This application claims priority to Japanese Patent Application No. 2016-029735 filed on Feb. 19, 2016, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an electronic unit manufacturing method.
2. Description of Related Art
In recent years, there is a demand for mounting electronic components such as MOS devices on a single substrate of an electronic unit for driving an actuator to make it possible to downsize the actuator. The electronic components generate heat when they are in operation. It is known to coat the electronic components with heat dissipating gel for dissipating the heat of the electronic components through the heat dissipating gel and a radiator.
To dissipate heat through heat dissipating gel, it is important to prevent formation of voids in the heat dissipating gel as much as possible. Japanese Patent Application Laid-open No. H10-50742 describes an electronic unit manufacturing method in which heat dissipating gel is discharged from a nozzle having a small-diameter opening to be coated on a substrate and side surfaces and a top surface of an electronic component while moving the nozzle spirally from the periphery to the center of the electronic component to suppress formation of voids in the discharged heat dissipating gel.
However, in the above conventional method, since the heat dissipating gel is discharged in a thin line from the small-diameter opening of the nozzle, different portions of the heat dissipating gel discharged from the small-diameter opening of the nozzle contact frequently at their interfaces. Accordingly, roll-in voids may occur in the discharged heat dissipating gel. In this case, since the heat dissipation properties of the electronic component are deteriorated, it may become difficult to downsize the electronic unit.
Further, in the above conventional method, the discharged heat dissipation gel has a mound shape in which the height at the center is larger than the periphery thereof after the coating is finished. Accordingly, when a radiator such as a heat sink is pressed against the heat dissipation gel being discharged so as to put the heat dissipation gel between the radiator and the electronic component, the heat dissipation gel may spread significantly around the electronic component. Therefore, there is a concern that the downsizing of the electronic unit may be prevented in a case where the coating area of the heat dissipation gel is specified or limited.
In addition, since the heat dissipation gel is discharged from the small-diameter opening of the nozzle while moving the nozzle spirally from the periphery to the center of the electronic component, the coating time is long, causing the manufacturing efficiency to be low and causing the manufacturing cost to be high.
An exemplary embodiment provides a method of manufacturing an electronic unit that includes an electronic component having a rectangular plate shape and generating heat during operation, and a heat dissipation gel covering the electronic component, including:
According to the exemplary embodiment, there is provided a method capable of manufacturing a compact electronic unit including an electronic component having a high heat dissipation property in a short time.
Other advantages and features of the invention will become apparent from the following description including the drawings and claims.
In the accompanying drawings:
The case 2 is made of metal in a bottomed cylindrical shape. The stator 3 is made of metal such as steel in an annular shape and fixed to the inner wall of the case 2. The winding 4 is made of metal such as copper in a wire shape and wound on the stator 3. The shaft 5 is made of metal in a stick shape and rotatably supported by the case 2. The shaft 5 is disposed such that its one end projects to the outside from the bottom of the case 2.
The rotor 6 is made of metal such as steel in a cylindrical shape and provided integrally in the shaft 5 such that its inner wall fits the outer wall of the shaft 5. Accordingly, the rotor 6 can rotate together with the shaft 5. A not shown magnet is provided in the outer wall of the rotor 6 so as to be opposite to the inner wall of the stator 3. The pulley 7 is disposed at one end of the shaft 5. The magnet 8 is fitted to the other end of the shaft 5. Accordingly, the pulley 7 and the magnet 8 can rotate together with the shaft 5. The electronic unit 10 is disposed at the opening of the case 2. The cover 9, which covers the electronic unit 10, is disposed in the case 2 so as to close the opening of the case 2. The electronic unit 10 includes a heat sink 20 as a radiator, a substrate 30, electronic components 40, a microcomputer 11, a rotation angle sensor 12 and heat dissipation gel 50. The electronic unit 10 controls electric power supplied to the winding 4 to control the rotation of the rotor 6.
The motor 1 is a mechanically/electrically-integrated motor.
The heat sink 20 is made of metal such as aluminum to have a plate shape, and disposed so as to close the opening of the case 2. The heat sink 20 is formed with a hole 21 at its center. The other end of the shaft 5 is located in the hole 21. The substrate 30 is disposed on the side of one surface 201 (first surface 201 hereinafter) of the heat sink 20, that is, disposed on the side opposite the stator 3. One surface 301 (first surface 301 hereinafter) of the substrate 30 is opposite the first surface 201 of the heat sink 20. The electronic components 40 are mounted on the first surface 301 of the substrate 30. As shown in
The element 41 is a switching element such as a MOS-FET. The sealing body 42 is made of resin such as epoxy resign in a rectangular plate shape. The sealing body 42 covers the whole of the element 41. The sealing body 42 includes a top surface 421, a bottom, surface 422, four side surfaces 423, 424, 425 and 426. The side surfaces 423 and 424 are opposite to each other. The side surfaces 425 and 426 are opposite to each other.
The longitudinal length (the length in the longitudinal direction) of the side surfaces 423 and 424, that is, the distance between the side surface 425 and the side surface 426 is w1. The longitudinal length of the side surfaces 425 and 426, that is, the distance between the side surface 423 and the side surface 424 is w2. The length w1 is greater than the length w2. Accordingly, the top surface 421 and the bottom surface 422 have a rectangular shape.
The terminals 43 are made of conductive material such as iron-nickel alloy or copper. Each terminal 43 is embedded in the sealing body 42 such that one end thereof is exposed from the side surface 425 or 426. A part of each terminal 43 is eclectically connected to the element 41. Another part of each terminal 43 is solder-connected to a printed wire on the first surface 301 of the substrate 30.
As shown in
The rotation angle sensor 12 is mounted on the first surface 301 of the substrate 30 so as to be located at a position opposite the magnet 8. The rotation angle sensor 12 detects a. rotational position of the rotor 6 by detecting the flux of the rotating magnet 8, and transmits a signal indicating the detected position to the microcomputer 11. The microcomputer 11 controls the rotation of the rotor 6 based on the rotation angle of the rotor 6 detected by the rotation angle sensor 12, the signal transmitted from a torque sensor fitted to the steering shaft and a signal indicating a vehicle speed.
When the rotor 6 rotates, a torque is outputted from the pulley 7 of the shaft 5. This torque is inputted to a not shown rack gear to assist. the steering operation of a vehicle driver. When the motor 1 rotates, that is, when the electronic components 40 operate, a large current flows to each of them, as a result of which the electronic components 40 generate heat. The heat dissipation gel 50 includes silicone resin as base material. The heat dissipation gel 50 contains granular filler made of aluminum oxide or the like.
The heat dissipation gel 50 is disposed between each electronic component 40 and the first surface 201 of the heat sink 20. The heat dissipation gel 50 is in contact with the top surface 421, the side surfaces 423, 424, 425 and 426 of the sealing body 42, the first surface 301 of the substrate 30 and the first surface 210 of the heat sink 20. The heat generated by the electronic component 40 while it operates is transmitted to the heat sink 20 to be dissipated.
Next, a method of manufacturing the electronic unit 10 is explained. This method includes a side surface coating step and a top surface coating step. In the side surface coating step and the top surface coating step, each electronic component 40 and the substrate 30 are coated with the heat dissipation gel 50 using a coating apparatus 60. As shown in
The nozzle 71 is made of metal in a cylindrical shape. The nozzle 71 is formed with an opening 711 at its one end surface (the first end surface hereinafter). As shown in
The feed section 91 stores therein the heat dissipation gel 50. The pipe 92 connects between the feed section 91 and the nozzle 71. The feed section 91 is capable of sending the heat dissipation gel 50 to the inside of the nozzle 71 through the pipe 92 so that the heat dissipation gel 50 can be discharged from the opening 711 of the nozzle 71.
The control section 93 is comprised of a microcomputer including a CPU, a memory storage such as ROM and RAM, and an I/O interface. The control section 93 controls the operations of the driving section 81 and the feed section 91 in accordance with programs stored in the ROM.
The control section 93 is capable of controlling the operation of the driving section 81 to change the position of the nozzle 71 relative to the electronic component 40 and the substrate 30. Also, the control section 93 is capable of controlling the amount of the heat dissipation gel 50 sent from the feed section 91 to control the amount of the heat dissipation gel 50 discharged from the opening 711 of the nozzle 71. The base 94 has a plane 941 parallel to the x-y plane.
The method of manufacturing the electronic unit 10 includes a component mounting step to be performed before the side surface coating step and the top surface coating step. In the component mounting step, the electronic component 40 is placed at predetermined positions such that the bottom surface 422 of the sealing body 42 is opposite to the first surface 301 of the substrate 30. Then, the terminals 43 of the electronic component 40 are soldered to a printed wire of the substrate 30.
Next, the side surface coating step and the top surface coating step are explained in detail. As shown in
The control section 93 controls the driving section 81 such that the longitudinal axis of the opening 711 of the nozzle 71 is parallel to the y-axis, and is located at a position corresponding to the side surface 423. Thereafter, the control section 93 controls the driving section 81 such that the nozzle 71 approaches the substrate 30.
Subsequently, the control section 93 causes the feed section 91 to send the heat dissipation gel 50 to discharge the heat dissipation gel 50 from the opening 711 in a state in which the outer wall of the end portion on the side of the opening 711 of the nozzle 711 abuts against the side surface 423 of the sealing body 42, and the opening of the nozzle 71 is apart from the substrate 30 by a predetermined. distance (see
In the following, a portion of the heat dissipation gel 50 which is coated on the side surface 423 is called “the side surface corresponding portion 51” as a matter of convenience. The longitudinal length gw1 of the side surface corresponding portion 51 is equal to the longitudinal length w1 of the side surface 423. The transverse length gw2 of the side surface corresponding portion 51 is equal to the transverse length of the end part on the side of opening 711 of the nozzle 71. The control section 93 causes the nozzle 71 to move in the z-axis direction, that is, causes the nozzle 71 to move away from the substrate 30 while the heat dissipation gel 50 is being discharged from the opening 711 with the outer wall of the nozzle 71 abutting against the side surface 423.
The control section 93 stops the heat dissipation gel 50 from being discharged from the nozzle 71 at a time when the height of the side surface corresponding portion 51 from the substrate 30 becomes equal to the plate thickness of the sealing body 42. As a result, the side surface corresponding portion 51 has a rectangular shape whose longitudinal axis is parallel to the side surface 423 (see
Subsequently, the control section 93 causes the feed section 91 to send the heat dissipation gel 50 for discharging the heat dissipation gel 50 from the opening 711 in a state in which the outer wall of the end part on the side of the opening 711 of the nozzle 711 abuts against the side surface 424 of the sealing body 42, and the opening 711 is away from the substrate 30 by a predetermined distance (see
In the following, a portion of the heat dissipation gel 50 that is coated on the side surface 424 is called “the side surface corresponding portion 52” as a matter of convenience. The longitudinal length gw1 of the side surface corresponding portion 52 is equal to the longitudinal length w1 of the side surface 423. The transverse length gw2 of the side surface corresponding portion 52 is equal to the transverse width of the end part on the side of opening 711 of the nozzle 71. The control section 93 causes the nozzle 71 to move in the z-axis direction, that is, causes the nozzle 71 to move away from the substrate 30 while the heat dissipation gel 50 is being discharged from the opening 711 with the outer wall of the nozzle 71 abutting against the side surface 424.
The control section 93 stops the heat dissipation gel 50 from being discharged from the nozzle 71 at a time when the height of the side surface corresponding portion 52 from the substrate 30 becomes approximately equal to the plate thickness of the sealing body 42. As a result, the side surface corresponding portion 52 has a rectangular shape whose longitudinal axis is parallel to the side surface 424 (see
Next, the top surface coating step is explained. The top surface coating step includes a first other side surface coating step and a second other side surface coating step. In the first other side surface coating step, the heat dissipation gel 50 is coated on the side surface 425. In the second other side surface coating step, the heat dissipation gel 50 is coated on the side surface 426.
First, the first other side surface coating step is explained. As shown in
In the following, a portion of the heat dissipation gel 50 that is coated on the side surface 425 is called “the side surface corresponding portion 53” as a matter of convenience. The longitudinal length gw3 of the side surface corresponding portion 53 is equal to the sum of the longitudinal length w2 of the side surface 425, the transverse length gw2 of the side surface corresponding portion 51 and the transverse length gw2 the side surface corresponding portion 52. The transverse length gw4 of the side surface corresponding portion 53 is equal to the transverse width of the end part on the side of opening 711 of the nozzle 71. That is, in this embodiment, the longitudinal length gw3 of the side surface corresponding portion 53 is equal to the longitudinal length gw1 of the side surface corresponding portions 51 and 52, and the transverse length gw4 of the side surface corresponding portion 53 is equal to the transverse length gw2 of the side surface corresponding portions 51 and 52.
The control section 93 causes the nozzle 71 to move in the z-axis direction, that is, causes the nozzle 71 to move away from the substrate 30 while the heat dissipation gel 50 is being discharged from the opening 711 with the outer wall of the nozzle 71 abutting against the side surface 425. At this time, the side surface corresponding portion 53 and the side surface corresponding portions 51 and 52 are integrated to one another. The first other side surface coating step is finished at this point in time.
As shown in
As a result, the heat dissipation gel 50 is coated on the side surface corresponding portions 51 and 52 and the top surface 421 of the sealing body 42 (see
As shown in
As a result, the thickness gt1 of the top surface corresponding portion 54 at the position corresponding to the center of the sealing body 42 becomes larger than the thickness gt2 of the top surface corresponding portion 54 at the position corresponding to the both ends of the sealing body 42, that is, at the position corresponding to the ends on the sides of the side surface 425 and the side surface 426 (see
Next, a second other surface coating step is explained. As shown in
Subsequently, the control section 93 causes the feed section 91 to send the heat dissipation gel 50 for discharging the heat dissipation gel 50 from the opening 711 in a state in which the outer wall of the end part on the side of the opening 711 of the nozzle 71 abuts against the side surface 426 of the sealing body 42, and the opening 711 is away from the substrate 30 by a predetermined distance (see
In the following, a portion of the heat dissipation gel 50 that is coated on the side surface 426 is called “the side surface corresponding portion 55” as a matter of convenience. The longitudinal length gw3 of the side surface corresponding portion 55 is equal to the sum of the longitudinal length w2 of the side surface 426, the transverse length gw2 of the side surface corresponding portion 51 and the transverse length gw2 of the side surface corresponding portion 52. The transverse length gw4 of the side surface corresponding portion 55 is equal to the transverse width of the end part on the side of opening 711 of the nozzle 71. That is, in this embodiment, the longitudinal length gw3 of the side surface corresponding portion 55 is equal to the longitudinal length gw1 of the side surface corresponding portions 51 and 52, and the transverse length gw4 of the side surface corresponding portion 55 is equal to the transverse length gw2 of the side surface corresponding portions 51 and 52.
The control section 93 causes the nozzle 71 to move in the z-axis direction, that is, causes the nozzle 71 to move away from the substrate 30 while the heat dissipation gel 50 is being discharged from the opening 711 with the outer wall of the nozzle 71 abutting against the side surface 426. The side surface corresponding portions 55 and 51 integrally connect with the side surface connecting part 52 and the top surface corresponding portion 54.
The control section 93 stops the heat dissipation gel 50 from being discharged from the nozzle 71 at a time when the height of the side surface corresponding portion 55 from the substrate 30 becomes equal to approximately twice the plate thickness of the sealing body 42. As a result, the side surface corresponding portion 55 has a rectangular shape whose longitudinal axis is parallel to the side surface 426 (see
As shown in
The method of manufacturing the electronic unit 10 also includes a radiator pressing step. The radiator pressing step is explained in the following. As shown in
(1) As explained above, the above described method of manufacturing the electronic unit 10 that includes the electronic component 40 having a rectangular plate shape and generating heat during operation and the heat dissipation gel 50 covering the electronic component 40 includes the side surface coating step and the top surface coating step.
In the side surface coating step, the heat dissipation gel 50 is discharged from the opening 711 having a flat rectangular shape of the nozzle 711 to coat the opposite side surfaces 423 and 424 with the heat dissipation gel 50. In the top surface coating step after the side surface coating step, the heat dissipation gel 50 is discharged from the opening 711 to coat the top surface 421 of the electronic component with the heat dissipation gel 50.
In each of the side surface coating step and the top surface coating step, since the opening 711 from which the heat dissipation gel 50 is discharged is flat-shaped, it is possible to prevent different portions of the heat dissipation gel 50 injected from the opening 71 of the nozzle 71 from contacting at their interfaces. Accordingly, it is possible to prevent formation of roll-in voids in the discharged heat dissipation gel 50. As a result, since the heat dissipation property of the electronic component 40 increases, the electronic unit 10 can be formed in a single substrate to thereby downsize the electronic unit 10.
Compared to the prior art in which heat dissipation gel is discharged from a small diameter circular opening of a nozzle while spirally moving the nozzle, the coating time can be reduced according to the above described embodiment because the heat dissipation gel is discharged from the flat opening 711. Therefore, according to the above described manufacturing method, it is possible to manufacture a small-sized. electronic unit including an electronic component having high heat dissipation property in a short time.
(2) In the above described embodiment, the electronic unit 10 further includes the substrate 30 disposed on the side opposite to the top surface 421 of the electronic component 40. In the side surface coating step, the heat dissipation gel 50 is coated on the boundary between the substrate 30 and the opposite side surfaces 423 and 424 (see
(3) In the side surface coating step and the top surface coating step, the heat dissipation gel 50 is coated on the boundary between the substrate 30 and all the four side surfaces 423, 224, 425 and 426 of the electronic component 40 (see
(4) In the side surface coating step and the top surface coating step, the outer wall of the end part on the side of the opening 711 of the nozzle 71 is caused to abut against the sealing body 42 of the electronic component 40 at the time of coating the heat dissipation gel 50 on the boundary between the substrate 30 and the side surfaces 423, 424, 425 and 426 of the electronic component 40. This makes it possible to maintain the distance between the opening 711 and the boundary approximately the same as the plate thickness of the nozzle 71. As a result, the heat dissipation gel 50 can be coated uniformly on the boundary between the substrate 30 and the side surfaces 423, 424, 425 and 426.
(5) The transverse length d2 of the opening 711 of the nozzle 71 is larger than twice the plate thickness t of the end part on the side of the opening 711 of the nozzle 71 (see
(6) The longitudinal length d1 of the opening 711 of the nozzle 71 is smaller than the longitudinal length w1 of the opposite side surfaces 423 and 424 (see
(7) In the side surface coating step, the heat dissipation gel 50 is discharged from the opening 711 of the nozzle 71 such that its width does not exceed the longitudinal length w1 of the opposite side surfaces 423 and the 424 (see
(8) In the top surface coating step, the heat dissipation gel 50 is discharged at a width which is smaller than the sum of the distance w2 between the opposite side surfaces 423 and 424 of the sealing body 42 of the electronic component 40 and the width gw2 of the side surface corresponding portions 51 and 52 (see
(9) In the top surface coating step, the heat dissipation gel 50 is discharged such that the thickness gt1 thereof at the position corresponding to the center of the sealing body 42 of the electronic component 40 is smaller than the thickness gt2 thereof at the position corresponding to the both end parts of the sealing body 42 of the electronic component 40, that is, the end parts on the side of the side surface 425 and the side of the side surface 426 (see
Next, a method of manufacturing the electronic unit 10 according to a second embodiment of the invention is described with reference to
In the second embodiment, the opening 711 of the nozzle 71 has a flat circular shape, that is, an oval shape as shown in
Except for the above, the second embodiment is the same as the first embodiment.
As explained above, in the second embodiment, the heat dissipation gel 50 is discharged from the flat opening 711 to coat the electronic component 40 and the substrate 30 as in the first embodiment. Like the first embodiment, according to the second embodiment, it is possible to prevent formation of roll-in voids in the heat dissipation gel 50 having been discharged and to reduce the coating time.
Next, a method of manufacturing the electronic unit 10 according to a third embodiment of the invention is described with reference to
The nozzle 72 is made of metal in a cylindrical shape of a rectangular cross section. The nozzle 72 is formed with an opening 721 at its one end surface. As shown in
The pipe 95 connects between the feed section 91 and the nozzle 72. The feed section 91 is capable of sending the heat dissipation gel 50 to the inside of the nozzle 72 through the pipe 95 so that the heat dissipation gel 50 can be discharged from the opening 721 of the nozzle 72.
The control section 93 is capable of controlling the operation of the driving section 82 to change the position of the nozzle 72 relative to the electronic component 40 and the substrate 30. Also, the control section 93 is capable of controlling the amount of the heat dissipation gel 50 sent from, the feed section 91 to control the amount of the heat dissipation gel 50 discharged from the opening 721 of the nozzle 72.
In the third embodiment, the heat dissipation gel 50 is discharged from the nozzle 71 to coat the side surfaces 423 and 424 of the sealing body 42 of the electronic component 40 with the heat dissipation gel 50. In the top surface coating step, the heat dissipation gel 50 is discharged from the nozzle 72 to coat the side surface 425, the top surface 421 and. the side surface 426 of the sealing body 42 with the heat dissipation gel 50. Accordingly, unlike in the first embodiment, it is not necessary to turn the nozzle 71 between the side surface coating step and the top surface coating step. Since the top surface coating step can be started immediately after the side surface coating step is finished, the coating time of the heat dissipation gel 50 can be further reduced.
In the above embodiments, the sealing body 42 of the electronic component 40 is formed in a rectangular plate shape. However, the sealing body 42 of the electronic component 40 may be formed in a square plate shape.
The outer wall of the end part on the side of the openings 711 or 721 may not be caused to abut against the sealing body 42 of the electronic component 40 at the time of coating the heat dissipation gel 50 on the boundary between the substrate 30 and the side surface s 423, 424, 425 and 426 of the sealing body 40. One of the first other surface coating step and the second other surface coating step may be omitted. The opening of the nozzle can have any arbitrary shape as long as it is flat. The ratio of the transverse length of the opening of the nozzle to the plate thickness of the end part on the side of the opening of the nozzle may have any value.
In the above embodiments, the longitudinal length of each of the opening 711 or 712 is 10 to 15 times the transverse length thereof. However, the longitudinal length is not limited thereto. The longitudinal length may be 2 to 10 times the transverse length, for example. The above embodiments are related to manufacturing the electronic unit 10 of the motor 1 for an electric power steering apparatus. It should be noted that the present invention can be used for manufacturing an electronic unit for controlling operation of an electric part of any apparatus.
The above explained preferred embodiments are exemplary of the invention of the present application which is described solely by the claims appended below. It should be understood that modifications of the preferred embodiments may be made as would occur to one of skill in the art.
Number | Date | Country | Kind |
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2016-029735 | Feb 2016 | JP | national |