JP4240474B2 - Thermocompression bonding apparatus and thermocompression bonding method - Google Patents

Description

The present invention relates to a technique for temporarily fixing an anisotropic conductive film (ACF = Anisotropic Conductive Film) to an electrode wiring surface formed on a flexible circuit board (FPC = Flexible Printed Circuit) by means of a thermocompression bonding means. about the thermocompression bonding device and thermocompression bonding how is utilized in the temporary fixing process.

  With the widespread use of mobile phones and personal digital assistants (PDAs), a display panel having a high-definition image display function and capable of realizing a thin shape and low power consumption has been demanded. It is used in many products as a display panel that satisfies this requirement. In recent years, organic EL (electroluminescence) display panels that take advantage of the characteristic of being self-luminous display elements have also been adopted in some electronic devices as described above, which replaces conventional liquid crystal display panels. It is attracting attention as a generation display panel.

  In such a display panel, a large number of data lines and a large number of scanning lines are arranged in a stripe pattern on a transparent substrate such as glass constituting the panel, and these data lines and scans are arranged. Display pixels are formed in a matrix, for example, at the intersections with the lines. The data lines and the scanning lines are connected to the flexible circuit board (hereinafter also referred to as FPC) at the orthogonal ends of the transparent substrate constituting the display panel, and are arranged in the FPC. It is configured to receive drive signals from a pixel driver data driver, a scan driver, and the like through the numerous electrode wirings.

  As described above, for example, an anisotropic conductive film (hereinafter also referred to as ACF) has been conventionally used as a means for connecting each electrode wiring in a flexible circuit board to a data line and a scanning line on a transparent substrate constituting a display panel. Means for connecting to each other by thermocompression bonding.

  This ACF is obtained by dispersing a large number of conductive particles in a thermoplastic or thermosetting resin film. When the thermocompression bonding head is brought into contact with a predetermined pressure, the conductive particles are connected between facing terminals. It exhibits electrical conductivity in a single direction, which allows conduction between terminals and mechanical connection. Therefore, the thermocompression bonding means using the ACF can be suitably used when a large number of terminals are connected together as described above.

  As described above, in order to thermocompression-bond an FPC to, for example, a data line or a scanning line on a transparent substrate constituting a display panel using the ACF, first, the ACF is temporarily fixed to the electrode wiring surface in the FPC. The process is executed. Next, the ACF temporarily fixed to the FPC is brought into contact with the data line or the scanning line on the transparent substrate, and the head is further thermocompression-bonded (main-compression bonding) from the back surface of the FPC. Thus, each electrode wiring in the FPC can be connected to the data line or the scanning line on the transparent substrate.

Patents already filed by the applicant of the present application for executing the process of temporarily fixing the ACF to, for example, the FPC and the process of permanently pressing the FPC to the display panel surface using the temporarily fixed ACF. It is disclosed in Document 1.
JP 2003-86999 A

  By the way, for example, the FPC circuit-connected to the substrate surface of the display panel through the ACF described above forms a copper stay pattern (electrode wiring) on a flexible film-like base member surface, and further thereon An insulating resist is applied. The region where the ACF is temporarily fixed is configured such that the electrode wiring is exposed without applying an insulating resist.

  FIG. 1 shows an example thereof, and shows an enlarged end portion of the FPC 1. Reference numeral 2 denotes a film-like base member constituting the FPC 1. On the base member 2, as shown by broken lines, electrode wirings 3 made of copper are formed in parallel with each other in a stripe shape, and a part of the surface on which the electrode wirings 3 are formed is excluded later. An insulating resist is further applied to the entire surface to form an insulating resist layer 4.

  A rectangular area surrounded by a chain line indicated by reference numeral 5 indicates an area where ACF (also indicated by reference numeral 5) is temporarily fixed, and the insulating resist layer 4 described above is in the area where ACF 5 is temporarily fixed. The portion of the electrode wiring 3 is an unformed (unpainted) portion of the resist layer. That is, the electrode wiring 3 is exposed in the hatched area indicated by reference numeral 3a. The exposed portion 3a of the electrode wiring is gold-plated 3b as necessary, as shown by hatching in white.

  As described above, the ACF 5 is temporarily fixed so as to cover the entire exposed portion 3a of the electrode wiring and also cover the portion provided with the insulating resist layer 4 in the periphery thereof. This is because stress tends to concentrate mechanically in the vicinity of the boundary portion of the insulating resist layer 4, and when a force such as repeated bending is applied, a crack or the like is likely to occur in this portion. Therefore, in order to avoid the above-described problem, the ACF 5 is fixed to a region that widely covers the formation position of the insulating resist layer 4 including the exposed portion 3 a of the electrode wiring 3.

  2 and 3 show how the ACF 5 is temporarily fixed to the FPC 1 having the configuration shown in FIG. That is, the FPC 1 in FIGS. 2 and 3 is shown in an enlarged cross-sectional view of a portion A shown in FIG. In FIGS. 2 and 3, parts corresponding to the parts shown in FIG.

  As shown in FIGS. 2 and 3, when the ACF 5 is temporarily fixed to the FPC 1, the FPC 1 is placed on the backup stage 10 that constitutes the thermocompression bonding apparatus. The backup stage 10 is made of a material that is relatively hard and has low thermal conductivity, and the mounting surface 10s of the circuit board is flat (planar). An ACF 5 is placed on the upper surface of the FPC 1 as shown in FIG. The placement position of the ACF 5 is placed so as to cover the formation position of the insulating resist layer 4 including the exposed portion 3a of the electrode wiring 3 as described above.

  In this case, since the resist layer 4 has a thickness as shown in FIG. 2, a step is generated between the exposed portion 3a of the electrode wiring and the resist layer 4, and this step portion has a back surface side of the ACF 5. A relatively large space 13a is generated. Then, as shown in FIG. 2, the thermocompression bonding head 11 constituting the thermocompression bonding apparatus descends to heat the ACF 5 and press-contact it to the FPC 1 side. As a result, the resin material constituting the ACF 5 is thermally deformed, and the ACF 5 is temporarily fixed on the FPC 1. Then, as shown in FIG. 3, the thermocompression bonding head 11 is raised and the process of temporarily fixing the ACF 5 to the FPC 1 is completed.

  In the state where the ACF 5 is temporarily fixed to the FPC 1, the back side of the ACF 5 is still sealed due to the presence of a step between the exposed portion 3a of the electrode wiring and the resist layer 4 as shown in FIG. There arises a problem that the space 13b is left. The air left in the sealed space 13b expands by receiving heat from the thermocompression bonding head during the subsequent main pressure bonding, and makes an electrical connection with the exposed portion 3a of the electrode wiring. The problem of alienation will occur.

  In order to avoid the above-described problem, for example, it is conceivable to create an air escape pattern in the insulating resist layer 4 in advance. However, since the resist layer 4 is generally formed by screen printing, an error of about 0.3 mm occurs, and it is difficult to form a fine air escape pattern corresponding to a fine pitch electrode terminal. Although it is possible to create a fine air escape pattern on the resist layer 4 by avoiding screen printing and using a mask, the process for this is complicated and costly, which is not practical.

  The present invention has been made paying attention to the above-described problems, and in the step of temporarily fixing the anisotropic conductive film to the flexible circuit board, a sealed space is provided between the circuit board and the anisotropic conductive film. It is an object of the present invention to provide a thermocompression bonding apparatus and a thermocompression bonding method that can greatly reduce the degree of formation of a flexible circuit board with improved electrical reliability, and a It is intended to provide onboard electronic equipment.

The thermocompression bonding apparatus according to the present invention, which has been made in order to solve the above-described problem, further includes a backup stage on which a flexible circuit board is placed and an electrode wiring surface of the flexible circuit board. A thermocompression bonding apparatus comprising a thermocompression bonding head that abuts on the mounted anisotropic conductive film, wherein electrode wiring in the flexible circuit board is formed on a part of the mounting surface of the flexible circuit board in the backup stage. for a boundary portion between the exposed portion and the insulating resist layer is disposed of, the with a recess having a thickness 20-100% of the depth of the film-shaped base member in the flexible circuit board, the recess, the flexible It is configured so that the end portion of the circuit board enters the flexi from the recess formed in the backup stage Boundary portions raised the mounting surface of Le circuit board, characterized in that it is made in the inclined surface of greater than 90 degrees to the plane of the recess.

Moreover, the thermocompression bonding method according to the present invention made to solve the above-described problems is the electrode wiring surface formed on the flexible circuit board using the thermocompression bonding apparatus having the above-described configuration, as described in claim 4. A method of temporarily fixing an anisotropic conductive film to the flexible circuit board, wherein the flexible circuit board includes a film-like base member, an electrode wiring arranged on the base member, and a part of the electrode wiring. It further comprises a configuration in which an insulating resist layer is laminated so as to be exposed, and a boundary portion between the exposed portion of the electrode wiring and the insulating resist layer is disposed at a position where the concave portion is formed in the backup stage, and The exposed portion of the electrode wiring is disposed on the mounting surface of the flexible circuit board in the backup stage, and the boundary between the exposed portion of the electrode wiring and the insulating resist layer An anisotropic conductive film is placed so as to cover the entire surface of the exposed portion of the electrode wiring including, and a thermocompression bonding head is brought into contact with the anisotropic conductive film to make a difference with respect to the flexible circuit board. It is characterized in that the isotropic conductive film is temporarily fixed.

  Hereinafter, a thermocompression bonding apparatus and a thermocompression bonding method using the same according to the present invention will be described based on embodiments shown in FIG. In the thermocompression bonding apparatus and thermocompression bonding method according to the present invention described below, the FPC having the form shown in FIG. 1 is used. Accordingly, portions corresponding to the respective portions shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate.

  4 and 5 show a first embodiment of the thermocompression bonding apparatus according to the present invention. In the backup stage 10 employed in this thermocompression bonding apparatus, one of the mounting surfaces 10s of the flexible circuit board is shown. A recess 14 is formed in the part. When temporarily fixing the ACF 5 to the FPC 1, first, the boundary portion between the exposed portion 3 a of the electrode wiring in the FPC 1 and the insulating resist layer 4 is disposed at the formation position of the recess 14 in the backup stage 10, and the electrode The exposed portion 3a of the wiring is positioned on the FPC placement surface 10s in the backup stage.

  By placing the FPC 1 on the backup stage 10 in this manner, the end portion of the FPC 1 enters the recess 14 formed in the backup stage 10 as shown in FIG. That is, the film-like base member 2 and the electrode wiring 3 constituting the FPC 1 are relatively flexible, and are brought into the state shown in FIG. 4 by their own weight. Therefore, the insulating resist layer 4 laminated on the end portion of the FPC 1 is also deformed as shown in FIG. 4, and the step formed between the insulating resist layer 4 and the exposed portion 3a of the electrode wiring is as shown in FIG. Compared to the example shown in (1), it is very small.

  When the ACF 5 is placed in this state as shown in FIG. 4, the space 13c formed on the back side of the ACF 5 becomes very small. Therefore, as shown in FIG. 5, when the ACF 5 is heated and pressed by the thermocompression bonding head 11 in this state, the ACF 5 is temporarily placed on the upper surface of the FPC 1 with almost no air remaining on the back side of the ACF 5. Can be fixed. As a result, even when the FPC 1 temporarily fixed with the ACF 5 is subjected to main pressure bonding to another substrate such as a display panel, the above-described problem caused by air accumulation existing on the back side of the ACF 5 can be avoided. it can.

  FIG. 6 is an enlarged view of a part of the backup stage 10 described above, which shows C and D portions surrounded by a broken line in FIG. The backup stage 10 is configured by superposing a plate-like auxiliary body 10b on a planar stage main body 10a, and the upper surface of the auxiliary body 10b is formed as an FPC mounting surface 10s. And the said recessed part 14 is formed in the non-polymerization part of an auxiliary body, ie, the part in which the auxiliary body 10b is not superposed | polymerized.

  An inclined surface 10c having an angle α exceeding 90 degrees with respect to the surface of the concave portion 14 is formed at the boundary portion that rises from the concave portion 14 to the mounting surface 10s of the FPC. In the example shown in FIG. 6, the α is about 130 degrees. This is because when the α is in an overhang state of 90 degrees or less, the FPC 1 is very damaged due to the contact pressure of the thermocompression bonding head 11, whereas This is because the degree to which the FPC 1 is damaged is very small when it is formed on the inclined surface 10c having the angle α.

  On the other hand, the depth of the recess 14 formed in the backup stage 10, in other words, in this embodiment, the thickness 10d of the auxiliary body 10b polymerized with respect to the stage body 10a is the film constituting the FPC 1. The thickness of the base member 2 is preferably in the range of 20 to 100%. This is because the degree of the effect obtained by providing the recess 14 is small when the depth of the recess 14 is shallower than the above numerical value.

  When the depth of the concave portion 14 is deeper than the above numerical value, the degree of deformation of the FPC 1 toward the concave portion 14 at the time of pressure bonding by the thermocompression bonding head 11 is increased, and defective thermocompression bonding occurs in part. Further, when the depth of the concave portion 14 is deeper than the above numerical value, another problem of causing the cutting of the electrode wiring 3 arranged in the FPC 1 occurs when receiving the contact pressure of the thermocompression bonding head 11. .

  As an example, the FPC 1 in which the thickness of the film-like base member 2 constituting the FPC 1 described above is 25 μm, the thickness of the electrode wiring 3 is 12 μm, and the thickness of the insulating resist layer 4 is 5 to 25 μm is used as a sample. FIG. 8 shows experimental data for determining the preferred depth of the recess 14 formed in the above. Note that the thickness of the insulating resist layer 4 has a width as described above, because the resist layer 4 is formed by printing, so that considerable variation occurs in one substrate.

The experimental data shown in FIG. 8 shows the result of obtaining the relationship of the non-defective product rate (%) of thermocompression bonding to the depth (%) of the recess 14 with respect to the thickness of the base member 2 constituting the FPC 1. . As can be understood from the data shown in FIG. 8, it is particularly preferable to provide the recess 14 having a depth of 30 to 100% of the thickness of the base member in the FPC, and practically a depth of 20 to 100%. It is desirable to have a recess 14 having That is, the thickness of the base member 2 in this case is 25 μm as described above, and the concave portion 14 having a depth of 20 to 100% of the thickness of the base member 2 is substantially 5 to 25 μm deep. Will have.

  FIG. 7 is a sectional view showing a second embodiment of the thermocompression bonding apparatus according to the present invention, which corresponds to FIG. 4 showing the first embodiment already described. . In the second embodiment shown in FIG. 7, a plurality of suction holes 16 are formed in the recess 14 formed in the backup stage 10. Thereby, the back surface of the FPC 1 placed on the backup stage 10 can be sucked and fixed to the concave portion 14 side.

  Therefore, according to the form of the backup stage 10 constituting the thermocompression bonding apparatus shown in FIG. 7, the back surface of the FPC 1 acts so as to be sucked by the negative pressure to the concave portion 14 side. Therefore, when the ACF 5 is placed on the FPC 1, The volume of the space 13c formed on the back side of the ACF 5 can be further reduced. Thereby, when the ACF 5 is temporarily fixed on the FPC 1 by heat-pressing with the thermocompression bonding head 11, the probability that air remains between the FPC 1 and the ACF 5 can be further reduced.

  The embodiment shown in FIGS. 4 to 7 described above shows a partial configuration of a thermocompression bonding apparatus that processes the end portion of the flexible circuit board 1 shown in FIG. 1, that is, the portion A of the flexible circuit board shown in FIG. Yes. However, the B portion shown in FIG. 1 has the same problem as described above. Therefore, the similar recess 14 is formed in the backup stage for processing the B portion shown in FIG.

  According to the flexible circuit board in which the anisotropic conductive film is thermocompression-bonded by employing the thermocompression bonding apparatus and the thermocompression bonding method according to the present invention, the degree to which a sealed space is formed between the circuit board and the anisotropic conductive film Therefore, it is possible to provide a flexible circuit board with improved electrical reliability and an electronic device equipped with the flexible circuit board.

  As for the electronic apparatus using the flexible circuit board described above, the display panel of the display is given as an example in the background art section, but the present invention is not only applied to the specific one as described above. In addition, it can be used for the connection between the bump and the flexible circuit board in the semiconductor integrated circuit, the connection between the same flexible circuit boards, etc., and can contribute to the improvement of the reliability in the electronic apparatus using these. .

It is a top view explaining the structure of the edge part of FPC, and the position which fixes ACF temporarily. It is sectional drawing explaining the condition which temporarily fixes ACF to FPC in the conventional thermocompression bonding apparatus. It is a sectional view explaining the situation where temporary fixation ended similarly. It is sectional drawing explaining the condition which temporarily fixes ACF to FPC in 1st Embodiment of the thermocompression-bonding apparatus concerning this invention. It is a sectional view explaining the situation where temporary fixation ended similarly. It is sectional drawing which expanded and showed the C and D part in FIG. It is sectional drawing explaining the condition which temporarily fixes ACF to FPC in 2nd Embodiment of the thermocompression-bonding apparatus concerning this invention. It is a figure which shows the experimental result which calculated | required the preferable depth of the recessed part formed in the backup stage in the thermocompression bonding apparatus concerning this invention.

Explanation of symbols

1 Flexible circuit board (FPC)
2 Base member 3 Electrode wiring 3a Exposed portion of electrode wiring 3b Gold-plated portion 4 Insulating resist layer 5 Anisotropic conductive film (ACF)
10 Backup stage (thermocompression bonding equipment)
10a Stage body 10b Auxiliary body 10c Inclined surface 10s Mounting surface of circuit board (FPC) 11 Thermocompression bonding head (thermocompression bonding apparatus)
13a to 13c space 14 recess 16 suction hole

Claims (5)

A thermocompression bonding apparatus comprising a backup stage for mounting a flexible circuit board, and a thermocompression bonding head that contacts an anisotropic conductive film further mounted on the electrode wiring surface of the flexible circuit board,
In the part of the mounting surface of the flexible circuit board in the backup stage , a boundary between the exposed portion of the electrode wiring and the insulating resist layer in the flexible circuit board is disposed, and the film shape in the flexible circuit board Comprising a recess having a depth of 20 to 100% of the thickness of the base member ;
The recess is configured such that an end of the flexible circuit board enters,
The thermocompression bonding apparatus characterized in that a boundary portion rising from the concave portion formed on the backup stage to the mounting surface of the flexible circuit board is an inclined surface exceeding 90 degrees with respect to the surface of the concave portion. The backup stage is configured by superimposing a plate-like auxiliary body on a planar stage main body, the upper surface of the auxiliary body is made a mounting surface of the flexible circuit board, and the non-polymerized portion of the auxiliary body is The thermocompression bonding apparatus according to claim 1, wherein the recess is formed. 3. The thermocompression bonding apparatus according to claim 1, wherein a suction hole capable of sucking a part of the flexible circuit board is formed in the recess formed in the backup stage. . A thermocompression bonding method for temporarily fixing an anisotropic conductive film to an electrode wiring surface formed on a flexible circuit board using the thermocompression bonding apparatus according to any one of claims 1 to 3. The flexible circuit board comprises a film-like base member, an electrode wiring arranged on the base member, and a structure in which an insulating resist layer is further laminated so as to expose a part of the electrode wiring. ,
A boundary portion between the exposed portion of the electrode wiring and the insulating resist layer is disposed at a position where the concave portion is formed in the backup stage, and the exposed portion of the electrode wiring is disposed on a mounting surface of the flexible circuit board in the backup stage. As well as
An anisotropic conductive film is placed so as to cover the entire surface of the exposed portion of the electrode wiring including the boundary portion between the exposed portion of the electrode wiring and the insulating resist layer, and a thermocompression bonding head is applied to the anisotropic conductive film. A thermocompression bonding method characterized in that an anisotropic conductive film is temporarily fixed to the flexible circuit board by contacting the substrate. By sucking air from the suction holes formed in the recesses in the backup stage, the flexible circuit board disposed in the recesses is sucked and fixed to the backup stage, and is anisotropic with respect to the flexible circuit boards in the suction-fixed state. The thermocompression bonding method according to claim 4 , wherein the conductive film is temporarily fixed by the thermocompression bonding head.

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