Method for overmolding with plastic and assembly

Abstract

A method for overmolding an element (4) with a body (2) made of plastic, wherein the element (4) is placed in an injection mold (5) having a cavity (8), wherein the element (4) is fixed in the cavity (8) by means of a movable retaining pin (9), wherein the plastic is injected into the cavity (8), and wherein the retaining pin (9) is moved away from the element (4) after the cavity (8) has been filled and while the plastic is still plastic, such that plastic can flow into the volume (11) released by the retaining pin (9), characterized in that the retaining pin (9) is subsequently moved back towards the element (4) as long as the plastic that has flowed into the volume (11) is still plastic, in particular such that a kind of compaction of the plastic takes place in the area of ​​fixation to the body (2).

Description

[0001] The invention relates to a method for overmolding an element with a body made of plastic according to the preamble of claim 1.

[0002] The method according to the invention can be used in particular for the production of a so-called electrical component carrier. An electrical component carrier is a support element for receiving electrical and / or electronic components, wherein electrical conductors for the electrical connection of the components are arranged in and / or on the support element. The electrical component carrier is usually produced by overmolding the structure for the conductors with plastic in an injection molding machine.

[0003] In a process for overmolding an element with a plastic body, the element is placed in a cavity-bearing injection mold located in the injection molding machine and fixed in the cavity by means of a movable retaining pin. The plastic is then injected into the cavity. After the cavity is filled, the retaining pin is moved away from the element while the plastic is still malleable, allowing plastic to flow into the volume released by the retaining pin and fill the area where the element was fixed. Generally, this creates a weld line on the body in the area where the element was fixed.

[0004] It has been found that leaky sutures frequently occur on the body, allowing harmful substances to enter and potentially affect the body's internal elements. One such suture (12) is located in Fig. Figure 10 clearly shows the leak 15 at body 2 in the area of ​​the weld seam 12. To counteract such impairments to the embedded element 4, the body is subsequently encased in a plastic resin to achieve a corresponding seal at the weld seams. However, this encasement is an additional, costly work step.

[0005] Various methods for overmolding an element, aspects of such methods, and components manufactured using such methods are known in the prior art and in particular from the documents DE 199 26 250 A1, DE 103 26 794 A1, DE 196 20 002 A1, US 6 290 893 B1, JP 2003-170 467 A and DE 10 2015 209 789 A1.

[0006] The invention is based on the objective of further developing the overmolding process in such a way that the tightness in the area of ​​element fixation and / or at the weld seam is improved. In particular, the additional potting process, which is currently common practice, should be eliminated.

[0007] This problem is solved in a generic overmolding process by the characterizing features of claim 1.

[0008] In the method according to the invention, the retaining pin is subsequently moved back towards the element as long as the plastic that has flowed into the volume is still plastic. In particular, this retraction of the retaining pin is carried out in such a way that a kind of compaction of the plastic occurs in the area of ​​fixation to the body. Further embodiments of the invention are the subject of the dependent claims.

[0009] As the plastic flows into the volume released by the retaining pin, a type of weld line can form in the area of ​​fixation to the body. According to the inventive overmolding method, when the retaining pin is moved back towards the element, the plastic in the area of ​​the weld line can be compacted. In particular, this can close any leaks at the weld line to the element.

[0010] In a further refinement of the method, the path length for the return movement of the retaining pin towards the element can be chosen to be shorter than the path length for the return movement of the retaining pin away from the element. In particular, it is advantageous for the return movement of the retaining pin to be terminated before and / or upon reaching the area of ​​fixation to the body. Such a measure ensures reliable closure of the bandage and thus its tightness.

[0011] The element can be a metal part. It can be flat, for example, a metal sheet. Preferably, the element can form a conductor track for the electrical connection of components located on the body. In particular, these conductor tracks can be manufactured as a stamped metal grid, which is then overmolded with plastic to form an electrical component carrier. The plastic can be a thermoplastic.

[0012] Advantageously, the retaining pin can have a point for fixing the element. The element can be provided with a receptacle corresponding to the point. Furthermore, the receptacle can be positioned in and / or on the area of ​​fixation to the body. The point can engage in the receptacle in a simple manner, either positively or non-positively, to fix the element.

[0013] In a further embodiment, the retaining pin can be movably guided within the injection mold, thus enabling precise fixation of the element in the cavity. The guide can be designed such that the retaining pin can move into and / or out of the cavity. Advantageously, the retaining pin can be moved by means of a drive, for which a corresponding control system can be provided. The drive can be a cost-effective and reliable motor, electric motor, electromagnetic, pneumatic, hydraulic, or similar type of drive.

[0014] The invention further provides an assembly comprising a plastic body and at least one element embedded in the body by overmolding. The element is fixed to the plastic during overmolding by means of a movable retaining pin. The plastic that flows into the fixation area on the body during and / or after the retaining pin is moved away is compacted. This achieves a simple seal of the assembly in the fixation area on the body without requiring any additional measures. According to the invention, the plastic that flows into the fixation area on the body is compacted by moving the retaining pin back. Such an assembly can be used, in particular, as a carrier for electronic components.

[0015] The following can be stated regarding a particularly preferred embodiment of the invention.

[0016] During the production of an electronic component carrier, the conductor tracks must be held in the center of the injection mold cavity during the injection process. Retaining pins are incorporated into the injection mold for this purpose. The subsequent removal of these pins and the flow of the plastic create weld lines, which can be potential sources of leakage for the electronic component carrier. Therefore, these weld lines must be sealed according to the relevant quality requirements, such as IP67. To avoid an additional sealing step, the conductor tracks should be embedded in a media-tight manner during overmolding with plastic.

[0017] This is achieved by mechanically extending the injection mold. During the injection process, the chamber in the area of ​​the fixation is filled with plastic by pulling the retaining pins. Immediately afterwards, the retaining pins are pushed back slightly, compacting the flowing plastic. The resulting weld line, where leaks to the conductor track could potentially occur, is thereby closed and / or compacted.

[0018] Thus, a method for sealing weld seams in a media-tight manner during the injection molding process for an electrical component carrier has been created.

[0019] The advantages achieved with the invention consist in particular of the fact that assemblies in which conductor tracks are overmolded can be manufactured without the previously required additional step of potting the weld lines. This saves costs in the manufacture of the assembly. Furthermore, the assembly's sealing against the ingress of contaminants is improved, resulting in an increase in quality.

[0020] An embodiment of the invention with various further developments and configurations is shown in the drawings and is described in more detail below. The drawings show... Fig. 1. Schematic representation of a component assembly in perspective view, Fig. 2 an element of the assembly made of Fig. 1 as a single unit, Fig. 3 a retaining pin to fix the element Fig. 2 in one injection mold, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 to Fig. 9 the injection mold during individual work steps when overmolding the element Fig. 2 and Fig. 10 an excerpt from the assembly according to Fig. 1 according to the state of the art.

[0021] In Fig. Figure 1 shows an assembly 1 in the form of an electrical component carrier with a body 2 made of plastic, the body 2 serving as a carrier for receiving electrical and / or electronic components 3. Embedded in the body 2 are elements 4, not visible (shown with dashed lines), designed as conductive traces, which serve for the electrical connection of the components 3. One such element 4 is shown as a separate part in Fig. 2 is shown as an example. The assembly 1 is manufactured by overmolding the element 4 with the body 2 made of plastic using an injection mold 5 (see Fig. 4) in an injection molding machine, as in Fig. 4 to Fig. 9 is shown in more detail.

[0022] As in Fig. As shown in Figure 4, the element 4 is first inserted into the open injection mold 5, which consists of an upper part 6 and a lower part 7 and has a cavity 8. The element 4 is fixed in the cavity 8 by means of a movable retaining pin 9. In this case, the element 4 is fixed by means of several retaining pins 9. Of course, instead of a pin-shaped retaining pin 9, a retaining element with another suitable shape can also be used to fix the element 4. The injection mold 5 is then closed and the plastic is injected into the cavity 8 at the gate 10, as shown in Figure 4. Fig. 5 is shown. After filling the cavity 8 and while the plastic is still malleable, the retaining pin 9 is moved away from element 4 to a position P1, as shown in Fig. 6 can be seen, so that in the area of ​​fixation the retaining pin 9 releases a certain volume 11. This then allows according to Fig. 7 Plastic flows into the volume 11 released by the retaining pin 9, forming a type of weld line 12 (see Fig. 9) in the area of ​​fixation to body 2. Subsequently, the retaining pin 9 is moved back towards element 4 to position P2 as long as the plastic that has flowed into volume 11 is still plastic, as can be seen in Fig. 8. This retraction of the retaining pin 9 towards the element 4 causes a kind of compaction of the plastic in the area of ​​fixation to the body 2 and especially in the area of ​​the weld seam 12. This creates a tight, closed weld seam 12, as can be seen from Fig. 9 can be seen, which closes any leaks at the weld seam 12 to element 4. After the plastic has solidified, the retaining pins 9 are then moved away from element 4, so that the retaining pins 9 are located in the lower part 7 of the injection mold 5. Finally, according to Fig. 9 opened the injection mold 5 and removed the body 2 with the injected element 4.

[0023] How to compare position P1 in Fig. 7 with position P2 in Fig. 8 detects that the path length for the return movement of the retaining pin 9 towards element 4 is chosen to be shorter than the path length for the return movement of the retaining pin 9 away from element 4. This ensures that the return movement of the retaining pin 9 ends before or upon reaching the area of ​​fixation on body 2. Thus, optimal compression of the bandage 12 is ensured without the risk of damaging it during the return movement.

[0024] Insofar as element 4 serves as an electrical conductor, it is advantageous for element 4 to be a metal part. Element 4 is, according to Fig. 2. Flat design. To easily overmold multiple conductor tracks, it is advantageous for element 4 to be designed as a stamped grid, produced from a sheet of metal in a stamping process. The plastic used for overmolding element 4 is a thermoplastic.

[0025] As in Fig. As can be seen in Figure 3, the retaining pin 9 has a tip 13 for fixing the element 4. The element 4 is according to Fig. 2 is in turn provided with a receptacle 14 corresponding to the tip 13. The receptacle 14 is located in and / or on the area of ​​fixation to the body 2. The tip 13 then engages in the receptacle 14 to fix the element 4 in a form-fit and / or force-fit manner, as can be seen from Fig. 4 recognizes. In order to perform the corresponding movements, the retaining pin 9 is movably guided in the lower part 7 of the injection mold 5. The retaining pin 9 is moved by means of a drive (not shown) operated by a control system, which can be, for example, motor-driven, electromechanical, electromagnetic, pneumatic, hydraulic, or the like. This allows the retaining pin 9 to move into and / or out of the cavity 8 as required.

[0026] Using the described method, it is therefore possible to determine the in Fig.The assembly 1 shown, designed in the manner of an electrical component carrier, comprises a body 2 made of plastic and at least one element 4 embedded in the body 2 by overmolding, wherein the element 4 is fixed with the plastic during overmolding by means of a movable retaining pin 9, and is manufactured in a sealed construction. For this purpose, the plastic that flows into the area of ​​fixation on the body 2 during and / or after the removal of the retaining pin 9 is compacted, for which purpose the plastic that flows into the area of ​​fixation on the body 2 is advantageously compacted by moving the retaining pin 9 back.

[0027] The invention is not limited to the described and illustrated embodiment. Rather, it also encompasses all technically advanced developments within the scope of the invention defined by the claims. Thus, the method according to the invention can not only be used to manufacture an electrical component carrier, but can also be advantageously employed for the media-tight overmolding of other elements. Reference symbol list 1 assembly 2 bodies 3 (electrical / electronic) component 4 Element 5 Injection mold 6 Top part (from injection mold) 7 Lower part (of injection mold) 8 Cavity 9 retaining pin 10. Sprue point 11 (released) volume 12. Binding suture 13 Tip (on retaining pin) 14 Recording (in element) 15 Leakage (with state of the art)

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