JPH04213076A - Soldering inspecting apparatus - Google Patents

Abstract

PURPOSE:To widen a dynamic range by omitting the absorption of X rays in lead pin parts of a soldering inspecting apparatus for inspecting a surface mounted parts which is not soldered yet. CONSTITUTION:A semiconductor element 4 having a plurality of lead pins 41 is soldered and mounted on a board 5, and a mounted part 6 is obtained. In a soldering inspecting apparatus, X-ray beam is cast on the mounted part 6, and a soldered part 42 is inspected based on the transmitted X rays. The soldering inspecting apparatus has the constitution having the parts performing the following functions, respectively. An X-ray generating means 1 generates the X-ray beam 11. A positioning control means 2 controls the relative positions of the X-ray generating means 1 and the mounted part 6 so that the X-ray beam 11 is transmitted through a path in a gap between a plurality of the lead pins 41 with respect to the soldered part 42 of the mounted part 6. An X-ray detecting means 3 detects the intensity of the X-ray beam 11 which is transmitted through the soldered part of the mounted part 6. The suitability of the soldered part 42 is inspected based on the detected intensity of the rays.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a soldering inspection device for inspecting unsoldered surfaces on surface-mounted components, and particularly for inspecting the soldered portions of mounted components made by soldering multiple lead pins of a semiconductor element onto a board. The present invention relates to a soldering inspection device. In recent years, with the miniaturization of electronic devices, there is a tendency for surface-mounted components on printed circuit boards used in these electronic devices to be mounted in higher density and in greater numbers. These surface mount components are much smaller than conventional insert components, and while the mounting area can be reduced, the soldering operation performed during mounting also needs to be performed with high precision.

[0002] High-density mounting surface mount components must be inspected with high accuracy even when inspecting the unsoldered state after being mounted on a printed circuit board, and conventional visual inspection is becoming difficult. In particular, QFP (Quad Flat
In package ) type mounted components, the lead width is approximately 0.3 mm, making it difficult to visually inspect minute floating defects on lead pins and unattached solder. There is a need for a soldering inspection device that can automatically inspect the soldered portions of various high-density mounted components.

0003

2. Description of the Related Art Conventionally, there has been a soldering inspection apparatus of this type as shown in FIG. FIG. 6 shows a schematic configuration diagram of a conventional soldering inspection device. In the figure, the conventional soldering inspection apparatus includes an X-ray generator 1 that generates an X-ray beam and projects the X-ray beam approximately perpendicularly onto a mounted component 6 having a semiconductor element 4 mounted on a printed circuit board 5. and an image intensifier 3 that detects the light intensity of the X-ray beam that has passed through the mounted component 6.

Next, the inspection operation of the conventional apparatus based on the above configuration will be explained with reference to FIGS. 7 and 8. 7 shows a perspective view, side view, and front view of normal soldering, and FIG. 8 shows a perspective view, side view, and front view of defective soldering. Said Figure 7
As shown in the figure, in case of normal soldering, the lead pin 41
Due to the surface tension between the lead pin 41 and the footprint 51 of the printed circuit board 5, the solder portion 42 is sucked up and becomes a concave solder shape (on the printed circuit board 5).
Although the total amount of solder in the solder portion 42 in the lower part is reduced, there is a large amount of solder in the edge portions such as the heel portion and the tip portion of the lead pin 41.

Furthermore, as shown in FIG. 8, in the case of defective soldering, the solder does not come into contact with the lead pins 41 and the solder portions 42 form a convex solder shape on the printed circuit board 5 due to surface tension, causing the lead pins 41 The amount of solder at the heel and tip will be smaller. In order to inspect and sort out the normal and defective soldering conditions, X-rays are irradiated from above the printed circuit board 5 to the solder portion 42 to be inspected, and a fluoroscopic image is analyzed using the irradiated X-rays. The amount of solder in 42 is roughly estimated. Soldering defects are inspected by selecting defective soldering conditions based on this estimated solder amount data.

[0006] In addition, there are other soldering inspection devices that use reflection angle characteristics using an optical method, and detecting the presence or absence of a solder portion is a defect in which the lead pin is lifted from the solder portion and is not bonded. cannot be detected. Also,
In a soldering inspection device that inspects based on height data, it is difficult to correctly detect a floating state of a minute lead pin. This is because defects are determined by checking the presence or absence of solder at the tip of the lead, and the soldering condition such as curvature.

That is, what is more problematic in actual joining is the solder amount distribution at the heel portion of the lead pin 41 (the curved portion of the lead pin), which is not visible from the outside, than the state of solder adhesion at the tip of the lead pin 41. Therefore, among various soldering inspection apparatuses, an inspection apparatus that performs judgment based on a perspective image using X-rays is used. In this way, the heel part of the lead pin 41 is the part where the difference in solder amount occurs the most depending on whether it is normal or defective (defective), and it is an effective clue for defect determination. Inspecting the adhesion state is most important in increasing the reliability of the inspection results.

[0008]

[Problems to be Solved by the Invention] Since the conventional soldering inspection equipment was constructed as described above, in an inspection equipment that uses optical reflection angle characteristics, it is difficult to detect soldering from the outside, such as at the heel of a lead pin. The problem is that it is difficult to inspect the amount of solder in areas that cannot be seen.
In addition, with inspection equipment that analyzes transmitted images using X-rays, the X-rays that pass through the heel of the lead pin will pass through the lead pin for a long time, reducing the amount of X-rays that pass through the solder part, making it impossible to accurately detect the amount of solder. There was a problem in that it was not possible to judge the suitability of soldered parts with high precision. That is, X
Since the heel of the lead pin is inspected by irradiating the X-ray from the surface, the X-ray that passes through the heel of the lead pin has a long transmission distance through the part where the lead pin is bent and stands perpendicular to the printed circuit board. (See X-ray 11a in Figure 9) The amount of X-rays that are largely absorbed within the lead pin and reach the solder portion at the heel of the lead pin is small, and the amount of X-rays that actually pass through the solder portion is also small. This is due to a reduction in the dynamic range of X-ray detection data.

Furthermore, in order to improve the dynamic range in conventional soldering inspection equipment, it is necessary to irradiate a large amount of X-rays with short wavelengths that are difficult to absorb into the lead pin portion, and then correct and remove the amount of X-rays absorbed by the lead. When irradiating a large amount of X-rays with short wavelengths, there is a risk that the internal data of the IC may be damaged (soft error). In addition, the amount of X-rays absorbed by the lead depends on the shape and curvature of the lead, and the direction of X-ray incidence.
(see the difference between lines 11a and 11b) changes significantly, so it is difficult to know in advance the influence of the amount of absorption by the lead and to correct it.

[0010] Therefore, with the conventional method, it is difficult to accurately measure the amount of solder at the heel of the lead. The present invention proposes a soldering inspection device that can accurately inspect solder parts for suitability by excluding X-ray absorption by lead pin parts, improving the dynamic range, and determining the amount of solder with high accuracy. With the goal.

[0011]

[Means for Solving the Problems] FIG. 1 shows a diagram illustrating the principle of the present invention. In the same figure, the soldering inspection apparatus according to the present invention applies an X-ray beam (11 ) and inspects the soldered portion (42) based on the transmitted X-ray light, the soldering inspection device includes an X-ray generating means (1) for generating the X-ray beam (11); Connect the wire beam (11) to a plurality of lead pins (41) to the soldered part (42) of the mounted component (6).
positioning control means (2) for controlling the relative positions of the X-ray generating means (1) and the mounted component (6) so that the path passes through the gap in the mounting component (6); 42), and an X-ray detection means (3) for detecting the light intensity of the X-ray beam (11) transmitted through the X-ray beam (11), and the suitability of the soldered portion (42) is inspected based on the detected light intensity. .

0012

[Operation] According to the present invention, by controlling the relative position of the X-ray generating means and the mounted component so that the X-ray beam does not pass through the lead pin part, absorption of X-rays by the lead pin part is suppressed as much as possible and dynamic This improves the range and detects the suitability of solder parts with high precision and accuracy.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 2 to 5. FIG. 2 is a schematic diagram of the overall configuration of this embodiment, FIG. 3 is a perspective view of essential parts in the X-ray projection direction, FIG. 4 is a front view of the substrate in a tilted state, and FIG. 5 is a side view of the substrate in a tilted state. In each of the above figures, the soldering inspection apparatus according to the present embodiment includes an X-ray generator 1 that generates X-rays, and a mounted component 6 in which a semiconductor element 4 is soldered and mounted on a printed circuit board 5.
a stage controller 2 that controls the projection angle of the X-ray beam 11 emitted from the X-ray generator 1 by tilting the image intensifier 3
The X-ray intensity signal output from the image intensifier 3 is input, and the control signal and tilt angle signal of the stage controller 2 are also input/output, and the solder portion of the mounted component 6 is adjusted based on these signals. This configuration includes an arithmetic control section 7 that determines suitability in 42 and controls it.

As shown in FIG. 3, the X-ray generating device 1 has a y-axis in the direction perpendicular to the semiconductor device 4, a z-axis in the direction in which the plurality of lead pins 41 of the semiconductor element 4 are arranged, and a y-axis and a z-axis, respectively. In an x-y-z three-dimensional coordinate system with the orthogonal direction as the x-axis, the angle θx with respect to the x-axis and the angle θ with respect to the y-axis
The beam is configured to irradiate the solder portion 42 directly at each angle θz with respect to the y and z axes without passing through the lead pins 41 of the semiconductor element 11.

The arithmetic control section 7 includes a CPU 71 which controls the entire device and calculates whether or not the soldered portion is appropriate.
, an I/O unit 72 that inputs and outputs control signals and tilt angle signals to and from the stage controller 2, and an A/D converter 73 that converts the X-ray intensity signal from the image intensifier 3 into a digital signal. and an image input section 74 that inputs this digital X-ray intensity signal as an image signal.
The configuration includes a memory 75 that stores this image signal, and a bus 75 that connects each component.

Next, the operation of the apparatus of this embodiment based on the above configuration will be explained. First, for the x, y, and z coordinate axes of the X-Y-Z three-dimensional coordinate system shown in FIG.
The mounted component 6 is irradiated with an X-ray beam 11 having an angle of θz from the X-ray generator 1. The irradiation angle of this X-ray beam 11 is determined by the distance d1 between the ends of the lead pins 41 in FIG.
, the height of the lead pin 41 is h1, and the inclination angle of the X-ray beam 11 with respect to the y-axis is θ1, then the maximum inclination angle θ1
max is as follows.

[0017] θ1max=tan-1(d1/h1) (1) Also, in FIG. 5, the semiconductor element 4 as an IC package
The distance between the end and the heel portion of the lead pin 41 is d2, the height from the printed circuit board 5 to the top surface of the semiconductor element 4 is h2, the inclination angle of the lead pin 41 with respect to the y-axis is θ3, and the X-ray beam with respect to the y-axis is If the inclination angle of No. 11 is θ2, the maximum inclination angle θ2max is as follows.

[0018] θ2max=tan-1(D2/h2)...(2) The inclination angle θ specified by the above formulas (1) and (2) can be set to the optimum angle at which the X-ray absorption of the lead pin 41 is minimized. can. The X-ray beam 11 irradiated onto the mounted component 6 at this optimum angle θ is detected by the image intensifier 3 arranged parallel to the printed circuit board 5 so that the magnification does not differ depending on each part on the printed circuit board 5. A perspective image will be formed on the surface. The X-ray intensity signal forming this fluoroscopic image is converted into a digital value by the A/D converter 73 and stored in the memory 75 via the image input section 74 as a digital X-ray intensity signal forming a grayscale image.

The CPU 71 reads out the digital X-ray intensity signal stored in the memory 75, and determines the lead pin based on the moving direction, moving distance, and magnification rate of the stage 8 inputted from the stage controller 2 via the I/O section 72. 4
A grayscale image of the heel portion of the lead pin 41 is formed, and this grayscale image is logarithmically converted to measure the thickness of the solder portion 42 of the heel portion of the lead pin 41. Based on the measured thickness of the solder portion 42 in the heel portion, the state of solder adhesion to the lead pin 41 can be determined and a soldering defect can be detected.

[0020] Note that the mounted component is a 160-pin QFP.
type, the thickness of the solder portion 42 at the heel portion of the lead pin 11 is approximately 10 mm in unsoldered state.
It is around 0μm, and the maximum is about 600μm in normal soldering condition.
m, it can be determined that 150 μm to 200 μm or more is a normal soldering state. Here, the inclination angle θ1 is 0 to 20 degrees, and the inclination angle θ2
can also be set to 0 to 35 degrees.

Furthermore, in the above embodiment, the X-ray beam is tilted in two axial directions (x-axis, y-axis), but it may be tilted only in one of the axial directions.

[0022]

As explained above, according to the present invention, by controlling the relative position of the X-ray generating means and the mounted component so that the X-ray beam does not pass through the lead pin portion, The dynamic range is improved by suppressing absorption as much as possible, and the suitability of the solder portion can be detected with high precision and accuracy.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram for explaining the principle configuration of the present invention.

FIG. 2 is an overall schematic configuration diagram for explaining one embodiment of the present invention.

3 is a perspective view of a main part in the X-ray projection direction for explaining the X-ray beam irradiation angle of the embodiment shown in FIG. 2; FIG.

4 is a front view of the substrate for explaining the tilted state of the substrate in the embodiment shown in FIG. 2; FIG.

5 is a side view of the substrate for explaining the tilted state of the substrate in the embodiment shown in FIG. 2; FIG.

FIG. 6 is a schematic configuration diagram of a conventional soldering inspection device.

FIG. 7 is a perspective view, a side view, and a front view of normal soldering.

FIG. 8 is a perspective view, a side view, and a front view of defective soldering.

FIG. 9 is an enlarged view of a soldering part for explaining a problem with a conventional soldering inspection device.

[Explanation of symbols]

1... X-ray generator (X-ray generating means) 2... Stage controller (positioning control means) 3... Image intensifier (X-ray detecting means) 4... Semiconductor element 5... Printed circuit board 6... Mounted components 7... Arithmetic control section 11...X-ray beam 41...Lead pin 42...Soldering part (soldering part) 71...CPU 72...I/O section 73...A/D conversion section 74...Image input section 75...Memory

Claims (6)

[Claims] Claim 1: A mounted component (6) formed by soldering and mounting a semiconductor element (4) having a plurality of lead pins (41) on a substrate (5) is irradiated with an X-ray beam (11).
In the soldering inspection device that inspects the soldered portion (42) based on transmitted light, the X-ray beam (11)
an X-ray generating means (1) that generates an X-ray beam (1);
The X-ray generating means (1) and the mounted component (6) are arranged relative to each other so that the A positioning control means (2) for controlling the position, and an X-ray detection means (3) for detecting the light intensity of the X-ray beam (11) transmitted through the soldered portion (42) of the mounted component (6). , the soldering part (4) based on the detected light intensity.
A soldering inspection device characterized by inspecting the suitability of 2). 2. The soldering inspection apparatus according to claim 1, wherein the positioning control means (2) is configured to control a semiconductor element (
4) in the direction in which the plurality of lead pins (41) are lined up
The irradiation angle of the ray beam (11) is tilted, and the X-ray generating means (1) and the mounted component (
6) A soldering inspection device characterized by controlling the relative position of item 6). 3. The soldering inspection apparatus according to claim 1, wherein the positioning control means (2) is configured to control a semiconductor element (
The irradiation angle of the X-ray beam (11) is tilted in a direction perpendicular to the direction in which the plurality of lead pins (41) are lined up in step 4), and the X-ray beam is Generation means (1) and mounted parts (6)
A soldering inspection device characterized by controlling the relative position of. 4. The soldering inspection apparatus according to claim 1, wherein the positioning control means (2) is configured to control a semiconductor element (
4), the X-ray beam (11
) and controlling the relative positions of the X-ray generating means (1) and the mounted component (6) so that the X-ray beam (11) passes through the gap between the plurality of lead pins (41). A soldering inspection device characterized by: 5. In the soldering inspection apparatus according to claim 2, the irradiation angle of the X-ray beam (11) is set such that the gap between the ends of the lead pin (41) is d1, and the distance between the ends of the lead pin (41) is d1.
The height of h1 is the normal direction of the mounting plane of the board (5) (y
The inclination angle of the X-ray beam (11) with respect to the axis) is θ1
Then, the maximum inclination angle θ1max is tan-1(d
1/h1). 6. In the soldering inspection apparatus according to claim 3, the irradiation angle of the X-ray beam (11) is determined by the distance between the end of the semiconductor element (4) and the heel portion of the lead pin (4). d2, from the substrate (5) to the semiconductor element (4
) The height to the top surface is h2, and the inclination angle of the lead pin 11 with respect to the normal direction (y-axis) of the mounting plane of the board (5) is θ.
3. X-ray beam (11
) is the inclination angle θ2, the maximum inclination angle θ2ma
A soldering inspection device characterized in that x is tan-1 (d2/h2).