Floating heat sink power control device

Abstract

A power control device comprising: an electronic board to which power electronic components are soldered; a housing defining an internal compartment suitable for housing said electronic board, said housing comprising a wall having: an external surface suitable for dissipating heat to the outside of the housing, an internal surface; means for securing said board to said housing; a heat sink secured to said housing, said heat sink comprising at least a first contact surface intended to be thermally connected to said internal surface of said housing, and at least a second contact surface intended to bear against at least one contact surface of said power electronic components; said heat sink being mounted freely in translation relative to said electronic board along the plane of said second surface of said heat sink. Fig. 1

Description

Title of the invention: Floating heat sink power control device 1. Scope of the invention

[0001] The field of the invention is that of the design and manufacture of controller devices, in particular those implemented in portable tools such as screwdrivers, drills... 2. Prior art

[0002] Screwing or drilling devices classically include a controller.

[0003] These controllers possess the intelligence and power enabling the tool, which is connected to it, to perform an operation (i.e. a screwing or drilling cycle) according to the programmed strategies.

[0004] The electrical power delivered by these controllers generates heat which must be dissipated in order to comply with standards and not exceed the temperature limits allowed by the electronic components.

[0005] To achieve the productivity objectives related to the industrial context in which they operate, controllers must enable the maximum number of operations to be performed in the minimum amount of time. The ability of these controllers to dissipate heat quickly is an essential element to ensure a sufficient rate of operations.

[0006] Two technologies are commonly implemented to ensure the removal of calories produced by the controllers.

[0007] According to a first technique, the controller housing contains a heat sink against which the controller's power transistors, soldered onto a circuit board, rest. This heat sink further comprises a surface equipped with cooling fins swept by air forced to circulate along the fins by means of a fan. The hot air resulting from the cooling of the heat sink remains inside the housing before being expelled through its walls.

[0008] According to a second technique, the power transistors are housed in a module and have a surface that is in contact, via a thermal conduction paste, with a wall of the controller housing. The module includes spring-loaded contacts connected to the leads of the power transistors. The electronic board includes traces against which the spring-loaded contacts bear to make electronic contact. The heat is thus directly dissipated through the wall of the controller housing.

[0009] Although relatively effective in cooling controllers, these techniques can still be improved.

[0010] In particular, it has been observed that these techniques could induce deformation of the electronic board generally due to hyperstaticity between the electronic board and the heat dissipation means.

[0011] Furthermore, the technique involving the use of a cooling fan is particularly disadvantageous since such a fan requires maintenance campaigns that tend to negatively impact productivity. In addition, the fan is a component that takes up a significant amount of space inside the controller housing, thus compromising the overall compactness of the controller.

[0012] The technique using a module is also disadvantageous insofar as the connection between the spring connectors and the card is made by contact, which can sometimes impair good electronic connectivity.

[0013] Furthermore, once the power transistors are attached to the circuit board, it is sometimes difficult to install the heat sink on the circuit board due to variations in transistor placement from one board to another. This can lead to damage to the components during heat sink installation and / or the need to remove and reposition the transistors before resoldering them. This obviously has a negative impact on the production cost of the controllers.

[0014] There is therefore a need to improve the design and manufacture of controllers. 3. Objectives of the invention

[0015] The invention aims in particular to provide an effective solution to at least some of these different problems.

[0016] In particular, according to at least one embodiment, an objective of the invention is to provide a controller that is efficient in terms of heat dissipation.

[0017] In particular, the invention aims, according to at least one embodiment, to provide such a controller which is simple and economical to manufacture.

[0018] Another objective of the invention is, according to at least one embodiment, to provide such a controller which is reliable.

[0019] In particular, the invention aims, according to at least one embodiment, to provide such a controller which requires little maintenance.

[0020] The invention also aims, according to at least one embodiment, to provide such a controller whose thermal dissipation means do not induce deformation of the electronic board. 4. Presentation of the invention

[0021] To this end, the invention proposes a power generation device comprising: - an electronic board to which electronic components are soldered power ; - a housing defining an internal compartment suitable for housing said electronic card, said housing comprising a wall having: - an external surface capable of dissipating heat to the outside of the case, and - an internal surface; - means of securing said electronic card to said casing; - a heat sink attached to said housing, said heat sink comprising at least a first contact surface intended to be thermally connected to said internal surface of said housing, and at least a second contact surface intended to bear against at least one contact surface of said power electronic components.

[0022] According to the invention, said heat sink is mounted freely in translation relative to said electronic board along the plane of said second surface of said heat sink.

[0023] Thus, the heat sink is free in translation along an axis orthogonal to the card to prevent the card assembly from being hyperstatic and consequently limit the risk of card deformation and damage to it.

[0024] According to one possible feature, said heat sink includes at least one receiving portion of at least one reversible fastening means of said heat sink to said electronic board, said at least one receiving portion being capable of cooperating with said at least one reversible fastening means, during the soldering of said power components to said board, in such a way that said contact surface of said power electronic components is in contact with said second surface of said heat sink.

[0025] Thus, it is possible to temporarily attach the electronic board to the heat sink before soldering the power electronic components to the board. In this way, the heat sink, against which the electronic components will rest, is used as a soldering jig, ensuring optimal positioning of the electronic components during soldering. Then, once the components have been soldered, the heat sink is detached from the board, and the board and heat sink are then attached to the enclosure. The heat sink is then free to move along an axis perpendicular to the board. This prevents the board attachment from becoming over-static and consequently limits the risk of board deformation and damage.

[0026] According to one possible feature, said second surface of said heat sink extends essentially orthogonally to said wall of said housing, said electronic board being intended to extend parallel to said wall and said contact surface of said power electronic components to extend parai- element to the said second surface of said heat sink.

[0027] According to one possible feature, said contact surface of said power electronic components comes into contact with said second surface of said heat sink in a direction parallel to said wall of said housing.

[0028] According to one possible feature, a device according to the invention comprises thermal bonding means between said internal surface of said housing and said first surface of said heat sink, said thermal bonding means extending substantially orthogonally to said electronic board, said electronic board being traversed by perforations allowing the passage of said thermal bonding means.

[0029] According to one possible feature, said thermal bonding means comprise first protrusions and / or second protrusions, said internal surface of said housing being carried by said first protrusions extending towards said electronic board and / or said first surface of said heat sink comprising said second protrusions extending towards said internal surface, said electronic board being traversed by perforations allowing the passage of said first and / or said second protrusions, the ends of said first and / or second protrusions being respectively in thermal contact with said heat sink or said housing or with each other, either directly or via thermal sheet(s).

[0030] According to one possible feature, the length of said second protrusions of said heat sink is chosen such that said second protrusions of said heat sink extend inside said perforations of said electronic board, when said heat sink is attached to said board, without protruding outside said perforations on the side of said board opposite to that where said heat sink is located.

[0031] According to one possible feature, a device according to the invention includes clipping means configured to hold said contact surface of said power electronic components against said second surface of said heat sink.

[0032] According to one possible feature, a device according to the invention comprises thermal sheets arranged between said second surface of said heat sink and said contact surface of said power electronic components.

[0033] According to one possible feature, said housing and said heat sink are made of aluminum alloy.

[0034] The invention also covers a screwing or drilling tool comprising a device according to any of the above variants.

[0035] The invention also covers a method for assembling a control device of power according to any one of the above variants, said process comprising: - a step of temporarily securing said heat sink to said electronic board by means of said reversible securing means; - a step of placing said power electronic components on said electronic board in such a way that said contact surface of said electronic components is in contact with said second surface of said heat sink; - a soldering step of said power electronic components onto said electronic board; - a step of detaching said heat sink from said card by deactivating said reversible fastening means; - a step of securing said electronic card to said housing; - a step of securing said heat sink to said housing.

[0036] According to one possible feature, said step of placing said power electronic components on said electronic board includes a step of holding said contact surface of said components against said second surface of said heat sink by clipping.

[0037] According to one possible feature, said step of detaching said heat sink from said card by deactivating said reversible fastening means is preceded by a step of placing said electronic card and said heat sink together in said housing. 5. Description of the figures

[0038] Other features and advantages of the invention will become apparent from the following description of particular embodiments, given by way of simple illustrative and non-limiting example, and the accompanying drawings, among which:

[0039] [Fig-1] [Fig.1] illustrates a perspective view of a control device according to the invention whose lid is disassembled;

[0040] [Fig.2] [Fig.2] illustrates a detailed view centered on the heat sink of the device in [Fig.1];

[0041] [Fig.3] [Fig.3] illustrates a cross-sectional view of the assembly of a device according to the invention;

[0042] [Fig.4] [Fig.4] illustrates a top view of the assembly of a device according to the invention;

[0043] [Fig.5] [Fig.5] illustrates a partial perspective view from below of the assembly of an electronic board and a heat sink of a device according to the invention;

[0044] [Fig.6] [Fig.6] illustrates a partial perspective view from below of the assembly of an electronic board with the power electronic components installed before soldering, and of a heat sink of a device according to the invention;

[0045] [Fig.7] [Fig.7] illustrates a partial cross-sectional view of the assembly of a of an electronic board and a heat sink according to the invention.

[0046] 6. Description of particular embodiments 6.1. Architecture

[0047] An example of a power control device according to the invention is presented in relation to Figures 1 to 7.

[0048] Such a power control device, also called a controller, can be connected to an electric tool, such as for example a screw-driving device or a drilling device.

[0049] As shown in the figures, such a power control device comprises a housing 10.

[0050] This housing 10 comprises a plurality of walls which delimit an internal housing 11.

[0051] In the illustrated embodiment, the housing has a parallelepiped shape. It then comprises four side walls 100, a bottom or base wall 101, and a removable lid not shown.

[0052] Of course, the case could have any other shape.

[0053] The lower wall 101 has: - an external surface 1011 capable of dissipating heat to the outside of the case 10, and - an internal surface area of ​​1012.

[0054] The internal housing 11 is suitable for housing an electronic card 12. In [Fig. 1], this electronic card is shown housed in this internal housing.

[0055] This electronic card 12 carries among other things power electronic components 120 such as transistors or other.

[0056] These power electronic components are arranged orthogonally to the electronic board with their pins passing through the printed circuit board. This avoids having to bend the pins of the power components to position them parallel to the board, resulting in increased productivity. It also improves the board's footprint.

[0057] The electronic board 12 can also carry other electronic components, which can be surface-mount components or traditional components (in the sense that they pass through the printed circuit board). The power electronic components and the other traditional components are arranged on the same side of the board so that they can be wave soldered. This soldering method is efficient in terms of productivity.

[0058] The card is therefore housed in the internal compartment 11 as close as possible to the internal surface 1012 of the lower wall 101, the electronic components being arranged towards the inside of the case 10. This arrangement allows for a more compact design.

[0059] The device includes means for securing the electronic card 12 to the housing 10.

[0060] In this embodiment, these fastening means include screws (not shown) which pass through holes 121 through the electronic board 12 and are screwed into threaded portions (not shown) provided on the internal surface 1012 of the lower wall 101.

[0061] A planar contact is ensured between the electronic card 12 and the lower wall 101 blocking the following degrees of freedom according to the trigonometric frame represented on [Fig.1], whose axes X and Y extend in the plane of the lower wall 101 and the Z axis is orthogonal to the plane of the lower wall 101: - translation along the Z axis; - rotations around the X and Y axes.

[0062] A tenon 1013 projects from the inner surface 1012 of the lower wall 101 towards the internal housing 11 along the Z-axis. This tenon 1013 passes through a complementaryly shaped orifice 122 formed through the electronic board 12 when the board is attached to the housing. The interaction of this tenon 1013 and this orifice 122 restricts the following degrees of freedom: - translations along the X and Y axes; - rotation about the Z-axis.

[0063] In this way, the electronic card 12 is attached to the housing 10, in this case to the internal surface 1012 of the lower wall 101, in an isostatic manner.

[0064] In variants, the electronic card 12 could be attached to any other wall of the housing 10 than the bottom wall 101 provided that the wall to which it is attached includes an external surface capable of dissipating heat to the outside of the housing 10.

[0065] The external surface 1011 may be essentially flat or may have fins 1013 to maximize the exchange surface with the air outside the housing and thus improve the evacuation of heat outside the housing.

[0066] The device includes a heat sink 13 attached to the housing 10.

[0067] This heat sink 13 comprises: - at least one first contact surface 130 intended to be thermally connected to the internal surface 1012 of the lower wall 101 of the housing 10, and - at least one second contact surface 131 intended to bear against at least one contact surface 1200 of the power electronic components 120.

[0068] In this embodiment, the second surfaces 131 of the heat sink 13 extend essentially orthogonally to the wall of the housing 10 with which the heat sink is thermally connected, i.e., here the lower wall 101. Furthermore, the electronic board extends parallel to the wall of the housing 10 with which the heat sink is thermally connected, i.e., here the lower wall 101. Also, the contact surface 1200 of the power electronic components 120 extends parallel to the second surfaces 131 of the heat sink 13. This allows the power electronic components 120 to be arranged on the board without bending their pins.

[0069] The contact surface 1200 of the power electronic components 120 comes into contact with the second surfaces 131 of the heat sink 13 in a direction parallel to the wall of the housing 10 with which the heat sink is in thermal contact, i.e. here the lower wall 101.

[0070] The device includes means for fixing the heat sink 13 to the housing 10. These fixing means include screws 14 which pass through holes 132 through the heat sink 13 and are screwed into tapped holes 1014 provided in the lower wall 101.

[0071] The internal surface 1012 of the housing 10 and the first surface 130 of the heat sink 13 can be in direct contact or via thermal sheets.

[0072] However, in this embodiment, the device includes thermal bonding means between the internal surface 1012 of the housing 10 and the first surface 130 of the heat sink 13. These thermal bonding means extend substantially orthogonally to the electronic board 12, the electronic board 12 being traversed by perforations 123 allowing the passage of the thermal bonding means.

[0073] More specifically, in this embodiment, these thermal bonding means comprise first protrusions 1015 and second protrusions 133.

[0074] The internal surface 1012 of the housing 10 includes the first protrusions 1015 which extend towards the electronic card 12.

[0075] The first surfaces 130 of the heat sink 13 are supported by the second protrusions 133 which extend towards the internal surface 1012.

[0076] The perforations 123 of the electronic card 12 allow the passage of the first 1015 and / or the second 133 protrusions.

[0077] The ends of the first 1015 and second 133 protrusions are respectively in thermal contact with each other, either directly or through thermal sheet(s) 18.

[0078] In variants, only the first protrusions will be implemented and will be in contact with the first contact surfaces of the heat sink directly or via thermal sheets.

[0079] In variants, only the second protrusions will be implemented and will be in contact with the internal surface of the housing wall with which the heat sink comes into contact, either directly or via thermal sheets.

[0080] Preferably, the device includes clips 15 configured to hold the contact surface 1200 of the power electronic components 120 against the second surface 131 of the heat sink 13.

[0081] According to one possible feature, thermal sheets not shown are arranged between the second surface 131 of the heat sink 13 and the contact surface 1200 of the power electronic components 12.

[0082] The housing 10 and the heat sink 13 are preferably made of aluminum alloy.

[0083] Thermal sheets can be made of a thermally conductive material (for example, graphite). They can also be replaced by elements made of a thermally conductive filling material (for example, silicone or polymers), known as "thermal pads" or "gap fillers".

[0084] The heat sink 13 includes at least one and preferably several (for example two) receiving portions 134 of at least one reversible means of securing the heat sink 13 to the electronic board 12.

[0085] The reversible fastening means may be, for example, a screw 16. In this case, the receiving portion will include a hole for the passage of each screw.

[0086] As will be described in more detail later in connection with the description of a method for assembling a device according to the invention, these receiving portions 134 are capable of: - cooperate with the screws 16, during the brazing of the power components 120 to the board 12, in such a way that the contact surface 1200 of the power electronic components 12 is in contact with the corresponding second surface 131 of the heat sink 13: - not to cooperate with any of the screws, after brazing the power components 120 to the electronic board 12 and after securing the heat sink 13 to the housing 10, the heat sink 13 then being mounted freely in translation relative to the electronic board 12 along the plane of the second surface 131 of the heat sink 13.

[0087] When the electronic board 12 is attached to the housing 10 and the heat sink 13 is attached to the housing 10, but the electronic board 12 and the heat sink 13 are not secured to each other by means of the screws 16, then there is play between the heat sink 13 and the board 12, which are not in contact with each other. with the other. The lack of contact results from: - the implementation of the perforations 123 of the electronic card 12 which induce the existence of a play along the X and Y axes between the heat sink and the card. - the existence of a game between card 12 and reception portions 134 along the Z axis.

[0088] Thus, the heat sink exerts no force on the electronic board and does not interfere with the isostatic attachment of the board to the housing.

[0089] Preferably, the length of the second protrusions 133 of the heat sink 13 is chosen such that the second protrusions 133 extend inside the perforations 123 of the electronic card 12, when the heat sink 13 is attached to the card 12, without protruding outside the perforations 123 on the side of the card opposite to that where the heat sink 13 is located.

[0090] This allows, when the heat sink 13 and the electronic board 12 are joined together, for more reliable wave soldering of the power electronic components onto the electronic board, since the ends of the second protrusions do not protrude on the side of the board where the soldering is performed. Indeed, because the heat sink does not protrude on the side of the board where the soldering is performed (or even preferably is recessed), it does not risk coming into contact with the tin wave during soldering. Therefore, it does not risk disrupting the thermal characteristics of the solder wave. 6.2. Assembly

[0091] The assembly of a device according to the invention is obtained in the following manner.

[0092] In a first step, the heat sink 13 is temporarily secured to the electronic card 12 by means of reversible fastening means. For this purpose, screws 16 are passed through the receiving portions 134 which are drilled for this purpose by holes, and a nut (not shown) is screwed to the end of the screws 16, the tightening of which allows the card 12 to be clamped between the nuts and a flat contact surface, parallel to the plane of the card, of the receiving portions 134.

[0093] In a second step, the power electronic components 120 are placed on the electronic board 12 by inserting their legs into the holes provided for this purpose in the board and in such a way that the contact surface 1200 of the electronic components 120 is in contact with the corresponding second surface 131 of the heat sink 13.

[0094] Retaining clips 15 can be put in place so as to hold the contact surface 1200 of the components 120 against the corresponding second surface 131 of the heat sink 13.

[0095] In a third step, the power electronic components 120 are brazed to the wave on the electronic card 12.

[0096] During this soldering, no relative displacement between the electronic components and the heat sink is to be deplored because the heat sink provides the function of a soldering template.

[0097] In a fourth step, the heat sink 13 is detached from the board 12 by disabling the reversible fastening means, i.e., by removing the screws 16 and their nuts. If retaining clips 15 are used to hold the contact surface 1200 of the components 120 against the corresponding second surface 131 of the heat sink 13, they are removed.

[0098] In a fifth step, the electronic card 12 is attached to the housing 10.

[0099] To this end, the card 12 is inserted into the inner housing 11, the tenon 1013 is inserted into the hole 122 of the card 12, the holes 121 of the card 12 are aligned with the threaded portions (not shown) provided on the inner surface 1012 of the lower wall 101, and screws are inserted into the holes 121 and screwed into the threaded portions. The electronic card 12 is then isostatically secured to the housing 10.

[0100] In a sixth step, the heat sink 13 is attached to the housing 12.

[0101] For this purpose, the second protrusions 133 are introduced into the perforations 123 of the card 12 until the first contact surfaces 130 of the heat sink 13 are in contact, either directly or via thermal sheets, with the ends of the first protrusions 1015 which form part of the inner surface 1012 of the lower wall 101 of the housing 10. The holes 132 of the heat sink 13 are placed in alignment with the tapped holes 1014 of the lower wall 101 of the housing 10. The screws 14 are inserted into the holes 132 and screwed into the holes 1014.

[0102] The electronic board 12 and the heat sink 13 are thus fixed to the housing 10 but are not fixed to each other, so that there is play between the heat sink 13 and the board 12, which are not in contact with each other. The lack of contact results in: - the implementation of the perforations 123 of the electronic card 12 which induce the existence of a play along the X and Y axes between the heat sink and the card. - the existence of a game between card 12 and reception portions 134 along the Z axis.

[0103] Thus, the heat sink exerts no force on the electronic board, in particular along the X axis perpendicular to the plane of the board, and does not interfere with the isostatic attachment of the board to the housing.

[0104] In one variant, the step of detaching the heat sink from the board by deactivation of the reversible fastening means is preceded by a step of installing, in the case, the electronic board and the heat sink fastened to each other.

[0105] The retaining clips 15 can be put back in place so as to maintain the contact surface 1200 of the components 120 against the corresponding second surface 131 of the heat sink 13. 6.3. Advantage

[0106] The technique according to the invention provides numerous advantages, including the following: - providing sufficient thermal efficiency through the direct dissipation of heat to the outside via an internal heatsink and the case which has a wall capable of dissipating heat, for example via fins. This is possible thanks to the passage of the internal heatsink through the card; - achieving controlled costs through the use of standard parts coupled with custom injection-molded parts and an optimized assembly process; - Reduced maintenance because the thermal system does not have a fan. Also, with this solution, the entire electronic board can be easily replaced.

[0107] The assembly process allows for an isostatic system, without placing any stress on the board or its components. This avoids any risk of deformation and damage to the board and its components. From a mechanical integration point of view, the assembly is therefore reliable.

Claims

Demands

1. Power control device comprising: - an electronic board to which power electronic components are brazed; - a housing delimiting an internal compartment suitable for housing said electronic board, said housing comprising a wall having: - an external surface suitable for dissipating heat to the outside of the housing, and - an internal surface; - means for securing said electronic board to said housing; - a heat sink secured to said housing, said heat sink comprising at least a first contact surface intended to be thermally connected to said internal surface of said housing, and at least a second contact surface intended to bear against at least one contact surface of said power electronic components;characterized in that said heat sink is mounted freely in translation relative to said electronic board along the plane of said second surface of said heat sink.;

2. Device according to claim 1 comprising at least one receiving portion of at least one reversible securing means for said heat sink to said electronic board, said at least one receiving portion being capable of cooperating with said at least one reversible securing means, during the soldering of said power components to said board, in such a way that said contact surface of said power electronic components is in contact with said second surface of said heat sink.

3. Device according to claim 1 or 2 wherein said second surface of said heat sink extends essentially orthogonally to said wall of said housing, said electronic board being intended to extend parallel to said wall and said contact surface of said power electronic components to extend parallel to said second surface of said heat sink.

4. Device according to any one of claims 1 to 3 in which said contact surface of said power electronic components comes into contact with said second surface of said heat sink in a direction parallel to said wall of said housing.

5. Device according to any one of claims 1 to 4 comprising thermal bonding means between said internal surface of said housing and said first surface of said heat sink, said thermal bonding means extending substantially orthogonally to said electronic board, said electronic board being traversed by perforations allowing the passage of said thermal bonding means.

6. Device according to claim 5 wherein said thermal bonding means comprise first protrusions and / or second protrusions, said internal surface of said housing being carried by said first protrusions extending towards said electronic board and / or said first surface of said heat sink comprising said second protrusions extending towards said internal surface, said electronic board being traversed by perforations allowing passage of said first and / or said second protrusions, the ends of said first and / or second protrusions being respectively in thermal contact with said heat sink or said housing or with each other, either directly or via thermal foil(s).

7. Device according to claim 6 wherein the length of said second protrusions of said heat sink is chosen such that said second protrusions of said heat sink extend inside said perforations of said electronic board, when said heat sink is attached to said board, without protruding outside said perforations on the side of said board opposite to that in which said heat sink is located.

8. Device according to any one of claims 1 to 7 comprising clipping means configured to hold said contact surface of said power electronic components against said second surface of said heat sink.

9. Device according to any one of claims 1 to 8 comprising thermal sheets disposed between said second surface of said heat sink and said contact surface of said power electronic components.

10. A device according to any one of claims 1 to 9, wherein said housing and said heat sink are made of alloy aluminum.

11. A screwing or drilling tool comprising a device according to any one of claims 1 to 10.

12. A method for assembling a power control device according to any one of claims 2 to 10 comprising: - a step of temporarily attaching said heat sink to said electronic board by means of said reversible attachment means; - a step of placing said power electronic components on said electronic board in such a way that said contact surface of said electronic components is in contact with said second surface of said heat sink; - a step of soldering said power electronic components to said electronic board; - a step of detaching said heat sink from said board by deactivating said reversible attachment means; - a step of attaching said electronic board to said housing; - a step of attaching said heat sink to said housing.

13. Assembly method according to claim 12 wherein said step of placing said power electronic components on said electronic board includes a step of retaining by clipping said contact surface of said components against said second surface of said heat sink.

14. Assembly method according to claim 11 or 12 wherein said step of decoupling said heat sink from said card by deactivation of said reversible fastening means is preceded by a step of placing said electronic card and said heat sink together in said housing.

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