JPH0455099B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a bonding state detection method and apparatus for determining the bonding state of a soldered portion of an electrical component such as an LSI.

[Background of the invention]

In electrical products, defective soldering is absolutely unacceptable as it directly leads to product defects.

Particularly when a large number of components are mounted in a high density, such as in a large computer, the number of soldering parts becomes enormous, and in order to increase the reliability of the product, it is necessary to
It is necessary to inspect all of these. Furthermore, it is necessary to simultaneously satisfy the above-mentioned reliability and improvement of productivity, and it is necessary to efficiently inspect a huge number of soldered parts.

For these reasons, there is currently an increasing demand for automatic visual inspection of soldered parts. It is particularly difficult to inspect the soldered joints of flat package type components.

For example, as shown in Figure 1, the soldering part 1 of a flat package type component, the wire bonding 2 of LSI etc., the joining part 5 when joining flat objects 1 and 2, etc. It is difficult to inspect whether it is good or bad.

That is, defects in the soldered parts include those where the joints are completely separated, those where the joints are only in contact but not completely joined, and those where the joints are misaligned.

Among the joints with a flat appearance as shown in Fig. 1, those that are completely separated or that are only in contact but not completely joined are observed as if they were joined. Defects are extremely difficult to detect.

There are two methods for conventional visual inspection of soldered joints of flat package components.

The first method is to vibrate the soldering part at a frequency of 60Hz to 200KHz by bringing a vibrator into direct contact with the soldering part, and detecting the vibration of the soldering part at that time with a vibration detector. Defects are determined based on the state of vibration at this time (US Pat. No. 4,218,922).

The second method is to vibrate the soldered part by directly touching the vibrator to the soldered part and change the vibration frequency applied to the soldered part in the range of 20Hz to 1MHz or 150KHz to 650KHz. There is a system that measures the frequency response of the soldered part by detecting the magnitude of vibration with a vibration detector, and then determines defects in the soldered part based on this frequency response (US patent No. 4287766).

However, all of these methods have the following drawbacks. That is, in the conventional method described above, a vibrator is brought into direct contact with the soldering part to vibrate the soldering part, and the vibration is detected using a vibration detector. 1) The vibrator must be brought into precise contact with all soldered parts, which slows down the inspection speed.

(2) It is difficult to maintain a constant state of contact between the soldered part, the vibrator, and the vibration detector, resulting in low reliability.

Therefore, the conventional methods described above cannot support the so-called high density mounting of large computers, where many components are mounted, and it is difficult to develop inspection methods and equipment that satisfy reliability and productivity. The reality is that it is urgent.

[Purpose of the invention]

SUMMARY OF THE INVENTION In order to solve the above-mentioned drawbacks of the prior art, it is an object of the present invention to quickly and reliably check the quality of the joints of a plurality of soldered joints arranged in parallel at desired intervals. It is an object of the present invention to provide a method and device for detecting a bonding state that enables determination.

[Summary of the invention]

In order to achieve the above object, the present invention indirectly vibrates a plurality of objects to be inspected arranged in parallel at a desired interval, and irradiates the excited plurality of objects to be inspected with laser light. A linear sensor disposed with its longitudinal direction facing the direction in which the plurality of objects to be inspected is arranged side by side, detecting speckle light detected by interfering the diffracted lights from the plurality of objects to be inspected through a detection optical system. The linear sensor receives the light by placing it in a focused state in the longitudinal direction and in a defocused state in a direction substantially perpendicular to the longitudinal direction to reduce the influence of speckle light from an adjacent object to be inspected. This bonding state detection method is characterized in that the bonding state of each object to be inspected is discriminated and determined based on the image signal detected from the image signal. The present invention also provides an excitation means for indirectly vibrating a plurality of objects to be inspected arranged in parallel at a desired interval, and a laser beam applied to the plurality of objects to be inspected vibrated by the excitation means. A laser beam irradiation means for irradiating speckle light detected by interfering with diffracted light from the plurality of objects to be inspected is arranged with the longitudinal direction facing the direction in which the plurality of objects to be inspected are arranged side by side. Detection optics that is in a focused state in the longitudinal direction of the linear sensor and in a defocused state in a direction substantially perpendicular to the longitudinal direction to reduce the influence of speckle light from an adjacent object to be inspected, and then receive the light by the linear sensor. A bonding state detection device comprising: a bonding state detection system; and bonding state determining means for discriminating and determining a bonding state of each object to be inspected based on an image signal detected from a linear sensor of the detection optical system. be.

[Embodiments of the invention]

First, the circumstances leading to the present invention will be explained.
The inventors studied the inspection of soldered parts from the viewpoints of reliability and productivity in view of the trend toward higher and higher densities.

That is, the inventors did not directly vibrate the soldering part as in the past, but instead vibrating the soldering part indirectly, and by making the vibration conditions for the soldering part the same for each part to be inspected. The technical challenge was to improve reliability and inspection speed, and to indirectly detect and judge vibrations in soldered parts.

In this study, when an object to be examined is irradiated with a laser beam and observed with a sensor, spots with high contrast called laser speckles are observed.

This laser speckle is the result of laser light irradiated onto the surface of an object that has minute irregularities that can be considered a random diffraction grating, diffracted by the diffraction grating, and these diffracted lights mutually interfering with each other. It is.

This laser speckle has the property of moving as the object moves, and by using this property, the vibration of the soldering part is detected by observing the movement of this laser speckle with an optical sensor. I found out what to do.

FIG. 3 is a diagram showing the principle at that time. In the figure, a laser beam emitted from a laser light source 10 is irradiated onto an object 12 through a half mirror 11, and the laser speckle generated at that time is focused by a focusing optical system 13 and observed by an optical sensor 14. It is something.

In this optical system, the amount of movement Ax of the laser speckle in the x direction is expressed by the following equation.

A _x = b + △/a・a _x −a/b・△・Ωy ...(1) where a: Distance between the object and the lens b: Distance between the lens and the imaging position Λ: Defocus amount from the imaging position _ax : Amount of movement of the object in the x direction Ωy: Amount of rotation of the object around the y-axis From the relationship in equation (1) above, the sensor is placed on the imaging plane (Δ=
0), the amount of movement of the spectrum will be equal to the amount of movement of the object multiplied by the magnification. On the other hand, by placing the sensor at a defocus position that is △ away from the image plane, the laser speckle will move even when the object rotates, and by setting the defocus amount to a large △, the laser speckle will be slightly weaker. Even small rotational movements can be interpreted as a large amount of laser speckle.

Furthermore, although the laser speckle remains within a narrow range at the imaging position, it expands at the defocus position.

In this case, when the objects to be inspected are lined up at a small pitch, if the laser speckles are spread out, the laser speckles from each object will overlap, making it difficult to distinguish between them. Become.

Therefore, in order to prevent this, the present invention inserts a cylindrical lens to maintain the imaging relationship in the direction in which the objects to be inspected are lined up, and performs defocusing in the direction perpendicular to this. This makes it possible to sufficiently separate the laser speckles and increase the amount of defocus, thereby sufficiently increasing the vibration detection sensitivity.

Furthermore, if a diffraction grating is used instead of a cylindrical lens, a diffraction image will be observed, and in this case as well, it is possible to defocus in only one direction.

Generally, there are two types of optical sensors: storage type and non-storage type. Among these, the storage type sensor is of the type that detects the amount of incident light integrated over a certain period of time, while the non-storage type sensor is of the type that detects temporal fluctuations in the amount of incident light.

The one shown in Fig. 4 is based on a non-accumulative type sensor, and when a vibrating laser speckle is detected by a non-accumulative type sensor, when the position of the laser speckle is vibrating, ( As shown in b), the amount of detected light is also observed to be oscillating, and for a laser speckle that is not vibrating, the amount of detected light is observed to be constant as shown in (a).

On the other hand, in the case of an accumulation type sensor, as shown in Figure 5, if a vibrating laser speckle is detected, the laser speckle is vibrating, so (b)
A blurred image is observed as shown in (a), and if the laser speckle is not vibrating, a laser speckle image with strong contrast is observed as shown in (a). Note that in the case of an accumulation type sensor, the accumulation time must be longer than the vibration frequency.

In this way, the vibration of the soldering part is
The laser speckles were detected as speckles, and it was confirmed that by observing these laser speckles with an optical sensor, it was possible to judge whether the soldered parts were good or bad.

FIG. 6 is a supplementary explanatory diagram of the bonding state detection device of the present invention.

In FIG. 6, the inspection device includes an excitation system 16, a laser irradiation system 20, a detection optical system 23, and a control section 3.
1.

First, the vibration system 16 indirectly vibrates the lead part 8 of the component 7 such as an LSI, and in this embodiment, turbulent air is jetted from the air nozzle 15 toward the soldering part. Vibration is applied to the reed portion 8.

The laser irradiation system 20 includes an irradiation optical system 18 and a half mirror 19, and irradiates the soldering portion with laser light from the laser light source 17.

The optical detection system 23 includes a condensing optical system 21 with an image plane set at a defocus position for detecting laser speckles, and an accumulation type linear sensor 22. The optical detection system 23 detects the laser speckle and observes it with the accumulation type linear sensor 22. do.

The control device 31 positions the object to be inspected.
- A table controller 27 that controls the Y table 24, a jet flow control section 25 that controls the air jet jet ejected from the air nozzle 15, a sensor drive circuit 26,
It incorporates a laser control circuit 28, a defect determination section 29, and an overall control section 30.

In this embodiment configured as described above, the overall operation is performed as follows (see FIG. 7).

Prior to the inspection, first, the general control unit 30 issues a command to move the X-Y table 24 to the inspection start position, start irradiating the object with a laser beam, and start blowing air from the air nozzle 15. .

In this way, the preparations before the inspection are completed, and then the inspection is started. First, the X-Y table 24 is driven by the table controller 27 to position the flat package component 7, so that the soldered portion of the lead 8, which is the object to be inspected, is irradiated with a laser beam, and at the same time the lead 8 is Air will be blown out into the soldering area.

In this state, a good lead 8 that has been completely soldered does not vibrate, but if the soldering is incomplete, the lead 8 vibrates.

In this way, the laser beam irradiated onto the object to be inspected is focused by the focusing optical system 21, and the laser speckle is observed by the storage type linear sensor 22.

The laser speckle obtained by this storage type linear sensor 22 is as shown in FIG.
In this case, since the reed 8 does not vibrate, an image 32 with a narrow pitch and severe irregularities is observed. On the other hand, in the case of a defective product, since the lead 8 is vibrating, the laser speckle also vibrates, and since this is detected in an integrated form, a smooth image 33 with a large pitch is observed.

In this way, depending on whether the soldering part is good or bad,
The images captured by storage type linear sensors are different. Based on the difference between these images, the defect determining section 29 makes a determination.

That is, the number of peaks in the amount of light in the laser speckle image appearing corresponding to each lead 8 that is the object to be inspected is measured, and a determination is made based on whether the number is greater or less than a predetermined threshold value.

Alternatively, calculate the average value of the pitch (distance between peaks) between the maximum values of the light intensity of the laser speckle image,
The judgment can be made based on whether this value is smaller than a predetermined threshold value, or the average value of the absolute value of the differential value of the light intensity of the laser speckle image is calculated, and whether this value is larger than the predetermined threshold value. You can also judge by how small it is.

For example, in the case of a good lead 8, the image is a thin uneven image, so if the number of peaks is greater than a predetermined threshold, it is determined to be a good product, and if it is less than a predetermined threshold value, it is determined to be a defective product.

In this determination, the vibration of the lead 8, the observation of the laser speckle with the storage type linear sensor 22, and the irradiation of the laser light are controlled by the control device,
Moreover, since the inspection is performed indirectly on the object to be inspected, the same conditions are applied to all the leads 8 to be inspected, and it is possible to make an inspection judgment completely responsive to the quality of the soldered portion.

In addition, by exciting with an air jet that utilizes turbulence, vibration can be generated over a wide range of frequencies, including the natural frequency of the leads 8 when the soldering is completely separated, resulting in large amplitude vibrations. Become.

Also, since the storage type linear sensor 22 is used,
It is possible to capture weak signals, obtain enough laser speckle to detect even low-output laser light, and in combination with the above-mentioned increase in amplitude, accurate detection is possible.

An embodiment of the present invention will be specifically described below. FIG. 9 shows an embodiment of the bonding state detection device of the present invention, which differs from the embodiment shown in FIG. 6 in that an AC magnet 34 is used in the excitation system 16, and the detection optical system 23, while maintaining the imaging relationship in the x direction, y
The difference is that a cylindrical lens -35 for defocusing only in the direction is added, making it possible to inspect even the leads 8 arranged at a small pitch, and that the defect determination method is different.

In this embodiment configured as described above, the difference from FIG. 6 in terms of the overall operation of the device and the defect determination method is that, as shown in FIG. is irradiated, and an image of the same waveform is observed using the storage type linear sensor 22 (see FIG. 11). Next, activate the AC magnet 34,
The lead 8 is vibrated, and changes in the laser speckle image before and after the vibration are confirmed to determine defects in the soldered portion.

For example, if the image of the laser speckle before excitation is as shown in Figure 11, and the image after excitation changes as shown in Figure 8, then the differential value of the laser speckle image before and after excitation should be calculated. It is binarized and compared by taking the cross-correlation between before and after the vibration, and it is determined whether the correlation coefficient is larger or smaller than a predetermined threshold value. In this case, a small one is determined as a defect.

In addition, as examples of other judgment methods, (1) Calculate the ratio or difference in the average pitch of the maximum point of the laser speckle light intensity before and after the excitation, and if this value is larger than a predetermined threshold value, it is considered a defect. How to determine as.

(2) A method of measuring the ratio or difference in the number of maximum values of the laser speckle light intensity before and after excitation, and determining as a defect if this value is smaller than a predetermined threshold.

(3) A method of performing fast Fourier transform on the amount of laser speckle light before and after excitation, calculating the ratio or difference of frequencies that take the maximum value in the frequency domain, and determining a defect if this value is smaller than a predetermined threshold value. .

(4) A method of calculating the ratio or difference between the average value of the absolute value of the differential value of the laser speckle light intensity before and after excitation, and determining a defect if this value is smaller than a predetermined threshold.

etc. can be mentioned.

In the case of this embodiment, the cylindrical lens 35
Since the lead 8 is inserted between the leads 8 (lead 8
It is possible to sufficiently separate the laser speckle of a component (such as a component in which multiple parts are arranged side by side) and to obtain a sufficiently high vibration detection sensitivity.

FIG. 12 shows yet another implementation. This embodiment differs from the embodiments shown in FIGS. 6 and 9 in that a cylindrical lens 35 is used in addition to the air nozzle 15 in the excitation system 16, and the control section includes a laser beam. A buffer 40 is provided for accumulating temporal variations in speckles, and the accumulated temporal variations in laser speckles are analyzed by a spectrum analyzer to determine the quality of the soldered parts.

That is, the inspection device includes an excitation system 16 having an air nozzle 15, a laser irradiation system 20 including a laser light source 17, an irradiation optical system 18, and a half mirror 19,
Optical detection system 2 including a condensing optical system 21, a cylindrical lens 35, and a non-accumulative linear sensor 39
3, table controller 27, air jet control section 25, sensor drive circuit 26, laser control circuit 2
8, a defect determination section 29, an overall control section 30, and a control device 31 containing a buffer 40.

The overall operation of this inspection device is performed as follows (see FIG. 7). First, prior to the inspection,
In response to a command from the overall control unit 30, the X-Y table 24 is moved to the inspection start position and irradiation of the upper surface of the lead 8 with the laser beam is started.

Next, by the table controller 27,
- Drive the Y table 24 to connect one side of the flat package type component 7 (this one side has many leads 8).
The leads 8 (which are provided in parallel) are positioned at the inspection position, and the air nozzle 15 starts spraying air toward the soldering area.

By blowing air in this manner, defective soldered products are indirectly vibrated. In this case, those with good soldering do not vibrate. This state is observed by a non-storage type parallel output linear sensor 39, and the time fluctuation of the laser speckle as shown in FIG. 4 is obtained.

The temporal fluctuations of the laser speckle corresponding to each lead obtained in this manner are accumulated in the buffer 40, and defects are determined based on the accumulated temporal fluctuations of the laser speckle.

That is, the non-storage type parallel output linear sensor 3
The laser speckle obtained at 9 is a good lead 8.
Because it does not vibrate, the amount of detected light hardly changes as shown in Figure 4a, but the defective lead 8
Since the reed 8 vibrates at its own natural frequency, the amount of detected light also oscillates as shown in FIG. 4b.

The time variation of this laser speckle is analyzed using a spectrum analyzer to obtain the image shown in FIG.

It is determined whether the position of the peak frequency in this frequency region is higher than a predetermined threshold value, and in this case, a high lead is determined to be defective.

The following methods can be considered as this determination method.

(1) Time fluctuation of laser speckle in floating form 2
The value is converted into a value, the number that changes from 0 to 1 or from 1 to 0 is calculated, and a lead whose value is larger than a predetermined threshold value is determined to be defective.

(2) Similar to (1) above, binarize in floating form, 0 → 1,
Alternatively, the average value of the pitch changing from 1 to 0 is calculated, and a lead whose value is smaller than a predetermined threshold value is determined to be defective.

The following sensors are used in this embodiment.

(1) A sensor capable of random scanning using an image detector, etc. When this sensor is used, it is possible to sequentially scan a large number of leads provided in parallel to detect temporal fluctuations in the amount of incident light.

(2) Point sensors such as photomars. When this sensor is used, inspection is performed by driving the X-Y table in a step-and-repeat manner one lead at a time.

As in this example, when measuring the temporal fluctuations of the laser speckle, the vibration frequency of the object to be inspected can be known, which increases the amount of information needed to determine pass/fail, and eliminates even the slightest defect. Don't miss anything and it's reliable.

Also, as explained in the embodiment shown in FIG. 6, by jetting air at different flow rates, a vibrating turbulent air jet is obtained, and thereby the object to be inspected is vibrated. For example, even if an unconnected soldered part cannot vibrate at its natural frequency, it will vibrate at the frequency of the air being injected, so it goes without saying that this can be detected.

Furthermore, it goes without saying that the cylindrical lens has the same effect as explained in the embodiment shown in FIG.

In the above description, an air jet and an alternating current magnet were used as examples of the excitation system, but any system that can indirectly excite the vibration may be used, and is not limited thereto. For example, it may be a gas other than air.

Furthermore, although a cylindrical lens has been described as an example of an optical component for defocusing, the present invention is not limited to this, and a diffraction grating may also be used.

Furthermore, although the storage type and non-storage type optical sensors have been explained, the present invention is not limited to these types.
For example, it goes without saying that a two-dimensional sensor may be used.

The three embodiments shown above are representative embodiments, and the combinations of the elements of the excitation system, the elements of the detection optical system, and the determination method described above are not limited to these.

〔Effect of the invention〕

As explained above, according to the present invention, in order to cope with the trend toward higher density, the soldering parts of flat package type parts, the wire bonding parts of LSI, etc. are arranged in parallel at desired intervals. By reducing the influence of speckle light from adjacent joints (objects to be inspected) on multiple joints (objects to be inspected), it is possible to check the joint status of each joint in a non-contact manner.
Moreover, it has the effect of being able to discriminate and test with high reliability and high speed.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams, and FIG. 1a shows the soldering part of the flat package type part;
Figure 1b is a perspective view showing the wire bonding part of LSI etc., Figure 1c is a perspective view showing the soldering part of a general flat part, and Figure 2 is a perspective view showing the soldered state of flat package parts. It is. Fig. 3 is a perspective view showing the principle of the present invention, and Fig. 4 is a diagram showing speckle detection waves by a non-storage type sensor. The detected wave in this case is shown. FIG. 5 is a diagram showing images of speckles detected by the storage type sensor, in which a shows an image that appears when the product is a good product and b shows an image that appears when the product is a defective product. FIG. 6 is a diagram showing the main part configuration for supplementary explanation of the bonding state detection device of the present invention, FIG. 7 is a block diagram for explaining the operation of the device shown in FIG. 6, and FIG. , FIG. 9 is a diagram showing the main configuration of an embodiment of the bonding state detection device of the present invention, and FIG. 11 is a diagram showing a detection waveform of a speckle obtained by the bonding state detection device shown in FIG. 9, and FIG. 12 is a block diagram for explaining the operation of the bonding state detection device shown in FIG. FIG. 13, a main configuration diagram showing another embodiment of the state detection device, is a diagram showing a detected waveform of speckles obtained by the bonding state detection device shown in FIG. 12, where a indicates a non-defective product;
b is a diagram showing a waveform of a defective product. 8...Reed, 15...Air nozzle, 16...
Excitation system, 17...Laser light source, 18...Irradiation optical system, 19...Half mirror, 20...Laser irradiation optical system, 21...Condensing optical system, 22...Accumulation linear sensor, 23...Detection Optical system, 25...Jet flow control unit, 26...Sensor drive circuit, 27...Table controller, 28...Laser control circuit, 29
... Defect determination section, 30 ... Overall control section, 34 ...
AC magnet, 35... Cylindrical lens, 40...
...Buffer that accumulates detection signals.

Claims (1)

[Claims] 1. A plurality of objects to be inspected arranged in parallel at a desired interval are indirectly vibrated, a laser beam is irradiated to the plurality of objects to be inspected that have been excited, and the plurality of objects to be inspected are The speckle light detected by interfering the diffracted light from the object to be inspected through the detection optical system is transmitted in the longitudinal direction of a linear sensor arranged with its longitudinal direction facing the direction in which the plurality of objects to be inspected are arranged side by side. The linear sensor receives light in a focused state and in a defocused state in a direction substantially orthogonal to the longitudinal direction, and discriminates and determines the joining state of each object to be inspected based on the image signal detected from the linear sensor. A bonding state detection method characterized by: 2. A vibration excitation means that indirectly vibrates a plurality of objects to be inspected arranged in parallel at a desired interval, and a laser beam that irradiates the plurality of objects to be inspected vibrated by the excitation means with laser light. An irradiation means and a linear sensor disposed with the longitudinal direction facing the direction in which the plurality of objects to be inspected are arranged side by side, emitting speckle light detected by interfering diffracted light from the plurality of objects to be inspected. a detection optical system that receives light with the linear sensor while placing it in a focused state in the direction and in a defocus state in a direction substantially perpendicular to the longitudinal direction; A bonding state detection device comprising bonding state determining means for discriminating and determining a bonding state of an object to be inspected. 3. The detection optical system is configured with a cylindrical lens or a diffraction grating, which brings the linear sensor into a focused state in the longitudinal direction and into a defocused state in a direction substantially orthogonal to the longitudinal direction. The bonding state detection device according to item 2.