JP6203014B2 - Base mounting structure for flexible circuit board - Google Patents

Description

  The present invention relates to a base mounting structure for a flexible circuit board formed by insert-molding a base made of synthetic resin on at least the back and side surfaces of a flexible circuit board.

  Conventionally, a synthetic resin base is attached to the back surface of a flexible circuit board formed with a circuit pattern on the front surface by insert molding, thereby fixing and supporting a flexible flexible circuit board. (For example, refer to Patent Document 1).

  FIG. 8 schematically shows a conventional example in which a flexible circuit board 200 is attached to and integrated with a bottom surface of a base (hereinafter referred to as “case”) 220 and a chip component (in this example, referred to as “light emitting element”) 205 is further attached. It is a schematic sectional drawing shown in FIG. As shown in the figure, the flexible circuit board 200 is insert-molded in a case 220 made of synthetic resin, and the case 220 is formed in a portion surrounding the back surface and the outer peripheral side surface of the flexible circuit board 200. The case 220 has a bottom part 221 and an outer peripheral side wall part 223, thereby providing a concave storage part 221 on the upper surface side, and the flexible circuit board 200 is installed on the bottom part of the storage part 221. The outer peripheral portion of the flexible circuit board 200 is sandwiched and fixed by the case 220.

  Further, a light emitting element 205 is attached to the surface of the flexible circuit board 200. The light emitting element 205 is attached by inserting the flexible circuit board 200 into the case 220 and then applying the low-temperature solder layer 203 on the connection pattern 201 formed on the surface of the flexible circuit board 200. The light emitting element 205 is placed, and the low temperature solder layer 203 and the terminal pattern 207 of the light emitting element 205 are brought into contact with each other. In this state, the ambient temperature around the case 220 is increased to reflow the low temperature solder layer 203. Do by.

JP 2000-151029 A

  However, if the light emitting element 205 is to be attached by solder reflow as described above, the flexible circuit board 200 is thermally expanded and extended by heat during reflow, and the central portion (exposed surface) is the case 220 as shown in FIG. There was a problem that it floated away from the surface of the bottom portion 221 of the. When the flexible circuit board 200 is lifted from the surface of the bottom 221, a defective electrical / mechanical connection with the light emitting element 205 occurs, an optical inconvenience occurs due to a change in the position of the light emitting element 205, or the flexible circuit board 200. Inconvenience may occur in other circuit patterns formed above.

  In order to solve the above problem, a method may be considered in which an adhesive layer is formed in advance on the back surface of the flexible circuit board 200 and the case 220 is molded by inserting the adhesive layer into a mold. However, when a hot melt type adhesive layer is used as the adhesive layer, the adhesive layer melts when the case with the flexible circuit board is reflowed by solder or used in a relatively high temperature atmosphere. Also, there is a risk that peeling will occur between the case 220 and the flexible circuit board 200. On the other hand, when an ordinary adhesive material is used as the adhesive layer, it is sticky, so that it is difficult to put in a mold and is difficult to handle, resulting in poor mass productivity.

  The present invention has been made in view of the above points, and its purpose is to prevent the flexible circuit board from being peeled off from the surface of the case even if the flexible circuit board after the base molding is reheated for reflowing or the like. Another object is to provide a base mounting structure for a flexible circuit board that can be easily manufactured.

The present invention comprises a flexible circuit board in which a circuit pattern is formed on the surface of a flexible film, and a base made of molded resin is adhered to at least the back surface and side surface of the flexible circuit board by insert molding. In the base mounting structure of the flexible circuit board to be attached, a large number of the solid particles are formed on the surface by applying a paste material obtained by kneading solid particles in a resin binder to the back surface of the flexible circuit board and drying and solidifying the paste material. It is characterized in that a non-adhesive adhesion layer having fine irregularities is provided, and the molding resin constituting the base is entangled and closely attached to the irregular surface of the adhesion layer.
An adhesion layer made of a paste material obtained by kneading solid particles in a resin binder is rough with many irregularities due to the solid particles on the surface. And since a base is attached to this adhesion layer at the time of insert molding, the synthetic resin which constitutes the base bites into the uneven surface of the adhesion layer, and the adhesion between both becomes strong and cannot be easily peeled off. Therefore, the base and the flexible circuit board are firmly fixed, and the flexible circuit board is not peeled off from the surface of the case even if it is reheated for reflowing or the like later. Further, since the adhesion layer is not sticky, it is easy to mount the flexible circuit board provided with the adhesion layer in the mold, and the manufacture thereof can be performed easily.

Further, the present invention is characterized in that the adhesion layer is made of the same material as any of the patterns constituting the circuit pattern.
Since it is not necessary to prepare another new material as the adhesion layer, it becomes possible to manufacture more easily.

According to the present invention, there is provided a base mounting structure for the flexible circuit board, wherein a connection pattern for connecting electronic components is formed on a surface of the flexible circuit board attached to the base, and the connection pattern includes an electronic circuit. The parts are attached by solder reflow.
When connecting an electronic component to the connection pattern of a flexible circuit board by solder reflow, the flexible circuit board is not peeled off from the case surface, so that the electromechanical connection with the electronic component is hindered or the position of the electronic component is Inconvenience does not occur by changing.

The present invention relates to a base mounting structure of the flexible circuit board, the circuit pattern, the conductive powder resistor pattern formed by the paste material obtained by kneading in a resin binder coated and dried The adhesion layer is formed by applying the same paste material as the resistor pattern and drying.

  According to the present invention, even if the flexible circuit board after the base molding is reheated for reflow or the like, the flexible circuit board is not peeled off from the surface of the case, and can be easily manufactured.

It is a schematic sectional drawing which shows typically case 1 with a circuit board. It is a schematic sectional drawing which shows the attachment method of the electronic component 60 to the case 1 with a circuit board. It is a schematic sectional drawing which shows typically case 1 with a circuit board to which electronic component 60 was attached. It is a perspective view which shows the specific example of case 1A with a circuit board, and the operating body 70A accommodated in the accommodating part 35A. It is an exploded perspective view of case 30A, flexible circuit board 10A, and terminal 80A. It is a figure which shows 10 A of flexible circuit boards, Fig.6 (a) is a top view, FIG.6 (b) is a back view. 2 is a schematic cross-sectional view of a case 1A with a circuit board housing an operating body 70. FIG. It is a schematic sectional drawing which shows typically the prior art example which attached the flexible circuit board 200 to the base 220, integrated, and also attached the chip component 205. It is explanatory drawing of the problem of a prior art example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view schematically showing a case 1 with a circuit board in which a flexible circuit board 10 is attached to a bottom surface of a base (hereinafter referred to as “case”) 30 and integrated. As shown in the figure, the case 1 with circuit board has a connection pattern 13 as a kind of circuit pattern formed on the surface of a flexible synthetic resin film 11 and an adhesive layer 50 formed on the back surface. The flexible circuit board 10 is provided, and a case 30 made of molded resin is attached to the back surface and the outer peripheral side surface of the flexible circuit board 10 by insert molding. In the case of this example, the adhesion layer 50 is formed on the entire back surface of the flexible circuit board 10, and the base 30 is attached to the adhesion layer 50 in close contact therewith. In the following description, “upper” refers to the direction of viewing the flexible circuit board 10 from the bottom 31 side of the case 30, and “lower” refers to the opposite direction.

  The film 11 constituting the flexible circuit board 10 uses a polyethylene terephthalate film (PET film) in this example, but other various films [for example, polyphenylene sulfide film (PPS film), polyimide film (PI film), etc. ] May be used. The plurality of connection patterns 13 formed on the upper surface of the film 11 are provided at positions facing a plurality of terminal patterns 61 provided on the light emitting element 60 described below. In this example, the resistor pattern is formed on the conductive pattern. It is comprised by the two-layer structure which formed. The conductive pattern is formed by applying and drying a conductive paste (silver paste) obtained by kneading conductive powder (in this example, silver powder) with a resin binder (in this example, thermosetting phenol resin). The resistor pattern is formed by applying and drying a resistor paste obtained by kneading conductive powder (carbon powder in this example) in a resin binder (thermosetting phenol resin in this example). The reason why the conductive pattern is covered with the resistor pattern is to protect the conductive pattern made of the silver pattern. Since the resistor pattern acts as a resistor for the thin thickness, it does not have a large resistance. Although not shown, various other circuit patterns such as a circuit pattern connected to the connection pattern 13 are also formed on the surface of the flexible circuit board 10.

  On the other hand, the adhesion layer 50 formed on the back surface of the film 11 is formed by applying and drying the same paste material as the resistor pattern used for the connection pattern 13. Here, the resistor paste used for the adhesion layer 50 and the resistor pattern (connection pattern 13) is obtained by printing a thin layer of carbon powder, which is solid particles, as described above, by screen printing or the like. Since the surface is dried, the surface has many fine irregularities due to the carbon powder, and has a rough surface. In this example, the surface roughness is about ± 5 μm.

  As a method for applying the paste material, screen printing is used in the above example, but other methods such as inkjet printing, flexographic printing, offset printing, letterpress printing, intaglio printing, and spray printing may be used.

  The case 30 is made of a thermoplastic resin (for example, polybutylene terephthalate (PBT), PET, nylon, ABS, etc.), and is filled with the thermoplastic resin in a mold cavity in which the flexible circuit board 10 is inserted. Manufactured after removing the mold. The case 30 has a bottom portion 31 and an outer peripheral side wall portion 33, whereby a concave storage portion 35 is provided on the upper surface side, and the flexible circuit board 10 is installed on the bottom portion of the storage portion 35. The surface of is exposed. By forming the case 30 in a portion surrounding the back surface and the outer peripheral side surface of the flexible circuit board 10, the outer peripheral portion of the flexible circuit board 10 is sandwiched and fixed by the case 30. Furthermore, in this case 1 with a circuit board, the adhesion layer 50 is provided on the back surface of the flexible circuit board 10, but the surface of the adhesion layer 50 is rough and rough as described above. The synthetic resin constituting the case 30 bites into and entangles the 50 uneven surfaces, and the two are in close contact with each other.

  FIG. 2 schematically shows a state in which a chip-type electronic component (hereinafter referred to as “light emitting element”) 60 is mounted on the connection pattern 13 of the flexible circuit board 10 of the case 1 with a circuit board configured as described above. It is a schematic sectional drawing. As shown in the figure, in order to mount and fix the light emitting element 60 on the flexible circuit board 10, first, a low temperature solder paste is applied and dried on the connection pattern 13 to form the low temperature solder layer 15. Next, a terminal pattern 61 provided on the surface of the light emitting element 60 is brought into contact with the low temperature solder layer 15. Then, the ambient temperature around the case 1 with the circuit board is set to 160 ° C. or more, which is the melting temperature of the low temperature solder layer 15, thereby reflowing the low temperature solder layer 15, and as shown in FIG. The terminal pattern 61 is electrically and mechanically joined.

  Due to the heating during the reflow, the flexible circuit board 10 tends to extend more than the case 30. However, as described above, since the adhesion between the synthetic resin constituting the case 30 and the adhesion layer 50 is strong and cannot be easily peeled off, the flexible circuit board 10 remains in the case 30 even if it is reheated for reflow. It will not peel off from the surface. For this reason, an electromechanical connection failure between the terminal pattern 61 and the connection pattern 13 of the light emitting element 60 does not occur, and an optical inconvenience does not occur due to a change in the position of the light emitting element 60. There is no inconvenience in other circuit patterns formed on the substrate 60.

  Further, since the adhesion layer 50 is not sticky, the flexible circuit board 10 provided with the adhesion layer 50 can be easily mounted in the mold, and the case 1 with the circuit board can be easily manufactured.

  In particular, in the case 1 with the circuit board, since the adhesive layer 50 is made of the same material as the resistor pattern constituting the connection pattern 13, it is necessary to prepare another new material for the adhesive layer 50. And can be manufactured more easily. That is, in general, the connection pattern 13 formed by, for example, applying and drying silver paste is often covered with a resistor pattern in order to protect the surface, but the adhesion layer is formed using the same material as the resistor pattern. 50 is formed, it is not necessary to prepare another new material as the adhesion layer 50 as described above, and the adhesion layer 50 can be formed easily and inexpensively.

  FIG. 4 is a perspective view showing a specific example of the case 1A with circuit board and an operating body 70A housed in the housing portion 35A. FIG. 5 is an exploded view of the case 30A, the flexible circuit board 10A, and the terminals 80. FIG. 6 is a view showing the flexible circuit board 10A, FIG. 6 (a) is a plan view, FIG. 6 (b) is a back view, and FIG. FIG. 6 is a schematic cross-sectional view (schematic cross-sectional view taken along line AA in FIG. 4) of a case 1 </ b> A with a circuit board that houses an operating body 70. In these drawings, the same or corresponding parts as those in the case 1 with a circuit board according to the embodiment shown in FIGS. 1 to 3 are denoted by the same reference numerals (provided that the suffix “A” is attached to each reference numeral). Note that matters other than those described below are the same as those of the case 1 with circuit board shown in FIGS.

  As shown in FIG. 5, a case 1A with a circuit board includes a case 30A having a bottom 31A and an outer peripheral side wall 33A, and a flexible circuit board installed at the bottom of a concave storage portion 35A provided on the upper surface of the case 30A. 10A and a terminal 80A having one end abutted on one side of the flexible circuit board 10A.

  As shown in FIG. 6, the flexible circuit board 10 </ b> A is provided with four connection patterns 13 </ b> A and a press switch pattern 17 </ b> A on the surface of the film 11 </ b> A. The pressing switch pattern 17A has a center switch pattern 17-1A and a surrounding switch pattern 17-2A surrounding the center switch pattern 17-1A in a U-shape. A lead pattern 19A is connected to each connection pattern 13A, the center switch pattern 17-1A, and the surrounding switch pattern 17-2A, and the other end of each lead pattern 19A is provided in parallel near one side of the flexible circuit board 10A. Connected to the terminal connection pattern 21A. At a predetermined position of the flexible circuit board 10A, a plurality of holes 23A are provided for connecting case 30A formed on the upper and lower surfaces thereof. Each connection pattern 13A, central switch pattern 17-1A, surrounding switch pattern 17-2A, each lead pattern 19A, and terminal connection pattern 21A are all made of conductive powder (in this example, silver powder) and resin binder (in this example, thermosetting). The conductive pattern is formed by applying and drying a conductive paste (silver paste) kneaded with the phenol resin), and for each connection pattern 13A, central switch pattern 17-1A, and surrounding switch pattern 17-2A, The resistor pattern is formed by applying and drying a resistor paste formed by kneading conductive powder (in this example, carbon powder) in a resin binder (in this example, thermosetting phenol resin) on the surface of the conductive pattern. Formed and configured. Note that a resist layer (not shown) is actually applied and protected on the extraction pattern 19A.

  Further, the adhesive layer 50A is formed on the back surface of the flexible circuit board 10A by applying the same paste material as the resistor pattern used for the connection pattern 13A and drying it. As described above, the adhesion layer 50 </ b> A has a large number of fine irregularities on the surface thereof, and has a rough surface.

  As shown in FIGS. 5 and 7, the terminal 80 </ b> A is formed of an elongated flat plate-like metal plate, and a middle portion is bent at a substantially right angle, so that the tip side is directed downward.

  Then, as shown in FIG. 5, the case 1 </ b> A with a circuit board is manufactured on one side of the outer periphery of the flexible circuit board 10 </ b> A (however, the light emitting element 60 </ b> A and the reversing plate 85 </ b> A shown in FIG. A cavity having the same shape as that of the case 30A is formed by abutting the tip of each terminal 80A (the terminal 80A at this time is not bent but extends linearly) on each terminal connection pattern 21A. It inserts in the metal mold | die which has and carries out by carrying out injection molding of the molten molding resin in the said cavity. Also in this case 1A with a circuit board, since the adhesion layer 50A is provided on the back surface of the flexible circuit board 10A, when the flexible circuit board 10A is insert-molded in the case 30A, the synthetic resin constituting the case 30A in the adhesion layer 50A. Is entangled and the adhesion between the two is strong. And the part of each terminal 80A which protrudes from the outer periphery of case 30A after manufacture of case 1A with a circuit board is bent below.

  Then, a low-temperature solder layer 15A (see FIG. 7) is formed by applying and drying a low-temperature solder paste on the exposed four connection patterns 13A of the case with circuit board 1A. Next, a terminal pattern 61A (see FIG. 7) provided on the surface of the light emitting element 60A is brought into contact with the low temperature solder layer 15A. Then, the ambient temperature around the case 1A with the circuit board is set to 160 ° C. or more, which is the melting temperature of the low-temperature solder layer 15A, thereby reflowing the low-temperature solder layer 15A and joining the connection pattern 13A and the terminal pattern 61A. .

  As described above, the flexible circuit board 10A tends to extend more than the case 30A due to the heating during the reflow, but the surface of the adhesion layer 50A has a large number of irregularities and is rough. The adhesion between the synthetic resin constituting the case 30A and the adhesion layer 50A is strong and cannot be easily peeled off. Therefore, even if reheating is performed for reflow, the flexible circuit board 10A is peeled off from the surface of the case 30A. There is nothing. Therefore, there is no electrical / mechanical connection failure between the light emitting element 60A and the connection pattern 13A, and no optical inconvenience occurs due to the change in the vertical position of the light emitting element 60A. Other circuit patterns and the like formed on 60A will not be adversely affected (such as a poor connection between the press switch pattern 17A and the reversing plate 85A described below or a poor touch feeling of the press switch).

  Next, the reversing plate 85A is placed on the exposed pressure switch pattern 17A of the case 1A with circuit board, and is fixed with an adhesive tape (not shown). The outer periphery of the reversing plate 85A is in contact with the surrounding switch pattern 17-2A, and the lower center surface of the reversing plate 85A is located at a predetermined distance from the central switch pattern 17-1A, thereby forming a pressing switch.

  On the other hand, the case 30A has a substantially rectangular shape and is made of a thermoplastic resin. The case 30A has a bottom portion 31A and an outer peripheral side wall portion 33A. By these, a concave storage portion 35A is provided on the upper surface side, and the bottom portion of the storage portion 35A. The flexible circuit board 10A is exposed. The portion where the flexible circuit board 10A and the terminal 80A are joined is fixed by sandwiching the upper and lower sides thereof by the case 30A. Bearing portions 39A each formed of a recess are formed at a predetermined position on the inner peripheral surface of the side wall 33A of the case 30A and one surface of the projection 37A protruding inward from the inner peripheral surface of the side wall 33A. Both bearing portions 39A are provided to face each other, and the upper end side of each of the bearing portions 39A is cut away so that a shaft portion 71A of the operating body 70A described below can be smoothly inserted from above.

  The actuating body 70A is an integrally molded product of transparent or translucent synthetic resin, and is formed in a substantially flat rectangular shape having an outer dimension to be inserted into the housing portion 35A of the case 30A. A cylindrical shaft portion 71A is provided along one side of the outer periphery of the operating body 70A. A pressing portion 75A (see FIG. 7) is provided on the lower surface of the operating body 70A.

  Then, the operating body 70A shown in FIG. 4 is stored in the storage portion 35A of the case 30A, and at that time, both ends of the shaft portion 71A of the operating body 70A are rotatably stored in the both bearing portions 39A of the case 30A. The operating body 70A is swingably supported.

  As shown in FIG. 7, when the upper surface of the operating body 70A is pressed by a pressing member 90A indicated by a dotted line, the operating body 70A swings down about the shaft portion 71A, and the pressing portion 75A is reversed. The plate 85A is pressed to reverse it, and the central lower surface of the reverse plate 85A comes into contact with the central switch pattern 17-1A to turn on the pressure switch. When the pressing by the pressing member 90A is released, the reversing plate 85A is automatically returned to the original shape by the automatic return force, the operating body 70A and the pressing member 90A are automatically returned to their original positions, and the pressing switch is turned off. On the other hand, if the light emitting element 60A emits light, the light passing through the inside of the operating body 70A illuminates members such as the pressing member 90A brightly.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea described in the claims and the specification and drawings. Is possible. Note that any shape, structure, or material not directly described in the specification and drawings is within the scope of the technical idea of the present invention as long as the effects and advantages of the present invention are exhibited. For example, in the above example, as the adhesion layer, a resistor paste obtained by kneading carbon powder in a resin binder and printed and dried by screen printing or the like is used, but other conductive solid particles (for example, silver particles or nickel) It may be an adhesion layer using a paste material obtained by kneading particles or the like) in a resin binder, or an adhesion layer using a paste material obtained by kneading solid particles made of an insulating material in a resin binder. May be. That is, if it is a paste material in which solid particles are kneaded with a resin binder, it may or may not have conductivity, and in short, any material may be used as long as the surface is roughened by solid particles.

  In the above example, the adhesion layer is applied to the entire back surface of the flexible circuit board. However, the adhesion layer may be formed on a part of the back surface of the flexible circuit board.

  In the above example, a light emitting element is used as an electronic component to be attached by reflow. May be an electronic component other than a chip type).

1, 1A Circuit board case 10, 10A Flexible circuit board 11, 11A Film 13, 13A Connection pattern (circuit pattern)
30,30A case (base)
50, 50A Adhesion layer 60, 60A Light emitting element (electronic component)
61, 61A Terminal pattern 17A Press switch pattern (circuit pattern)
19A Lead pattern (circuit pattern)
21A Terminal connection pattern (circuit pattern)

Claims (4)

A flexible circuit board comprising a flexible circuit board formed with a circuit pattern on the surface of a flexible film, and a base made of molded resin being attached to at least the back and side surfaces of the flexible circuit board by insert molding. In the circuit board base mounting structure,
A non-adhesive adhesion layer having a large number of fine irregularities due to the solid particles on the surface by applying a paste material obtained by kneading solid particles in a resin binder on the back surface of the flexible circuit board and drying and solidifying the paste material. A base mounting structure for a flexible circuit board, characterized in that a molding resin that constitutes the base is bitten into the uneven surface of the adhesive layer so that the base is attached in close contact. The base mounting structure for a flexible circuit board according to claim 1,
The base attachment structure for a flexible circuit board, wherein the adhesion layer is made of the same material as any of the patterns constituting the circuit pattern. A flexible circuit board mounting structure according to claim 1 or 2,
A connection pattern for connecting an electronic component is formed on the surface of the flexible circuit board attached to the base, and an electronic component is attached to the connection pattern by solder reflow. Base mounting structure. A base mounting structure for a flexible circuit board according to claim 2 or 3 ,
The circuit pattern, the conductive powder has a resistor pattern formed by the paste material obtained by kneading in a resin binder was applied and dried,
The adhesive layer is formed by applying and drying the same paste material as the resistor pattern and drying the flexible circuit board base mounting structure.

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