JP2006147766A - Method for connecting cof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for connecting a COF by which the COF can be fitted efficiently and surely. <P>SOLUTION: The method for connecting a COF 2 includes a step to fit the COF 2 to a liquid crystal panel 1 by means of an anisotropical conductive film 3. The fitting step includes a heat crimping step to pinch a buffer material 13 between the COF 2 and a heating head 10, and to press it while heating it by the heating head 10. The heat crimping step includes a step for crimping while pressing down the heating head 10 by downward thrust force obtained from the following formula. Formula is expressed as follows: (Downward thrust force)=(Width of COF)×(Crimping length of COF)×(Pressure required for crimping)×(Number of COFs)+(Total length of board space)×(Crimping length of COF)×(Pressure required for crimping)×(Conversion factor). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a COF connection method.

  In an electronic device, as a member for mounting an IC (Integrated Circuit) chip, there is a COF (Chip On Film) in which an IC chip is connected and fixed to a base film. For example, in a liquid crystal display device, in order to drive each pixel, a COF in which an IC chip is arranged is connected to a liquid crystal display panel in which liquid crystal is sealed between a pair of glass substrates. In the manufacturing process of the liquid crystal display device, there is a process of connecting and fixing the COF to the liquid crystal display panel.

  As a method of connecting an IC chip to a liquid crystal display panel, a method called a COG (Chip On Glass) method in which a driving IC chip is directly formed on a liquid crystal display panel in addition to using a COF, or a method called a TCP (Tape Carrier Package) method. There is. In TCP, a wiring pattern is formed on a tape-like substrate such as polyimide, and an IC chip is connected and fixed to the wiring pattern. The TCP is connected and fixed to the liquid crystal display panel in the same manner as the COF. In TCP, the thickness of the substrate serving as a base material is thicker than that of COF. TCP is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-291738.

  When TCP or COF is connected and fixed to the liquid crystal display panel, an anisotropic conductive film (ACF) is used. An anisotropic conductive film is a tape-like adhesive in which conductive particles are dispersed.

  FIG. 6 shows a schematic cross-sectional view of the process of connecting and fixing the TCP to the liquid crystal display panel. The liquid crystal display panel includes, for example, a pair of glass substrates. An electrical circuit is formed on the surface of one glass substrate 1b, and the TCP 5 is connected to this electrical circuit. An anisotropic conductive film 3 is disposed at a bonding portion between the TCP 5 and the glass substrate 1b. Since a plurality of IC chips are connected to the liquid crystal display panel, a plurality of TCPs 5 are connected to the surface of the glass substrate 1b. TCP5 is arrange | positioned at equal intervals. The anisotropic conductive film 3 is formed in a strip shape so as to extend in the direction in which the TCPs 5 are arranged.

  In bonding the TCP 5, the TCP 5 is heated while being pressed by the heating head 10 as indicated by an arrow 39. By this thermocompression bonding, the TCP 5 is fixed to the glass substrate 1b through the anisotropic conductive film 3. The plurality of TCPs 5 are thermocompression bonded at once by the heating head 10. By performing pressure bonding with the anisotropic conductive film 3 interposed therebetween, the wiring formed on the surface of the TCP 5 and the wiring formed on the surface of the glass substrate 1b of the liquid crystal display panel are electrically connected to each other without being short-circuited. can do.

  When thermocompression bonding is performed using the heating head 10, it is preferable that the cushioning material 14 is disposed between the heating head 10 and the TCP 5 to be crimped (see, for example, Japanese Patent Laid-Open No. 5-25829). By arranging the buffer material 14, the pressing force of the heating head can be made uniform in each TCP.

  The buffer material 14 includes a polyimide film or the like and has elasticity. As shown in FIG. 6, when the heating head 10 is pressed in the direction indicated by the arrow 39, the cushioning material 14 is recessed. At this time, a gap 21 is formed between the buffer material 14 and the anisotropic conductive film 3. That is, the buffer material 14 contacts only the TCP 5 without contacting the anisotropic conductive film 3.

  FIG. 7 shows a schematic cross-sectional view of the process of bonding and fixing the COF to the liquid crystal display panel. Similarly to TCP, COF2 is bonded using anisotropic conductive film 3 in order to electrically connect the wiring on the surface of glass substrate 1b and the wiring of COF2. A strip-shaped anisotropic conductive film 3 is disposed on the surface of the glass substrate 1b, and a plurality of COFs 2 are disposed on the upper surface thereof. The COF 2 is formed so that the planar shape is rectangular. The COFs 2 are arranged in a line.

  In the step of thermocompression bonding COF, first, the anisotropic conductive film 3 is disposed on the surface of the glass substrate 1b of the liquid crystal display panel. Next, the position of the COF is aligned with the surface of the anisotropic conductive film 3 and temporarily bonded. Next, the COF 2 is pressed while applying the downward thrust indicated by the arrow 40 to the heating head 10 heated to approximately 300 ° C. or more and 400 ° C. or less. The COF 2 is pressed so that the pressure applied to the COF 2 is approximately 2.5 MPa to 3.5 MPa. A plurality of COFs 2 are bonded at the same time. As the cushioning material 14, for example, a silicon rubber sheet is used, and a sheet having a thickness of 0.2 mm or more and 0.3 mm or less is used in consideration of pressure uniformity and mechanical strength when thermocompression bonding is performed. ing.

  The downward thrust of the heating head when performing COF thermocompression bonding using an anisotropic conductive film is calculated by the following calculation formula.

(Descent thrust) = (COF width) × (COF crimping length) × (pressure required for crimping) × (number of COFs) (1)
Here, the crimping length of the COF is a length in a direction perpendicular to the width direction of the COF 2 in a region where the COF 2 and the glass substrate 1b are in contact with each other. (COF width) × (COF compression length) indicates an adhesion area between the COF 2 and the glass substrate 1b. That is, the above-mentioned descending thrust is calculated by multiplying the thrust required for crimping COF per sheet by the number of COFs.

  Japanese Patent Application Laid-Open No. 2001-291738 discloses a connection method in which TCP is pressure-bonded using a pressure-sensitive light-emitting film in the step of thermocompression bonding to a liquid crystal display panel. In this method, the quality of thermocompression bonding is determined by observing the light emission state of the pressure-sensitive light-emitting film visually or with a microscope after completion of the thermocompression bonding operation. It is disclosed that in a portion where thermocompression bonding is defective, it is possible to eliminate all defects by repeating the operation of thermocompression bonding.

In JP 2003-249734 A, a wiring board such as a printed board is connected to the printed circuit board by thermocompression bonding so that the printed circuit board has the same wiring pattern on the back surface as the printed circuit board. A connection method for forming a dummy wiring pattern having a width and an interval is disclosed. In this connection method, it is disclosed that a uniform pressure can be applied to the wiring patterns to be connected, the connection between the wiring patterns does not become defective, and the occurrence of poor conduction can be prevented.
Japanese Patent Laid-Open No. 2001-291737 JP-A-5-258829 JP 2003-249734 A

  Referring to FIG. 6, when connecting TCP 5 to glass substrate 1 b, gap portion 21 is formed between buffer material 14 and anisotropic conductive film 3. It can be pressed uniformly.

  However, referring to FIG. 7, when a COF is connected to the glass substrate 1b, for example, when the cushioning material 14 includes a silicon rubber sheet having a thickness of 0.2 mm or more and 0.3 mm or less, 2.5 MPa When the pressure of 3.5 MPa or less is applied, the silicon rubber sheet is compressed by 50 μm or more. Since the thickness of the COF 2 is about 50 μm, the buffer material 14 directly contacts the anisotropic conductive film between the COFs 2 in addition to the COF 2. For this reason, there has been a problem that sufficient pressure cannot be applied to COF2.

  In particular, when the size of the liquid crystal display panel increases and the end of the glass substrate 1b becomes longer, the distance between the COFs 2 becomes longer, and the pressure applied to the COF 2 becomes insufficient. . As a result, there is a problem that a connection failure occurs between the wiring formed on the COF 2 and the wiring formed on the glass substrate 1b.

  In the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2001-291738, there is a problem that it takes time because the thermocompression bonding process is repeated again when the adhesion state is poor. Further, since the thermal paper cannot be measured accurately when the temperature becomes high, there is a problem that only relative pressure measurement can be performed.

  In addition, it is conceivable to measure the downward thrust of the heating head with pressure sensitive paper before thermocompression bonding. However, since the length of the area where the COF is adhered, the size of the COF, or the number of the COFs are different for each model, there is a problem that measurement with a pressure sensitive paper is necessary every time thermocompression bonding is performed for different models. .

  Furthermore, in order to measure an absolute pressure using thermal paper, it is necessary to measure in a state where the temperature is lowered. The heating head loses its balance when the temperature changes. For this reason, it is necessary to adjust the balance each time the temperature of the heating head is lowered, and there is a problem that it takes time.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a COF connection method capable of attaching a COF efficiently and reliably.

  In order to achieve the above object, a COF connection method according to the present invention includes an attachment step of connecting a COF to a substrate through an anisotropic conductive film, and the attachment step includes a cushioning material as the COF and a heating head. And a thermocompression bonding step in which the COF is pressed while being heated by the heating head. The thermocompression bonding step includes a step performed while pressing the heating head with a downward thrust obtained by the following equation.

(Descent thrust) = (COF width) × (COF crimping length) × (pressure required for crimping) × (number of COFs) + (total board space) × (COF crimping length) × (crimping) Required pressure) x (conversion factor)
Here, (conversion factor) = (pressure applied to the surface of the substrate between the COFs) / (pressure applied to the surface of the COF). By adopting this method, it is possible to provide a COF connection method capable of attaching the COF efficiently and reliably.

  Preferably, in the above invention, the conversion factor is obtained by measuring pressure using pressure sensitive paper. By adopting this method, the conversion factor for calculating the descending thrust can be easily obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the connection method of COF which can attach COF efficiently and reliably can be provided.

  With reference to FIGS. 1 to 5, a COF connection method according to an embodiment of the present invention will be described. “COF” in the present invention indicates that the thickness of the COF film (the thickness of the portion to be connected and fixed) is 30 μm or more and 55 μm or less. The standard thickness of the COF film is 46 μm, which is the sum of the thickness of the substrate of 38 μm and the thickness of the wiring copper foil of 8 μm. In addition to this, there are many types of base materials and copper foils, and considering the thickness of each base material and copper foil, the thickness of the COF film is about 30 μm to 55 μm. It is.

  FIG. 1 is a schematic perspective view of a main part of a thermocompression bonding apparatus for connecting a COF in the present embodiment. In this embodiment, a COF is connected to the liquid crystal display panel.

  For example, the liquid crystal display panel 1 includes glass substrates 1a and 1b. The glass substrate 1a and the glass substrate 1b are bonded and fixed by a sealing material so that the main surfaces face each other. In a space sandwiched between the glass substrate 1a and the glass substrate 1b, liquid crystal is sealed inside the sealing material.

  Pixel electrodes are formed on the surface of the glass substrate 1b so as to correspond to the respective pixels. The pixel electrode is connected to a TFT (Thin Film Transistor) formed on the surface of the glass substrate 1b. The TFT is connected to the IC chip formed on the COF 2 and is driven by the IC chip.

  The liquid crystal display panel 1 in the present embodiment is formed so that the planar shape is substantially rectangular. A connection terminal portion is formed at the end of one side of the planar rectangular shape of the glass substrate 1b. The glass substrate 1b is formed larger than the glass substrate 1a so that the connection terminal portion is exposed. The COF 2 in the present embodiment is formed so that the planar shape is substantially rectangular. The COF 2 is bonded and fixed to the connection terminal portion of the glass substrate 1b. The COFs 2 are arranged at substantially constant intervals.

  The thermocompression bonding apparatus in the present embodiment includes a stage for arranging a liquid crystal display panel on the surface (not shown). A film-like buffer material 13 is disposed above the stage, and the heating head 10 is disposed above the buffer material 13. The heating head 10 has a longitudinal direction and is formed so that a plurality of COFs 2 can be thermocompression bonded at a time.

  FIG. 2 is a schematic partial cross-sectional view of the thermocompression bonding apparatus as viewed from the side. An IC chip 4 is disposed in the COF 2. The tip of the heating head 10 is formed so that the cross-sectional shape is substantially rectangular, and is formed so that the COF 2 can be pressed planarly. The buffer material 13 is formed in a strip shape, and is sent in the longitudinal direction of the strip only by a predetermined length every time thermocompression bonding is performed several times to several tens of times. That is, it is formed so that a portion to which no pressure is applied can be used when performing thermocompression bonding. The buffer material 13 is supported by rollers 15 disposed on both sides of the heating head 10. The roller 15 is formed so as to be rotatable, and is formed so that the cushioning material 13 can be fed in the longitudinal direction.

  The liquid crystal display panel 1 is disposed so that the connection terminal portion of the glass substrate 1b to which the COF 2 is connected faces the heating head 10. The liquid crystal display panel 1 is fixed to a stage (not shown).

  The heating head 10 is formed to be movable as indicated by an arrow 31. In the present embodiment, it is formed to be movable in the vertical direction. When the heating head 10 moves in the direction indicated by the arrow 31, the COF 2 is pressed with the cushioning material 13 interposed therebetween. The COF 2 is bonded and fixed to the glass substrate 1b by the anisotropic conductive film 3.

  FIG. 3 shows a schematic partial cross-sectional view when the COF is bonded and fixed. First, the COF 2 is temporarily crimped while being aligned so that the wiring formed on the surface of the COF 2 film is electrically connected to the wiring formed on the surface of the glass substrate 1b. FIG. 3 shows a state after the temporary crimping of COF2. On the surface of the glass substrate 1b, the anisotropic conductive film 3 is disposed in a band shape, and on the surface of the anisotropic conductive film 3, COF 2 is disposed.

  A cushioning material 13 is disposed between the heating head 10 and the COF 2. In the present embodiment, the cushioning material 13 includes a silicon rubber sheet 11. The buffer material 13 includes a polyimide film 12 formed on the surface of the silicon rubber sheet 11 on the side facing the heating head 10. The buffer material 13 includes a glass cloth (not shown) disposed on the surface of the silicon rubber sheet 11 on the side facing the COF 2.

  The hardness and thickness of the silicon rubber sheet of the buffer material are not particularly limited, but the thickness of the silicon rubber sheet is preferably 0.15 mm or more and 0.4 mm or less, and the hardness is Hs40 or more and Hs90 or less. preferable.

  FIG. 4 shows a schematic partial cross-sectional view when performing the main pressure bonding in the COF 2 thermocompression bonding process. As shown by the arrow 32, the heating head 10 is lowered. As shown by an arrow 33, a pressing force is applied to the COF 2 toward the glass substrate 1b. The COF 2 is heated by the heating head 10. The COF 2 and the glass substrate 1b are bonded by an anisotropic conductive film. The conductive particles inside the anisotropic conductive film 3 are crushed, and the wiring formed on the COF 2 and the wiring formed on the connection terminal portion on the surface of the glass substrate 1b can be electrically connected.

  In the present embodiment, the downward thrust of the heating head 10 is calculated by the following formula.

(Descent thrust) = (COF width) × (COF crimping length) × (pressure required for crimping) × (number of COFs) + (total board space) × (COF crimping length) × (crimping) Required pressure) x (conversion factor) (2)
Here, the conversion coefficient is calculated by the following equation.

(Conversion factor) = (Pressure applied to the surface of the substrate between the COFs) / (Pressure applied to the surface of the COF) (3)
FIG. 5 shows a schematic plan view when a COF is connected to the liquid crystal display panel. In the present embodiment, the COF 2 is arranged so that one side of the COF 2 and the outer side of the glass substrate 1b are substantially parallel. With reference to FIGS. 1, 2, and 5, the width W of the COF 2 is the length of the COF 2 in the direction in which the COF 2 is arranged. The crimping length L1 of COF2 is the length in the direction perpendicular to the direction in which COF2 is arranged in the region where COF2 and glass substrate 1b are bonded. The total length L2 of the substrate is a length in a direction parallel to the direction in which the COF 2 is arranged in the substrate to which the COF 2 is attached.

  The total length of the space of the substrate is the total length of the portions where the COF is not arranged in the direction in which the COF is arranged, and is the length obtained by subtracting the total width of the COF from the total length of the substrate. In FIG. 5, the total length of the substrate space is the sum of the distance L3 between the COFs 2 and the length L4 from the end COF 2 to the end of the glass substrate 1b (the length L4 outside the region where the COF 2 is disposed). is there.

  In the conversion coefficient of Expression (3), the pressure applied to the surface of the COF and the pressure applied to the surface of the substrate between the COFs are obtained by actual measurement. In measuring the pressure applied to each surface, for example, pressure sensitive paper is used. Pressure-sensitive paper is placed on the surface of the COF and the surface of the substrate between the COFs, and is pressurized with a heating head, and each pressure is measured. By adopting this method, the conversion coefficient can be easily obtained. For example, in a state where the heating head is at room temperature, a descending thrust is obtained such that the pressure applied to the COF by pressure sensitive paper is 3 MPa. Next, the pressure applied to the surface of the glass substrate between the COFs under this condition is obtained with pressure sensitive paper. The conversion factor can be determined from the obtained pressure.

  The method of calculating the conversion coefficient is not limited to this form. For example, the conversion coefficient may be obtained by gradually changing the pressure for a plurality of samples and back-calculating from the descending thrust with the best connection state. Absent.

  In the present embodiment, the downward thrust of the heating head 10 is calculated using the above formulas (2) and (3). Compared with the formula (1) according to the conventional connection method, the second item of the formula (2) is added, so that the downward thrust is increased and the COF can be pressed with an optimum pressure. Thus, an appropriate downward thrust for pressing the COF can be obtained, and the COF can be reliably attached to a substrate such as a glass substrate.

  Also in the method using pressure sensitive paper, in the conventional technique, it is necessary to perform measurement using pressure sensitive paper every time the model is changed. However, in the connection method according to the present invention, even if the COF crimping length, the number of COFs, or the total length of the substrate are changed, the COF thickness, the buffer material, and the pressure necessary for crimping the COF are changed. As long as there is not, appropriate fall thrust can be easily calculated | required using Formula (2) and Formula (3). For this reason, it is not necessary to return the temperature of the heating head to room temperature, and productivity is improved.

  Normally, the COF thickness, cushioning material, or pressure required to connect the COF does not change for each model, so there is no need to obtain the above conversion factor for each model. The downward thrust of the heating head can be obtained. For this reason, when connecting and fixing a plurality of models, the manufacturing time is shortened, the productivity is improved, and the connection failure of COF can be prevented.

  Next, a COF was attached to the liquid crystal display panel, and a confirmation test for the reliability of the above formulas (2) and (3) was performed. The method for connecting the thermocompression bonding apparatus and the COF is the same as described above.

  Referring to FIG. 5, COF 2 having a width W of 40 mm and a thickness of 46 μm (base material is 38 μm and copper foil is 8 μm) was used. The crimping length L1 of COF2 was arranged to be 1.0 mm. In this test, two pieces of COF2 were attached to one glass substrate. The pressure required for pressure bonding of this COF2 is 3.0 MPa. As the liquid crystal display panel, a substrate having a total length L2 of 310 mm was used. The total length of the space at this time is 230 mm.

  As the buffer material, a laminate of a polyimide film having a thickness of 0.012 mm, a silicon rubber sheet having a thickness of 0.25 mm and a hardness of Hs70, and a glass cloth having a thickness of 0.04 mm was used.

  Under this condition, the heating head is pressed so that the pressure applied to the surface of the COF 2 becomes 3 MPa. At this time, the pressure applied to the surface of the COF 2 and the pressure applied to the surface of the glass substrate 1b are obtained. The conversion factor obtained from these measured pressures was 0.116.

  Therefore, when COF having a thickness of 46 μm and a cushioning material including a silicon rubber sheet having a thickness of 0.25 mm and a hardness of Hs70, the downward thrust of the heating head in thermocompression bonding is as follows: .

(Descent thrust) = (COF width) × (COF crimping length) × (pressure required for crimping) × (number of COFs) + (total board space) × (COF crimping length) × (crimping) Pressure required) x 0.116 (4)
Here, in order to examine the connection state of the present invention, the ACF particle diameter when TCP was connected to the glass substrate was measured using a conventional calculation formula shown in Formula (1). COF thermocompression bonding was performed with a downward thrust with the conversion coefficient changed little by little, and the particle size of the anisotropic conductive film at that time was measured. The ACF particles can be flattened when a pressure is applied to form conduction between opposing wirings. The test results are shown in Table 1.

  In Table 1, the diameter of the ACF particles indicates the longest diameter among the flat shapes in the cross-sectional shape. As shown in Table 1, when TCP connection was performed, the diameter of the ACF particles after connection was 4.8 μm. The diameter of the ACF particles when the COF was connected by the downward thrust when the conversion factor was 0.116 was 4.79 μm, and it was confirmed that it was almost the same as the particle size at the time of TCP connection. That is, by using the above formula (4), it was possible to press the anisotropic conductive film in substantially the same state as when the TCP was connected to the substrate, and the wirings could be reliably connected.

  In the present embodiment, the COF is disposed on the surface of the glass substrate. However, the present invention is not limited to this configuration, and the present invention can be applied in an attachment process for connecting the COF to the surface of an arbitrary substrate. In this embodiment mode, a liquid crystal display device is taken as an example of an electrical device. However, the present invention is not limited to this mode and can be applied to any electrical device.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic perspective view of the principal part of the thermocompression bonding apparatus in embodiment. It is a general | schematic fragmentary sectional view of the principal part of the thermocompression bonding apparatus in embodiment. It is a general | schematic fragmentary sectional view of the 1st process when performing thermocompression bonding in embodiment. It is a general | schematic fragmentary sectional view of the 2nd process when performing thermocompression bonding in embodiment. It is a schematic plan view when COF is attached to a liquid crystal display panel. It is a schematic sectional drawing when connecting TCP based on a prior art by thermocompression bonding. It is a schematic sectional drawing when connecting COF by thermocompression bonding.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Liquid crystal display panel, 1a, 1b Glass substrate, 2 COF, 3 Anisotropic conductive film, 4 IC chip, 5 TCP, 10 Heating head, 11 Silicon rubber sheet, 12 Polyimide film, 13, 14 Buffer material, 15 roller, 21 gap part, 31-33, 39,40 arrow, L1 crimping length (crimping length in a direction perpendicular to the width direction of COF), L2 total length of substrate, distance between L3 COFs, L4 COF are arranged The outer length of the region, the width of W COF.

Claims (2)

Including an attachment step of connecting the COF to the substrate via an anisotropic conductive film;
The attaching step includes a thermocompression bonding step in which a buffer material is sandwiched between the COF and a heating head, and the COF is pressed while being heated by the heating head,
The method of connecting COFs, wherein the thermocompression bonding step includes a step of pressing the heating head with a downward thrust obtained by the following equation.
(Descent thrust) = (COF width) × (COF crimping length) × (pressure required for crimping) × (number of COFs) + (total board space) × (COF crimping length) × (crimping) Required pressure) x (conversion factor)
Here, (conversion factor) = (pressure applied to the surface of the substrate between the COFs) / (pressure applied to the surface of the COF).   The COF connection method according to claim 1, wherein the conversion factor is obtained by measuring pressure using pressure sensitive paper.

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