JP2013008792A - Method of processing flexible substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method that eliminates the needs of setting bending conditions and newly producing a bending device when a specification of a substrate is changed, and realizes high-quality bending.SOLUTION: A processing method of a flexible substrate for bending a COF substrate at an arbitrary angle includes: a step S1 that is a bending property examination step for examining, on the basis of a cross-sectional area ratio between a base material and wirings of the COF substrate, the relationship between the cross-sectional area ratio and a bending angle of the flexible substrate; a step S2 that is a cross-sectional area ratio determination step for determining the cross-sectional area ratio of the COF substrate; and a step S3 that is a designing step for designing the COF substrate having the cross-sectional area ratio corresponding to the bending angle.

Description

  The present invention relates to a method for processing a flexible circuit board, and particularly relates to a bending process for a flexible circuit board.

  A flexible substrate may be used by making use of its characteristics and folding the substrate at an arbitrary angle so as to be compactly incorporated in a housing or the like of an electronic device. In electronic devices, performance is often improved by changing an internal circuit board or the like while using the same housing.

  When a flexible substrate is bent to a desired angle, a bending method and an apparatus are studied for each substrate, and a desired bending angle is realized by matching conditions. Therefore, it is necessary to set the folding conditions every time the substrate specifications change, and it is sometimes necessary to create a new bending apparatus.

  On the other hand, as a method of bending a flexible substrate, as disclosed in Patent Document 1, a method of relaxing stress applied to a bent portion when a flexible substrate is bent is disclosed. According to this, the protective layer inside the place to be bent was removed, and the bent portion was further reinforced with an adhesive. This provided a high stress structure. Patent Document 2 discloses a flexible substrate bending apparatus. According to this, the apparatus was bending with the jig | tool, heating the bending part of a board | substrate.

JP 2005-340401 A JP 2005-96408 A

  However, the method for bending a flexible substrate described in Patent Document 1 requires steps such as removal of the protective layer of the flexible substrate and application of an adhesive. Furthermore, since additional members are required, there are problems such as a decrease in yield and an increase in cost. Moreover, in the bending apparatus of the flexible substrate described in Patent Document 2, it is necessary to add a heating mechanism to the processing apparatus, and there is a problem that the apparatus configuration becomes complicated. Further, since the bent portion is heated, there is a problem that the heated portion melts and the pattern is exposed depending on the material of the base material and the protective layer.

  Therefore, there has been a demand for a processing method that does not require bending conditions every time the substrate specifications change and does not create a new bending apparatus, and a processing method that realizes high-quality bending.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A flexible substrate processing method according to this application example is a flexible substrate processing method for bending a flexible substrate on which wiring is installed, and a ratio of a cross-sectional area of the flexible substrate to a cross-sectional area of the wiring. Is a cross-sectional area ratio, a bendability investigation step for examining bendability indicating the relationship between the cross-sectional area ratio and the bend angle of the flexible substrate, and a cross-sectional area ratio for determining the cross-sectional area ratio corresponding to the predetermined bend angle. And a design process for designing the flexible substrate having the determined cross-sectional area ratio.

  According to this application example, the bendability indicating the relationship between the cross-sectional area ratio and the bend angle of the flexible substrate is examined in the bendability investigation step. In this step, the bending characteristics of the flexible substrate are evaluated. From the evaluation results, the relationship between the cross-sectional area ratio and the bending characteristics under each condition of the base material, the wiring, and the bending becomes clear. Next, in the cross-sectional area ratio determining step, a cross-sectional area ratio corresponding to a predetermined bending angle is determined. In the design process, a flexible substrate having the cross-sectional area ratio determined in the cross-sectional area ratio determining process is designed.

  The cross-sectional area ratio at which a desired bending angle is obtained is determined from the relationship between the cross-sectional area ratio and the bending characteristics. And the flexible substrate of the determined cross-sectional area ratio is designed. By bending the flexible substrate under the designed conditions, it is possible to obtain a flexible substrate bent with high quality at a desired bending angle.

  Even when the specifications such as the number of wirings of the flexible substrate and the substrate width are changed, the desired bending angle can be realized with high quality without changing the bending conditions by designing the substrate so as to have a cross-sectional area ratio.

FIG. 2 is a schematic exploded perspective view showing a configuration of an inkjet head. FIG. 3 is a schematic side sectional view showing the structure of an inkjet head. The schematic diagram for demonstrating the bending of a COF board | substrate. The schematic front view which shows the structure of the bending apparatus of a flexible substrate. The schematic side view which shows the structure of the bending apparatus of a flexible substrate. The flowchart which shows the manufacturing process which bends a flexible substrate. The schematic diagram for demonstrating the processing method of a flexible substrate. The figure for demonstrating the processing method of a flexible substrate. The figure for demonstrating the processing method of a flexible substrate. The flowchart which shows a design process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale of each layer and each member is made different from the actual scale so that each layer and each member can be recognized.

(Embodiment 1)
First, a flexible substrate and a bending method of the flexible substrate will be described. This bending method is used for bonding a COF substrate (Chip on Film) on which a drive circuit for driving a piezoelectric element is mounted to an electrode portion of a plate-like member, for example, in the manufacture of an ink jet printer as a printing apparatus. The COF substrate is bent at a predetermined angle (90 °). Therefore, the configuration of the inkjet head will be briefly described.

  FIG. 1 is a schematic exploded perspective view showing the configuration of the inkjet head. FIG. 2 is a schematic side sectional view showing the structure of the inkjet head. As shown in FIG. 1 and FIG. 2, the inkjet head 1 is configured by stacking a nozzle plate 11, a flow path forming substrate 12, a protective substrate 13, a seal substrate 14, and a head case 15 in this order. A head substrate 2 is incorporated in the inkjet head 1 so as to penetrate the head case 15 and the protective substrate 13 and to stand on the flow path forming substrate 12. The head substrate 2 is formed by bonding a pair of COF substrates 22 on which a drive circuit 25 for driving the piezoelectric element 19 is mounted to both side surfaces of the base plate 21, and wiring in a lower bent portion of the pair of COF substrates 22. The conduction portion 27 is electrically connected to the lead electrode 18 on the flow path forming substrate 12.

  The nozzle plate 11 is made of, for example, stainless steel, and is bonded to one surface of the flow path forming substrate 12 with an adhesive or the like. In addition, a plurality of discharge nozzles 16 are formed at an equal pitch on the nozzle surface, which is one surface of the nozzle plate 11, and the plurality of discharge nozzles 16 are, for example, two rows arranged in parallel to each other. The nozzle row is configured.

  In the flow path forming substrate 12, a plurality of pressure chambers 11 a partitioned by partition walls are arranged in parallel in two rows in the width direction so as to correspond to the plurality of discharge nozzles 16. A common chamber 17 for storing functional liquid supplied from a functional liquid supply device (not shown) is formed in a region outside the longitudinal direction of the flow path forming substrate 12. And each pressure chamber 11a and the common chamber 17 are each connected via the supply path 11b. The common chamber 17 is installed through the protective substrate 13 and receives the supply of the functional liquid from the functional liquid supply device through the functional liquid inlet 14 a provided in the head case 15.

  The protective substrate 13 is connected to the flow path forming substrate 12 via the elastic film 12a and the insulator film 12b in this order from the flow path forming substrate 12 side. A number of piezoelectric elements 19 corresponding to the plurality of pressure chambers 11a are formed on the insulator film 12b. The protective substrate 13 is formed with a through hole 12c penetrating in the thickness direction. Further, a mechanism portion 12 d for accommodating each piezoelectric element 19 is recessed inside the protective substrate 13. One end of a lead electrode 18 is connected to each piezoelectric element 19, and the other end of the lead electrode 18 extends so as to be exposed in the through hole 12 c. The other end portion of the lead electrode 18 is connected to the conduction portion 27 of the COF substrate 22 located on the head substrate 2 described above. Then, by applying a voltage to the piezoelectric element 19 to deform the insulator film 12b and the elastic film 12a, the function chamber is introduced from the common chamber 17 by changing the volume of the pressure chamber 11a and functions from the discharge nozzle 16. The liquid is discharged as droplets.

  The head case 15 is connected to the protective substrate 13 via a sealing substrate 14 including a sealing film 13a and a fixing plate 13b in this order from the protective substrate 13 side. The common chamber 17 is sealed only by the sealing film 13a. The head case 15 is provided with a head substrate holding hole 14b communicating with a through hole 12c provided in the protective substrate 13. The head substrate 2 is inserted into the head substrate holding hole 14b and is made of an anisotropic conductive paste. The lead electrode 18 is connected via an adhesive.

  The head substrate 2 includes a base plate 21 that is a plate member made of stainless steel and a pair of COF substrates 22 that are attached to both side surfaces of the base plate 21 with a double-sided adhesive tape 23. Each COF substrate 22 includes a drive circuit 25, a substrate body 26 as a flexible base material, and a conduction portion 27. The substrate body 26 is flat and has a drive circuit 25 mounted thereon. The drive circuit 25 is a circuit that drives the piezoelectric element 19. The substrate body 26 is bonded to the base plate 21. The conductive portion 27 is bent from the board body 26 in an “L” shape.

  The pair of COF substrates 22 affixed to both side surfaces of the base plate 21 are arranged so that the leading end portions of the conducting portions 27 face inward. And the front-end | tip part of the conduction | electrical_connection part 27 is arrange | positioned so that the lower end surface of the baseplate 21 may be followed. The base plate 21 is abutted on the flow path forming substrate 12 with the front end portion of each COF substrate 22 facing down. In this state, the pair of COF substrates 22 are interposed via an adhesive that is an anisotropic conductive paste. The lead electrode 18 is connected.

  FIG. 3 is a schematic diagram for explaining bending of the COF substrate. FIG. 3A is a schematic plan view showing the COF substrate before bending. FIG. 3B is a schematic side view showing the COF substrate before bending. FIG. 3C is a main part schematic enlarged view showing the COF substrate before bending, and is an enlarged view of the conduction part. FIG. 3D is a schematic plan view showing the COF substrate after bending, and FIG. 3E is a schematic side view showing the COF substrate after bending. FIG. 3F is a main part schematic enlarged view showing the COF substrate after bending, and is an enlarged view of the conduction part.

  As shown in FIGS. 3A to 3C, the COF substrate 22 is formed flat before being bent, and conductive portions 27 are arranged on one surface of the substrate body 26. As shown in FIGS. 3D to 3E, after bending, the substrate body 26 and the conductive portion 27 of the COF substrate 22 are bent in an L shape at the bent portion 22a. For example, in the present embodiment, about 0.5 mm of the tip end portion of the COF substrate 22 is plastically deformed to 90 ° with high accuracy.

  FIG. 4 is a schematic front view showing the configuration of the flexible substrate bending apparatus. FIG. 5 is a schematic side view showing the configuration of the flexible substrate bending apparatus. As shown in FIGS. 4 and 5, the bending apparatus 3 includes a bending die 31 that holds the COF substrate 22. The bending die 31 includes a fixing part 35 and a pressing part 36. The COF substrate 22 is sandwiched and fixed between the fixing portion 35 and the pressing portion 36. The bending die 31 has the COF substrate 22 disposed so that the conductive portion 27 protrudes downward in the drawing. And the conduction | electrical_connection part 27 side of the fixing | fixed part 35 is formed in the acute angle.

  The bending device 3 includes a bending mechanism 32 on the lower side of the bending die 31 in the figure. The bending mechanism unit 32 includes a head unit 33 and a bending operation mechanism 34 that moves the head unit 33. The head unit 33 includes a bending roller 37 and a support portion 38 that supports the bending roller 37. The bending roller 37 has a cylindrical shape, and the rotation shaft of the bending roller 37 is supported by the support portion 38. The axial direction of the bending roller 37 is the direction in which the bent portion 22a extends, and this direction is the X direction.

  The bending operation mechanism 34 includes a first linear motion mechanism 49 and a second linear motion mechanism 51. When the thickness direction of the COF substrate 22 is the Y direction, the second linear motion mechanism 51 is a mechanism that moves the head unit 33 in the Y direction. When the direction orthogonal to the X direction and the Y direction is the Z direction, the Z direction is the longitudinal direction of the conducting portion 27. The first linear motion mechanism 49 is a mechanism that moves the head unit 33 in the Z direction. The bending operation mechanism 34 includes a pressing spring 56. The pressing spring 56 urges the head unit 33 in a direction approaching the bending die 31 in the Z direction.

  When bending the conduction portion 27, the bending device 3 drives the first linear motion mechanism 49 to separate the head unit 33 from the bending die 31 and drives the second linear motion mechanism 51 to cause the head unit 33 to be connected to the conduction portion 27. With respect to the holding part 36 side. Next, the bending device 3 drives the first linear motion mechanism 49 to bring the head unit 33 closer to the pressing portion 36. Subsequently, the bending device 3 moves the head unit 33 toward the fixed portion 35 with respect to the conducting portion 27.

  At this time, the bending roller 37 moves while pressing the substrate body 26 by the pressing spring 56. As a result, the conduction portion 27 of the substrate body 26 is pressed against the fixing portion 35, and the substrate body 26 is pushed and bent along the fixing portion 35. Next, the bending device 3 drives the first linear motion mechanism 49 to separate the head unit 33 from the COF substrate 22. As a result, the COF substrate 22 is bent at the bent portion 22a.

  From here, the processing method of a flexible substrate is demonstrated. FIG. 6 is a flowchart showing a manufacturing process for bending the flexible substrate. Step S1 corresponds to a bendability investigation step, and is a step of investigating the relationship between the cross-sectional area ratio between the substrate and the wiring and the bendability. Next, the process proceeds to step S2. Step S2 corresponds to a cross-sectional area ratio determining step, and is a step of determining the cross-sectional area ratio of the flexible substrate. Next, the process proceeds to step S3. Step S3 corresponds to a design process and is a process for designing a flexible substrate having a determined cross-sectional area ratio. Next, the process proceeds to step S4. Step S4 corresponds to a bending process and is a process of bending the flexible substrate. The manufacturing process of bending the flexible substrate is completed by the above process.

  7-10 is a figure for demonstrating the processing method of a flexible substrate. Next, the manufacturing method will be described in detail with reference to FIGS. 7 to 10 in association with the steps shown in FIG. 7 and 8 are diagrams corresponding to the bendability investigation step of step S1. As shown in FIG. 7, in step S <b> 1, the cross-sectional area in the direction in which the conductive portions 27 are arranged in the COF substrate 22, that is, the direction in which the bent portions 22 a are to be extended, is defined as the base material cross-sectional area 102. Next, let the cross-sectional area of the conduction | electrical_connection part 27 of the direction where the bending part 22a extends be the wiring cross-sectional area 101. FIG. Next, the ratio of the substrate cross-sectional area 102 and the wiring cross-sectional area 101 is taken as the cross-sectional area ratio.

  The base material and wiring material of the COF substrate 22 are determined in advance. The substrate body 26 is not particularly limited as long as it is a flexible material. In the present embodiment, for example, a polyimide resin is used. The material of the conductive portion 27 is not particularly limited as long as it has good electrical conductivity and is resistant to corrosion. In the present embodiment, for example, Cu plated with Au is used as a wiring material for the conductive portion 27.

  At least two or more levels of flexible substrates having different cross-sectional area ratios are prepared using the substrate body 26 and the wiring material. These flexible substrates are bent using the bending apparatus 3, and the relationship between the cross-sectional area ratio 100 and the bending angle 103 is investigated. As shown in FIG. 8, the horizontal axis is a cross-sectional area ratio of 100. In the cross-sectional area ratio 100, the right side in the figure is larger than the left side. The vertical axis shows the bending angle 103 of the flexible substrate, and the upper side in the figure is larger than the lower side. And the bending angle 103 is measured about the flexible substrate from which cross-sectional area ratio 100 differs. Next, the measurement data of the cross-sectional area ratio 100 and the bending angle 103 are plotted, and a correlation line 104 indicating the relationship between the cross-sectional area ratio 100 of the flexible substrate and the bending angle 103 is calculated. It should be noted that step S1 may be omitted from step S2 for the flexible substrate for which the correlation line 104 has already been calculated.

  FIG. 9 is a diagram corresponding to the cross-sectional area ratio determining step in step S2. As shown in FIG. 9, in step S2, a target bending angle 103a is set. Next, the cross-sectional area ratio setting value 100a corresponding to the target bending angle 103a is calculated using the correlation line 104.

  If the desired bending angle 103 is not within the range of the correlation line 104, a flexible substrate having a different cross-sectional area ratio 100 is prepared and the relationship between the cross-sectional area ratio 100 and the bending angle 103 is investigated. Alternatively, the bending condition of the bending apparatus is changed, and the condition is investigated so that a desired bending angle 103 is obtained within the range of the investigated cross-sectional area.

FIG. 10 is a flowchart showing the design process of step S3. The flexible substrate design process will be described with reference to FIG.
Step S11 corresponds to a constraint condition setting step. This step is a step of determining the constraint conditions for the flexible substrate design. For example, the number of wirings to be bent and the width of the substrate are determined. Next, the process proceeds to step S12. Step S12 corresponds to a wiring pitch calculation step. This step is a step of calculating the pitch of the wiring from the constraint conditions of the flexible substrate design. Next, the process proceeds to step S13.

  Step S13 corresponds to a wiring L / S temporary setting step. This step is a step of temporarily setting L / S (line / space) of the wiring. The “L” line indicates the width of the wiring, and the “S” space is the width between adjacent wirings. In other words, the width of the wiring at the calculated pitch and the width between the wirings are temporarily set. Next, the process proceeds to step S14. Step S14 corresponds to a wiring thickness setting step. This step is a step of setting the wiring thickness that can be processed with the temporarily set L / S. Next, the process proceeds to step S15.

  Step S15 corresponds to a workability determination step, and is a step of determining whether wiring can be processed. When it is determined that the processing cannot be performed, the process proceeds to step S13. Then, L / S is re-determined to determine the wiring thickness. When it is determined that machining can be performed, the process proceeds to step S16. Step S16 corresponds to a substrate thickness setting step. This step is a step of determining the base material thickness of the substrate body 26 using the cross-sectional area ratio 100 set in step S2, the set L / S, and the wiring thickness. The design process of step S3 is completed by the above process.

  In the bending step of step S4, the COF substrate 22 is bent using the bending device 3. At this time, since the processing conditions are set in advance, the COF substrate 22 can be bent with high accuracy. With the above process, the manufacturing process for bending the flexible substrate is completed.

  As described above, according to the method for bending a flexible substrate according to the present embodiment, the following effects can be obtained. That is, it is not necessary to remove the protective layer from the flexible substrate or to apply an adhesive. Thereby, the COF substrate 22 can be processed without complicating the process. Furthermore, since an additional member is not required, it can be manufactured with high productivity and high productivity. Further, since it is not necessary to add a heating mechanism to the processing apparatus, it is possible to prevent the problem that the apparatus becomes expensive. Furthermore, it is possible to solve the problem of inclusion in which the substrate and the protective layer are melted by heating the bent portion and the pattern is exposed.

  In the present embodiment, it is not necessary to set the bending condition every time the specifications of the substrate change. In addition, it is possible to provide a method for easily realizing equivalent bending without newly manufacturing a bending apparatus.

In addition, this embodiment is not limited to embodiment mentioned above, A various change and improvement can also be added. A modification will be described below.
(Modification 1)
In the first embodiment, the cross-sectional area ratio 100 corresponding to the bending angle 103 is calculated using the correlation line 104. Instead of the correlation line 104, a table indicating the relationship between the bending angle 103 and the cross-sectional area ratio 100 may be used. Even when the correlation line 104 has a non-linear relationship, the relationship between the bending angle 103 and the cross-sectional area ratio 100 can be accurately shown. Therefore, the cross-sectional area ratio 100 can be calculated with high accuracy.

  26 ... Substrate body as flexible base material, 27 ... Conducting portion as wiring, 100 ... Cross-sectional area ratio, 103 ... Bending angle.

Claims (1)

A flexible substrate processing method for bending a flexible substrate on which wiring is installed,
The ratio of the cross-sectional area of the flexible substrate and the cross-sectional area of the wiring as a cross-sectional area ratio, and a bendability investigation step of examining the bendability indicating the relationship between the cross-sectional area ratio and the bending angle of the flexible substrate;
A cross-sectional area ratio determining step for determining the cross-sectional area ratio corresponding to the predetermined bending angle;
And a design step of designing the flexible substrate having the determined cross-sectional area ratio.

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