JPS6165175A - Method and apparatus for inspecting joined status of terminals of circuit parts - Google Patents

Abstract

PURPOSE:To detect oscillation with high sensitivity and to attain highly accurately an inspection for a joined state by inserting an optical means such as a cylindrical lens having a negative focal distance into an optical detecting system and defocusing light only in one direction. CONSTITUTION:One lead to be tested of a flat package type parts 7 is positioned on an inspecting position, a laser beam is irradiated to the upper surface of the lead and disturbed air jet is blown from an air nozzle 15 upon a soldering part to be inspected. Under said status, a lead of high quality is not oscillated, but a defective disconnected lead is oscillated. Therefore, light is defocused only in one direction by the cylindrical lens 21-2 having a negative focal distance and the lead is observed by an accumulation type linear sensor 22 having a sample rate larger than its oscillation frequency to obtain a laser speckle. An excellent laser speckle has a sharp unevenness in fine pitches, but a defective one disconnected with lead has a moderate waveform. Consequently, the defect of the joint part can be decided by analyzing the difference of the laser speckle.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method and apparatus for inspecting the bonding condition of circuit components such as integrated circuits, and more specifically to a method for inspecting the bonding condition of circuit components in a non-contact manner. The present invention relates to a method and apparatus for shaking and detecting the vibration state in a non-contact manner.

[Background of the invention]

The joints of circuit components such as integrated circuits to be inspected include solder parts 1 of flat package components as shown in Fig. 1(a), and wires of LSI etc. as shown in Fig. 1(b).・There is a pounding point 2, etc.

These defects in objects having joints include those in which the joints are completely separated, those in which the joints are only in contact but not completely connected, and those in which 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 there is a particular need for inspection automation. Highly sexual.

All of these objects to be inspected have the same structure as shown in FIG. 1(C).

In FIG. 1(C), 3 and 4 are objects having joints, 5 is the joint, and a lead wire (not shown) is connected to the joint 3 or 4.

The following describes only the inspection of flat package type parts with no lead connections and defects (including those that are completely floating and those that are in contact but are not soldered). .

It goes without saying that the same thing can be done with respect to the inspection of an object having the structure shown in FIG. 1(C) by using the method of the present invention.

First, the conventional method for visually inspecting the soldered parts of flat package components is the "Batte" method described below.
There are two methods of lleken.

The first method is to bring the vibrator into contact with the soldered part.
Therefore, vibration is performed at a frequency of 60 Hz to 200 IG (z), the vibration state at that time is detected by a vibration detector, and defects are determined based on the vibration state at this time. ([J%
3% patent 4.218.9224 The second method is to bring the vibrator into contact with the soldered part.
0Hz to 1MHz or +t i 5 GKHz to 65
The soldering part is vibrated by changing the frequency to 0KHz,
By detecting the thickness of the vibration at this time with a vibration detector, the frequency response of the soldered part can be measured, and defects can be determined based on this frequency response (U%8%Patent
4.287,766).

Although these methods have the advantage of directly detecting the joint state of the soldered parts, they have some drawbacks because they use a contact method to excite and detect vibrations.

(1) The carrying speed is slow. (2) Since it is a contact method, it is difficult to maintain a constant state of contact between the soldered part, the vibrator, and the detector, and the inspection reliability is low.

[Purpose of the invention]

The purpose of the present invention is to eliminate the problems of the prior art as described above, and to detect the contact state of joints by non-contact vibration excitation and non-contact detection, and to enable vibration detection with higher sensitivity. An object of the present invention is to provide an inspection method and apparatus that can detect the state of a joint with high precision.

[Summary of the invention]

One of the features of the present invention is to vibrate the object to be inspected (inspected object) at the joint without contact, and to optically detect the vibration state using laser speckles, etc., and to detect the detected vibration state. In the method of detecting the bonding state of a subject by analyzing the detection system, defocusing is performed in only one direction by inserting an optical means such as a cylindrical lens having a negative focal length into the optical detection system. This makes it possible to perform automatic inspection with high accuracy.

Another feature of the present invention is the device configuration, which includes a vibrating means for vibrating the object to be inspected in a non-contact manner, and a vibration state of the object to be inspected excited by the excitation means. - An apparatus for detecting a bonding state of an object to be inspected, comprising an optical means for detecting using the speckle, and an analysis means for analyzing the vibration state detected by the optical means and determining a defect. A cylindrical lens with a negative focal length is inserted into the means, so that minute rotational vibrations of the object to be inspected can be detected as large changes in the amount of light.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Before explaining the specific configuration of the present invention, FIG.

Referring to FIG. 2, the principle of the present invention will be explained.

That is, the inspected object shown in FIG. 1 (hereinafter referred to as the object to be inspected).

If the bonding state (method) of the objects (referred to as objects) differs, the elastic properties of the bonding state will differ. 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, as shown in FIG. 2, if the lead 8 of the flat package component 7 attached to the board 6 has a connection length or a defective part, soldering may cause vibration to the part 9 at the bottom of the lead 8. When air is blown through an air nozzle or the like and vibration is applied to the lead, good leads do not vibrate because they are firmly fixed to the board 6, but defective leads have no connection to the board and vibrate violently. .

The magnitude of this vibration is measured, and if the vibration exceeds a certain level, it is determined to be defective.

On the other hand, vibration detection is performed in the following manner.

When a laser beam is irradiated onto the main part of the object to be inspected and a sensor detects it, spots with high contrast called laser specks are observed. Laser speckle refers to a laser beam irradiated onto the surface of an object that has minute irregularities that can be considered as a random diffraction grating, causing diffraction by the diffraction grating, and the diffracted lights mutually interfere. Since this speck /I/ 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.

FIG. 5 shows an example of the configuration of the optical system.
0 is a laser oscillator, 11 is a 1-7 mirror, 12 is an object to be inspected, 13 is a detection optical system, and 14 is a sensor, which are arranged as shown in FIG.

In FIG. 5, the amount of spectrum movement Az in two directions is expressed by equation (1).

a: Distance between the object and the lens b: Distance between the lens and the imaging position Δ: Amount of defocus from the imaging position aχ: Amount of movement of the object in two directions Ωy Amount of rotation of the object around the y-axis Therefore, if the speckle is placed on the sensor imaging plane (defocus amount Δ=0), the movement i of the speckle will be equal to the movement amount of the object multiplied by the magnification.

On the other hand, by placing the sensor at a defocus position that is Δ apart from the image plane, the speckles will move even when the object rotates, and by setting a large defocus amount Δ, the speckles will move even when the object rotates. It is also possible to understand movement as the amount of speckle movement.

Generally, there are two types of optical sensors: storage type and non-storage type. Accumulating type senna measures the amount of incident light.

in a format that detects the result of integrating over a certain period of time.

A non-storage type sensor is of a type that detects temporal fluctuations in the amount of incident light.

If a vibrating laser speckle is detected with an accumulation type sensor, the position of the speckle spot will be vibrating, so the detected light amount at a certain point will also be observed as vibrating, and the laser speckle that is not vibrating will be observed. As shown in FIGS. 3(a) and 3(b), the amount of detected light is observed to be constant.

Accumulation type SE/If a vibrating laser speckle is detected, the position of the speckle spot is vibrating, so if the accumulation time is longer than the vibration period, the detected light amount at a specific point will be , is a constant value that does not depend on location. For this reason, the distribution of detection signals for speckles that are not vibrating is as shown in Figure 4 (a), where speckles with strong contrast are observed, and for speckles that are vibrating, as shown in Figure 4 (b).
), a blurred image with no contrast is observed.

Furthermore, although speckles remain in a narrow range at the imaging position, they spread out at the defocus position. If the objects to be inspected are lined up at a small pitch,
When the speckles spread out, the speckles from each object overlap, making it difficult to distinguish between them.

Therefore, by inserting a cylindrical lens to maintain the imaging relationship in the direction of alignment and defocusing in the direction perpendicular to this, the speckles from each object can be sufficiently separated, and the amount of defocus can be reduced. By increasing the size, it is possible to obtain sufficient vibration detection sensitivity.

On the other hand, if the average pitch of speckles is larger than the resolution of the sensor and is as small as possible, the change in the amount of light when the speckles move will be large.

The results of the experiment are shown in Figure 6.

When a cylindrical/trical lens with a positive focal length is used, as shown in Fig. 6(a), the speckle pitch is thick, but the cylindrical lens 1 with a negative focal length is used.
By inserting 3-2, the speckle pitch becomes smaller as shown in FIG. 6(b).

As described above, by inserting the negative cylindrical lens 16-2, minute rotational vibrations of the connection portion of the leads can be detected as large changes in the amount of light.

That is, the connection state of the joint can be detected in an enlarged manner, and highly accurate detection is possible.

Next, a specific configuration of the present invention will be shown and explained.

FIG. 7 shows the configuration of an inspection device for determining defects with no lead connection in the above-described flat package type components.

As shown in FIG. 7, the inspection device uses an excitation system that uses an air nozzle 15 to blow turbulent air jets onto several parts of the solder at multiple locations to be inspected, and to excite leads with poor connections. 16, and a laser 17 for irradiating the solder portion Q with a laser beam.

An illumination optical system 18, a laser irradiation optical system 20 from a no-f mirror 19, a lens 21 for detecting laser speckles, and a cylindrical lens 21-2 having a negative focal length. , a detection optical system 23 consisting of an accumulating linear sensor 22, an X-Y table 24 for positioning the inspection object, a jet flow control section 25 for controlling the air jet, a senna drive circuit 26, and a table controller 27. It consists of a laser control rack 28, a defect determination section 29, and a control section 51 consisting of an overall control section 50.

Further, FIG. 8 outlines the overall operation of the inspection by the inspection apparatus of FIG. 7.

Prior to the inspection, X-
The Y table 24 is moved to the inspection start position, the laser beam starts to irradiate the top surface of the lead to be inspected, and the air jet starts to be ejected from the air nozzle 15 to the solder portion Q.

Next, perform the inspection by repeating the following operations.

That is, the X-Y table 24 is driven to position the leads on one side of the flat package component 7 to be inspected to the inspection position, and a laser beam is irradiated onto the top surface of the leads.
Create a state in which the air jet is sprayed onto several parts of the solder.

In this state, the non-defective leads do not vibrate, but the defective unconnected leads vibrate. This state is detected by an accumulation-type linear sensor 2 whose sample rate is greater than the vibration frequency.
2, and the laser speckle shown in FIG. 9 is obtained.

Defect determination χ is performed based on the state of laser speckles at locations corresponding to each lead.

Next, the defect determination method will be described.

As shown in FIG. 9, the laser speckle obtained by the accumulation type linear sensor 22 detects a waveform 32 with a thin pitch and severe irregularities since the lead does not vibrate in the case of a good lead.

However, in the case of a defective lead with no connection, the lead vibrates, the speckle vibrates, and since this is detected in an integrated form, a gentle waveform 63 is detected. To calculate this difference, we Fourier transform the speckle image corresponding to each lead, normalize it using the 0 component, and then take the maximum value of the high-order component in a certain interval. Determine small leads as defective.

Variations of this judgment method include the following.

(b) Calculate the sum of speckle waveforms whose differential values or absolute values of multi-order differential values are larger than a predetermined value, and determine a lead whose sum is smaller than a predetermined threshold value to be defective.

(b) A lead in which the average pitch at a location where the speckle waveform has an extremely thick value is smaller than a predetermined threshold value is determined to be defective.

Next, a second embodiment will be explained with reference to FIG.

In FIG. 10, the same reference numerals as in FIG. 7 indicate the same components. In FIG. 10, the detection optical system 23 includes a condensing optical system 21 for detecting laser speckles, and a cylindrical optical system for defocusing in the y direction while maintaining the imaging relationship in the χ direction. Lens 21-
2 and a non-storage type linear sensor 34 with a parallel output.

The overall operation of the inspection apparatus will be explained using FIG. 8 mentioned above.

Prior to the inspection, first, by command from the overall control unit 3o,
- Move the Y table 24 to the inspection start position and start irradiating the upper surface of the lead with the laser beam. Next, perform the inspection by repeating the following operations.

That is, the X-Y table 24 is driven to position one side of the leads of the flat package component 7 to be inspected to the inspection position, and the air nozzle 15 starts spraying an air jet onto the solder portion Q. In this state, the good reeds do not vibrate, but the defective unconnected reeds vibrate.

This state is observed by a non-storage type parallel output IJ near sensor 39 to obtain the time fluctuation of laser speckle shown in FIG. The laser at the location corresponding to each lead obtained.
Accumulate the temporal fluctuations of speckle in Huffer 40,
Defects are determined based on this accumulated time variation.

Next, a defect determination method will be explained.

First, for the laser speckle obtained with a non-storage type parallel output linear sensor, since the component lead does not vibrate for a good product, the amount of detected light hardly changes as shown in Figure 5(a) K. For a defective lead with no connection, the detected light amount oscillates as shown in FIG. 3(4) because the component lead oscillates at the lead's own vibration frequency. By analyzing the temporal variation of this laser speckle with a spectrum analyzer, a waveform as shown in FIG. 11 is obtained. A lead whose peak frequency position in this frequency region is higher than a predetermined threshold value is determined to be defective.

A modification of this defect determination method will be explained.

(b) Binarize the time fluctuation of speckle in floating form and
'' to ``1'' or ``1'' to ``0'' is calculated, and this value is determined to be defective when the dog lead exceeds a predetermined threshold.

(b) Binarize the floating form in the same way as in (a), calculate the average value of the pitch that changes from "o" to "1" or from "1" to "0", and if this value is lower than the predetermined threshold Determine small leads as defective.

In addition, the following is a modification of Senna used in this method.
There is something to do.

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

(b) Point senna such as Photomaru. Using this sensor, the X-Y table is driven one location at a time in a step-and-repeat manner to perform inspection.

This embodiment has the following effects.

(a) Since the temporal fluctuations of laser speckle are measured, the vibration frequency of the lead can be determined, and since there is a large amount of information, the reliability is high and it is possible to make judgments that will not overlook any defects.

(b) Since the vibration is performed using a turbulent air jet that captures the flow rate, even if a poorly connected lead hits some solder and cannot vibrate at the natural frequency of the lead, it will not vibrate at the frequency of the flow rate. It can generate vibrations and detect them.

In addition, there are other methods that were not explained in the two embodiments described above, but will be described below.

(a) Vibration method in which the direction of the jet flow is vibrated, and these vibrations are used in addition to the turbulent flow. This method includes
It has the same effect as an air jet with oscillating flow rate.

(b) A method of using a diffraction grating instead of a cylindrical lens as an optical component for defocusing (observing a diffraction image). This method has the same effect as using a cylindrical lens.

b) A system in which a two-dimensional sensor is used instead of a linear sensor as an accumulative optical sensor. This method has the advantage of being able to perform highly reliable inspections because it captures images in two dimensions.

(d) As a defect determination method, the speckle waveform before air jet blowing is also captured, and defects are determined by comparing before and after blowing. This method has the feature of high reliability because it performs before-and-after comparisons.

As mentioned above, the embodiments of the present invention include the vibration method of each food,
There are implementation modes of the vibration detection method and the defect determination method, and these are summarized below.

(1) Vibration method (a) Injection of air jet using only turbulence (b) Injection of air jet with flow rate vibration added ()・) Injection of air jet with vibration in the jet direction (2) Vibration detection Method (a) Method of detecting time fluctuations (b) Method of detecting with an accumulation type linear sensor whose accumulation time is longer than the period of natural vibration of the lead to be inspected (c) Method of detecting the accumulation time due to the characteristic of the lead to be inspected Detection method using an accumulation-type two-dimensional sensor with a period longer than the frequency period (3) Defect determination method (2) Method using only the vibration state of speckles during vibration (2) Vibration state of speckles before and after vibration Although only these typical combinations are shown as examples, any combination can be tested, and 18 different examples are possible.

As already mentioned, the test object shown in FIG. 1C, which has a connection structure similar to the soldered portion of a flat package component, can also be tested in the same way.

〔Effect of the invention〕

As is clear from the above-mentioned embodiments, according to the present invention, the state of the soldering parts of flat package parts of printed circuit boards and the connection parts such as wire bonding parts of LSI etc. is vibrated in a non-contact manner. Since the vibration state can be detected with high sensitivity, these inspections that conventionally relied on visual inspection can be performed reliably and automatically, and can also detect minute rotational vibrations in connections and connections as large changes in light intensity. Therefore, the detection accuracy is extremely high.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view of an object to be inspected for the joint state of circuit components according to the present invention, FIG. 1(a) is a perspective view of a solder part of a flat package type component, and FIG.
Perspective view of wire bonding locations such as I, Figure 1 (C
) is a perspective view of a connection part of a general circuit component. Figure 2 is a perspective view of a soldered part of a flat package component that is an example of the inspection target, Figure 3 is a waveform diagram of speckle detection by a non-accumulative sensor, and Figure 3 shows speckle detection for non-defective products. Detection waveform diagram, Figure 5 (J) shows a speckle detection waveform diagram for a defective product, Figure 4 shows a speckle detection image by an accumulation type sensor, Figure 4 (a) shows a diagram for a good product, Figure 4 ( A) is a diagram for a defective product, Figure 5 is a perspective view to explain the principle of defocus, Figure 6 shows the effect when a cylindrical lens is inserted, and Figure 6 (a) is an experimental diagram. The configuration of the device is shown in Figure 6 (4).
, (C) shows the distribution diagram in the y direction of the waveform detected by the Senna, (Rei) shows the distribution diagram when a cylindrical lens with a positive focal length is inserted, and (C) shows the distribution diagram with a negative focal length. It is a distribution diagram when a cylindrical lens is inserted. Fig. 7 is a configuration diagram of the bonding state inspection device of the first embodiment, Fig. 8 is an operation/case diagram of the first embodiment, and Fig. 9 is a waveform detected in the first embodiment. It shows. Fig. 10 is a device configuration diagram of the second embodiment, and Figs. 11(a) and (b).
) is a waveform diagram detected in the second example. 1... Solder part of flat package type part, 2... Wire bonding location of LSI etc., 3.4... Object. 5...Joint part, 6...Board, 7...Parts such as LSI, 8...Component lead, 9...On board wiring pattern. 10... Laser, 11... Half mirror, 12... Target, 13... Detection optical system, 16-2... Cylindrical lens, 14.
...Sensor, 15...Air nozzle. 16...Excitation system, 17...Laser, 18...Irradiation optical system, 19...Half mirror, 20...V- The irradiation optical system, 21...Condensing optical system. 21-2...Siri/trical lens. 22... Storage type linear sensor, 25...
...Detection optical system, 24...X-Y table, 25...Jet flow control section, 26...Sensor drive circuit. 27...Table controller. 28... Laser control circuit, 29... Defect determination section, 30... Overall control section, 61... Control section, 52.55... ...Laser speckle, 64...
...Parallel output linear senna.

Claims (3)

[Claims] (1) The joint of the circuit component terminal is vibrated in a non-contact manner by an air jet means, and the vibration state is detected via a laser irradiation optical system and a condensing optical system, and a focal point inserted into the condensing optical system A circuit component terminal characterized in that the bonding state of the bonding portion is detected by defocusing in only one direction using an optical means having a negative distance, and analyzing the vibration state obtained by the defocusing. bonding condition inspection method. (2) An excitation means for vibrating a terminal joint of a circuit component in a non-contact manner, and a laser irradiation optical system and a condensing optical system for detecting the vibration state of the joint excited by the excitation means. , and a detection optical system consisting of an optical means inserted into the condensing optical system and having a negative focal length and defocusing in only one direction, and analyzing the vibration state detected by the detection optical system,
A bonding state inspection device for circuit component terminals, comprising an analysis means for determining a defect in a bonded portion. (3) The device for inspecting the bonding state of circuit component terminals according to claim 1, wherein the optical means having a negative focal length and defocusing in only one direction is a cylindrical lens. .