Method for establishing an electrical connection between a printed circuit board and a connection wire, and electrohydraulic actuator

Abstract

The invention relates to a method for establishing an electrical connection between a printed circuit board (1) and a connection wire (2), wherein the printed circuit board (1) is provided with a metallization area (11), the method comprising the following steps: - providing a housing part (7), which is provided with a wall (72) and at least one projection (75) projecting in relation to the wall (72), - applying a material deposit (16) composed of an electrically conductive paste (17) to the wall (72) of the housing part (7) in a locally limited region (74) outside the projection (75), - placing a portion (21) of the connection wire (2) onto the material deposit (16), wherein the portion (21) of the connection wire (2), by way of its outer sheath (22), adheres to the material deposit (16), - mounting the printed circuit board (1) onto the housing part (7) in such a way that the metallization area (11) of the printed circuit board (1) faces the portion (21) of the connection wire (2), and - pressing the printed circuit board (1) in the direction of the wall (72) of the housing part (7) until the printed circuit board (1) comes into contact with the projection (75), wherein the portion (21) of the connection wire (2) is pushed into the material deposit (16) by the metallization area (11), until the electrically conductive paste (17) of the material deposit (16) covers the metallization area (11) of the printed circuit board (1).

Description

[0001] Description

[0002] title

[0003] Method for establishing an electrical connection between a printed circuit board and a connecting wire and electrohydraulic actuator

[0004] State of the art

[0005] In the prior art, for example, electrohydraulic actuators are used to control hydraulic systems. These actuators comprise an electromagnet with a solenoid coil and a valve member with a valve element. The valve element, actuated by the electromagnet, can open or close variously designed inlet and outlet openings on the valve member, thereby adjusting the pressure at one or more hydraulic consumers or a pressure channel. Such electrohydraulic actuators can be controlled via a control unit that adjusts the electrical current through the solenoid coil of the electromagnet.

[0006] In the prior art, electrohydraulic control devices are used to control electrohydraulic actuators. These devices are used, for example, in automotive transmissions. They are generally designed as complex electronic modules with pressure sensors, speed sensors, and other functions, and can be used to control multiple electrohydraulic actuators. For example, DE 101 30 833 B4 discloses an electrohydraulic control device that has a hydraulic block with a component side and is provided with hydraulic channels. Several electrohydraulic actuators are arranged on the hydraulic block, each engaging a valve section from the component side into a receiving opening in the hydraulic block. An electronic control unit comprises a printed circuit board designed as a large-area connecting insulation layer with conductor tracks embedded therein.A central section of this circuit board acts as a circuit carrier and is equipped with the electronic components of a control circuit, which are covered by a cover section placed on the circuit board. The circuit board extends outward at the sides over the cover section and has electrical contacts at its edges, each of which is electrically connected to the electrical terminals of an electrohydraulic actuator.

[0007] In existing solutions, all actuators are usually controlled via a common electronic control unit (ECU), which can determine the required actuating currents for the actuators using a microprocessor, for example, and provides the actuating currents to the actuators' electromagnets via power amplifier modules integrated into the control unit. The ECU has multiple power amplifiers, allowing multiple actuators to be controlled via this ECU.

[0008] New developments and fields of application require that electrohydraulic actuators are no longer operated via an output stage module in a central control unit, but preferably be addressed via a bus system (e.g., CAN or LIN). However, the actuating current required to generate the actuating forces must then be generated in or on the actuator from a battery voltage. There is therefore a need for hydraulic actuators (so-called "smart actuators") that can be integrated into a small, flexibly deployable unit with an electronic control unit located directly in or on the actuator and assigned to the actuator.

[0009] This raises the fundamental problem of how the coil winding of an actuator's electromagnet is to be electrically connected to the control unit's circuit board. The coil winding of an electromagnet has a very thin wire that is rather slack. Mounting the connecting wire in the through-hole mounting method familiar for printed circuit boards in a contact opening of the circuit board, similar to the conventional electronic wire components mounted on the circuit board, is therefore generally not possible or only possible with considerable additional technical effort.

[0010] Known electrical connection technologies between the connecting wires of an electromagnet's coil winding and a circuit board therefore use intermediate connecting means to achieve reliable contact. For example, DE 44 27 767 C2 shows a coil winding whose connecting wires are wound around the electromagnet's connector plugs and overmolded with a plastic coil housing. Exposed ends of the connector plugs extend from the coil housing as connector tabs. The sturdy connector tabs can be used for further contact with the circuit board, whereby additional contact elements can be inserted between the connector tabs and the circuit board.

[0011] DE 103 37 197 B4, for example, discloses further contacting via contact elements designed as spring elements, which are part of the electromagnetic actuator and are connected to the coil winding. The spring-loaded contact elements can be pressed against a metallization surface on a circuit board with their ends facing away from the actuator. However, these solutions require a considerable amount of installation space.

[0012] Disclosure of the invention

[0013] The invention relates to a method of electrical connection between a printed circuit board and a connecting wire, wherein the printed circuit board is provided with a metallization surface on at least a first side, characterized by the following steps:

[0014] - Providing a housing part which is provided with a wall and at least one projection projecting from the wall,

[0015] - applying a material layer of an electrically conductive paste in a locally limited area outside the projection onto the wall of the housing part,

[0016] - Placing a section of the connecting wire onto the material deposit, whereby the section of the connecting wire adheres to the material deposit with its outer sheath,

[0017] - Placing the printed circuit board on the housing part in such a way that the metallization surface of the printed circuit board is aligned with the section of the connecting wire and

[0018] - Pressing the circuit board towards the wall of the housing part until the circuit board comes into contact with the projection with the first side, wherein the section of the connecting wire is pressed from the metallization surface into the material application until the electrically conductive paste of the material application covers the metallization surface of the circuit board.Furthermore, the invention relates to an electro-hydraulic actuator produced by the method presented here, which has a valve part, an electromagnet with a coil winding, a magnet armature movably mounted in the electromagnet and a valve member actuated by the magnet armature and arranged in the valve part, wherein the electro-hydraulic actuator further comprises at least one printed circuit board which is arranged on a wall of a housing part on at least one projection protruding from the wall, wherein the housing part is arranged on an actuator housing of the actuator and wherein at least one connecting wire of the coil winding is electrically conductively connected to a metallization surface of the circuit board by means of a material application of an electrically conductive paste arranged between the wall of the housing part and the metallization surface and covering the metallization surface.

[0019] In the context of the present application, a material application of an electrically conductive paste is understood to mean a material application of a viscous material with a sufficiently high viscosity (preferably over 10,000 cPs [cPs = centipoise]) so as not to flow away from the application site. The electrically conductive paste has a low modulus of elasticity and is therefore easily deformable under low pressure. It is preferably an electrically conductive adhesive, for example, a silicone paste or a silicone adhesive.

[0020] Advantages of the invention

[0021] The method presented here describes a possibility of electrically and mechanically connecting a connecting wire to a metallization surface on a printed circuit board using only a few, easily manageable process steps. To do this, a layer of electrically conductive paste is first applied in a localized area outside a projection on the wall of a housing part, which can be done using a dispenser, for example. The housing part can in particular be designed as a housing half-shell made of plastic and can serve to hold the circuit board. The electrically conductive paste can in particular comprise an electrically conductive adhesive. A section of the connecting wire is then placed onto the layer of material, with the section of the connecting wire adhering to the layer of material with its outer sheath.The section of the connecting wire can be freed from any insulation covering the rest of the connecting wire and, if necessary, cleaned beforehand so that the electrically conductive material of the connecting wire is in direct contact with the material deposit. In the next process step, the circuit board is placed on the housing part, with the metallization surface of the circuit board facing the section of the connecting wire. In the final process step, the circuit board is pressed towards the wall of the housing part, or pressed until the first side of the circuit board comes into contact with the projection. At the same time, the section of the connecting wire is pressed from the metallization surface into the material deposit until the electrically conductive paste of the material deposit covers the metallization surface of the circuit board.The connecting wire is now reliably electrically connected to the metallization surface of the circuit board via the electrically conductive paste.

[0022] Without being limited to this, the process is particularly suitable for a flexible connecting wire, in particular the connecting wire of a coil winding of a magnetic coil, which would not be suitable even for through-hole mounting. Apart from the application of conductive paste, no further connecting means are required. In particular, no complex intermediate contact means are required. Soldering the connecting wire into the circuit board is also unnecessary. Therefore, the manufacturing effort for the electrical connection between the connecting wire and the circuit board can be significantly reduced.

[0023] The integration of a control circuit into an electromagnetic actuator can only be achieved with a space-saving solution for the electrical connection between the circuit board and the connecting wires of the coil winding. The method presented here therefore represents a particularly suitable solution for this task, whereby the method requires a few manageable connection steps and few components and enables a space-reduced electrical connection between a metallization surface of the circuit board of the control circuit and the coil winding of a magnetic coil. This simplifies or enables the integration of a control unit into an electromagnetic actuator C, "smart actuator"). Advantageous embodiments and further developments of the invention are made possible by the features contained in the dependent claims.

[0024] Advantageously, the section of the connecting wire intended for embedding in the material coating can be circular in cross-section, which simplifies its introduction into the electrically conductive paste.

[0025] For a particularly reliable and stable electrical connection, the section of the connecting wire can advantageously be pressed so deeply into the material deposit that it is completely or almost completely embedded.

[0026] Advantageously, after the step of pressing the circuit board onto the at least one projection, the circuit board can be secured to the housing part using fastening means, in particular screwable fastening means. The screwable fastening means can, for example, be screwed through a designated opening in the circuit board into a receiving opening in the projection provided with a screw thread. Preferably, at least two or more projections are provided for stable fastening of the circuit board. This creates a compact assembly that can be easily processed further.

[0027] The method is particularly advantageous, without being limited thereto, for establishing an electrical connection between a metallization surface of a printed circuit board intended for installation on or in an electrohydraulic actuator and at least one connecting wire of a coil winding of an electromagnet of the electrohydraulic actuator. The housing part can, for example, be manufactured in particular as a housing half-shell made of plastic and serve to accommodate the printed circuit board. The printed circuit board is then mounted, for example, on an inner wall of the housing part. The housing part can then be secured to an actuator housing, wherein the connecting wire of a coil winding, which is in contact with the printed circuit board via the electrically conductive paste, can be easily accommodated in the housing part.

[0028] Also advantageous is an electro-hydraulic actuator produced using the method according to the invention, which comprises a valve part, an electromagnet with a coil winding, a magnet armature movably mounted in the electromagnet, and a valve member actuated by the magnet armature and arranged in the valve part, wherein the electro-hydraulic actuator comprises at least one printed circuit board arranged on a wall of a housing part on at least one projection protruding from the wall, wherein the housing part is arranged on an actuator housing of the actuator, and at least one connecting wire of the coil winding is electrically conductively connected to a metallization surface of the circuit board by means of a material application of an electrically conductive paste arranged between the wall of the housing part and the metallization surface and covering the metallization surface.

[0029] Short description of the drawings

[0030] Possible embodiments of the invention are explained below with reference to the accompanying figures. In the drawing:

[0031] Figures 1 to 5 show a cross section through a section of a printed circuit board during a sequence of method steps for an embodiment of the method according to the invention for producing an electrical connection between a printed circuit board and a connecting wire,

[0032] Figure 6 shows an electrohydraulic actuator manufactured using the method according to the invention.

[0033] Embodiments of the invention

[0034] Figure 1 shows a cross-section through a section of a housing part 7. The housing part 7 is manufactured, for example, as a housing half-shell made of plastic and has a wall 72, which is provided as the inside of an electronics housing, as well as an outer wall 73 facing away from the wall 72. In the exemplary embodiment shown here, the wall 72 has a pedestal, the upper side of which represents a locally limited area 74 of the wall 72, which is provided with a material application 16 consisting of an electrically conductive paste 17. The material application 16 can be applied, for example, using a dispenser. The paste 17 is sufficiently viscous and does not flow out of the area 74, but adheres there. The paste 17 can, in particular, comprise or consist of a viscous, pasty, electrically conductive adhesive.As further shown in Figure 1, the housing part 7 has at least one projection 75 which projects from the housing part 7 and the wall 72. In particular, a plurality of such projections are provided, although only one of these is shown in Figure 1. The projection 75 projects from the wall 72 and extends on the side of the housing part 7 facing away from the outer wall 73 beyond the area 74 to approximately the height of the material application 16. In the exemplary embodiment shown, the end face of the projection 75 which is provided as a stop surface for a printed circuit board 1 and faces away from the housing part 7 is located somewhat below an upper side of the material application 16 facing away from the housing part 7. The projection 75 is formed, for example, by a dome-like extension of the housing part 7 with a circular cross-section which has a central inner recess 76 which can be provided with an internal thread.

[0035] In a further method step shown in Figure 2, a section 21 of a connecting wire 2 with its outer sheath 22 is placed flat on the material deposit 16 so that it adheres thereto. The connecting wire 2 extends from a beginning to an end along a direction of extension, or longitudinal extension, and preferably has a cylindrical outer sheath 22, which can be seen as a circular cross-section in the cross-section of Figure 2 (perpendicular to the direction of extension of the connecting wire). A section 21 of the connecting wire 2 intended for contacting, for example an end section of the connecting wire 2, is stripped and cleaned if necessary and placed flat on the material deposit 16 with the underside of its outer sheath 22.The connecting wire 2 is, without being limited thereto, preferably a connecting wire of a coil winding 23 of an electromagnet, as will be explained below.

[0036] Figure 3 shows how, in a further method step, a printed circuit board 1 is placed onto the housing part 7. The printed circuit board can, for example, be a conventional printed circuit board (PCB = printed circuit board), in particular a multi-layer printed circuit board made of epoxy resin with inner layers made of copper. The printed circuit board 1 has a first side 31 and a second side 32 facing away from the first side 31. The printed circuit board 1 has, for example, on the first side 31, a metallization area 11 made of, for example, copper. A second metallization 12 can be arranged on the second side 32. In addition, the printed circuit board 1 can have a section (not shown) with further metallization areas. The printed circuit board 1 can be intended and provided to be populated with the components of an electronic control circuit.On the first side 31, the circuit board 1 can be provided with a solder resist layer 14 that does not cover the inner region of the metallization surface 11, leaving it exposed. On the second side 32, the circuit board 1 has, for example, a second solder resist layer 14a, which can completely cover the metallization 12 there. Furthermore, the circuit board 1 has at least one opening 15 that completely penetrates the circuit board 1.

[0037] As can be clearly seen in Figure 3, the printed circuit board 1 is placed on the housing part 7 in such a way that the metallization surface 11 of the printed circuit board 1 faces the section 21 of the connecting wire 2. The opening 15 is aligned centrally with the inner recess 76 of the projection 75. By pressing the printed circuit board 1 in the direction of the wall 72 of the housing part 7 (direction of the arrow in Figure 3), the first side 31 of the printed circuit board 1 comes to rest against the end face of the projection 75 facing away from the printed circuit board 1.

[0038] The final state is shown in Figure 4. The circuit board 1 rests with its first side on the projection 75. By pressing the circuit board 1, the section 21 of the connecting wire 2 is pressed from the metallization surface 11 into the material deposit 16 until the electrically conductive paste 17 of the material deposit 16 covers the metallization surface 11 of the circuit board 1. As shown in Figure 4, the metallization surface 11 is preferably completely covered by the electrically conductive paste 17. As can be seen, the section 21 of the connecting wire 2 is pressed deeply into the material deposit 16 and is embedded therein. By pressing the circuit board 1, the material deposit 16 was deformed and flattened and now covers the previously exposed area of ​​the metallization surface 11.

[0039] Finally, as shown in Figure 5, at least one fastening means 18, for example in the form of a screw, can be screwed through the at least one opening 15 of the circuit board 1 into the recess 76, which is preferably provided with an internal thread, so that the circuit board 1 is firmly connected to the housing part 7. The described method is particularly suitable for establishing an electrical connection between a metallization area 11 on the surface of a circuit board 1 intended for installation on or in an electro-hydraulic actuator 3 and at least one connecting wire 2 of a coil winding 23 of an electromagnet 51 of the electro-hydraulic actuator 3.

[0040] Figure 6 shows an example of an electrohydraulic actuator 3 manufactured using the method according to the invention. The electrohydraulic actuator 3 can have a valve part 6, an electromagnet 5 with a coil winding 23, a magnet armature 52 movably mounted in the electromagnet 5, and a valve member 61 actuated by the magnet armature 52 and arranged in the valve part 6, which is supported in the valve part 6 against a spring 62. By displacing the valve member 61, inlet and outlet openings (not shown) of the valve part 6 for a hydraulic fluid can be opened or closed, whereby the hydraulic working pressure at a working connection of the valve part 6 can be adjusted. The electromagnet 5 is provided with an actuator housing 54 formed as a plastic housing, in particular by injection molding. The housing part 7 is attached to one side of the actuator housing 54.The housing part 7 can, as described above, be designed, for example, as a housing half-shell in which a printed circuit board 1 provided with a control circuit (not shown) is arranged. The printed circuit board 1 rests on several projections 75, to which the printed circuit board is screwed. The printed circuit board 1 is connected via electrical connecting means 71 to plug lugs 56 of a connector plug 55 of the electrohydraulic actuator 3, which plug lugs are embedded in the actuator housing 54.

[0041] The electromagnet 5 comprises, for example, a pole tube 53 in which the magnet armature 52 is movably mounted. The magnet armature 52 is fixedly connected to a plunger 58, which protrudes from the pole tube 53 at one axial end thereof and acts on the valve member 61. The pole tube 53 is surrounded by a magnetic coil with the coil winding 23. By energizing the coil winding 23, the magnet armature 52 is moved downward in Figure 6. As a result, the plunger 58 presses the valve member 61 downward in the valve part 6 against the spring force of the spring 62. By reducing the current strength, the magnetic force is reduced, and the valve member 61 is moved upward again in Figure 6 with the assistance of the tension force of the spring 62. As can also be seen in Figure 6, the coil winding 23 has at least one connecting wire 2, which is led out laterally from the actuator housing 54.A contact section 21 of the at least one connecting wire 2 of the coil winding 23 is contacted with the metallization surface 11 on the circuit board 1 by the material application 16 with the electrically conductive paste 17.

[0042] The procedure can be such that the connecting wire 2 of the finished electromagnet 5 is contacted with the housing part 7 removed, using the method shown in Figures 1 to 5. The flexibility of the connecting wire 2 allows the housing part 7 to then be pivoted toward the actuator housing 54 and secured laterally to the actuator housing 54 via a sealing ring, wherein the ends of the connecting means 71 facing away from the circuit board 1 can be pressed into end sections of the connector tabs 56. The connecting wire 2 is accommodated in a protected manner in the housing part 7.

Claims

Claims 1 . A method for producing an electrical connection between a printed circuit board (1) and a connecting wire (2), wherein the printed circuit board (1) is provided with a metallization surface (11) on at least one first side (31), characterized by the following steps: Providing a housing part (7) which is provided with a wall (72) and at least one projection (75) projecting from the wall (72), Applying a material coating (16) of an electrically conductive paste (17) in a locally limited area (74) outside the projection (75) onto the wall (72) of the housing part (7), Placing a section (21) of the connecting wire (2) onto the material deposit (16), wherein the section (21) of the connecting wire (2) adheres to the material deposit (16) with its outer sheath (22), Placing the printed circuit board (1) on the housing part (7) in such a way that the metallization surface (11) of the printed circuit board (1) is directed towards the section (21) of the connecting wire (2) and Pressing the printed circuit board (1) in the direction of the wall (72) of the housing part (7) until the printed circuit board (1) comes to rest with the first side (31) on the projection (75), wherein the section (21) of the connecting wire (2) is pressed from the metallization surface (11) into the material application (16) until the electrically conductive paste (17) of the material application (16) covers the metallization surface (11) of the printed circuit board (1) 2. Method according to claim 1, characterized in that the electrically conductive paste (17) comprises an electrically conductive adhesive.

3. Method according to claim 1 or 2, characterized in that the connecting wire (2) is a connecting wire of a coil winding (23) 4. Method according to one of the preceding claims, characterized in that the section (21) of the connecting wire (2) is circular in cross section.

5. Method according to one of the preceding claims, characterized in that the section (21) of the connecting wire (2) is pressed so deeply into the material deposit (16) that it is completely or almost completely embedded therein.

6. Method according to one of the preceding claims, characterized in that the printed circuit board (1) is fastened to the housing part (7) by fastening means (18) after the step of pressing the printed circuit board (1) onto the projection (75).

7. Method according to one of the preceding claims, characterized in that the method for producing an electrical connection between a metallization surface (11) on a printed circuit board (1) intended for installation on or in an electrohydraulic actuator (3) and at least one connecting wire (2) of a coil winding (23) of an electromagnet (51) of the electro-hydraulic actuator (3).

8. Electrohydraulic actuator (3) comprising a valve part (6), an electromagnet (5) with a coil winding (23), a magnet armature (52) movably mounted in the electromagnet (5) and a (52) actuated valve member (61) arranged in the valve part (6), characterized in that the electro-hydraulic actuator (3) has at least one printed circuit board (1) which is arranged on a wall (72) of a housing part (7) on at least one projection (75) projecting relative to the wall (72), wherein the housing part (7) is arranged on an actuator housing (54) of the actuator, wherein at least one connecting wire (2) of the coil winding (23) is electrically conductively connected to a metallization surface (11) of the printed circuit board (1) by means of a material application (16) comprising an electrically conductive paste (17) arranged between the wall (72) of the housing part (7) and the metallization surface (11) and covering the metallization surface (11).

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