JP3186308B2 - Method and apparatus for monitoring sintering state of ceramic substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for monitoring a sintering state at the time of manufacturing a ceramic substrate such as an electronic circuit.

[0002]

2. Description of the Related Art A ceramic substrate is made by printing a metal particle and a small amount of a glass component on a base material made of ceramic powder or glass, forming a pattern, and then sintering at a high temperature. At this time, the glass contained in the base portion in the pattern portion also soaks, but the amount of the soaking varies depending on the sintering conditions. Therefore, the sintering conditions are monitored by monitoring the amount of the soaking of the glass. can do.

Conventionally, the measurement of the amount of glass has been performed by visually observing the surface with a microscope or the like.

[0004]

As described above, conventionally,
Since the measurement of the amount of glass was carried out visually, there were variations due to the conditions at the time of work and individual differences.Therefore, it was not possible to statistically monitor fluctuations in the sintering state, and errors in the control of process conditions in the next step caused errors. There were many problems such as increase.

An object of the present invention is to provide a means for measuring the amount of glass in a ceramic substrate pattern portion after sintering, and a means for quantitatively monitoring the sintering state of a ceramic substrate.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for polishing a surface of a substrate after sintering, aligning the directions of metal surfaces exposed on the surface substantially uniformly, and adjusting the surface of the metal surface. Processing two images: an image illuminated / detected from the line direction and an image illuminated with polarized light oscillating only in a specific direction, and only light oscillating in the direction orthogonal to the oscillating direction of the illumination is detected Then, by quantifying the distribution region of the metal in the pattern portion, the amount of glass in the pattern portion was quantified, and the sintering state of the ceramic substrate could be monitored quantitatively.

[0007]

[Function] The reflectance of visible light in the normal direction of the object surface is
Generally, glass is 4%, whereas metal is 60% or more. Therefore, metal is detected brighter than glass. Further, in the reflection of light on the surface of the object, the angle of incidence and the angle of reflection with respect to the surface normal are equal, and in other directions, the amount of reflected light is extremely reduced. For this reason, after sintering, if the ceramic substrate in which the direction of the metal surface exposed on the surface is substantially uniformly adjusted by polishing the surface is illuminated / detected from the normal direction of the surface, the pattern portion is The surface where the metal is exposed is detected as bright with a certain probability, and the other portions are detected as dark.

In general, in the reflection of light on the surface of an object, the polarization of the light incident / specularly reflected in the normal direction of the surface is not disturbed (the vibration direction does not change). The polarization direction is the same as the illumination light. Therefore, if the detection side detects only the polarized light orthogonal to the polarization direction of the illumination light, the specularly reflected light is not detected, and that portion is detected as dark, so that the entire pattern portion is detected as dark. Hereinafter, this illumination / detection method is referred to as polarization detection.

[0009] From the above, the illumination /
The place where it is detected brightly in the detected image and darkly detected in the polarization detection image is a metal.

Further, since the swelling of the glass occurs from the periphery to the center of the pattern, the distribution area of the metal becomes narrower as the amount of glass increases. Therefore, the amount of the glass is determined by calculating the distribution area of the metal. And the sintering state of the ceramic substrate can be monitored quantitatively.

[0011]

An embodiment of the present invention will be described below. First,
The whole of the present invention will be described, and then an embodiment for measuring the amount of glass in the pattern portion of the ceramic substrate will be described.

FIG. 1 is a flowchart for explaining one embodiment of monitoring the sintering state. In FIG. 1, a ceramic substrate prepared in a previous step is sintered in a sintering step. The metal surface exposed on the surface of the pattern portion of the sintered ceramic substrate is oriented in various directions as in the cross-sectional example shown in FIG. For this reason, even if it is illuminated / detected from a certain direction, it is hardly detected. For example, when the illumination light 105 is illuminated from above the sample in FIG. 2A, most of the reflected light is reflected in a direction different from the illumination direction like the reflected light 106, and the direction is various. Then, the surface of the ceramic substrate is polished to make the direction of the metal surface exposed on the surface almost uniform, and if the same detection is performed, the reflected light from most of the metal portion is generated as shown in FIG. Can be detected. Utilizing this, the amount of glass is quantified by a method described later in detail, and glass amount information 46 is obtained. The glass amount information 46 is used as quantitative sintering state information of the sintering step, and is fed back to the process conditions of the sintering step or used for determining the process conditions of the next step.

According to this embodiment, the sintering state can be quantitatively grasped, which can be used for improving the yield of substrate manufacturing and ensuring reliability.

Next, an embodiment for measuring the amount of glass in the pattern portion of the ceramic substrate will be described. FIG. 3 is a diagram showing an overall configuration of one embodiment for measuring the amount of glass in a pattern portion of a ceramic substrate. In FIG. 3, reference numeral 1 denotes a sample (ceramic substrate) as an object to be measured. 2 is sample 1
This is a stage for moving. Reference numeral 3 denotes an illumination light source for illuminating the sample 1. Although the light source is mounted as it is in the figure, the light source may be separated and guided by a light guide or the like. Reference numeral 4 denotes a sensor for detecting the surface of the sample 1. Here, a TV camera which is a two-dimensional sensor will be described as an example. Reference numeral 5 denotes a polarizer for turning the illumination light 25, which is natural light, into polarized light that vibrates in only one specific direction.
In and out of the optical path. That is, when the polarizer 5 is put in the optical path of the illumination light 25, the illumination light 26 becomes
Light that oscillates only in one specific direction, that is, polarized light,
When the polarizer 5 is emitted from the optical path, the illumination light 26 becomes natural light.
Reference numeral 6 denotes an analyzer for passing only the light oscillating in one specific direction of the detection light 27. The analyzer 6 can be moved into and out of the optical path of the detection light 27 by a suitable moving device (not shown). is there. Here, the analyzer 6 is mounted in a direction that passes only light that vibrates in a direction orthogonal to the vibration direction of the illumination light 26. 7 is an image signal 20 obtained by the sensor 4
As shown in FIG. 4, the image processing unit generates an input control signal 21 for controlling the sensor 4, the A / D converter 31, and the like, and outputs an image signal 20 which is an output of the sensor 4. An A / D converter 31 for converting a digital value according to the input control signal 21; a shading correction unit 32 for correcting shading of the obtained image signal 40; and a binarization unit 33 for binarizing the image signal 41
, A memory 34 for temporarily storing the binarized image signal 42, and a microprocessor 35. 8
Is an overall control unit that controls the entire system, and includes a microprocessor, a sequencer, and the like. Of course, it may be configured by hard wired logic. Reference numeral 9 denotes a stage control unit for controlling the stage 2, which moves the stage 2 according to a command 23 of the overall control unit 8. Reference numeral 10 denotes a lens group for illumination / detection. Illumination light is illuminated on the surface of the sample 1 by the lens groups 10a and 10b.
Images are formed on the sensor 4 by b and 10c. Reference numeral 11 denotes a half mirror for performing illumination and detection coaxially. The half mirror 11 reflects the illumination light 26 in the direction of the sample 1 and transmits the reflected light from the sample to obtain the detection light 27. Here, 10a,
Three lens groups 10b and 10c and half mirror 1
1 constitutes an illumination / detection system, but the configuration does not matter as long as the two images can be detected.

Next, the operation of this embodiment will be described.

In this embodiment, first, the stage is moved to a position where the amount of glass is to be measured, and then an image of one frame of the TV camera as the sensor 4 is taken under the control of the input control 30, and the image signal 20 is taken. Get. Image signal 20
Is converted into a digital value by the A / D converter 31 for each pixel of the linear sensor and becomes an image signal 40. The shading correction circuit 32 corrects the shading (non-uniformity of the detected light due to non-uniformity of illumination and non-uniformity of the sensitivity of the sensor) of the image signal 40 to become an image signal 41. The shading correction circuit 32 includes, for example, JP-A-58-153.
No. 328, an image sensor non-uniformity correction method can be used. The image signal 41 is binarized by a binarization circuit 33 for setting the brightness at a certain threshold value or higher to "1", and the obtained binary image signal 42 is stored in an image memory of the memory 34.

Here, the obtained image will be described with reference to FIG. In FIG. 5, the "1" portion is represented by black or oblique lines. Further, 101a and 101b are patterns, and 102 is ceramic as a base material.

FIG. 5A shows an example of a binary image when the polarizer 5 is taken out of the illumination optical path 25, the illumination light 26 is used as natural light, and the analyzer 6 is also emitted from the detection-side optical path 27 and detected.
When detected in this way, the metal part in the pattern 101 is detected bright (black in FIG. 5A). FIG.
As shown in (a), the ceramic part 102 may be detected as bright.

FIG. 5B shows the same location as the imaging location in FIG.
6 is light that oscillates in only one specific direction, that is, polarized light, and the analyzer 6 is also placed in the detection-side optical path 27 so that only the detection light orthogonal to the oscillation direction of the illumination light is detected. It is an example. When such detection is performed, the glass portion in the pattern portion 101 is detected dark (white in FIG. 5B) because of its low reflectance. Further, since the plane of polarization does not change due to specular reflection at the metal part, the reflected light cannot be transmitted through the analyzer 6 and is detected dark. On the other hand, in the ceramic part 102, the illumination light 26 is diffused from the ceramic surface to the inside, so that the polarized light is disturbed and the light vibrates in various directions, and the light in the direction that can pass through the analyzer 6 is detected as the detection light 28. You. For this reason, the pattern portion 10
An image in which 1 is dark (white in FIG. 5B) and the ceramic portion 102 is bright (black or oblique lines in FIG. 5B) is detected.

The two images obtained by these two illumination / detection methods are stored at different addresses in the memory 34. The microprocessor 35 reads and processes the two images, and outputs glass amount information 46. Hereinafter, one embodiment of the processing will be described with reference to FIGS.

FIG. 6 shows an embodiment of the image processing by the microprocessor 35. 43a is a binary image signal when both the polarizer 5 and the analyzer 6 shown in FIG. 5 (a) are detected out of the optical path, and 43b is a polarizer shown in FIG. 5 (b). 5, the analyzer 6 is a binary image signal when detected in the optical path. First, a logical NOT 43c of the image signal 43b is obtained, and a logical AND with the image signal 43a is obtained.
An image signal 44a shown in FIG. here"
Only the metal portion 103 inside the pattern becomes 1 ". On the other hand, labeling is performed on the image signal 43c,
As shown in FIG. 7B, the individual patterns 101a, 101a
Extract 1b . FIG. 7B shows an image signal 44b as a result of the labeling, in which pixels of "0" are shown in white, pixels of "1" are shown in oblique lines, and pixels of "2" are shown in black. Next, as shown in FIG. 7C, windows 111a and 111b surrounding each pattern are generated. Window 1
11a and 111b are superimposed on the image signal 44a, and the smallest convex polygon (hereinafter referred to as convex hull) including all the metal parts 103 in each window is detected. Detection of the convex hull, for example information processing Letters, Buioeru 1 (1972) 133, pages from the 132 pages (Info r mation Processing Letters, Vol.1 (197
2), pp. 132-133), is performed by the following method called Graham's method.

First, the upper left pixel of the window is set as a starting point, and scanning is performed to the right. If the pixel is located at the right end of the window or hits a pixel of "1", the starting point is moved down by one pixel. When the pixel hits “1”, the coordinates are stored. This is repeated until the start point is the lower left pixel of the window, and the coordinates corresponding to the pixel “1” are sequentially stored. Next, starting from the lower right pixel of the window and scanning toward the left, it becomes the leftmost pixel of the window, or
If it hits the pixel of 1 ", the starting point is moved up by one pixel. If it hits the pixel of" 1 ", its coordinates are stored.This is repeated until the starting point becomes the upper right pixel of the window, and" 1 " In this way, a set of coordinates P is obtained as shown in Fig. 8A.Points included in the set P are candidate points of the vertices of the convex hull. When these are processed according to the flow shown in Fig. 9, a set Q of remaining points as shown in Fig. 8B is a vertex of the convex hull.

From the set Q, the area 45a of the convex hull is

[0024]

(Equation 1)

[0025]

On the other hand, by counting the number of "1" or the number of "2" from the image signal 44b, the individual area 45b of the pattern 101a or 101b can be obtained. By dividing 45a by 45b, the ratio of the distribution area of the metal portion to the pattern area is determined, and this is output as glass amount information 46.

Alternatively, the contour of the pattern 101 may be determined, the maximum value of the distance between the vertices of the convex hull from the contour may be determined, and this may be used as the glass amount information 46. Further, these two may be combined to obtain the glass amount information 46.

In this embodiment, a part of the image processing unit 7 is constituted by hardware, and a part is constituted by a microprocessor. However, the constitution is not limited as long as the image processing can be performed.

In this embodiment, since the detection is performed by one sensor, there is no need to perform a process such as alignment or magnification conversion between two images captured under two types of illumination / detection conditions. There is.

In this embodiment, the polarizer 5 and the analyzer 6 are moved and detected by one detection head in order to obtain two image detection conditions. However, separate detection heads may be used.

In this embodiment, polarization detection is performed to obtain the shape of the pattern portion 101. However, design data may be prepared in advance, or data detected before may be used. In this case, the number of detections can be reduced by one, and the measurement can be speeded up.

In this embodiment, a two-dimensional sensor is used as the sensor 4. However, a one-dimensional sensor such as a linear sensor is used to synchronize the stage 2 with the operation of the sensor.
Detection may be performed by continuous movement. In this case, there is an effect that the start / stop time of the stage can be reduced, and the detection time can be shortened.

Further, in this embodiment, since the detected image is processed after being binarized, the processing circuit can be reduced in scale.

[0034]

According to the present invention, the sintering state of the ceramic substrate can be quantitatively monitored by obtaining the quantified information of the glass amount of the ceramic substrate pattern portion after sintering.

[Brief description of the drawings]

FIG. 1 is an overall flowchart of the present invention.

FIG. 2 is a sectional view of a sample.

FIG. 3 is an overall configuration diagram of one embodiment for measuring the amount of glass in a pattern portion of a ceramic substrate.

FIG. 4 is a block diagram showing one embodiment of an image processing unit 7 in FIG. 3;

FIG. 5 is a flowchart of image processing by a microprocessor 35 in FIG. 4;

FIG. 6 is a diagram illustrating an example of an image of each unit in FIG. 4;

FIG. 7 is a diagram illustrating an example of an image of each unit in FIG. 6;

FIG. 8 is a diagram illustrating convex hull detection.

FIG. 9 is a diagram showing a flow of convex hull detection.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... sample (ceramic substrate), 2 ... stage, 3 ... light source of illumination, 4 ... sensor, 5 ... polarizer, 6 ... analyzer, 7 ... image processing part, 8 ... whole control part, 9 ... stage control part, 10
(10a, 10b, 10c): lens group, 11: half mirror, 25, 26: illumination optical path, 27, 28: detection optical path, 30: input control unit, 31: A / D converter, 32
.., Shading correction unit, 33, binarization unit, 34, memory unit, 35, microprocessor, 101 (101a, 101a,
101b): ceramic substrate pattern portion, 102: base material portion (ceramic portion), 103: metal portion, 104: glass portion.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Mineo Nomoto 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. Hitachi, Ltd. Production Engineering Laboratory (56) References JP-A-1-263540 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/84-21/958 H05K 3/46

Claims (4)

(57) [Claims] 1. A ceramic substrate after sintering is polished, the directions of metal surfaces exposed on the surface are almost uniformly aligned, and an image A illuminated / detected from a normal direction of those surfaces and a specific direction are obtained. 2 of the image B obtained by illuminating only polarized light oscillating and detecting only light oscillating in the direction orthogonal to the oscillation direction of the illumination light.
A method for monitoring the sintering state of a ceramic substrate, comprising obtaining two images, detecting the amount of glass from the two images by image processing, and using the detected amount as monitoring information for the sintering state of the ceramic substrate. 2. The method according to claim 1, wherein a portion detected as bright in the image A and a portion detected dark in the image B is a metal portion, a portion detected dark in the image B is a pattern portion, and Characterized in that the area of the convex hull including the following is expressed as a ratio to the area of the pattern. 3. The amount of glass according to claim 1, wherein a portion detected brightly in the image A and darkly detected in the image B is a metal portion, a portion detected dark in the image B is a pattern portion, Characterized by the maximum value of the distance between the convex hull and the boundary of the pattern portion including the following. 4. A means for polishing a ceramic substrate after sintering so as to make the directions of metal surfaces exposed on the surface almost uniform, a means for obtaining an image A illuminated / detected from the normal direction of those surfaces, A means for illuminating polarized light oscillating only in a specific direction and obtaining an image B in which only light oscillating in a direction orthogonal to the oscillation direction of the illumination light is obtained; An apparatus for monitoring a sintering state of a ceramic substrate, comprising an image processing means for detecting.