JP3277691B2 - Inspection method of mounted printed circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of inspecting a mounted printed circuit board by irradiating a finely narrowed light beam onto the mounted printed circuit board and receiving the reflected light to inspect the solder shape. is there.

[0002]

2. Description of the Related Art In recent years, inspection of components on a mounted printed circuit board for positional displacement, missing parts, defective soldering, and the like has been performed by irradiating a narrowly focused beam light to the mounted printed circuit board and detecting reflected light thereof. Some are done by contact. Conventionally, as such an inspection method, there is a method using the principle of triangulation, in which a minute light beam generated from a light source is deflected by a polygon mirror to scan the substrate, and the light beam is irradiated from the irradiation position of the minute light beam on the substrate. There is an inspection method in which reflected light is received by a photoelectric conversion element, and an inspection is performed by obtaining the height of an irradiation position of a minute beam light corresponding to the light receiving position.

[0003]

However, in the above-mentioned conventional inspection method, there is glossiness particularly on the solder surface,
Moreover, since the light is often inclined, the reflected light from the irradiation position of the minute beam light may not enter the photoelectric conversion element. For this reason, there is a problem that the detection by the photoelectric conversion element becomes impossible, an accurate height is not required, and the solder inspection cannot be performed.

Accordingly, the present invention provides a method for detecting the shape of a solder by detecting reflected light along an irradiation axis of a minute beam of light on a substrate by a photoelectric conversion element and detecting an inclination state of an inspection surface from the amount of the received light. Can be inspected.

[0005]

In order to solve the above-mentioned problems, a method for inspecting a mounted printed circuit board according to the present invention scans the mounted printed circuit board with a minute light beam, and scans the light from the irradiation position of the minute light beam. A method in which reflected light along the irradiation optical axis of a minute beam light is received by a photoelectric conversion element to obtain a solder shape. (A) A measurement area to be inspected is formed by connecting a mounted component
The horizontal direction where the field extends and the vertical direction which is the width direction of the mounted component
Countercurrent Prefecture, previously divided into a plurality of small regions of the horizontal and vertical, from the quantity of received reflected light in (b) the photoelectric conversion element
The brightness of each of the small areas is binarized, and a two-dimensional
Creating a turn, and (c) forming a pattern of the intensity of each row in the vertical direction.
In the horizontal direction from the mounted component side
First, start of solder, which is the connection part between the mounted component and solder
Recognize the edges and then the continuity of the solder
The end of the solder is recognized, and the start end and the end
The length is detected .

[0006]

According to the above method, the luminance is detected for each of the divided areas from the amount of the reflected light received by the photoelectric conversion element.
The brightness is binarized to create a two-dimensional pattern of the brightness. By detecting the inclined state of the substrate surface from the two-dimensional pattern of the luminance, the quality of the solder application and the defect are inspected.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an apparatus for inspecting a mounted printed circuit board to which the present invention is applied. In FIG. 1, reference numeral 1 denotes a light source for generating a minute light beam to irradiate the mounted printed circuit board 6. Reference numeral 2 denotes a collimating lens system for condensing the minute beam light from the light source 1 to make it a parallel light beam. Reference numeral 3 denotes a polygon mirror for deflecting the parallel light beam and deflecting light reflected from the mounted printed circuit board 6. Reference numeral 4 denotes a polygon motor for driving the polygon mirror 3 to rotate. Reference numeral 5 denotes a light projecting fθ lens that condenses the parallel light beam deflected by the polygon mirror 3 and irradiates the mounted printed circuit board 6 substantially perpendicularly. Reference numeral 6 denotes a mounted printed board to be inspected.

Reference numeral 7 denotes a mounted light that has returned along the light projection optical axis through the light projection fθ lens 5 and the polygon mirror 3 among the reflected light from the small beam light irradiation position on the mounted printed circuit board 6. The tunnel mirror deflects reflected light in a direction perpendicular to the printed circuit board 6. Reference numeral 8 denotes a lens for collecting the reflected light deflected by the tunnel mirror 7. Reference numeral 9 denotes a stop for blocking reflected light from directions other than the vertical direction. Reference numeral 10 denotes a photodiode that receives the reflected light in the vertical direction and converts the amount of received light into an electrical output.

Reference numeral 11 denotes a table for fixing the mounted printed circuit board 6. A ball screw 12 moves the table 11 in the sub-scanning direction (the direction of the arrow y) by rotating. Reference numeral 13 denotes a ball screw motor that rotates the ball screw 12. Reference numeral 14 denotes a guide rail for guiding the table 11. The operation of the mounted printed circuit board inspection apparatus configured as described above will be described.

The minute light beam generated from the light source 1 is converted into a parallel light beam by the collimating lens system 2, passes through the hole of the tunnel mirror 7, is deflected by the polygon mirror 3, and is condensed by the light projection fθ lens 5, The light beam is irradiated substantially vertically onto the mounted printed circuit board 6 as an optical axis of the minute beam light irradiation. At this time, the minute beam light generated from the light source 1 is
With the rotation of the polygon mirror 3 rotated by the polygon motor 4, the mounted printed circuit board 6 is scanned in the main scanning direction (the direction of the arrow x) in the figure.

The reflected light reflected from the minute beam light irradiation position in the direction of the minute beam light irradiation optical axis (substantially vertical direction) passes through the light projecting fθ lens 5, polygon mirror 3, tunnel mirror 7, lens 8, and stop 9. Photodiode 1 through
It is led to 0. At this time, the reflected light in the vertical direction is
The light is collected by the θ lens 5 and the lens 8, and the collected reflected light is received by the photodiode 10. Further, light other than the reflected light in the direction of the optical axis of the minute beam light irradiation is blocked by a stop 9 provided between the lens 8 and the photodiode 10. Therefore, only the amount of reflected light reflected from the minute beam light irradiation position in the direction of the minute beam light irradiation optical axis can be correctly measured. Hereinafter, the amount of light received by the photodiode 10 (reflected light in the direction of the optical axis of the irradiation of the minute beam light) is referred to as the incident luminance.

Since the photodiode 10 receives the reflected light in the vertical direction from the mounted printed board 6, when the inclination of the solder surface is gentle or no solder is attached,
The output increases as the reflected light in the vertical direction increases,
Conversely, when the inclination of the solder surface is steep, the reflected light in the vertical direction is reduced, and the output is reduced. Using this feature,
As an embodiment of the present invention, a method of inspecting a solder defect by a pattern of reflected light intensity applied to the above-described mounted printed circuit board inspection apparatus will be described below.

First, a measurement area is set before the inspection. FIG. 2 shows a setting example of a measurement area for performing a solder inspection. FIG. 2A is a plan view of a solder connection portion of a mounted component to be inspected.
Reference numeral 2 denotes solder, and 23 denotes a land on the substrate. Measurement area 2
The method of setting 4 includes a method in which the size in the vertical direction is based on the lead width as shown in FIG. 5B and a method in which the land size is based on the land width as shown in FIG. Is a land length as shown in FIGS. In the present embodiment, the measurement area 24 is set as shown in FIG.

Next, the measurement area 24 set in FIG.
Is divided into a plurality of vertical and horizontal divided areas 25 as shown in FIG.
Divided into The size of each of the divided areas 25 is larger than the spot irradiated by the minute light beam from the light source 1, and is set to an appropriate size such that data of a plurality of reflected light amounts can be sampled by the photodiode 10. In the horizontal division, the width of the central divided area divided into three parts instead of equal divisions can be increased.

As described above, the inspection is started after the measurement area is set to a plurality of divided areas prior to the inspection.
The rotation of the polygon mirror 3 scans the measurement area 24 with a minute light beam, and samples a plurality of pieces of incident luminance data in each divided area 25. From the sampled data, the characteristic value of the incident luminance in each divided area 25 is obtained. Examples of the method of obtaining the characteristic value include a method in which an average of the incident luminance in each divided area is set as the characteristic value, and a method in which the maximum value of the incident luminance in each divided area is set as the characteristic value.

Next, the characteristic value is binarized based on a certain set value. As described above, the epi-illuminance is dark (small) on a slope and bright (large) on a plane. Therefore, if the characteristic value of each divided area is larger than this set value, it is determined that the area is a plane. When the characteristic value of the incident light luminance is binarized in this manner, for example, a result shown in FIG. 3 is obtained. Here, a hatched portion 26 indicates an inclined surface, and a blank portion 27 indicates a flat portion.
The pattern of the intensity of the brightness in the divided area makes it possible to recognize the solder shape.

In this embodiment, the inspection of the quality of the solder is performed by
The detection is performed by detecting the solder length and the solder non-wetting shape (that is, the defective connection between the lead and the solder) from the pattern of the intensity of the incident light.

First, the detection of the solder length will be described. The solder length is measured by recognizing the connection between the lead and the solder, that is, the starting end of the solder from the incident luminance pattern, then recognizing the continuity of the solder, and finally recognizing the end of the solder. I do.

The incident luminance patterns of the three divided areas in each column in the vertical direction are as shown in FIG.
(B) two slopes, (c) two slopes, the center of which is flat,
It is classified into five shapes: (d) one slope, and (e) a flat surface. A pattern in which both ends are inclined and the center is flat in (c) is called a non-wetting pattern, and the central part is also regarded as a slope. Here, as shown by the position of arrow A in FIG. 5, when viewed from the left end side of the
If there is more than one slope, it is regarded as the starting end of the solder. That is, it is determined that the solder is formed rightward from the position.

Here, the range in which the start end is recognized can be set with a certain margin to absorb the recognition error of the lead tip position. When no margin is given to the recognition range L as shown in FIG. 6A, it is determined whether or not the start end exists in the first column on the left end of the measurement area. On the other hand, as shown in FIG. 6B, if the recognition range L has a margin and the start end A is recognized from the range of three columns from the left end of the measurement area, the slope exists in the second column. Is also recognized as the starting end. Further, when there is no slope in the recognition range L as in (c), the solder length is set to zero.

When the start end of the solder is detected, as shown in FIG. 7, it is recognized whether or not the divided area in the right column of the divided area which is the slope is a slope. Shall be In the figure, it is recognized that the solder is continuous between the arrows L. As an exception, only the central part of the non-wetting pattern of (d) is considered to be continuous if it is on the right slope.

The end of the solder is regarded as the end of the solder when the divided area of the slope continuing to the right column becomes one or less. For example, the end of the solder is indicated by the arrow B in FIG. It has recognized. In particular, (d) is a method of recognizing the end in the case of a non-wetting pattern as an exception. As described above, from the start end to the end end, the solder length is detected.

Next, regarding the recognition of the non-wetting (defective) of the solder, the non-wetting shape is such that the tip of the lead 21 is adapted to the solder as shown in the sectional views of FIGS. As shown in the cross-sectional view of FIG.
1 means that the tip is floating. Solder non-wetting shape
As shown in FIGS. 7A and 7B and FIGS. 7B and 7B, there is a characteristic that the incident light luminance at the apex of the solder portion is high (bright). Utilizing this characteristic, the length of the vertex (non-wetting length) is measured from the two-dimensional pattern of the intensity of the brightness shown in FIG. If it is short, it is judged good. Next, a method for obtaining the non-wetting length will be described step by step.

First, it is recognized whether or not it has a non-wetting shape. That is, as shown in FIG. 3 (c), even if the brightness of the central portion of the solder is high, if the solder shape is fan-shaped, it is not a non-wetting shape. Even if the non-wetting pattern shown in FIG. 4 (c) exists, if the central divided area of the right column of the non-wetting pattern is not a slope, it is not recognized as a non-wetting shape.

In the case of a non-wetting shape, whether it is the shape shown in FIG. 9A or the shape shown in FIG. 9B depends on the positional relationship between the measured starting position of the non-wetting pattern and the starting end of the solder. Determine. In other words, if the start position of the non-wetting pattern matches the position of the start end of the solder, the shape shown in FIG.
Otherwise, it is determined that the shape is (a).

After confirming the non-wetting shape, the length of the non-wetting shape is determined. The length of the non-wetting pattern is obtained from the continuous number of the non-wetting patterns. If there are a plurality of non-wetting patterns, the non-wetting patterns are classified by shape and the maximum non-wetting length for each shape is adopted. For example, in the example shown in FIG. 10, the solder length L is 9 dots, the non-wetting length is 2 dots in FIG.
(B) The maximum length of the shape can be measured as 3 dots.

The solder length and the non-wetting length measured as described above are each compared with a set value to detect a solder defect. With this set value, it is possible to change the length of solder to be defective, the length of non-wetting, and the shape of non-wetting.

As described above, the method for inspecting a mounted printed circuit board according to the present invention binarizes the incident light luminance and creates a two-dimensional pattern having a high and low incident light luminance, thereby obtaining a glossy and highly inclined solder or the like. Even in this case, the shape can be recognized from the amount of light received by the photoelectric conversion element. Especially in the present invention
First, in the two-dimensional pattern,
The pattern of each column in the vertical direction, which is the width direction of the
Recognition, then the length direction of the land where the solder extends
In the direction, how is the pattern of each adjacent column in the vertical direction
The solder shape can be detected by recognizing whether
I have to put out. Various solders expected for this
Is coded in advance, and the solder shape is compared with this.
Detects the shape and matches the master solder shape
Compared to the one that detects the solder shape after soldering
Observe various solder shapes and code or master images
No need to prepare images
How the patterns in each column are arranged in the horizontal direction
Only need to be recognized each time.
Also, the solder shape can be detected efficiently.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an inspection apparatus to which an inspection method of a mounted printed circuit board according to the present invention is applied.

FIG. 2 is a plan view showing a setting example of a measurement area.

FIG. 3 is a plan view showing a divided area obtained by dividing a measurement area.

FIG. 4 is a classification diagram of an incident luminance pattern

FIG. 5 is an incident luminance pattern diagram illustrating a measurement start end of solder.

FIG. 6 is an incident luminance pattern diagram illustrating a measurement start end of solder.

FIG. 7 is an incident luminance pattern diagram for explaining continuity of solder;

FIG. 8 is an incident luminance pattern diagram illustrating a measurement termination portion of solder.

FIG. 9 is a cross-sectional view for explaining a non-wetting shape, a plan view of incident luminance, and a pattern of incident luminance.

FIG. 10 is an incident-light luminance pattern diagram for explaining a non-wetting shape.

[Explanation of symbols]

 Reference Signs List 1 light source 2 collimating lens system 3 polygon mirror 5 light emitting fθ lens 6 mounted printed circuit board 7 tunnel mirror 8 lens 9 aperture 10 photodiode 11 table 21 lead 22 solder 23 land 24 measurement area 25 division area

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Daisuke Nagai 8-1, Koshinmachi, Takamatsu City, Kagawa Prefecture Inside Matsushita Hisashi Electronics Co., Ltd. (56) References JP-A-2-212748 (JP, A) JP-A-3 −218405 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01N 21/84-21/958 H05K 3/32-3/34 512 H05K 13/08

Claims (6)

(57) [Claims] A printed circuit board on which mounting is performed is scanned by a minute beam light, and reflected light along an irradiation optical axis of the minute beam light is received by a photoelectric conversion element from an irradiation position of the minute beam light to form a solder shape. (A) measuring a measurement area to be inspected by connecting a mounted component
The horizontal direction where the field extends and the vertical direction which is the width direction of the mounted component
Countercurrent Prefecture, previously divided into a plurality of small regions of the horizontal and vertical, from the quantity of received reflected light in (b) the photoelectric conversion element
The brightness of each of the small areas is binarized, and a two-dimensional
Creating a turn, and (c) forming a pattern of the intensity of each row in the vertical direction.
In the horizontal direction from the mounted component side
First, start of solder, which is the connection part between the mounted component and solder
Recognize the edges and then the continuity of the solder
The end of the solder is recognized, and the start end and the end
A method for inspecting a mounted printed circuit board, wherein the length is detected . 2. One of the small areas binarized by the intensity of the brightness
The other side is a plane and the other side is a slope.
The pattern in each row in the horizontal direction from the mounted component side
When recognizing an application, each column in the vertical direction
Recognize the start of solder when the upper slope exists
2. The pre-mounted package according to claim 1, wherein:
Inspection method for printed circuit boards. 3. The horizontal direction in which the solder extends after recognizing the start end.
In, the small area next to the small area that is the slope is the slope
In this case, it is recognized that the solder is continuous
A method for inspecting a mounted printed circuit board according to claim 2. 4. Adjacent to each other in a lateral direction in which the solder extends.
For each column in the vertical direction,
Counting and recognizing it as the end of solder when it falls below the specified number
The mounted device according to claim 2 or 3, wherein
Inspection method for printed circuit boards. 5. A recognition of a start end in a solder measurement area.
Is set in advance, and soldering starts within this range.
The feature is to detect whether the edge exists
The method for inspecting a mounted printed circuit board according to claim 2. 6. The pattern of each column in the vertical direction is set in advance by a half
Bad connection putter And the steps in (c)
When this defective pattern continues in the horizontal direction,
The feature is that the quality of the solder is detected when
The method for inspecting a mounted printed circuit board according to claim 1.
Law.