Encapsulation process and assembly encapsulated by such a process

Abstract

Encapsulation method and assembly encapsulated by such a method The invention relates to a method for encapsulating a printed circuit board (2) comprising at least: at least one electronic component (3) and at least one connector (4) having at least a first part (5) electrically connected to the printed circuit board (2) and comprising at least: a first overmolding step, during which at least a part of the printed circuit board (2) and the electronic component (3) are covered by a first covering layer (8); a first cooling step, during which the first covering layer (8) is cooled; a second overmolding step, during which the first covering layer (8) and the first part (5) of the connector (4) are covered by a second covering layer (9); and a second cooling step, during which the second covering layer (9) is cooled.Figure to be published with the abbreviation: Figure 6.

Description

Title of the invention: Encapsulation method and assembly encapsulated by such a method TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of the encapsulation of electronic components.

[0002] The present invention relates to a novel encapsulation method for an electronic card and the resulting encapsulated electronic card. Such an electronic card is particularly intended for use in atmospheres at risk of explosion, also known by the acronym ATEX, in particular in the aeronautical field, and more particularly in the field of aircraft fuel tanks. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] In certain environments, for example in ATEX atmospheres, liquid or gaseous, such as in aircraft fuel tanks, particularly in the aeronautics field, the electronic components must be protected and isolated from the outside, both to protect them from risks coming from the external environment, but also to avoid any electrical risk to the outside from the electronic components.

[0004] Among the known protection techniques, one solution consists of sealing the electronic components in a hermetic enclosure. Such a solution is however expensive, bulky and heavy. In addition, it is not reliable and safe in all circumstances.

[0005] Another known protection technique consists of encapsulating the electronic components, that is to say, embedding them in a protective coating.

[0006] Among the encapsulation solutions, the resination technique is known, also called by the English term "potting", consisting of a process during which an electronic card is housed in a housing in which a low viscosity resin is poured in order to completely cover the electronic card.

[0007] However, depending on the nature of the resin, air bubbles may become trapped in the resin, which may create hot spots and other defects, and / or the resin may deteriorate the solder joints of the electronic board.

[0008] Furthermore, the use of a housing limits the freedom of form for encapsulation and increases both the cost, the size and the weight of this solution.

[0009] There is therefore a need for a method of encapsulating electronic components which is inexpensive, compact and which limits the addition of weight, while remaining reliable and safe in all circumstances, in particular to guarantee the electrical insulation of electronic components from the outside and to guarantee their protection against humidity, chemical attacks, corrosive influences, etc. from the environment.

[0010] An encapsulation process must also: protect electronic components from shocks and vibrations, guarantee electrical insulation in the event of failure or external events, such as lightning strikes, provide protection against thermal shock, and ensure their sealing, even in the event of failure, combustion and / or explosion of one of the electronic components.

[0011] In addition, an encapsulation method must also protect the immediate environment of the electronic components from hazards, particularly electrical hazards, that they may represent. For example, the encapsulation must prevent any propagation outside the encapsulation of a possible electric arc and / or spark coming from the electronic components.

[0012] An encapsulation process must also allow: to withstand high temperature variations, in particular from -55°C to +85°C, allow differential thermal expansion of the electronic card to avoid the risk of tearing off the components, ensure the hermeticity of the electronic card, and allow heat dissipation of the components, while guaranteeing intrinsic safety.

[0013] Finally, the encapsulation process and the resulting encapsulated electronic card must be chemically compatible with fuels and hydraulic fluids and present no risk of biocontamination of such products. Summary of the invention

[0014] To this end, the invention relates to an encapsulation method based on double overmolding, in two stages, with adhesion between two covering layers over their entire contact surface.

[0015] The invention therefore relates to a method of encapsulating an assembly comprising at least one printed circuit comprising: at least electronic component and at least one connector having a first part electrically connected to the printed circuit.

[0016] In addition, the connector may have a second part connected to a cable electric.

[0017] More specifically, the encapsulation method according to the invention comprises at least • a first overmolding step, during which at least part of the printed circuit and the electronic component are covered by a first covering layer, in particular a hot-melt adhesive compound; • a first cooling step, during which the first covering layer is cooled, in particular by being solidified; • a second overmolding step, during which the first covering layer and the first part of the connector are covered by a second covering layer, in particular a thermoplastic compound or thermoplastic elastomer; • a second cooling step, during which the second covering layer is cooled, in particular by being solidified, in order in particular to ensure direct adhesion between the first covering layer and the second covering layer, in particular by chemical adhesion and / or mechanical anchoring.

[0018] In addition, the first cooling step may include an extraction of the assembly thus obtained from a first injection mold.

[0019] Similarly, the first cooling step may include an extraction of the assembly thus obtained from the second injection mold.

[0020] The encapsulation method according to the present invention makes it possible to address the problems mentioned above. The first covering layer guarantees preservation of the printed circuit and ensures a hermetic environment around the electronic component. In addition, the second covering layer advantageously guarantees resistance to environmental stresses, in particular from hydrocarbons, sustainable aviation fuels, hydraulic fluids, etc.

[0021] The encapsulation method according to the present invention therefore provides double overmolding which, in addition to doubling the protection of the electronic component, notably allows the second covering layer to guarantee sealing of an assembly thus obtained from the encapsulation method according to the present invention with respect to an external environment, even in the event of failure of the first covering layer.

[0022] For this purpose, the first covering layer may be more flexible and deformable than the second covering layer, which has higher rigidity and increased strength.

[0023] Therefore, for example in a case where the electronic card is struck by lightning and an electric arc forms at the level of the electronic component despite the fact that it is embedded in the first covering layer, the second covering layer would constitute a second impassable barrier which would prevent the electric arc from escaping outside the encapsulation.

[0024] Furthermore, the first covering layer and the second covering layer adhere strongly, preferably chemically, ensuring that their interface is watertight.

[0025] In addition to the characteristics which have just been mentioned, the encapsulation method according to the invention may have one or more of the following additional characteristics, considered individually or according to all technically possible combinations: • the first overmolding step consists of injecting the first covering layer into a first injection mold at a first maximum pressure of 70 bars, in particular 50 bars, more specifically 15 bars, so as to preserve the integrity of the electronic component during the injection of the first covering layer; • the first overmolding step consists of injecting the first covering layer into the first injection mold at a first temperature, in particular higher than the melting temperature of the first covering layer, in particular the first temperature being lower than 250°C, in particular lower than 200°C, more preferably lower than 180°C, so as to preserve the integrity of the electronic component during the injection of the first covering layer; • the second overmolding step consists of injecting the second covering layer into the second injection mold at a second pressure, with a maximum value of 2000 bars, in particular between 500 bars and 1500 bars, more specifically between 800 bars and 1200 bars; • the second overmolding step consists of injecting the second covering layer into the second injection mold at a second temperature, in particular higher than a melting temperature and / or a glass transition temperature of the second covering layer; • the first covering layer has a first thickness, in particular between 0.5 mm and 5 mm, in particular between 2 mm and 4 mm, the first thickness being in particular dependent on the peak insulation voltages to be respected and must be sufficient to guarantee electrical insulation between the electronics and the external conductive environment; and / or • the second covering layer has a second thickness, in particular between 0.5 mm and 5 mm, in particular between 2 mm and 4 mm, the second thickness being in particular dependent on the peak insulation voltages to be respected and must be sufficient to guarantee electrical insulation between the electronic card and a conductive external environment.

[0026] Furthermore, the encapsulation method according to the invention may also have at least: • an initial preparatory step, during which at least one positioning means is positioned near the electronic card, and / or at least one first holding means is placed in support on the electronic card; • the initial preparatory stage takes place before the first overmolding stage; • an intermediate preparatory step, during which at least one second holding means is placed in contact with the electronic card, in particular on the positioning means; • the intermediate preparatory step occurs after the first cooling step and / or before the second overmolding step; and / or • the second cooling step ensures direct adhesion between the first covering layer and the second covering layer, in particular by chemical adhesion and / or by mechanical anchoring.

[0027] In addition: • the first covering layer is a hot-melt adhesive compound, notably comprising mainly polyamide; • the second covering layer (9) is a thermoplastic compound or thermoplastic elastomer, in particular comprising mainly ether-amide block copolymer, polyethersulfone, polyetheretherketone and / or polyamide; and / or • the second covering layer may contain a filler of electrically conductive material, in particular carbon black, in particular in an amount sufficient to make the second covering layer conductive after curing.

[0028] Another aspect of the invention relates to an assembly comprising a printed circuit comprising at least one electronic component, at least one connector having at least a first part electrically connected to the printed circuit and a second part connected to an electrical cable.

[0029] More specifically, the assembly is obtained by the encapsulation process described above, and in which: • at least part of the printed circuit board and the electronic component are re- covered by a first covering layer, and • the first covering layer and the first part of the connector are covered by a second covering layer.

[0030] In addition, the first covering layer and the second covering layers are mutually bonded by direct adhesion, in particular by chemical adhesion and / or mechanical anchoring.

[0031] According to one aspect of the invention, the first covering layer is a compound mainly comprising polyamide and / or the second covering layer is a compound mainly comprising ether-amide block copolymer, polyethersulfone, polyetheretherketone and / or polyamide.

[0032] Thanks to the invention, the electronic component is isolated from the external environment, and vice versa, in a reliable, reproducible and durable manner.

[0033] The encapsulation method according to the invention is easy and quick to implement, can be automated and use known double overmolding equipment. In addition, the encapsulation method according to the invention makes it possible to reduce direct costs and non-recurring costs.

[0034] Finally, the encapsulation method according to the invention is compatible with the majority of electronic cards.

[0035] The encapsulated assembly obtained by the encapsulation method according to the invention has a reduced mass, size and number of parts compared to previous solutions and has excellent resistance to vibrations, temperature and attacks from the external environment.

[0036] Furthermore, the encapsulated assembly obtained by the encapsulation method according to the invention can be compatible with all environments by choosing a suitable composition for the second covering layer. BRIEF DESCRIPTION OF THE FIGURES

[0037] The present invention will be better understood and other characteristics and advantages will become apparent upon reading the detailed description which follows, comprising embodiments given by way of illustration with reference to the appended figures, presented as non-limiting examples, which may serve to complete the understanding of the present invention and the description of its embodiment and, where appropriate, contribute to its definition, in which: • [Fig.l] shows a schematic representation of a first example of an electronic card equipped with a connector connected to an electrical cable; • [Fig.2] shows a schematic representation of the electronic card of the [Fig.l] encapsulated in a first covering layer according to an example of the invention; • [Fig.3] shows a schematic representation of the electronic card of the [Fig.2] encapsulated in a second covering layer according to the invention; • [Fig.4] shows a schematic representation of a second example of electronic card equipped with a connector connected to an electric cable; • [Fig.5] shows a schematic representation of the electronic card of the [Fig.4] encapsulated in a first covering layer according to the invention; • [Fig.6] shows a schematic representation of the electronic card of the [Fig.5] encapsulated in a second covering layer according to the invention; and • [Fig.7], [Fig.8], [Fig.9], [Fig.10], [Fig.11] and [Fig.12] illustrate diagram technically an example of a double overmolding encapsulation process according to the invention. DETAILED DESCRIPTION

[0038] It should be noted that, in the figures, the structural and / or functional elements common to the different embodiments may have the same references. Thus, unless otherwise stated, such elements have identical structural, dimensional and material properties.

[0039] [Fig.l] to [Fig.6] illustrate schematic representations of two examples of an electronic card 1 according to the invention.

[0040] More specifically, as shown in [Fig.l] and [Fig.4], the electronic card 1 further comprises a printed circuit 2 comprising at least one electronic component 3 mounted on the surface of the printed circuit 2.

[0041] The electronic card 1 also comprises at least one connector 4, having a first part 5, electrically connected to the printed circuit 2, and a second part 6, connected to an electrical cable 7.

[0042] The electric cable 7 may be rigid or flexible, and possibly covered with a sheath, for example made of polytetrafluoroethylene (PTFE).

[0043] The connector 4 has, for example, the function of supplying the electronic card 1 with electrical energy and / or of allowing an exchange of electrical signals between the electronic card 1 and another device, for example connected to the electrical cable 7.

[0044] According to a particular embodiment, the connector 4 and the electrical cable 7 can be a single piece.

[0045] The invention relates to a method of encapsulating the electronic card 1, as well as the resulting encapsulated assembly.

[0046] The encapsulation method according to the invention comprises at least one first step overmolding, during which at least a portion of the printed circuit 2 and the electronic component 3 are covered by a first covering layer 8, in particular a hot-melt adhesive compound. Thus, at least a portion of the printed circuit 2 and the electronic component 3 are encapsulated in the first covering layer 8

[0047] The first covering layer 8 constitutes a first overmolding.

[0048] The first overmolding step of the encapsulation method according to the invention is carried out in a first injection mold, for example using a conventional overmolding technique.

[0049] In particular, the first overmolding step of the encapsulation method according to the invention may consist of an injection of the first covering layer 8 into the first injection mold at a first pressure PL. The first pressure PI may in particular have a maximum value of 70 bars, in particular 50 bars, more specifically 15 bars.

[0050] In addition, the first overmolding step of the encapsulation method according to the invention may consist of injecting the first covering layer 8 into the first injection mold at a first temperature TL. The first temperature T1 is in particular higher than a melting temperature of the first covering layer 8. However, the first temperature T1 is lower than 250°C, in particular lower than 200°C, more specifically lower than 180°C.

[0051] The first covering layer 8, in particular the hot-melt adhesive compound, has a first thickness E1, in particular between 0.5 mm and 5 mm, in particular between 2 mm and 4 mm.

[0052] In addition, the encapsulation method according to the invention comprises at least one first cooling step, during which the first covering layer 8 is cooled. As a result, the first covering layer 8 solidifies.

[0053] [Fig.2] and [Fig.5] illustrate schematic representations of the electronic card 1, respectively of [Fig.1] and of [Fig.3], encapsulated in the first covering layer 8, at the end of the first cooling step of the encapsulation method according to the invention.

[0054] According to a first exemplary embodiment, as presented in [Fig.2], the first part 5 of the connector 4 can remain outside the first covering layer 8. According to a second exemplary embodiment, as presented in [Fig.5], the first part 5 of the connector 4 can be covered by the first covering layer 8 in order to also be encapsulated.

[0055] It is then possible to remove the electronic card 1, partially or entirely encapsulated by the first covering layer 8, from the first injection mold.

[0056] Furthermore, the encapsulation method according to the invention comprises at least one second overmolding step, during which the first covering layer 8 and the first part 5 of the connector 4 are covered by a second covering layer 9, in particular a thermoplastic compound or thermoplastic elastomer. Thus, the first covering layer 8 and the first part 5 of the connector 4 are encapsulated by the second covering layer 9.

[0057] During the second overmolding step, the first part 5 of the connector 4, even if it was located outside the first covering layer 8 as may be the case according to the first exemplary embodiment, is now also encapsulated in the second covering layer 9.

[0058] The second covering layer 9 constitutes a second overmolding.

[0059] The second overmolding step of the encapsulation method according to the invention is carried out in a second injection mold, in particular arranged around the assembly resulting from the first cooling step, for example according to a conventional overmolding technique.

[0060] In particular, the second overmolding step of the encapsulation method according to the invention may consist of an injection of the second covering layer 9 into the second injection mold at a second pressure P2. The second pressure P2 may in particular have a maximum value of 2000 bars, in particular between 500 bars and 1500 bars, and more specifically between 800 bars and 1200 bars.

[0061] In addition, the second overmolding step of the encapsulation method according to the invention may consist of injecting the first covering layer 8 into the first injection mold at a second temperature T2. The second temperature T2 is in particular higher than a melting temperature and / or a glass transition temperature of the second covering layer 9.

[0062] In particular, if the second covering layer 9 is a thermoplastic or a thermoplastic elastomer, the second temperature T2 is in particular greater than • the melting temperature of the second covering layer 9 if it is semi-crystalline, and / or • the glass transition temperature of the second covering layer 9 if it is amorphous.

[0063] The second covering layer 9, in particular the thermoplastic compound or thermoplastic elastomer, has a second thickness E2 in particular between 0.5 mm and 5 mm, in particular between 2 mm and 4 mm.

[0064] The first thickness E1 and the second thickness E2 may for example have a value of 3 mm. A value given for these thicknesses will be designated hereinafter by a generic value of XX mm.

[0065] By such a dimension, it is understood that not only is the electronic component 3 covered by the first covering layer 8, itself covered by the second covering layer 9. By “covered” we of course mean “entirely covered”.

[0066] Similarly, a surface of the electronic component 3 is covered by the first covering layer 8 of at least XX millimeters thickness and by the second covering layer 9 of at least XX millimeters thickness.

[0067] The first covering layer 8 and the second covering layer 9 of at least XX mm thickness can, for example, match the reliefs of the electronic card 1, with a substantially constant thickness on the electronic card 1.

[0068] Alternatively or additionally, the first covering layer 8 and the second covering layer 9 of at least XX mm thickness may, for example, be in the form of a block, as shown in the figures, with a variable thickness but never less than XX mm thickness.

[0069] It is also conceivable that the first covering layer 8 substantially matches the reliefs of the electronic card 1 while the second covering layer 9 is in the form of a block whose external shape will define that of the finished product.

[0070] The second covering layer 9 may also be molded with fixing elements allowing mounting of the encapsulated electronic card 1 where it will be used.

[0071] Such fixing elements may for example be molded in one piece with the second covering layer 9 or be partially integrated into it during the second overmolding step.

[0072] During the second overmolding step, the electronic components 3 are protected from the molding pressure by the first covering layer 8.

[0073] The encapsulation method according to the invention also comprises at least one second cooling step, during which the second covering layer 9 is cooled. As a result, the second covering layer 9 solidifies.

[0074] During the second cooling step, the second covering layer 9 ensures direct adhesion to the first covering layer 8, in particular by chemical adhesion and / or by mechanical anchoring, so as to achieve perfect adhesion and / or perfect sealing between the first covering layer 8 and the second covering layer 9.

[0075] [Fig.3] and [Fig.6] illustrate schematic representations of the electronic card 1, respectively of [Fig.2] and of [Fig.5], encapsulated in a second covering layer 9 according to the invention, at the end of the second cooling step. development of the encapsulation process according to the invention.

[0076] It is then possible to remove the electronic card 1 encapsulated, in whole or in part, in the first covering layer 8 and in the second covering layer 9, from the second injection mold.

[0077] In the present description, • the term “direct adhesion” must be understood as being a mechanism of adhesion of the contact surfaces of two materials, in this case the first covering layer 8 and the second covering layer 9, without adding a third intermediate material between them; • the term “chemical adhesion” must be understood as being a mechanism of adhesion of the contact surfaces of two materials, in this case the first covering layer 8 and the second covering layer 9, by molecular contact and by the establishment of chemical bonds between atoms, molecules and / or functional groups, for example by the creation of covalent bonds between the contact surfaces; • the term “mechanical anchoring” must be understood as being a mechanism for adhesion of the contact surfaces of two materials, in this case the first covering layer 8 and the second covering layer 9, in which one of the two materials is brought into contact in liquid form on the surface of the other material and penetrates into the pores of the other material before drying and / or hardening to ensure mechanical adhesion between the two materials; • the term “mechanical anchoring” must also be understood as being a mechanism for adhesion of the contact surfaces of two materials, in this case the first covering layer 8 and the second covering layer 9, in which one of the two materials comprises cavities intended to be filled by the other material in order to ensure solidarity between two materials and to prevent separation of the two materials after cooling and solidification; • the term “hot-melt adhesive compound” should be understood as encompassing all types of hot-melt glues, also known by the acronym “HMA” for “Hot-Melt Adhesive” in English, and being a category of thermoplastic adhesive; • the term “thermoplastic compound” must also be understood as encompassing all types of polymers or polymer mixtures capable of softening or melting following a rise in temperature in a reversible manner; and • the term “thermoplastic elastomer compound” should be understood as being all types of copolymers or polymer blends combining a thermoplastic character, that is to say which softens or melts following a rise in temperature and which hardens upon cooling, and the elastic properties of elastomers.

[0078] The hot melt adhesive compound and the thermoplastic or thermoplastic elastomer compound may be chosen so as to meet one or more of the following conditions: • in the liquid state, the hot melt adhesive compound must have a low viscosity, so that it can, • on the one hand, infiltrate around the electronic components during the first overmolding stage, in particular without generating bubbles and, • on the other hand, be injected at low pressure to preserve the integrity of the electronic component covered by overmolding; • the hot melt adhesive compound must be an electrical insulator; • the hot melt adhesive compound must not exhibit capacitive coupling; • the hot melt adhesive compound must be flame retardant; • the hot melt adhesive compound must not be a thermal insulator, in order to allow heat dissipation of the electronic component; • the hot-melt adhesive compound must be elastically deformable, in particular to allow expansion of the electronic component; • the hot melt adhesive compound must not be corrosive, in particular so as not to chemically damage the electronic component; • the thermoplastic compound or thermoplastic elastomer must be suitable for the environment in which the electronic card will be used, so as not to contaminate and / or damage the environment in which it is located, and vice versa; • the hot-melt adhesive compound and the thermoplastic or thermoplastic elastomer compound must be mutually compatible, so as not to contaminate and / or deteriorate each other, in particular in order to achieve the best possible adhesion at their interface, more specifically by chemical adhesion and / or by mechanical anchoring, so as to make any penetration of fluid between the first covering layer 8 and the second covering layer 9 impossible; • the hot melt adhesive compound and the thermoplastic compound or thermoplastic elastomer must comply with the European REACH regulation, acronym for “Registration, Evaluation, Authorisation of Chemicals” in English.

[0079] According to one embodiment of the invention, the hot melt adhesive compound can be a compound comprising mainly polyamide (PA). Furthermore, the thermoplastic compound or thermoplastic elastomer may be a compound comprising mainly ether-amide block copolymer (TPE-A). Thus, the polyamide groups of the hot-melt adhesive compound and the thermoplastic compound or thermoplastic elastomer create a chemical adhesion between the first covering layer 8 and the second covering layer 9.

[0080] As a reminder, an ether-amide block copolymer TPE-A has the general formula HO-(CO-PA-CO-O-PE-O)nH where: • PA is a polyamide, and • PE is a polyether.

[0081] The elastomer thermoplastic constituting the second covering layer 9 may be capable of absorbing shocks and vibrations. In addition, the elastomer thermoplastic constituting the second covering layer 9 may be capable of deforming without damaging the electric cable 7 in the event of mechanical stress on the latter.

[0082] According to another embodiment of the invention, the thermoplastic compound or thermoplastic elastomer may be a thermoplastic compound comprising mainly polyamide (PA). In such another embodiment of the invention, the polyamide (PA) constituting the second covering layer 9 is more economical and more rigid. In addition, it is capable of integrating additional functions, such as areas intended for fixing a housing to a support.

[0083] According to yet another embodiment of the invention, the second covering layer 9 is made with a thermoplastic compound mainly comprising polyethersulfone (PES) and / or polyetheretherketone (PEEK). The second covering layer 9 thus has excellent mechanical strength and excellent chemical stability.

[0084] According to yet another embodiment, the thermoplastic compound or thermoplastic elastomer does not contain any filler capable of making it electrically conductive, so as to reinforce electrical insulation of the printed circuit 2, with an environment in which it is used.

[0085] According to yet another embodiment of the invention, the thermoplastic compound or thermoplastic elastomer may contain an electrically conductive filler, such as, for example, carbon black, in an amount sufficient to make the thermoplastic compound or thermoplastic elastomer conductive after curing. Thus, the thermoplastic compound or thermoplastic elastomer advantageously makes it possible to dissipate electrostatic charges.

[0086] The first overmolding step and the second overmolding step implemented by the invention use known molds and technologies. During the first overmolding step and the second overmolding step, a position of the assembly to be overmolded must be referenced. In addition, the assembly to be overmolded must be kept centered inside the first injection mold and / or in the second injection mold.

[0087] For this purpose, positioning and / or holding of the assembly to be overmolded can be done by means of • positioning means, allowing very precise referencing of the position of the elements to be encapsulated, and • holding means, making it possible to immobilize the elements to be encapsulated during the encapsulation process according to the invention.

[0088] The positioning means are preferably metallic, in particular in order to withstand the temperatures considered during the encapsulation process. Furthermore, the metallic positioning means are capable of acting as electrical connectors.

[0089] In addition, the positioning means may be removable.

[0090] According to a particular embodiment, the connector 4, if it is sufficiently rigid, can also act as positioning means and / or holding means.

[0091] An example of an embodiment of the encapsulation method according to the invention is described with reference to [Fig.7] to [Fig. 12].

[0092] For reasons of simplification, the electronic component 3 is not illustrated and the shapes of the different elements to be encapsulated are simplified in a very schematic manner.

[0093] The encapsulation method according to the invention may comprise an initial preparatory step, in particular shown in [Fig.7], during which at least one positioning means 10, in particular at least one insert 10, is positioned close to the electronic card 1. According to a particular embodiment, the positioning means 10 is positioned at a distance from the electronic card 1.

[0094] The positioning means 10 may have a height substantially equal to a height that the electronic card 1 will have at the end of the encapsulation process, after encapsulation by the first covering layer 8 and the second covering layer 9, in double overmolding.

[0095] The initial preparatory step may also include the installation of at least one first holding means 11a, in particular at least one centering device 11a. In addition, the first holding means 11 may also be placed in support on the electronic card 1, in particular on different faces of the electronic card 1, in order to immobilize it in the first injection mold.

[0096] Alternatively, the first holding means 11a can be directly positioned in the first injection mold.

[0097] Such a first holding means 11a may in particular be supported in a dead zone of the electronic card 1, that is to say in an area devoid of the electronic component 3.

[0098] The encapsulation method according to the invention may comprise a first positioning step, during which the assembly thus formed at the end of the initial preparatory step is introduced into the first injection mold, in which the positioning means 10 and the first holding means 11a are immobilized.

[0099] Subsequently, the first covering layer 8, in particular the hot-melt adhesive compound, is then injected, in particular in liquid form, according to the first overmolding step of the encapsulation method according to the invention, into the first injection mold.

[0100] The first injection mold is sized so as to allow the first covering layer 8 to cover by overmolding at least part of the printed circuit 2 and the electronic component 3.

[0101] All or part of the connector 4 may also be covered by overmolding with the first covering layer 8, although this is not necessarily necessary during the first overmolding step.

[0102] In the example of [Fig.8], the entire printed circuit 2 is covered by overmolding, although it is only necessary for the electronic component 3 to be covered and encapsulated in the first covering layer 8.

[0103] After the first cooling step, the first covering layer 8 has cooled and solidified, the first holding means 11a can be removed, revealing at least one hollow volume, forming a well 12, visible in particular in [Fig.9].

[0104] Prior to the second overmolding step, the encapsulation method according to the invention may comprise at least one intermediate preparatory step, during which at least one second holding means 11b, in particular at least one centering device 11b, is placed in place. In addition, the second holding means 11b may also be placed in contact with the electronic card 1, in particular on different faces of the electronic card 1, in order to immobilize it in the second injection mold.

[0105] Alternatively, the second holding means 11b can be directly positioned in the first injection mold.

[0106] According to a particular embodiment, the second holding means 11b is positioned on the positioning means 10, a part of which emerges outside the first layer 8, as can be seen in [Fig. 10].

[0107] The encapsulation method according to the invention may comprise a second positioning step, during which the assembly thus formed at the end of the intermediate preparatory step is introduced into the second injection mold, in which the second holding means 11b, in particular integral with the second injection mold, are immobilized.

[0108] Subsequently, the second covering layer 9, in particular the thermoplastic compound or thermoplastic elastomer, is then injected, in particular in liquid form, according to the second overmolding step of the encapsulation method according to the invention into the second injection mold.

[0109] The second injection mold is sized so as to allow the second covering layer 9 to cover the first covering layer 8 by overmolding, in particular in its entirety.

[0110] Furthermore, at least the first part 5 of the connector 4, whether it has already been previously covered by the first covering layer 8 or not, is covered by the second covering layer 9, so as to protect a junction of the connector 4 with the electronic card 1 and to guarantee the sealing of the assembly at the connector 4, as shown in [Fig. 1 1].

[0111] For this purpose, the second covering layer 9 may have sufficient flexibility to deform and accompany the electric cable 7 in the event of mechanical stress.

[0112] During the second overmolding step, the well 12 is filled and overmolded by the second covering layer 9.

[0113] The positioning means 10 is suitable for being used, subsequently, as a fixing point, in particular by screwing, on a support. In addition, the positioning means 10 is also suitable for acting as an anti-creep ring.

[0114] In certain cases, the electrical cable 7, to which the connector 4 is connected, may be covered with a sheath, in particular made of polytetrafluoroethylene PTFE, on which the first covering layer 8 and / or the second covering layer 9 is / are likely to adhere poorly.

[0115] In order to guarantee the sealing of the electronic card 1 at the interface with the sheath, the encapsulation method according to the invention may provide a sealing step, during which a sealing sleeve may be added, in particular heat-sealed, to the interface between the sheath and the first covering layer 8 and / or the second covering layer 9.

[0116] Alternatively or in addition, the sealing step is such that the sheath undergoes a surface treatment aimed at improving the adhesion of the first covering layer 8 and / or the second covering layer 9.

[0117] According to a particular embodiment, the encapsulation method according to the invention provides for the implementation of: • a plurality of positioning means 10, in particular a plurality of inserts 10, • a plurality of first holding means 11a, in particular a plurality of centering devices 11a, and / or • a plurality of second holding means 11b, in particular a plurality of centering means 11b.

[0118] The encapsulation method according to the invention is such that the number of second holding means 11b is less than or equal to the number of positioning means 10.

[0119] The assembly comprising a printed circuit 2 and at least one connector 4, and encapsulated according to the encapsulation method of the invention is such that at least a part of the printed circuit 2 and the electronic component 3 are overmolded in the first covering layer 8, while the entirety of the first covering layer 8 and the first part 5 of the connector 4 are overmolded in the second covering layer 9.

[0120] The encapsulation method of the invention makes it possible to have strong adhesion and perfect sealing between the first covering layer 8 and the second covering layer 9, for example by chemical adhesion or mechanical anchoring.

[0121] According to various embodiments, the printed circuit 2 may comprise a plurality of electronic components 3 mounted on the surface of the printed circuit 2. According to the invention, in such configurations, all the electronic components 3 are covered by the first covering layer 8 during the first overmolding step.

[0122] The assembly obtained by the encapsulation method according to the invention is in particular an assembly intended to be used in a fuel tank of an aircraft and / or in an ATEX atmosphere.

[0123] Although described through a certain number of examples, variants and embodiments, the encapsulation method according to the invention and the assembly which results therefrom comprise various variants, modifications and improvements which will appear obvious to those skilled in the art, it being understood that these variants, modifications and improvements are part of the scope of the invention.

Claims

Claims

1. Method for encapsulating an assembly comprising at least one printed circuit (2) comprising: - at least one electronic component (3) and - at least one connector (4) having at least a first part (5) electrically connected to the printed circuit (2) - characterized in that it comprises at least: - a first overmolding step, during which at least a part of the printed circuit (2) and the electronic component (3) are covered by a first covering layer (8); - a first cooling step, during which the first covering layer (8) is cooled; - a second overmolding step, during which the first covering layer (8) and the first part (5) of the connector (4) are covered by a second covering layer (9); and - a second cooling step, during which the second covering layer (9) is cooled.

2. Encapsulation method according to claim 1, characterized in that the first overmolding step consists of an injection of the first covering layer (8) into a first injection mold at a first pressure (PI), in particular between 0 bar and 70 bar, in particular between 0 bar and 50 bar, more specifically between 0 bar and 15 bar, and / or at a first temperature (Tl), in particular higher than a melting temperature of the first covering layer (8).

3. Encapsulation method according to any one of the preceding claims, characterized in that the second overmolding step consists of an injection of the second covering layer (9) into the second injection mold at a second pressure (P2), of a maximum value of 2000 bars, in particular between 500 bars and 1500 bars, more specifically between 800 bars and 1200 bars, and / or at a second temperature (T2), in particular higher than a melting temperature and / or a glass transition temperature of the second covering layer (9).

4. Encapsulation method according to any one of the preceding claims, characterized in that the first covering layer (8) has a first thickness (E1), in particular between 0.5 mm and 5 mm, in particular between 2 mm and 4 mm, and / or in that the second covering layer (9) has a second thickness (E2), in particular between 0.5 mm and 5 mm, in particular between 2 mm and 4 mm.

5. Encapsulation method according to any one of the preceding claims, characterized in that it further comprises an initial preparatory step, during which at least one positioning means (10) is positioned close to the electronic card (1), and / or at least one first holding means (11a) is to be placed in contact with the electronic card (1).

6. Encapsulation method according to claim 5, characterized in that the initial preparatory step occurs before the first overmolding step.

7. Encapsulation method according to claim 5 or 6, characterized in that it further comprises an intermediate preparatory step, during which at least one second holding means (11b) is placed in contact with the electronic card (1), in particular on the positioning means (10).

8. Encapsulation method according to claim 7, characterized in that the intermediate preparatory step occurs after the first cooling step and / or before the second overmolding step.

9. Encapsulation method according to any one of the preceding claims, characterized in that the second cooling step ensures direct adhesion between the first covering layer (8) and the second covering layer (9), in particular by chemical adhesion and / or by mechanical anchoring.

10. Encapsulation method according to the preceding claim, characterized in that the first covering layer (8) is a hot-melt adhesive compound, in particular comprising mainly polyamide (PA), and / or in that the second covering layer (9) is a thermoplastic or thermoplastic elastomer compound, in particular comprising mainly ether-amide block copolymer (TPE-A), polyethersulfone (PES), polyetheretherketone (PEEK) and / or polyamide (PA).

11. Encapsulation method according to any one of the preceding claims, characterized in that the second covering layer (9) contains a filler of electrically conductive material, in particular carbon black.

12. Assembly comprising a printed circuit (2) comprising: - at least one electronic component (3), and - at least one connector (4) having at least a first part (5) electrically connected to the printed circuit (2), and - a second part (6) connected to an electrical cable (7), - characterized in that it is obtained by the encapsulation method according to any one of the preceding claims, and in that: - at least a part of the printed circuit (2) and the electronic component (3) are covered by a first covering layer (8); and - the first covering layer (8) and the first part (5) of the connector (4) are covered by a second covering layer (9).

13. Assembly according to claim 12, characterized in that the first covering layer (8) and the second covering layer (9) are mutually linked by direct adhesion, in particular by chemical adhesion and / or by mechanical anchoring.

14. Assembly according to claim 12 or 13, characterized in that the first covering layer (8) is a compound comprising mainly polyamide and / or in that the second covering layer (9) is a compound comprising mainly ether-amide block copolymer (TPE-A), polyethersulfone (PES), polyetheretherketone (PEEK) and / or polyamide (PA).

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