JPH0310151A - Object inspection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Application Fields Prior Art (Figs. 9 to 11) Problems to be Solved by the Invention Examples of Means and Actions for Solving the Problems Explanation of the Principle of the Invention (Fig. 1 to 7) One embodiment of the present invention (Fig. 8) Effects of the invention [Summary] Regarding an object inspection device that detects the three-dimensional state of an object to be measured using X-rays, The purpose of the present invention is to provide an object inspection device that is capable of contact, non-destructive, high-speed, and highly accurate detection, and includes an A detection means 42 for detecting X-rays transmitted through the object, a distance detection means 68 for detecting the distance between the inspection point and the X-ray source, and a movement means 56 for moving the object to be measured 52 at a predetermined speed. , storage means 70 to 73 for storing image signals corresponding to the X-rays detected by the detection means 42, and the distance detection means 6.
Extracting means for extracting the image signals corresponding to the X-rays that have passed through the inspection point of the object to be measured 52 from different directions from among the image signals stored in the storage means 70 to 73 based on the output of 8. 74, and an inspection means 76 for inspecting the inspection point of the object to be measured based on the maximum value of the image signals of the same inspection point extracted by the extraction means 74.

[Industrial Application Field] The present invention relates to an object inspection device, and more particularly, to an object inspection device that detects the three-dimensional state of an object to be measured using X-rays.

As the speed of electronic computers continues to increase, it has become necessary to know not only the external appearance but also the internal state of an object when inspecting electronic components. For example, in electronic computers,
Ceramic substrates are increasingly being used in place of conventional plastics. In this manufacturing process, it is necessary to inspect the inside of the electrically conductive hole (hereinafter referred to as via hole (IA HOLE)) formed in the ceramic substrate.

[Conventional technology]

A ceramic multilayer board is manufactured by laminating a plurality of green sheets and sintering them. Via holes are provided to provide electrical continuity between each layer, and as shown in Figure 9, via holes 1.2 are made by drilling a through hole 4 in the green sheet 3 and filling it with copper paste. It is. The conditions necessary for the via hole are to ensure continuity between each layer.
As in via hole 2 shown in Fig. 9, the copper paste has reached the surface of the base material.
For example, there is a This defect cannot be detected unless you know the internal condition, not the external appearance.

Another field is the internal solder inspection of surface-mounted printed circuit boards. Visual inspection of solder has traditionally been performed visually, but as surface mounting technology advances, soldering is now performed behind the leads, making visual inspection difficult. For example, as shown in FIG.
．． The presence or absence of solder on the back side of IC pin 7 cannot be detected just by looking from above.
The IC pin 7 shows a defective one in which the solder was not attached. In such fields,
It is necessary to measure the object behind the object.

Conventionally, therefore, a method has been adopted in which an X-ray source is provided outside the object, the transmitted X-rays are detected by an X-ray camera, and the presence or absence of solder or the amount thereof is measured based on the amount of transmitted X-rays.

[Problems to be Solved by the Invention] However, since such conventional object inspection devices simply use X-rays,
Object to be inspected (printed wiring board) as shown in Figure 1
If there is solder 9 on the back side of the solder 9, even if you try to transmit X-rays 10.11 and detect the amount of transmitted X-rays with an X-ray camera 12.13, the amount of transmitted X-rays will be the same as in the normal case, so you can determine whether it is defective or normal. The problem was that it was not possible.

Therefore, an object of the present invention is to provide an object inspection device that can detect the three-dimensional state of an object to be measured in a non-contact, non-destructive manner, at high speed and with high precision, without being affected by objects that are not the object of inspection. There is.

[Means to solve the problem]

In order to achieve the above object, the object inspection apparatus according to the present invention includes an X-ray source 41 that emits X-rays that transmit X-rays to an object to be measured 52 having an inspection location, and an X-ray source that emits Detection means 42 for detecting, the inspection location and the X
a distance detecting means 68 for detecting the distance to the radiation source; a moving means 56 for moving the object to be measured 52 at a predetermined speed;
Among the storage means 70 to 73 for storing image signals corresponding to the X-rays detected by the detection means 42, and the image signals stored by the storage means 70 to 73 based on the output of the distance detection means 68, , the object to be measured 52
an extraction means 74 for extracting the image signals corresponding to the X-rays that have passed through the inspection area from different directions;
and an inspection means 76 for inspecting the inspection location of the object to be measured based on the maximum value of the image signals of the same inspection location extracted in step 4.

[Effect]

In the present invention, an object to be measured placed between an X-ray source and a detection means for detecting X-rays is moved at a predetermined speed by a moving means, and X-rays are applied to the inspection point of the object to be measured from different directions. irradiated. Then, only image signals detected from different directions of the inspection location are extracted, and based on the maximum value, it is determined whether or not there is a defect at the inspection location of the object to be measured.

Therefore, even if there is solder, etc. outside the inspection area, the amount of X-ray transmission at the target inspection area can be obtained without being affected by the solder, etc., and the inspection area of the object to be measured can be quickly and accurately The presence or absence of defects can be inspected.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

The present invention, when inspecting voids inside an object, irradiates the area to be inspected from multiple directions depending on the amount of X detection transmission, and is not affected by the back side of each amount of transmission. It attempts to select only the signals.

1 to 7 are diagrams for explaining the present invention in detail.

Hereinafter, the present invention will be described in detail using an example of solder measurement. In FIG. 1, 21 is a surface mount printed board;
22 is, for example, a copper lead, 23.24 is solder applied to the back pattern of the surface mount printed board 21, 25.26.
27 is a part. First, X-ray @, (a - d) 31~
34 and detectors 35 to 38 are installed.

Among the signals detected by each of the detectors 35 to 38, the maximum value can be regarded as a signal that is not affected by tails. In other words, if there is solder 23, 24 or parts 25 to 25 on the back of the surface mount printed board 21,
27, the X-rays are absorbed there and the transmission becomes small. Therefore, each X-ray source (a-d) 31~
Among the transmission amounts from 34, the maximum value is unaffected by the back pattern. In order to achieve this, the first
By setting multiple irradiation angles as shown in the figure, it is possible to install the irradiation beam so that it passes through only the solder on the front side. Here, when the irradiation angle is different, the length of the transmission through the copper lead 22 is different, but compared to solder, copper absorbs about 1/1 the amount of X-rays.
10, so its effect can be ignored (see Table 1)
.

Table 1 The present invention attempts to realize the above principle using one X-ray source and one X-ray camera. That is, as shown in FIG. 2, one two-dimensional X-ray detector (detection means) 42 is provided for one X-ray source 41, and a printed board (object to be measured) 43 to be inspected is moved at a constant speed. When moving, each point receives irradiation from a different direction. For example, as shown in Figure 3, the point you want to observe (inspection location) 4
4 moves as 1.2.3.4, the back pattern 45 also moves at the same time. When the transmitted image is detected in each of these cases, the back and front patterns can be separated only in case 4.

The configuration shown in FIG. 2 requires a frame memory for storing each screen and a circuit for calculating and reading out the amount of transmission at the same point from each screen. Figure 4 is a block diagram showing the concept.
In this figure, the detected image signal that detects the amount of X-rays transmitted through each point 1 to 4 is input to the maximum value detection circuit 47 via the image signal selector 46, and the maximum value detection circuit 47
The maximum value of ~4 points is detected. The detected maximum value (in this example, the value in the case of 4) is used to calculate the amount of transmission at the same point by the transmittance determination circuit 48, and the determination circuit 49 calculates the distribution of the amount of X-ray transmission on the surface to determine the presence or absence of defects. It is determined.

Also, as shown in FIG. 5, the image positions are different on the front and back sides of the printed board 43, so if you select the locations for the front and back sides, as shown in FIG. It can be measured.

In this measurement, it is important to measure the distance between the X-ray source 41 and the object to be measured (printed board 43).

That is, as shown in FIGS. 7(a) and (b), X-ray '6
When the distance between 1.41 and the object to be measured changes to h', the distance between the inspection point 44 and the normal line between the X-ray source 41 and the object to be measured also changes from d to d'. Therefore, it is necessary to measure the distance between the X-ray source 41 and the inspection point 44 using an optical method.

Hereinafter, embodiments will be described based on the above basic principle. 8th
The figure is a diagram showing an embodiment of the object inspection apparatus according to the present invention, and the same components as those in the explanation of the principle shown in FIGS. 1 to 7 are given the same numbers.

In FIG. 8, 51 is an object internal observation device (object inspection device), 52 is a printed board (object to be measured) to which parts 53 to 55 are attached, and 56 is mounted with the printed board 52,
It is a moving table (moving means) movable in the X-Y axis directions. On the other hand, 57 is a laser, and the light beam (laser light) from the laser 57 passes through lenses 58 and 59 and is reflected by a rotating mirror 60, and then enters an illumination objective lens 61, and is directed onto the print temporary 52 in the form of a diagonal line. irradiate. After the reflected light from the printed board 52 passes through a detection objective lens 61, it is imaged by a beam splitter 63 onto photodetectors 64 and 65. Photodetector 64.65
For example, a CCD or a TV camera is used. The images detected by the photodetectors 64 and 65 are A/D converted by an A/D converter (not shown) and input to the height detection circuit 66. The height detection circuit 66 detects the height of the printed board 52 based on the input detection image, and the detection signal is input to the base material height detection circuit 67, and the location to be detected by the base material height detection circuit 67 The height of is detected. The laser 57, lens 58, 59, rotating mirror 60, illumination objective lens 61, detection objective lens 62, beam splitter 63, photodetector 64, 65, height detection circuit 66, and base material height detection circuit 67 as a whole A distance detection means 68 is configured.

The image output detected by the X-ray detector 42 is input to an amplifier 69, amplified by the amplifier 69, and temporarily stored in frame memories (storage means) 70-73. The image output stored in each frame memory 70 to 73 is manually input to an address selection circuit (extraction means) 74, and the address selection circuit 74
is the inspection target detected by the base material height detection circuit 67 and
The coordinates of the part to be detected are calculated based on the distance data with respect to the radiation source 41, and the observed value of the corresponding address is read from each frame memory 70-73. The read observed values are input to the X-ray cross-sectional image processing circuit 75, and the X-ray cross-sectional image processing circuit 75 determines the largest amount of transmission among the observed values. The determination result is input to a defect determination circuit (inspection means) 76, which compares the maximum amount of transmission with a predetermined value, and if the amount of transmission falls outside a certain tolerance range from the predetermined value, it is determined to be a defect. It is determined that

Next, the effect will be explained.

The X-ray source 41 irradiates the printed board 52 with X-rays from above, and the moving table 56 is moved in a predetermined direction at a constant speed. On the detection side, an X-ray detector 42 is placed below the printed board 52 to detect the amount of transmitted X-rays. The detected signals are amplified by an amplifier 69 and then input to frame memories 70 to 73, where they are sequentially stored.

On the other hand, the distance between the inspection object and the X-ray source 41 is measured by an optical method (triangulation method) by the distance detection means 68, and based on this result, the coordinates of the part to be detected are calculated by the address selection circuit 74. The observed values are read out from each frame memory 70-73. Then, the largest amount of transmission among those values becomes the amount of X-ray transmission at that coordinate. Next, the defect determination circuit 76 compares the amount of transmission with a predetermined amount of transmission, and if the amount of transmission is larger than the predetermined value, it is determined that there is a defect.

As described above, in this embodiment, even if there is solder, parts, etc. on the back side of the object to be inspected, defects can be reliably determined only at the inspection location without being affected by these parts. Using one X-ray source 41 and one X-ray detector 42, the three-dimensional state of a plate-shaped object can be detected at high speed and with high precision.

In this embodiment, the presence or absence of defects in the solder on the printed board 52 is determined, but it goes without saying that the present invention is applicable not only to the solder on the printed board 52 but also to the inspection of via holes in ceramic substrates.

〔Effect of the invention〕

According to the present invention, it is possible to realize an object inspection device that can detect the three-dimensional state of a measured object in a non-contact, non-destructive manner at high speed and with high precision without being affected by objects not to be inspected.

[Brief explanation of the drawing]

Figures 1 to 7 are diagrams for explaining the present invention in detail, Figure 1 is a diagram explaining its principle, and Figure 2 is a diagram showing the case where it is realized using one X-ray source and one X-ray camera. Figure 3 is a diagram explaining the principle, Figure 4 is a block configuration diagram, Figure 5 is a diagram explaining the principle when detecting images on the front and back sides of the printed board, and Figure 6 is a diagram explaining the principle. FIG. 5 is a diagram showing a detection screen detected as shown in FIG. 7. FIG. 7 is a diagram for explaining the distance between the X-ray source and the object to be inspected. FIG. 8 is a diagram showing an embodiment of the object inspection device according to the present invention. Overall configuration diagram, Figures 9 to 11 are diagrams showing a conventional object inspection device, Figure 9 is a diagram showing the state of the via hole, and Figure 10 is a diagram for explaining the state of solder adhesion, FIG. 11 is a diagram for explaining the problem. 21...Surface mount printed board, 22...
・I same type lead, 23.24...Solder, 25-27...Parts, 31-34...X-ray source, 35-38...Detection 41...X-ray source, 42...X-ray detector (detection means), 43...
...Printed board (object to be measured), 44...
Point to be observed (inspection location), 45...Back pattern, 46...Image signal selector, 47...Maximum value detection circuit, 48...Transmittance Determination circuit, 49... Discrimination circuit, 51... Object internal observation device (object inspection device),
52...Printed board (object to be measured), 53~
55... Parts, 56... Moving table (moving means), 57...
... Laser, 58.59 ... Lens, 60 ... Rotating mirror 61 ... Objective lens for irradiation, 62 ... Objective lens for detection, 63...Beam splitter, 64.65...Photodetector, 66...
... Height detection circuit, 67 ... Base material height detection circuit, 68 ... Distance detection means, 69 ... Amplifier, 70 to 73 ...・Frame memory (storage means),
74...Address selection circuit (extraction means), 75
......X-ray cross-sectional image processing circuit, 76...
Defect discrimination circuit (inspection means) Fig. Fig. Fig. 5 An explanatory diagram of the principle of detecting the front and back images of the temporary print of the present invention! , 2.3.4 One upper surface (same address) 1', 2', 3', 4' One lower surface (one address) Figure 6 shows the detection screen drawn out according to Figure 5 of the principle explanation 7 Figure 0 Diagram showing the state of conventional via holes

Claims (1)

[Claims] An X-ray source (41) that emits and transmits X-rays to an object to be measured (52) having an inspection location, and a detection means (41) that detects the X-rays that have passed through the object to be measured (52).
42), distance detection means (68) for detecting the distance between the inspection point and the X-ray source, moving means (56) for moving the object to be measured (52) at a predetermined speed, and the detection means storage means (70) to (73) for storing image signals corresponding to the X-rays detected by (42); and storage means (70) to (73) based on the output of the distance detection means (68). extracting means (74) for extracting the image signals corresponding to X-rays that have passed through the inspection point of the object to be measured (52) from different directions from among the image signals stored by the method; An object inspection device comprising: inspection means (76) for inspecting the inspection location of the object to be measured based on the maximum value of the image signals of the same inspection location extracted by ).