JP2004317226A - Bump inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bump inspection device constituted so as to enhance the S/N ratio of an X-ray image to stably inspect a bump. <P>SOLUTION: An X-ray emitting device 16 is arranged and fixed under the substrate 2 supported on a substrate support mechanism 10 and a flat panel 20 as an X-ray detector is arranged above the substrate 2 so as to be opposed to the X-ray emitting device 16. The substrate 2 supported on the substrate support mechanism 10 is located at an inspection position by a movement control part 14 and X rays 18 emitted from the X-ray emitting device 16 transmit through the bump 4 of the substrate to be detected by the flat panel 20 and the X-ray image thereof is captured in an image processor 22 to determine the quality of the bump 4 such as the presence of the void of the bump 4 or the like. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for inspecting bumps formed on a substrate, and more particularly to an apparatus for non-destructively inspecting solder bumps formed on a substrate for mounting and mounting a semiconductor chip.
[0002]
[Prior art]
As a substrate to be inspected in the present invention, for example, as shown in FIG. 2, a plurality of solder bumps 4 are arranged and formed on the surface of the substrate 2, and a plurality of pads 6 are formed on the back surface of the substrate 2. It is formed individually. In this substrate, bumps 4 and pads on the back surface are connected by wiring formed in the substrate. On the substrate 2, an IC chip 8 on which a semiconductor device is formed is placed on a solder bump formation area of the substrate 2 with its pad formation surface facing down, and the chip 8 is connected to the substrate 2 by the solder bumps 4 and mounted. Is what is done. Thereafter, terminals are attached to the pads 6 on the back surface of the substrate 2, a case is put on the chip 8, and heat radiating fins are attached to obtain a packaged semiconductor device such as a CPU chip. The substrate to be inspected by the present invention is in a state before the chip 8 is mounted.
[0003]
As a method of inspecting a solder bump, a defect of a bump is detected by irradiating X-rays, detecting X-rays transmitted through the bumps, and performing image processing (for example, Patent Document 1). reference.).
[0004]
In an inspection apparatus using such X-rays, generally, the substrate to be inspected is arranged so that the bumps face upward, an X-ray generator is provided on the lower side, and the X-rays transmitted through the substrate are placed above the substrate. It is arranged so that it may be detected by the provided X-ray detector. This is partly to make the bumps to be inspected visible.
[0005]
In an apparatus in which an X-ray generator is arranged below an object, the object to be inspected is often mounted on a support plate such as a carbon plate to support the object to be inspected. In general, an image tube is used as a detector.
[0006]
As for the X-ray detector, a flat panel is used in medical X-ray CT and the like. The flat panel has features such as low distortion and good resolution, but the flat panel is not generally used in a substrate inspection apparatus or the like. This is because flat panels have a drawback of low sensitivity.
[0007]
[Patent Document 1]
JP 2001-358161 A
[Problems to be solved by the invention]
The configuration of a conventional inspection apparatus in which an inspection object is arranged with bumps facing upward and an X-ray generator is provided below has the following problems.
When the inspection object is supported so that the bumps face upward, at least the thickness of the substrate of the inspection object exists between the X-ray generator and the bump. Further, when the inspection object is supported by being placed on a support member such as a carbon plate, the thickness of the support member is also added. Therefore, there is a problem that the distance between the X-ray generator and the bump cannot be made smaller than a certain value. Further, since the substrate thickness of the inspection target varies depending on the target, there is a problem that the distance between the X-ray generator and the bump is not constant.
[0009]
In the case of solder bumps, it is important not only to inspect the outer diameter shape but also to inspect whether or not voids (voids) exist inside the solder bumps. Since there is a limit to how close the distance can be, the S / N ratio (signal to noise) of the obtained image is not only low, but also because the distance between the X-ray generator and the bump is not constant, the size of the void and the like must be reduced. This leads to the problem that it is difficult to measure stably.
Accordingly, it is an object of the present invention to improve the S / N ratio of an X-ray image so that a bump can be inspected stably.
[0010]
[Means for Solving the Problems]
The present invention relates to a bump inspection apparatus for inspecting a plurality of bumps formed on a substrate by transmitting X-rays, wherein the substrate to be inspected is supported such that its bump formation surface faces downward, A substrate support mechanism that can be moved by the X-ray generator, an X-ray generator that is arranged below the substrate supported by the substrate support mechanism and emits X-rays upward, and an X-ray that is above the substrate supported by the substrate support mechanism. A flat panel as an X-ray detector disposed at a position for detecting X-rays emitted from the generator.
[0011]
In the present invention, since the bump forming surface of the substrate to be inspected faces the direction of the X-ray generator, the observation site to be inspected, that is, the distance between the bump and the X-ray generator can be reduced. it can. Therefore, it is possible to improve the detection accuracy of the void of the bump and the like.
[0012]
Further, a flat panel serving as a detector can be close to the tube. With such an arrangement, the luminance of the detector increases even at the same imaging magnification and the same X-ray output. When an image tube is used as a detector as in a conventional apparatus, such an arrangement saturates the detector. Further, when the image tube is brought closer to the X-ray generator by a certain distance or more, shading is sharpened based on the curvature of the image tube, and the luminance distribution of the obtained image is not constant, which makes image processing after binarization difficult.
[0013]
On the other hand, since the flat panel is used as the detector according to the present invention, there is no problem such as shading, and the disadvantage of the flat panel having low luminance is an advantage only in the present invention. Since the output is less likely to be saturated, the output can be increased in a range where the X-ray generator has room, and as a result, the S / N ratio of the image can be improved.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in detail based on examples.
FIG. 1 schematically shows one embodiment. Reference numeral 10 denotes a substrate support mechanism that supports the substrate 2 to be inspected so that the bump forming surface faces downward. The substrate support mechanism 10 includes a tray-shaped substrate holder 12 for supporting the substrate 2 with its bump formation surface facing downward and the bumps 4 exposed. The support mechanism 10 has a drive mechanism such as an XY stage for supporting the substrate 2 in a horizontal plane and moving the substrate 2 in the X and Y directions in the horizontal plane to be positioned at the inspection position. The movement is controlled by 14.
[0015]
An X-ray generator 16 is arranged and fixed below the substrate 2 supported by the substrate support mechanism 10. The X-ray generator 16 includes an X-ray tube, and X-rays 18 generated from the X-ray tube pass through the substrate 2.
[0016]
A flat panel 20 as an X-ray detector is arranged above the substrate 2 supported by the substrate support mechanism 10 so as to face the X-ray generator 16. Reference numeral 22 denotes an image processing apparatus which takes in an X-ray image detected by the flat panel 20 and determines the shape of the bump 4 and the presence or absence of a void inside the bump 4.
[0017]
In this embodiment, the substrate 2 supported by the substrate support mechanism 10 is positioned at the inspection position by the movement control unit 14, and the X-rays 18 emitted from the X-ray generator 16 penetrate the bumps 4 of the substrate and pass through the flat panel. At step 20, the X-ray image is taken into the image processing device 22, and the quality of the bump is determined.
[0018]
FIG. 3 schematically shows a target portion of the X-ray generator. The X-ray tube 16a of the X-ray generator 16 has a target 16b in a vacuum region inside (the lower side in the figure) of the X-ray tube 16 and is irradiated with an electron beam 27 so that the X-ray is emitted from the target 16a. 18 occurs.
[0019]
FIG. 4 shows an example of a preferred arrangement of the substrate support mechanism 10 and the X-ray generator 16. The X-ray tube 16a of the X-ray generator 16 has a plate 24 made of fluororesin or the like attached to a peripheral portion of the upper surface thereof. The X-ray tube 16a is arranged so that the plate 24 contacts the lower surface of the tray 12 of the substrate support mechanism. As a result, the distance between the X-ray tube 16a and the substrate 2 is always constant. Therefore, the point 26 where X-rays are generated on the target 16b of the X-ray tube 16a, that is, the distance between the focus of the X-ray tube 16a and the bump 4 Approach a certain distance.
[0020]
FIG. 5A shows a preferred example of the frame 12 of the substrate support mechanism. An opening 30 for supporting the substrates 2 one by one is opened in the frame 12, and the substrate 2 is inserted and supported in the opening 30 such that the bumps face downward. Two adjacent sides of the four sides of each opening 32 of the frame 12 are provided with a spring material 32 for pressing the substrate 2 inserted into the opening 32 in the horizontal direction to fix the position. As shown in FIG. 5 (B), the spring member 32 has a bent shape, and applies a spring force in a direction of pressing the substrate 2 against the edge of the opposing frame through the gap between the frame 12 and the substrate 2. Let it work. As shown by arrows in FIG. 5A, the two spring members 32 press the substrate 2 so that the substrate 2 is pressed against the frame 12 and the position is fixed.
[0021]
FIG. 6 shows a preferred embodiment for accurately positioning the bumps to be inspected on the substrate 2 to be inspected. In the bump formation surface of the substrate 2 fixed to the frame 12 of the support mechanism, at two or more places around the area where the bumps 4 are arranged as shown in FIG. The image of the area as shown is measured. The position of the substrate 2 is corrected based on the image.
[0022]
An X-ray for inspection may be used to capture images of the areas a and b, or an image reading device such as a CCD camera may be separately provided at another position.
[0023]
【The invention's effect】
According to the present invention, a substrate to be inspected is supported so that its bump forming surface faces downward so as to be movable in a horizontal plane, an X-ray generator is provided below the supported substrate, and an X-ray is provided above the substrate. Since the detector is arranged, the distance between the bump and the X-ray generator can be reduced, and the accuracy of detecting a void in the bump can be improved.
In addition, since a flat panel is used as the X-ray detector, there is no problem such as shading even when approaching the X-ray tube, and the output is unlikely to be saturated. And the S / N ratio of the image can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing one embodiment.
FIG. 2 is a perspective view showing a substrate to be inspected by the inspection apparatus of the present invention together with a chip mounted thereon.
FIG. 3 is a schematic sectional view of a main part of one embodiment.
FIG. 4 is a schematic sectional view of a main part of another embodiment.
FIG. 5A is a plan view showing a frame of a substrate support mechanism and a supported substrate, and FIG. 5B is a perspective view showing a spring member provided in the substrate support mechanism.
FIG. 6 is a plan view of the substrate for explaining the positioning of the inspection site on the substrate.
[Explanation of symbols]
2 Substrate to be inspected 4 Bump 10 Substrate support mechanism 12 Substrate holder 14 Movement control unit 16 X-ray generator 16a X-ray tube 16b Target 18 X-ray 20 Flat panel 32 Spring material

Claims (5)

In a bump inspection apparatus for inspecting a plurality of bumps formed on a substrate by transmitting X-rays,
A substrate support mechanism that supports the substrate to be inspected so that its bump forming surface faces downward, and can be moved in a horizontal plane,
An X-ray generator that is arranged below the substrate supported by the substrate support mechanism and emits X-rays upward;
A flat panel as an X-ray detector disposed at a position above the substrate supported by the substrate support mechanism and for detecting X-rays emitted from the X-ray generator. Inspection equipment. The bump inspection apparatus according to claim 1, wherein the substrate support mechanism includes a tray-shaped substrate holder that is supported at a peripheral portion of the substrate so as to expose a bump formation surface of the substrate. In the X-ray generator, a distance between a focal point of the X-ray tube and the bump forming surface is kept constant by contacting a peripheral portion of an upper surface of the X-ray tube with a lower surface of the substrate holder. Item 3. A bump inspection device according to Item 2. 4. The bump inspection apparatus according to claim 2, wherein the substrate holder includes a biasing member that presses a supported substrate in a horizontal direction to fix a position. 5. For each substrate supported by the substrate holder, a means for measuring at least two images around the area where the bumps are arranged on the bump formation surface and correcting the inspection position for each substrate based on the measured images. The bump inspection apparatus according to claim 1, further comprising:

Images