality constant K constitutes the relationship grasping means in this embodiment.

  According to this embodiment, the same effect as the first embodiment is obtained. Further, the labor of calibration as in the first embodiment can be omitted, and the measurement time can be further shortened.

  In the present embodiment, the proportionality constant K and the like are obtained for all the pixels of the image data based on the two types of image data captured under two types of light patterns that are 180 degrees out of phase. However, the present invention is not limited to this, and for example, the proportional constant K or the like may be obtained based on two types of image data captured under two types of light patterns that are 90 ° out of phase. Further, the proportional constant K or the like may be obtained not in all the pixels of the image data but in a partial range of the image data such as around the pixel to be measured.

  In addition, it is not limited to the description content of the said embodiment, For example, you may implement as follows. Of course, other application examples and modification examples not illustrated below are also possible.

  (A) In the above-described embodiment, the three-dimensional measuring device is embodied as the substrate inspection device 1 that measures the height of the cream solder printed on the printed circuit board 2, but is not limited thereto, for example, printing on the substrate You may embody in the structure which measures the height of other things, such as the solder bump made and the electronic component mounted on the board | substrate.

  (B) In the above embodiment, the grating for converting the light from the light source 4a into a striped light pattern is constituted by the liquid crystal grating 4b, and the phase of the light pattern is shifted by switching this. It has a configuration. For example, the grating member may be transferred by a transfer unit such as a piezo actuator to shift the phase of the light pattern.

  (C) In the above embodiment, for the inspection area including the cream solder satisfying the predetermined determination condition, the third order is based on the four image data captured under the four light patterns whose phases are different by 90 °. The original measurement is performed, and the inspection area not including the cream solder satisfying the determination condition is subjected to the three-dimensional measurement based on the two image data captured under the two light patterns whose phases are different by 180 °. It is configured to do.

  Not limited to this, for example, for an inspection area including cream solder satisfying a predetermined determination condition, three-dimensional measurement is performed based on four image data captured under four light patterns whose phases are different by 90 °. For the inspection area that does not include the cream solder that satisfies the determination condition, the third order is based on the three types of image data captured under three different light patterns whose phases are different by 120 ° (or 90 °). It is good also as a structure which performs original measurement.

  In addition, for an inspection area including cream solder that satisfies a predetermined determination condition, the inspection area is three-dimensional based on three types of image data captured under three different light patterns whose phases are different by 120 ° (or 90 °). For the inspection area that does not include cream solder that meets the above criteria, the measurement is performed on the basis of two types of image data captured under two different light patterns whose phases are different by 180 ° (or 90 °). It is good also as a structure which performs three-dimensional measurement.

  Of course, the phase shift amount is not limited to the various shift amounts exemplified above, and other shift amounts that can be three-dimensionally measured by the phase shift method may be adopted.

  (D) In the above embodiment, the inspection area including the cream solder satisfying the predetermined determination condition is measured three-dimensionally by the four-time imaging method, and the inspection area not including the cream solder satisfying the determination condition is 2 Although the configuration is such that the imaging method is switched in two stages, such as performing three-dimensional measurement by the multiple imaging method, the configuration is not limited to this, and the imaging method may be switched in three steps.

  For example, using the condition setting screen 330 shown in FIG. 11, a specific condition (for example, a high condition in FIG. 11) among predetermined determination conditions (for example, a condition set in the medium accuracy measurement field 331 in FIG. 11) in the inspection area. If cream solder that satisfies the conditions set in the accuracy measurement field 332 is included, four types of image data are acquired by four-time imaging (by irradiating and imaging a light pattern with four phases). If the inspection area contains cream solder that satisfies the determination condition, but does not include cream solder that satisfies the specific condition, the three-time imaging method (irradiates the light pattern with three phases). When three types of image data are acquired by imaging, and cream solder satisfying the determination condition is not included in the inspection area, the two-time imaging method (light in two phases) is used. By imaging irradiated turn) may obtain the image data of the two ways.

For example, here is set to be "" volume "is" 2 mm ³ "less than" is the "determination condition", if you set the "" volume "is" 1 mm ³ "less than" is as "specific condition" If the inspection area contains cream solder with “volume” of less than “1 mm ³ ”, image data is acquired by the four-time imaging method, and “volume” is “2 mm in the inspection area. ^If cream solder satisfying “less than ³ ” is included, but cream solder satisfying “less than“ 1 mm ³ ”” is included, image data is acquired by the three-time imaging method, If the inspection area does not include cream solder satisfying “volume” of less than “2 mm ³ ”, the image data is acquired by the two-time imaging method.

  (E) In the above embodiment, an inspection area (for example, FIG. 7) including both cream solder that satisfies the determination condition (for example, cream solder Js in FIG. 7) and cream solder that does not satisfy the determination condition (for example, cream solder Jb in FIG. 7). 7 inspection area W2), when four types of image data captured under four different light patterns having different phases are acquired, both cream solders in the inspection area (for example, cream solder Js in FIG. 7). , Jb) are configured to perform three-dimensional measurement based on four types of image data.

  For example, an inspection area (for example, cream solder Js in FIG. 7) that includes both cream solder that satisfies the determination condition (for example, cream solder Js in FIG. 7) and cream solder that does not satisfy the determination condition (for example, cream solder Jb in FIG. 7). For the inspection area W2), when four types of image data respectively captured under four light patterns with different phases are acquired, cream solder that satisfies the determination condition in the inspection area (for example, cream solder in FIG. 7) For Js), three-dimensional measurement is performed based on the four types of image data, and for the cream solder that does not satisfy the determination condition in the inspection area (for example, cream solder Jb in FIG. 7), the four types of captured images are taken. A configuration in which three-dimensional measurement is performed based on two or three types of image data among the data may be employed.

  According to such a configuration, three-dimensional measurement can be performed in a short time based on less image data for cream solder that does not satisfy the predetermined determination condition (cream solder that does not require much measurement accuracy). As a result, the measurement speed can be further improved.

  In addition, when four types of image data are acquired, the measurement accuracy for “a cream solder that does not satisfy a predetermined determination condition (for example, cream solder Jb in FIG. 7)” and two types acquired by two or three imaging methods. Alternatively, the measurement accuracy for “a cream solder that does not satisfy a predetermined determination condition (for example, cream solder Jb in FIG. 7)” when three-dimensional measurement is performed based on three types of image data can be made equivalent.

  Of course, an inspection area (for example, inspection area W2 in FIG. 7) that includes both cream solder that satisfies the determination condition (for example, cream solder Js in FIG. 7) and cream solder that does not satisfy the determination condition (for example, cream solder Jb in FIG. 7). The same configuration can be obtained when three types of image data captured under three types of light patterns having different phases are acquired.

In addition, when four types of image data are acquired by the four-time imaging method under the configuration in which the imaging method exemplified in (d) is switched to three stages, a specific condition in the examination area (for example, ““ volume ”is“ For cream solder satisfying “less than 1 mm ³ ” ”, three-dimensional measurement is performed by the phase shift method based on the four kinds of image data, and the specific condition in the inspection area is not satisfied and the determination condition (for example,“ “volume”) For cream solder satisfying “less than“ 2 mm ³ ””), the three-dimensional measurement is performed by the phase shift method based on three kinds of image data among the obtained four kinds of image data, and the determination condition in the inspection area is determined. For cream solder that does not satisfy the above, three-dimensional measurement is performed by the phase shift method based on two of the acquired four types of image data. When three types of image data are acquired by the imaging method, the cream solder satisfying the determination condition in the inspection area is subjected to a three-dimensional measurement by the phase shift method based on the three types of image data, and in the inspection area. The cream solder that does not satisfy the determination condition may be configured to perform three-dimensional measurement by a phase shift method based on two types of acquired image data.

  (F) In the above embodiment, the determination condition is set via the condition setting screen 230, but the configuration of the condition setting means is not limited to this.

  For example, the determination condition may be set via the condition setting screen 350 shown in FIG. On the condition setting screen 350, the volume value of the cream solder as the determination condition can be changed by sliding the slide bar 351 to the left and right. The slide bar 351 is an image simulating a slide bar displayed on the display device 23 and can be operated via a touch panel.

  Here, for the inspection area including the cream solder having a volume less than a predetermined value set by operating the slide bar 351, three-dimensional measurement is performed by the four-time imaging method, and the cream solder having a volume less than the predetermined value is not included. For the inspection area, three-dimensional measurement is performed by the two-time imaging method.

  In FIG. 12, for example, when the slide bar 351 is moved to the right end, the volume value of the cream solder as the determination condition becomes the maximum value. That is, all cream solder on the printed circuit board 2 satisfies the determination condition, and three-dimensional measurement is performed by the four-time imaging method for all inspection areas. On the other hand, when the slide bar 351 is moved to the left end, the volume value of the cream solder as the determination condition becomes the minimum value. That is, all cream solders on the printed circuit board 2 do not satisfy the determination condition, and three-dimensional measurement is performed by the imaging method twice for all inspection areas.

  Further, the condition setting screen 350 displays a scheduled time display unit 352 (scheduled time) that can display a scheduled time required for measurement of the printed circuit board 2 under a determination condition (predetermined volume value) set by operating the slide bar 351. Display means) is provided. The scheduled time displayed here is calculated based on the determination condition set by operating the slide bar 351 and the Gerber data.

  For example, in the example shown in FIG. 8, the time required to finish all the imaging processes related to one inspection area is 100 msec (0.100 sec) in the case of the four-time imaging method, and in the case of the two-time imaging method. Is 40 msec (0.040 sec).

  Accordingly, if the number of inspection areas set on the printed circuit board 2 is N, the time required to acquire the image data of the entire range of one printed circuit board 2 is four times for all the inspection areas. When the image data is acquired by the above, 100 × N (msec) is obtained. On the other hand, in the case where image data is acquired by the two-time imaging method for all inspection areas, 40 × N (msec).

  In addition, the number of inspection areas including cream solder having a volume less than a predetermined value set by operating the slide bar 351 is N1, and the number of inspection areas not including cream solder having a volume less than the predetermined value is N2. In the case of (number), the time required to acquire the image data of the entire range of one printed circuit board 2 is 100 × N1 (msec) + 40 × N2 (msec).

  Furthermore, it is good also as a structure which displays on the scheduled time display part 352 as scheduled time including the movement time which drives the motors 15 and 16 and moves the printed circuit board 2 from a predetermined | prescribed inspection area to the next inspection area.

(G) In the above-described embodiment, the two-time imaging method is configured to perform three-dimensional measurement based on two types of image data captured under two types of light patterns that are 180 degrees out of phase. Instead of this, for example, a configuration may be adopted in which three-dimensional measurement is performed based on two types of image data captured under two types of light patterns whose phases differ by 90 °. In such a case, by using the above formulas (23) and (27), the luminance values V ₂₀ and V ₂₁ at each pixel on the two kinds of image data and the known proportionality constant K are used, and the light at each pixel. The phase θ ₂ of the pattern can be calculated.

According to such a configuration, since the phase θ ₂ can be obtained based on an arithmetic expression using “tan ⁻¹ ”, the height can be measured in a range of 360 ° from −180 ° to 180 °. Can be larger.

Of course, other configurations may be adopted as long as the relationship of the above formulas (1), (2), and (3) is satisfied. An example of the general formula for obtaining the phase θ ₂ is the above formula (9) [see [Equation 9]].

  DESCRIPTION OF SYMBOLS 1 ... Board | substrate inspection apparatus, 2 ... Printed circuit board, 4 ... Illuminating device, 4a ... Light source, 4b ... Liquid crystal lattice, 5 ... Camera, 6 ... Control apparatus, 23 ... Display apparatus, 24 ... Image data storage means, 25 ... Calculation result Storage device, 26: Setting data storage device, 230: Condition setting screen, A ... Gain, B ... Offset, K ... Proportional constant, Js, Jb ... Cream solder, W1-W4 ... Inspection area.

Claims (6)

Irradiation means capable of irradiating an object to be measured with a light pattern having a striped light intensity distribution;
Imaging means capable of imaging a predetermined measurement area on the object to be measured irradiated with the light pattern;
The irradiation unit and the imaging unit are controlled, the phase of the light pattern is changed in a plurality of ways, and a plurality of images related to the measurement region captured under each light pattern can be acquired. Image acquisition means capable of changing the number of images to be acquired for the measurement region according to the measurement region;
Based on the image acquired by the image acquisition means, the image processing means capable of performing three-dimensional measurement on the measurement target in the measurement region by the phase shift method,
The image acquisition means includes
When the measurement target satisfying a predetermined determination condition is included in the measurement region, the first predetermined number of images captured by irradiating the light pattern with the first predetermined number of phases are acquired,
When the measurement target that satisfies the determination condition is not included in the measurement region, the second predetermined number obtained by irradiating and imaging a light pattern with a second predetermined number of phases smaller than the first predetermined number A three-dimensional measuring apparatus characterized by acquiring a street image. In the case where the image acquisition means acquires the first predetermined number of images,
The image processing means includes
For the measurement target that satisfies the determination condition in the measurement region, based on the first predetermined number of images, three-dimensional measurement is performed by a phase shift method,
The three-dimensional measurement according to claim 1, wherein a three-dimensional measurement is performed by a phase shift method based on the second predetermined number of images for a measurement target that does not satisfy the determination condition in the measurement region. Measuring device.   The three-dimensional measuring apparatus according to claim 1, further comprising condition setting means capable of setting the determination condition based on an external operation.   The three-dimensional measuring apparatus according to claim 3, further comprising a scheduled time display unit capable of displaying a scheduled time for measuring the measurement object under the determination condition set by the condition setting unit. . The image acquisition means includes
When the measurement target satisfying the determination condition is included in the measurement region, the first predetermined number of four or three types of images obtained by irradiating a light pattern with three or three phases are imaged. Get an image,
When the measurement target that satisfies the determination condition is not included in the measurement area, two images obtained by irradiating a light pattern with two phases as the second predetermined number are acquired. The three-dimensional measuring apparatus according to claim 1, wherein the three-dimensional measuring apparatus is characterized.   The measurement object is a cream solder printed on a printed circuit board as the object to be measured, or a solder bump formed on a wafer substrate as the object to be measured. The three-dimensional measuring apparatus according to any one of 5.

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