JPH03199947A - Inspection of soldered part and apparatus therefor, and inspection of electronic component mounting state - Google Patents

Abstract

PURPOSE:To make it possible to detect the defect of a bridge by inputting a light beam from the direction so that a region between the rear side of an electronic component and a circuit board can be observed, and detecting the passableness of the region from the outputting direction of the light. CONSTITUTION:The laser light is emitted from a laser light source 3 to an IC chip 2 whose position is determined at an inspecting position. The laser light is incident on the existing region of soldered parts 16 between the chip 2 and a ceramic substrate 1 through lenses 4a and 4b and a prism 5a. The laser light part which has passed through the region is made incident into a line sensor 8 through a prism 5b, a lens 4c and a galvano-mirror 6a. An image sensing control circuit 12 rotates and controls the mirror 6a with a motor 7a under the instruction of a total control part 11. The laser light is detected with the sensor 8 in synchronization with the control. The signal is stored in an image memory 13 as the two-dimensional image at a line unit. A defect decision part 14 which is actuated with the control part when the image detection is finished decides the presence or absence of the defective part of the bridge in the detected image.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an inspection method and an inspection device for inspecting a soldered portion connecting an electronic component and a circuit board, and furthermore, an inspection method using the inspection method. The present invention relates to an electronic component mounting state inspection method.

[Prior Art] Generally, various electronic components are connected to circuit boards by soldering, but bridge defects are one of the defects that typically occur in soldered parts. ing. A bridge defect is a defect when a soldered part is electrically connected to an adjacent soldered part by solder, and Figures 13(a) and 13(b) show flat package type electronic components and pin type electronic components, respectively. This figure shows an example of a bridge defect in a soldered part of an electronic component.

Up to now, in the inspection for bridge defects, an image of the soldered portion is detected from above the circuit board, and defects are detected by analyzing the detected image. For example, if the soldering area is illuminated in a negative direction from the surrounding area, the soldering area and its surrounding area may be
If the image is captured by the V left camera, the area where the solder area exists can be detected from the image since the illumination light is strongly reflected at the solder area.Therefore, by analyzing that area, the presence or absence of a bridge can be easily determined. It has become possible.

In addition to the above, there is a method described in Japanese Patent Application Laid-open No. 131409/1983 that detects defective solder lines on a printed circuit board with good accuracy without using any kind of illumination from the surroundings. It is being In this case, excitation light is irradiated to the soldered parts on the printed circuit board,
Lead misalignment and bridge defects are detected by detecting a silhouette image of the soldered area using fluorescence generated from the printed circuit board and analyzing the image.

[Problems to be Solved by the Invention] However, in the conventional technology, soldered parts are inspected by optically detecting solder images from above the circuit board. cannot be applied.

This is because when an electronic component is connected to a circuit board by a soldered part interposed between the back side of the part and the circuit board, the soldered part to be inspected is hidden behind the electronic component. This is because the shape of the solder material cannot be detected from above the circuit board. To explain this situation in more detail, FIG. 14 shows an example of a circuit board on which such electronic components are mounted, and FIG. 15 shows a partial cross section thereof.

As shown in the figure, an IC chip 2 is directly connected to a ceramic substrate 1 through minute soldering parts 16 arranged in a grid pattern. Although there is a possibility that a bridge defect 15C may occur, it is actually difficult to observe that portion from the outside, and therefore, the conventional technology cannot be applied as is. In FIG. 15, reference numeral 17 indicates a wiring conductor within the ceramic substrate 1, one end of which is connected to the soldered portion 16.

An object of the present invention is to make it possible to easily detect bridging defects at the soldered portion when an electronic component is connected to a circuit board by a soldered portion interposed between the back side of the component and the circuit board. The present invention provides a method for inspecting soldered joints.

Another object of the present invention is to provide a method for inspecting the mounting state of electronic components, which can inspect the mounting state of electronic components using the method for inspecting soldered parts.

Furthermore, another object of the present invention is to prevent bridging defects from easily occurring at the soldering part when an electronic component is connected to a circuit board by a soldering part interposed between the back surface of the component and the circuit board. To provide a soldering part inspection device capable of detecting soldered parts.

[Means for Solving the Problems] The above object is to allow a light beam to enter the soldering part intervening area between the back surface of an electronic component and a circuit board from a direction that allows the area to be seen, and at the same time, the light beam to This is achieved by detecting whether or not the light beam can pass through the intervening region based on the direction in which the light beam is emitted. 7- Another object of the present invention is to inspect the mounting states of electronic components of various mounting types mounted on a circuit board according to the mounting type, by inspecting the mounting state of the electronic components mounted on the circuit board. This is achieved by inspecting the mounting state of electronic components mounted on a circuit board by soldering parts using the above soldering part inspection method.

Furthermore, another object of the present invention is to provide a light beam incident means for allowing a beam of light to enter a soldering part intervening area between the back surface of an electronic component and a circuit board from a direction that allows the area to be seen; A light beam detection means for detecting the passing light beam from the direction of the light beam emission, and a defect determination means for determining the presence or absence of solder between adjacent solder material parts by analyzing the optical path detection result from the light beam detection means. This can be achieved by comprising a control means that performs a series of soldered portion inspections on electronic components by controlling each of the above-mentioned means.

[Operation] When an electronic component is connected to a circuit board by a soldering section interposed between the back side of the component and the circuit board, the state of connection of the electronic component to the circuit board by the soldering section is Although it cannot be seen from above the board, it can be seen from the side by an appropriate method. In other words, a small gap exists between the electronic component and the circuit board as a soldering area, but if a beam of light is incident on this gap, the beam will not pass through the soldering area or the area where solder is present. Even if they are blocked, parts where they do not exist will still pass through.

Therefore, if the passing position and non-passing position of the light beam with respect to the electronic component are known in advance from the design information,
If the ray that should be detected at the passing position is not detected,
It can be determined that solder exists in the optical path as a bridge defect.

In addition, after various mounting types of electronic components are mounted on a circuit board, the mounting status of the electronic components may be inspected for each mounting type. The mounting state of electronic components mounted on a circuit board using soldered parts can be easily inspected by using the above method.

Therefore, as a soldering part inspection device in which the soldering part inspection method is actually carried out, a light beam is incident on at least the interposed area of the soldered part between the back side of the electronic component and the circuit board from a direction that allows the area to be seen. A light beam incident means for detecting the soldering portion, a light beam detection means for detecting the light beam passing through the soldering part intervening area from the direction of the light beam emission, and an analysis of the optical path detection result from the light beam detection means. It is only necessary to include a defect determining means for determining the presence or absence of solder between the parts, and a control means for performing a series of soldered portion inspections on the electronic component by controlling each of the above-mentioned means.

[Example] The present invention will be explained below with reference to FIGS. 1 to 12.

First, the soldering part inspection device according to the first embodiment will be explained. Fig. 1 shows its configuration, and Fig. 2 shows the configuration of the optical system and the state of the optical path at that time. . As shown in the figure, (a plurality of) IC chips 2 are mounted or connected on a ceramic substrate 1 by a large number of minute spherical solder parts 16 arranged on a grid.
The ceramic substrate 1 on which the C chip 2 is mounted is x, y, z
It is fixed in a positioned state on a stage 9 which can be moved and rotated in the direction. In this state, the overall control section 11 drives the stage 9 as desired via the stage drive circuit IO according to the flow shown in FIG. 5, whereby any IC 2 to be inspected is positioned at the inspection position. At the inspection position, prisms 5a and 5b are located on both sides of the IC2.

Now, if the laser light source 3 emits a laser beam with the IC chip 2 positioned at the inspection position, the laser beam is converted into wide parallel light by the lenses 4a and 4b, and then the prism 5a In addition to being reflected by
The beam is made to be incident on the soldering part intervening area (hereinafter simply referred to as the 1-soldering area) existing between the IC chip 2 and the ceramic substrate 1. In this way, the passage of the laser beam incident on the solder area is partially blocked by the solder material 16 existing in the optical path and the solder as a bridge defect. The laser beam portion that has passed through is once reflected by the prism 5b and then detected by the line sensor 8 via the lens 4c and galvanometer mirror 6a. At that time, as shown in Figure 2,
The optical path of the laser beam detected by the line sensor 8 can be selected by the rotational position of the galvanometer mirror 6a rotated by the motor 7a. Therefore, if the imaging control circuit 12 controls the rotation of the galvano mirror 6a based on the instruction from the overall control unit 11 and detects the laser beam with the line sensor 8 in synchronization with the rotation control, the detection signal will be transmitted line by line. A two-dimensional image is obtained by sequentially storing the images in the image memory 13. The two-dimensional image obtained in this way is obtained by projecting the solder area using parallel light, but in this two-dimensional image,
2 Solder material portions 1 of substantially the same shape arranged in a grid pattern
6 is detected as a row of solder parts that are parallel to the incident laser beam and are all overlapped row by row.As a result, the two-dimensional image is obtained as a silhouette image as shown in Figure 3. It is something that can be done. At that time, if there is even one solder defect, that is, a bridge defect, at the laser beam passing position between the rows of solder material parts, a connected solder image is detected as shown by reference numeral 18 in the silhouette image shown in FIG. It is something that will be done.

Here, if we go back to the previous explanation and continue the explanation again, when the image detection is completed, the defect determination unit 14 activated by the overall control unit 11 determines whether or not a bridge defect exists in the detected image. is now being determined. When determining the presence or absence of a defect, the detected image is first binarized using an appropriately set threshold value to obtain a binary image. For example, on a binary image, solder or solder material parts are binarized as "0", and areas where these do not exist are binarized as [moon]. Thereafter, based on the design information about the solder material part 16 stored in advance in the defect determination section 14, a window 19a-1 is displayed in the binary image as shown in FIG.
9d is set. The set positions of these windows 19a to 19d are naturally located between the rows of solder material parts.

Now, when the windows 19a to 19d are set as described above, the areas of pixels whose value is "0" are totaled within each of the windows 19a to 19d, but the total value is not determined in advance. If the threshold value is greater than or equal to the threshold value, it is determined that a bridge defect exists within that window.

In the example shown in FIG. 4, it is determined that a bridge defect exists within the window 19c.

The overall control unit 11 sequentially performs the inspection operation described above for each of all the IC chips 2 mounted on the ceramic substrate 1 according to the flow shown in FIG.
After the inspection of each chip 2 is completed, the ceramic substrate 1 is rotated 90 degrees and all IC chips 2 are inspected again.
Similar tests are performed on each of them in turn. This is because inspection from only one direction cannot detect bridging defects that occur between adjacent soldered parts of multiple soldered parts in the same row that are parallel to the incident laser beam. That's because you don't get it. In the overall control section 11,
Waiting for the inspection from two directions to be completed, the presence or absence of a bridge defect will be reported. If a defect exists, the location of the IC chip 2 related to the defect and the defect in this IC chip 2 will be reported. The location is also reported. Of course, if a bridge defect is detected in any IC chip 2, it is also possible to terminate the inspection process at that point.

As described above, in the first embodiment, since the projected image of the solder area is first stored in the image memory as a two-dimensional image, the defect shape is can be easily and directly confirmed.

Next, to explain the solder material inspection device according to the second embodiment, FIG. 6 shows its configuration, and FIGS. 5-7 show the configuration of the optical system and the state of the optical path at that time. It is something. As shown in Figures 6 and 7, the only difference in the structure of the optical system is that no galvanometer mirror is provided.
This embodiment is substantially different from that of the previous embodiment. In the first embodiment, the laser beam passing through the solder area was detected line by line while controlling the rotation of the galvanometer mirror.
In this embodiment, the line sensor 8 detects the light that is collectively focused by the lens 4C. As a result, the detected value by the line sensor 8 becomes as shown in FIG. 8, which is equivalent to the result obtained by vertically integrating the pixel values in the two-dimensional image shown in FIG. 3. The detection value from the line sensor 8 is processed in a manner similar to that of the first embodiment to determine the presence or absence of a bridge defect. That is, as shown in FIG. 8, one-dimensional windows 19e to 1
9h is set, and the presence or absence of a bridge defect can be determined by determining whether or not the detected values within each of the windows 19e to 19h are greater than or equal to the threshold value. In the example shown in FIG. 8, since the detected value in window 19g has not reached the threshold, window 19g
It can be determined that a bridge defect exists at the corresponding position.

In the case of the second embodiment described above, since the detected image is one-dimensional and not detected as a two-dimensional image, scanning with a galvanometer mirror and storing the image in the image memory are unnecessary, and the configuration is simple. This means that inspection can be carried out at high speed.

Continuing to explain the third embodiment, although the optical system and image capturing method are different in this embodiment compared to the first embodiment, the overall inspection procedure and the processing method for detected images are almost the same. ing.

That is, in this embodiment, the solder area is two-dimensionally scanned by a laser beam with a small spot diameter, and an image is detected two-dimensionally in synchronization with this scanning. As shown in FIGS. 9 and 10, the laser light from the laser light source 3 is transmitted through galvano mirrors 6b and 6c and a lens 4d.
, 4e, and is reflected by the prism 5a in the direction of the solder area. At that time, the galvano mirrors 6b and 6c are driven by motors 7b and 7, respectively.
When rotated by c, the solder area is two-dimensionally scanned over the entire solder area. The laser beam passed through the solder area is transmitted through the prism 5b.
It is reflected by the light guide 20 and the photomultiple (
The photomultiplier tube) 21 performs photoelectric conversion and obtains an electrical signal, but this electrical signal is sequentially stored in the image memory 13 in synchronization with the scanning of the laser beam, resulting in the same result as in the first embodiment. A two-dimensional image is obtained and processed in the same way.

In the case of this embodiment, since the laser light incident on the solder region is focused into a narrow beam, the first. Compared to the second embodiment, the influence of laser beam reflection within the solder region is smaller, and therefore bridge defects at the soldered portion can be detected with high accuracy.

Finally, the fourth embodiment will be explained with reference to FIGS. 11 and 12. The situation is similar to that of the third embodiment, except that the laser beam incident on the solder area is slit-shaped. It becomes. The laser beam from the laser light source 3 is first converted into a slit shape by lenses 4f and 4g, and then is reflected by a prism 5a in the direction of the solder area via a galvanometer mirror 6b and a lens 4h. As shown in FIG. 12, at that time, the laser beam is incident on the solder area as a vertically long slit-shaped beam, but due to the rotation of the galvanometer mirror 6b, the slit-shaped laser beam illuminates the solder area one-dimensionally. This is what will be scanned. The laser beam passed through the solder area is
After being detected one-dimensionally in synchronization with laser beam scanning by an optical system similar to that in the second embodiment, processing is performed in the same manner as in the second embodiment.

In the case of this fourth embodiment, the influence of laser beam reflection within the solder region can be suppressed to a small level as in the case of the third embodiment, and the structure is simple as in the case of the third embodiment. , inspection can also be performed at high speed.

The method and apparatus for inspecting soldered joints have been described above using various examples. However, the incidence of laser light on the solder area and the detection of the laser beam through the solder area are limited to the various examples described above. If this is done properly, bridge defects in soldered parts will be detected with good accuracy. However, such a soldering part inspection method and its equipment cannot be used when all electronic components are mounted on a circuit board.
It can also be used to detect the mounting status of electronic components of a specific mounting type on a circuit board. The mounting state referred to herein does not refer to the mounting position, orientation (rotation state), polar direction, etc. of the electronic component in the mounted state, but mainly relates to the state of soldering. It is necessary to reliably mount a unit electronic component onto a circuit board using each of the multiple soldering points, but in this case, there may be cases where the connection at a certain soldering point is poor (including cases where there is no connection at all, or bridge defects). )
If so, it can also be used to detect defects. Among these defects, the method for detecting bridge defects has already been described, but if there is no connection at all at a certain soldered part, there is Since there is a gap between the bottom end and the circuit board, the idea is to detect that gap through image processing as well. Since light beams can pass through these gaps, if the detected image is appropriately processed, these gaps can be detected along with the bridge defect.

[Effects of the Invention] As explained above, in the case of claims 1 to 5, when an electronic component is connected to a circuit board by a soldering part interposed between the back surface of the component and the circuit board, , bridge defects in soldered parts can be easily detected, and in the case according to claim 6, the mounting state of electronic components of a specific mounting type can be inspected using the soldered part inspection method, Furthermore, according to claim 7, when an electronic component is connected to a circuit board by a soldering portion interposed between the back surface of the component and the circuit board, a bridging defect at the soldering portion can be easily detected. This results in a soldering part inspection device that is rated as acceptable.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a first embodiment of the soldering part inspection device according to the present invention, FIG. 2 is a diagram showing the configuration of the optical system and the optical path in the embodiment, and FIG. 4 is a diagram for explaining the processing contents for the detected image in the same example, and FIG. 5 is a diagram for explaining the processing contents for the detected image in the same example, and FIG. FIG. 6 is a diagram showing the configuration of a second embodiment of the soldering part inspection device according to the present invention, and FIG. FIG. 8 is a diagram showing the configuration of the system and the state of the optical path. FIG. 8 is a diagram for explaining the processing contents for the detected image in the same embodiment. FIG. FIG. 10 is a diagram showing the configuration of the optical system and the state of the optical path in the embodiment, and FIG. 11 is a diagram showing the fourth embodiment of the soldering part inspection device according to the present invention. FIG. 12 is a diagram showing the configuration of an example, and FIG. 12 is a diagram showing the configuration of the optical system and the state of the optical path in the example.
13(a) and 13(b) are diagrams for explaining a bridge defect, and FIGS. 14 and 15 are diagrams for explaining a bridge defect that occurs in a specific mounting type of electronic component. ■... Ceramic substrate, 2... IC chip, 3...
・Laser light source, 4a to 4e...Lens, 5a, 5
b... Prism, 6a-6c... Galvano mirror 1
7a-7c...Motor, 8...Linear sensor, 9.
...Stage, 10...Stage drive circuit, 11...
- Overall control section, 12... Imaging control circuit, 13... Image memory, 14... Defect determination section, 16... Soldering section, 20... Light guide, 21... Photomultiple (
photomultiplier tube)

Claims (7)

[Claims] 1. A method for inspecting a soldered joint when an electronic component is connected to a circuit board by a soldered joint interposed between the back side of the electronic component and the circuit board, the method comprising: A light beam is incident on the soldering part intervening area from a direction that allows the area to be seen, and whether or not the light ray can pass through the soldering part intervening area is detected from the light emitting direction. A method for inspecting a soldered part in which it is determined whether or not a soldered part exists in an optical path connecting points. 2. The light beam is incident on the entire soldering part intervening area as a wide parallel beam, and whether or not the light ray can pass through the soldering part intervening area is detected and processed as a two-dimensional image from the direction in which the light ray is emitted. 2. The method for inspecting a soldered part according to claim 1. 3. The light beam is incident on the entire soldering part intervening area as a wide parallel beam, and whether or not the light ray can pass through the soldering part intervening area is detected and processed one-dimensionally as an image from the direction of the light ray emission. 2. The method for inspecting a soldered part according to claim 1. 4. The light beam enters the soldering part intervening area as a beam with a small spot diameter in order to two-dimensionally scan the area, and whether or not the light ray can pass through the soldering part intervening area is determined by the scanning from the light emitting direction. 2. The soldered part inspection method according to claim 1, wherein the soldered part inspection method is detected and processed two-dimensionally as an image in synchronization with . 5. The light beam enters the soldering part intervening area as a slit-shaped beam in order to one-dimensionally scan the area, and whether or not the light ray can pass through the soldering part intervening area is determined from the direction in which the light ray comes out in synchronization with the scanning. 2. The soldered portion inspection method according to claim 1, wherein the soldered portion is detected and processed one-dimensionally as an image. 6. An electronic component mounting state inspection method for inspecting the mounting state of various mounting types of electronic components mounted on a circuit board, the method of inspecting the mounting state of each electronic component mounted on a circuit board by mounting type. In this case, claims 1 to 4 apply to electronic components mounted on a circuit board by means of a soldering portion interposed between the back surface of the component and the circuit board.
An electronic component mounting state inspection method in which the mounting state is inspected by the soldered part inspection method according to any one of the above. 7. A soldering part inspection device for the case where an electronic component is connected to a circuit board by a soldering part interposed between the back surface of the component and the circuit board, a light beam incident means for causing a light beam to enter the soldering part intervening region from a direction that allows the region to be seen; a light beam detecting means for detecting the light beam that has passed through the soldering part intervening region from the direction in which the light beam is emitted; Defect determination means for determining the presence or absence of solder between adjacent soldering parts by analyzing the optical path detection results from the means; 1. A soldering part inspection device comprising a control means for inspecting a soldering part.