JPH02243911A - Soldering inspection device - Google Patents

Abstract

PURPOSE:To improve the reliability of inspection by deciding whether a solder zone is normal or not based on a video signal obtained from a removing means which removes a bright part detected in a video signal. CONSTITUTION:The light from a light source 1 is made incident on a solder zone filler 22 by a light guide 2 through a polarizing plate 3a. When the polarizing plate 3a is provided facing the fillet 22 so as to provide P or S polarization and a polarizing plate 5 is provided so as to allow its polarizing surface to be intersected orthogonally with the polarizing plate 3, a TV camera 7 detects only secondary reflected light from another component. Further, a TV camera 8 is provided with no polarizing plate, so direct reflected light and the secondary reflected light from the fillet 2 are both detected. For the purpose, the bright part detected in the camera 7 is masked according to the output of the camera 8 to detect only the direct reflected light. Namely, a binarization coding circuit 9 detects the bright part and masks the output of the camera 8, which outputs only the direct reflected light from the fillet 22, thus removing the secondary reflected light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for inspecting parts of solder on a printed circuit board or the like.

[Conventional technology]

When electronic components are mounted on a printed circuit board or the like, they are mounted by soldering, but since the soldering condition greatly affects the reliability of the electronic circuit, it is necessary to inspect the soldered parts. Conventional soldering inspection is described, for example, in Monthly Semiconductor World, Vol. 6, No. 12, pp. 230-237.

[Problem to be solved by the invention]

Since many electronic components are mounted at a high density on an actual printed circuit board, there are mirror surfaces with high reflectivity such as other soldering parts or metal parts in the immediate vicinity of the soldering part of interest. In the conventional technology, since the direction of the light source and the direction of the TV right camera are constant, if there is reflected light from the fillet part, it is assumed that the fillet part has an inclination within a certain non-defective range, and the pass/fail judgment is made. are doing. On the other hand, if there is a mirror surface nearby, the reflected light from that mirror surface will be reflected back to the solder fillet, and multiple reflected light bright spots were detected in the TV camera detection image, which is originally a defect. Therefore, there was a problem in that reflected light was detected from fillets where no reflected light should be obtained, making it impossible to accurately determine defects.

The purpose of the present invention is to remove the reflected light from other components other than the direct reflected light from the light source at the fillet portion (hereinafter referred to as secondary reflected light), and to correctly remove the reflected light from other parts (hereinafter referred to as secondary reflected light), even in densely decorated printed circuit boards. An object of the present invention is to provide a soldering inspection device capable of determining defects.

[Means to solve the problem]

In order to achieve the above object, the configuration shown in FIG. 4 is adopted.

In Figure 4, 1 is a light source, 2 is a light guide, 3 is a polarizing plate, 4
is a half mirror, 5 is a polarizing plate, 6 is a mirror, 7.8 is T
V camera, 9 is a binarization circuit, and 10 is a masking circuit. The polarizing plate 3 polarizes the light from the light source in a direction parallel to or perpendicular to the printed circuit board 20 having the soldered portion to be inspected. The polarizing plate 5 has a polarizing plane perpendicular to the polarizing plane of the polarizing plate 3. Soldering part fillet 22
When the slope of the average slope is θ and the direction of determination is n,
The original axes of the TV camera 7 and the light guide 2 are arranged so as to form an angle of 2θ. The light emitted from the light guide passes through the polarizing plate 3, is reflected by the fillet 22, and is detected by the TV camera 7 through the bar 7mi 2-4 and the polarizing plate 5. - 10,000, 10,000 of the light separated by the half mirror 2-4 passes through the mirror 6,
Detected by the TV left camera.

Light with only P-polarized light or S-polarized light is transmitted to a metal surface (
When the light enters the soldering part), there is no rotation of the plane of polarization, and the component in the direction of the plane of polarization perpendicular to the polarization plane becomes zero. However, when polarized light that is neither P-polarized nor S-polarized is incident, the polarization plane The secondary reflection portion is removed from the fillet reflected light by taking advantage of the fact that the fillet is rotated to become elongated circularly polarized light with components in various polarization directions.

[Effect]

The intensity of reflected light of polarized light on a metal surface will be explained with reference to FIG. As shown in the fifth factor, the angle between the polarization direction of the incident light from the light guide 2 and the plane of incidence is ψ1, the angle between the polarization transmission axis direction of the polarizing plate 5 on the reflected light side and the plane of incidence is ψ2,
The amplitude reflectance of P polarized light is rp, the amplitude reflectance of S polarized light r8,
If the energy reflectance of P-polarized light is RPl, the intensity of the light that has passed through the polarizing plate is Io%, and the phase difference between the P-polarized light component and the reflected light from the 8 polarizing plates is lφ, then the intensity of the reflected light that has passed through the polarizing plate is It is given by the following formula.

X(ψ1.ψ2)=IσRp(p”dn”$, *5
tn2ψ2-1-aI! +2ψ,・■2ψ2+ T p
dt 2ψ, 5g1n2ψ2・plane Δφ) −・・・−
・(1) ψ, = 90°, that is, when applying P polarization to the light source, I (906, ψ, ): IO@Rp p2dn
2ψ2・(2). Therefore, the polarizing plate on the reflective side is ψ2
When = 0, the reflection intensity is φ, and when ψ2 = 900, the reflection intensity is jl large. 0I (90°, 90') = IosR
It becomes p-p.

In other words, if the source of direct reflection (primary reflection) from the light source is P-polarized with respect to the fillet, if the detection side polarizing plate is set to ψ2 = 0, no reflected light will be detected, and ψ2 = 90°. It will be detected brightest if you set it to .

On the other hand, when the light from the light source is first reflected by another component and then reflected by the fillet 22, the polarization direction of the light source is set to P polarization with respect to the fillet 22, so it is not reflected to the reflective surface of the other component. , it does not become p-polarized light. Therefore, in equation (1), the reflected light has a rotated polarization direction and a polarization component other than the main polarization direction. Furthermore, since this reflected light enters the fillet, it does not become P-polarized light for the fillet, and even if the fillet reflected light passes through the polarizing plate 5 in the direction where ψ2=φ, the transmitted light intensity is φ. Not. Therefore, only secondary reflected light from other parts is detected.

From the above, if the fourth factor polarizing plate 3 is installed so that the light is p- or s-polarized with respect to the fillet 22, and the polarizing plane of the polarizing plate 5 is installed perpendicular to the polarizing plate 3, the Tv camera 7
Only secondary reflected light from other parts is detected. -10,000T
Since the v-camera 8 is not equipped with a polarizing plate, both the direct reflected light and the secondary reflected light from the fillet are detected. Therefore,
By masking the bright portion detected by the TV camera 7 from the output of the '1'v camera 8, only the directly reflected light is detected. For example, when the TV left camera detects the direct reflected light 31 and the secondary reflected light 32 as shown in FIG. 6, the TV camera 7 detects only the secondary reflected light component 32 as shown in FIG. be done.

If the bright part is detected by the binarization circuit 9 shown in Fig. 4 and masked on the output of the TV left camera (Fig. 6), the output will be as shown in Fig. 8. , only the direct reflected light from the fillet remains, and the secondary reflected light can be removed.

〔Example〕

An embodiment of the present invention will be explained below with reference to FIG. In the figure, 1a is a light source such as a norogen lamp, 2a is a light guide, 3 is a polarizing plate, 4 is a mirror 5 is a polarizing plate, 6 is a mirror, 7.8 is a TV camera mirror 9 is a binarization circuit, 10 is a 11 is a window generation circuit, 12 is a gate circuit, 15 is an integration circuit, 14 is a comparison circuit, 15 is a synchronization signal generation circuit, 16 is a stage positioning circuit, 17 is an X
Y stage, 18 is a sequence controller, 19 is solder position information, 20 is a printed circuit board on which the inspection target is mounted, 21 is a part mounted on the printed circuit board 20, 22 is a soldered part fillet to be inspected It is.

The light from the light source 1a is passed through the light guide 2a and the polarizing plate 3a.
and enters the soldering part fillet 22 through the soldering part fillet 22. When the inclination angle of the center of the normal fillet is θ, the angle of the light guide is 20 degrees from the perpendicular direction of the printed circuit board, and the direction is arranged in the longitudinal direction of the soldering pad. θ is generally 1
Since the angle is 50 to 500, 2# is arbitrarily set at an angle of 300 to 600. The reflected light from the fillet 22 is branched by a half mirror 4, and a polarizing plate 5 is placed on an optical path perpendicular to the printed circuit board 20, and a TV camera 7 is placed behind it.

Another branching source of the half mirror 4 is a mirror 6 which restores the image mirrored by the half mirror to its original state and detects it with the TV left camera. The polarizing direction of the polarizing plate 5 is perpendicular to the printed circuit board, and the polarizing direction of the polarizing plate 5 is parallel to the plane of incidence. T
The V camera 7 and the T camera mirror are positioned so that they detect the same field of view with the same magnification. Furthermore, a synchronization signal generation circuit 15
In other words, they are driven in the same synchronization. Therefore, the TV camera 7 and the TV left camera output detection signals for the same location at the same time.

The sequence controller 18 reads the soldering position information 19 taught in advance, that is, the X and Y coordinates within the printed circuit board 20, issues a command to the stage positioning circuit 16, drives the XY stage 17, and moves the fillet 22 to be inspected. is positioned on the optical axis extension line of the light guide 2a.

Since the TV camera 7 passes through the polarizing plate 5, light greater than the directly reflected light, that is, secondary reflected light is detected.

The output signal of the TV camera 7 is binarized by the binarization circuit 9, and the original part is +111+1 and the other part is 11φ+
For the TV left camera (+), all polarized light components, that is, direct reflected light and secondary reflection sources are combined and detected.

The output of the TV left camera is input to the masking circuit 10.

The masking circuit 10 is configured so that the output of the binarization circuit 9 is "11'".
When the output of IIφ-binarization circuit 9 is 6φ”, T
V outputs the output of the left camera. The window generating circuit 11 inputs the position of the fillet 22 to be inspected in the TV camera field from the sequence controller 1B, and generates a window 2 containing only one fillet as shown in FIG. 2 for the fillet 22 to be inspected.
3, and according to the timing of the synchronization generation circuit 15, a signal of "I+1 detecting the window section - detecting other sections +1φ" is output to the gate circuit 12. The controller 18 and the comparator 14 generate an integration start signal when the window detection starts and an integration end signal when the detection ends.
When the output of
When Iφ11, it outputs “Akaneφ”.The integrating circuit 13 outputs “Akaneφ”.
The output of the gate circuit 12 is used to start the integration of the window generation circuit 11, and the output of the end circuit 13 is used as a comparator.
It is compared with a certain non-defective level set value, and when the set value is smaller than the set value, it is determined to be defective, and when it is larger than the set value, it is determined to be good. The Geitance controller 18 receives the integration end signal and informs the window circuit 11 of the coordinates of the next window 25 to inspect the fillet 24 as shown in the second factor. After all the fillets within the field of view of the 'l'V camera have been inspected, a new command is issued to the stage drive circuit 16 to move the stage 17 so that the TV camera 7.8 can detect the new fillet. Repeat the above operation to inspect the fillet part of the lead in the same direction.
Regarding the fillet part, as shown in Fig. 3, 1a,
For the set 2a, 3a, in the opposite direction 1b, 2a,
3a, orthogonally, 10*20w3o, and 1d, 2
d and 3d, and perform the inspection by emitting light only from the front side of the fillet to be inspected. Also, like 5a, 3b is polarized in the direction parallel to the printed circuit board 20, and 3o and 5d
The direction of rotation is adjusted so that the light is polarized perpendicularly to the printed circuit board 20.

In this embodiment, a light source such as a halogen lamp is guided by a light guide and polarized by a polarizing plate, but a linearly polarized laser may be used instead. Furthermore, although the integral value within the window is used as the criterion for defect determination, it can be applied to all soldering inspection devices that detect specularly reflected light from soldering fillets.

〔Effect of the invention〕

According to the present invention, since secondary reflected light from other parts can be removed, defects are less likely to be overlooked as in the conventional method, and inspection reliability is improved.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a perspective configuration diagram showing the illumination part shown in the first cause in detail, and FIG. 4 is a diagram showing the window position generated by the window generating circuit shown in the figure. 5 is a diagram showing the relationship between the polarization directions of each polarizing plate shown in FIG. 4, and FIG. 6 is a diagram showing the relationship between the polarization directions of each polarizing plate shown in FIG.
FIG. 7 is a diagram showing a binary image due to total reflection obtained from the rv camera, and FIG. 7 is a diagram showing a binary image due to secondary reflection obtained from the first Tv camera mirror shown in FIGS. 4 and 1. The figure shows a binary image obtained by removing the binary image shown in FIG. 7 from the binary image shown in FIG. 6. Explanation of symbols 1a-d...Light source, 2axd...Light guide. 5a-d...Polarizing plate, 4...Half mirror 5...Polarizing plate, 6...Mirror 7
, 8...'l'V camera, 9... Binarization circuit, 10... Masking circuit. 4th [21 1st Fig. 5 J6121 Fig. 8 Fig. 70

Claims (1)

[Claims] 1. A soldering inspection device that inspects soldered parts where electronic components are mounted on a board includes an illumination means that illuminates the soldered parts with polarized light from an oblique direction, and an illumination means that illuminates the soldered parts with polarized light from an oblique direction; a first imaging means that receives only the polarized light component orthogonal to the polarization plane and converts it into a video signal;
a second imaging means that receives all the polarized light components of the light reflected from the soldering part and converts it into a video signal; and a second imaging means that captures the first image from the video signal obtained from the second imaging means. Soldering characterized by comprising a removing means for removing a brightly detected part in a video signal obtained from the removing means, and the quality of the solder part is determined based on the video signal obtained from the removing means. Inspection equipment.