Enclosing an electrical assembly

Abstract

A method (200) for enclosing an electrical assembly (100), the method (200) comprising the following steps: heating (225) a thermoplastic cover material (150) that extends over the assembly (100) on all sides; pneumatically pressing (235) the cover material (150) against the assembly (100); and cooling (240) the cover material (150).

Description

The present invention relates to a housing for an electrical assembly, in particular on board a motor vehicle. More preferably, the invention relates to the production of a housing for an electrical assembly and the installation of the assembly into the housing.A plurality of electrical or electronic systems comprising a number of electrical assemblies may be provided on board a motor vehicle. A module can comprise, for example, an electronic control unit, a processing device, an energy store, a sensor or an actuator. In order to protect the assembly from moisture, dust, vibrations or aggressive media such as oil or gasoline, it can be inserted into a housing. The housing may keep harmful influences away from the assembly and may have a fastening point for being attached to a structure of the motor vehicle.Providing a housing for the assembly and inserting the assembly into the housing may be referred to as a housing. The manufacture of the housing and the insertion are usually carried out separately from one another.Many housings are manufactured by injection molding. For this purpose, cost-intensive tools must be provided for one or more housing shells. The assembly can be snapped or screwed into the housing shell, for example, and the housing can be closed in a separate operation. This procedure can be cost-effective for the housing, in particular in large numbers. However, adapting the housing shape if requirements of the assembly change is complicated.The assembly can also be cast into a housing. For this purpose, a concave housing shell, for example made of sheet metal or plastic, can be used, into which the assembly is introduced and subsequently cast with a synthetic resin. After the resin has been cured, the assembly is ready for use. However, removing the assembly from the housing is generally not possible without destroying the housing or the assembly. Depending on the shape of the package, a substantial amount of resin may be required, which may increase the manufacturing cost of the package. The assembly can thereby be unnecessarily large or heavy.DE 10 2010 062 788 A1 relates to a method for producing electronic assemblies, comprising a carrier with conductor tracks applied thereon and at least one electronic component which is electrically conductively connected to at least one conductor track, in which the at least one electronic component is connected to the carrier and contact of the electronic component with at least one conductor track is produced, an adhesive layer is applied to the carrier with the at least one component and a film is laminated onto the carrier with the at least one component.DE 25 35 173 A1 shows a method for producing a moisture-proof covering of electrical components or component combinations with connecting wires which point in the same direction, which consists of a one-piece, deep-drawn, thermoplastic plastic film and a termination of a curable potting resin in the region of the connecting wires, and in which the potting space is preformed by the plastic film.DE 10 2014 100 281 A1 likewise discloses a method for injection molding a circuit board with electronic and / or electrical components arranged on the circuit board with plastic, wherein the components on the circuit board are covered at least partially with at least one film, and in the subsequent at least one part of the circuit board is injection molded with plastic with the electronic and / or electrical components.It is an object of the present invention to provide an improved technique for packaging an electrical assembly. The invention achieves this object by means of the subject matter of the independent claims. Dependent claims represent preferred embodiments.According to a first aspect of the present invention, a method of packaging an electrical assembly comprises the steps of heating a thermoplastic covering material that extends on all sides over the assembly; pneumatically pressing the covering material against the assembly; and cooling the covering material.It has been recognized that methods of vacuum deep drawing, also called vacuum forming or thermoforming, can be advantageously used for enclosing an electrical assembly. In this case, a housing shell or a complete housing can be produced and the assembly can be inserted into it. Advantageously, the shaping of the housing shell and the installation of the assembly in the housing shell can take place in a single operation. The packaging of the assembly can thus be carried out more quickly, with a reduced number of tools and overall more cost-effectively. The proposed method can be used advantageously in particular in small and medium quantities.The housing shell produced according to the method can be individually adapted to the electrical assembly. Manufacturing tolerances of the assembly or individual size differences may be harmless. The method may tolerate certain changes to the shape of the assembly without requiring a new tool or step of processing. The housing may be cut open and removed as necessary, for example, to repair the assembly. The assembly can then be provided with a new enclosure in the manner described.The method can be used on electrical assemblies in a wide range of sizes. Thus, for example, a simple electrical assembly, which consists only of a sensor of a few millimeters edge length, can be housed just as easily as a large assembly with an edge length of approximately 10 or approximately 20 cm.In a preferred embodiment, the covering material is plate-shaped before heating. The cover material may be provided in films or sheets of different thicknesses. The thickness of the covering material can be, for example, in the range from about 0.3 mm to about 10 mm. The covering material can be processed as a sheet or from a roll.Upon pressing the cover material against the assembly, the cover material may be connected to a bottom plate disposed on an opposite side of the assembly. The base material may comprise a planar plate, a profiled housing shell or a flexible material. In this case, the housing can comprise a housing shell and a base plate. In one embodiment, the floor material and the cover material are compatible with each other and may in particular be made of the same material, preferably a thermoplastic.Process steps described herein with respect to the cover material may also be applied to the floor material. In this case, the covering material and the floor material can be processed independently of one another or simultaneously. In the following, the term material is used for both the covering material and the floor material.In one embodiment of the method, the cover material is welded to the floor material. The welding can be effected in particular as part of the pneumatic pressing. In this case, the heated covering material can be pressed against the preferably likewise heated floor material. In another embodiment, the cover material can be welded to the base material in a separate operation only after the pressing. For this purpose, ultrasonic or laser welding can be used, for example.The base material may be thermoplastic. Like the cover material, it can be heated before the pressing, pressed pneumatically onto the assembly together with the cover material and cooled after the pressing.In general, the pneumatic pressing can be effected by generating a pneumatic pressure difference between a side facing away from the assembly and a side facing it. For this purpose, an overpressure can be effected on the side facing away and / or a reduced pressure or vacuum can be effected on the side facing away. If both the cover material and the base material are to be pneumatically deformed, the negative pressure or the vacuum can be generated between the cover material and the base material.In another variant, the covering material forms a bag before heating and the assembly is inserted into the bag before pressing. The vacuum may be created, for example, by exhausting air from the open end of the bag. The open end can be closed and welded in the course of pneumatic pressing. This variant can be used advantageously, for example, to weld a feeding element, such as a cable, in the region of the open end of the pouch. The cable can in particular comprise an electrical connection or a signal line which is connected to the electrical assembly.In yet another variant, the covering material forms a tube before heating and the assembly can be introduced into the tube before pressing. The procedure can be similar to that in the variant of the bag-shaped covering material, with the difference that two open ends are present before the pneumatic pressing. In each case, feeds or connections of the electrical assembly can be led through the ends and welded to the material.In all embodiments, the material may carry an additional recess through which air may be sucked to effect the vacuum between the material and the assembly. The recess can remain open after the pressing or be closed as part of the pressing or in a subsequent working step. For closing, a cover can be provided or the recess can be closed with a sealing compound.A penetrating element can be attached to the material, wherein the element can be connected to the assembly before pressing. The element can comprise, for example, a cable, a feed line or a plug contact. The material can be connected to the element in a materially integral manner, for example by means of welding. In another embodiment, the element is formed or formed integrally on the material. In order to prevent unintentional detachment of the material from the passing element, the heating of the material can only take place up to a predetermined distance from the element.If the element comprises a cable, the cable may be soldered or otherwise attached to the assembly before the material is heated and pressed. An element can also be attached to the assembly, for example, by means of screws, rivets or adhesive bonding.In a further preferred embodiment, a mechanical fastening point is formed on the material. The fastening point can in particular comprise a recess through which a screw, a rivet or a bolt can be inserted later. A region surrounding the recess may be made reinforced. The thickness of the material may be increased in this range. Alternatively, a mechanical fastening element, for example made of metal, can be provided, which is connected to the material in a materially integral manner.Before the pressing, a thermal guide element can be attached to the assembly. The thermal conducting element can comprise, for example, a conducting pad or a conducting paste. A larger cavity between the assembly and the housing shell can be avoided by introducing a gap filler. After the pressing, the guide element lies between the assembly and the gap filler and the latter can support a heat transport to the outside. After the housing, a thermal element, for example a cooling body or a heat exchanger, can be attached in this region on the outer side of the housing shell.In a further embodiment, a protective gas is conducted between the assembly and the material before the pressing. The inert gas may comprise, for example, an inert gas or a low-reaction gas such as CO 2 which may contribute to slowing down corrosion or chemical aging of the assembly. The protective gas can also prevent the generation of sparks, so that the assembly can be used in an improved manner in an explosion-protected environment.The material can comprise a planar shielding element. The shielding element can be designed to be soft magnetic for shielding a magnetic field or electrically conductive for shielding an electric field. Preferably, an electrical contact point of the shielding element on the material is led out. The contact point can be electrically conductively connected to the assembly or can be provided on the outer side of the housed assembly in order to be electrically connected there. It is particularly preferred that the shielding element is electrically insulated from the assembly by means of the material. Optionally, an insulation layer can be applied to the shielding element for this purpose. In yet another embodiment, the assembly may be provided with an electrical insulation material, which may be, for example, a plate, bag or tube, before being encased in the material.The assembly may be sequentially provided with first and second heated thermoplastic cover materials. The shielding member may be interposed between the two covering materials. The cover materials can have different properties. For example, a first material that is closer to the assembly may be more elastic than a second material that is further outward. Still further layers of thermoplastic material may be provided around the assembly. Functional layers can be provided between the layers, which for example realize a visual protection or a mechanical reinforcement. In yet another refinement, the housed electrical assembly can be re-housed together with another element. The other element may comprise, for example, a cooling element or a cooling channel.According to another aspect of the present invention, thermoforming is used to conform a housing shell for an electrical assembly to the assembly. At the same time, the assembly can be installed in the housing shell.According to yet another aspect of the present invention, an electrical assembly, which can be configured in particular for use on a motor vehicle, is accommodated in a housing shell described herein. The forming of the housing shell and the installation of the assembly can advantageously be carried out by means of a method described herein in only one operation.According to yet another aspect of the present invention, a motor vehicle includes an electrical assembly described herein. The assembly can be configured in particular for controlling the motor vehicle or a predetermined function on board the motor vehicle.The invention will now be described in more detail with reference to the accompanying figures, in which: FIG. 1 shows an assembly before and after the housing; and FIG. 2 shows a flow diagram of a method for housing an assemblyis.FIG. 1 shows an assembly 100. In a first illustration 105, the assembly 100 is illustrated before the housing and in a second illustration 110 after the housing. It should be noted that the assembly 100 and enclosure shown in FIG. 1 are only exemplary and schematically illustrated to illustrate aspects of the present invention.The assembly 100 comprises in the present case a printed circuit board 115, on the top side of which at least one component 120 is attached. Optionally, at least one component 120 can also be provided on the underside. A component 120 may in particular comprise a passive component, for instance a resistor, a capacitor, a plug connector or an inductor, or an active component, for instance a transistor or an integrated circuit. In FIG. 1, a central component 120 is designed to be active and is configured to emit heat during operation. On its upper side, the component 120 can carry a thermal conducting element 125, which can comprise, for example, heat-conducting paste or a heat-conducting pad.Filling compound 130 is provided between a left-hand and the middle component 120, which filling compound is configured to be distributed under pressure between the printed circuit board 115 and the components 120. Optionally, the filling compound 130 can be configured to cure, crosslink or set later. In this case, the filling compound 130 can have a predetermined thermal conductivity. The filling compound 130 is preferably electrically insulating.A component 120 shown on the right is exemplarily designed as a plug contact. A corresponding plug contact 135 can be electrically and mechanically connected to it.It is proposed to produce at least one housing shell 140 for the assembly 100 by means of thermoforming in only one working step and to simultaneously attach the assembly 100 in the housing shell 140. A housing 145 can in particular comprise an upper and a lower housing shell 140, which can be formed in a common operating step.The assembly 100 may be placed between a cover material 150 and a bottom material 155, the materials 150, 155 being thermoplastic so that they may be permanently deformed within a predetermined temperature range. A deformation temperature of the materials 150, 155 is preferably above an allowable operating temperature of the assembly 100. The operating temperature may be about -40 to +150° C. for an application on board a motor vehicle. The materials 150, 155 can therefore be plastically deformed, for example, from a temperature of approximately 155° C.Optionally, a mounting point 160 is formed on one of the materials 150, 155. The fastening point 160 can be connected to the material 150, 155 in one piece or in a materially integral manner. The attachment point 160 is configured to introduce a predetermined force into the material 150, 155. To prevent deformation or tearing of the material 150, 155, the attachment point 160 may comprise a reinforced resilient material, a section reinforced by material 150, 155, or a resilient insert. A reinforcement can also extend between two fastening points 160, for example in the form of a spar or frame. In one embodiment, a cutout or an aperture through the material 150, 155 is provided in the region of the fastening point 160. The attachment point 160 may be in the area of the assembly 100 or outside.A plug contact 135 leads through the covering material 150 and is preferably connected to the covering material 150 in a materially bonded manner. For example, the plug contact 135 can be formed on the cover material 150 or welded thereto. The plug contact 135 shown is connected to a cable 165 which is configured for the electrical connection of the assembly 100. The plug contact 135 can be inserted into the corresponding plug contact 135, which is formed by the component 120 shown on the right, before the covering material 150 is formed into a housing shell 140.For forming, the cover material 150 and the base material 155 are each heated to their thermoplastic temperature. Thereafter, the cover material 150 and the bottom material 155 are pneumatically pressed against the assembly 100. For this purpose, a region between the materials 150, 155 can be evacuated. At the same time, a fastening point 160 can be guided to a predetermined position or fixed there. If the materials 150, 155 are sufficiently close to the assembly 100, they can be cooled below their thermoplastic temperature. The pressing and cooling can only take a few seconds, so that there is no risk of thermal damage to a component 120 of the assembly 100.It can be seen in the second illustration 110 how, after this process, the covering material 150 bears against the assembly 100 and thus forms an upper housing shell 140. Depending on a mechanical structure of the assembly 100 and a flexibility of the cover material 150, a cavity 168 may remain locally between the housing shell 140 and the assembly 100. This can be filled by previously introduced filling compound 130. During the pneumatic pressing, the filling compound 130 can be distributed between the covering material 150 and the assembly 100 in such a way that it fills a cavity 168.Preferably, a supernatant 170 can be separated off only after the material 150, 155 has cooled below the thermoplastic temperature. In the region of the thermal guide element 125, a thermal element, such as a heat exchanger or a cooling body, can be attached. For this purpose, the housing shell 140 can optionally be removed in this region, for which purpose it can be cut open, for example by means of a knife or by laser.FIG. 2 shows a flow diagram of a method 200 for housing an assembly 100. For simplicity, the method 200 relates only to the production of a housing shell 140 and the attachment of the assembly 100 in the housing shell 140. In a corresponding manner, however, a plurality of housing shells 140 can also be formed simultaneously or a housing shell 140 can be formed on a base plate. The assembly 100 is preferably situated at the end in a complete housing 145, which is further preferably closed on all sides. By means of the method 200, a hermetic closure of the assembly 100 can be effected, which closure comprises an absolutely tight termination, which prevents in particular an exchange of air or water.In a step 205, a thermoplastic covering material 150 is provided. For this purpose, it is possible in particular to use a technical thermoplastic, for example a partially crystalline thermoplastic such as PPA or an amorphous thermoplastic such as PC or PET.In a step 210, the assembly 100 is provided. In an optional step 215, a thermal guide element 125 or a filling compound 130 can be attached to the assembly 100 in a predetermined region.In a step 220, an element 135, 160 extending through the cover material 150 may be attached to the assembly 100. For example, a mounting point 160 may be located or held at a predetermined location on the assembly 100. A plug contact 135 can be inserted into a corresponding plug contact 135 on the assembly 100. A cable 165 extending through the covering material 150 may be electrically connected to the assembly 100. In a corresponding manner, for example, a mechanical or hydraulic element 135, 160 can be connected to the assembly 100.In a step 225, the cover material 150 may be heated until it reaches its thermoplastic temperature. For this purpose, in particular infrared radiation or hot air can be used. Optionally, in a step 230, a protective gas can be introduced into the region between the covering material 150 and the assembly 100.In a step 235, the cover material 150 is pneumatically pressed against the assembly 100. For this purpose, a vacuum is preferably generated between the assembly 100 and the cover material 150. Once the covering material 150 has sufficiently bent into the assembly 100, it can be cooled again. Cooling can be accelerated by air movement.In a step 245, the assembly 100 surrounding the housing 145 or the housing shell 140 can be processed further. If, for example, the covering material 150 has a dedicated opening through which air is suctioned off during the pressing operation, this opening can be closed. A protrusion 170 comprising material 150 that protrudes above the assembly 100 may be separated. The supernatant 170 may be used to produce further cover material 150. An aperture or a recess, for example at a fastening point 160 or in the region of a thermal connection of a component 120 of the assembly 100, can be produced. The housing shell 140 formed can also be deburred, labeled or colored.If desired, the method 200 may be repeated to house the assembly 100 in another layer of cover material 150. Different layers can fulfil different functions and can be effected by means of different materials or material thicknesses.Reference numerals denote reference numerals100 Assembly 105 First illustration 110 Second illustration 115 Printed circuit board 120 Component 125 Thermal guide element 130 Filling compound, gap filler 135 Plug contact 140 Housing shell 145 Housing 150 Covering material 155 Base material 160 Fastening point 165 Cable 168 Cavity 170 Protrusion 200 Method 205 Covering material provide 210 Assembly provide 215 Gap filler mount 220 Element to assembly mount 225 Covering material heat 230 Protective gas insert 235 Covering material press on 240 Covering material cool 245 Separation of protrusion

Claims

A method (200) for enclosing an electrical assembly (100), the method (200) comprising the steps of: heating (225) a thermoplastic covering material (150) protruding on all sides over the assembly (100); pneumatically pressing (235) the covering material (150) against the assembly (100); and cooling (240) the covering material (150).The method (200) of claim 1, wherein the cover material (150) is plate-shaped prior to the heating (225) and is bonded to a bottom material (155) attached to an opposite side of the assembly (100) during the pressing (235).The method (200) of claim 2, wherein the cover material (150) is welded to the floor material (155).Method (200) according to claim 2 or 3, wherein the base material (155) is thermoplastic, heated before the pressing (235), pneumatically pressed (235) together with the cover material (150) onto the assembly (100) and cooled (240) after the pressing (235).The method (200) of claim 1, wherein the cover material (150) forms a bag before the heating (225) and the assembly (100) is placed in the bag before the pressing (235).The method (200) of claim 1, wherein the covering material (150) forms a tube before the heating (225) and the assembly (100) is inserted into the tube before the pressing (235).The method (200) according to any one of the preceding claims, wherein a passing element (135, 160) is attached to the material (150, 155); wherein the element (135, 160) is connected to the assembly (100) before the pressing.The method (200) of any preceding claim, wherein a mechanical attachment point (160) is formed on the material (150, 155).Method (200) according to one of the preceding claims, wherein a thermal guide element (125) is attached to the assembly (100) before the pressing.Method (200) according to one of the preceding claims, wherein a protective gas is conducted between the assembly (100) and the material (150, 155) before the pressing.Method (200) according to one of the preceding claims, wherein the material (150, 155) comprises a planar shielding element.The method (200) according to any one of the preceding claims, wherein the assembly (100) is successively provided (235) with a first and a second heated thermoplastic covering material (150); wherein the first material (150, 155) is softer than the second.Housing shell (140) for an electrical assembly (100), wherein the housing shell (140) is adapted to the assembly (100) by means of thermoforming, wherein a method according to claim 1 is carried out for the housing.Electrical assembly (100), in particular for use on a motor vehicle, wherein the assembly (100) is accommodated in a housing shell (140) according to claim 13.Motor vehicle comprising an electrical assembly (100) according to claim 14.

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