JPH04319610A - Inspecting apparatus of flip chip - Google Patents

Abstract

PURPOSE:To detect an X-ray fluoroscopic image at a high speed and with high resolution and high sensitivity by a method wherein an optical image corresponding to an image of X-rays transmitted through a substance to be inspected is applied to a TDI(time delayed integrated) sensor having a plurality of pixel lines. CONSTITUTION:An image of X-rays transmitted through a substance 3 to be inspected is received and turned into an optical image by a fluorescent screen. The optical axis of the optical image is changed by a mirror 5 and the image is formed and condensed by lens systems 6 and 8. This optical image is applied to a TDI sensor 9 comprising a plurality of pixel lines and having an image superposing function. An image processing means 11 receives as an input an electric charge generated in the sensor 9, executes an image processing and outputs a two-dimensional image. A stage control means 12 makes a stage 2 run straight so that the optical image of the substance 3 applied onto the sensor 9 be shifted in the same direction with that of charge transfer between adjacent pixel lines of the sensor 9 so that it corresponds to the speed of the charge transfer. Besides, it is effective to provide a microchannel plate 7 which reinforces the luminance of the optical image sensed by the sensor 9.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flip chip inspection device, and more particularly to a device for detecting X-ray fluoroscopic images necessary for inspecting microbumps on a flip chip connected to electrodes on a substrate for defects.

[0002] In recent years, electronic components mounted on printed circuit boards have become increasingly miniaturized, and the mounting density of electronic components has also increased. Along with this, there are an increasing number of parts that cannot be inspected by visual inspection. For example, many tiny microbumps with a radius of about 200 μm are formed at the connection part of a flip chip, but since these microbumps are hidden behind the LSI package, they cannot be inspected using optical methods. I can't. A fluoroscopic inspection method using X-rays is an effective inspection method in such cases.

0003

2. Description of the Related Art FIG. 4 shows a perspective view of a flip chip. The flip chip 21 is connected to an electrode on a substrate 23 via a large number of microbumps 22 with a radius of about 200 μm.

[0004] FIGS. 5 and 6 show examples of the shape of microbumps at the connection portion of a flip chip. What is shown in FIG. 5 is an external view of a normal microbump, and what is shown in FIG. 6 is an external view of a defective microbump. In other words, in (a) of FIG. 6, the fusion between the bumps is insufficient, and (
b) (c) and (d) are locally constricted, and (e in the same figure)
) has a void inside, (f) in the same figure has a positional shift, and (g) in the same figure has a narrow upper part.

[0005] Therefore, after connecting the flip chip,
Although it is necessary to inspect the presence or absence of microbump defects in the connection portion, there is currently no optical inspection technique suitable for inspecting such defects.

[0006] A high-speed inspection method using X-rays uses a CCD line sensor to
A method of extracting a signal charge corresponding to a line perspective image and converting it into an image to detect defects is being considered.

[0007]

The method using a CCD line sensor is expected to improve the inspection speed, but on the other hand, the charge accumulation time per pixel of the line sensor is reduced. The amount of X-rays used to inspect microbumps is as small as approximately 1R (roentgen)/min, so if the accumulation time is short, quantum noise specific to the
/N ratio becomes difficult to obtain.

An object of the present invention is to eliminate these drawbacks, and to provide a flip-chip inspection device that can detect X-ray fluoroscopic images of microbumps on flip-chip connections at high speed, high resolution, and high sensitivity. It is in.

[0009]

[Means for Solving the Problems] The above object can be achieved by any of the following means.

[0010] The first means includes a minute focus X-ray source (1);
A stage (2) is provided to face the fine focus X-ray source (1), and a stage (2) on which an object to be inspected (3) to which a flip chip is connected is placed and moves; A fluorescent screen (4) that receives the transmitted X-ray image and converts it into an optical image, a mirror (5) that changes the optical axis of the optical image converted by the fluorescent screen (4), and a mirror (5) that forms the optical image.・The lens system (6, 8) that condenses the light and the image formed by this lens system (6, 8)
TDI (Ti
an image processing means (11) that receives the output signal of the TDI sensor (9), performs image processing, and outputs a two-dimensional image; The said stage (
2) and a stage control means (12) for causing the stage to travel in a straight line. In addition, MCP (M
It is effective if an icro Channel Plate (7) is provided.

The second means includes a fine focus X-ray source (1);
A stage (2) is provided to face the fine focus X-ray source (1), and a stage (2) on which an object to be inspected (3) to which a flip chip is connected is placed and moves; X that receives the transmitted X-ray image and outputs an optical image with enhanced brightness
a ray image intensifier (13), a condenser lens (8) that condenses the optical image output from the X-ray image intensifier (13), and a condenser lens (8) that condenses the optical image output from the X-ray image intensifier (13); T is made up of multiple pixel lines that generate electric charges when irradiated with an optical image, and has an image superimposition function.
DI (Time Delayed Integrated
) sensor (9), an image processing means (11) that receives the output signal of this TDI sensor (9), performs image processing, and outputs a two-dimensional image; The stage (2) is moved such that the optical image of the object (3) to be inspected moves in the same direction as the charge transfer direction in accordance with the charge transfer speed between adjacent pixel lines of the TDI sensor (9). Stage control means (12) for running in a straight line
) is a flip chip inspection device.

[0012] Instead of the stage control means (12), the TDI sensor (9) is operated in a direction opposite to the charge transfer direction in accordance with the charge transfer speed between adjacent pixel lines of the TDI sensor (9).
TDI sensor control means for moving the sensor (9) may be provided. In addition, the TDI sensor (9)
is preferably a tapped TDI sensor.

[0013]

[Operation] The operation of the present invention will be explained with reference to the principle diagram shown in FIG. In the figure, 3 is a test object to which a flip chip is connected, 4 is a fluorescent screen that converts the X-ray image transmitted through the test object 3 into an optical image, and 9 is a TDI (Time Del
ayed Integral) CCD sensor.

As shown in the figure, the TDICCD sensor 9 has a number of pixels arranged in a line, each of which generates an electric charge when the light receiving portion is irradiated with light, and is arranged in parallel. For example, charges generated in a first pixel line are transferred to an adjacent second pixel line after a certain period of time. The charges sequentially transferred to adjacent pixel lines in this manner are finally transferred to the n-th pixel line and taken out from there.

The light corresponding to point A of the object to be inspected 3 is TDIC.
Suppose that point a on the first pixel line of the CD sensor 9 is irradiated. The charge generated at point a is transferred to point a' of the second pixel line after a certain period of time. When the inspected object 3 is moved to the right in the figure (the same direction as the charge transfer direction) in accordance with the charge transfer, and the point A is moved to the point A',
The same light that was previously applied to point a on the first pixel line (A of object 3) is applied to point a' on the second pixel line.
The light corresponding to the point) is irradiated to generate a charge, which is superimposed on the charge transferred from point a of the first pixel line to point a' of the second pixel line.

By sequentially repeating the above steps up to the n-th pixel line, the charge accumulation time of the TDICCD sensor 9 due to the optical image corresponding to the object 3 to be inspected is equal to that of the normal CC
It is n times as large as the D line sensor. In general, quantum noise decreases to 1/√n when the image signal acquisition time increases n times, so it becomes possible to detect an image with a good S/N ratio.

Furthermore, if a tapped TDICCD sensor in which a tap is provided in the signal extraction section is used, the image signals of a plurality of regions of the signal extraction section divided by the taps are simultaneously extracted in parallel. Retrieval is faster. As a result, for example, a TD with 16 taps
If an ICCD sensor is used, the inspection speed will be increased by about one order of magnitude.

Note that a resolution of about 10 μm can be obtained by using a microfocus type X-ray source, that is, an X-ray source with an X-ray focal point of 10 μm or less in diameter.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, flip chip inspection apparatuses according to three embodiments of the present invention will be described below.

First Example FIG. 2 shows a configuration diagram of a flip chip inspection apparatus. In the figure, 1 is a micro-focus X-ray source with an X-ray focus of about 10 μm, and 2 is a stage on which an object to be inspected 3 to which a flip chip is connected is placed and is movable in the X, Y, and Z directions. ,4
is the X generated by the minute focus X-ray source 1 that has passed through the inspected object 3
A fluorescent screen (rare earth fluorescent material, plastic scintillator, etc.) that converts a line image into an optical image. 5 is a mirror for taking the optical image out of the X-ray radiation path, 6 is an imaging lens, and 7 is an MCP (Mic) that enhances the brightness of the optical image.
ro Channel Plate), 8 is a condenser lens, and 9 is a TDICCD sensor. Here, the reason why the mirror 5 is necessary is to eliminate the drawback that if the MCP is placed directly under the fluorescent screen, noise due to X-rays will be mixed in.

10 is an A/D converter, and the TDICCD sensor 9 is divided into a plurality of regions by a plurality of taps.
The signal charges taken out simultaneously and in parallel from each of the charge extraction regions in a short period of time are A/D converted. Reference numeral 11 denotes an image processing means that receives the digital signal output from the A/D converter 10 and outputs a two-dimensional image. Using this two-dimensional image, the flip chip connection is inspected using a separately provided inspection circuit.

Reference numeral 12 denotes a stage control means, in which an optical image of the object to be inspected 3 irradiated onto the TDICCD sensor 9 through the condensing lens 8 passes over the TDICCD sensor 9.
The stage 2 is moved linearly in the X and Y planes so as to move in the same direction as the charge transfer direction of the CD sensor 9 at a speed corresponding to the charge transfer speed.

Note that the magnification of the X-ray image can be changed by moving the stage 2 in the Z-axis direction.

Furthermore, if an optical image with sufficient brightness can be obtained, the MCP 7 may not necessarily be provided.

Second Example FIG. 3 shows a configuration diagram of a flip chip inspection apparatus. In the figure,
Components that are the same as those shown in FIG. 2 are indicated by the same symbols, and 13 is an X-ray image intensifier that receives the X-ray image transmitted through the inspection object 3 and outputs an optical image with enhanced brightness. It is. Note that since the amount of X-rays that pass through the X-ray image intensifier 13 and leak downward is very small, the mirror 5 that removes the optical axis of the optical image from the X-ray irradiation path is not necessarily required.

Third Example In a flip chip inspection apparatus having the same configuration as the first and second examples, instead of moving the stage 2 in a straight line, the TDICCD sensor 9 is moved in the opposite direction to the charge transfer direction. A TDI sensor control means (not shown) is provided to move the TDI sensor at a speed corresponding to the charge transfer speed.

[0027]

Effects of the Invention As explained above, in the flip chip inspection device according to the present invention,
An optical image corresponding to a line image is created using a TD having n pixel lines.
Since the ICCD sensor is irradiated and the optical image is moved at a speed corresponding to the charge transfer speed between pixel lines of the TDICCD sensor, the charge accumulation time due to the optical image irradiated to the TDICCD sensor is increased by n times, resulting in a good S/ X of N ratio
Fluoroscopic images can be obtained, and resolution is improved by using a microfocus X-ray source, so high speed, high resolution,
X-ray fluoroscopic images of microbumps in flip-chip connections can be obtained with high sensitivity, and this image can be used to automatically inspect microbumps for defects.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention.

FIG. 2 is a configuration diagram of a flip chip inspection device according to the present invention. (Compatible with the first embodiment)

FIG. 3 is a configuration diagram of a flip chip inspection device according to the present invention. (Compatible with the second embodiment)

FIG. 4 is an explanatory diagram of a flip chip.

FIG. 5 is a diagram illustrating the shape of microbumps in a flip-chip connection. (normal bump)

FIG. 6 is a diagram illustrating the shape of microbumps in a flip-chip connection. (Bad bump)

[Explanation of symbols]

1. Microfocus X-ray source 2 Stage 3. Object to be inspected 4 Fluorescent screen 5 Mirror 6 Imaging lens 7 MCP 8 Condensing lens 9 TDICCD sensor 10 A/D converter 11 Image processing means 12 Stage control means

Claims (4)

[Claims] Claim 1: A microfocus X-ray source (1) and an object (3) provided opposite to the microfocus X-ray source (1) to which a flip chip is connected are placed and moved. stage(
2), a fluorescent screen (4) that receives the X-ray image transmitted through the inspection object (3) and converts it into an optical image, and changes the optical axis of the optical image converted by the fluorescent screen (4). a mirror (5), a lens system (6, 8) that forms and focuses the optical image;
A TDI (Time Del) is composed of a plurality of pixel lines that generate electric charges when irradiated with the optical image formed and focused by the lens system (6, 8), and has an image superimposition function.
ayed Integrated) sensor (9);
an image processing means (11) that receives the output signal of the TDI sensor (9), processes the image, and outputs a two-dimensional image; and the object to be inspected (3) that is irradiated onto the TDI sensor (9). the stage (2) such that the optical image of the TDI sensor (9) moves in the same direction as the charge transfer direction corresponding to the charge transfer speed between adjacent pixel lines of the TDI sensor (9);
1. A flip-chip inspection apparatus comprising: stage control means (12) for causing the stage to travel in a straight line. 2. A fine focus X-ray source (1) and an object to be inspected (3) provided opposite to the fine focus X-ray source (1) and connected to a flip chip are placed and moved. stage(
2), an X-ray image intensifier (13) that receives the X-ray image transmitted through the object to be inspected (3) and outputs an optical image with enhanced brightness, and the X-ray image intensifier ( 13), and a plurality of pixel lines that generate electric charges when irradiated with the optical image focused by the focusing lens (8). TDI (TimeDe) with superimposition function
a layered integrated) sensor (9), and an image processing means (11) that receives the output signal of the TDI sensor (9), performs image processing, and outputs a two-dimensional image.
The optical image of the object to be inspected (3) irradiated onto the TDI sensor (9) is arranged in the charge transfer direction corresponding to the charge transfer speed between adjacent pixel lines of the TDI sensor (9). The stage (2) is moved in the same direction as the
1. A flip chip inspection device comprising: a stage control means (12) for causing a stage control device (12) to move the device (12) in a straight line; 3. The flip-chip inspection apparatus according to claim 1, wherein the TDI sensor (9) is arranged such that the TDI sensor (9) is configured to conduct the TDI sensor (9) in a direction opposite to the charge transfer direction in accordance with a charge transfer speed between adjacent pixel lines of the TDI sensor (9). T to move the sensor (9)
A flip chip inspection device characterized by being provided with a DI sensor control means. 4. The TDI sensor (9) is a tapped T.
4. The flip chip inspection device according to claim 1, 2, or 3, wherein the flip chip inspection device is a DI sensor.