JP2005160206A - Waterproof structure of electronic unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waterproof structure of an electronic unit capable of preventing leakage of potting material injected into a case to the outside of the case, and preventing adhesion of the potting material to the engaging part of a connector fitting part. <P>SOLUTION: The waterproof structure of an electronic unit comprises a unit body 8 where an insulating board 20 having a connector fitting part 22 is stacked on a printed board 17 having an electronic component, and a case 35 for containing the unit body and the printed board 17 is waterproofed by burying it into a potting material 26 cured by injecting into a liquid sump part 47 within the case 35. A bank wall part 46 for preventing leakage of liquid potting material 26 to the outside of the case 35 is provided on the inside of the front wall part 37 for sectioning the liquid sump part 47, and the engaging hole 22a of the connector fitting part 22 engaging with the engaging protrusion 51c of an external connector 50 is located between the bank wall part 46 and the front wall part 37. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is an electronic device that is used in a humid environment, for example, an engine room of an automobile, and a liquid potting material injected into a case is cured, so that a substrate having electronic components housed in the case is waterproof protected. It relates to the waterproof structure of the unit.

  A conventional example related to the waterproof structure of this type of electronic unit is shown in FIGS. The first conventional example shown in FIG. 5 (Patent Document 1) relates to a liquid crystal display 55 used in a humid place such as a washing machine, and prevents moisture from entering the case, thereby ensuring the reliability of the liquid crystal display. It is the one that has improved the nature.

  The liquid crystal display 55 includes a control substrate 56 incorporated in a substrate support case (not shown) and a display unit 57. Electrical components such as a capacitor 56a and a connector housing are mounted on the control board 56. The display unit 57 includes an outer case 58 made of synthetic resin, an inner case 59 housed inside the outer case 58, and a liquid crystal display panel 60 housed in a housing space formed inside the outer case 58 and the inner case 59. And. The opening end of the inner case 59 is joined to the inner bottom surface of the outer case 58 with an adhesive or double-sided tape, and the potting material 61 is injected into the gap between the outer periphery of the inner case 59 and the inner periphery of the outer case 58. The storage space is hermetically sealed.

  As a result, the space on the lead-out side of the connection terminal pin 62 provided on the side edge of the liquid crystal display panel 60 and connected to the connection pattern (not shown) formed on the back surface of the control board 56 is sealed, and the storage space is externally provided. Water does not enter and the liquid crystal display panel 60 is protected from water.

  The second conventional example shown in FIG. 6 relates to an electronic unit 65 in which a circuit board 67 is buried in an insulating potting material 71 injected into a case 70 and the circuit board 67 is waterproof protected. The electronic unit 65 includes a unit main body 66 and a case 70 in which the unit main body 66 is accommodated. The unit body 66 includes a circuit board 67 on which a plurality of electronic components (not shown) are mounted, and a bus bar molded body 68 having a connector fitting portion 68a on one side.

  On the circuit board 67, a heat-sensitive transistor, an integrated circuit, or the like is mounted. The bus bar molded body 68 is equipped with a relay, a fuse or the like that generates heat. Therefore, in the case 70, the circuit board 67 is disposed in the lower layer, and the bus bar molded body 68 is disposed in the upper layer so that the circuit board 67 is not affected by heat.

In addition, the circuit board 67 located under the case 70 may be corroded by water or condensation that has entered the case 70 from the outside, and is therefore buried in the potting material 71 and is waterproof protected. . The potting material 71 is injected so as not to leak out of the case 70 to such an extent that the circuit board 67 is completely buried.
JP-A-5-142522 (page 3-4, FIG. 5)

  However, the above conventional example has the following problems to be solved. In the first conventional example, the potting material 61 is filled in the gap between the outer periphery of the side wall of the inner case 59 and the inner periphery of the side wall of the outer case 58 to prevent moisture from entering. There was a concern that the potting material 61 leaked from the outer case 58 and contaminated the product and work table. If the product becomes dirty, the appearance of the product deteriorates, and therefore, it is necessary to clean the dirt cleanly, and it takes extra time other than the assembly of the liquid crystal display 55, and there is a concern that the assembling workability is deteriorated.

  Further, if the side wall of the outer case 58 is formed high in order to prevent the potting material 61 from leaking out of the outer case 58, there is a problem in that the liquid crystal display 55 is sublime and cannot be made compact.

  In the second conventional example, since the entire circuit board 67 is embedded in the potting material 71, the entire circuit board 67 is waterproofed. However, when the liquid potting material 71 is mistakenly put too much, there is a concern that the potting material 71 gets over the side wall and leaks to the outside, and stains the product and the like in the same manner as in the first conventional example. Further, since the electronic unit 65 is increased in size, it is difficult to prevent the potting material 71 from leaking by raising the side wall of the case 70.

  Furthermore, there is a problem that the potting material 71 leaked to the outside adheres to the locking hole 68b of the connector fitting portion 68a and hardens, so that the external connector 69 cannot be fitted into the connector fitting portion 68a. .

  In view of the above-described points, the present invention can prevent the potting material injected into the case from leaking out of the case without enlarging the case, and the potting material is an engaging portion of the connector fitting portion. An object of the present invention is to provide a waterproof structure for an electronic unit that can be prevented from adhering to water.

  To achieve the above object, a first aspect of the present invention is a unit main body in which a substrate having a plurality of electronic components and an insulating substrate having a connector fitting portion are laminated, and a case for housing the unit main body. And a waterproof structure of the electronic unit in which the substrate is waterproof protected by a potting material injected into the liquid reservoir in the case and cured, and is provided inside the wall portion that defines the liquid reservoir. A bank wall portion for preventing the potting material from leaking out of the case is provided.

  According to the above configuration, the moisture-proof liquid potting material injected into the liquid reservoir of the case is cured, so that the unit body substrate is protected from waterproofing, and transistors, capacitors and integrated circuits mounted on the substrate are protected. Moisture resistance and electrical insulation of electronic parts such as circuits are enhanced, and corrosion and short circuits are prevented. And when a liquid potting material enters too much and the liquid level of a potting material becomes higher than a bank wall part, the overflow potting material accumulates in the clearance gap between a bank wall part and a side wall. In addition, by making the potting material urethane resin with excellent heat dissipation, for example, the heat generated from the electronic components on the board is dissipated to the surroundings through the potting material, and the electronic components are thermally deteriorated and the soldered portion is deteriorated. Is prevented.

  According to a second aspect of the present invention, in the waterproof structure for an electronic unit according to the first aspect, a groove is formed between the wall portion and the wall portion.

  According to the above configuration, when the liquid potting material is poured too much into the liquid reservoir, the overflowing potting material gets over the bank wall and accumulates in the groove.

  According to a third aspect of the present invention, in the waterproof structure of the electronic unit according to the first or second aspect, the connector fitting portion is provided with an engaging portion for the locking portion of the external connector, and the engaging portion is It is located between the bank wall part and the wall part.

  According to the above configuration, the potting material that has overflowed due to excessive injection is prevented from adhering to the engaging portion of the connector fitting portion.

  According to a fourth aspect of the present invention, in the waterproof structure for an electronic unit according to the third aspect, the bank wall portion is an enclosure portion formed in a frame shape at a position corresponding to the engagement portion. And

  According to the said structure, an engaging part is protected by an enclosure part and it is prevented that a potting material adheres to an engaging part.

  As described above, according to the first aspect of the present invention, since the bank wall portion is provided inside the wall portion that defines the liquid reservoir portion, the liquid potting material enters the liquid reservoir portion too much, and the potting is performed. When the liquid level of the material becomes higher than the bank wall, the overflowing potting material gets over the bank wall and accumulates in the gap between the bank wall and the wall. Therefore, it is possible to reliably prevent the potting material from leaking to the outside of the case, and it is possible to protect a portion that causes inconvenience when the potting material adheres.

  According to the second aspect of the present invention, since the groove is formed between the wall portion and the wall portion, the overflowing potting material gets over the wall and accumulates in the groove. Therefore, the effect of claim 1 is promoted, and the potting material can be reliably prevented from leaking to the outside of the case.

  According to the invention described in claim 3, since the engaging portion is located between the wall portion and the wall portion, the potting material overflowing after being excessively injected is the engaging portion of the connector fitting portion. It is prevented from adhering to. Therefore, the external connector can be detachably attached to the connector fitting portion, and the reliability of connector connection is improved.

  According to the fourth aspect of the present invention, the engaging portion is effectively protected by the bank wall portion, and the potting material is prevented from adhering to the engaging portion. Therefore, an effect equivalent to that of the invention of claim 3 is obtained, and the reliability of the connector connection lock is improved.

  Specific examples of embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 3 show an embodiment of a waterproof structure for an electronic unit according to the present invention, and FIG. 4 is a modification of a case in which a unit main body is accommodated.

  The electronic unit 5 includes an electrical component such as a fuse and a relay 24 (FIG. 3), an electronic component such as a diode, a resistor, a transistor 32 (FIG. 3), a coil, a capacitor, and an integrated circuit in the unit body 8, and A connector fitting portion 22 for connecting these circuits to an external circuit is provided, and a relay 24 is connected to electronic parts such as a transistor 32 and a capacitor via a bus bar 13 so that a wiper, a washer fluid, a front It is a communication control device that controls auxiliary equipment such as lights. The electrical components are mounted on the bus bar wiring board 10, and the electronic components are mounted on a printed circuit board (substrate) 17, and the bus bar wiring board 10 and the printed circuit board 17 are arranged vertically in a layered structure.

  The waterproof structure of the electronic unit 5 of the present embodiment prevents the potting material 26 injected into the case 35 from leaking out of the case 35 by changing the shape of the case 35 without increasing the size of the case 35. In addition, the potting material 26 can be prevented from adhering to the locking hole (engagement portion) 22a of the connector fitting portion 22, and the printed circuit board 17 having a plurality of electronic components, A unit main body 8 formed by laminating an insulating substrate 20 having a connector fitting portion 22 and a case 35 for housing the unit main body 8 are provided, and the moisture resistance that has been injected into the liquid reservoir 47 in the case 35 and cured is cured. In the waterproof structure of the electronic unit 5 in which the printed circuit board 17 is protected by waterproofing by being buried in the potting material 26 having, before the liquid reservoir portion 47 is partitioned. A wall wall 46 for preventing leakage of the injected potting material 26 outside the case 35 is provided inside the wall wall 37, and the external connector 50 is connected between the wall wall 46 and the front wall 37. The locking hole 22a of the connector fitting portion 22 that engages with the locking protrusion (locking portion) 51c is located. Further, it is effective that a groove 48 is provided between the bank wall portion 46 and the front wall portion 37.

  Below, the main structural part is demonstrated in detail about the waterproof structure of the electronic unit 5 of this embodiment. The electronic unit 5 includes a case 35 made of a synthetic resin material and a unit body 8.

  The case 35 is formed by resin molding using PBT having excellent moldability and heat resistance as a constituent material. As shown in FIG. 3 in which the electronic unit 5 is disposed upside down, the case 35 has an outer wall composed of a bottom wall 36 and a peripheral wall, an opening is formed in the top wall, and the unit main body 8 is accommodated. It has become so. The wall portions 39, 39 on both sides are provided with a lock arm 39a for fixing the electronic unit and a locking hole 39b for the locking claw 9 of the unit main body 8 (only one wall portion 39 is shown). . When the unit main body 8 is accommodated in the case 35, the case 35 and the unit main body 8 are united by engaging the locking holes 39 b with the locking claws 9. A wide opening 37a is formed in the front wall portion 37 so that the connector fitting portion 22 provided on the front side of the unit main body 8 is disposed.

  A partition wall 45 is erected on the bottom wall 36 to prevent heat from the relay 24 and the fuse from being transferred to the printed circuit board 17 (FIG. 1). In front of the partition wall 45 of the bottom wall 36, an aluminum plate 41 having a heat dissipation property for releasing heat generated from the printed circuit board 17 is fitted. Small holes (not shown) are provided in the four corners of the rectangular aluminum plate 41, pins are provided in the bottom wall 36, and the aluminum plate 41 is fixed to the bottom wall 36 by engaging the small holes with the pins. It has become so. A plurality of fuse holding portions 42 are provided on the rear side of the bottom wall 36. A fuse (not shown) is set in the fuse holding portion 42, and a tab-like lead terminal extending in the setting direction is connected to the tuning-fork-like terminal portion 13e.

  A slit 43 is formed in the bottom wall 36 at a position corresponding to the relay 24. The outside air flowing in through the slit 43 effectively cools the relay 24 and the fuse, which are heat-generating electrical components, and the heat-sensitive electronic components on the printed circuit board 17. By providing the slit 43, there is a concern that moisture and water may enter the case 35 together with the outside air. However, the entire printed circuit board 17 including the electronic components is buried in the moisture-proof potting material 26. The substrate 17 is protected from waterproofing.

  At the intersection of the bottom wall 36 and the front wall portion 37 that is orthogonal to the bottom wall 36, there is a bank wall portion 46 that is located inside the front wall portion 37 and extends along the front wall portion 37. Is provided. The bank wall portion 46 is provided so as to have a dimension higher than the resin surface of the potting material 26 injected into the liquid reservoir portion 47 of the case 35. A liquid reservoir 47 is formed between the partition wall 45 and the bank wall 46, and the bank wall 46 prevents the potting material 26 injected into the liquid reservoir 47 from leaking out of the case 35. It is a standing wall.

  As shown in FIG. 2, the liquid potting material 26 is liquidated by the injection nozzle 27 inserted into the injection hole 28 (FIG. 3) of the insulating substrate 20 and the insertion hole 18 b of the printed circuit board 17 in the assembly process of the electronic unit 5. It is designed to be injected into the reservoir 47. However, when the operator puts the potting material 26 too much, or when the electronic unit 5 is mistakenly tilted after the potting material 26 is injected, the bank wall portion 46 is used. The potting material 26 leaking from the liquid storage portion 47 after getting over is accumulated in a bowl-shaped groove 48 formed between the front wall portion 37 and the bank wall portion 46. This prevents the potting material 26 overflowing from the liquid reservoir 47 from leaking out of the case 35.

  Moreover, since the locking hole 22a of the connector fitting part 22 is located between the front wall part 37 and the bank wall part 46, the potting material 26 leaking from the liquid reservoir part 47 is locked into the locking hole 22a. And the engagement between the locking hole 22a and the locking projection 51c of the external connector 50 is also prevented. For this reason, the reliability of the lock | rock of the external connector 50 detachably fitted to the connector fitting part 22 is improved.

  For the potting material 26, a urethane resin having moisture resistance and electrical insulation is used. The urethane resin is cured (solidified) to seal the gap between the case 35 and the aluminum plate 41 so that water does not come into contact with the printed circuit board 17. In addition, since the urethane resin has good thermal conductivity and excellent heat resistance, the heat generated from the printed circuit board 17 is dissipated to the outside, and the temperature rise of the printed circuit board 17 is prevented. Since the potting material 26 is also in close contact with the aluminum plate 41 having excellent heat dissipation, the heat dissipation of the printed circuit board 17 is further enhanced.

  FIG. 4 shows a modification of the case 35 shown in FIG. 3, which effectively prevents the potting material 26 from adhering to the locking holes 22 a of the connector fitting portion 22. The enclosure portion 46 ′ as a bank wall portion is provided at a position corresponding to the locking hole 22 a at the center of the connector fitting portion 22. Such an enclosing portion 46 'can be appropriately provided in a portion where the inconvenience occurs when the potting material 26 adheres, and can also be provided at a position corresponding to the locking holes 22a of the connector housings on both sides.

  Next, the unit body 8 will be described. As shown in FIG. 3, the unit main body 8 includes a bus bar wiring board 10 in which bus bar molded bodies 11 and 12 are laminated in two layers, and a printed board 17. The bus bar molded bodies 11 and 12 are formed by integrally molding the bus bar 13 and the insulating substrate 20 by insert molding. A plurality of relays 24 are mounted on the bus bar molded body 12 as electrical components.

  The insulating substrate 20 is made of PBT (polybutylene terephthalate) suitable for insert molding. This insulating substrate 20 is for insulating and protecting the bus bar 13, and is integrally formed on the bus bar main body excluding the terminal portions 13b, 13c, 13d, and 13e formed at the end of the bus bar 13. The bus bar main body is not shown because it is embedded in the insulating substrate.

  Three connector fitting portions 22 are provided on the front side of the insulating substrate 20. For convenience, reference numeral 22 is attached to the central connector fitting portion. A tab-like terminal portion 13d for connecting a connector protrudes inside the connector fitting portion 22, and the connector fitting portion 22 and the terminal portion 13d constitute a female connector. A male external connector 50 having female terminals is fitted into the female connector. FIG. 3 shows an external connector 50 fitted to the central connector fitting portion 22 as an example.

  The external connector 50 includes a connector housing 51 and female terminals (not shown). The connector housing 51 has a terminal accommodating chamber 51a partitioned by an outer wall and a partition, and female terminals are accommodated in the terminal accommodating chamber 51a. On the ceiling wall of the connector housing 51, an L-shaped lock arm 51 b that is locked to the connector fitting portion 22 is projected. The lock arm 1b is provided with a locking projection 51c, and the locking projection 51c engages with the locking hole 22a of the connector fitting portion 22, so that the external connector 50 is engaged with the connector fitting portion 22. It has come to be stopped.

  The lock arm 51b is formed so as to be elastically deformable with a base portion as a fulcrum, and by depressing the free end portion, the locking is released and the external connector 50 is pulled out from the connector fitting portion 22. . The female terminal is formed by punching and bending from a conductive substrate, and has an electrical contact portion on one side and an electric wire connection portion on the other side. The female terminal is locked by the flexible locking piece 51d in the terminal accommodating chamber 51a to prevent the female terminal from coming out.

  A relay holding unit 30 to which a plurality of relays 24 are attached is provided on the rear side of the insulating substrate 20. The relay holding portions 30 are provided at five locations, and the relays 24 having different sizes are held respectively. A plurality of tab holes for inserting lead terminals of the relay 24 are formed through the bottom surface of the relay holding portion 30. By setting the relay 24 in the relay holding portion 30, the lead terminal is inserted into the tab hole and comes into contact with the terminal portion 13a (FIGS. 1 and 2) of the bus bar 13 protruding to the back side of the insulating substrate 20. . The positioning structure of the relay 24 will be filed in another application.

  The bus bar 13 is a circuit conductor made of copper or copper alloy as a constituent material and punched in accordance with a predetermined circuit pattern by a press, and a terminal group formed at the horizontal bus bar main part and the end of the bus bar main part 13b, 13c, 13d, and 13e. Since the bus bar main body is embedded in the insulating substrate 20, it is insulated and protected from being short-circuited with the outside.

  The terminal groups 13b, 13c, 13d, and 13e are composed of terminal portions 13b and 13c for board connection, terminal portions 13d for connector connection, and terminal portions 13e for fuse connection. The terminal portions 13b and 13c (FIGS. 1 and 2) for connecting the substrate have a tab shape, and are formed upright on the left and right sides and the central portion of the bus bar wiring board 10 (FIG. 3). The left and right terminal portions 13b and 13b are formed to face each other, and the central terminal portion 13c is formed in a direction orthogonal to the left and right terminal portions 13b and 13b.

  Since the plurality of terminal portions 13b and 13c for connecting the substrates are connected in a state of being aligned in a horizontal row by an alignment correction resin band 15 formed by insert molding, shaking such as falling is prevented. It is accurately inserted into the terminal hole 18a formed in the printed circuit board 17 located on the lower side of the wiring board 10, and is directly connected to the circuit pattern by soldering. A plurality of soldered portions 19 (FIG. 3) of the terminal portions 13 b and 13 c are formed on the back surface of the printed circuit board 17.

  The plurality of terminal portions 13d for connector connection have a tab shape and are arranged in parallel on the front side of the bus bar wiring board 10. As described above, the female terminal of the external connector 50 is connected to the terminal portion 13d. By connecting the external connector 50 to the unit main body 8, the internal circuit and the external circuit are electrically connected, power supply and signal transmission / reception are performed, and the electronic unit 5 functions as a control device capable of multiplex communication. It has become.

  The fuse connecting terminal portion 13e (FIG. 3) has a tuning fork shape, and is arranged in parallel along the rear side of the bus bar wiring board 10. The terminal portion 13e has a pair of elastic arm portions, and a lead terminal of the fuse is sandwiched between convex electric contact portions formed on the tip side of each arm portion. .

  The printed circuit board 17 includes an insulating substrate 18 having a wiring conductor and electronic components (not shown) such as a transistor 32 and a capacitor mounted on the substrate 18. For the insulating substrate, a glass epoxy resin or the like having a low coefficient of thermal expansion and hardly causing deformation such as warpage during curing is used. A circuit pattern is formed on the insulating substrate, and the terminal portions 13b and 13c of the bus bar 13 are electrically connected to the circuit pattern by soldering. Electronic components such as a transistor 32 and a capacitor are connected to the terminal portions 13b and 13c of the bus bar 13 through a circuit pattern.

  Although heat is generated from these electronic components, since the potting material 26 is made of urethane resin having excellent heat dissipation, the potting material 26 functions as a heat sink, and the electronic components and the printed circuit board 17 are interposed via the potting material 26. The heat generated from the heat is dissipated to the surroundings to prevent the electronic components and the like from reaching a high temperature state, and the thermal deterioration of the electronic components and the soldered portion are prevented. In addition, it is possible to further improve heat dissipation by interposing a filler having thermal conductivity, such as silica or aluminum nitride, in the potting material 26 to enhance the heat sink function.

  As described above, according to the present embodiment, since the bank wall portion 46 (enclosure portion 46 ′) is provided inside the front wall portion 37 that partitions the liquid reservoir portion 47 of the case 35, the liquid reservoir portion 47. When the liquid potting material 26 enters too much, the overflowing potting material 26 gets over the bank wall portion 46 and collects in the gap (groove 48) between the bank wall portion 46 and the front wall portion 37. It is possible to prevent the material 26 from leaking outside the case 35. Moreover, since the locking hole 22a of the connector fitting part 22 is located between the bank wall part 46 and the front wall part 37, the potting material 26 adheres to the locking hole 22a of the connector fitting part 22. Thus, the external connector 50 can be detachably attached to the connector fitting portion 22 to improve the reliability of the lock.

In addition, this invention is not limited to the said embodiment, It can deform | transform and implement as follows.
(1) The electronic unit 5 is configured by changing to an electrical connection box such as a junction box, a relay box, or an ECU box. According to such a configuration, it is possible to protect the electrical / electronic component in a waterproofing manner without impairing the heat dissipation, similarly to the electronic unit 5 of the present embodiment.
(2) The potting material 26 is made of silicone resin, epoxy resin or the like instead of urethane resin. These resins are excellent in adhesion, waterproofness, and dustproofness, and can protect the printed circuit board 17 in the same manner as when urethane resin is used. In particular, since the silicone potting material has excellent vibration resistance, it is possible to prevent generation of cracks due to impact or vibration. In addition, since the epoxy potting material has a low thermal expansion coefficient, it is possible to prevent warping of the printed circuit board 17 by reducing the stress during heat curing.

It is sectional drawing which shows one Embodiment of the waterproof structure of the electronic unit which concerns on this invention. It is sectional drawing which shows the state before inject | pouring a potting material into the electronic unit shown in FIG. FIG. 6 is an exploded perspective view showing the electronic unit upside down. It is a perspective view which shows the modification of the case shown in FIG. It is a perspective view which shows an example of the waterproof structure of the conventional electronic unit. It is a perspective view which shows another example of the waterproof structure of the conventional electronic unit.

Explanation of symbols

5 Electronic unit 8 Unit body 17 Printed circuit board (board)
20 Insulating board 22 Connector fitting part 22a Locking hole (engagement part)
26 Potting material 35, 35 'Case 37 Front wall portion 46 Dyke wall portion 46' Enclosing portion 47 Liquid reservoir portion 48 Groove 50 External connector 51c Locking protrusion (locking portion)

Claims (4)

A unit main body formed by laminating a substrate having a plurality of electronic components, an insulating substrate having a connector fitting portion, and a case for housing the unit main body, and injected into a liquid reservoir in the case and cured A waterproof structure of the electronic unit in which the substrate is waterproof protected by the potting material,
A waterproof structure for an electronic unit, characterized in that an embankment wall portion for preventing leakage of the potting material out of the case is provided inside a wall portion that defines and forms the liquid reservoir portion.   The waterproof structure for an electronic unit according to claim 1, wherein a groove is formed between the bank wall portion and the wall portion.   The engagement part with respect to the latching | locking part of an external connector is provided in the said connector fitting part, and this engagement part is located between the said bank wall part and the said wall part. Waterproof structure of the electronic unit described.   4. The waterproof structure for an electronic unit according to claim 3, wherein the bank wall portion is an enclosure portion formed in a frame shape at a position corresponding to the engagement portion.

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