JPH0252981B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and apparatus for detecting the joint state of a plurality of parts.

[Background of the invention]

Examples of joints to be inspected include soldering parts 1 of flat package components (FIG. 1a) and wire bonding parts 2 of LSIs and the like (FIG. 1b). Defects in these objects include cases where the joints are completely separated, cases where the joints are only in contact but not completely connected, and cases where the joints are misaligned. In particular, among these defects, those where the joints are completely separated or only in contact are not only difficult to inspect automatically, but also
Since visual inspection is also difficult, there is a particular need for inspection automation. All of these objects to be inspected are a first object 3 and a second object 4, as shown in Figure 1c.
and a joint portion 5 between them. Therefore, the following explanation is limited to the inspection of flat package components with no lead contact defects (including those that are completely floating and those that are in contact but are not soldered). do. The same thing can be said about the inspection of other objects having the structure shown in FIG.

As conventional techniques, there are two methods by Vattelle Labs described below as methods for visually inspecting the soldered portions of flat package components.

The first method is to excite the vibration at a frequency of 60Hz to 200KHz by bringing the vibrator into contact with the soldered part, and detect the vibration state at that time with a vibration detector. Defects are determined based on the (US Patent 4218922) The second method is to bring the vibrator into contact with the soldered part to generate a signal from 20Hz to 1MHz or from 150KHz to
The soldered part is vibrated at a frequency of up to 650KHz, and the magnitude of the vibration at this time is detected by a vibration detector to measure the frequency response of the soldered part, and defects are determined based on this frequency response. Let's do it. (USPatent 4287766) Since these methods perform vibration excitation and vibration detection using a contact method, they have the following drawbacks.

1 Detection speed is poor.

2. It is difficult to maintain constant contact between the soldered part, vibrator, and detector, resulting in low test reliability.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for detecting a bonded state, which eliminates the drawbacks of the above-mentioned prior art and enables fast and reliable detection of a bonded state in inspecting the bonded state of parts.

[Summary of the invention]

In order to achieve the above object, the present invention vibrates a target object in a non-contact manner by means of a gas jet, magnetic force, etc.
This bonding state detection method is characterized in that the vibration state is detected in a non-contact manner using optical means, and the detected vibration state is analyzed to detect the bonding state of the object to be inspected. Furthermore, the present invention is characterized by an apparatus for implementing the above method. That is, the present invention provides an excitation means composed of a gas injection means or an excited magnetic force generating means for vibrating an object in a non-contact manner, and an optical system that detects the vibration state of the object excited by the excitation means. comprising an optical means for detecting the vibration state and an analysis means for analyzing the vibration state detected by the optical means,
The purpose is to detect the joint state of objects. The above-mentioned optical means may include, for example, an irradiation means for irradiating a laser and a detection means for detecting fluctuations in the laser spectrum observed from the object.

[Embodiments of the invention]

Hereinafter, the present invention will be specifically explained based on embodiments shown in the drawings.

That is, the principle of the present invention is shown below.

If the bonded state of the objects shown in FIG. 1 is different, the elastic properties of the bonded state will be different. Therefore, by vibrating the joint and detecting the vibration state at that time, it is possible to determine an abnormality in the joint state, that is, a defect.

For example, when we vibrate the leads of a good product and a defective product at the soldered part of a flat package type component shown in Figure 2, the good lead hardly vibrates because it is firmly fixed to the board, but the lead of the defective product hardly vibrates. is not connected to the board and vibrates violently. By measuring the magnitude of this vibration, it is possible to determine that a device that generates vibrations of a predetermined magnitude or more is defective.

On the other hand, vibration detection is performed using the following method.
When an inspection target is irradiated with a laser and viewed with a sensor, high-contrast spots called laser speckles are observed. Laser speckle is a phenomenon in which a laser beam is irradiated onto the surface of an object that has minute irregularities that can be considered as a random diffraction grating, and the diffraction grating causes diffraction, and the diffracted light beams interfere with each other. It is something. Since this speckle moves as the object moves, the movement of the object can be detected by observing the movement of this laser speckle with an optical sensor.

Generally, there are two types of optical sensors: storage type and non-storage type. A storage type sensor is a type that detects the time-integrated amount of incident light, and a non-storage type sensor is a type that detects time fluctuations in the amount of incident light.

If a vibrating laser speckle is detected with a non-storage type sensor, since the position of the speckle spot is vibrating, the detected light intensity at a certain point will also be observed as oscillating, and the laser speckle that is not vibrating will be In contrast, the amount of detected light is observed to be constant. (Fig. 11) If a vibrating laser speckle is detected with an accumulation type sensor, the position of the speckle spot will be vibrating, so if the accumulation time is longer than the vibration period, the detected light amount at a particular point will be , is a constant value that is almost independent of location. For this reason, the distribution of detection signals for speckles that do not vibrate is such that speckles with strong contrast are observed as shown in Figure 3a, and speckles that are vibrating have no contrast as shown in Figure 3b. A blurry image is observed.

Next, a first embodiment of the present invention will be specifically described using the drawings. FIG. 2 shows an example of an object whose bonded state is to be detected. That is, a wiring pattern formed on the substrate 1 and a component lead 8 provided on a component 7 such as an LSI are soldered together.

FIG. 4 shows the configuration of an inspection apparatus for determining defects without lead connection in flat package type parts. The inspection device includes an air nozzle 10 for blowing a turbulent air jet onto multiple soldered parts to be inspected and vibrating unconnected leads.
The vibration system 11 using
A laser irradiation optical system 15 consisting of a laser 12, an irradiation optical system 13, and a half mirror 14 for irradiating a beam, and a condensing optical system 16 with an image plane set at a focused position or a defocus position for detecting laser speckles. and storage type linear sensor 17
a detection optical system 18, an X-Y table 19 for positioning the inspection object, a jet flow control section 20 for controlling the air jet, a sensor drive circuit 21, a table controller 22, a laser control circuit 23, a defect determination section 24, and the whole. It consists of a control section 26 consisting of a control section 25 .

The overall operation of the inspection will be outlined using FIG. 5. Prior to the inspection, the overall control unit 25
In response to this command, the X-Y table 19 is moved to the inspection start position, the laser beam starts irradiating the upper surface of the lead to be inspected, and the air nozzle 10 starts spraying an air jet to the soldering part.

Next, perform the inspection by repeating the following operations. The X-Y table 19 is driven to position the leads on one side of the flat package component 7 to be inspected to the inspection position, a laser beam is irradiated onto the top surface of the leads, and an air jet is injected to the soldered part. make it like this. In this state, the good reeds do not vibrate, but the defective unconnected reeds vibrate. This state is observed by an accumulation type linear sensor 17 whose sample rate is higher than the vibration frequency, and the laser speckle shown in FIG. 6 is obtained. Defects are determined based on the state of the laser speckle at the location corresponding to each lead. Reference numeral 27 indicates a laser speckle for a good product in the first embodiment, and 28 indicates a laser speckle for an unconnected lead of a defective product in the first embodiment.

Next, the defect determination method will be described. As shown in FIG. 6, the laser speckle obtained by the accumulation type linear sensor 17 has a narrow pitch and a sharply uneven image in the case of a good lead because the lead is not vibrating.
However, in a defective L lead that is connected, the lead is vibrating, the speckle is vibrating, and this is detected in an integrated form, so a smooth image with a large pitch is observed. This difference is determined by counting the number of locations where the light intensity of the speckle image corresponding to each lead takes a maximum value, and leads that are smaller than a predetermined threshold value are determined to be defective.

Variations of this judgment method include the following.

The average value of the pitch between the maximum values of the light intensity of the speckle image is calculated, and a lead for which this value is smaller than a predetermined threshold value is determined to be defective.

The average value of the absolute values of the differential values of the light intensity of the speckle image is calculated, and a lead for which this value is smaller than a predetermined threshold value is determined to be defective.

According to this embodiment, there are the following effects.

Since the vibration is performed using an air jet that utilizes turbulence, the vibration is generated over a wide range of frequencies, including the natural frequency of the defective unconnected lead, making it possible to obtain vibrations with large amplitudes. can.

Since it uses an accumulation type sensor, it is possible to capture weak signals, and it is possible to obtain enough laser speckle to detect even a low output laser.

Since the determination method is simple, the speed can be increased and the device configuration is simple.

Next, a second embodiment of the present invention will be described. The configuration of the inspection device to be inspected is similar to that of the first embodiment.
As shown in the figure. The inspection device includes a vibration system 11 using an AC magnet 29 to vibrate a component lead 8 made of a paramagnetic material such as iron, and a laser 12 and irradiation optics to irradiate a laser beam to a soldered part. System 1
3, a laser irradiation optical system 15 consisting of a half mirror 14, a detection optical system 18 consisting of a condensing optical system 16 for detecting laser speckles and an accumulation type linear sensor 17, and a positioning X-Y The table 19, the magnetic field control unit 31 for controlling the AC magnet 29, the sensor drive circuit 21 for extracting sensor signals, the table controller 22, the laser control circuit 23, and the defect determination unit 2
4 and a control section 26 consisting of an overall control section 25.

The overall operation of the inspection will be outlined using FIG. 8. Prior to the inspection, the overall control unit 25
In response to this command, the X-Y table 19 is moved to the inspection start position, and irradiation of the laser beam onto the top surface of the lead to be inspected is started.

Next, perform the inspection by repeating the following operations. The X-Y table 19 is driven to position the lead on one side of the flat package component 7 to be inspected to the inspection position, and the laser speckle image shown in FIG. 9 is obtained. Reference numeral 31 indicates a laser speckle for a good product before vibration in the second embodiment, and 32 indicates a laser speckle for a connected L lead of a defective product before vibration in the second embodiment. In this state, all laser speckles are stationary, and the images are approximately the same for all leads. Next, if the component lead 8 is vibrated with the AC magnet 29, the good lead will not vibrate, but
The L lead that is connected to the defective product vibrates. In this state, a laser speckle image shown in FIG. 6 is obtained.
Defects are determined by comparing the laser speckles before and after vibration at locations corresponding to each lead.

Next, the defect determination method will be described. The laser speckle before excitation obtained by the storage type linear sensor 17 has almost the same shape for all the leads as shown in FIG. 9, but the laser speckle after excitation has the same shape as the first Like the embodiment, it has the shape shown in FIG. This difference is differentiated with respect to the location of the light intensity of the speckle image corresponding to each lead before and after the excitation, and the differential value is binarized with positive values as 1 and negative or 0 values as 0. The cross-correlation of the post-shake results is compared, and if the correlation coefficient is lower than a predetermined threshold value, it is determined to be a defect.

Modifications of the defect determination method include the following.

The ratio or difference between the average pitch of the maximum value of the speckle light amount before and after the vibration is calculated, and if this value is larger than a predetermined threshold value, it is determined to be a defect.

The ratio or difference between the maximum values of the amount of speckle light before and after the vibration is measured, and if this value is smaller than a predetermined threshold value, it is determined to be a defect.

The amount of speckle light before and after the vibration is subjected to fast Fourier transform, and the ratio or difference between the frequencies that take the maximum value in the frequency domain is calculated, and if this value is smaller than a predetermined threshold value, it is determined to be a defect.

The ratio or difference between the average value of the absolute value of the differential value of the speckle light amount before and after the vibration is calculated, and if this value is smaller than a predetermined threshold value, it is determined to be a defect.

According to this embodiment, the following effects can be obtained.

Stable non-contact vibration is possible because the vibration is performed using a magnet.

It is highly reliable because it compares the laser speckle before and after excitation.

Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 10 shows the configuration of an inspection apparatus for an inspection object similar to that of the first embodiment. The inspection device includes an excitation system 11 using an air nozzle 10 for simultaneously blowing a turbulent air jet with an oscillating flow rate onto a plurality of soldered parts to be inspected, and vibrates unconnected leads, and a soldered part. A laser irradiation optical system 15 consisting of a laser 12, an irradiation optical system 13, and a half mirror 14 for irradiating a laser beam to the target area, and a condenser with an image plane set at a focused position or a defocus position for detecting laser speckles. Optical system 16 and non-storage type parallel output linear sensor 33
a detection optical system 18, an X-Y table 19 for positioning the inspection object, a jet flow control unit 20 for controlling the flow rate of the air jet, a sensor drive circuit 11, a buffer 34 for storing parallel output signals, and a table. The control section 26 includes a controller 22, a laser control circuit 23, a defect determination section 24, and an overall control section 25.

The overall operation of the inspection will be outlined using FIG. 5. Prior to the inspection, the overall control unit 25
With this command, the X-Y table 19 is moved to the inspection start position and irradiation of the upper surface of the lead with the laser beam is started. Next, perform the inspection by repeating the following operations. Drive the X-Y table 19,
Position the leads for one side of the flat package part 7 to be inspected to the inspection position, and connect the air nozzle 1 to the inspection position.
Start spraying the air jet to the soldering part from 0.
In this state, the lead of the good product does not vibrate, but the connected L lead of the defective product vibrates. This state is observed by a non-storage type parallel output linear sensor 33, and the temporal fluctuation of the laser speckle shown in FIG. 11 is obtained. The time fluctuation of the laser speckle at the location corresponding to each lead obtained is buffered 34.
Defects are determined based on the accumulated time fluctuations.

The defect determination method is shown below. As shown in Figure 11a, the laser speckle obtained with a non-storage type parallel output linear sensor shows almost no change in the amount of detected light for a good product because the component lead is not vibrating, but for a defective product. For a connected L lead, the component lead vibrates at the natural frequency of the lead, so the amount of detected light oscillates as shown in FIG. 11b. Figures 12a and 12b are obtained by analyzing the temporal variation of this laser speckle with a spectrum analyzer. A lead whose peak frequency position in this frequency region is higher than a predetermined threshold as shown in FIG. 12b is determined to be defective.

A modification of this defect determination method is shown below.

Binarize the time fluctuation of speckle in floating form and set it to 0
The number that changes from 1 or 1 to 0 is calculated, and a lead whose value is larger than a predetermined threshold is determined to be defective.

In the same way, the floating type is binarized, the average value of the pitch changing from 0 to 1 or 1 to 0 is calculated, and a lead whose value is smaller than a predetermined threshold is determined to be defective.

Further, there are the following variations of the sensor used in this method.

A sensor capable of random scanning using image disector, etc. Using this sensor, each lead is sequentially scanned while detecting temporal fluctuations in the amount of incident light.

Point sensors such as Photomaru. Using this sensor, the X-Y table is driven one by one in a step-and-repeat manner for inspection.

This embodiment has the following effects.

Since the time variation of the laser speckle is measured, it is possible to know the vibration frequency of the lead, and the large amount of information provides high reliability, making it possible to make judgments that will not overlook any defects.

Since the vibration is performed using a turbulent air jet with a vibrating flow rate, even if the connected L lead hits the solder part and cannot vibrate at the natural frequency of the lead, it will vibrate at the frequency of the flow rate. This can be detected.

Next, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 13 shows the configuration of an inspection apparatus for an inspection object similar to that of the first embodiment.

The inspection device includes an excitation system 11 using an air nozzle 10 for blowing a turbulent air jet onto the inspection object;
and a laser irradiation optical system 15 consisting of a laser 12, an irradiation optical system 13, and a half mirror 14, a detection optical system 35 consisting of a condensing optical system 16 and an accumulation type two-dimensional sensor 35, an X-Y table 19, and jet flow control. unit 20, sensor drive circuit 11, buffer 34 for storing two-dimensional signals, and table controller 2.
2, a laser control circuit 23, a defect determination section 24, and a control section 26 consisting of an overall control section 25.

The overall operation of the inspection will be outlined using FIG. 5. Prior to the inspection, the overall control unit 25
With this command, the X-Y table 19 is moved to the inspection start position and irradiation of the upper surface of the lead with the laser beam is started. Next, perform the inspection by repeating the following operations. Drive the X-Y table 19,
Position the leads for one side of the flat package part 7 to be inspected to the inspection position, and connect the air nozzle 1 to the inspection position.
Start spraying the air jet to the soldering part from 0.
This state is observed by the accumulation type linear sensor 35, and a two-dimensional image of the laser speckle shown in FIG. 14 is obtained. The distribution of the laser speckle at the location corresponding to each lead in the two-dimensional position thus obtained is stored in the buffer 34, and defects are determined based on this stored temporal variation.

The defect determination method is shown below. The laser speckle obtained by the storage type two-dimensional sensor shows clear speckle spots as shown at 36 in Fig. 14 for good products because the component leads are not vibrating, but for defective products there is no connection L. Since the component lead vibrates with respect to the lead, a blurred speckle appears as shown at 37 in FIG. 14. This laser speckle is subjected to two-dimensional fast Fourier transform, and a defect is determined by comparing the peak position in the frequency domain with that of a good sample determined in advance.

A modification of this defect determination method is shown below.

The two-dimensional speckle image is binarized in floating form, the area of each bright region is calculated, and the average value is taken, and if these values are larger than a predetermined threshold value, it is determined to be a defective product.

The Laplacian operator is applied to the two-dimensional speckle image to detect the brightness peak position, the number of peaks per unit area is compared with a predetermined threshold value, and the smaller one is determined to be a defective product.

The fourth embodiment has the following effects.

Because it captures a two-dimensional image, it can obtain information over a wide area and is highly reliable.

Inspection is possible even when lead positioning accuracy is poor.

Since the vibration is performed using an air jet, it is possible to obtain vibration with a large amplitude as described in the first embodiment.

Further, although not explained in the above four embodiments, there is a method of vibrating the jet flow by vibrating the direction of the jet flow and exciting the jet flow by these vibrations in addition to the turbulent flow. In the nozzle 38 shown in FIG. 15, the control flows 40a and 40b are controlled in phase with respect to the main jet 39.
By flowing the main jet as an oscillating flow shifted by 180 degrees, the direction of the main jet can be oscillated up and down. This method has the same effect as an air jet with flow rate oscillation.

As described above, the embodiments of the apparatus of the present invention include implementations of various vibration methods, vibration detection methods, and defect determination methods, and these are summarized below.

(1) Vibration method Injection of air jets using only turbulence.

Injection of air jet with flow rate vibration.

Injection of air jet with oscillating jet direction.

(2) Vibration detection method How to detect time variations.

A method of detection using an accumulation-type linear sensor whose accumulation time is longer than the period of natural vibration of the lead being inspected.

A method of detection using an accumulation-type two-dimensional sensor whose accumulation time is longer than the period of natural vibration of the reed being inspected.

(3) Defect determination method A method that uses only the vibration state of the speckle during excitation.

A method that compares the vibration state of speckles before and after excitation.

Although only these typical combinations are shown as examples, any combination can be tested, and 18 different examples are possible.

Furthermore, as already mentioned, the test object shown in FIG. 1c, which has a connection structure similar to that of the soldered portion of a flat package type component, can be similarly tested.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to detect the quality of the joints of soldered parts of flat package parts of printed circuit boards and wire bonding parts of LSI etc. in a non-contact manner with high reliability and at high speed. This has the effect of automating these inspections, which previously relied on visual inspection.

[Brief explanation of drawings]

Figure 1 shows the inspection targets covered by this patent. Figure 1a is a soldering part of a flat package type component, Figure 1b is a wire bonding part of LSI etc., and Figure 1c is a general inspection target. Indicates the inspection target covered by this patent. Figure 2 is a detailed view of the soldered part of a flat package type component that is an example of the inspection target, Figure 3a shows a speckle image for a good lead, and Figure 3b shows a defective lead.
The speckle image for the lead is shown. FIG. 4 is a block diagram showing the first embodiment of the present invention, FIG. 5 is a diagram showing the inspection sequence of the first embodiment of the present invention, and FIG. 6 is a detection diagram of the first embodiment of the present invention. 7 is a block diagram showing the second embodiment of the present invention, FIG. 8 is a diagram showing the inspection sequence of the second embodiment of the present invention, and FIG. 9 is a diagram showing the inspection sequence of the second embodiment of the present invention. FIG. 10 is a configuration diagram showing the third embodiment of the present invention, and FIG. 11 is a diagram showing the detection speckle of the third embodiment of the present invention before vibration. FIG. 12 is a diagram showing the frequency response results obtained by analyzing FIG. 11 with a spectrum analyzer. FIG. 13 is a configuration diagram showing the fourth embodiment of the present invention. The figure shows a two-dimensional speckle image detected in the fourth embodiment of the present invention, and FIG. 15 shows the shape and cross section of a nozzle that can control the direction of the jet flow. 10... Air nozzle, 11... Vibration system, 12...
... Laser, 13 ... Irradiation optical system, 14 ... Half mirror, 15 ... Laser irradiation optical system, 16 ... Condensing optical system, 17 ... Non-accumulative linear sensor, 1
8...Detection optical system, 19...X-Y table, 2
0...Jet flow control section, 21...Sensor drive, 22...
... table controller, 23 ... laser control circuit, 24 ... defect control section, 25 ... overall control section,
26...Control unit, 29...AC magnet, 30...Magnetic field control unit, 33...Non-storage type parallel output linear sensor, 34...Buffer for accumulating detection signals, 3
5... Accumulation type two-dimensional sensor, 38... Nozzle,
39...Main jet flow, 40...Control flow.

Claims (1)

[Claims] 1. Vibrating the object in a non-contact manner, detecting the vibration state using optical means in a non-contact manner, and analyzing the detected vibration state to detect the bonding state of the object to be inspected. A bonding state detection method characterized by: 2. A vibration means for vibrating an object in a non-contact manner, an optical means for optically detecting the vibration state of the object excited by the vibration means, and an analysis of the vibration state detected by the optical means. What is claimed is: 1. A bonding state detection device comprising: analysis means for detecting a bonding state of an object. 3. The bonding state detection device according to claim 2, wherein the vibration excitation means is constituted by a gas injection stage that injects gas. 4. The bonding state detection device according to claim 2, characterized in that the vibration excitation means is constituted by excited magnetic force generation means. 5. Claim No. 5, characterized in that the above-mentioned optical means is constituted by a laser irradiation means for irradiating a laser beam onto the object, and a detection means for detecting fluctuations in the laser spectrum observed from the object. The bonding state detection device according to item 2, or 3, or 4.