FR3007315A1 - CUTTED CONNECTION GRID AND PROCESS FOR PRODUCING SAME, ASSISTED BY LASER WELDING - Google Patents

Abstract

A core element (1) is provided with conductive tracks which are injection-molded at a first partial area by a first layer of plastics material (2) and then at second partial areas. by a second layer of plastic material (8). The first and second plastic layers overlap reciprocally laterally in overlapping areas (13), and wrap, in common, the entire core member (1). The first layer of plastic material (2) has other optical properties than the second layer of plastic material. After the second injection overmolding, the first plastic layer (2) is welded by laser welding to the second plastic layer (8) forming a material continuity connection.

Description

FIELD OF THE INVENTION The present invention relates to a method of manufacturing a cut-off leadframe, as well as a cut-off leadframe that can be fabricated thereby. State of the art 10 Cut grids with conductive tracks or cut-off connection grids, for example, are used in the automotive industry to make electrical interconnections of control devices. For example, in motor vehicle automatic gearboxes, for the control of clutch and gear shift operations, control modules are used which are located in an inner chamber of a gearbox filled with oil. . Here, to ensure the electrical interconnections, cut-off grids are used which are coated by injection molding. Cut-off connection grids are preferably flat elements on which electronic components can also be placed. Electrically conductive sections or sectors in the form of singular conductive tracks exist on the cut-off terminal grids, in particular on a core element, which is centrally arranged and is surrounded by an electrically insulating coating casing. The core member is here, as a rule, made of plastic or metal, the conductive tracks being applied as conductive layers on a support substrate in the case of a plastic embodiment.

DE 10 2009 046 467 A1 discloses a cut-off lead grid having a special surface contour, as well as a control apparatus comprising such a cut-off gate. It is also described a conventional method of manufacturing a cut-off leadframe. In a summary manner, during a first manufacturing step, core elements of the cut-off connection grids are produced by a stamping or punching type cutting process. The individual core elements are here mutually interconnected in certain places, so that it is not necessary to place each individual core element, during an injection overmolding operation, which follows, in a tooling of corresponding molding. Then, the core elements are coated with a plastic material by injection molding, to form a coating envelope around the core elements, and thus, firstly to ensure a necessary electrical insulation with respect to the outside, and on the other hand obtain a mechanical stabilization.

On this occasion, during a second manufacturing step, there is a partial pre-coating of overmoulding by injection of the core elements of the cut-off leadframe, in which partial areas, such as, for example, the connection zones. , which maintain between them the individual core elements, however, are not coated by the injection molding. These partial areas can form open areas, which generally have dimensions of 1 to 2 mm.

During a third manufacturing step, the core elements are separated from each other. On this occasion, the connection zones between the core elements are eliminated by die-cutting or punching, or cut in another way. This results in a large number of individual kernel elements. The pre-encapsulation by injection molding, carried out previously, holds together these core elements and maintains them in their required geometric position.

In a final fourth stage of manufacture, a main overmoulding coating is produced by injecting the individual pre-coated core elements by injection overmolding. On this occasion, the injection-molded areas of the cut-off lead-in grid not covered by the injection-molding overmolding preform are coated, but the pre-coated zones by injection overmolding are also partially coated by overmolding by means of overmoulding. injection, so that pre-coated areas and injection molding main coating areas overlap partially, laterally. To prevent reciprocal sliding of individual sections of the core elements of the cut-off connection grids, and to guarantee the desired position of the core elements, in the injection molding tooling to produce the main coating, bearing areas necessary for the main coating of injection overmoulding, are applied to the pre-coating of injection overmolding, so that the bearing zones provide positioning in the injection overmoulding tool to produce the main coating of injection molding. This, however, leads to the fact that the main over-molding by injection is not able to completely cover the core element, but is instead interrupted at the abutment areas mentioned above, so that partial areas of the Pre-coating of injection molding is not covered and is released to the outside. It has been found that, despite the injection-molded coating envelope, fluids could reach inside a cut-off leadframe, and cause damage therein. For example, in the case of cut-off connection grids, which are implemented inside 15 gearboxes or transmissions, can oil could penetrate these grids, and was, due to absence flow of the oil, chemically decomposed over time, thus being likely to cause corrosion effects and short circuits 20 in the conductive tracks of the cut-off leadframe. Disclosure of the Invention Embodiments of the invention allow for an advantageous fabrication of a cut-off leadframe and the production of a correspondingly made cut-off leadframe for which the risk of seeing fluids is minimized. To achieve the core element of the cut-off leadframe due to seal failures of a wrapping coating obtained by injection overmolding. According to a first aspect of the present invention, there is described a method of manufacturing a cut-off leadframe. In a first step, a core element is prepared, which comprises conductive tracks. This core member is coated, by a first injection molding, with a first plastic layer, at first partial regions of the core member. Then, the core member is coated, by a second injection molding, with a second plastic layer, at second partial areas of the core member. The first and second plastics layers, i.e. the first and second partial areas, overlap reciprocally laterally in overlapping areas, and coat, in common, the entire core. The method is characterized in that the first layer of plastic material has other optical properties than the second layer of plastic material, and after the second injection molding is welded, by laser welding, the first layer of plastic material to the second layer of plastic material forming a material continuity bond. The ideas underlying the present invention can be considered as based on the following principle and the following findings: As described in the introduction, a coating envelope, which must electrically isolate a core element from a cut-off lead frame and protect against fluid penetration can be produced by a two-stage injection overmoulding operation. A first layer of plastic material, which may be designated by pre-coating of injection molding, overlaps, certainly, in this case, laterally a second layer of plastic material, which may be referred to as a main overmolding coating. by injection, but is not completely covered by it, parts of the first layer of plastic remaining left outward. It has been observed that at outwardly transition zones between the first layer of plastic material and the second layer of plastic material, residual cracks and cavities may be formed, in particular because the plastic material constituting the pre-coating of injection overmoulding is insufficiently effected by the hot plastic material, which is deposited therein during the formation of the main over-molding injection coating. In such cracks can then penetrate fluids, and spread there, especially under the effect of capillary forces. From this observation, it is now proposed, during an additional process step, to weld to one another, by laser welding, the first and the second layer of plastic material, forming a material continuity bond. In this regard, the first layer of plastic material is made of a material having other optical properties than that of the second layer of plastic material. For example, for the first and second plastics layers, it is possible to choose materials in such a way that, depending on a laser used for laser welding, the laser light is absorbed. in the material of the first plastic layer substantially stronger than in the material of the second plastic layer.

The expression "substantially higher absorbed" can be understood in this context for example as follows, namely that the laser light is absorbed in the material of the first layer of plastic so strongly that due to the absorption of light, a localized melting of the first layer of plastic material occurs at a deeper level, whereas the laser light is absorbed much less in the material of the second layer of material plastic, so that there is no localized melting in the second layer of plastic by the simple fact of light absorption. An absorption coefficient in the wavelength range of the laser light may, for example, be 50% greater for the material of the first plastic layer than for the material of the second plastic layer. .

The more or less strong absorption of the light used for the laser welding, in the material of the first respectively of the second layer of plastic material, leads to the laser light, which, in an overlap zone, falls all the time. firstly, from the outside, on the second layer of plastic material, is practically not absorbed, but is transmitted, for the most part, to the first plastic layer underneath, and is absorbed only in this one. This makes it possible to conduct, at the level of the interface surface where the first layer of plastic material is adjacent to the second layer in an overlap zone, to a localized melting of the first layer of plastic material, a slight fusion of the second layer of plastic material. layer of plastic material occurring simultaneously, so that a material continuity connection of the two layers of plastic material is formed during the solidification which follows. It is not necessary, however, that the entire second layer of plastic material on top of it be fused, as would be the case if the laser light had already been absorbed in this second layer of plastic material.

Due to the selective absorption of laser light in an area directly adjacent to an interface surface between the first and second plastic layers, made possible by the appropriate choice of materials, welding with less than one M is achieved. risk of damage. In addition, it is possible to minimize the power consumption required for laser welding. The first layer of plastics material may for example contain a coloring substance. This coloring substance can be chosen so that laser light is absorbed. The coloring substance may for example be integrated as pigments in a plastic base material. For example, it is possible to incorporate, as coloring substances, soot or dyes derived from tars. In particular, it is possible to choose properties of the coloring substance and a concentration thereof in the plastic material, so that the laser light is absorbed, for the most part, in the first layer of plastic material, on a few micrometers, thus preferably leading to localized heating of the first layer of plastic material, mainly in the vicinity of the interface surface with the second layer of plastic material. The coloring substance is preferably exclusively integrated with the first layer of plastic material, but not with the second layer of plastic material.

The second layer of plastic material may preferably be made of a material, which is substantially transparent to the laser light used for laser welding. This material may for example have, for the light in question, a transmission of more than 50%, preferably more than 90%, during the irradiation of the second layer of plastic material, that is to say up to reach the first layer of plastic. The laser light is thus mainly transmitted by the second plastic layer, and can then be absorbed by the first layer of plastic material underneath and non-transparent for this light. The two plastic layers do not need to be welded to each other along their entire surface. On the contrary, it may be sufficient to weld the first layer of plastic material to the second layer of plastic material along a line, which annularly and in a closed manner surrounds an area in which the first layer of plastic material is disengaged. Since the welded joint annularly surrounds an open area of the first layer of plastics material, it is possible to ensure that no fluid, which could penetrate at a joint or interface surface that is also exposed to the The outer surface, between the first and the second layer of plastic material, can not reach cracks formed at this interface surface up to a surface of the core element and cause damage thereto.

Advantageously, the first layer of plastic material is welded to the second layer of plastics material in an area remote from an area in which the first layer of plastic material is disengaged. The term "remote" may mean here that a welding joint must extend, albeit in a close manner, for example at a distance of less than 3 mm, preferably less than 1 mm, from the open area of the first plastic layer, but should not be generated directly along a line where the first layer of plastic material is adjacent to the second layer of plastic material at the surface. In other words, the welding joint must not be arranged directly at the transition, arriving at the surface, between the first and the second layer of plastic material, but must be spaced slightly laterally this transition. On the one hand, it makes it possible to keep the length of the welding joint short and thus to keep the stress applied for welding low, and on the other hand any residual cracks, open towards the surface, between the first and the second layer of plastic material, can be kept as small as possible, so that possibly aggressive fluids can not accumulate in these areas. The first and second plastics layers may be identical or different materials, especially thermoplastics. The first and second plastic layers may in particular have identical or similar physical properties with respect to their melting point, but not with respect to their optical absorption behavior.

In principle, the process step of the mutual welding of the two plastic layers can take place at any time after the second injection overmolding on the core member. However, it may be advantageous to weld the first plastic layer to the second plastic layer directly after the second injection molding, before the second plastic layer has cooled to the surrounding temperature. It is thus possible to further exploit, at least partially, the process heat that has been provided during the injection overmoulding, so that the following welding operation requires less energy for the heating of the material. .

According to an advantageous configuration of the process, the first and second plastic layers are welded to each other simultaneously on the two opposite sides of the core element. This makes it possible to quickly produce the desired welding seals.

According to a second aspect of the present invention, there is provided a cut-off lead grid, such as that which can be manufactured in particular using the manufacturing method described above. The cut-off lead frame comprises a core member, which includes conductive tracks, and a coating shell obtained by injection molding and encasing the core member with plastic. The coating envelope here has a first layer of plastic material at the first partial regions of the core member, which is obtained by a first injection overmolding coating the core member. In addition, the coating envelope has a second layer of plastic material at second partial regions of the core member, which is obtained by a second injection overmolding coating the core member. The first and second layers of plastic material, namely the partial areas, overlap reciprocally laterally in overlapping areas, and coat, in common, the entire core member. The cut-off lead is characterized by the fact that the first and second plastic layers have different optical properties and are welded to one another forming a material continuity connection. Laser welding of the first to second plastics layer provides a reliable and long-term seal between the two plastic layers. A welding seal, by its embodiment, preferably does not extend up to the outer surface of the coating casing formed by the two layers of plastic, but is at a interface surface between the two plastic layers, inside the coating envelope. The welding seal is therefore, as a rule, not or practically not visible from the outside. However, it can be noticed in the weld joint area, small flatness irregularities 25 of the coating envelope. The welding zone can be verified by destructive control, for example analysis of sections or polished cuts, or also by non-destructive testing, such as a computer-assisted tomography. Another possibility for quality control is a bleeding control method. Preferably, the first layer of plastics material is welded to the second layer of plastics material, in a region remote from an area in which the first layer of plastic material is disengaged. In other words, the two layers of plastic material are welded to one another in an area where the first layer of plastic material is not disengaged, but lies beneath the second layer of plastic material, which ride it here. The first layer of plastic material can, as described above, contain a coloring substance to produce the absorption of laser light. On the other hand, the second layer of plastic material may be substantially transparent for the light of a laser used for laser welding, that is to say in a wavelength range typically from 300 nm to 2000 nm. preferably 400 to 800 nm. It should be noted that any advantages and features of embodiments of the invention are here described in part with reference to a method of manufacturing a cut-off leadframe, and in part with reference to a gate of FIG. cut-off connection. For those skilled in the art, it is obvious that the features described can be combined or exchanged appropriately, to achieve other embodiments and, where appropriate, synergistic effects. BRIEF DESCRIPTION OF THE DRAWINGS In the following, embodiments of the invention will be described with reference to the accompanying drawings, neither the description nor the drawings are to be considered as limiting the invention.

Figure I shows, in a cross-sectional view, the operation of the first injection molding in the context of a manufacturing method according to the invention. FIG. 2 shows, in a cross-sectional view, the operation of the second injection overmolding in the context of a manufacturing method according to the invention. Figure 3 shows, in a cross-sectional view, the laser welding operation of the first and second plastic layers, as part of a manufacturing method according to the invention. The figures are only schematic and do not respect the scales. In the figures, the identical references designate identical characteristics or having identical effects. Embodiments of the invention In the following will be described, with reference to FIGS. 1 to 3, embodiments in accordance with the invention for the manufacture of a cut-off gate, according to which all firstly, two layers of plastics material on partial areas of a core member overlapping each other at least partially, and then bonding the two plastic layers to one another producing a continuous bonding of matter. As can be seen in FIG. 1, during a first injection overmolding operation, the core element 1 is placed in a molding tool 3 which, in bearing zones 4, bears on surfaces 12 opposite of the core element 1.

In the first partial residual zones of the surfaces 12, in which cavities 5 are formed between the molding tool 3 and the core element 1, plastic material is injected, for example polyamide mixed with substance pigments. 2. Then, as indicated by FIG. 2, during a second process step, the core element 1 10 provided with the first layer of plastics material 2 is deposited in the second layer of plastic material. This other molding tool 7 then bears against surfaces 9 of the first layer of plastics material 2, which serve as support zones 6. The moldings are then injected again into cavities formed between the molding tool 7 and the core element 1, of the plastic, which forms the second plastic layer 8. The plastics material of the second plastics material 8 must however be 20 for the laser light, and therefore does not need dye pigments or very matter material transparent layer contain little. This second layer of plastic material 8 laterally overlaps the first layer of plastic material 2, in overlapping areas 13.

In this second injection overmolding operation, the surfaces 9 with which the bearing areas of the first plastic layer 2 rest against the molding tool 7 are however not covered with material It can thus be formed, between the first layer of plastic material 2 and the second layer of plastics material 8, a crack 10 open towards the outside, along which it can move. for example, gearbox oil, from a surface 11 of the second layer of plastic material 8 to a surface 12 of the core member, in particular due to capillary forces. Transmission gear oil thus penetrating into the cut-off connection grid may lead to damage to this cut-off gate or to defects in its operation. Therefore, it is proposed to weld, by means of a laser light, the second plastic layer 8 to the first plastic layer 2, at least in parts of the overlap areas 13, in which the two layers of plastic overlap laterally. Such mutual welding leads to a material continuity connection of the two plastic layers 2, 8. At least in the region of such a material continuity connection, a crack initially present between the two layers of plastic material 2, 8, is interrupted, so that no fluid can reach from the outside to the core element 1. As shown in FIG. 3, a part of the overlapping zones 13, which is distant from a zone 14 in which the first layer of plastic material 2 is disengaged to the outside, can on this occasion be fused by localized irradiation with the aid of laser light 15. The laser light 15 is to a large extent transmitted by the second layer of plastic material 8 transparent to this light, and is then absorbed by the first layer of plastic material 2 mixed with pigments of dye. On this occasion, it is possible to provide enough energy to produce the at least localized melting, both of the second layer of plastic material 8 released outwardly in these overlapping areas 13, as of the first layer of material plastic 2 adjacent below. During the solidification which follows, a welded joint 16 is formed inside, and thus the material continuity connection, desired, between the two layers of plastic material 2, 8. The cut-off gate provided with both plastic layers 2, 8 can here be irradiated simultaneously from the two opposite sides with laser light 15, which allows to obtain short process times. Alternatively, the welding seals can also be made successively on the two opposite sides.

Claims (12)

REVENDICATIONS1. A method of manufacturing a cut-off lead frame, comprising: preparing a core member (1) having conductive tracks; a first injection molding encasing the core member (1) with a first plastic layer (2) at first partial areas of the core member (1); A second injection molding encasing the core member (1) with a second plastic layer (8) at second partial areas of the core member (1); the first and second plastic layers (2, 8) reciprocally overlapping each other in overlapping areas (13), and co-sealing the entire core member (1); characterized in that the first plastic layer 20 has other optical properties than the second plastic layer, and after the second injection molding is welded by laser welding the first plastic layer (2). to the second plastic layer (8) forming a material continuity bond. 2. Method according to claim 1, characterized in that for the first and second plastic layer (2, 8) materials are selected respectively, and for the laser welding a laser is selected so that the light (15) of the laser is absorbed in the material of the first plastic layer (2) substantially stronger than in the material of the second layer of plastic material (8). 3. Method according to claim 1 or claim 2, characterized in that the first layer of plastic material (2) contains a coloring substance. 4. Method according to one of claims 1 to 3, characterized in that the second layer of plastic material (8) is substantially transparent to the laser light (15) used for laser welding. 5. Method according to one of claims 1 to 4, characterized in that the first layer of plastic material (2) is welded to the second layer of plastic material (8) directly after the second injection overmolding, before that the second plastic layer (8) has cooled to the surrounding temperature. 20 6. Method according to one of claims 1 to 5, characterized in that the first layer of plastic material (2) is welded to the second layer of plastic material (8) simultaneously on the two opposite sides of the element. of core (1). 25 7. Method according to one of claims 1 to 6, characterized in that the first layer of plastic material (2) is welded to the second layer of plastic material (8), in a zone distant from a zone ( 14) in which the first layer of plastic material (2) is disengaged. 8. Method according to one of claims 1 to 7, characterized in that the first layer of plastic material (2) is welded to the second layer of plastic material (8) along a line which surrounds annularly and in a closed manner, a zone (14) in which the first layer of plastic material is disengaged. A cutoff gate comprising: a core member (1) having conductive tracks; a first plastic layer (2) at first partial regions of the core member (1), which is obtained by a first injection overmolding embedding the core member (1); a second layer of plastic material (8) at second partial regions of the core member (1), which is obtained by a second injection overmolding encapsulating the core member (1); the first and second plastic layers (2, 8) laterally overlapping each other in overlapping areas, and co-sealing the entire core member (1); characterized in that the first plastic layer has other optical properties than the second plastic layer, and the first plastic layer (2) is welded to the second plastic layer (8) forming a connection continuity of matter. Cut-away grating according to Claim 9, characterized in that the first layer of plastics material (2) is welded to the second layer of plastics material (8) in a zone remote from an area (14) in which the first plastic layer (2) is disengaged. 11. cut-off connection grid according to claim 9 or claim 10, characterized in that the first layer of plastic material (2) contains a coloring substance. 12. cut-off gate according to one of claims 9 to 11, characterized in that the second plastic layer (8) is substantially transparent for light in a wavelength range of 300 to 2000 nm.