Device comprising an electronic card and a capacitor connected to the electronic card

Abstract

The invention relates to a device comprising an electronic card (6) and a capacitor (1). The capacitor (1) comprises two terminals (3) which are connected to the electronic card (6), such that the capacitor (1) has an upper face substantially parallel to a lower face (7) of the electronic card (6). The electronic card (6) comprises a slot forming a through opening in said electronic card (6), and this slot is interposed between the two terminals (3) of the capacitor (1) and oriented to be intersecting with the axis connecting the two terminals (3) of the capacitor (1), the slot extending opposite the entire width of the capacitor (1). The device further comprises an electrically insulating element (9) in said slot and on the upper face (5) of the capacitor (1), the electrically insulating element (9) being interposed between the terminals (3) of the capacitor (1) over the entire width of the capacitor (1). figure for the abstract: figure 2

Description

Title of the invention: Device comprising an electronic card and a capacitor connected to the electronic card TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of electronic components, in particular power electronic components comprising capacitors carried by an electronic card or printed circuit.

[0002] One of the preferred applications of the present invention concerns electromagnetic compatibility filters, generally called EMC filters which make it possible to guarantee electromagnetic compatibility in equipment.

[0003] The inverters comprise such an EMC filter, so that the invention relates in particular to an inverter controlling a traction motor of an electric or hybrid vehicle. The invention has a particular application in an input filter of an inverter, namely an EMC filter called an EMI filter (according to the English acronym "Electro Magnetic Interference"), intended to avoid disturbances in the equipment connected to the power supply of the inverter. This is called filtering the power signal.

[0004] This application serves as support below for the description of the present invention, which is nevertheless applicable to numerous other applications, as soon as certain capacitors are used, and are linked to an electronic card. STATE OF THE ART

[0005] Capacitors are used in many electronic components, particularly when connected to an electronic card. An "electronic card" refers to any type of printed circuit, which is also commonly referred to as a "PCB" according to the acronym for the English expression "Printed Circuit Board".

[0006] Generally speaking, if a short circuit occurs between the terminals of a capacitor, this can cause significant damage to the capacitor and the electronic board, and also damage other parts of the component that includes the electronic board and the capacitors. Some protections can be considered, for example by providing a means of bypassing the leakage current when such a short circuit occurs.

[0007] These means may nevertheless be complex to implement or expensive, and it may be preferable to ensure that such a short circuit simply cannot occur, or at least to ensure that it is slowed down in order to allow time for the safety systems (for example a sensor or a circuit breaker) of the inverter to trigger and thus avoid a risk of a fire starting.

[0008] Some capacitors are in the form of a cubic, or more generally rectangular parallelepiped, shaped case.

[0009] The case is filled with a resin from which the capacitor terminals emerge. This type of configuration is particularly common for most plastic film capacitors. A plastic film capacitor is made of thin layers of insulating plastic used as a dielectric, often metallized, and encapsulated in a resin cast into the case.

[0010] Such a capacitor may be used, for example, as a class X capacitor (or an "X capacitor" according to the commonly used English expression), which is used in interconnection applications between power lines in electrical and electronic equipment. These capacitors make it possible to suppress or attenuate electromagnetic interference (EMI) or transient overvoltages which circulate on electrical power cables or bars.

[0011] Parallelepiped capacitors nevertheless have a disadvantage. When they are used in an application in which they are installed with their face from which the capacitor terminals emerge facing upwards, horizontally or with a slight inclination, water, for example from the condensation of water present in the ambient air, can accumulate on this face. Indeed, a resin is poured into the capacitor housing through this initially open face of the housing, and polymerizes in the housing. The filling is often slightly incomplete, to avoid any overflow of the resin. Furthermore, even with complete filling, the surface tension forces between the resin and the housing create a capillary effect resulting in a slightly concave free surface of the resin.

[0012] If the terminals become connected by a film of water, the capacitor may become short-circuited. This is generally problematic, as explained above, and is even more so for a capacitor interposed between power conductors of a power electronics component. Statement of the invention

[0013] The present invention aims firstly to resolve this problem, and, more generally, to improve the insulation between the terminals of a capacitor connected to an electronic card.

[0014] To this end, the invention relates to a device comprising an electronic card and a capacitor. The capacitor comprises two terminals which are connected to the electronic card, so that the capacitor has an upper face substantially parallel to a lower face of the electronic card. A length of the capacitor is defined as being a dimension of the capacitor in the direction of an axis connecting the two terminals of the capacitor, measured parallel to the upper face of the capacitor, and wherein a width of the capacitor is defined as a dimension of the capacitor perpendicular to its length and measured parallel to the upper face of the capacitor. The electronic card comprises a slot forming a through opening in said electronic card, the slot being interposed between the two terminals of the capacitor and oriented to intersect with the axis connecting the two terminals of the capacitor, the slot extending opposite the entire width of the capacitor. The device further comprises an electrically insulating element in said slot and on the upper face of the capacitor, the electrically insulating element being interposed between the terminals of the capacitor over the entire width of the capacitor.

[0015] The present invention makes it possible to avoid any risk of short circuit between the terminals of the capacitor, by a simple and reliable mechanical means. The invention is of particular interest when the upper surface of the capacitor is horizontal or close to horizontal.

[0016] The electrically insulating element may be a bead of glue.

[0017] The concept of glue in this document also covers the concept of mastic of similar composition.

[0018] The glue may be a silicone-based glue.

[0019] The glue can be chosen from a polyurethane glue, a polysulfide-based glue, an epoxy glue, and an acrylic glue.

[0020] The slot may be perpendicular to the axis connecting the two terminals of the capacitor. The slot may be at an equal distance from each of the terminals.

[0021] A portion of the electrically insulating element may protrude from an upper face of the electronic card, opposite its lower face.

[0022] The electrically insulating element may extend on the upper face of the electronic card beyond an edge of the slot.

[0023] The upper face of the capacitor can be at a distance from the lower face of the electronic card.

[0024] The part of the electrical insulating element which protrudes from the upper face of the electronic card may have a height, measured perpendicular to said upper face of the electronic card, of between 0.5 mm and 8 mm, for example between 1 mm and 1.5 mm.

[0025] The slot may have a length measured in the plane of the upper surface of the electronic card in the direction of the largest dimension of the slot, between 5 mm and 50 mm.

[0026] The slot may have a width, measured in the plane of the upper surface of the electronic card in the direction of the smallest dimension of the slot, of between 0.5 mm and 6 mm.

[0027] The invention also relates to an electromagnetic compatibility filter comprising a device as described above. In such a filter, the capacitor may be an X-type capacitor.

[0028] The invention finally relates to an inverter comprising a device as described above. BRIEF DESCRIPTION OF THE FIGURES

[0029] Other advantages, aims and particular characteristics of the present invention will emerge from the following non-limiting description of at least one particular embodiment of the devices and methods which are the subject of the present invention, with reference to the appended drawings, in which: • [Fig.l] is a schematic perspective view of an example of a capacitor whose configuration may lead to a risk of short circuit which is addressed within the scope of the present invention; • [Fig.2] is a schematic sectional view of a device according to one embodiment of the invention; • [Fig.3] is a three-dimensional schematic view of the device of the [Fig.2] ; • [Fig.4] is a three-dimensional schematic view of a sub-assembly enabling the invention to be implemented; • [Fig.5] is a three-dimensional schematic sectional view of the device of figures 2 and 3; • [Fig.6] is a detail view of part of [Fig.2]. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present description is given as a non-limiting example of embodiment.

[0031] [Fig.l] represents a capacitor 1 of the plastic film type or the like, encapsulated in a resin contained in a casing 2. The casing 2 is substantially of rectangular parallelepiped shape. The casing 2 can be made of different materials, and can in particular be made of plastic. The capacitor has two terminals 3, which emerge from the resin 4 which has been cast in the casing 1 by an initially open face. This face, materialized by the edges of the casing 2, and by extension by the free surface of the resin 4, will be designated the upper face 5 of the capacitor.

[0032] After polymerization, the resin 4 is no longer liquid and the capacitor can be installed in any orientation. For various reasons, the configuration of the component which is to integrate this capacitor 1 may be such that the upper face 5 is oriented horizontally and upwards for most of the duration of use of the component, or with a slight slope to the horizontal direction. By slight slope, we mean less than 30° compared to the horizontal.

[0033] As can be seen in [Fig. 1], the free surface of the resin 4 is very slightly below the level of the upper face 5 of the capacitor 1. This avoids the risk of the resin overflowing during the manufacture of the capacitor 1. Thus, at the level of the upper face 5 in the best case there is a substantially flat surface, or a slight concavity, a slight “bathtub”. The humidity present in the air can condense in the form of liquid water, and this water can then stagnate at the level of the upper face of the capacitor 1, if its orientation does not allow evacuation by flow of this water.

[0034] According to a first aspect, the present invention aims to prevent water present on the upper face of the capacitor 1 from creating a short circuit between the two terminals 3, or, more generally, from a continuous wet film being able to form between said terminals 3.

[0035] As seen in [Fig.2] and [Fig.3], this goal is achieved in the following manner.

[0036] [Fig. 2] shows a sectional view of a device according to one embodiment of the invention.

[0037] According to the invention, the capacitor 1 is connected, by its terminals 3, to an electronic card 6. In particular, the terminals 3 are in the form of pins, and they pass through the card 6. Alternatively, the terminals can be soldered to the surface of the electronic card, using CMS technology for “surface mounted component”.

[0038] The electronic card 6 has a lower face 7 and an upper face 8. The capacitor 1 is installed on the side of the lower face 7 of the electronic card 6.

[0039] The electronic card and the capacitor are shown in [Fig. 2] according to the orientation in which they will be used during the majority of the use of the system which will be equipped with it. Thus, the electronic card 6 extends along a substantially horizontal plane. The upper face 5 of the capacitor is also substantially horizontal, which can promote the stagnation of water which would form there by condensation. In order to prevent water, for example in the form of a wet film, from being able to form between the two terminals 3, an electrical insulating element 9 is interposed between the terminals 3. In particular, the electrical insulating element 9 is formed on the upper face 5 of the capacitor, through a slot 10 formed in the electronic card 6.

[0040] As can be seen in Figures 3 and 4 described in more detail below, the electrical insulating element extends at least over the entire width 1 of the capacitor 1. In particular, the slot 10 extends opposite the entire width 1 of the capacitor 1, as this is visible in [Fig.5], so that the electrical insulating element can be placed through the slot 10 and can thus extend over this entire width 1.

[0041] The electrically insulating element may in particular be formed from an insulating glue or mastic. A bead of this electrically insulating material may be formed across the slot 10.

[0042] The glue may be a silicone-based glue. This type of glue has good adhesion properties on the upper surface of the capacitor and significant insulating properties, especially on the capacitor resin. Alternatively, a polyurethane glue, a polysulfide-based glue, an epoxy glue, or an acrylic glue can be used successfully. Corresponding sealants can also be used.

[0043] According to another aspect of certain embodiments of the invention, the upper face 5 of the capacitor is at a distance d from the lower face of the electronic card. This distance d allows air circulation between the electronic card 6 and the upper face 5 of the capacitor. Such air circulation allows better cooling of the capacitor 1, but also evaporation of the water which may have formed on the upper face 5 of the capacitor 1. The distance d also makes it possible to provide sufficient space to form the solder cones at the terminals.

[0044] The distance d is typically between 0.5 mm and 3 mm.

[0045] [Fig.3] represents the device of [Fig.2], according to a three-dimensional view showing the upper face 8 of the electronic card 6.

[0046] [Fig.4] shows a sub-assembly, comprising an electronic card 6 and a capacitor 1. The electronic card is configured so that the invention can be implemented, thanks to the slot 10, which extends along an axis B which is substantially perpendicular to the axis A which connects the two terminals 3 of the capacitor 1. The slot completely crosses the thickness of the electronic card, which allows access to the upper face 5 to form a bead of glue there as an electrical insulating element, or more generally, to fix such an electrical insulating element there, over at least the entire width 1 of the capacitor 1 and therefore of its upper face 5.

[0047] The slot, and therefore the electrical insulating element, is advantageously positioned at an equal distance from the terminals 4 of the capacitor 1. Generally, this amounts to forming the slot at half the length L of the capacitor.

[0048] It will be noted in this regard that when the electrical insulating element 9 is formed from an adhesive or a mastic, it would not be relevant to form the adhesive bead on the capacitor 1 before connecting it to the electronic card 6. This could indeed pose problems in positioning the capacitor before its connection by soldering. When the electrical insulating element 9 is formed from an adhesive or a mastic, it is therefore advantageously formed through the slot 10. It is for example introduced through of the slot 10 with a suitable delivery nozzle. Polymerization then occurs rapidly. Sufficient setting to allow further assembly of the component that will integrate the electronic card is obtained in a few minutes. Complete polymerization, which typically takes 24 hours, can continue without problem after assembly of the component.

[0049] As can be seen in particular in [Fig. 3], in this embodiment of the invention, once the electrical insulating element 9 is formed, it protrudes from the upper face 8 of the electronic card 6. The part of the electrical insulating element which protrudes from the upper face 8 of the electronic card thus forms an electrically insulating separation wall between the connection zones of the terminals 3 located on the upper face 8 of the electronic card. The creepage distance (shortest distance between two conductive elements, here the terminals of the capacitor) of the capacitor is increased. In general, this improves the electrical separation between the two terminals and the general safety of the component.

[0050] The glue also makes it possible to prevent water retention on both sides (on the lower face side and on the upper face side) of the electronic card.

[0051] The part of the electrical insulating element which protrudes from the upper face of the electronic card may have a height H, shown in [Fig.5] and [Fig.6], measured perpendicular to said upper face of the electronic card, of between 0.5 mm and 8 mm. The height H may typically be between 1 mm and 1.5 mm.

[0052] The length LO of the slot 10 may be between 5 mm and 50 mm. Furthermore, the length of the portion of the electrically insulating element which protrudes from the upper face 8 of the electronic card 6, measured in the plane of the upper surface of the electronic card in the direction of the length of the slot, may be greater than the length of the slot. For example, the electrically insulating element which protrudes from the upper face 8 of the electronic card 6 may have a length of 1 mm to 10 mm greater than that of the slot 10.

[0053] The width LA of the slot 10 may be between 0.5 mm and 6 mm. Furthermore, the width of the portion of the electrical insulating element which protrudes from the upper face 8 of the electronic card 6, measured in the plane of the upper surface of the electronic card in the direction of the width of the slot, may be greater than the width of the slot. For example, the electrical insulating element which protrudes from the upper face 8 of the electronic card 6 may have a width of 1 mm to 10 mm greater than that of the slot 10.

[0054] Thus, as can be seen in [Fig.5] which is a section in a vertical plane along the slot 10 (therefore along the axis B visible in [Fig.4]) the length of the part of the electrical insulating element which protrudes from the upper face 8 of the electronic card 6 is greater than the length LO of the slot 10. Similarly, as can be seen in [Fig.6], the width of the part of the electrical insulating element which protrudes from the upper face 8 of the electronic card 6 is greater than the width LA of the slot 10. In other words, the electrical insulating element extends on the upper face of the electronic card beyond the edge of the slot 10.

[0055] [Fig.6], which is a detail view of [Fig.2], also shows the distance d between the lower face 7 of the electronic card 6 and the upper face 5 of the capacitor 1.

[0056] The invention thus developed makes it possible to avoid any risk of short-circuiting a capacitor linked to an electronic card, which would be linked to stagnation of water or humidity on the upper surface of the capacitor. This is obtained by a simple and reliable solution, namely the formation of an electrical insulating element (for example a bead of glue) through a slot formed in the electronic card over at least the entire width of the capacitor. In addition, the glue makes it possible to improve the mechanical strength of the capacitor with respect to the capacitor.

[0057] In some embodiments, the electrically insulating element also forms an insulating wall on the upper surface of the electronic board, which increases the creepage distance of the capacitor.

[0058] Nomenclature: • 1: Capacitor • 2: Capacitor housing • 3: Capacitor terminals • 4: Resin • 5: Upper face of the capacitor • 6: Electronic card • 7: Underside of the electronic card • 8: Upper face of the electronic card • 9: Electrical insulating element • 10: Slot

Claims

Claims

1. Device comprising an electronic card (6) and a capacitor (1), the capacitor (1) comprising two terminals (3) which are connected to the electronic card (6), so that the capacitor (1) has an upper face (5) substantially parallel to a lower face (7) of the electronic card (6), and in which a length (L) of the capacitor (1) is defined as being a dimension of the capacitor (1) in the direction of an axis connecting the two terminals (3) of the capacitor (1), measured parallel to the upper face (5) of the capacitor (1), and in which a width (1) of the capacitor (1) is defined as being a dimension of the capacitor (1) perpendicular to its length (L) and measured parallel to the upper face (5) of the capacitor (1), the device being characterized in that the electronic card (6) comprises a slot (10) forming a through opening in said electronic card (6),the slot (10) being interposed between the two terminals (3) of the capacitor (1) and oriented to be intersecting with the axis connecting the two terminals (3) of the capacitor (1), the slot (10) extending opposite the entire width of the capacitor (1), and in that the device further comprises an electrically insulating element (9) in said slot (10) and on the upper face (5) of the capacitor (1), the electrically insulating element (9) being interposed between the terminals (3) of the capacitor (1) over the entire width of the capacitor (1).,

2. Device according to claim 1, in which the electrically insulating element (9) is a bead of glue.

3. A device according to claim 2, wherein the glue is a silicone-based glue.

4. A device according to claim 2, wherein the glue is selected from a polyurethane glue, a polysulfide-based glue, an epoxy glue, and an acrylic glue.

5. Device according to any one of the preceding claims, in which the slot (10) is perpendicular to the axis connecting the two terminals (3) of the capacitor (1).

6. A device according to any preceding claim, wherein the slot (10) is equidistant from each of the terminals (3).

7. Device according to any one of the preceding claims, in which a part of the electrical insulating element protrudes from an upper face (8) of the electronic card (6), opposite its lower face (7).

8. Device according to claim 7, in which the electrically insulating element (9) extends on the upper face (8) of the electronic card (6) beyond an edge of the slot.

9. Device according to any one of the preceding claims, in which the upper face (5) of the capacitor (1) is at a distance from the lower face (7) of the electronic card (6).

10. Device according to claim 7 or claim 8, in which the part of the electrical insulating element which protrudes from the upper face (8) of the electronic card (6) has a height (H), measured perpendicular to said upper face of the electronic card, of between 0.5 mm and 8 mm, for example between 1 mm and 1.5 mm.

11. Device according to any one of the preceding claims, in which the slot (10) has a length (LO), measured in the plane of the upper surface (8) of the electronic card (6) in the direction of the largest dimension of the slot, of between 5 mm and 50 mm.

12. Device according to any one of the preceding claims, in which the slot (10) has a width (LA), measured in the plane of the upper surface (8) of the electronic card (6) in the direction of the smallest dimension of the slot, of between 0.5 mm and 6 mm.

13. 111111. Electromagnetic compatibility filter comprising a device according to any one of the preceding claims.

14. An electromagnetic compatibility filter according to claim 13, wherein the capacitor (1) is an X-type capacitor.

15. An inverter comprising a device according to any one of claims 1 to 12.

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