JPS60238748A - Soldered part inspecting method - Google Patents

Abstract

PURPOSE:To inspect whether a solder fillet is good or not by emitting fluorescence by irradiating excitation light from right above of a soldered part, and detecting the size of a reflecting area of the fluorescence of a solder fillet part. CONSTITUTION:When excitation light 5 is irradiated from right above of an object to be inspected, fluorescence 6 is generated from a base plate 111, but it is emitted directly in the right upper direction, and also reflected fluorescence 7 emitted in the right upper direction after being reflected by a fillet serving as the outside surface of a solder 110 exists, too. Therefore, by taking notice of a fact that its reflecting state is different in accordance with a shape of the fillet, this method is constituted so that whether the fillet is good or not can be discriminated by its size. In this way, the fillet can be inspected with high accuracy even in case of a fined solder 110 part without being affected by the peripheral parts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for inspecting solder portions of electronic components soldered onto a board.

[Background of the invention]

FIG. 1(a) shows how many parts 103 of a flat package type component are soldered to the band 102 on the board.
This shows the state where they are joined through the
The same figure (b) shows a state in which the component pin 104 of the bottle-shaped component is joined to the through hole 105 with a solder portion 106.
Furthermore, in the same figure (C), the surface-mounted part 107 is attached to the band 10 on the board.
8 shows the state in which the fillet is joined at a solder portion 109, but the reality is that small fillet defects have not been detected with good accuracy so far. Figure 2<&)# (
b) shows cross-sections of the solder portion 103 and its surroundings in FIG. 1(a), showing good and bad fillets, respectively; a conventional fillet inspection method is disclosed in Japanese Patent Application Laid-Open No. 55-51342. The following are examples of what has been done. According to this method, the test object is irradiated with light directly above the test object, while the light reflected from the calibration object is detected directly above the test object. By scanning the inspection object by sequentially moving the light irradiation area, the quality of the fillet can be known from the signal waveform of the detected light.

However, as shown in Figure 3 (-), the light 11 comes from directly above.
2 in the form of a spot and detecting the reflected light, there is a problem that the distribution of the amount of reflected light is almost the same regardless of the fillet formation state for steeply sloped fillet parts due to the miniaturization of solder parts. be.

As shown in FIG. 3(b), there is almost no difference between the light amount distribution A for a small fillet and the light amount distribution B for a good fillet.

On the other hand, it is also conceivable that by irradiating the light 112 obliquely upward as shown in FIGS. 4(a) and 4(b), a large difference is caused between the light amount distribution for a small fillet and the light amount distribution C for a good fillet. ing.

However, when performing an inspection in this manner, there is a problem in that the optical path is blocked by surrounding components, making it impossible to perform the inspection.

In addition, Figure 2 (aL (b), Figure 3 (a) and Figure 4
Reference numeral 110 in figure (a). Reference numerals 111 indicate solder and a substrate, respectively.

[Purpose of the invention]

Therefore, it is an object of the present invention to provide a method for inspecting solder parts, which is not influenced by surrounding components and can inspect fillets with good precision even in miniaturized soldering parts.

[Summary of the invention]

For this purpose, the present invention focuses on the fact that organic materials such as polyimide and glass epoxy that make up the base material have a low band gap, but that the band gaps of the solder, iron, and copper that make up the soldering part are high. By irradiating light with a wavelength sufficiently shorter than the wavelength corresponding to the energy of the gap directly above the inspection object as excitation light, fluorescence is generated just above the base material, and the degree of reflection of this fluorescence on the fillet is measured. This allows you to know whether the product is good or bad.

[Embodiments of the invention]

The present invention will be explained below with reference to FIGS. 5 to 9.

First, the principle of the present invention will be explained. As shown in FIG. 5(a), when the excitation light 5 is irradiated directly above the inspection object, fluorescence 6 is generated from the substrate 111, but the fluorescence 6 reaches directly above the inspection object. There is also reflected fluorescence 7 that is reflected by the fillet as the outer surface of the solder 110 and reaches directly above. The degree to which the reflected fluorescent light 7 is reflected directly above the fillet differs depending on the shape of the fillet. That is, when looking at the reflected fluorescence 7 from the fillet directly above, if the fillet is good, the reflected fluorescence 7 will be detected as a thick band, but if the fillet is small, it will actually be detected as a band. Even if the reflection pattern is thick, the reflection surface is made small and therefore the width is small and is detected as a band, or almost no reflected fluorescence 7 can be detected. FIG. 5(b) shows the light amount distribution F when the fillet is good and the light amount distribution E'f when the fillet is small, and there is clearly a difference. Therefore, if the width of the difference is greater than a certain value, it can be determined that the fillet is similar, and if it is less than that, it can be determined that the fillet is small.

Now, the present invention will be specifically explained below regarding flat package type parts, but it can be similarly applied to fillet inspection of bottle type and surface mounted parts as soldering parts.

First, the soldering state of the flat package type component onto the board will be explained. FIG. 6 shows this state. As shown in the figure, a flat package type component 10 has a solder fillet 1 attached to a pad 13 formed in advance on a substrate 12 with a component lead 11 led out from its side surface.
4, the solder fillet 14 is mounted on the board 12, but whether or not a small defect has occurred in the solder fillet 14 is inspected by the solder inspection device shown in FIG. There is. That is, the inspection apparatus according to the present invention is entirely composed of a light irradiation system 19. The fluorescent image detection system and the control system N are used to drive and control the X-Y table on which the substrate is mounted depending on the control system N. First, the irradiation of the excitation light onto the soldering part will be explained. This is done by the light irradiation system 19. The spot-shaped excitation light from the K laser 15 is made into a slit by cylindrical lenses 16 and 17, and is irradiated onto the soldering portion via a dichroic mirror 18 that reflects only the wavelength of the excitation light.

By irradiating this excitation light, fluorescence is generated from some portions of the substrate 12 in the vicinity of the substrate 12, and an image of this fluorescence is detected by a fluorescence image detection system B. The direct fluorescence from the substrate 12 portion and the reflected fluorescence from the solder fillet are absorbed by the dichroic mirror 18.
．． The light is detected by a solid-state TV camera n via an imaging optical system and an excitation light cut filter 21.

Prior to the inspection, first, the XY table row is moved to the inspection start position via the table controller in accordance with a command from the overall control section 5, and the laser 15 is turned on. Therefore, by repeatedly performing the following operations, the soldered portion can be inspected.

That is, the solid-state TV camera η detects a fluorescent image in the inspection target area with the inspection target component lead of the flat package component 10 positioned in the inspection target area by driving the X-Y table 28. FIG. 8 shows an example of a fluorescent image detected in this manner, with only the soldered portion extracted. As shown in 1, there are detection images G and H corresponding to soldered parts in detection 14 where the ground corresponds to the board, but both detection images G and H are solder fillet images. It now includes a gap. Incidentally, the detected images G and H show those with a good solder fillet and a solder fillet with a small defect, respectively. If the solder fillet is good, the width between the solder fillet images is detected as large, but in the case of a small solder fillet defect, the width is detected as small, or almost no solder fillet image can be detected. It is something.

Therefore, the quality of solder fillets can be determined by detecting the width between solder fillet images and determining whether the width is one foot or more.

To explain this determination in detail, the defect determination section first compares the fluorescence image as shown in FIG.
As shown in the figure, only the pad part or the soldered part is extracted. Next, by adding this in the y direction, the position x
A one-dimensional light amount function as the f parameter is obtained as shown in FIG. 9(b), and the value of the light amount function is binarized using a predetermined threshold. If it is above the threshold value, it is set as 'I', and if it is less than that, it is set as 10' and binarized as shown in FIG. 9(e).
111 in the binary light amount function obtained in this way
By measuring the entire width of the part and comparing this value with a separately predetermined threshold value, the quality of the solder fillet at that part (rad part or soldering part) can be easily and quickly determined. The reason why the fluorescent images are added in the y direction in the above process is that the entire solder fillet is considered without being affected by minute irregularities or noise, and the quality of the solder fillet can be accurately determined. This is for the purpose of making a judgment.

The present invention is as described above, but as an excitation light source, a laser having a wavelength of 600 rays or less, or a combination of a light source containing a wavelength component of 600 rays or less, such as a mercury lamp or an ultraviolet fluorescent light, and an optical filter is used. obtain. In addition, devices for detecting fluorescent images include a TV camera using an image pickup tube, a complete combination of a scanning mechanism such as a linear sensor and a galvano mirror, and a sensor for detecting the amount of light at one point such as a photomultiplier tube and a scanning device. There are various possibilities, such as a combination of mechanisms.

〔Effect of the invention〕

As explained above, the present invention generates fluorescence only from the substrate part by the excitation light irradiated directly above the inspection object,
The quality of the solder fillet can be determined by detecting the degree of reflection of this fluorescence on the solder fillet from directly above the object to be inspected. Therefore, according to the present invention, the quality of the solder fillet, that is, the soldered part, can be inspected with good precision even in the case of miniaturized soldered parts, without being affected by surrounding parts. It has the effect of gaining 7 points.

[Brief explanation of drawings]

Figures 1 (a), (b), and (e) are diagrams showing the mounting and joining states of various components on the board by soldering parts, and Figure 2
Figures (a) and (b) are cross-sectional views of the soldered part and its surroundings in Figure 1 (,), showing good and bad fillets, and Figure 3 (a) and (b) are cross-sectional views of soldered parts and their surroundings. Figures 4(a) and 4(a) are diagrams for explaining problems when detecting reflected light by irradiating light directly above the gradient fillet.
b) is a diagram for explaining that the quality of the fillet can be inspected by irradiating light from diagonally above the inspection object, and FIG. 5(a), ω) is a diagram for explaining the present invention in detail. 6 is a diagram showing the state of soldering of flat package type components onto a board, FIG. 7 is a diagram showing a solder part inspection device according to the present invention together with a component mounting board, and FIG. A diagram showing an example of a fluorescent image detected by a solid-state TV camera regarding some parts of the solder in this configuration, FIG. 9(a),
), (0) is a diagram for explaining an example of processing by the defect determination section in the same configuration. 10... Flat package type component, 11... Component lead, 12... Board, 14... Solder fillet, 15... K laser, 16.17... Cylindrical lens, 18... Dichroic Miller, Ka...
- Imaging optical system, 21... excitation light cut filter, n.
・・Solid-state TV camera, ・Defect determination section, 25...
Overall control section, %...table controller, fat...
X-Y Table Agent Patent Attorney Tadashi Akimoto Figure 1 (0) (C) Figure 2 (b) Figure 3 (q) (b) Inn 1i Figure 4 (b) Figure 5 ( b) Figure 6 Figure 7 Figure 8 Figure 9 (0) (C”l lm-Bond X (b)

Claims (1)

[Claims] This is a method for inspecting the quality of solder fillets at various parts of solder on various parts mounted on a board. By irradiating an excitation source directly above the solder part to be inspected, fluorescence is generated only at the base material of the board. , detect the size of the reflective area of the fluorescent solder fillet directly above the solder, and inspect the quality of the solder fillet at the solder based on the size of the detected reflective area. A method for inspecting several parts of solder.