Patent Application
20190126525
This application claims the benefit and priority of German Patent Application DE 10 2017 219 325.5, filed Oct. 27, 2017, which is incorporated by reference herein in its entirety.
The present invention relates to an injection molding tool and a method for the sealing of insert components.
To protect components, these are often equipped with a lid and are overmolded with a mass, which protects the components from a penetration of external influences. This is e.g. carried out by means of an injection molding tool. To accomplish this, an insert component, which is usually a metal sheet, is inserted into the space that is provided for the injection molding tool. Then it is overmolded with a flowable plastic compound. The contact surfaces on the injection molding tool are hereby used for the sealing of the insert component. A disadvantage of the sealings that are known thus far is, that they either do not completely seal or, when they provide a better sealing, that they are not able to withstand the high temperatures during the injection molding process. Furthermore, larger excess molding often occurs during the injection molding procedure, resulting in undesired burr formations.
It is thus one objective of this invention to provide an injection molding tool and a method for the sealing of insert components, by means of which the mentioned disadvantages are overcome.
In accordance with the invention, this objective is achieved by means of the characteristics of the independent patent claims. Advantageous embodiments are subject-matter of the dependent claims.
An injection molding tool is provided, comprising a base carrier that is suitable to accommodate an insert component, wherein at least one separate part of the base carrier forms a contact surface with the insert component after it has been inserted into the base carrier, herein at least the contact surface features a high-temperature material.
By replacing the previously known contact surface with a high-temperature material, a significantly lower contact pressure can be used than it was used for methods that are known thus far. An improved sealing of the insert component can thus be achieved by means of an injection molding with the flowable mass, e.g. with thermoset plastic. Also, a compensating of uneven surfaces on the insert components can be accomplished due to the temperature characteristics of the high-temperature materials.
In one embodiment, at least the separate part of the base carrier is surrounded by the high-temperature material.
In one embodiment, the base carrier consists of at least two components that can be connected to each other, one of which is the separate part, and wherein the separate part is made of the high-temperature material.
By surrounding the contact surface with a high-temperature material or by providing a second part as an attachable cover so to speak, an already existing injection molding tool can be retrofitted. By means of the two-part production of the contact area of the injection molding tool, its production is simpler.
In one embodiment, the high-temperature material features a predetermined thickness. The thickness is selected in such a way, that the desired characteristics, i.e. a sealing at the lowest possible contact pressure, can be realized.
A method for the sealing of insert components is furthermore provided, wherein at least one insert component is hereby inserted into the described base carrier of the injection molding tool, and a pressure is exerted onto it in a further step, and in another step, it is overmolded with a flowable mass. The maximum contact pressure between the injection molding tool and the insert component is hereby selected in such a way, that at least one sealing section of the insert component is protected against penetration of the flowable mass during the injection molding procedure.
In one embodiment, the base carrier can be moved hydraulically. The contact pressure is thereby adjustable for the sealing.
In one embodiment, the high-temperature material is PEEK. In one embodiment, the flowable mass is a thermoset. In one embodiment, a circuit board equipped with electronic and/or electrical components is arranged within the at least one insert component.
When using the high-temperature material, in particular PEEK, it is advantageous that a significantly lower contact pressure can be used than in methods that are known thus far. An improved sealing of the insert component can thus be achieved by means of the overmolding with e.g. the thermoset, as well as a compensating of uneven surfaces on the insert component due to the temperature characteristics.
Further characteristics and advantages of the invention can be derived from the following description of embodiments of the invention, from the figures of the drawings that depict details according to the invention, and from the claims. The individual characteristics can be implemented individually by themselves or as a plurality in any combination in any variant of the invention.
Preferred embodiments of the invention are described in detail in the following by means of the attached drawings.
In the following description of the figures, identical elements or functions are provided with the same reference signs.
A thermosetting plastic is often used as flowable mass for the injection molding of insert components, because it turns very low viscous during the injection molding process and can therefore be used very well for filling thin-walled areas. However, it also flows very easily into areas that should not be overmolded, i.e. where no thermosetting plastic should be found after the injection molding process. Such areas are e.g. electrical or electronic components, over which the thermosetting plastic flows during the overmolding process, since these are not completely sealed from the contact surface. This can happen since uneven surfaces can appear in the insert component due to manufacturing tolerances, which cannot be fully sealed by the metallic contact area that was used thus far. The inflow into undesired areas calls for an extensive reworking. This is a problem especially when electrical or electronic components are overmolded, since these should be stressed as little as possible mechanically, in order to prevent damage or destruction.
To achieve a better sealing, a high contact pressure is used between the base carrier of the injection molding tool, into which the insert component is arranged, and the insert component. On the other hand, this is a disadvantage for especially electrical or electronic components, since these are sensitive to pressure. The force that is referred to as contact pressure or pre-tensioning is the force that is exerted onto the insert components during the injection molding process e.g. with thermosetting plastic, in order to be sealed in such a way that an overmolding of undesired areas with thermosetting plastic is prevented. Particularly the base carrier can be arranged to be hydraulically movable.
So far, the sealing of pressure-sensitive components, in particular circuit boards with electrical or electronic components mounted on it, is not solved optimally. As a solution, it is thus suggested to replace the contact surfaces of the base carrier of the injection molding tool, which serve for the sealing of the insert components, with a technical high-temperature material. The use of PEEK, or polyetheretherketone is advantageous in this case. Although this plastic material is as hard as steel, it can absorb small uneven surfaces in a temperature range of a thermoset tool of approx. 160° C. As a result, when compared to conventional methods, a reduced contact pressure can be used without impairing the sealing effect. The sealing effect is even enhanced by the use of a technical high-temperature material such as PEEK, although the contact pressure is reduced. This is a result particularly of the thermal characteristics of the material.
As it is schematically indicated in the
The separate area 12 may thus be formed in one embodiment as a separate component which is placed on the remaining part 11 of base carrier 1, e.g. in form or a lid. In another variant it is possible that the upper, separate part 12 of basic carrier 1 can be surrounded with the technical high-temperature material, e.g. coated or overmolded. In any case, it is necessary that the separate part 12 of basic carrier 1 that is made of the technical high-temperature material features a thickness, by means of which the advantageous characteristics of the separate part 12 can be used, i.e. in particular the exerting of a lower pressure p on the insert component 2 while achieving an increased sealing effect at the same time. The technical high-temperature material is furthermore to be selected in such a way, that it is thermally stable in the temperature range which is used for the injection molding, but that it can still flow to a certain degree. At lower temperatures it should be hard. A very suitable material is PPEK, or polyetheretherketone.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102017219325.5 | Oct 2017 | DE | national |
