JP2009004710A - Flexible substrate on which electronic components are mounted and recording apparatus including the same - Google Patents

Abstract

An underfill resin 57 that seals the outer periphery of a circuit element 50 starts to peel off at a corner portion outside a corner 50a of the circuit element 50 when a flexible substrate 23 on which the circuit element 50 is mounted is bent. To prevent.
A solder resist film covering a wiring pattern is formed on a base substrate of a flexible substrate on the outer peripheral side of a mounting region of a circuit element. The first opening 55 in the solder resist film 54 is formed outside the corner 50a of the circuit element 50 having a substantially rectangular shape in plan view. The underfill resin 57 seals the connection portion between the terminal portion of the circuit element 50 and the wiring pattern 52, and is in close contact with the base substrate 51 through the first opening 55. The adhesive strength between the underfill resin 57 and the base substrate 51 is greater than that between the underfill resin 57 and the solder resist film 54.
[Selection] Figure 6

Description

  The present invention relates to a flexible board on which electronic components are mounted and a recording apparatus including the flexible board.

  As a flexible substrate on which electronic components (circuit elements) are mounted, for example, a wiring flexible substrate (COF) that sends a drive signal based on print data using an actuator of a recording head that ejects ink as a load is known. The recording head 100 includes a cavity portion 101 having a large number of nozzles and ink supply paths, and an actuator 102 having an active portion corresponding to each nozzle, as described in Patent Document 1 and the like, as shown in FIG. A flexible substrate 103 on which an electronic component (circuit element) 104 is mounted is joined to the upper surface of the actuator 102 so as to be connected to an external signal source.

A connection portion between the circuit element 104 and the wiring pattern 107 on the flexible substrate 103 is usually sealed with a potting material as described in Patent Document 2.
Japanese Patent Laying-Open No. 2005-219337 (see FIG. 3) JP-A-9-323414 (see FIG. 6)

  Incidentally, the connecting portion between the flexible substrate 103 and the circuit element 104 generally has a structure as shown in FIGS. 10 (a) to 11 (b).

  That is, on the flexible substrate 103, a wiring pattern 107 made of a plurality of narrow copper foil wires is printed on one surface of a flexible base substrate 106 made of a film made of polyimide resin or the like. A solder resist film (insulating coating film) 109 is formed on one surface of the base substrate 106 so as to cover the wiring pattern 107 while leaving an opening surrounding the mounting region 108 of the circuit element 104 (FIGS. 10A and 10 (B). b)). Therefore, the reference numeral 109 a is the edge of the opening of the solder resist film 109 that surrounds the mounting region 108. Since the viscosity of the resin constituting the solder resist film is low, the edge 109a of the opening of the solder resist film 109 hangs down (flows) so as to approach the outer peripheral direction of the mounting region 108 as shown in FIG. The cross section is inclined so that the thickness decreases toward the mounting region 108.

  The end 107a of the wiring pattern 107 exposed from the edge 109a of the opening of the solder resist film 109 and the terminal formed on the lower surface of the circuit element 104 are connected via a bump 110 formed of a conductive material.

  Thereafter, the outer periphery of the circuit element 104, the solder resist film 109, and the underfill resin 111 are injected. Thus, the underfill resin 111 seals the connection portion between the terminal of the circuit element 104 and the end portion 107 a of the wiring pattern 107 and the end portion 107 a of the wiring pattern 107.

  The base substrate 106 of the flexible substrate 103 configured as described above has flexibility, but the circuit element 104 is solid, so when the base substrate 106 bends, the outer periphery of the circuit element 104 is The stress at the time of bending is concentrated in the vicinity of the overlapping portion between the underfill resin 111 and the solder resist film 109. In addition, when the circuit element 104 has a rectangular shape in plan view, the outer edge 112 of the underfill resin 111 that surrounds a corner (corner) where two adjacent sides intersect (see FIG. 11A) Is formed in a convex arc shape of approximately a quarter in a plan view, and stress at the time of bending such as bending and twisting tends to concentrate on the corner portion 112.

  In general, since the underfill resin 111 is a thermosetting epoxy resin and the solder resist film 109 is a urethane resin, the adhesion between the underfill resin 111 and the solder resist film 109 is not good. As a result, when the flexible substrate 103 is bent, the underfill resin 111 starts to be peeled from the solder resist film 109 from the outer peripheral edge of the corner portion 112. As the peeling progresses, when the flexible substrate 103 is bent, the wiring pattern 107 is formed in a region between the outer peripheral edge of the circuit element 104 and the edge 109a of the solder resist film (insulating coating film) 109 formation region. There has been a problem that such a breakage occurs (see FIG. 12) or a connection portion between the bump 110 and the end portion 107a of the wiring pattern 107 is broken.

  The present invention solves the above-mentioned problem, and improves the adhesive strength of the coating portion of the flexible substrate with the underfill resin to break the connection portion with the wiring pattern portion and the circuit element due to the bending of the flexible substrate. An object of the present invention is to provide a configuration capable of preventing the problem and to provide a recording apparatus including such a flexible substrate.

  In order to achieve the above object, the flexible substrate according to the first aspect of the present invention is a flexible substrate having an electronic component mounted on one side, and the base substrate of the flexible substrate is connected to a terminal portion of the electronic component. At least so as to seal a connection portion between the terminal part of the electronic component and the wiring pattern, and a wiring pattern that covers the wiring pattern except for a mounting region of the electronic component An underfill resin filled between the outer periphery of the electronic component and the insulating coating film is provided, and the base substrate is exposed outside the mounting area of the electronic component in the insulating coating film. A first opening is formed, and an adhesive strength between the underfill resin and the base substrate is larger than that between the underfill resin and the insulating coating film. The underfill resin is characterized in that in close contact with the base substrate through said first opening.

  According to a second aspect of the present invention, in the flexible substrate according to the first aspect, the electronic component is formed in a substantially rectangular shape in plan view, and the first opening is formed outside a corner portion of the rectangular shape. The part is formed.

  According to a third aspect of the present invention, in the flexible substrate according to the first or second aspect, the insulating coating film is a second opening that exposes an end portion of the wiring pattern connected to the terminal portion of the electronic component. And having the first opening outside the second opening.

  According to a fourth aspect of the present invention, in the flexible substrate according to the second aspect, the wiring pattern is formed to extend outward from a position on the base substrate corresponding to a rectangular side portion of the electronic component. The first opening is formed to expose the base substrate at a position where the wiring pattern is not disposed.

  According to a fifth aspect of the present invention, in the flexible substrate according to any one of the first to fourth aspects, the surface of the base substrate surrounded by the first opening has an adhesive strength with the underfill resin. A dummy pattern larger than that of the insulating coating film is formed.

  According to a sixth aspect of the present invention, in the flexible substrate according to any one of the first to fifth aspects, the underfill resin formation region is outward in plan view from the outer peripheral edge of the electronic component, and the insulation is formed. It is formed continuously over the overlapping portion with the coating film and the first opening that does not overlap with the insulating coating film.

  According to a seventh aspect of the present invention, the electronic component is a circuit element for selectively driving an actuator in a recording head that performs a recording operation, and the wiring pattern of the flexible substrate according to any one of the first to sixth aspects Is connected to the actuator.

  According to the first aspect of the present invention, in the first opening, the underfill resin is in direct contact with the surface of the base substrate, and the adhesive strength of the underfill resin to the surface of the base substrate is high. Therefore, even when the flexible substrate is bent, peeling of the underfill resin from the surface of the base substrate is not started. As a result, it is possible to reliably prevent accidents such as the wiring pattern being broken due to the bending, or the connection between the end of the wiring pattern and the electronic component being peeled off (electrically open). In addition, the end portion of the wiring pattern and the connection portion between the end portion and the electronic component are sealed and not exposed by the underfill resin, so that they are not exposed to the external environment, such as ink mist, and no corrosion occurs. There is an effect.

  According to the second aspect of the present invention, the electronic component is formed in a substantially rectangular shape in plan view, and the first opening is formed outside the corner of the rectangle. .

  Accordingly, the first opening, which is outside the four corners of the electronic component, is a place where the underfill resin is easily peeled off (a place where the bending stress increases) when the flexible substrate is bent. In this first opening, since the underfill resin is in direct contact with the surface of the base substrate, the underfill resin is less likely to be peeled off.

  According to the invention described in claim 3, the insulating coating film has the second opening that exposes the end of the wiring pattern connected to the terminal portion of the electronic component, and from the second opening. Has the first opening on the outside. In this way, since the underfill resin adheres to the surface of the base substrate outside the position where the terminal portion of the electronic component and the wiring pattern are connected, the connecting portion between the terminal portion of the electronic component and the wiring pattern is It can be protected from peeling and can be easily sealed.

  According to the invention of claim 4, the wiring pattern is formed to extend outward from a position on the base substrate corresponding to a rectangular side portion of the electronic component, and the first opening is Since the base substrate is exposed at a position where the wiring pattern is not disposed, the terminal part of the electronic component is connected to the wiring pattern corresponding to the side part, and the corner part of the electronic component is connected. It is possible to secure the first opening with a large area outside, that is, at a position where there is no wiring pattern, so that the underfill resin can be adhered to the base substrate, and the connection part between the terminal part of the electronic component and the wiring pattern can be reliably removed. Can be protected.

  According to the fifth aspect of the present invention, a dummy pattern having an adhesive strength with the underfill resin larger than that with the insulating coating film is formed on the surface of the base substrate surrounded by the first opening. Therefore, peeling of the underfill resin is less likely to occur at the first opening. Therefore, it is possible to improve the effect of reliably preventing accidents such as the wiring pattern for connection to the electronic component being broken due to the bending, or the connection portion between the end of the wiring pattern and the electronic component being peeled off.

  According to the invention described in claim 6, the underfill resin is outward in plan view from the outer periphery of the electronic component and overlaps with the insulating coating film, and overlaps with the insulating coating film. The first opening is not continuously formed. Accordingly, since the underfill resin does not start to peel off at the bonding portion between the underfill resin and the base substrate in the first opening, the effect of not peeling is affected by the overlap between the insulating coating film and the underfill resin. It can be taken over, and the sealing performance by the underfill resin is improved.

  According to a seventh aspect of the present invention, the electronic component is a circuit element for selectively driving an actuator in a recording head for performing a recording operation, and the wiring pattern of the flexible substrate according to the first to sixth aspects. Since the recording apparatus is characterized in that it is connected to the actuator, it is possible to reduce the trouble associated with the bending of the flexible substrate during assembly of the recording apparatus.

  FIG. 1 is a schematic plan view of a recording apparatus 1 including a flexible substrate according to the present invention. The recording apparatus 1 may be applied to a single printer apparatus, or may be applied to a printer function (recording unit) of a multi-function apparatus having a plurality of functions such as a facsimile function and a copy function.

  As shown in FIGS. 1 and 2, the recording apparatus 1 includes a box-shaped head holder 3 that constitutes a carriage 2. A recording head 4 is mounted on the lower surface side of the head holder 3 with its nozzles (not shown) exposed downward. The carriage 2 is supported by the first guide member 5 and the second guide member 6 so as to be capable of reciprocating in the main scanning direction (Y-axis direction), and is applied to a driving pulley 9 connected to the carriage motor 8 and a driven pulley 10. The passed timing belt 11 reciprocates along the Y-axis direction.

  A sheet as a recording medium is conveyed in the sub-scanning direction (X-axis direction) orthogonal to the main scanning direction (Y-axis direction) while being placed on the upper surface of a flat platen 7 disposed below the carriage 2. The

  In the recording apparatus main body 12, a replaceable ink cartridge 13 is stationary. Here, four inks for black ink, cyan ink, magenta ink, and yellow ink are used according to the number of ink colors. A cartridge 13 is provided. The ink in each ink cartridge 13 is independently supplied to an ink storage section 24 (described later) of the carriage 2 via a flexible resin ink supply tube 15.

  As shown in FIGS. 1 and 2, in the apparatus main body 12 of the recording apparatus 1, a maintenance unit 16 is provided on one side (right side in FIG. 1) outside the width (recording area) of the paper in the Y-axis direction. Is provided. The maintenance unit 16 performs a recovery operation (purging) for recovering the discharge function of the recording head 4 to be described later.

  Next, the configuration of the carriage 2 will be described. As shown in FIG. 3, the recording head 4 is fixed to the lower surface of the box-shaped head holder 3 whose upper surface is opened, and the upper side of the recording head 4 in the head holder 3. In addition, an ink storage unit 24 is disposed, and an electric circuit board 30 is disposed on the upper side of the ink storage unit 24 so as to close the upper surface of the head holder 3. The head holder 3 is an injection-molded product made of synthetic resin, and includes four side walls 3a and a bottom plate 3b, and has an upper surface opening 3c.

  An electric circuit (not shown) is formed on the lower surface 30a of the electric circuit board 30 by a known printed wiring along the surface 30a, and a plurality of capacitors such as a bypass capacitor and a resistor are connected to the electric circuit. Circuit element 31, first connector 34, and second connector 35 are provided. The electric circuit board 30 itself is configured in a substantially rigid plate shape with an electrically insulating material made of glass fiber and epoxy resin. It is assumed that a portion that is electrically connected to the electric circuit and the circuit element 31 is not exposed on the upper surface 30b of the electric circuit board 30 on the opposite side. In addition, when the terminal part of the circuit element 31 penetrates the electric circuit board 30 and is exposed to the upper surface 30b, it may be covered with an insulating film 47 of an electrically insulating material.

  Then, the electric circuit, the circuit element 31 and the connectors 34 and 35 are mounted inside the head holder 3, that is, the electric circuit board 30 with the lower surface 30 a facing downward covers the upper surface opening 3 c of the head holder 3. Is done. At this time, a frame-like sealing body 33 is inserted between the upper end surface 3 d of the head holder 3 and the outer periphery of the electric circuit board 30, and the electric circuit board 30 is connected to the head by fastening means such as a screw 32. It is fixed to the holder 3.

  The recording head 4 is similar to the known one described in Japanese Patent Application Laid-Open No. 2005-322850. As shown in FIG. 4, a flat cavity 21 having a nozzle on the lower surface side and a pressure chamber on the upper surface side. And the actuator 22 are laminated. A flexible substrate 23 having flexibility is connected to the upper surface of the actuator 22, and a heat radiating plate 25 made of a metal plate is laminated and bonded to the upper surface of the flexible substrate 23 that overlaps the actuator 22.

  The cavity portion 21 is formed by laminating a plurality of thin plates, and an ink supply path is formed therein. The ink supply path receives the supply of ink in the ink reservoir 24 from the ink intake 21a, and distributes the ink to many nozzles.

  As shown in FIG. 4, the actuator 22 is a flat shape having a size extending over all the nozzles, and a plurality of ceramic layers stacked in a direction perpendicular to the flat direction, and the actuator 22 is disposed between the plurality of ceramic layers. It consists of a plurality of internal electrodes.

  The internal electrode is configured as a pair of electrodes sandwiching the ceramic layer at each position corresponding to a large number of nozzles, one of which is an individual external electrode 22a formed on the top surface of the actuator 22, and the other is a common external electrode 22b. Are connected to each. These individual external electrode 22a and common external electrode 22b are connected to the wiring pattern of the flexible substrate 23, respectively.

  In the actuator 22 provided with electrodes in this manner, as is well known, by applying a voltage between the individual external electrode and the common external electrode, the portion of the ceramic layer sandwiched between the internal electrodes expands and the corresponding nozzle Pressure can be applied to the ink inside and ink (droplets) can be ejected from the nozzles.

  The recording head 4 is fixed to the lower surface side of the bottom plate 3 b of the head holder 3 with an adhesive 40 with a reinforcing frame 36 interposed therebetween. Therefore, a plurality of through holes 41 through which the adhesive 40 is poured are formed in the bottom plate 3b (see FIG. 3).

  Note that a rib 3e is provided on the lower surface of the head holder 3 so as to project the recording medium side (downward) so as to surround the recording head 4. In other words, the recording head 4 is disposed inside a recess formed on the lower surface side of the bottom plate 3b.

  A front frame 37 is provided so as to surround the recording head 4 inside the rib 3e in order to alleviate a step (unevenness) on the lower surface (surface facing the recording medium) side of the head holder 3. The front frame 37 is attached to the lower surface of the reinforcing frame 36 with an adhesive.

  The gaps between the outer periphery of the front frame 37 and the outer periphery of the recording head 4 and the lower edge of the head holder 3 are sealed with a seal 38 made of a material that is not affected by ink such as silicone resin. In this way, the outer periphery of the recording head 4 is fixed to the head holder 3 so as to be airtightly closed from the outside.

  The flexible substrate 23 is inserted from the upper surface of the recording head 4 into a slit hole 42 formed in the bottom plate 3 b of the head holder 3, and is drawn around the head holder 3. The terminal 23b (see FIG. 4) at the end of the flexible wiring member 23 is connected to one end of a flexible wiring member 46 in which a plurality of wires are arranged in parallel, and the other end 46a of the flexible wiring member 46 is an electric circuit board. It connects to the 1st connector 34 provided in the lower surface 30a of 30 (refer FIG. 3). The electric circuit board 30 receives a drive signal from a control device (not shown) stationary on the device body 12 via a flexible wiring cable 39 (see FIG. 2). Therefore, the wiring cable 39 connects the terminal 39 a at the end thereof to the second connector 35 provided on the lower surface 30 a of the electric circuit board 30, and connects the upper end surface 3 d of the one side wall 3 a of the head holder 3 and the electric circuit board 30. It is pulled out of the head holder 3 from between and connected to the control device.

  A drive circuit element 50 formed as an IC chip as an example of an electronic component for driving the actuator 22 is mounted in the middle of the flexible substrate 23 (see FIGS. 3 and 4). The drive circuit element 50 converts the drive signal serially transmitted from the electric circuit board 30 that closes the upper surface opening of the head holder 3 into a parallel signal corresponding to a number of nozzles, and outputs it as a voltage suitable for driving the ceramic layer. To do.

  In order to dissipate the heat of the drive circuit element 50, the radiator 43 is fixed to a pin (not shown) on the upper surface side of the bottom plate 3b. A rubber-like elastic member 44 is disposed between the bottom plate 3b and the flexible wiring member 23 so that the drive circuit element 50 is in close contact with the heat radiating body 43 so as to allow heat conduction. In order to guide the heat of the heat radiating body 43 to the outside of the head holder 3 and dissipate it to the outside air, the connecting portion 45a passing through the side wall 3a of the head holder 3 and connecting to the side portion 43b of the heat radiating body 43 and the outer surface of the side wall 3a. A diffusion plate 45 including a parallel diffusion portion 45b is provided (see FIG. 3).

  Next, a first embodiment of the configuration of the mounting location of the circuit element 50 as an electronic component on the flexible substrate 23 will be described in detail with reference to FIGS. 5 and 6. The basic structure of the flexible substrate 23 is connected to the input and output terminals of the circuit element 50 on one side of the flexible base substrate 51 made of a film made of polyimide resin or the like, as in the conventional description. A wiring pattern 52 made of a plurality of narrow copper foil wires is provided by known printing. An end 52 a of the wiring pattern 52 extends into the mounting area 53 of the circuit element 50. The circuit element 50 in the embodiment is a substantially rectangular chip body in plan view (see FIGS. 6A and 6B). Since the circuit element 50 includes the terminal portion along the outer periphery of the lower surface, the mounting region 53 matches the shape of the circuit element 50 in plan view.

  A solder resist film as an example of an insulating coating film having a uniform thickness over the entire surface of one side of the base substrate 51 in an outer region surrounding the mounting region 53, which is appropriately spaced outward from the outer peripheral edge of the mounting region 53. 54 is formed so as to cover the wiring pattern 52 (see FIGS. 5A and 5B). Accordingly, reference numeral 54a is an edge of the solder resist film 54 forming region, that is, an edge of openings 55 and 56 described later. Since the solder resist film 54 has a low viscosity, the edge portion of the formation region of the solder resist film 54 hangs (flows) so as to approach the outer peripheral direction of the mounting region 53, and FIG. 5B and FIG. As shown in (), the cross section is inclined so that the thickness decreases toward the mounting region 53.

  That is, the solder resist film 54 is formed with a second opening 56 that surrounds the mounting region 53 and exposes the end 52a of the wiring pattern 52 on the inner side, and the four corners of the second opening 56 are formed. That is, the first opening 55 is formed outside the corner portion 50a of the rectangular circuit element 50. The outside of these openings 55 and 56 is the formation region of the solder resist film 54. These openings 55 and 56 form one continuous opening and expose the base substrate 51. The plane area of the first opening 55 is preferably as large as possible in order to secure a bonding area between an underfill resin 57 and a base substrate 51 described later.

  The wiring pattern 52 is formed to extend outward from the position on the base substrate corresponding to the rectangular side portion of the circuit element 50, that is, the mounting region 53. The first opening 55 is formed to expose the base substrate 51 at a position where the wiring pattern 52 is not disposed (see FIGS. 5A and 5B).

  A terminal portion (not shown) formed on the lower surface of the circuit element 50 and an end portion 52a of the wiring pattern 52 are heated and pressed through bumps 59 formed of a conductive material such as gold or solder. Are connected by a method corresponding to the material of the bump 59 (see FIGS. 6A and 6B).

  Thereafter, an underfill resin 57 is filled at least between the outer periphery of the circuit element 50 and the solder resist film 54 so as to seal the connection portion between the terminal portion of the circuit element 50 and the wiring pattern (FIG. 6A). ) And FIG. 6B).

  The underfill resin 57 is in close contact with the end portion 52a of the wiring pattern 52 and the base substrate 51 at the four sides (excluding the corners) of the second opening 56, and in the second opening 56 in a plan view. It overlaps the upper surface of the solder resist film 54 beyond the edge. The width dimension of the overlapping part (the width dimension in the direction orthogonal to the side of the second opening 56) is W2. On the other hand, the underfill resin 57 is in close contact with the base substrate 51 without overlapping the solder resist film 54 at the location of the first opening 55.

  Generally, the underfill resin 57 is a thermosetting resin such as an epoxy resin. The base substrate 51 is a polyimide resin, and the solder resist film 54 is a urethane resin. For this reason, the adhesive strength between the underfill resin 57 and the base substrate 51 is greater than that between the underfill resin 57 and the solder resist film 54. The adhesive strength between the underfill resin 57 and the outer peripheral surface of the circuit element 50 is greater than that between the underfill resin 57 and the solder resist film 54. Therefore, in the first opening 55, the underfill resin 57 is in direct contact with the surface of the base substrate 51, and the adhesive strength of the underfill resin 57 to the surface of the base substrate 51 is assumed to be the first opening 55. When the solder resist film 54 covers the position, the adhesive strength of the underfill resin 57 to the surface of the solder resist film 54 is greater.

  The flexible substrate 23 is bent when it is carried for assembling to the recording apparatus 1 or drawn around the head holder 3. At this time, the stress is concentrated most at positions on the base substrate 51 corresponding to the four corners 50a of the circuit element 50. However, since the base substrate 51 and the underfill resin 57 are firmly bonded to each other in the first opening 55 that is outside the corner portion 50a, the underfill resin 57 may be peeled off from the base substrate 51. It can be suppressed. Moreover, since the corner | angular part 50a of the circuit element 50 and the underfill resin 57 are adhere | attached firmly, it can also suppress that it peels in the location with the said bending | flexion. Connection portions between the end portions 52a of the wiring pattern 52 and the terminal portions of the circuit element 50 at the four side portions (second opening portions 56) of the circuit element 50 are sandwiched by the four first opening portions 55, respectively. Therefore, it is protected from the above-described peeling progressing at those connection points. As a result, it is possible to reliably prevent an accident such as the connection portion between the end portion 52a of the wiring pattern 52 and the terminal portion of the circuit element 50 being peeled off (electrically opened) or the wiring pattern 52 in the vicinity thereof being broken. It is. Further, since the end portion 52a of the wiring pattern 52 and the connection portion between the end portion 52a and the terminal portion of the circuit element 50 are not sealed and exposed by the underfill resin 57, they are exposed to an external environment such as ink mist. No corrosion occurs. Note that the solder resist film 54 may be made of the same type of polyimide resin, epoxy resin, or the like as the base substrate 51. Even if the solder resist film 54 and the base substrate 51 are made of the same material, the surface of the base substrate 51 is subjected to a treatment such as roughening in order to improve the adhesion to the wiring pattern 52. Therefore, the underfill resin 57 has a higher adhesive strength with the base substrate 51 than the solder resist film 54.

  In the embodiment described above, the first opening 55 and the second opening 56 are continuous, so that the underfill resin 57 is in close contact with the base substrate 51 over both the openings 55 and 56. . However, the first opening 55 and the second opening 56 may be formed independently of each other, that is, the two may be formed by separating them with the solder resist film 54.

  7 (a), 7 (b), 8 (a), and 8 (b) show a second embodiment for improving the adhesive strength of the underfill resin 57 in the first opening 55. FIG. The form is shown. In this embodiment, as shown in FIGS. 7A and 8A, a dummy pattern having a high adhesive strength with the underfill resin 57 is formed on the surface of the base substrate 51 surrounded by the first opening 55. 60 is formed. The dummy pattern 60 is preferably formed of a conductive material such as copper, like the wiring pattern 52. In addition, when the wiring pattern 52 is printed on the surface of the base substrate 51, an extra step can be eliminated by forming the dummy pattern 60 at the same time. The area of the dummy pattern 60 in plan view is preferably as large as possible in order to ensure a large adhesion area with the underfill resin 57, and the outer periphery of the dummy pattern 60 is as close as possible to the inner periphery of the first opening 55. Formed.

  Further, the adhesive strength of the dummy pattern 60 to the surface of the base substrate 51 is larger than the adhesive strength of the underfill resin 57 to the surface of the dummy pattern 60, and the adhesive strength of the underfill resin 57 to the surface of the dummy pattern 60 is Same as or larger than that for 51 surface. Preferably, the adhesive strength of the underfill resin 57 to the surface of the dummy pattern 60 can be further increased by forming the surface of the dummy pattern 60 roughly using a chemical or the like. In the second embodiment, the underfill resin 57 is bonded to the surface of the dummy pattern 60. In addition, since the other structure is the same as 1st Embodiment, the same code | symbol is attached | subjected about the same structure and detailed description is abbreviate | omitted.

  By configuring in this way, even if the flexible substrate 23 is greatly bent and stress is concentrated on the position on the base substrate 51 corresponding to the corner portion 50a of the circuit element 50, as in the first embodiment, Since the dummy pattern 60 and the underfill resin 57 are firmly bonded, it is possible to prevent the underfill resin 57 from peeling from the flexible substrate 23. As a result, the connection portion between the end portion 52a of the four-side wiring pattern 52 of the circuit element 50 and the terminal portion of the circuit element 50 is peeled off (electrically opened), or the wiring pattern 52 in the vicinity thereof is broken. It is possible to prevent accidents.

  In the second embodiment, the dummy pattern 60 and the base substrate 51 may be exposed in the first opening 55, and the underfill resin 57 may be adhered to both. Further, the dummy pattern 60 can also serve as a part of signal lines or a grant line in the wiring pattern 52.

  In the present invention, the planar view form of the electronic component may be any of a circle, a triangle, and a polygon other than a rectangle.

  In the above-described embodiment, the recording apparatus has been described as an example. However, it is needless to say that the present invention can be applied to various apparatuses such as automobile parts and household electric apparatuses.

1 is a schematic plan view of a recording apparatus to which the present invention is applied. It is a perspective view of a recording part. It is a partially cutaway sectional view showing the inside of the head holder of the droplet discharge device. FIG. 3 is an exploded perspective view of a recording head. (A) is a top view which shows the 1st opening part and 2nd opening part in 1st Embodiment, (b) is a Vb-Vb arrow expanded sectional view of Fig.5 (a). (A) is a top view of the state which mounted the circuit element and sealed with underfill resin, (b) is the VIb-VIb arrow directional expanded sectional view of Fig.6 (a). (A) is a top view which shows the dummy pattern in the 1st opening part and 2nd opening part in 2nd Embodiment, (b) is an VIIb-VIIb arrow directional enlarged sectional view of Fig.7 (a). (A) is a top view of the state which mounted the circuit element and sealed with underfill resin, (b) is an VIIIb-VIIIb arrow directional cross-sectional enlarged view of Fig.8 (a). It is a disassembled perspective view of the recording head in a prior art. (A) is a top view which shows the mounting area | region of the circuit element in a prior art, and the formation area of a soldering resist film, (b) is an Xb-Xb arrow expanded sectional view of Fig.10 (a). (A) is a top view of the state which mounted the circuit element and sealed with underfill resin, (b) is the XIb-XIb line | wire arrow expanded sectional view of Fig.11 (a). It is sectional drawing which shows the fracture | rupture of the wiring pattern by peeling of the underfill resin in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording device 4 Recording head 23, 103 Flexible substrate 50, 104 Circuit element 51 as an electronic component, 106 Base substrate 52, 107 Wiring pattern 53, 108 Mounting area 54 of a circuit element 109 Solder resist film as an insulation coating film 55 First opening 56 Second opening 57, 111 Underfill resin 60, 110 Bump

Claims (7)

A flexible board with electronic components mounted on one side,
On the base substrate in the flexible substrate, a wiring pattern connected to the terminal part of the electronic component, and an insulating coating film covering the wiring pattern except for the mounting region of the electronic component are formed,
An underfill resin filled at least between the outer periphery of the electronic component and the insulating coating film is provided so as to seal a connection portion between the terminal portion of the electronic component and the wiring pattern, A first opening that exposes the base substrate is formed outside the mounting region of the electronic component in the covering film,
The adhesive strength between the underfill resin and the base substrate is greater than that between the underfill resin and the insulating coating film, and the underfill resin adheres to the base substrate through the first opening. A flexible substrate characterized by the above.   2. The flexible substrate according to claim 1, wherein the electronic component is formed in a substantially rectangular shape in plan view, and the first opening is formed outside a corner portion of the rectangle. .   The insulating coating film has a second opening that exposes an end of a wiring pattern connected to the terminal part of the electronic component, and the first opening is formed outside the second opening. The flexible substrate according to claim 1, wherein the flexible substrate is provided. The wiring pattern is formed to extend outward from a position on the base substrate corresponding to a rectangular side of the electronic component,
The flexible substrate according to claim 2, wherein the first opening is formed to expose the base substrate at a position where the wiring pattern is not disposed.   A dummy pattern having an adhesive strength with the underfill resin larger than that with the insulating coating film is formed on the surface of the base substrate surrounded by the first opening. Item 5. The flexible substrate according to any one of Items 1 to 4.   The underfill resin is continuous from the outer peripheral edge of the electronic component in a plan view and overlapping with the insulating coating film and the first opening not overlapping with the insulating coating film. The flexible substrate according to claim 1, wherein the flexible substrate is formed as described above.   The electronic component is a circuit element for selectively driving an actuator in a recording head that performs a recording operation, and the wiring pattern of the flexible substrate according to claim 1 is connected to the actuator. A recording apparatus.

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