JPH0252245A - X-ray inspection device - Google Patents

Abstract

PURPOSE:To enable nondestructive inspection by X rays nearly under temperature conditions at the time of actual use and to improve the reliability of the time of actual use and to improve the reliability of the inspection by heating or cooling a substrate to be inspected and holding the temperature conditions at the time of the actual use or severer conditions. CONSTITUTION:The substrate 20 to be inspected is arranged between the X-ray tube 11 of an X-ray generation part 10 and an image sensor 40 for X-ray detection to perform X-ray radiography and also radiograph an X-ray transmission image on an X-ray recording medium which can be arranged in front of the image sensor 40, e.g. an instant film 200. Then when the nondestructive inspection of the substrate 20 to be inspected by the X rays is carried out, the substrate 20 to be inspected is heated by a heating means such as an infrared-ray lamp or cooled by a cooling means to perform the inspection under temperature conditions wherein the substrate 20 to be inspected is used while incorporated in actual equipment or under severer temperature conditions in consideration of a safety ratio. Consequently, a defect such as a near-bridge phenomenon can securely be inspected at high temperature.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an X-ray inspection apparatus for a substrate to be inspected.

(Prior Art) This type of X-ray inspection apparatus is configured such that a subject is placed between an X-ray generation source and an X-ray TV camera, and X-rays are emitted from the X-ray generation source toward the subject. are doing.

The X-rays that have passed through the object are input to an X-ray TV camera, which converts the transmitted X-ray image into an optical image, which is then photographed by the camera and converted into an electrical signal, which displays the object image on a monitor. configured to display.

For example, if the subject is an electronic circuit board,
This electronic circuit board-F is equipped with multiple electronic components such as ICs, so this electronic circuit board is supported on the X-Y tape route, and the subject position is varied by table control. We are trying to image various parts.

(Problems to be Solved by the Invention) For example, a case will be described in which a surface-mounted board is used as the board to be inspected. This type of board will eventually be incorporated into various electronic devices and used.

Incidentally, many of the electronic devices described above have an internal heat source, and therefore, the actual usage environment of a surface mount board incorporated into a chassis having this heat source is considerably higher than room temperature.

By the way, under such high temperatures, defects that do not occur at room temperature may occur.For example, in the case of surface mount boards, component leads are directly attached to the pattern on the surface of the board by soldering, so there may be defects in the solder. When the bubbles are engraved at high temperatures, near bridges and the like often occur between the leads, which can sometimes cause stains.

When inspecting at room temperature, there is a low possibility of detecting such a phenomenon even if the internal structure is not imaged by non-destructive inspection.

In this way, in the past, the board to be inspected was inspected without considering the environment in which it would eventually become a product, so even if the board passed the X-ray inspection, if the board was later incorporated into an electronic device. There were many cases where defects occurred, and the reliability of the test was low.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems, to enable non-destructive inspection using X-rays under temperature conditions close to the actual usage environment, and to improve the reliability of X-ray inspection. The purpose of the present invention is to provide an X-ray inspection device that can perform

[Structure of the Invention] (Means for Solving the Problems) In the present invention, a board to be inspected on which electronic components are mounted is supported on an X-Y table-F, and an X-ray beam is directed from an X-ray source toward the board to be inspected. In an X-ray inspection apparatus for non-destructively testing a substrate to be inspected by emitting radiation and converting an X-ray image that does not pass through the substrate to be inspected, a heating means provided to heat the substrate to be inspected; At least one of the cooling means and the cooling means provided to cool the substrate to be inspected is provided, and the X-ray inspection is performed under temperature conditions depending on the usage environment.

(Function) In the present invention, when performing a non-destructive inspection of a board to be inspected using X-rays, the board to be inspected is heated by a heating means or cooled by a cooling means. It is possible to test under temperature conditions close to those that would occur when the device is incorporated into actual equipment, or under more severe temperature conditions considering the safety factor.
Therefore, when electronic components are supported by soldering, they are often exposed to high temperatures, especially when the leads are directly attached to the surface of the board without inserting the leads into the holes of the board, such as in the case of surface-mounted boards. Defects such as the near bridge phenomenon can be reliably inspected, and defects that occur when the final product is operated in high-temperature or low-temperature environments can also be reliably detected. Test reliability will be greatly improved.

(Example) The present invention will be described below as a non-destructive testing device for electronic circuit boards.
An embodiment applied to a line inspection device will be specifically described with reference to the drawings.

This X-ray inspection device consists of an X-ray generator T as shown in Fig. 2.
X-ray photography is performed by placing a board 20 to be inspected, such as a surface-mounted board, between the X-ray tube 1 of W 10 and an image sensor 40 that detects X-rays. The image sensor 4
An X-ray transmission image can be taken on an X-ray recording medium such as an instant film 200 that can be placed on the front side of the camera.

The X-ray generating section 10 includes the X-ray tube 11 that generates X-rays.
and a high voltage generator 1 that applies a high voltage to this X-ray tube 11.
It is composed of 2. The X-ray tube 11 is equipped with a cathode filament and an anode opposite to the cathode filament in its internal vacuum. By heating the filament, thermionic electrons are accelerated by a high DC voltage and collided with the anode. let me,
The kinetic energy of the thermoelectrons at this time is obtained as X-rays. Note that this X-ray exposure amount can be changed by varying the tube voltage or filament current of the X-ray tube 11.

Furthermore, as the X-ray tube 11, a so-called microfocus X-ray source is employed. In this example, the size of the focal point is 10
A microfocus X-ray source of 0 microns or less, preferably 15 microns or less is used. Such a fine focus can be achieved by causing the thermoelectrons to collide with a microscopic region on the anode, which is the target of the thermoelectrons, and can be achieved by narrowing down the target area 1 to the region using a focusing electrode or the like.

In this embodiment, the board to be inspected 20 is an electronic circuit board on which electronic components such as ICs are mounted on the surface. Multiple sheets are arranged in 10, X-Y stage]
By moving -09, it can be set as an X-ray irradiation area.

In order to convert the X-ray image into an image, the image sensor 40 is provided which inputs X-rays through the substrate 20 to be inspected. Here, in this embodiment, a vidicon is used as the image sensor 40, but this vidicon has a photoconductive surface which is an X-ray input surface or is sensitive to X-rays, and an electrical signal corresponding to the intensity of X-rays is sent. is output.

For example, a variable gain amplifier 50 is provided downstream of the image sensor 40, and is configured to amplify and output the electrical signal with a gain determined to obtain an optimal image.

Further, an image processing section 60 inputs the output of the amplifier 5o.
The image processing unit 6o divides the electric signal into 256 levels or 51 levels for each predetermined level range.
The signal is binarized in two stages, and the binarized gradation signal is subjected to image processing such as edge enhancement and output.

Furthermore, a 'F■ signal processing section 7 is provided after the image processing section 6o.
0 is provided, the digital signal output from the image processing unit 6o is converted into an analog signal, and further processed such as superimposing a synchronization signal to become a TV signal, which is then output to the display 8o at the subsequent stage.
It is possible to display images.

Further, in this embodiment, it is possible to take an X-ray image on film, and for this purpose, the instant film 2o○ can be placed on the mounting table 201. This instant film 200 has a negative and a positive film sealed inside one sheet of film, and at the same time, a liquid agent for developing and fixing is contained wrapped in a soft substance. After photographing on this film, development and fixing are started by pressing the liquid agent, and if it is a black and white film, the image can be recognized in about 15 seconds.

An example of this type of instant film is the film used in Polaroid cameras (trade name), which is also sensitive to the wavelength of X-rays.

In the X-ray inspection apparatus having the above configuration, the orthogonal axis direction on the two-dimensional plane of the X-Y table 100f is X.

If Y is the height direction orthogonal to the X and Y axes, then in this embodiment, the X and Y positions of the substrate to be inspected 20 are
- In addition to being realized by driving the Y-table 100, a Z-direction moving mechanism (not shown) is provided to change the Z-direction position of the instant film 200 and the Z-direction position of the image sensor 40. The shooting magnification can be set to .

Note that since the X-Y stage 109 is set within the X-ray irradiation area, although the base (not shown) that supports the X-Y stage 109 is made of stainless steel, the X-ray passage path is The XY stage 109 is made of a material that easily transmits X-rays, such as aluminum.

Next, the supporting jigs 1 and 10 fixedly supported by the XY stage 109 J: and supporting the substrate to be inspected 2o will be explained with reference to FIG. 3.

The board to be inspected 2o in this embodiment is an electronic circuit board as shown in FIG. 4, and the supporting jig 1]0 is
The frame body 111 has a stepped surface 11.2 on the inner surface, and a rod 114 for regulating the end surface of the substrate 20 in the width direction is hung thereon. By supporting the substrate 20 on the X-Y stage 10
A plurality of substrates 20 can be supported by being parallel to the substrates 9 and partitioned by rods 114.

Next, the characteristic configuration of the device of this embodiment will be explained.
As shown in FIG. 1, the structure includes a heating means 300 for heating the substrate 2° to be inspected to set a desired surface temperature condition. The heating means 300 is composed of, for example, infrared lamps placed on both sides of the image sensor 4o, and is configured to directly heat the surface of the substrate 20 to be inspected.

Then, the heating means 300 heats the substrate 20 to be inspected so that the surface temperature thereof can be maintained at, for example, 30° C. to 506° C. Note that when the temperature of the substrate 20 to be inspected is raised from room temperature to the above temperature using this X-ray inspection apparatus, the deviation will occur because it takes a predetermined time to reach the -12 temperature, so that ρj is It is preferable that the substrate to be inspected 20 be preheated using a constant temperature bath or the like before being transported.

Next, the effect will be explained.

First, when X-ray inspecting the first substrate 2o to be inspected in the inspection lots 1 to 1, teaching of the imaging position and imaging magnification is performed.

- After the initial settings described in V are completed, the X-ray inspection is started, and the X-ray inspection is performed by emitting X-rays from the X-ray tube 11 toward the substrate 20 to be inspected.

In this embodiment, as shown in FIG. 3, a plurality of objects 20 to be processed are mounted on a support jig 110 and an X-ray inspection is performed. First, the substrate to be inspected 20 at the left end of the support jig 110'' is set as the X-ray irradiation area, and thereafter the CPU
2], O reads the position information sequentially according to the pre-programmed flowchart, first controls the execution of the inspection at the first coordinate, then the second coordinate, the third coordinate, etc.
By automatically variably controlling the X and Y positions and imaging magnification of the substrate 20 to be inspected, X-ray inspection can be performed continuously.

In addition, in this embodiment, since a fine focus X-ray source is employed, a large amount of power is not required to increase the X-ray density.

In addition, the characteristic operation of the present embodiment and the supporting jig described in 1- and 1-], ] Of the substrate to be inspected 20 are heated by the heating means 300.
The test board 20 is heated under the most severe temperature conditions when it is incorporated into an actual electronic device and operates, for example, the surface temperature of the test board 20 is set to about 50°C.

Therefore, in the unlikely event that there are air bubbles inside the solder, and these bubbles are exposed to high temperatures,
Due to the expansion, it is possible to detect defects such as the formation of a near bridge due to the expansion of half 1 (-1). , it is possible to prevent defects that may occur when the device is subsequently incorporated into a device and moved. Note that when the heating means 300 is placed further away from the surface of the substrate to be inspected 20 as in this embodiment, In some cases, it is preferable to use an infrared lamp with high heating efficiency.

In addition, when raising the temperature to a temperature considerably higher than room temperature, if this temperature increase is performed inside the X-ray inspection equipment, the inspection throughput will decrease, so it is necessary to preheat the X-ray inspection equipment. If the temperature preheated by the heating means 300 is maintained, the throughput 1~ will not decrease compared to the case of testing at room temperature.

Imaging of the X-ray image is performed as follows.

That is, the X-rays transmitted through the substrate to be inspected 20 are input to the image sensor 40, and an X-ray transmission image is taken by the image sensor 40 here.

At this time, in this embodiment, the χ-ray tube 1, which is an X-ray source with a minute focus,
1, a clear X-ray image without blur can be projected onto the photoconductive surface of the image sensor 40.

That is, as shown in FIG. 4(b), if the focus is not minute, in addition to the original transmitted image A1 of the substrate to be inspected, there will be a blurred image A2 due to the large focus;
As shown in Figure (a), in the case of a minute focus, the substrate to be inspected 2
Since only the X-ray transmission image of 0 is incident on the image sensor 40, a clear image without blurring can be obtained.

The image sensor 40 outputs an electrical signal corresponding to the detected light intensity, and this electrical signal is amplified by the amplifier 50 and then input to the image processing section 60 .

The image processing unit 60 converts the analog electrical signals into 256,512
The digital signal is binarized into gradations such as stages, and various processes are performed on the stages of this digital signal.

Thereafter, this digital signal is input to the TV signal processing section 70 at the subsequent stage, where it is converted into an analog signal and processed into a TV signal on which a synchronization signal etc. are superimposed. By displaying the upper image, an X-ray transmitted image of the substrate 20 to be inspected is converted into an image.

In addition, when using a conventional X-ray source with a large focus as shown in Fig. 4(b), parallel X-rays are emitted from this large focus, so the X-ray fluorescence multiplier tube, etc. It was impossible to perform X-ray photography without using a tube with a large input surface area, but in this example, an X-ray tube 11 with a minute focus is used, so the input surface has a small aperture of several inches, making it possible to perform X-ray photography. image sensor 4 etc.
It can be adopted as 0. In addition, even if the input surface is small in diameter, it can be scanned by moving the X and Y positions of the board 20 to be inspected, or as described above.
By enlarging the imaging magnification of the line image, it becomes possible to photograph the entire electronic component or a portion thereof as desired. moreover,
An X-ray fluorescence multiplier tube is extremely expensive compared to a vidicon, and this embodiment is superior in that the apparatus can be made at a lower cost.

Next, the second substrate 20 to be inspected on the support jig 110 is
X-ray imaging is performed at each coordinate position in the same manner as in the radiation exposure area, and X-ray inspection is performed on all the substrates to be inspected 20 in the support jig 110 in the same manner. Become.

After testing all of the test boards 20 in the support jig 110, replace the test board 20 in the jig 110 with a new test board 20, and then test the same type of test board 20. We will proceed with the X-ray examination.

Incidentally, it is also possible to set the instant film 200 as necessary and take an X-ray transmission image on the instant film 200.

In this way, according to the device of this embodiment, X-ray inspection can be performed under the same temperature conditions as when the board to be inspected is actually installed and operated in electronic equipment. Also, it is possible to reliably find out those that cause defects when placed inside the equipment under high temperature conditions, and the reliability of X-ray inspection can be greatly improved.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible within the scope of the invention.

For example, the means for heating the substrate 20 to be inspected is not limited to an infrared lamp as in the embodiment described above.
Various means have been adopted to heat the substrate 20 to be inspected, and in this case, the method is limited to one that is set at a position separated from the substrate 20 to be inspected via a space, for example, a thin film on the XY stage 109 itself. A tape heater or the like may be arranged to heat the back surface of the substrate by heat transfer.

- In the above embodiment, the inspection was explained in which the object to be inspected was heated to a high temperature, but the object to be inspected was set in a cold atmosphere.
, cold and hot environment inspections may be conducted, or both facilities may be provided and used selectively. The cooling means may be any one of placing liquid nitrogen in an insulated container, providing a cooler, or circulating a cooling medium through a refrigerant pipe.

Alternatively, the surface temperature of the substrate 20 may be detected by a sensor such as a thermocouple, and X-ray irradiation may be performed when a predetermined temperature is reached.

[Effects of the Invention] As explained above, according to the present invention, the substrate to be inspected is subjected to X
Since the X-ray inspection can be performed, defects that are likely to occur after the board to be inspected is incorporated into an electronic device can be discovered beforehand, and the 18 fj characteristics of the X-ray inspection can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an example of heating means for a substrate to be inspected to explain an embodiment of the apparatus of the present invention, and FIG. 2 is an X-ray diagram of an electronic circuit board, which is the object to be inspected in FIG. FIG. 3 is a schematic explanatory diagram for explaining one embodiment applied to inspection, and FIG. b) is a schematic explanatory diagram for explaining the fine focus of FIG. 1 and the conventional X-ray transmission image. 11... X-ray generation source, 20... Board to be inspected, 300... Heating means. Agent: Patent Attorney To I (and 1 other person) Mr. Mitsudo, Section X

Claims (1)

[Claims] A board to be inspected on which electronic components are mounted is supported on an X-Y table, and an X-ray source emits X-rays toward the board to be inspected. An X-ray inspection apparatus that non-destructively inspects a board to be inspected by converting a line image into an image includes a heating means provided to heat the board to be inspected, and a cooling means provided to cool the board to be inspected. An X-ray inspection apparatus characterized in that at least one of the means is provided to perform the above-mentioned X-ray inspection under temperature conditions depending on the usage environment.