Electronic component with laser direct structuring

Abstract

Electronic component in the form of a coil former (10) for surface mounting on a circuit board, wherein the component comprises at least one solder pad (16) made of electrically insulating material, the material containing a metal-organic additive enabling laser direct structuring (LDS) for conductor track generation, the solder pad (16) having a lower terminal element (18) formed on the underside of the solder pad (16) and having an electrically conductive lower surface (20) to be soldered to the circuit board, and an upper terminal element (22) with an electrically conductive upper winding section for a connecting wire projecting outwards from the solder pad (16) and spaced apart from the lower terminal element (18), the lower boundary of the lower terminal element (18) projecting beyond the lower boundary surface (59) of the solder pad (16) by a distance (A).a connecting piece (32) between lower connecting element (18) and upper connecting element (22) has an inclined surface, and wherein the underside of the lower connecting element (18), the underside of the upper connecting element (22) and a connecting section (34) of the inclined surface of the connecting piece (32) are each provided with an electrical conductor, the insulating material contains a crosslinking amplifier by which a short-term temperature load of the upper connecting element and / or the lower connecting element is achievable in a time range of 5 s to 10 s and in a temperature range of 300 °C to 450 °C, and wherein an electrical conductor (34) is formed by laser direct structuring and subsequent chemical layer build-up.

Description

The invention relates to an electronic component in the form of a coil body which is to be soldered on a circuit board in a surface mounting manner, wherein the component comprises at least one integrally connected soldering support point consisting of electrically insulating material.A component of this type as a coil body is known from DE 39 10 750 C3. The solder support point described therein includes a lead wire held in a U-shape within the solder support point. The underside of the connecting wire serves for soldering to conductor tracks of a printed circuit board or a circuit board. An upper portion of the wire constitutes a winding portion to which a lead wire for the electronic component is wound. In this way, an electrically conductive connection from the electronic component to the conductor track is created on the printed circuit board. The lower portion of the wire protrudes a distance from the lower boundary surface of the component, so that after soldering, a space still remains between the body of the component and the printed circuit board.Furthermore, JP 2005-327 887 A discloses a component having numerous features of claim 1, with the exception of features which relate to laser direct structuring. DE 10 2006 061 722 A1 describes that the material contains an organometallic additive which enables direct conductor track structuring (LDS) for conductor track generation.Further prior art is described in the documents JP S50-18 953 U, US 2010 / 0 307 799 A1, U.S. Pat. No. 5,212,345 A, US 2011 / 0 025 441 A1 and JP H04-42 720 U.It is an object of the invention to specify an electronic component as a coil body, the electrical and mechanical properties of which are improved.This object is achieved by the combination of the features of claim 1. Advantageous further developments are specified in the dependent claims.According to the invention, the component designed as a coil body comprises at least one soldering base point consisting of electrically insulating material, wherein the material contains an organometallic additive which enables laser direct structuring (LDS) for generating conductor tracks. This laser direct structuring is a technology with which the surface of plastics is changed in its conductivity by laser light. In this way, conductor tracks can be applied to three-dimensional plastic molded parts. The plastic material is activated with a laser beam at the locations at which the conductor tracks are to be later built up. In this process, a chemical reaction takes place on the plastic surface, in which nuclei form which act as catalysts during the metal coating. A metal layer, in particular a copper layer, is then built up in an electroless (non-electroplating) chemical bath, wherein conductor track thicknesses of several μm are produced. The conductor track produced in this way is then coated with further metal layers, for example a nickel layer and / or a gold layer.In the invention, a lower terminal member has an electrically conductive lower pad to be soldered to the circuit board. An upper terminal element substantially comprises a protruding upper winding portion having an electrically conductive surface. At this winding-on section, a connecting wire is wound on, which leads to an active or passive electronic part, e.g. to a coil. A connecting piece runs between the lower connection element and the upper connection element, the surface of which connecting piece is likewise provided with an electrical conductor track. In this way, a continuous electrically conductive connection is created between the winding section and the lower connection element, so that it is possible to connect the electronic component electrically to a conductor track of a printed circuit board and thus to further electrical components of an electrical circuit arrangement.The electrically conductive lower coating has a relatively large area, thereby allowing a large contact area to the conductive trace on the circuit board, resulting in improved soldering and electrical contact. In the region of the winding-on section, too, different structural solutions result, according to which the mechanical stability of the winding-on section and / or the electrical contactability and solderableness are improved.The lower boundary of the connection element protrudes beyond the lower boundary surface of the soldering support point by a distance. This creates an intermediate space for the component, which allows cooling air to circulate and improves the precise positioning of the component on conductor tracks of the printed circuit board and thus the solderable nature.In the invention, the insulating material contains a crosslinking enhancer, by means of which a short-term temperature load of the upper connection element and / or of the lower connection element is achieved in a time range from 5 s to 10 s and in a temperature range from 300° C. to 450° C. This measure ensures that a low failure rate is achieved during the soldering process. The measure mentioned is particularly critical with regard to the soldering process in which a connecting wire of the electronic component, for example a coil, has to be soldered to the upper winding section. This connecting wire has an insulating lacquer layer which has to be removed during the soldering process. Therefore, this soldering process is performed in a relatively high temperature range of 390° C. to 410° C. in a time period of 0.5 s to 1 s. The insulating material to be used must survive this soldering process without loss of quality.Exemplary embodiments of the invention are explained below with reference to the drawings. Shown therein are: FIG. 1 shows a component in the form of a coil body, FIG. 2 shows the coil body according to FIG. 1 with modified winding sections, FIG. 3 shows another embodiment with convex upper winding sections, FIG. 4 shows an embodiment with trapezoidal upper winding sections and lower-lying connecting sections, FIG. 5 shows a coil body in which a plurality of upper connection elements are connected to one another by conductor tracks, and FIG. 6 shows an embodiment with protruding plate elements.FIG. 1 shows a coil body 10 as an electronic component, which is shown with its underside upwards. This bobbin 10 is an SMD (surface mounted device) component and has a hollow central body 12 around the circumference of which a coil (not shown) can be arranged. The interior 14 of the body 12 is used to receive a ferrite core. The coil body 10 is formed integrally with a plurality of similar soldering support points, of which only one is provided with the reference sign 16 for reasons of better clarity. The entire coil body 10 is produced as an injection-molded part from thermoplastic material, preferably from polyamide, and contains an organometallic additive, which enables laser direct structuring for generating conductor tracks.Each solder pad 16 has a lower terminal 18 formed on the underside of the solder pad 16 and carries an electrically conductive pad 20, which electrically conductive pad 20 is to be soldered to a circuit board (not shown). The solder support point 16 further includes an upper terminal element 22 which projects outwardly from the solder support point 16 and is spaced from the lower terminal element 18. The upper connection element 22 likewise has an electrically conductive coating and forms a winding section for a connection wire of a coil.The lower connecting element 18 is in the form of a skid with a base 30 and inclined lateral skid surfaces 26, 28, which are designated in the right-hand part of FIG. 1. This right-hand part of the figure is drawn without electrically conductive coatings, so that various details can be seen better. During the production of the coil body, the lateral surfaces 26, 28 and the base surface 30 are provided with an electrically conductive layer. As can be seen, this base area 30 can be substantially larger than, for example, in the case of a wire, so that good electrical contact and a large-area soldering area are created on a circuit board when soldering to a conductor track. Due to the additionally metallized oblique skid surfaces 26, 28, the electrical resistance for the contacting can be further reduced. Furthermore, due to capillary forces during soldering, soldering material is deposited in the region of the oblique runner surfaces 26, 28, which improves the quality of the soldering connection.In the upper connection element 22, a runner shape with a base surface 30 and oblique lateral runner surfaces is likewise formed (see right-hand part of the figure). As can be seen in the left-hand part of the figure, these surfaces are provided with an electrically conductive coating. The upper terminal member 22 constitutes the upper winding portion around which the lead wire for the coil is wound and then soldered. Here too, relatively large soldering areas and electrically conductive contact areas are provided, so that a high production quality is produced.The upper connection element 22 and the lower connection element 18 are integrally connected to one another via a connecting piece 32. The connecting piece 32 has a surface running obliquely between the lower connecting element 18 and the upper connecting element 22, on which surface an electrical conductor track 34 is formed by direct laser structuring and subsequent chemical layer construction. This electrical conductor track 34 provides the electrical connection between the electrical coatings of the upper connection element 22 and of the lower connection element 18.Between the various soldering support points 16 there are formed groove-shaped depressions 36, by means of which a high creepage resistance is ensured.In the case of direct laser structuring, as mentioned, a laser beam is guided over the surface of the plastic material at the locations at which a metal layer is to be built up during the subsequent chemical metallization. The exposure to the laser beam is generally carried out from above by deflecting the laser in the X-Y direction. Viewed from one side, an exposure can advantageously take place only where there is no shading of the laser light, which is why oblique surfaces, such as the lateral runner surfaces 26, 28, can still be sufficiently exposed and subsequently metallized.FIG. 2 shows a further development of the exemplary embodiment according to FIG. 1, in which the upper connection element 22 or the winding-on section is provided completely with an electrical coating on its circumferential lateral surface. This is made possible by exposing this lateral surface both from above and from below by means of laser radiation and then chemically metallized. Alternatively, the bobbin 10 may be exposed once from one side (e.g., from above), then turned over, and exposed a second time from that side (e.g., from above).FIG. 3 shows a further exemplary embodiment in which the upper connection element 22 is oval in cross section. A portion of its surface is provided with a convexly extending electrically conductive coating 38. The lower terminal element 18 has a skid shape with lateral vertical skid surfaces 40 which are not metallized. The oval shape of the winding-on section is advantageous since it facilitates the winding-on of the connecting wire.FIG. 4 shows a further exemplary embodiment in which the upper connection element 22 is trapezoidal in cross section. The upper side of the trapezoid shown (in the installed position, this is the lower side) is provided with the electrically conductive coating. The conductive path 42 of the connecting piece 32 is formed in a depression 44. This has the advantageous technical effect that the leakage current resistance is further improved due to the depression in the insulating material.FIG. 5 shows a further exemplary embodiment for the coil body 10, wherein an electrical interconnection is carried out by electrically conductive bridges. The left-hand part of the drawing shows an embodiment in which the electrically conductive coatings of three lower connection elements 50, 52, 54 are connected to one another by an electrically conductive coating 56. This means that the lower connection elements 50, 52, 54 are electrically connected in parallel and have the same electrical potential. In this way, the electrical contacting can be improved and the electrical resistance can also be reduced.It can be seen from FIG. 5 that the lower boundary of the lower connection element 58, formed by its electrically conductive coating, protrudes beyond the lower boundary surface 59 of the coil body 10 by a distance A. This distance A ensures that the coil body 10 can be positioned and soldered precisely on a printed circuit board.In the right-hand part of the drawing, another variant of an electrical interconnection can be seen, in which a lower connection element 58 is designed to be electrically separated from other connection elements. Two further connection elements 60, 62 are connected to one another via an electrically conductive bridge 64 and are thus connected electrically in parallel.FIG. 6 shows an embodiment of a coil body 10, in which above the upper connection element 22 (viewed in the use state) plate elements 70 are formed integrally on both sides, which project outwards beyond the upper connection elements 22. As a result of this measure, the creepage distance toward the ferrite core in the coil body 10 is further increased, and therefore the creepage current resistance is further improved. In this way, a compact design for the coil body 10 with optimized electrical properties is possible. In the right-hand part of the figure, the lower connection element 18 is shown to have a corrugated surface 72. After metallization, this surface perforation is still present. It improves the solderableness of the metal surface.List of reference characters10 Coil body 12 Central body 16 Solder base 18 Lower connection element 20 Electrically conductive coating 22 Upper connection element 26, 28 Skid surfaces 30 Base surface 33 Connecting piece 34 Conductor track 36 Depressions 38 Electrically conductive coating 40 Perpendicular skid surfaces 42 Conductor track 44 Depression 50, 52, 54 Lower connection elements 56 Electrical coating 58, 60, 62 Lower connection elements 59 Lower boundary surface 70 Plate element 72 Corrugated surface

Claims

Electronic component in the form of a coil body (10) which is to be soldered on a circuit board in surface mounting, wherein the component comprises at least one soldering support point (16) which consists of electrically insulating material, the material containing an organometallic additive which enables laser direct structuring LDS for conductor track generation, the soldering support point (16) has a lower connection element (18) which is formed on the underside of the soldering support point (16) and has an electrically conductive lower coating (20) which is to be soldered to the circuit board, and an upper connection element (22) having an electrically conductive upper winding section for a connection wire which projects outwards from the soldering support point (16) and is spaced apart from the lower connection element (18), the lower boundary of the lower connection element (18) protrudes beyond the lower boundary surface (59) of the solder support point (16) by a distance (A), a connecting piece (32) between the lower connection element (18) and the upper connection element (22) has an obliquely running surface, and wherein the underside of the lower connection element (18), the underside of the upper connection element (22) and a connecting section (34) of the obliquely running surface of the connecting piece (32) are each provided with an electrical conductor track, the insulating material contains a crosslinking amplifier, by means of which a short-term temperature load of the upper connection element and / or of the lower connection element can be achieved in a time range of 5 s to 10 s and in a temperature range of 300° C. to 450° C., and wherein an electrical conductor track (34) is formed by laser direct structuring and subsequent chemical layer structure.Component according to Claim 1, characterized in that the insulating material consists of thermoplastic material, in particular substantially of polyamide.Structural element according to one of the preceding claims, characterized in that the lower connection element (18) has a skid shape with oblique lateral skid surfaces (26, 28), wherein the base surface (30) of the skid shape and the lateral skid surfaces (26, 28) are provided with an electrically conductive coating.Structural element according to one of the preceding claims, characterized in that the upper winding-on section comprises a trapezoidal shape in cross section.Component according to one of the preceding claims 1 to 4, characterised in that the upper winding-on section is formed convexly in cross-section and its surface is provided with a convexly running electrically conductive coating.Component according to one of the preceding claims, characterized in that the upper winding-on section is provided completely with an electrical coating on its circumferential lateral surface.Component according to one of the preceding claims, in which the conductor track (42) of the connecting piece (32) is formed in a depression (44).Structural element according to one of the preceding claims, characterized in that a plate element (70) is formed integrally on it above the upper connection element (22), said plate element projecting outwards beyond the upper winding-on section.Structural element according to one of the preceding claims, characterized in that the lower connection element (18) has a corrugated surface (72).Component according to one of the preceding claims, characterized in that the conductive coatings of a plurality of upper connection elements and / or of a plurality of lower connection elements (50, 52, 54; 60, 62) are connected to one another by conductor tracks.

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