JPH04125942A - Object surface shape displaying equipment using x-ray and object surface shape inspection equipment - Google Patents

Abstract

PURPOSE:To three-dimensionally simulate and display the shape and the surface state of an object to be inspected, by a method wherein an X-ray absorption distribution cure is obtained by computing transmission X-ray absorption quantity, while the object to be inspected is scanned with an X-ray in a specified direction. CONSTITUTION:A stage 5 which retains an object 4 to be inspected and is capable of three-dimensional moving is irradiated with an X-ray from an X-ray source 3. The X-ray absorption quantity is calculated with a transmission X-ray absorption quantity computing means 21, while a soldering part 16 is scanned in a specified direction. By computing an equation (2), an X-ray absorption distribution curve is obtained, and a monochromatic image is displayed. The ratio of the X-ray absorption quantity is worked into data about the thickness of the object to be inspected. At least one of the X-ray absorption quantities is subtracted from a subtraction means 25 and off-set, thereby obtaining the thickness of the soldering part 16, e.g. the (distribution of the height. This operation is computation-processed in order along all scanning lines, and all of the results are three-dimensionally displayed. Thus the shape of the object to be inspected and the surface state are observed. Thereby the three-dimensional shape of the soldering part of a surface mount device can be simulated.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an object surface shape display device using X-rays and a device for inspecting the surface shape of an object to be inspected. The purpose is to easily understand and inspect the shape of the object to be inspected by displaying the surface shape in a way that is visible to the human eye. Transmitted X-ray detection means, means for calculating the X-ray absorption amount of the transmitted X-rays, logarithmic conversion means for performing logarithmic conversion on the X-ray absorption amount, and inversion processing for the information obtained by the logarithmic conversion means. and a display means for displaying information on the height of the object to be inspected obtained by the reversing means in a two-dimensional manner, and a control means for controlling the operation of each of the above-mentioned means. Configure.

[Industrial Field of Application] The present invention relates to an object surface shape display device using X-rays and a device for inspecting the surface shape of an object to be inspected.

[Conventional technology]

As the density and integration of electronic components progresses, it becomes possible to quickly and accurately check whether or not mounted components mounted on a board are reliably and accurately connected to the pads at the ends of the board or wiring sections. (It has become necessary to detect

Conventionally, such inspections have been carried out visually or by nondestructive inspection methods, but there are limitations, and it has become necessary to introduce transmission inspection methods using, for example, X-rays. .

However, with such a transmission type inspection method, although the amount of X-ray absorption at a specific location of a mounted component can be detected, it is not possible to obtain information regarding the shape of the specific portion.

Furthermore, considering an example in which such a transmission inspection method is applied to inspecting the shape of solder joints on a surface mount board, solder appearance inspection has conventionally been performed optically, but surface mount technology for solder As technology advances, lead sizes have become smaller, and solder joint positions are often hidden behind the chip, making visual inspection impossible.

Furthermore, regarding the solder part, it is not enough just to connect the board and the lead part of the chip; it is also important to check whether the solder is evenly applied, the state of solder diffusion, and the surface of the solder. An important condition is whether the shape, solder thickness unevenness, etc. meet certain conditions.

Therefore, there is a need for an apparatus that can inspect and confirm the shape of solder joints on the joint surfaces.

FIG. 5 shows an example of a conventional X-ray inspection apparatus for an object to be inspected.

That is, in the conventional X-ray inspection device, inside the X-ray shielding box 2,
An X-ray source 3, a movable stage 5 holding an object to be inspected 4, and transmitted X-ray detection means 8 comprising, for example, an image intensifier 6 and a vidicon camera 7, are provided. After irradiating the object 2 with X-rays from the source 3 and detecting the resulting X-ray absorption distribution with the image intensifier 6 and converting it into visible light with the vidicon camera 7, the camera control unit 9 A method is adopted in which the information is displayed on a display means 10 such as a monitor television for inspection.

However, in such inspection equipment that uses X-rays, the image that the inspector refers to is the absorption distribution of X-rays and does not directly show the thickness distribution of the target object. The inspector had to memorize the correspondence between the solder and the displayed image, and the inspection required skill.

The problem with this prior art technique is not limited to solder joints, but can be applied to all types of devices in which the shape of the metal material in the internal portion, which cannot be observed externally, is a problem.

For example, when a part of a ceramic substrate is made of metal to connect mounted components, problems similar to those described above are involved.

[Problem to be solved by the invention]

The purpose of the present invention is to improve the above-mentioned drawbacks of the prior art, and to obtain information regarding the shape, especially the height, of the internal part of the metal material that cannot be observed from the outside by using transmitted X-rays on the object to be inspected. By performing a predetermined conversion process on the X-ray absorption distribution, it is visually displayed as information about the height of a shape that is visible to the human eye. The object of the present invention is to provide an object surface shape display device and an object surface inspection device for an object to be inspected that do not require skill.

[Means to solve the problem]

In order to achieve the above object, the present invention employs the following technical configuration.

That is, an X-ray source, a movable stage that holds the object to be inspected, a means for detecting transmitted X-rays, a means for calculating the amount of X-ray absorption of the transmitted X-rays, and a means for performing logarithmic transformation on the amount of X-ray absorption. A logarithmic conversion means, an inversion means that performs an inversion process on the information obtained by the logarithm conversion means, and a display that expands and displays information regarding the height of the object to be inspected obtained by the inversion means in a two-dimensional manner. and a control means for controlling the operation of each of the above-mentioned means. Means, said transmission
means for calculating the X-ray absorption amount of a ray, logarithmic conversion means for performing logarithmic conversion on the X-ray absorption amount, inversion means for performing inversion processing on the information obtained by the logarithm conversion means, and the inversion means This is an inspection device for an object to be inspected, which is comprised of a display means for displaying flatly developed information regarding the height of the object to be inspected obtained by the method, and a control means for controlling the operation of each of the above-mentioned means. .

[For production]

In the present invention, by adopting the above configuration,
In addition to converting the X-rays that have passed through the object to be inspected into visible information regarding the height of the object to be inspected, by expanding this visible information into a plane, it is possible to directly determine the surface shape of the object to be inspected. It can be inspected.

〔Example〕

A specific example of the object surface shape display device using X-rays according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of an object surface shape display device using X-rays according to the present invention, and is also a diagram explaining the principle of the present invention.

The basic configuration of FIG. 1 is the same as the configuration shown in FIG. For example, a transmitted X-ray detection means 8 consisting of an image intensifier 6, a vidicon camera 7, etc. is provided, and the transmitted X-ray detection means 8 is configured to be displayed on a display means 10 such as a monitor television via a camera control unit 9. There is.

The movable stage 5 is configured to be movable in three axes, and in particular, it restricts the movement of the object to be inspected and the movement related to X-ray scanning in the X and Y directions. The direction is the direction of movement that contributes to the magnification.

However, in the present invention, as described above, a conversion means 11 is added that converts the X-rays transmitted through the object to be inspected into visible information regarding the height of the object to be inspected. The configuration of this means will be described later.

Conventionally, the object to be inspected is irradiated with X-rays and a grayscale image regarding the X-ray absorption amount distribution is obtained from the transmitted X-rays. It does not represent information about height.

However, the amount of X-rays absorbed by the object to be inspected is
There is a fact that many X-rays are absorbed, and conversely, when the thickness is thin, the amount of X-ray absorption is small.Furthermore, the relationship between the amount of X-ray absorption and the thickness of the object to be inspected is a simple linear relationship. It is known that there is no difference, and that it changes depending on the exponential relationship.

As a result of pursuing such a relationship, the relationship between the displayed image and the thickness, that is, the height, of the object to be inspected and the amount of X-ray absorption is expressed by the following equation (1).

That is, the height distribution of each part is fm (x, y),
Image I (x, y) obtained by patented X-ray irradiation characterized by the absorption rate of each region for X-rays is 1(x, y)
=αIoΣ−exp(μm·fm(x, y)). Here, Io is the radiation dose.

Therefore, in order to obtain the height distribution of the object, it is sufficient to logarithmically transform (1) and calculate equation (2).

In(1) =-Σ(u* ・fi=(x, y))
Therefore, by calculating the above equation (2) while scanning the X-ray in a specific direction along the object to be inspected, the X-ray absorption amount distribution curve can be obtained.

Now, the object to be inspected is specified as one in which the lead part 14 of a semiconductor chip 12 as shown in FIG. Consider the case where the soldering is performed by observing the joint state of the parts from the thickness or surface condition and inspecting the suitability of the soldering.

Therefore, it is assumed that the soldering is such that the joint shape of the portion 16 is as shown in FIG. 3A.

First, as shown in FIG. 4, the object to be inspected is irradiated with X-rays, and the X-rays are scanned in one specific direction of the object to be inspected 16. (Step a) As a result, means 2 for calculating the amount of transmitted X-ray absorption from transmitted X-rays.
1 to calculate the amount of X-ray absorption at each position,
An X-ray absorption distribution curve as shown in Figure 3B was obtained,
Based on this, a grayscale image can be displayed on the display means. (Step b) Next, the logarithmic conversion means 23 performs logarithmic conversion from the X-ray absorption amount distribution chart obtained in step b to obtain a chart showing the ratio of the X-ray absorption amount as shown in FIG. 3C. (Step C) Next, the chart showing the ratio of the X-ray absorption amount obtained in Step C is processed using the inverting means 24 into information regarding the thickness of the object to be inspected as shown in the third diagram. do. (Step d) In this specific example, the information regarding the thickness of the object to be inspected obtained here is the total thickness of the lead 14, the soldering portion 16, and the pad portion 15. It is related to.

Therefore, depending on the type of object to be inspected, it may be necessary to confirm the shape of the surface of the object to be inspected, and in that case, the purpose can be achieved using the information obtained in step d. .

However, in this specific example, it is necessary to observe the height of the part or its surface shape, and check the distribution of the height, etc. for soldering. The existence of pad 15 is a hindrance.

However, the thickness and X-ray absorption rate of the pad portion 15 are approximately constant, the thickness and X-ray absorption rate of the lead 14 are approximately constant, and the thickness and average X-ray absorption rate of the substrate 13 are approximately constant. Considering that the X-ray absorption rate of the board is constant and that the X-ray absorption rate of the board is smaller than that of the solder, the above By subtracting the amount of X-ray absorption of at least one of the parts detected by the subtracting means 25 (steps e to g), the necessary offset is performed, and the object to be inspected as shown in the upper part of FIG. 3, that is, the solder part 16 thickness, in other words, the distribution regarding height is determined.

(Step h) Furthermore, in the present invention, the information obtained in Step h is
Arithmetic processing is performed sequentially along all scanning lines of the object to be inspected (step i), and all of the results are transferred to the third
The shape of the object to be inspected can be determined by displaying the shape of the object to be inspected, by displaying it as shown in Fig.
It becomes possible to visually observe the surface condition.

In the present invention, it is preferable to provide a storage means 27 in which information regarding the known conditions indicating the above-mentioned constant value is stored in advance, and when performing the above arithmetic processing, necessary information can be appropriately retrieved from the storage means. may be read out and a predetermined arithmetic process executed, or the amount of X-ray absorption necessary for offset may be calculated from the stored information, and the offset amount may be subtracted from the measured amount of X-ray absorption. .

Further, the storage means 27 according to the present invention preferably stores positional information regarding the object to be inspected as X and Y coordinate values.

Further, as another specific example of the present invention, when the object surface shape display device having the above-described configuration is used as a surface condition inspection device for an object to be inspected or a height inspection device for an object to be inspected, An image storage means 28 is added in which information regarding the thickness and surface condition of a normal or defective object to be inspected as a reference is stored in advance, and comparison calculation processing is performed with the inspection information of the object to be inspected. This makes it possible to perform the test easily and quickly.

Furthermore, in the present invention, the amount of X-ray absorption in a portion without a fillet can be measured using the X-ray surface mount board inspection apparatus, and this measured value can be used for offset.

The configuration of the converting means 11 in the present invention is already clear from FIG. The transmitted X-ray absorption amount calculation means 21 calculates the X-ray absorption amount distribution through the A/D converter 20 and the frame buffer 22.

After that, the X-ray absorption amount distribution information is transferred to the processing system, and bus 3
1, operations such as logarithmic conversion, inversion processing, offset processing, and comparison processing with reference information are executed under the control of a microcomputer (CPU) 29 that controls all calculation processing of the conversion means 11 through be.

Further, each calculation result of the conversion means 11 is displayed on the display means 10 as appropriate.

Further, the converting means 11 is provided with an input/output port (I10 port) 30 for driving the moving stage in displacement based on the calculation result.

[Effects] According to the present invention, as a result of employing the above technical configuration, it is possible to measure the height distribution of the soldering portion of a surface mount board, and it is possible to display a three-dimensional shape in a pseudo manner. Therefore, according to the present invention, the surface shape of the object to be inspected can be easily measured, such as by measuring the solder shape of a surface-mounted board, and no skill in inspection is required.

Further, by comparing the obtained image with a reference image, automatic solder inspection can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an object surface shape display device using X-rays according to the present invention, and is a diagram illustrating the principle of the present invention. FIG. 2 is a perspective view showing a specific example of an object to be inspected used in the present invention. 3A to 3F are diagrams showing the measurement procedure of the object surface shape display device according to the present invention. FIG. 4 is a flowchart showing the measurement procedure in the object surface shape display device according to the present invention. FIG. 5 is a schematic diagram showing an example of a conventional object surface shape display device using X-rays. 1...Object surface shape display device 2...X-ray shielding box 3...X-ray source 4...Object to be inspected 5...Movable stage 6 for holding the object to be inspected... - Image intensifier 67... Vidicon camera 8... Transmitted X-ray detection means 9... Camera control unit 10... Display means 11... Conversion means 12... Semiconductor chip 13... Substrate 14... Lead part 15... Pad part 16... Soldering part 20... A/D converter 21... Transmitted X-ray absorption amount calculating means 22... Frame buffer 23... Logarithmic conversion means 24... Inversion means 25... Subtraction means 6... Offset means 7... Storage means 8... Image storage means 9... Microcomputer (CPU) 0... Input/output board (I10 boat)■...Has

Claims (1)

[Claims] 1. An X-ray source, a movable stage that holds an object to be inspected, a transmitted X-ray detection means, a means for calculating the amount of X-ray absorption of the transmitted X-rays, and a means for calculating the amount of X-ray absorption of the transmitted X-rays. A logarithmic conversion means for performing logarithmic conversion, an inversion means for performing inversion processing on the information obtained by the logarithm conversion means, and information regarding the height of the object to be inspected obtained by the inversion means in a two-dimensional manner. A device for displaying the surface shape of an object using X-rays, characterized in that it is comprised of a display device that expands and displays the image, and a control device that controls the operation of each of the above-mentioned devices. 2. The object surface shape display device using X-rays according to claim 1, further comprising subtraction means for subtracting known information from the information obtained by the inversion means. 3. The object surface shape display device according to claim 2, further comprising storage means for storing the known information. 4. An apparatus for inspecting the surface shape of an object to be inspected using the object surface shape display device according to any one of claims 1 to 3. 5. A reference value storage means for storing the surface shape of a normal reference object in advance, a means for comparing the information stored in the reference value storage means with information regarding the surface state of the object to be inspected, and from the comparison means. 5. The apparatus for inspecting the surface shape of an object to be inspected according to claim 4, further comprising means for displaying the output of said object.