JPH0694651A - Substrate inspector - Google Patents

Abstract

PURPOSE:To obtain a reconfigured image with less picture quality deterioration by reducing a part where an X-ray source and a rotary substrate are crossing by moving the substrate and then generating the reconfigured screen by compensating an obtained data so that an enlargement rate is aligned. CONSTITUTION:The X rays from an X-ray source 22 are applied to a substrate 26 and the images of transmitted projection data are received by a camera 28 via a fluorescent plate 23 and an image-forming lens 27. The obtained projection data are A/D converted 32 and stored at a frame memory 33 and the line-shaped data through a reconfiguration section are extracted as projection data and are stored in a projection data memory 34. On the other hand, in a dropout part with a rotary angle where the substrate 26 and the X-ray source 22 are crossing, the substrate 26 is moved to the side of the fluorescent plate 23 for reducing it. The distance at this time is detected by an encoder 40 and stored and then is used for calculating the expansion rate of an image processing unit 37. With the projection data which are obtained by reduction along with the move of the substrate 26, the expansion rate is aligned by the unit 37 and stored in the projection data memory 34 as the data of the dropout part. After the projection data over a half periphery or an entire periphery is collected, reconfiguration calculation is made by the image processing unit 37 before displaying at a display 36 as a reconfiguration image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate inspection apparatus for observing a cross section of a substrate using X-rays.

In recent years, in the manufacture of mounting boards and printed circuit boards, miniaturization of electronic parts and high-density mounting have been advanced, and along with this, miniaturization of connection parts such as solder has also progressed. As the amount of solder used decreases, the reliability test is not enough to inspect only from the appearance and defects, and the quality such as the presence or absence of voids inside the solder, the presence of cracks, and the gap between the chip and the board It is necessary to inspect the bump shape of the connection part. An inspection method using X-rays is an effective method for inspecting such a portion.

Especially when observing the inside, CT (Comput
The method using ed tomography) enables cross-sectional observation, and it is desired to capture images with high accuracy.

[0004]

2. Description of the Related Art FIG. 4 is a block diagram of a conventional board inspection apparatus. The substrate inspection apparatus 11 in FIG. 4 is a CT apparatus using X-ray II (image intensifier), and a substrate 13 as a sample is mounted on a holder 12a of a rotary stage 12 for inspection.

The substrate 13 is irradiated with X-rays from an X-ray source 14, and the transmitted X-rays are incident on X-rays II15. The X-ray source 14 is a micro focus with a focal dimension of several μm or less. Further, the X-ray II15 is briefly described. The light converted from the incident X-ray by the fluorescent screen is converted into an electron by the photoelectric member, and the electron beam generated by accelerating the electron by the electrode is output to the fluorescent screen. The image projected onto the output phosphor screen is received by the camera. Since this X-ray II15 has a large incident surface and high sensitivity, a magnified image can be obtained.

The board inspection apparatus 11 as described above is provided with a board 13
While rotating the rotary stage 12 mounted with a predetermined angle, the projection data is collected on the X-ray II 15 and, although not shown, image reconstruction is performed.

FIG. 5 shows a diagram for explaining the projection data of FIG. FIG. 5 shows the data collection of the X-ray attenuation amount for every 120 degrees on the substrate 13, for example.

Therefore, FIG. 6 shows a diagram for explaining the magnifying optical system of FIG. In FIG. 6, the sample is the substrate 1.
When detecting a microscopic portion such as the bump of No. 3, X-ray I
It is desirable to project the image on the sensor surface 15a of I15 with the maximum magnification. Therefore, from the X-ray source 14 to the sensor surface 15a
The distance D from the X-ray source 14 to the substrate 13 must be made as small as possible with respect to the distance L. In this case, the enlargement ratio M to the sensor surface 15a is represented by L / D.

[0009]

However, if the substrate 13 is placed too close to the X-ray source 14 in order to increase the magnification, the holder 12a abuts the X-ray source 14 and cannot rotate when rotated.

Here, FIG. 7 shows a diagram for explaining a conventional image loss. As shown in FIG. 7A, the substrate 13
When the holder 12a abuts the X-ray source 14 when is rotated, there is a projection angle Φ at which the X-ray source 14 and the substrate 13 intersect, as shown in FIG. 7B.

That is, there is a problem that projection data at this angle Φ cannot be detected and data is lost, and if image reconstruction is performed in this state, image quality is deteriorated due to data loss in the obtained image.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a substrate inspection apparatus for obtaining a reconstructed image with little deterioration in image quality.

[0013]

The above object is to irradiate a substrate rotated by rotating means with X-rays from an X-ray source, receive enlarged projection data of the substrate by image receiving means, and In a substrate inspection apparatus that generates a reconstructed image, a moving unit that moves the rotating unit from the X-ray source to the image receiving unit to change the enlargement ratio, and the projection unit having different enlargement ratios obtained by the moving unit. Data correction means for generating the reconstructed image by matching the data enlargement rate,
Is solved by having.

[0014]

As described above, the moving means changes the enlargement ratio so that the portion where the X-ray source and the rotated substrate intersect is moved to reduce the image. Further, the projection data of the substrate having different enlargement ratios are made uniform in enlargement ratio by the data correction means. Then, the reconstructed image is generated from the projection data of the substrates with the same enlargement ratio.

As a result, projection data which could not be obtained at the intersection of the X-ray source and the substrate can be obtained.
It is possible to obtain a reconstructed image with little deterioration in image quality.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of an embodiment of the present invention.
In FIG. 1, the substrate inspection apparatus 21 is provided with a linear stage 24 that is a moving unit between the X-ray source 22 and the fluorescent plate 23, and a rotary stage 25 that is a rotating unit is provided on the linear stage 24. As the X-ray source 22, for example, a microfocus X-ray source is used. Rotating stage 25
Is provided with a holder 25a.
The board 26 to be inspected is mounted on a. This board 26
Is a chip having bumps formed thereon, and the state of formation of the bumps is to be inspected.

An image forming lens 2 is provided behind the fluorescent screen 23.
A camera 28 is installed via 7. The camera 28 is composed of, for example, a CCD (charge coupled device) in which pixels are arranged one-dimensionally or two-dimensionally. In the case of a one-dimensional array CCD, the fluorescent plate 23 and the camera 28 may be optically coupled by the taper of the light guide plate. The fluorescent plate 23 and the imaging lens 27
(Or taper) and the camera 28 constitute an image receiving means. X-ray II may be used as the image receiving means.

On the other hand, in the processing circuit, the data bus 31
A for converting the projection data from the camera 28 into digital data
/ D converter 32, frame memory 33 that stores all projection data, projection data memory 34 that stores reconstructed image data, CPU (central processing unit) 35 that performs various controls, display unit 36, coordinate conversion, The image processing unit 3 which is a data correction means for performing configuration calculation, magnification correction, etc.
7 and an input / output (I / O) interface 38 are respectively connected.

The I / O interface 38 has an X
X-ray controller 3 for controlling X-ray dose by the radiation source 22
9, an encoder 40 for detecting the position signals of the rotary stage 25 and the rectilinear stage 24, a stage controller 41 for driving them, and a camera controller 42 for driving the shutter of the camera 28 are connected.

Next, the operation of the board inspection apparatus will be described. First, the substrate 2 is irradiated with X-rays emitted from the X-ray source 22.
The projection data that has been radiated to 6 and transmitted is received by the camera 28 via the fluorescent plate 23 and the imaging lens 27. The obtained projection data is digitized by the A / D converter 32,
After being stored in the frame memory 33, the line-shaped data transmitted through the reconstructed cross section is extracted as projection data and stored in the projection data memory 34.

On the other hand, in the data missing portion of the rotation angle where the substrate 26 and the X-ray source intersect, the substrate 26 is moved to the fluorescent plate 23 side by the rectilinear stage 24 to reduce the size. The moving distance at this time is stored in advance by detection from the encoder 40, and is used for calculation of the enlargement ratio (reduction ratio) in the image processing unit 37.

The projection data obtained by the reduction is made to have the same enlargement ratio in the image processing unit 37 and is stored in the projection data memory 34 as the data of the missing portion.

Then, after the projection data is collected over a half circumference or the entire circumference, reconstruction calculation is performed in the image processing unit 37 and displayed on the display unit 36 as a reconstructed image.

Therefore, FIG. 2 shows a diagram for explaining the process of FIG. 1, and FIG. 3 shows a diagram for explaining the principle of the process of FIG. In FIGS. 2 and 3, first, projection data of the substrate 26 at a normal magnification is obtained. Therefore, the substrate 26
The missing angle of the projection data is calculated from the rotation center position of X, the size of the X-ray source 22, and the thickness of the substrate 26 (see step (S
T) 1), collecting projection data (ST2, FIG. 3)
(A)).

Subsequently, in the projection of the missing angle portion, the enlargement ratio is reduced (ST3) and the missing portion data is collected (ST.
4, FIG. 3 (B)). At this time, the enlargement ratio is obtained from the moving distance of the rectilinear stage 24, and the reduction ratio of the projection data is corrected by calculation to obtain the projection data (ST5, FIG. 3B).

The correction in this case is performed by the formula P ₀ (S) = P
It is calculated based on ₁ (Sx / (x + Δx)). Note that P ₀ (S) is the corrected projection data, P ₁ (S) is the reduced data used in the missing portion, and S is the projection coordinates.

Then, using the obtained projection data, image reconstruction including the missing angle portion shown in FIG. 3C is performed (ST6).

As a result, the deterioration of the resolution of the plane distribution of the substrate 26 necessary for the inspection can be minimized, and the deterioration of the image quality of the reconstructed image due to the missing projection data can be prevented.

Although the above embodiment shows the case where the enlargement ratio correction is performed by the calculation in the image processing unit 37, a zoom optical system is provided in the camera 28, and when the image is reduced, the camera controller 42 serves as a zoom control means.
The same effect can be obtained even when image reconstruction is performed by receiving the projection data that has been zoomed in and zoomed in at the same magnification.

[0030]

As described above, according to the present invention, projection data obtained by reducing the portion where the X-ray source and the substrate intersect with each other by changing the enlargement ratio is corrected so as to make the enlargement ratio uniform. By generating a reconstructed image, it is possible to obtain a reconstructed image with little deterioration in image quality.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram for explaining the process of FIG.

FIG. 3 is a diagram for explaining the principle of the processing of FIG.

FIG. 4 is a configuration diagram of a conventional board inspection device.

FIG. 5 is a diagram for explaining the projection data of FIG.

FIG. 6 is a diagram for explaining the magnifying optical system of FIG.

FIG. 7 is a diagram for explaining a conventional image loss.

[Explanation of symbols]

 21 Substrate Inspection Device 22 X-ray Source 23 Fluorescent Plate 24 Straight Stage 25 Rotating Stage 25a Holder 26 Substrate 27 Imaging Lens 28 Camera 31 Data Bus 33 Frame Memory 34 Projection Data Memory 37 Image Processing Unit 42 Camera Controller

Claims (2)

[Claims] 1. A substrate (26) rotated by a rotating means (25) is irradiated with an X-ray from an X-ray source (22), and enlarged projection data of the substrate (26) is received by an image receiving means (23, 23). Two
In the substrate inspection apparatus for receiving an image by means of an image receiving device (7, 28) and generating a reconstructed image of the substrate (26), the rotating means (25) is connected to the image receiving means (23, 27, 28) from the X-ray source (22). ) And a data correcting means for generating the reconstructed image by aligning the enlargement ratios of the projection data having different enlargement ratios obtained by the moving means (24). (37), and a substrate inspection apparatus comprising: 2. The image receiving means (23, 27, 28) is provided with a zoom optical system, and the data correcting means (37).
2. A zoom control means (42) for driving the zoom optical system to equalize the enlargement ratios.
The board inspection apparatus described.