Electronic component for automation technology and a manufacturing process

Abstract

The invention relates to an electronic component for automation technology with at least one standard industrial connector, in particular for sensors and / or actuators, comprising a plastic body as a housing produced by overmolding an electronic circuit board. A ceramic heat sink is arranged on the electronic circuit board, which at least partially protrudes from the plastic body or forms an outer surface of the housing. The invention further relates to a manufacturing method for the electronic component.

Description

[0001] The invention relates to an electronic component for automation technology according to the preamble of claim 1, and to a method for manufacturing the electronic component.

[0002] In automation technology, particularly in industrial manufacturing or process measurement technology, electronic components or devices such as sensors, actuators, and bus connectors (gateways) are frequently used to automate product manufacturing. The applicant manufactures and distributes a large number of such products. Electronic components can be arranged inside a housing of the electronic component, preferably a circuit board. Preferably, industrial connectors, especially rigid connectors (M8, M12), can be soldered onto the circuit board.

[0003] Such an electronic component is known from DE 10 2017 203 870 A1, which comprises a circuit board with multiple connectors and multiple light-emitting diodes, encapsulated twice in plastic. The circuit board is embedded in a first transparent injection-molded plastic part produced in a first injection molding process, and the transparent first injection-molded plastic part is enclosed by a non-transparent second injection-molded plastic part produced in a second injection molding process. The injection-molded plastic parts have the particular advantage of forming a durable and environmentally sealed housing for the circuit board while simultaneously enabling the functionality of a light guide.

[0004] Using a plastic housing produced by overmolding offers a cost-effective and robust solution for protecting an electronic circuit board from environmental influences. In particular, this can improve the lifespan of an electronic component. However, with increasing performance of electronic components, especially high-performance processors, the plastic housing can lead to increased heat generation within the electronic components.

[0005] German patent DE 10 2007 014 433 A1 discloses a substrate for electrical or electronic components or circuits made of a ceramic material that is electrically non-conductive or virtually non-conductive. The substrate itself serves for heat dissipation and can additionally incorporate or be connected to ceramic cooling elements. However, a substrate made of ceramic material has the disadvantage of high cost and significant limitations on the arrangement of electronic components. In particular, a multi-layered structure with different functions for guiding conductor tracks is not possible, and the arrangement of electronic components on both sides is also considerably restricted.

[0006] DE 10 2022 116 608 A1 discloses a connector module for printed circuit board connection, comprising a multi-pole, round port for connecting a connector, an electronic unit and a shell-shaped housing.

[0007] DE 198 55 389 A1 discloses an electronic device with a two-part housing for receiving a carrier substrate with electronic circuitry.

[0008] DE 41 07 312 A1 discloses a mounting arrangement of a semiconductor device on a printed circuit board, wherein the metallic contact surface of the semiconductor device is connected to the printed circuit board via a thermally conductive layer. The printed circuit board is arranged on a metallic substrate by means of an electrically insulating intermediate layer, wherein a via is provided in the printed circuit board in the area of ​​the contact surface of the semiconductor device, through which a thermally conductive connection is established between the thermally conductive layer and the electrically insulating intermediate layer.

[0009] The object of the invention is to provide an electronic component that, while avoiding the disadvantages known from the prior art, enables the long-term use of electronic components with increased performance. Furthermore, the object is to provide a method for manufacturing the electronic component.

[0010] The problem is solved by the features of claim 1. With regard to the method, the problem is solved by the features of claim 10.

[0011] Advantageous embodiments of the invention are specified in the dependent claims.

[0012] According to the invention, an electronic component for automation technology is claimed, comprising at least one standard industrial connector, preferably several standard industrial connectors for sensors and / or actuators, and a plastic body as a housing produced by overmolding an electronic circuit board. Preferably, a ceramic heat sink is arranged on the back side of the electronic circuit board, which projects at least partially from the plastic body or forms an outer surface of the housing. Preferably, electronic components are arranged on the front side of the electronic circuit board, and the electronic circuit board has at least one conductor connecting the electronic components to the ceramic heat sink for heat dissipation. Preferably, the at least one conductor enables heat to be transferred from the electronic components on the front side to the ceramic heat sink on the back side of the electronic circuit board.

[0013] The electronic circuit board is preferably made of a conventional printed circuit board material with good insulating properties to increase its efficiency and reliability. Particularly preferred is a glass fiber epoxy resin laminate or a glass fiber epoxy resin composite material, which exhibits good electrical insulation properties and is especially cost-effective. Furthermore, such circuit board materials are optimized for the production process and can implement a wide variety of functionalities. In particular, compared to circuit boards made of ceramic material, standard processes for assembly and manufacturing can be applied. Furthermore, it is possible to place electronic components on both the front and back sides of the circuit board.Advantageously, conductive traces can connect the electronic components on the front and preferably also those on the back to the ceramic heat sink on the back. This approach, in particular, overcomes the disadvantage of limited thermal conductivity.

[0014] Preferably, the electronic circuit board itself is not made of a ceramic material.

[0015] The housing, designed as a plastic body, preferably serves as a protective and support element for the electronic circuit board with electronic components, the circuit board preferably being overmolded in a plastic injection molding process. Particularly preferably, several standard industrial connectors are used, protruding from and enclosed by the plastic body.

[0016] The term electronic circuit board here refers preferably to a printed circuit board on which electronic components are mounted and functionally connected via industrial connectors, in particular rigid connectors (M8, M12).

[0017] The invention offers the advantage that the integration of a ceramic heat sink with protruding cooling fins enables efficient heat dissipation from the electronic circuit board, thereby increasing the reliability and lifespan of the electronic component and preventing overheating. In particular, more powerful electronic components, especially processors and / or microcontrollers, can be used. Furthermore, the use of a plastic housing allows the electronic component to be robust and resistant to environmental influences, thus expanding its application possibilities in harsh industrial environments. The at least partial protrusion of the ceramic heat sink or the formation of a housing surface provides the advantage of passive cooling, eliminating the need for active cooling components such as fans, which reduces energy consumption and offers protection against environmental influences.The use of a ceramic material offers the advantage of high thermal conductivity combined with electrical insulation, which improves heat dissipation without increasing the risk of short circuits. The conductive traces connecting the front and back of the electronic circuit board allow for the use of a conventional circuit board material, whose limited thermal conductivity is overcome by these traces.

[0018] Preferably, the electronic components are connected together with a conductor track for power supply, in particular as a so-called daisy chain, wherein the conductor track is connected to the ceramic heat sink in order to distribute local heat points or hotspots over a larger area.

[0019] Preferably, the ceramic heat sink is thermally connected to the heat-generating electronic components on the circuit board. In particular, these electronic components may be processors, microcontrollers, power stages, and / or output switches.

[0020] According to a preferred embodiment, the ceramic heat sink has several cooling fins that protrude at least partially or completely from the plastic body. The protruding cooling fins of the ceramic heat sink improve passive cooling. Particularly preferably, the ceramic heat sink has a base body with several cooling fins arranged on it, wherein the base body is surrounded by the plastic body and the multiple cooling fins protrude beyond an outer surface of the plastic body. In other words, the base body is preferably congruent with an outer surface of the plastic body. This has the advantage that the ceramic heat sink can be positioned more easily in an injection mold and overmolding of the ceramic heat sink can be avoided.

[0021] Preferably, at least one or more conductor tracks, particularly made of copper, are designed for current conduction, wherein the ceramic heat sink is mounted directly or immediately onto the circuit board or preferably forms a contact surface, in particular a solder surface or solder joint, with a surface of the circuit board, and wherein the ceramic heat sink is connected to the at least one current-carrying conductor track for heat dissipation. Connecting the ceramic heat sink to the conductor track has the advantage that the circuit board itself does not need to provide heat dissipation. In contrast, a circuit board intended to provide heat dissipation would need a correspondingly large surface area for full-surface contact with all components.In contrast, heat dissipation via a conductor track allows for a particularly space-saving design, whereby the arrangement of electronic components on the front and back sides can be chosen arbitrarily, as long as contact with the conductor tracks is maintained and current can be supplied simultaneously. Preferably, heat dissipation can be ensured in this way for all components contacted on the circuit board. For example, a layered structure is also conceivable here, whereby direct contact with the surface of the electronic circuit board is not necessary.

[0022] According to a further preferred embodiment, additional electronic components or at least one electronic component are arranged on the back of the electronic circuit board, wherein at least some electronic components are arranged in a space between the ceramic heat sink and the back of the electronic circuit board.

[0023] Preferably, electronic components are arranged adjacent to a contact or solder surface for connecting the ceramic heat sink. In other words, the ceramic heat sink is not fully bonded to the circuit board, but allows for lateral arrangement of electronic components. This has the advantage that as many electronic components as possible can be arranged on the circuit board in a space-saving manner, while the ceramic heat sink, due to its electrical insulating properties, allows for direct contact with the electronic components without the risk of breakdown or short circuit. In comparison, metal heat sinks have the disadvantage that sufficient air / creep distance and a thermal paste with reduced thermal conductivity must be provided.

[0024] Preferably, the ceramic heat sink can have a recess on its underside facing the electronic circuit board in order to accommodate protruding electronic components in the space between.

[0025] Furthermore, it is conceivable that electronic components are soldered laterally to the ceramic heat sink and connected to the circuit board via a conductor track. This allows the ceramic heat sink itself to be advantageously used as an extension of an arrangement of electronic components.

[0026] Preferably, the electronic circuit board is made of an insulating material, in particular plastic material or a plastic composite material, in particular an electrically insulating material that has a lower thermal conductivity compared to the ceramic heat sink, and wherein the at least one conductor track ensures the heat dissipation from the electronic components to the ceramic heat sink.

[0027] Furthermore, the electronic circuit board is preferably designed for the mechanical fixing of electronic components and the standard industrial connections, which ensure such a firm mechanical connection that they can withstand a high-pressure injection molding process.

[0028] According to a preferred embodiment, the electronic component is an IO-Link master unit. Designing it as an IO-Link master unit enables simple and standardized communication with a variety of fieldbus devices, particularly sensors and / or actuators, thus simplifying integration into existing automation systems. By implementing IO-Link technology, the electronic component can acquire and forward diagnostic data from connected devices, and the ceramic heat sink advantageously allows for the processing of larger data volumes.

[0029] The ceramic heat sink is preferably made of aluminum oxide. Aluminum oxide is advantageously chemically stable and corrosion-resistant, which makes the ceramic heat sink particularly suitable for use in chemically aggressive or humid environments. The ceramic material has high thermal conductivity and the advantage of low electrical conductivity, which enables improved heat dissipation and electromagnetic compatibility. The ceramic heat sink can also preferably be made of silicon carbide or aluminum nitride.

[0030] According to a preferred embodiment, the ceramic heat sink has a discontinuous metal coating to connect it to several conductive traces on the electronic circuit board. The discontinuous metal coating on the ceramic heat sink enables a targeted and reliable connection to the conductive traces on the circuit board, thus simplifying assembly. In particular, the metal coating is discontinuous in such a way that no electrical short circuit occurs between the conductive traces, allowing the insulating properties of the ceramic to be utilized. By using a metal coating for fixation, the heat sink can be mounted without additional mechanical fasteners, reducing the overall height of the electronic component and lowering material costs. Specifically, the heat sink is mounted before the circuit board is overmolded with the plastic housing.Preferably, the fixing is mechanically stable enough to prevent loosening, particularly during a high-pressure injection molding process. The selective metal coating enables a precise connection to heat conduction paths and thermal connections to heat-generating electrical components on the electronic circuit board, resulting in optimized heat distribution.

[0031] Preferably, these are copper conductor tracks. Alternatively or additionally, thermal conductor tracks can be formed on the electronic circuit board, which are solely intended for heat conduction.

[0032] In other words, the conductor tracks are preferably connected to or arranged on the heat-generating electronic components in order to transfer the heat to the ceramic heat sink.

[0033] According to further training, the standard industrial connectors can be connected to the front of the circuit board, and the ceramic heat sink to the back. This spatial separation of the industrial connectors and the ceramic heat sink allows for efficient use of the available space on the circuit board, resulting in a compact design for the electronic component. In particular, electronic components can be arranged on both the front and back of the circuit board. Furthermore, a larger number of electronic components on the circuit board can be brought into contact with the ceramic heat sink to dissipate their heat.Furthermore, by arranging the industrial connectors on the front and the ceramic heat sink on the back, improved thermal separation between the heat sources and the connectors can be achieved, thus facilitating or at least not restricting the operation of the electronic component. Additionally, heat dissipation via air intake or the connection of further heat sinks can be facilitated on the back without impairing the functionality of the electronic component for the operator.

[0034] Further improvements may include the inclusion of a via on the circuit board, connected to the ceramic heat sink and / or conductive traces, to dissipate heat from the front of the circuit board and the electronic components mounted on it. The vias, in particular, allow for direct heat transfer from the electronic components on the top side of the circuit board to the ceramic heat sink, resulting in more effective cooling and reducing the thermal stress on the components.

[0035] According to a further development, it may be preferable for the ceramic heat sink to have a shoulder section that is overmolded by the plastic body in order to attach the ceramic heat sink to the circuit board. In particular, the shoulder section is formed perpendicular to a normal direction of the circuit board, with the plastic body engaging the ceramic heat sink in a form-fitting manner and thus securing it against forces acting along the normal direction. The shoulder section also has the advantage that the contact surface between the ceramic heat sink and the plastic body can be enlarged and the sealing effect improved.

[0036] Preferably, the plastic body is overmolded using a high-pressure injection molding process. Particularly preferably, the electronic components, connectors, and ceramic heat sink are connected to the circuit board in such a way that they can withstand mechanical stress resulting from the injection molding process.

[0037] Furthermore, it is preferably provided that the plastic body is produced by double overmolding the electronic circuit board, wherein a first plastic section attaches the ceramic heat sink to the electronic circuit board and a second plastic section forms an outer surface adjacent to the ceramic heat sink. Preferably, the aforementioned shoulder section can be designed such that the second plastic section secures the ceramic heat sink in the housing. The use of double overmolding has the advantage that the plastic material for the first overmolding can be selected to be particularly gentle, while the second overmolding can be designed with an improved surface finish or with additional functionalities such as sealing, optical transparency, or improved gap dimensions.

[0038] The invention further relates to a method for manufacturing the aforementioned electronic component, wherein the ceramic heat sink is arranged on the electronic circuit board and subsequently overmolded with the plastic body by means of a plastic injection molding process. This has the advantage that the ceramic heat sink can be attached particularly easily by means of overmolding and also ensures efficient heat dissipation.

[0039] The ceramic heat sink is preferably manufactured using a pressing process. Advantageously, this method allows for the cost-effective production of heat sinks in large quantities and with complex geometries. In particular, the aforementioned shoulder section and / or the cooling fins can advantageously be manufactured using a pressing process in a press tool.

[0040] The invention will now be explained in more detail using exemplary embodiments and with reference to the drawings.

[0041] They show schematically: Fig. 1a: Perspective view of the back of an electronic component with a ceramic heat sink, Fig. 1b: Front view of the electronic component according to the Fig. 1a, Fig. 1c: Sectional view of the electronic component along a section axis AA according to the Fig. 1b with an electronic circuit board, Fig. 2: Detailed view of the electronic component according to the Fig. 1c, Fig. 3a,b: Top view and side view of an electronic circuit board according to the Fig. 1c without case, Fig. 4a-e: perspective view, side views, bottom view and top view of a ceramic heat sink, Fig. 5: Side view of the electronic circuit board with ceramic heat sink.

[0042] In the following description of preferred embodiments, identical reference numerals denote identical or comparable components.

[0043] The Fig. 1a, Fig. 1b and Fig. Figure 1c shows an electronic component 10, in particular an IO-Link master unit, with an integrated electronic circuit board 12 according to the Fig. 1c, which is enclosed by a plastic body 14 that forms a housing for the electronic component 10 and is preferably manufactured by injection molding. For heat dissipation, the electronic circuit board 12 is connected to a ceramic heat sink 20, which preferably has several cooling fins 22 that protrude from the plastic body 14. Preferably, the ceramic heat sink 20 is arranged on a rear side 24 of the electronic circuit board 12, with several standard industrial connectors 28, in particular plug connectors, for connecting sensors and / or actuators (not shown) preferably being provided on an opposite front side 26. More preferably, the cooling fins 22 protrude from the plastic body 14 starting from the rear side 24, and preferably the several standard industrial connectors 28 also protrude from the plastic body 14.

[0044] To manufacture the electronic component 10, the ceramic heat sink 20 is first connected to the electronic circuit board 12 on the back 24 and subsequently overmolded with the plastic body 14 using the plastic injection molding process.

[0045] The Fig. 2, a detailed view of the Fig. Figure 1c shows the connection of the ceramic heat sink 20 to the electronic circuit board 12 with a printed circuit board 16, particularly on the back side 24. Preferably, several conductive traces 18 are arranged spaced apart from one another on the back side 24 of the electronic circuit board 12 and are connected to the ceramic heat sink 20. For connection to the conductive traces 18, the ceramic heat sink 20 preferably has an interrupted metal coating (not shown) corresponding to the arrangement of the conductive traces 18. Preferably, the ceramic heat sink 20 can have a base body 21 with cooling fins 22 arranged thereon, wherein the base body 21 is preferably positioned flush with an outer surface 30 of the plastic body 14 to allow overmolding with a plastic material and to facilitate positioning in a plastic injection mold.

[0046] Preferably, the base body 21 can be divided into a connection section 35 and a shoulder section 36. The connection section 35 is connected to the electronic circuit board 12, and the shoulder section 36 is preferably formed with a shoulder transverse to a normal direction n of the electronic circuit board 12. This has the advantage that the plastic body 14 encloses the shoulder and thereby secures the ceramic heat sink 20 along the normal direction n and protects it from external forces acting on the connection between the electronic circuit board 12 and the ceramic heat sink 20.

[0047] Furthermore, it may be preferable in this context that the plastic body 14 is produced by double overmolding of the electronic circuit board 12. The plastic body 14 can have a first and a second plastic section 38a,b. Preferably, the shoulder section 36 is designed such that it is overmolded by the first plastic section 38a in a first injection molding process. This has the advantage that the ceramic heat sink 20 can be secured to the electronic circuit board 12 after assembly and overmolding in the first injection molding process. In particular, it is advantageous to use a plastic material that allows for particularly gentle overmolding. The second plastic section 38b can form the outer surface 30 as the outer layer and, for example, additionally seal the electronic component 10 and provide improved surface properties.

[0048] The Fig. 3a and the Fig. Figure 3b shows the electronic circuit board 12 with printed circuit board 16, which is equipped with a variety of exemplary electronic components 34. Electronic components 34 can be mounted on the front side 26 according to the Fig. 3b as well as preferably on the reverse side 24 according to the Fig. 3a. The multiple conductor tracks 18 are also the Fig. 3a, which are arranged on the back 24 of the electronic circuit board 12 and are connected to the ceramic heat sink 20. The conductor tracks 18 are preferably connected to the electronic components 34 on the front 26 and preferably to the back 24 in order to dissipate heat via the ceramic heat sink 20.

[0049] The Fig. 4a to Fig. Figure 4e shows the ceramic heat sink 20 with several cooling fins 22, which extend the surface area of ​​the ceramic heat sink 20 for improved heat dissipation. Fig. Figure 4b shows that the cooling fins 22 are preferably V-shaped. Particularly for overmolding with the previously described plastic body 14, the cooling fins 22 are designed to ensure sufficient mechanical stability for engagement with a plastic injection mold. The V-shape, in particular, enables planar contact between the side faces of the cooling fins 22 and the injection mold.

[0050] The Fig. 4b, Fig. 4c and Fig. Figure 4e further shows that the base body 21 has a connecting section 35 and a shoulder section 36, wherein the shoulder section 36 preferably forms a circumferential shoulder perpendicular to the normal direction n in order to improve the fixation in the plastic body 14.

[0051] The Fig. Figure 4d shows an underside of the ceramic heat sink 20 on which an interrupted metal coating 32, in particular with several stripes, is formed. Preferably, the metal coating 32 is arranged according to the arrangement of the conductor tracks 18 as shown in the Fig. 3a designed to ensure a thermally conductive connection to the ceramic heat sink 20.

[0052] The Fig.Figure 5 shows a preferred embodiment, wherein electronic components 34 are arranged on a front side 26 and a back side 24 of the electronic circuit board 12, and wherein the ceramic heat sink 20 is arranged on the back side 24. Preferably, a current-carrying conductor 18 is formed between the front side 26 and the back side 24 to dissipate heat from the electronic component 34 towards the ceramic heat sink 20. Particularly preferably, the conductor 18 is designed as a through-hole 42, in particular a via, which preferably ensures heat dissipation directly between an electronic component 34 and the ceramic heat sink 20. Furthermore, it may be preferred that at least part of an electronic component 34 is arranged in a space 40 between the ceramic heat sink 20 and the back side 24 of the electronic circuit board 12 to enable a particularly space-saving arrangement.In this context, it may be further preferred that the ceramic heat sink 20 has a recess to accommodate larger electronic components 34, in particular larger than a contact or solder thickness of the connection between ceramic heat sink 20 and electronic circuit board 12, in the space 40.

[0053] The ceramic heat sink 20 is preferably provided with a vapor-deposited conductor track and connected to the circuit board via a solder pad in a soldering process. It is also conceivable that electronic components 34 are arranged laterally to the gap 40, particularly on a side surface of the ceramic heat sink 20. Reference symbol list 10 Electronic components 12 Electronic circuit boards 14 plastic bodies 16 circuit board 18 conductor tracks 20 ceramic heat sinks 21 Basic shapes 22 cooling fins 24 Back of the electronic circuit board 26 Front of the electronic circuit board 28 standard industrial connectors 30 External surface area of ​​an electronic component housing 32 interrupted metal coating 34 electronic component or electronic component 35 Connection section 36 paragraph section 38a,b first and second plastic section 40 space 42 Through-hole plating n Normal alignment of the electronic circuit board

Claims

[1] Electronic component for automation technology with at least one standard industrial connection (28), in particular for sensors and / or actuators, with a plastic body (14) as a housing produced by overmolding an electronic circuit board (12), characterized by , that a ceramic heat sink (20) is arranged on a rear side (24) of the electronic circuit board (12), which protrudes at least partially from the plastic body (14) or forms an outer surface (30) of the housing, wherein electronic components (34) are arranged on a front side (26) of the electronic circuit board (12) and wherein the electronic circuit board (12) has at least one conductor track (18) that connects the electronic components (34) to the ceramic heat sink (20) for heat dissipation. [2] Electronic component according to claim 1, characterized by, that additionally further electronic components (34) are arranged on the back (24) of the electronic circuit board (12), wherein at least some electronic components (34) are arranged in an intermediate space (40) between the ceramic heat sink (20) and the back (24) of the electronic circuit board (12). [3] Electronic component according to claim 1 or 2, characterized by , that the at least one conductor track (18), in particular made of copper, is designed for conducting current, wherein the ceramic heat sink (20) is placed directly on the electronic circuit board (12) and is connected to the at least one current-carrying conductor track (18) for heat dissipation. [4] Electronic component according to any one of claims 1 to 3, characterized bythat the electronic circuit board (12) is made of an insulating material, in particular a plastic material or a plastic composite material, which has a lower thermal conductivity compared to the ceramic heat sink (20) and wherein the at least one conductor track (18) ensures the heat dissipation from the electronic components (34) to the ceramic heat sink (20). [5] Electronic component according to any one of claims 1 to 4, characterized by , that the ceramic heat sink (20) has an interrupted metal coating (32) to connect the ceramic heat sink (20) to several conductor tracks (18) provided on the electronic circuit board (12). [6] Electronic component according to any one of claims 1 to 5, characterized by , that the standard industrial connectors (28) are connected to a front (26) of the electronic circuit board (12) and the ceramic heat sink (20) is connected to a rear (24) of the electronic circuit board (12). [7] Electronic component according to any one of claims 1 to 6, characterized by , that the electronic circuit board (12) has a via (42) which is / are connected to the ceramic heat sink (20) and / or conductor tracks (18) to dissipate heat from the front (26) of the electronic circuit board (12) and the electronic components (34) arranged on it. [8] Electronic component according to any one of claims 1 to 7, characterized by , that the ceramic heat sink (20) has a shoulder section (36) which is overmolded by the plastic body (14) to secure the ceramic heat sink (20) to the electronic circuit board (12) and in the housing. [9] Electronic component according to any one of claims 1 to 8, characterized by, that the plastic body (14) is produced in a high-pressure injection molding process by double overmolding of the electronic circuit board (12), wherein a first plastic section (38a) attaches the ceramic heat sink (20) to the electronic circuit board (12) and a second plastic section (38b) forms an outer surface (30) adjacent to the ceramic heat sink (20). [10] Method for manufacturing the electronic component according to any one of claims 1 to 9, wherein the ceramic heat sink (20) is arranged on the electronic circuit board (12) and is subsequently overmolded with the plastic body (14) by a plastic injection molding process.

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