JPS6085363A - Method and apparatus for detecting joint state - Google Patents

Abstract

PURPOSE:To enable a high-speed and highly reliable detection by a method where in after an object is vibrated in a non-contact manner, the vibration state is detected non-contact with an optical means and analyzed to detect the joint state of the object to be inspected. CONSTITUTION:A wire pattern on a substrate 1 is soldered with a part lead 8 provided on a component 7 such as LSI. An X-Y table 19 is moved to the position of starting inspection, then a laser beam is irradiated on the top of the lead to be inspected and an airstream is jetted to the soldered part from an air nozzle 10. The table 19 is driven to move one side of the lead to be inspected the part 7 to the inspection position. In the laser speckle obtained with a storage type linear sensor 17, an image sharply rugged with a fine pitch is observed as there is no vibration in the lead if it is accepted. But if it is rejected, an image gentle with a large pitch is observed as the lead vibrates causing a vibration in the speckle. This difference enables the discrimination on the quality.

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 the solder joint part 1 of a flat package type part (FIG. 1(a)) and the wire bonding part 2 of an LSI etc. (FIG. 1(+)).

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 automatically inspect, but also difficult to visually inspect, so inspection automation is particularly important. Highly necessary. All of these objects to be inspected have the same structure as shown in FIG.

Therefore, among these inspection targets, we are limited to inspecting flat package type parts for defects with no lead contact (including those that are completely floating and those that are in contact but are not soldered). explain. The same thing can be said about the inspection of other objects having the structure shown in FIG. 1(c), and it goes without saying that the inspection can be carried out using the method of the present invention.

As a conventional technique, the Vatt method described below is a method for visually inspecting parts of flat package parts.
There are two methods of elle lab.

The first method is to excite at a frequency of 60H2 to 200Hz by bringing the vibrator into contact with some part of the solder.
The state of vibration at that time is detected by a vibration detector, and defects are determined based on the state of vibration at that time (U,
S, Patent 4,218.922) The second method is to bring the vibrator into contact with several parts of the solder.
11z ~ I MHzt or 150AIIz ~ 650K
The frequency response of the solder parts is measured by changing the vibration using the IIzi and detecting the magnitude of the vibration with a vibration detector. Based on this frequency response, a defect detection sound is generated. Let's do it. (U, S, Paten
t 4,287,766) Since these methods perform vibration excitation and vibration detection using a contact method, they have the following drawbacks.

1) Inspection speed is slow.

2) It is difficult to maintain constant contact between the solder parts, the vibrator, and the detector, resulting in low inspection 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 an object in a non-contact manner using gas jets, magnetic force, etc., detects this vibration state in a non-contact manner using optical means, and detects the detected vibration state in a non-contact manner. This is a bonding state detection method characterized by analyzing 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 for vibrating an object in a non-contact manner or an excited magnetic force generating means, and a vibrating state of the object excited by the excitation means. The object of the present invention is to detect a bonding state of an object by comprising an optical means for optically detecting the vibration state, and an analysis means for analyzing the vibration state detected by the optical means. 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 entire principle of the present invention is shown below.

If the bonded states of the objects shown in FIG. 1 are different, the elastic properties of the bonded states will be different. Therefore, by vibrating the joint and detecting the vibration state at that time, abnormalities in the joint state can be detected.
In other words, it is possible to determine that the defect is 1'f3'fi.

For example, when soldering a flat package type component as shown in Figure 2, when the leads of a good product and a defective product are vibrated, the leads of the good product are firmly fixed to the board, so almost no vibration occurs.
- No vibration (eighth, the lead of a defective product is not connected to the board and vibrates violently. The magnitude of this vibration is measured, and those that are vibrating above a certain level are determined to be defective. be able to.

On the other hand, 1. Vibration detection is performed using the following method.

When an object to be inspected is irradiated with a laser and viewed with a sensor, high-contrast spots called laser speckles can be observed. Laser speckle is when a laser beam is irradiated onto the surface of an object, which has minute irregularities that can be considered as a sindamn diffraction grating, and is diffracted by this diffraction grating.
This is the result of mutual interference between the diffracted lights. Since these speckles move as the object moves, the movement of the object can be detected by observing the movement of the laser speckles 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 non-storage type sensor detects oscillating laser speckles, the position of the speckle spots will oscillate], my friend, the amount of detected light at a certain point will also oscillate and be observed as oscillating. For laser speckles that are not detected, the amount of detected light is observed to be constant. (Figure 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, it will be possible to detect a specific point. The amount of light is a constant value that does not depend on the location. For this reason, the distribution of detection signals for non-vibrating speckles is as shown in Figure 5 (a), where speckles with strong contrast are observed, and for vibrating speckles, as shown in Figure 6 (b).
), a blurred image with no contrast is observed and observed.Next, a first embodiment of the present invention will be specifically described with reference to the drawings. FIG. 2 shows an example of an object whose bonded state is to be detected. That is, the wiring pattern formed on the substrate 1,
A component lead 8 provided on a component 7 such as a T is bonded together.

FIG. 4 shows the configuration of an inspection apparatus for determining defects in the 17 lead connections for flat package components. The inspection device blows a turbulent air jet onto the soldering part of the counting point to be tested, and the excitation system 11 using an air nozzle 10 for adding unconnected leads to the soldering part. A laser irradiation optical system 15 consisting of a laser 12 for irradiating a laser beam, an irradiation optical system 13, and a half mirror 14, and an image plane were set at a focus position and a defocus position for detecting laser speckles. Concentrating optical system 16 and accumulation type linear sensor? 17, 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, and a defect determination section 24. It consists of 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, first, by command from the overall control section 25,
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 ejecting an air jet to the soldering part.

Next, perform the inspection by repeating the following operations. X-Y
Driving the table 19, the flat packaged part 7
Position the leads on one side of the inspection target to the inspection position.
, the laser beam is irradiated onto the top surface of the lead, and the air jet is directed to the soldering area. In this state, the good lead does not vibrate, but the defective lead does not vibrate.
It's vibrating. This state is observed by an accumulation type IJ near 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 laser speckles at locations corresponding to each lead.

Reference numeral 27 indicates laser speckle for a good product in the first embodiment, and 28 indicates laser speckle for 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 storage type linear sensor 17 has a thin pitch and a sharply uneven image is observed in the case of a good lead because the lead is not vibrating. However, the connection of the defective product [,
In the reed, the reed vibrates, the speckle vibrates, and this is detected in an integrated form, so a smooth image with a large pitch is observed. The number of locations where the speckle light intensity corresponding to each lead has a maximum value is measured, and a lead smaller than a predetermined threshold value is determined to be defective.

Variations of this judgment method include the following.

1) Calculate the half value of the pitch between the maximum values of the light intensity of the speckle image, and determine a lead for which this value is smaller than a predetermined threshold value to be defective.

11) Calculate the average value of the absolute values of the differential values of the light intensity of the speckle image, and determine a lead whose value is smaller than a predetermined threshold value as defective.

According to this example, the following effects can be achieved.Ol) Since the vibration is performed using an air jet that utilizes turbulence, the vibration is applied over a wide range of frequencies, including the natural frequency of the defective unconnected lead. It is possible to obtain vibrations with large amplitude.

il) Since an accumulation type sensor is used, it is possible to capture weak signals, and it is possible to obtain enough laser speckle to detect even a laser with a small output.

1ii) Since the determination method is simple, the speed can be increased and the W configuration is simple. Next, a second embodiment of the present invention will be described. The entire configuration of an inspection apparatus for inspection similar to that of the first embodiment is shown in FIG. An excitation system 11 using an AC magnet 29 to excite a component lead 8 made of a paramagnetic material such as iron;
Laser 12 for irradiating the laser beam onto several parts of the solder
a laser irradiation optical system 15 consisting of an irradiation optical system 13 and a half mirror 14; a detection optical system 18 consisting of a condensing optical system 16 for detecting laser speckles and an accumulation type IJ near sensor 17; and positioning X,
- Consists of a magnetic field control section 31 for controlling the Y table 19 and the AC magnet 29, a sensor drive circuit 21 for extracting sensor signals, a table controller 22, a laser control circuit 23, a defect determination section 24, and an overall control section 25. It consists of a control section 26.

The overall operation of the inspection will be outlined using FIG. 8. Prior to the inspection, by command from the overall control unit 25,
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. X-Y
Driving the table 19, the flat cage-shaped part 7
Position the leads on one side of the inspection target to the inspection position,
A laser speckle image shown in FIG. 9 is obtained. 61 is the second
62 shows the laser speckle for the non-defective product before vibration in the second embodiment, and 62 shows the laser speckle for the connected e-freed product before vibration in the second embodiment. In this state, the laser speckles are all stationary and appear, and the images are almost the same for all leads. Next, when the component lead 8 is vibrated with the AC magnet 29, the good lead does not vibrate, but the defective lead does not vibrate.
vibrates.

In this state, a laser speckle image shown in FIG. 6 is obtained. Defects are determined by comparing laser speckles before and after excitation at locations corresponding to each lead.

Next, the defect determination method will be described. Accumulation type 1 nonia sensor 1
The laser speckles obtained in step 7 before excitation have almost the same shape for all leads as shown in Fig. 9, but the laser speckles after excitation are similar to those in the first example. The shape is similar to that shown in FIG. This difference is differentiated with respect to the location of the light intensity of the corresponding speckle image for each lead before and after excitation, and all cases where this differential value is positive are 1. Binaryize with negative or O values as the starting point, and compare by taking the mutual correlation of -1 before and after vibration, and if the correlation value is lower than a predetermined threshold, it is determined to be a defect. do.

Variations of the defect determination method include the following: 1) Calculate the ratio or difference between the average pitches of the maximum values of speckle light -ml: before and after vibration, and determine if this value is greater than a predetermined threshold. Determine something as defective.

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

1ii) Fast Fourier transform the amount of speckle light before and after excitation, calculate the specific gravity or difference of the frequency that takes the maximum value in the frequency domain, and if this value is predetermined, 17') is smaller than the threshold value. Determined as all defects.

N) Calculate the difference between the average absolute value of the differential value of the speckle element order before and after the vibration, and if this value is smaller than a predetermined threshold, it is determined to be a defect.

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

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

ii) High reliability as laser speckles are compared before and after excitation.

Next, a fifth 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 has an air nozzle 10 that can simultaneously blow a turbulent air jet with an oscillating flow rate onto multiple soldering parts to be inspected, and vibrate leads without plugs.
Laser irradiation using the excitation system 11, the laser 12 for irradiating the soldering part with a laser beam, the irradiation optical system 13, and the half mirror 14 -) LR system 15, and laser speckle detection The condensing optical system 16 sets the iτ plane at the focal point position or defocus position of the lens.
and a detection optical system 18 consisting of a non-storage type parallel output linear sensor 66, and an X-
A Y table 19, a jet flow control section 2o that controls the flow rate of the air jet, a sensor drive circuit-1, a buffer 34 for storing parallel output signals, a table controller 22, a laser control circuit 23, a defect determination section 24, and an overall control section. The control section 26 includes a control section 25.

The overall operation of the inspection will be outlined using FIG. 5. Prior to the inspection, first, by command from the overall control section 25,
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, the following operation 'fc b' is repeated and inspected. The X-Y table 19 is driven to position one side of the leads to be inspected of the flat package component 7 to the inspection position, and the air nozzle 10 starts spraying an air jet to the soldering part.

In this state, either a good reed does not vibrate, or a defective L'J-de vibrates. This state'(r
Observation is made with a non-storage type parallel output linear sensor 33 to obtain the laser speckle time z=h shown in FIG. The laser speckle times corresponding to the respective leads thus obtained are accumulated in the buffer 34, and defects are determined based on the accumulated times.

The defect determination method is shown below. Non-storage type parallel output linear
The laser speckle obtained by the sensor is 1 for a good product.
Because the component leads vibrate, W, 11)”A
As shown in (ζL), the amount of detected light hardly changes, but due to the connection of a defective product [11th j
The amount of detected light oscillates as shown in (b). This I
Figures 12(a) and 12(b) are obtained by analyzing the temporal variation of I-the speckle using a spectrum analyzer. The position of the single frequency in this frequency region is
As shown in FIG. 12(b), a lead higher than a predetermined threshold value is determined to be defective.

A modification of this defect determination method is shown below.

i) Binarize the time variation of speckle in full floating form from 0 to 1
Alternatively, a number that changes from 1 to 0 is calculated, and a lead whose value exceeds a predetermined threshold is determined to be defective.

ii) Similar to i), the floating type is binarized, and the average value of the pinches changing from 0 to 11 or from 1 to 0 is calculated, and a lead whose value is smaller than a predetermined threshold is determined to be defective.

In addition, the following gun is a variation of the sensor used in this method.

i) A sensor capable of random scanning using an image dissector or the like. Using this sensor, each lead is sequentially scanned while detecting temporal fluctuations in the amount of incident light.

it) Point sensor such as Photomaru 0 This sensor is used to drive the X-Y table one by one in a step-and-rebeat manner to perform inspection.

This embodiment has the following effects.

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

i) Since the vibration is performed using a turbulent air jet with a vibrating flow rate, even if the connecting L IJ-de hits one solder part and cannot vibrate at the natural frequency of the lead, it will vibrate at the frequency of the flow rate. This vibration 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 12.
, a laser irradiation optical system 15 consisting of an irradiation optical system 16 and a half mirror 14 , and a detection optical system 35 consisting of a condensing optical system 16 and an accumulation type two-dimensional sensor 55 . X-Y table 19
．． The control section 26 includes a jet flow control section 20, a sensor drive circuit 11, a nozzle 34 for storing two-dimensional signals, a table controller 22, a laser control circuit 26, 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, by command from the overall control unit 25,
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, the inspection is carried out by repeating the following operations: 1X-Y table 19 is driven to position one side of the flat package component 7 to be inspected to the inspection position, and the air nozzle 10 Start spraying the air jet onto some parts of the solder. This state is observed by the storage type linear sensor 65, and the 14th
Obtain the two-dimensional image of laser speckles shown in the figure.The distribution of laser speckles at the locations corresponding to each lead in the two-dimensional positions thus obtained is accumulated in the buffer 64, and the accumulated time Defects are determined based on fluctuations.

The defect determination method is shown below. The laser speckles obtained with the storage type two-dimensional sensor show clear speckle spots as shown at 66 in Figure 14 for good products because the component leads are not vibrating, but the connection of defective products is For the L IJ-do, the component leads are vibrating, resulting in blurred speckles as shown at 37 in Figure 14. This laser speckle is subjected to a two-dimensional fast Fourier transform, and is converted into a frequency domain. Defectiveness is determined by comparing the peak position of the sample with that of a sample of non-defective products determined in advance.

A modification of this defect determination method is shown below.

l) Binarize the two-dimensional speckle image in floating form, calculate the area of each bright region, take the average value, and determine that all products that are thicker than a predetermined threshold are defective.

ii) A 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.

j) Since it captures a two-dimensional image, it can obtain information from a wide area and is highly reliable.

ii)! Inspection is possible even if the positioning accuracy of the J-board is poor.

1ii) 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-mentioned four embodiments, there is a method of vibrating the jet flow by vibrating the direction of the jet flow and vibrating it by these vibrations in addition to the turbulent flow. In the nozzle 3B shown in FIG. 15, the control flow 40a is
By flowing the main jet and 40b as an oscillating flow with a phase shift of 1800, the direction of the main jet can be oscillated up and down. This method has the same effect as an air jet with oscillated flow rate.

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

(1) Vibration method i) Air jet spraying using only turbulence.

ll　Air stream injection with flow rate imaging.

1ii) Injection of air jet with oscillating jet direction.

(2) Imaging detection method i) A method for detecting time variations.

1) Detection method using an accumulation-type linear sensor whose accumulation time is longer than the period of natural vibration of the reed to be inspected.

111) A method in which the accumulation time is longer than the period of the natural vibration of the reed to be inspected using an i-long accumulation type two-dimensional sensor.

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

ii) 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, it is possible for as many as 10 colleagues to inspect the inspection object shown in FIG.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to detect the quality of the bonding conditions of soldered parts of flat package parts of printed circuit boards and wire bonding locations of LSIs, etc., in a non-contact manner, with high reliability, and at high speed. , - It is possible to fully automate these inspections that previously relied on visual inspection.

[Brief explanation of drawings]

Figure 1 shows the parts to be inspected that are the subject of this patent. Figure 1 (a) shows the soldering part of flat pan gauge type parts, and Figure 11 (b) shows the wire bonding part of LSI etc. Figure 1 ('c) shows a general inspection target covered by this patent. Figure 2 is a detailed view of the soldered part of a flat package component that is an example of the inspection target, Figure 3 (a) shows a speckle image for a good lead, and Figure 6 (a) shows a speckle image of a good lead.
Figure (b) shows a speckle image for a defective connected LIJ-de. 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. A diagram showing a speckle image, FIG. 7 is a configuration diagram showing a second embodiment of the present invention, FIG. 8 is a diagram showing an inspection sequence of the second embodiment of the present invention, and FIG. A diagram showing detected speckles before excitation in the second embodiment, FIG. 10 is a configuration diagram showing the third embodiment of the present invention, and FIG. 11 shows non-defective and defective products in the third embodiment of the present invention. 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. , FIG. 14 is a diagram showing a two-dimensional speckle image detected in the fourth embodiment of the present invention,
FIG. 15 is a diagram showing the shape and cross section of a nozzle that can control the direction of jet flow. 10...Air nozzle, 11...Excitation system 12...V-za 13...Irradiation optical system 14...Half mirror 15...Laser irradiation optical system 16.
...Condensing optical system 17...Non-accumulative linear sensor 18...Detection optical system 19...X-Y table 20
...Jet flow control section 2 sensor drive 22...Table controller 23...Laser control circuit 24..Defect control section 25.
- Overall control unit 26... Control unit 29... AC magnet 6o - Magnetic field control unit 33 - Non-storage type parallel output linear sensor 34 - Buffer 35 with all detection signals connected... Storage type two Dimensional sensor 38 Nozzle 69-・Main jet flow 40・Control flow FIG. Figure 11 (δn; 1゛ Figure 14 - Figure 15)

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 determine the bonding state of the object to be inspected. A bonding state detection method characterized by detecting. 2. A vibration excitation 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 optical means for optically detecting the vibration state of the object excited by the vibration means. What is claimed is: 1. A bonding state detection device comprising: analysis means for analyzing, and detecting a bonding state of an object. 2. The bonding state detection device according to claim 2, wherein said vibration excitation means is constituted by a gas injection stage for injecting 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 2, characterized in that the optical means is constituted by laser irradiation means for irradiating a laser beam onto the object, and detection means for detecting fluctuations in the laser spectrum observed from the object. The bonding state detection device according to item 6, item 6, or item 4.