JPS61240105A - Method and apparatus for detecting connection state - Google Patents

Abstract

PURPOSE:To enable the detection of a connection state at a high speed with good reliability, by detecting the change with time in the vibration, movement or deformation of an object in a non-contact state by using an optical means and analyzing the detected change with time to detect the connection state of the object. CONSTITUTION:The detected wave form of each speckle at the detection time (t) of a sensor is set to ft(x) (wherein x shows the position corresponding to each picture element of a linear sensor) and the judgement of a flaw in performed on the basis of the laser speckles at the positions corresponding to parts leads 27, 28, 29 is said detected wave forms. That is, with respect to the parts lead 27 not connected and the parts lead 28 weak in connection, the speckle wave forms come to a shape having no unevenness by the self- exciting vibration of the parts leads 27, 28 or change appears in said wave forms. In this case, by taking the correlation phi1, t0+1 (xb>=x>=xe) of two speckle wave forms, the one wherein a correlation value is smaller than a predetermined threshold value phi+h is judged as a flaw. By this method, a connection state can be detected at a high speed in a non-contact state.

Description

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

[Background of the invention]

The joints to be inspected include soldering parts 1 of flat package type parts (Fig. 1 (a)), wires of LSI etc.
Examples include bonding location 2 (FIG. 1(b)).

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. As shown in FIG. 1(c), these objects to be inspected all have the same structure consisting of a first object 3, a second object 4, and a joint 5 between them. Therefore, the following will explain only the inspection of flat package type parts with no lead connection defects (including those that are completely floating and those that are in contact but are not soldered). . The same thing can be said about the inspection of other objects having the structure shown in FIG.

As a conventional technique, the following V at
There are two methods used by Telle Lab.

The first method is to excite the vibrator at a frequency of 60Hz to 200KHz by bringing the vibrator into contact with the solder.The vibration state at that time is detected by a vibration detector, and the vibration state at this time is also measured. Defects are determined. (U,
S., Patent 4,218,922) The second method is to bring the vibrator into contact with the solder metal.
The frequency response of the solder is measured by changing the frequency from 0Hz to IMHz or from 150KHz to 650KHz, and measuring the frequency response of the solder by using a vibration detector to detect the magnitude of the vibration at this time. Defects are determined.

(U,S-Patent 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 a constant state of contact between the solder cap, the vibrator, and the 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-mentioned objective, the present invention applies an external force to an object without contact using gas jets, magnetic force, etc.

The feature is that the time change of the object such as vibration, movement, deformation, etc. at this time is detected in a non-contact manner using optical means, and the detected time change is analyzed to detect the bonding state of the object to be inspected. It is something to do. The present invention also relates to an apparatus that directly uses the above method, and includes a mechanical means comprising a gas injection means or an excited magnetic force generating means for applying an external force to an object in a non-contact manner; an optical means for optically detecting temporal variations in changes in an object that has undergone changes such as vibration, movement, deformation, etc.; and an analysis means for analyzing temporal fluctuations in changes occurring in the object detected by the optical means. The device is characterized in that it is configured to detect the bonding state of the objects. Note that the above-mentioned optical means includes, for example, an irradiation means for irradiating a laser and a detection means for detecting fluctuations in laser speckles observed from an object. Further, the detection of changes in the object over time is performed by the following method. That is, when an object to be inspected is irradiated with a laser and viewed with a sensor, high-contrast spots called laser speckles are observed. Laser speckle is when 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 single diffraction beams interfere with each other. . 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 vibrating laser speckles, the position of the speckle salt is vibrating, so
The amount of detected light at a certain point is also observed to oscillate, and for laser speckles that do not oscillate, 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 salt is vibrating, so if the accumulation time is longer than the vibration period, a specific point can be detected. The amount of light is a constant value that does not depend on the situation. Therefore, in the distribution of detection signals for non-vibrating speckles, speckles with strong contrast are observed as shown in FIG. 3(a).

For vibrating speckles, a blurred image with no contrast is observed, as shown in FIG. 3(b).

Also, when detecting vibrating speckles, if the accumulation time is made sufficiently smaller than the vibration period.

A waveform similar to that of a non-storage type sensor is detected. As for speckles that move, if the movement is sufficiently fast compared to the accumulation time, speckles with no contrast will be detected, and if the movement is sufficiently slow compared to the accumulation time, speckles that are gradually moving will be detected.

[Embodiments of the invention]

1 to 11 showing embodiments of the present invention will be specifically described below. First, before describing embodiments of the present invention, the principle of the present invention will be described below. As shown in FIG. 1, the solder joint between the wiring pattern 9 on the board 6 mounted on the x-y table 19 and the component lead 8 provided on the flat package type component 7 such as LSI is the If the conditions are different, the elastic properties of the component leads 8 will differ depending on the bonding condition. Therefore, for example, at the joint between the wiring pattern 9 and the one-component lead 8,
The above bonded state can be determined by ejecting turbulent air from a dynamic system 11 using an air nozzle 10 and applying an external force, and detecting time fluctuations in changes such as vibration, movement, and deformation occurring in the component lead 8. It becomes possible to determine abnormalities, that is, defects. That is, for example, the nozzle 10 shown in FIG. 1 is applied to a non-defective product and a defective product at the soldered portion of the component lead 8 of the flat package type component 7 shown in FIG.
When external force is applied by ejecting turbulent air from the dynamic system 11 using However, the defective component lead 8 is not bonded to the wiring pattern 9 of the board, or the bonding force is weak due to insufficient bonding, so it is susceptible to minute vibrations due to vibration, movement, and elastic deformation of the bonded part. Occur. We measure the fluctuations of these minute vibrations over time,
A change that differs from that of a non-defective product, such as a change that starts early or changes rapidly, can be determined as a defect.

[Example I]

Next, FIGS. 1 and 5 will explain the first embodiment of the present invention.
This will be explained with reference to FIGS. 9 to 9. FIG. 5 is a perspective view showing an example of a target object of the present invention. As shown in the figure, the bonding surfaces between the wiring pattern 9 formed on the substrate 6 and the component leads 8 provided on the flat package type component 7 such as LSI are soldered. Further, FIG. 1 is an explanatory view showing an inspection device for determining defects in the soldered portion of the component lead of the flat package type component shown in FIG. 5 above. In the figure, as described above, the dynamic means 11 using the air nozzle 10 is used to blow out turbulent air onto the soldered portion of the component lead 8 to apply an external force to the component lead 8. Further, a laser transmitter 12 for irradiating the soldered portion of the component lead 8 with a laser beam, and an irradiation optical system 1 are provided.
3, and a laser irradiation optical system 1 consisting of a half mirror 14
5, a condensing optical system 16 with an image plane set at a focused position, a defocused position, or a defocused position in only one direction for detecting laser speckles, and a detection optical system 16 consisting of an accumulation type near sensor 7. system 18, a detection optical system 18 for positioning the inspection object, and an X for positioning the flat packaged part 7 to be inspected.
- A jet flow control section 2o for controlling the air jet amount of the Y table 19 and the dynamic means 11, and a sensor drive circuit 2
1, table controller 22, and laser control circuit 2
3, a defect determination section 24, and an overall control section 25. Since the configuration is as described above, the entire operation will be explained with reference to FIG. 6 showing the inspection sequence. Prior to the inspection, the X-Y table 19 is first moved to the inspection start position according to a command from the overall control section 25, and the laser beam starts to be irradiated onto the upper surface of the component lead 8 to be inspected.

Next, the following operations are repeated to perform the inspection.

That is, the X-Y table 19 is driven to position one side of the component lead 8 to be inspected of the flat packaged component 7 at an inspection position, and the upper surface of the component lead 8 is irradiated with a laser beam. In this state, the linear sensor 7 starts detecting temporal fluctuations in speckles. Afterwards,
t while the jet flow control unit 2o starts detection by the linear sensor 17.

When the time has elapsed, air is ejected from the air nozzle 1o toward the solder joint of the component lead 8, and when time t1 has elapsed, the air nozzle 1o is controlled to stop ejecting air. . At this time, the time variation of detected speckles will be explained with reference to FIGS. 7 and 8. First, let's talk about the case of a non-defective product. In this case, the component lead 8 is firmly fixed to the board 6, so
When the substrate 6 starts to vibrate due to the outward jet of air from the air nozzle 10, the component leads 8 also start to vibrate. In this case, as shown in FIG. 7(c), even if air is ejected from the air nozzle 10, the component lead 8
Due to the total rigidity of the substrate 6 and the substrate 6, no fluctuation in the waveform is observed. On the other hand, if the component lead 8 and the board 6 are not connected, the air nozzle
Air blows out and applies an external force to the component lead 8, and at the same time the component lead 8 moves and generates self-excited vibration at the moving position. The self-excited vibration at this time generates vibration at a high frequency of several kHz to several 10 kHz, which is the natural frequency of the component lead 8, and with a large amplitude. In addition, if the soldering between the component lead 8 and the board 6 is insufficient, that is, the connection between the two is weak, the component lead 8 is connected to the air nozzle 1 as shown in FIG. 7(b).
When an external force is applied due to air jetting from the base plate 0, minute rotational vibrations are generated around the joints, and then when the board 6 starts vibrating, the vibrations of the board 6 and the parts mentioned above are generated. Vibration is generated in the component lead 8 in combination with minute rotational vibrations generated in the lead 8 itself. In this case, when an external force is applied, the component lead 8 vibrates with a small amplitude at a natural frequency, and the board 6 vibrates with a medium amplitude at a low frequency of about several tens of Hz to several hundred Hz. Furthermore, even when the component lead 8 and the board 6 are not connected as described above, the component lead 8 is pressed against the board 6. In some cases, the component lead 8 comes into contact with the board 6 and the vibration temporarily stops. Next, the sensor detection time is set to a time greater than the natural frequency of the component lead 8 and smaller than the natural frequency of the board 6, for example, the sensor detection time t is set to time 19, time 2, and so on. ...If the time is 8 and the time tI from the start of the sensor to the start of air blowing is the time 3, the detection time of each sensor is the unconnected component lead 2.
7. Weakly connected component leads 28, Good component leads 29
The speckle waveform of is detected as shown in FIG. That is, as shown in the figure, the sensor detection time t is time 19.
At time 2, the speckle waveform of each component lead 27, 28, and 29 has not yet started to emit air, so there is almost no time variation in the speckle waveform, but when the sensor detection time t coincides with the air ejection start time t0, it is a good product. There is almost no change in the component lead 29, but the unconnected component lead 27 causes speckle movement, and the self-excited vibration of the component lead 27 itself generates a speckle waveform with no unevenness at the moving position. There is. In addition, the weakly connected component lead 28 causes speckle movement, and the self-excited vibration of the component lead 28 itself generates a speckle waveform with no unevenness at the moved position. Therefore, the speckle detection waveform at sensor detection time t is set as ft(, e) (χ represents the position corresponding to each pixel of the linear sensor), and each component lead 27, 28, 29 in these detection waveforms is Defects are determined based on the state of the laser speckle at the corresponding position 8, that is,
From the design information, the X corresponding to each pixel of the linear sensor is
Assuming that the position XbeXe of each component lead 27, 28, 29 is in the range xb≦X<X, the detected waveform ft(χ) at time t uses ft(χ): xb≦X≦Xe. Next, one method of defect determination will be described with reference to FIG. Figure (a) shows the speckle waveform of each component lead before air is blown out. As shown in the figure, in this case,
The speckle waveforms of each component lead 27, 28, and 29 are approximately the same. Next, the same figure (b) shows the speckle waveform of each component lead after air is blown out, as shown in the same figure.

In this case, the non-defective component lead 29 maintains the state before the air is ejected and no change is observed.On the other hand, the component lead 27 with no connection and the component lead 28 with a weak connection
In this case, the speckle waveform becomes smooth due to the self-excited vibration of the component leads 27 and 28, or the waveform changes. Is this change in speckle waveform a cross-correlation between two speckle waveforms? ,.

By taking toot (Xb≧X≧Xa), those whose correlation value is smaller than a predetermined threshold P+h are determined to be defects. That is, the above cross-correlation P xm t
oot(xb≧X≧xe) as χ.

Then, Pzto+, ≦P+h is considered a defect.

F　toot＞　P　+h is determined as a good product.

In addition to the above-mentioned means for applying an external force, there is a means for applying an external force in a stepwise manner using a magnet. In addition to the defect determination method described above, there is a method described below.

(i) In other words, the sum of the absolute values of the differences between the speckle waveform f1(χ) before air is ejected and the speckle waveform fto+□(χ) immediately after air is ejected x1゜to+1
(xb≦X≧xe), and if this value is larger than a preset threshold value X+h, it is determined as a defect.

That is, the sum of absolute values x1゜toot(Xb≧X≦xe
), then X□toot≧X+h is a defect, and xtI
, +, ≧X+h is determined to be a good product.

(ii) The speckle waveform is applied with a high-frequency emphasis filter or a bandpass filter (g c Cx)
Defects are determined by comparing the cross-correlation or the sum of the absolute values of the differences.

(fit) A speckle waveform is Fourier-transformed, and a phase difference or a rate of change corresponding to a specific frequency in the Fourier-transformed region is determined as a defect if it is larger than a preset threshold.

Therefore, according to the embodiment described above, since an external force is applied to the component leads 27, 28, 29 by the air jet, the defective product vibrates with a large amplitude at its natural frequency or moves. There is a big difference between good quality products. Moreover, since it is possible to determine whether a defective product is a good product or a defective product simply by comparing the speckle waveforms before and after the air is blown out, it is possible to increase the speed.

[Example ■]

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 10 is an explanatory diagram of the configuration of an inspection apparatus showing another embodiment of the present invention. As shown in the figure, an AC magnet 3 is used to vibrate a component lead 8 made of a paramagnetic material such as iron.
0, a laser transmitter 12 for irradiating a laser beam onto the solder portion of the component lead 8, a laser irradiation optical system 15 consisting of an illumination optical system 13 and a half mirror 14, and a laser spec. A detection optical system 18 formed from a condensing optical system 16 for detecting a linear sensor and an accumulation type linear sensor 17, and a positioning X-Y
A magnetic field control section 31 for controlling the table 19 and the AC magnet 30, a sensor drive circuit 21 for taking out sensor signals, and a table controller 22 for controlling the positioning XY table 19.

It is comprised of a laser control circuit 23 for controlling the output amount of laser light from the laser oscillator 12, a control section 26 formed from a missing defect determination section 24 and an overall control section 25. Since the configuration is as described above, its operation will be described based on the inspection sequence shown in FIG. As shown in the figure, prior to the inspection, the X-Y table 19 is first moved to the inspection start position by a command from the overall control unit 25 and positioned so that the laser beam will irradiate the solder portion of the component lead 8. Thereafter, irradiation of the laser beam onto the solder portion of the component lead 8 is started. Next, the inspection is performed by repeating the operations described below. That is, the X-ZY table 19 is driven to position the component lead 8 on one side of the flat package component 7 to be inspected at the inspection position, and the linear sensor 7 detects speckles. Start detecting time fluctuations in . When 70 hours have passed since the start of detection,
When the AC magnet 30 is excited and t time has elapsed,
The magnetic field control section 31 is driven so that the excitation is completed. In this case, the time fluctuation of the component lead 8 was a self-excited vibration in the previous example (2), but in this example, it was a forced vibration.
The only difference is this point, and the rest are the same. Furthermore, if the accumulation time of the accumulation type linear sensor 17 is set to be larger than the excitation frequency of the component lead 8 and smaller than the natural frequency of the board, the speckle waveform of the component lead 8 will be the same as that of the above embodiment. It is detected in the same manner as in FIG. 8 described above. Next, the missing defect determination method will be described. In general, speckles from the board are dark, and speckles from the component leads 8 and wiring pattern 9 are bright. Therefore, the dark part of the speckle is masked as a part of the board and speckles from the component lead 8 and wiring pattern 9 are bright. Extract only files. x1≦x<X4+z of extracted waveform: X4=i×Δ
Defects are determined for speckle waveforms within the range of χ. The above judgment cylinder 11 (x4≦X<X + +t
) Regarding the change in the speckle ε waveform at the accumulation time t of the accumulation type linear sensor 7 before and after the AC magnet 30 is excited, the mutual a correlation between the two speckle waveforms P t (4v x +≦X≦
Xi+i) is half, the amount of change at of the two speckle waveforms is aj=mQx [j'
t C<JpxsSx≦x++z)], so,
Assuming that the shift amount at which the change amount at of the two speckle waveforms is the maximum value is sl, for a good component lead 8, the change amount at and the shift amount st are determined by the vibration of the board. Therefore, from the detected speckle waveform, the pattern of the change amount at and shift amount Sj of the good component lead 8 is extracted, and the above-mentioned AC magnet 30 is used as an i method that is significantly different from the shift amount ( Alternatively, there is a method of vibrating the flow rate or the direction of the jet stream to create the air jet 1, or of vibrating it with ultrasonic waves.Also, as other conventional methods, the following method is available.

i) In other words, apply a high-frequency emphasis filter or a bandpass filter to the detected speckle waveform ft(χ) to obtain a waveform gt(χ) that emphasizes unevenness, and then calculate the sum of the absolute values. Assuming that the time variation ht of the blur amount of the speckle waveform is )C: Similarly, after extracting non-defective component leads 8, those that are significantly different from these are determined to be defective.

ii) Fourier transform the detected speckle waveform ft(χ), extract the component lead 8 of phase and absolute value at a specific frequency, and determine a component lead 8 that is significantly different from this as a defect.

Therefore, according to the embodiment described above, since the magnet or the like is used for forced vibration, stable vibration can be obtained. In addition, defects are determined after detecting the vibration of the board and removing it.

Test reliability is high.

As described above, the dynamical system 11 when implementing the present invention
Examples include air jets (using turbulence), and magnets.

There are AC magnets, air jets that vibrate the flow rate or jet direction, and ultrasonic waves.Methods for dividing the judgment area include:
There is a method that uses design information and the bright part of speckles.Furthermore, as a judgment method, the blowing of the air jet is determined by cross-correlation or the difference between the waveforms before and after, and after filtering the detected waveform, the blowing of the air jet is For cross-correlation or waveform difference, or air jet blowing, the front and rear waveforms are Fourier-transformed, and the phase difference and change rate of 1 specific frequency are used, or 1=0 and t=t4 (4=1...
In the case of 2...), the time variation of the shift amount deformation amount is determined from the cross-correlation, and from this, the patterns of non-defective products are extracted and those that are significantly different are considered defects, or the detected waveform is filtered and its absolute value is determined. By taking the sum of , the time variation of the amount of speckle blur is determined.

By doing this, you can either extract the patterns of good products and treat those that are significantly different as defects, or perform Fourier transform on the detected waveform.
It is possible to obtain the temporal fluctuations of the phase and absolute value of a specific frequency, extract the patterns of good products, and consider those that are significantly different from each other as defects, and by combining these methods. Furthermore, as described above, the inspection target shown in FIG. 1(c), which has a joint structure similar to that of the soldered portion of a flat package type component, can be similarly inspected.

〔Effect of the invention〕

As described above, the present invention is applicable to soldering parts of flat package parts of printed circuit boards and wires such as LSIs.
Since it is possible to detect the quality of bonding points, etc., in a non-contact manner, with high reliability and at high speed, it is possible to automate these inspections, which were previously performed by visual inspection, thereby further increasing reliability. It has high sensitivity and can be detected at high speed.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a bonding state inspection device showing an embodiment of the present invention, FIG. 2(a) is a soldered part of a flat package component to be inspected, and FIG. 2(b) is a wire of an LSI etc.・Bonding location, Figure 2 (C) is a perspective view of each inspection target covered by this patent, Figure 3 (
a) is a good parts lead. (b) is a temporal variation curve of each speckle light intensity of a defective component lead, Figure 4 (a) is a diagram of a non-defective component lead, (b)
) is an image of each speckle on the defective component lead. Figure 5 is an enlarged perspective view of the soldered part of the flat package part to be inspected, Figure 6 is an inspection sequence showing an example of the inspection method of Figure 1, and Figure 7 (a) is a component lead with no connection. , (b) is a component lead with a weak connection, (C) is a temporal variation curve of the lead position when applying each external force for a good component lead, and Figure 8 is a component lead with no connection and a component with a weak connection. Figure 9 (a) shows the waveform of the speckle light intensity before air blowing, and (b) shows the waveform of the speckle light intensity immediately after air blowing. , FIG. 10 is an explanatory diagram of a bonding state inspection apparatus showing another embodiment of the present invention, and FIG. 11 is an inspection sequence showing another embodiment of the inspection method of FIG. 10. 1... Soldering part of flat package type parts, 2...
・Wire bonding points for LSI etc., 3...
First object, 4... Second object, 5... Joint, 6
... Board, 7... Parts, 8, 27.28.29.
... Parts lead, 9 ... Wiring pattern, 10 ... Air nozzle, 11 ... Mechanical means, 12 ... Laser transmitter, 13 ... Irradiation optical system, 14 ... Half mirror 1
15... Laser irradiation optical system, 16... Condensing optical system,
17... Storage type linear sensor, 18... Detection optical system, 19... x-y table, 20...
...Jet flow control section, 21...Sensor drive circuit, 22...
・Table controller, 23...laser control circuit,
24... Defect determination section, 25... Overall control section, 26.
...Control unit, 30...AC magnet, 31...Magnetic field control unit.

Claims (1)

[Claims] 1. Applying an external force to the object, detecting time changes such as vibration, movement, deformation, etc. of the object that occur at this time using optical means without contact, and analyzing the detected time changes. A method for detecting a bonded state, comprising: detecting a bonded state of an object to be inspected. 2. Bonding state detection characterized in that the analysis of the detected temporal change as set forth in claim 1 is performed by focusing on changes in the shift amount, deformation amount, etc. of the speckle waveform before and after applying external force. Method. 3. The analysis of the detected temporal change described in claim 1 focuses on temporal changes in the shift amount, deformation amount, etc. of the speckle waveform when an external force is applied, and detects the quality of the good product from the speckle waveform. A bonding state detection method characterized by extracting a pattern and treating a pattern with a different speckle waveform as a defect. 4. The analysis of the detected temporal change described in claim 1, 2, or 3 is performed by correlating, Fourier transform, or simple A bonding state detection method characterized by determining based on a difference. 5. Mechanical means that applies an external force to an object, optical means that non-contact detects temporal changes such as vibration, movement, deformation, etc. generated by this mechanical means, and analysis that analyzes temporal changes detected by this optical means. What is claimed is: 1. A bonding state detection device comprising means for detecting a bonding state of objects in a non-contact manner. 6. The optical means recited in claim 5 includes a laser irradiation means for irradiating a laser beam onto an object, and a time fluctuation of a laser speckle waveform observed from the object at an imaging position, a defocus position, or a single point. 1. A bonding state detection device comprising a detection means that detects at a position that is defocused only in a direction.