KR102228802B1 - Bonding defect inspection method using interference fringe during display panel PCB bonding process - Google Patents

Abstract

The present invention relates to a bonding defect inspection method using an interference fringe during a display panel PCB bonding process. More specifically, the present invention relates to a bonding defect inspection method using an interference fringe during a display panel PCB bonding process, which is able to reduce cost by using an ACF in a powder form to be used for electrically connecting an FPC and a PCB, to check a contour line-shaped interference fringe on the relevant part by photographing the bonding part by a photographic apparatus when inspecting a bonding defect after a compression bonding through the ACF powder, to check if the height of the contour line of the interference fringe falls under the preset range height difference, and to allow a user to easily inspect for bonding defects.

Description

Bonding defect inspection method using interference fringe during display panel PCB bonding process}

The present invention relates to a bonding defect inspection method using an interference pattern during the bonding process of a display panel PCB to enable inspection of bonding defects when bonding through powder-type ACF.

In general, LCD panels (hereinafter, substrates) are provided in electronic devices such as mobile phones, mobile terminals, and liquid crystal TVs. Such a substrate may be typically mounted on a substrate by a FOG (Film On Glass) / FOP (Film On Panel) method or a COG (Chip On Glass) / COP (Chip On Panel) method.

That is, in the FOG/FOP bonding method, an anisotropic conductive film (hereinafter, ACF) is attached to an electronic circuit electrode printed on a substrate made of glass or plastic, and a film or FPC is disposed on the ACF, and an appropriate pressure is applied. It is a method in which the ACF and the electrode of the substrate are brought into contact with each other to conduct.

At this time, the ACF contains conductive particles, and when a certain pressure is applied, the insulating film is broken, so that electricity can be applied through the conductive particles.

However, in the case of the conventional ACF conductive ball in the form of grains, there is a problem that the cost is high, so an alternative to solve this problem is urgently emerging.

Korean Registered Patent Publication No. 10-1151982 (registered on May 24, 2012)

The present invention has been conceived to solve the above problems, and an object of the present invention is to reduce the manufacturing cost by electrically connecting the FPC and the PCB by using ACF in powder form instead of conductive balls in grain form. In order to check the bonding state and poor bonding of the powder, by checking the interference pattern in the form of contour lines generated at the FPC and ACF attachment locations through an imaging device such as an interferometer, by checking the height difference at the contact area through the interference pattern, The present invention relates to a bonding defect inspection method using an interference pattern during a display panel PCB bonding process, which enables the bonding defect to be determined according to whether the height difference corresponds to a height difference within a preset range.

Other objects and advantages of the present invention will be described below, and will be understood by examples of the present invention. Further, the objects and advantages of the present invention can be realized by means and combinations shown in the claims.

The present invention is a means for solving the above problems,

ACF applied between the FPC 10 and the PCB 20 to electrically connect each other is used as a powder-type ACF powder 30, and whether the ACF is evenly distributed and bonded in the preset bonding pressure range. In order to confirm the bonding defect, the change in bending according to the degree of pressing of the FPC 10 is checked as a height difference (H), and the degree of compression between the FPC 10 and the PCB 20 is examined,

The height difference (H) is a contour shape generated at the FPC 10 and the ACF attachment position after the FPC 10 and the PCB 20 are crimped in a preset bonding pressure range, and then the crimped surface is imaged through an imaging device. By checking the interference pattern (A) of, it is possible to determine the bonding defect of the ACF according to whether the measured height difference (H) of the FPC 10 falls within the height difference (H') of the preset range. It is characterized.

As described above, the present invention has an effect of reducing manufacturing cost by using ACF powder that is not in the form of a ball for compression bonding between the FPC and the PCB.

In addition, the present invention is easy by checking whether the height according to the contour line of the interference pattern corresponds to the height difference in the preset range by imaging the contour line shape interference pattern of the compressed area through various image pickup devices after bonding compression using ACF powder. There is an effect that can easily inspect the amount of bonding.

1 is a conceptual diagram of an embodiment showing an ACF powder bonding defect inspection method according to the present invention.
2 is a view showing an interference pattern in the form of a contour image captured by an interferometer in the ACF powder bonding defect inspection method according to the present invention.
3 and 4 are diagrams showing the configuration of an interferometer according to the present invention.
5 and 6 are diagrams showing differences in images obtained according to the used lighting.

Before describing various embodiments of the present invention in detail, it will be appreciated that the application is not limited to the details of configurations and arrangements of elements described in the following detailed description or illustrated in the drawings. The present invention can be implemented and practiced in different embodiments, and can be carried out in various ways. Also, device or element orientation (eg "front", "back", "up", "down", "top", "bottom" The expressions and predicates used herein with respect to terms such as ", "left", "right", "lateral"), etc. are used only to simplify the description of the present invention, and related devices Or you will find that the element simply does not indicate or implies that it should have a particular orientation. Further, terms such as “first” and “second” are used in this application and the appended claims for purposes of explanation and are not intended to represent or imply any relative importance or spirit.

The present invention has the following features to achieve the above object.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventors appropriately explain the concept of terms in order to explain their own invention in the best way. Based on the principle that it can be defined, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention.

Accordingly, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiment of the present invention, and do not represent all the technical spirit of the present invention. It should be understood that there may be equivalents and variations.

Looking at an embodiment according to the present invention is as follows.

The ACF applied between the FPC 10 and the PCB 20 to electrically connect each other is used as a powder-type ACF powder 30, and the ACF powder 30 is evenly distributed in a preset bonding pressure range. In order to check whether the bonding is successful or not, depending on the degree of compression between the FPC 10 and the PCB 20, the change in bending that occurs when the FPC 10 is pressed is determined by the FPC lead 11 and the FPC lead 11. ) By checking the height difference (H) of the FPC (10) formed between the gaps, by checking the bonding defect of the ACF powder (30),

The height difference (H) is a contour shape generated at the FPC 10 and the ACF attachment position after the FPC 10 and the PCB 20 are crimped in a preset bonding pressure range, and then the crimped surface is imaged through an imaging device. By checking the interference pattern (A) of, it is possible to determine the bonding defect of the ACF according to whether the measured height difference (H) of the FPC 10 falls within the height difference (H') of the preset range. It is characterized.

In addition, the interference fringe (A) has a larger height difference (H) as the shape of the contour line becomes denser or the number of contour lines increases, and the center of the contour line means the lowest point (B) in the entire contour line, and the height difference ( It is characterized in that the number of measurements of contour lines identified according to H) corresponds to the number of preset contour lines.

In addition, the height difference (H) may vary for each measurement even in the same preset bonding pressure range, and may be different for each measurement depending on the application state of the ACF powder 30 and the surrounding conditions to be applied. It is characterized by that.

In addition, the imaging device is characterized in that the interferometer 40 or line scan in which the AREA camera is installed is used.

In addition, the interferometer 40 generates an interference fringe (A) as the light for imaging passes from the light source 41 to the beam splitter 42, splits into two, and then merges together, and the interference fringe (A) Is caused by the difference in the phase difference or refractive index of the light generated when the distance between the two paths is different when the light is split and combined, and the focusing and tilting of the reference mirror 43 reflecting light from the inside. It is characterized in that the flatness between the reference mirror 43 and the FPC 10 mounting surface can be matched through an adjustment knob capable of adjusting (Tilt).

In addition, the imaging device changes the wavelength of the illumination so that it is possible to clarify the check of the interference pattern (A) in the form of a contour line, and as the wavelength of the illumination, the illumination passes through the FPC 10 and the upper surface of the PCB 20 The PCB lead 21 is visible, and in the empty space between the PCB lead 21 and the PCB lead 21, the red series long wavelength that can clearly define the interference pattern A in the form of a contour line formed on the surface of the FPC 10 A display panel PCB, characterized in that a blue-series short wavelength is used or the light does not pass through the FPC 10 and the interference pattern A in the form of a contour line formed on the surface of the FPC 10 is clearly used. Bonding defect inspection method using interference fringes during bonding process.

Hereinafter, a bonding defect inspection method using an interference pattern during a display panel PCB bonding process according to a preferred embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6.

A bonding defect inspection method using an interference pattern in the display panel PCB bonding process according to the present invention is as follows.

First of all, in order to electrically connect the various FPCs 10 and PCBs 20, a ball-shaped ACF is applied between each other, and then the upper part of the FPC 10 is crimped, and the ACF conductive balls are broken. The ball-shaped ACF is used as a powder-type ACF (ACF powder 30) in the present invention, thereby reducing cost.

Thereafter, the ACF powder 30 is evenly distributed in the preset bonding pressure range and it is necessary to check whether the bonding is defective or not. In the present invention, the problem is solved through imaging through an imaging device.

To explain this in detail,

In order to bond the FPC 10 and the PCB 20 to each other, the FPC 10 is crimped as described above. At this time, the bending change according to the degree of pressing of the FPC 10 is determined by the FPC lead 11 and the FPC lead. (11) By checking the height difference (H) of the FPC 10 formed between the gaps, the degree of compression between the FPC 10 and the PCB 20 can be inspected.

That is, a PCB lead 21 to be electrically connected is formed on the upper surface of the PCB 20, and the FPC 10 that is positioned corresponding to the upper surface of the PCB 20 and pressed is also formed with an FPC lead 11 on the lower surface. , ACF powder 30 is applied between the contact areas between the PCB lead 21 and the FPC lead 11, and when the FPC 10 and the PCB 20 are pressed and bonded to each other, as shown in FIG. The attachment part (contact position) between the FPC 10 and the PCB 20 creates a height difference (H) with other parts without a lead.

Thus, in order to check the height difference (H) of the FPC (10),

After the FPC 10 and the PCB 20 are crimped to a preset bonding pressure range, when the crimping surface is imaged through an image pickup device, as shown in FIG. 2, a contour line is obtained for each FPC 10 and ACF attachment position. The interference fringe (A) in the shape can be checked. Accordingly, the height difference (H) (shape of the contour line) of the FPC 10 that can be measured through the interference fringe (A) is the height difference (H') of the preset range. By checking whether it corresponds to, it is possible to determine the bonding defect of the ACF powder 30 on the corresponding part.

As shown in FIG. 2, it is determined that the shape of the contour line of the interference pattern (A) becomes more compact, or the height difference (H) increases as the number of contour lines increases. Of course, for each of various preset bonding pressures After measuring the range of the contour line height (FPC (10) height difference) as a reference in advance, as shown in FIG. 1, the measured height difference (H) is the height difference in the preset range at an appropriate bonding pressure preset based on this. Compared with (H'), the measured height difference (H) is not defective if the preset range height difference (H') is applicable, and is relatively higher or higher than the preset height difference (H'). The low case is selected as a defect.

The center of the contour line is the center to be compressed, and may mean the lowest point (B) in the entire contour line. (The lowest point (B) described above in the contour line may be applied as the highest point according to the embodiment).

Of course, the height difference (H) measured in this way may vary with each measurement even in the same preset bonding pressure range, and the application state of the ACF powder 30 and the applied ambient conditions (temperature, humidity, pressure bonding) Also, depending on the method, etc.), the height difference as the reference may be different for each measurement, and thus the height difference as the reference is previously designated as a height difference H'in a preset range.

Of course, the range of the number of contour lines to be measured according to the height difference (H) is in the preset range of the number of contour lines for each height difference (H), which is preset for each height difference (H) and stored in a DB. It should be true.

In the case of the imaging device, in the present invention, an interferometer 40 or a line scan installed with an area camera is used, but it is natural that such an imaging device can be variously changed according to a user's embodiment.

In the interferometer 40 forming the interference fringe A in the present invention, as shown in Figs. 3 and 4, the light for imaging is bifurcated from the light source 41 to the beam splitter 42. The interference pattern (A) is generated when the light is split and combined, and the interference pattern (A) is generated due to the difference in phase or refractive index of light generated due to the different distances of the two paths when the light is split and combined. Flatness between the reference mirror 43 and the FPC 10 installation surface through an adjustment knob that can adjust the focusing and tilt of the reference mirror 43 that reflects light from the inside. To be able to match, such an interferometer 40 is a well-known technique.

In addition, in the case of such an imaging device,

It is possible to clarify the check of the interference pattern (A) in the form of contour lines by changing the wavelength of the illumination used (a source of illumination is that various light sources may be used depending on the embodiment of the laser and the user, as well as LED). However, looking at the effect according to the wavelength of the used lighting is as follows.

1. In case the lighting is red series long wavelength,

The lighting passes through the FPC 10 so that the PCB lead 21 on the upper surface of the PCB 20 is visible, and a contour line formed on the surface of the FPC 10 in the empty space between the PCB lead 21 and the PCB lead 21 The interference pattern (A) of the shape can be clearly identified, so that the overall bonding strength can be judged.

2. If the lighting is Blue series short wavelength,

Since the lighting does not pass through the FPC 10, the PCB lead 21 is difficult to see, and the interference pattern (A) in the form of a contour line formed on the surface of the FPC 10 can be clearly obtained, so that the overall contour line can be obtained. It is lost.

In other words, when bonding at high pressure/high temperature outside of the preset bonding pressure range, grains of ACF powder 30 may occur on the surface of the PCB lead 21, and this may appear as the highest point of the contour line to be inspected as a defect. It can be.

As described above, although the present invention has been described by the limited embodiments and drawings, the present invention is not limited thereto, and the technical spirit of the present invention and the following by those of ordinary skill in the technical field to which the present invention pertains. It goes without saying that various modifications and changes are possible within the equivalent range of the claims to be described.

10: FPC 11: FPC lead
20: PCB 21: PCB lead
30: ACF powder 40: interferometer
A: Interference pattern B: Lowest point
H: ACF height difference
H': Preset range height difference

Claims (6)

ACF applied between the FPC (10) and the PCB (20) to electrically connect each other is used as a powder-type ACF powder (30),
In order to check whether the ACF powder 30 is evenly distributed in the preset bonding pressure range and bonded or not, according to the degree of compression between the FPC 10 and the PCB 20, the FPC 10 is pressed. By confirming the resulting bending change by the height difference (H) of the FPC 10 formed between the FPC lead 11 and the FPC lead 11 interval, by confirming the bonding defect of the ACF powder 30,
The height difference (H) is
After the FPC (10) and the PCB (20) are compressed in a preset bonding pressure range, the compressed surface is imaged in a plane through an image pickup device, and the contour shape generated at the attachment position of the FPC (10) and ACF powder (30). By checking the interference fringe (A), depending on whether the measured height difference (H) of the FPC 10 identified through the interference fringe (A) falls within the height difference (H') of the preset range, the ACF Allows to determine bonding defects,
The interference pattern (A) is that the height difference (H) is larger as the shape of the contour line becomes denser or the number of contour lines increases, and the center of the contour line means the lowest point (B) in the entire contour line, and the height difference (H) The number of measurements of contour lines checked according to the number corresponds to the preset number of contour lines,
The height difference (H) may vary for each measurement even in the same preset bonding pressure range, and may be different for each measurement depending on the application state of the ACF powder 30 and the applied ambient conditions,
The imaging device is an interferometer 40 equipped with an AREA camera, or a line scan,
The interferometer 40 is
The light for image pickup passes through the beam splitter 42 from the light source 41, splits into two, and then merges to generate an interference pattern (A), and the interference pattern (A) is divided into two when the light is split and combined. It is caused by the difference in the phase difference or refractive index of light generated due to different path distances, and adjustment that can adjust the focusing and tilt of the reference mirror 43 that reflects light from the inside. Through the knob, it is possible to match the flatness between the reference mirror 43 and the mounting surface of the FPC 10,
The imaging device
By changing the wavelength of the illumination, it is possible to clarify the check of the interference pattern (A) in the form of a contour line. As the wavelength of the illumination, the illumination passes through the FPC 10 and the PCB lead 21 on the upper surface of the PCB 20 is Can be seen, and in the empty space between the PCB lead 21 and the PCB lead 21, a red series long wavelength that can clearly define the interference pattern A in the form of a contour line formed on the surface of the FPC 10 is used, or the illumination The interference pattern during the display panel PCB bonding process, characterized in that a blue-series short wavelength that does not pass through the FPC 10 and can clarify the contour-shaped interference pattern (A) formed on the surface of the FPC 10 is used. Bonding defect inspection method used.
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