Electronic modular unit, in particular capacitive proximity sensor for a vehicle and method of producing the modular unit

Abstract

An electronic modular unit having electronics has a printed circuit board, a housing receiving the electronics and an electrical conductor. The conductor is in this connection directly soldered with a flat connection end to a contact surface of the printed circuit board. In order to simplify the soldering process, a spring element is arranged in the housing and presses the connection end of the conductor on the contact surface of the printed circuit board for the purpose of fixing the connection end during soldering. The modular unit is, in particular, a capacitive proximity sensor for a vehicle.

Claims

1. An electronic modular unit, comprising: electronics having a printed circuit board with a contact surface; a housing receiving said electronics; an electrical conductor having a flat connection end directly soldered to said contact surface of said printed circuit board; and a spring element disposed in said housing and pressing said flat connection end of said electrical conductor on said contact surface of said printed circuit board for fixing said flat connection end during soldering.

2. The electronic modular unit according to claim 1, wherein: said housing has a housing wall; and said spring element has a spring arm projecting from said housing wall.

3. The electronic modular unit according to claim 2, wherein said spring arm is oriented precisely or approximately parallel to said printed circuit board and has a free end, said spring element having a stamp, which is oriented precisely or at least approximately perpendicular to said printed circuit board, is formed on said free end of said spring arm.

4. The electronic modular unit according to claim 1, wherein said spring element is integrally connected to said housing.

5. The electronic modular unit according to claim 1, wherein said printed circuit board has a pair of tapered apertures formed therein; and further comprising at least one alignment pin disposed in said housing and penetrating said pair of tapered apertures in said printed circuit board and in said flat connection end to position said flat connection end with respect to said printed circuit board.

6. The electronic modular unit according to claim 1, wherein: said housing has a first housing part and at least one second housing part; said electronics are enclosed in said first housing part; and said spring element projects from said second housing part such that said spring element is pressed against said flat connection end.

7. The electronic modular unit according to claim 6, wherein said electrical conductor is guided out of said housing between an edge of said first housing part and an edge of said second housing part in a positionally fixed manner.

8. The electronic modular unit according to claim 1, wherein the electronic modular unit is a capacitive proximity sensor for a vehicle.

9. A method for producing a modular unit, which comprises the steps of: providing a printed circuit board with a solder deposit in a region of a contact surface; inserting the printed circuit board with the solder deposit into a housing; inserting a conductor having a connection end into the housing, with a result that the connection end is clamped between the solder deposit and a spring element; and melting the solder deposit by location-selective heating for direct soldering of the connection end to the contact surface.

10. The method according to claim 9, which further comprises heating the printed circuit board from an underside of the printed circuit board which faces away from the contact surface in order to melt the solder deposit.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a diagrammatic, perspective view of a top of a capacitive proximity sensor with a control unit containing electronics and a flat-conductor electrode connected thereto, wherein a connection end of the flat-conductor electrode is guided into a housing of the control unit in order to make contact with the electronics and wherein the electronics and the connection end brought into contact therewith are over molded with a molding compound;

(2) FIG. 2 is a perspective, bottom view of the proximity sensor according to FIG. 1;

(3) FIG. 3 is a perspective view which is rotated with respect to FIG. 1 with a view of the top of the proximity sensor in that figure in a non-over molded state;

(4) FIG. 4 is a perspective view of the housing of the control unit formed by a tub-like first housing part and a second housing part embodied as a wall insert;

(5) FIG. 5 is a perspective view of the first housing part of the housing; and

(6) FIG. 6 is a simplified section view taken along the line VI-VI shown in FIG. 3 through the proximity sensor in a pre-assembly state.

DETAILED DESCRIPTION OF THE INVENTION

(7) Mutually corresponding parts are always provided with identical reference signs in all of the figures. Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown a capacitive (proximity) sensor 1 for a motor vehicle. The sensor 1 is used in a tailgate, for example, for touch-free opening.

(8) The sensor 1 contains a control unit 2 and a flat-conductor electrode 3 connected thereto. The flat-conductor electrode 3 is formed by a copper foil acting as electrical conductor, which is coated on all sides (and thus, in particular, on the two flat sides) with a plastic layer acting as insulating and carrier material.

(9) The control unit 2 contains a housing 4 composed of plastic. The housing 4, which is constructed in a tub-like manner, is formed from a housing base 5 (FIG. 2) and four walls projecting approximately at right angles from the housing base. That housing side at which the flat-conductor electrode 3 is inserted into the housing 4 is referred to below as front side. The wall of the housing 4 arranged at the front side is referred to as (front) wall 6. The wall of the housing 4 lying opposite the front wall is referred to as (rear) wall 7. The two remaining, mutually opposing walls of the housing 4 which each connect the front wall 6 to the rear wall 7 are referred to as (side) walls 8.

(10) The housing base 5 is arranged at an underside of the housing 4. The walls 6, 7, 8 each adjoin the housing base 5 with a lower edge. The upper edges of the walls 6, 7, 8 extend as far as a surrounding upper outer edge 9 of the housing 4 in a plane. The housing 4 is preferably open toward the upper side facing away from the housing base 5. However, a cover may also be placed on the outer edge 9 in an alternative configuration (not illustrated).

(11) A bracket 10 projects from each of the side walls 8, in which a bushing for indirectly or directly screwing the housing 4 or the control unit 2 to a vehicle is introduced. The brackets 10 are arranged flush with the outer edge 9.

(12) Two female connectors 11 of an electrical plug-in connector are arranged on the rear wall 7. One of the female connectors 11 (on the left in the illustration) is used here to connect a signal and supply line for the control unit 2. The second female connector 11 (on the right in the illustration) is used to connect a circular-conductor electrode (not illustrated) for the sensor 1.

(13) According to FIG. 1, a housing interior 15 enclosed by the housing 4 is filled with a molding compound 16, for example an epoxy resin. The molding compound 16 abuts each of the walls 6, 7, 8 and finishes with a flat top surface 17 just under the outer edge 9 of the housing 4. The molding compound 16 is used to protect electronics 20 (FIG. 3) arranged in the housing interior 15 and a connection end 21 (FIG. 3) of the flat-conductor electrode 3 (FIG. 3) inserted into the housing 4, by the molding compound sealing the housing interior 15 and the components arranged therein in a manner electrically insulated from the exterior as well as air- and water-tight.

(14) As can be seen in particular from FIG. 2, the housing base 5 has a rectangular outline. However, the housing base 5 is embodied in a manner profiled (in particular, stepped) along its flat extent. Furthermore, three downwardly projecting projections 22 are formed on the outside of the housing base 5 and act, in particular, as screw bosses and to which the electronics 20 are screwed in the mounted state with the housing base 5. In an alternative embodiment, the printed circuit board 25 is not screwed to the housing 4 but only attached thereto via press-fit contacts and the molding compound 16. The apertures in the printed circuit board 25 which correspond to the projections 22 are used in this case merely for the purpose of positioning when inserting the printed circuit board 25 into the housing 4.

(15) FIG. 3 shows the sensor 1 in the non-overmolded state in a view direction toward the top. It can be seen in this illustration that the electronics 20 are formed by a printed circuit board 25, which is populated with electronic components 26 (in particular, a microcontroller) which are not explained in any more detail here. The printed circuit board 25 is plane parallel to the outer edge 9 in the housing 4, wherein it extends almost as far as the walls 6, 7, 8. The printed circuit board 25 is positioned and fixed by the projections 22 and two alignment pins 30 formed on the inside on the housing base 5.

(16) The connection end 21 of the flat-conductor electrode 3 is electrically connected and mechanically attached to a front-side edge of the printed circuit board 25. The flat connection end 21 of the flat-conductor electrode 3 lies flat on a flat, upwardly facing side of the printed circuit board 25.

(17) At the connection end 21, the flat-conductor electrode 3 is subdivided in the transverse direction into three sections 31 delimited from one another by slots. In the region of the two edge-side sections 31, in each case a hole 32 is introduced into the flat-conductor electrode 3, by which the flat-conductor electrode 3 is placed on the respectively assigned alignment pin 30. For this purpose, the holes 32 are preferably manufactured to be undersized with respect to the corresponding alignment pins 30, with the result that the flat-conductor electrode 3 is positioned and fixed in position in a force-fitting manner on the alignment pins 30 both with respect to the housing 4 and with respect to the printed circuit board 25.

(18) In the illustrated exemplary embodiment, the flat-conductor electrode 3 (or the conductor track thereof) is soldered in the region of the central section 31 to a corresponding conductor track on the printed circuit board 25. The central section 31 is therefore also referred to as contact section 33.

(19) The contact section 33 is mechanically decoupled to a certain extent from the edge-side sections 31primarily used for mechanically holding the flat-conductor electrode 3by the slots between the sections 31. The contact section 33 and the solder point connecting the former to the printed circuit board 25 are relieved of strain as a result.

(20) FIG. 4 shows the empty housing 4 with a view into the housing interior 15 delimited by the housing base 5 and the walls 6, 7, 8. It can be seen from this illustration that the housing 4 is formed from two parts, namely a first housing part 40 and a second housing part arranged on the front side. The second housing part includes a part of the front wall 6 and is therefore referred to below as wall insert 41.

(21) A surface 42, arranged on the outside of the housing, of the wall insert 41 has a substantially trapezoid shape. An eyelet 44 is formed in each case on both sides at the lower edge 43 of the surface 42. A longitudinal recessed grip 45 is formed in the wall insert 41 close to the upper edge of the surface 42.

(22) The first housing part 40 is shown in a detail illustration in FIG. 5. It can be seen from the illustration that a number of contact elements 50 (press-fit contact elements) project from the housing base 5 in the housing interior 15 in the rearward area of the housing part 40, are assigned to the female connectors 11 and penetrate corresponding contact openings in the printed circuit board 25 (see FIG. 3) in the installation state of the electronics 20. The two alignment pins 30 project from the housing base 5 in the housing interior 15 close to the front wall 6, the alignment pins servingas can be seen in FIG. 3as positioning means for the flat-conductor electrode 3 and the printed circuit board 25. Furthermore, a reinforcing web 51, which likewise projects from the housing base 5, for the printed circuit board 25 can be seen.

(23) The first housing part 40 forms the housing base 5, the walls 7 and 8 and an edge-side part of the front wall 6. An approximately rectangular cutout 55 is introduced into the front wall 6 from the outer edge 9 and is used as bushing for the flat-conductor electrode 3 from the housing 4. In the final assembled state of the control unit 2, the cutout 55 is filled in by the wall insert 41.

(24) In order to fasten the wall insert 41 to the housing part 40, a web 57 is in each case formed along the two opposing side edges 56 of the cutout 55. The webs 57 interact here with an assigned groove 58 (FIG. 3) of the wall insert 41 to form a tongue-and-groove connection. By means of the tongue-and-groove connection, the wall insert 41 can be slid into the cutout 55. The lower edge 60 of the cutout 55 is embodied without a web.

(25) Two latching lugs 61 are formed on the housing part 40 at the lower end of the front wall 6. The latching lugs 61 interact with the eyelets 44 of the wall insert 41 to form a latched connection and are thus used to latch the wall insert 41 into the cutout 55 (FIG. 4).

(26) In an exemplary embodiment, the cutout 55 extends over approximately 40% of the height of the front wall 6 and over approximately 65% of the width of the front wall 6. The width of the cutout corresponds approximately in this case to the width of the flat-conductor electrode 3. The lower edge 60 of the cutout 55 is approximately at the height of the correctly inserted printed circuit board 25.

(27) It can be seen when looking at FIG. 1 and FIG. 3 that the molding compound 16, which is poured in a liquid state during the manufacturing process of the modular unit 1, would flow out of the housing 4 through the cutout 55 were it not for the wall insert 41. The wall insert 41 is therefore used as a barrier for the molding compound 16.

(28) FIG. 6 shows a section (not illustrated to scale) of the modular unit 1 taken along the line VI-VI shown in FIG. 3. It can be seen here that the flat-conductor electrode 3 is inserted into the housing 4 between the lower edge 60 of the cutout 55 and an inside lower edge 70 of the wall insert 41. It can also be seen that the wall insert 41 has a wall thickness which is greater than the wall thickness of the surrounding front wall 6. The wall insert 41 is divided into a ledge 71, which is embodied in a substantially complementary manner to the cutout 55, and the surface 42, which is formed on the ledge 71 on the housing exterior. In particular, the ledge 71 has approximately the thickness of the surrounding region of the housing part 40 and finishes flush with the surrounding wall 6 in the interior. The surface 42 projects in its flat extent both laterally and downwardly over the cutout 55 (see also FIG. 4).

(29) As a result of this, a stepped (L-shaped in cross section) gap 80 is formed at the lower edge 60 of the cutout 55 between the wall insert 41 and the housing part 40, through which gap the flat-conductor electrode 3 is guided, with the result that the flat-conductor electrode 3 is clamped between the wall insert 41 and the housing part 40. The housing bushing described therefore provides the flat-conductor electrode 3 with effective strain relief.

(30) Furthermore, the wall insert 41 supports the soldering process for electrical connection of the flat-conductor electrode 3 to the electronics 20.

(31) In order to explain the soldering process, the modular unit 1 is shown in a pre-assembled state in FIG. 6. In this pre-assembled state, the printed circuit board 25which was previously populated with the electronic components 26 outside of the housing 4has already been inserted into the housing part 40 and fixed there. Furthermore, the flat-conductor electrode 3 with the connection end 21 has been guided into the housing 4 and fixed to the housing part 40 by latching of the wall insert 41. In the pre-assembled state according to FIG. 6, the flat-conductor electrode 3 has not yet been soldered to the printed circuit board 25, however.

(32) As can be seen in FIG. 6, an electrically conductive contact surface 90 is applied on the printed circuit board 25, the area of which contact surface corresponds approximately to the contact section 33 of the flat-conductor electrode 3. The flat-conductor electrode 3 is laid in the housing 4 such that the contact section 33 aligns with the contact surface 90. In this connection, in order to solder the contact section 33, a solder deposit 91 has been applied to the contact surface 90 during the population of the printed circuit board 25.

(33) In order to fix the contact section 33, a spring element (referred to below as hold-down element 92) is formed in one piece on the inside of the wall insert 41 (see also FIG. 3). According to FIG. 6, the hold-down element 92 is formed by a preloaded arm 93 projecting from the wall insert 41, on which arm a stamp 94 which projects downward from the arm 93 is formed. A free end 95 of the stamp 94 abuts the assigned contact section 33 and pushes same against the contact surface 90 and the solder deposit 91 applied thereto.

(34) For the soldering process, the solder deposit 91 is now melted by location-selective heat supply, with the result that when the solder resolidifies, a permanent electrical connection between the flat-conductor electrode 3 and the contact surface 90 of the printed circuit board 25 has been produced.

(35) In a variant of the method, the heat required for the soldering process is supplied by a hot soldering tool (soldering tip) which is placed on an underside of the printed circuit board 25 in alignment with the contact surface 90. Alternatively, the solder deposit 91 is heated using induction. In both cases, the heat is applied to the side of the printed circuit board 25 which faces away from the contact surface 90. The contact section 33 is fixed relative to the contact surface 90 by the hold-down element 92 during the soldering process. External means for fixing the contact section 33 are therefore advantageously neither necessary nor provided.

(36) In order to be able to introduce the soldering tool from below to the printed circuit board 25 installed in the housing 4, the housing base 5 is provided with an access opening 96 in the region of the reinforcing web 51. In order to conduct in a targeted manner the heat supplied from below inside the printed circuit board 25 to the contact surface 90 and the solder deposit 91 applied thereto, a metal insert 97, which acts as a heat-conducting bridge, is preferably let into the printed circuit board 25 in alignment with the contact surface 90.

(37) After the manufacture of the solder connection, the (assembled) housing 4 is filled with the liquid molding compound 16, which then solidifies and thus hermetically seals the housing 4. The access opening 96 is also sealed with molding compound in the same molding step or subsequently.

(38) The subject matter of the invention is not restricted to the exemplary embodiment described above. Instead, further embodiments of the invention can be derived from the above description by a person skilled in the art. In particular, the described individual features of the invention and the variant configurations thereof may also be combined with one another in a different way.

(39) The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention. List of reference signs: 1 (proximity) sensor 2 control unit 3 flat-conductor electrode 4 housing 5 housing base 6 (front) wall 7 (rear) wall 8 (side) wall 9 outer edge 10 bracket 11 female connector 15 housing interior 16 molding compound 17 top surface 20 electronics 21 electronics 22 projection 25 printed circuit board 26 electronic component 30 alignment pin 31 section 32 hole 33 contact section 40 housing part 41 wall insert 42 surface 43 edge 44 eyelet 45 recessed grip 50 contact element 51 reinforcing web 55 cutout 56 side edge 57 web 58 groove 60 edge 61 latching lug 70 edge 71 ledge 80 gap 90 contact surface 91 solder deposit 92 hold-down element 93 arm 94 stamp 95 free end 96 access opening 97 metal insert