Method for manufacturing a field device
Vacuum potting with a foaming compound addresses the issue of component damage and disassembly challenges in injection molding, providing protection and recyclability for field devices.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- IFM ELECTRONIC GMBH
- Filing Date
- 2026-01-14
- Publication Date
- 2026-07-23
AI Technical Summary
Injection molding processes for field devices can damage electronic components, and the resulting housings are difficult to disassemble, leading to limited recyclability.
A method involving vacuum potting with a foaming compound, such as polyurethane foam, is used to protect electronic components within a housing, allowing easy disassembly and recycling.
The method effectively protects components from environmental influences and enables cost-effective manufacturing with enhanced recyclability.
Smart Images
Figure EP2026050731_23072026_PF_FP_ABST
Abstract
Description
[0001] Method for manufacturing a field device
[0002] The invention relates to a method for manufacturing a field device, for example, an IO-Link master or another distributor in automation technology. Electronic components of field devices, such as sensors, actuators, control units, and distributors, are often encapsulated in a housing using an injection molding process. This presents the problem that the pressures used in the injection molding process can damage the electronic components. Therefore, it is often necessary to provide electronic components on a printed circuit board with underfills to better protect them from the injected potting compound. Furthermore, it is often necessary to encase the electronic components with a protective covering, such as an additional potting compound or heat-shrink tubing.Furthermore, injection-molded plastic housings are typically used, which are manufactured, for example, by overmolding the electronic components. Field devices manufactured in this way are difficult or impossible to disassemble at an economically viable cost. Consequently, the raw materials used cannot be recycled, or can only be recycled to a very limited extent.
[0003] The object of the invention is to provide a method for manufacturing a field device which makes it possible to attach electronic components inside the housing of the field device and protect them from moisture, as well as to provide a field device which is cost-effective to manufacture and can be recycled well.
[0004] The problem is solved by a method according to claim 1. Advantageous embodiments of the invention, as well as a field device manufactured according to the method and a method for recycling such a field device, are specified in the dependent claims.
[0005] Advantageously, a method for manufacturing a field device with a housing is specified, the method comprising the following steps:
[0006] - Mounting components of the field device in the housing and closing the housing;
[0007] - Arranging the housing in a vacuum potting device, wherein the inside of the housing is connected via a first valve to a foam chamber and via a second valve to a vacuum pump of the vacuum potting device;
[0008] - Foaming and providing a foaming potting compound in the foaming chamber;
[0009] - Evacuating the interior of the housing using the vacuum pump, so that a target pressure Psou in the range of 1 mbar to 100 mbar is established inside the housing; - Closing the second valve when the target pressure Psou is reached and introducing the foam from the foam chamber into the interior of the housing by opening the first valve.
[0010] This has the advantage that a foam potting compound is provided, thus protecting field device components from environmental influences. In particular, no special precautions need to be taken to protect electronic components from high injection molding pressures. A further advantage is that a field device manufactured in this way can be easily recycled.
[0011] The potting compound can be, for example, a polyurethane foam such as Nafturan. Preferably, the target pressure Psou is selected in the range of 10 mbar to 30 mbar. Advantageously, the potting foam is produced using ambient air and / or at atmospheric pressure. For example, the foam chamber can be connected to the environment via an air filter. An ambient pressure Pext can be in the range of 0.95 bar < P exThe pressure difference (t) should be less than 1.1 bar. This has the advantage that the potting foam in the foam chamber can be rapidly transported into the housing interior due to the pressure difference AP = Pext - Psou. In particular, the foam bubbles forming the potting foam can be largely preserved by this rapid transport. Furthermore, the generated negative pressure promotes the distribution of the potting foam within the housing, allowing the foam to flow into undercuts or narrow gaps, for example.
[0012] Evacuation of the housing interior, starting from normal ambient pressure, can preferably be carried out within an evacuation time of < 20 s, and particularly advantageously within an evacuation time of < 10 s (P2024.1360-WÖ / JH - 3). This enables a short process duration. Advantageously, the closing of the second valve and the opening of the first valve overlap in time. This allows for a particularly short process time and thus cost-effective manufacturing of the field device.
[0013] In some embodiments of the method, it is preferred that arranging the housing in the vacuum potting device includes sealing the housing by means of the vacuum potting device. For example, it may be provided that one or more interfaces, such as IO-Link sockets or a bus interface, are sealed before the target pressure is set. In particular, it may be provided that the housing is inserted into a mold that is complementary to the housing and sealed by means of the mold.
[0014] In some further developments of the method, it is provided that an overpressure Pi is applied to the foam chamber before the first valve is opened, where Pi > 3 bar, and in particular where Pi > 5 bar. It is especially preferred that the pressure Pi is reduced to a pressure P2 < 2 bar after the first valve is opened, after which the first valve can be closed. For example, P2 can be equal to the external pressure P. exThe pressure t (for example, approximately 1 bar) of the external environment can be selected. Such a procedure can be advantageous for preserving the bubbles of the foamed potting compound during transport into the housing interior.
[0015] In some embodiments, the housing comprises a metallic housing body. The process then preferably includes a step for forming the housing body using a deep-drawing process. This has the advantage that a significant portion of the housing can be formed in one piece. This allows for the provision of an easily sealable housing and facilitates the production of the field device using the vacuum potting process. Furthermore, it also enables the production of a field device whose housing consists primarily of stainless steel. In particular, the housing can be manufactured with only a few connection points between different housing components, which is advantageous, for example, for applications with high hygiene or sealing requirements.Another advantage is that such a field device can be easily recycled, as the metallic housing can be separated relatively easily from the components inside.
[0016] In a further aspect of the invention, a field device comprising a housing and a printed circuit board is provided, wherein the field device was manufactured according to a method described above and wherein the printed circuit board is at least partially surrounded by a foam potting compound formed from the potting compound and fixed in the housing. Thus, the printed circuit board can be securely fixed inside the housing and, in particular, protected against vibrations and / or ingress of moisture.
[0017] Preferably, the housing comprises a metallic housing body and a metallic housing base, the housing body being a deep-drawn part. Such a design can meet high requirements for hygiene and / or sealing.
[0018] It is particularly advantageous if the housing base is connected to the housing body by a force-fit and / or form-fit connection. In some embodiments, the housing base can be bent towards the inside of the housing at an edge. Advantageously, a circumferential side wall of the housing body and a circumferential side wall of the housing base can run parallel to each other, at least in sections, and be fastened to each other, for example, by means of a press fit. Furthermore, at least one sealing element, for example, a circumferential sealing lip, can be formed between the side wall of the housing base and the side wall of the housing body.
[0019] A particularly advantageous feature is that the foam encapsulation, including the circuit board, can be pressed out of the housing body, at least after removing the housing base. For example, a field device designed as a distributor, such as an IO-Link master, can be designed such that the foam encapsulation, including the components surrounded by it, can be pressed out by applying a pressing force. In particular, it can be provided that the pressing force is applied via interface openings in the housing body. A force-fit connection between the housing body and the housing base has the advantage that the housing can be opened in the same pressing process as the removal of the foam encapsulation. Likewise, a positive-locking fastening can also be provided and designed such that the housing base can be detached from the housing body by means of the pressing process.This allows for the provision of a field device that can be easily recycled.
[0020] Furthermore, the housing body can be designed with recesses for accommodating interfaces, such as sockets or plugs of a bus interface or an IO-Link interface. These recesses can, in particular, include deep-drawn recesses in the housing body with openings for receiving an interface element complementary to the interface, such as an IO-Link connector. Additionally, external or internal threads can be provided on the recesses for fastening the respective complementary interface elements. Advantageously, sealing elements are provided on the recesses or interfaces to prevent the ingress of dirt or moisture and to ensure an airtight seal of the housing, even in the area of the interfaces.
[0021] In some advanced versions of the field device, the housing base includes one or more indentations pointing towards the interior of the housing. For example, a housing base manufactured as a deep-drawn part may have corresponding indentations. It is particularly advantageous to incorporate thermally conductive elements, such as thermal pads, between these indentations and a circuit board of the field device. These thermally conductive elements can then act as a thermal bridge to dissipate thermal energy from the circuit board, through the housing, to the surrounding environment. In particular, the thermally conductive elements can also be partially surrounded by the foam potting compound and held or secured in position by it.
[0022] Preferably, the field device is a network component of a data bus or an IO-Link system. Such field devices typically have interfaces that are arranged in corresponding openings in the housing body or can be contacted via it. These openings can then be used to apply pressure to the foam potting compound during recycling of the field device. The foam potting compound can thus be pressed out of the housing or the housing body. The invention is explained in more detail below with reference to exemplary embodiments and the drawings.
[0023] They show schematically:
[0024] Figure 1 shows a perspective view of a field device;
[0025] Figure 2 shows a top view of the field device of Figure 1;
[0026] Figure 3 shows a side view of the field device from Figures 1 and 2;
[0027] Figure 4 shows a sectional view of the field device from Figure 2 along a section line HH, as well as a schematic arrangement of the field device in a vacuum potting device with a foam chamber and a vacuum pump;
[0028] Figure 5 shows a view of the field device in the sectional view of Figure 4, with a schematically represented foam potting element; and Figure 6 shows a sectional view of the field device along section line AA from Figure 3 with a schematically represented foam potting element; , In the following description of the preferred embodiments, the same reference numerals denote the same or comparable components.
[0029] Figures 1 to 3 show a perspective view, a top view, and a side view of a field device 1 configured as an IO-Link master. The field device 1 comprises a housing 3 with a metallic housing body 5 and a metallic housing base 6. A total of eight IO-Link interfaces 7 are provided on the top surface of the housing 3, by means of which further field devices, such as sensors or actuators, can be integrated into an IO-Link network. Furthermore, two optical indicators 9 are provided on the top surface of the housing at each IO-Link interface 7, each of which, for example, includes at least one LED. The housing body 5 is a thermoformed part.
[0030] The housing body 5 has a circumferential rim region, which forms an outer side wall 5b of the housing 3. Furthermore, the housing base 6 also has a circumferential rim region, which forms an inner side wall 6b of the housing. The side walls 5b and 6b run parallel at least partially and are positively connected to each other. A seal 15, designed as a sealing lip, is also provided between the outer side wall 5b and the inner side wall 6b. Alternatively or additionally, a positive-locking connection between the housing body 5 and the housing base 6 can also be provided.
[0031] The housing body 5 has a total of eight recesses 21, each of which has an opening for accommodating one of the IO-Link interfaces 7. The recesses 21 are each deep-drawn. A seal 27 is formed between each element of the IO-Link interfaces 7 and the recesses 21. For example, the seals 27 are formed between a spring element of the IO-Link interfaces 7 and the corresponding recess 21 of the housing body 5. An additional seal 29 is formed on each inner support component of the IO-Link interfaces 7. The seals 27 and 29 provide effective protection against the ingress of moisture. Furthermore, the housing 5 can also be sealed in the area of the IO-Link interfaces 7 / recesses 21 by means of the seals 27 and 29 for vacuum potting.
[0032] Figure 4 shows a sectional view of the field device 1 along section line HH (see Figure 2), as well as a schematic representation of a vacuum potting device 40. The sectional view also shows curved projections 11 of the housing base 6, extending towards the interior of the housing, as well as a circuit board 13 and a cavity 101. The field device 1 is attached to the housing 3 at two end regions by retaining elements 41 of the vacuum potting device 40. A foam chamber 51 with a foam generator 53 is provided for potting the interior of the field device 1. The foam chamber 51 also includes an air filter 55 and is at least partially filled with a foaming potting compound 57. The foaming potting compound 57 can be fed into the interior of the housing 5 via a first line 61, which can be opened and closed by means of a first valve 63.The first line 61 can, for example, have a circular cross-section with a diameter di in the range of 10 mm < di < 30 mm. The foam chamber 51 is advantageously arranged as close as possible to the field device 1, so that the first line 61 can be correspondingly short. An overall length Li of the first line 61 of less than 30 cm is advantageous.
[0033] To pot the interior of the housing of the field device 1, the foaming potting compound 57 located in the foam chamber 51 can be foamed, with the first valve 63 closed. A vacuum pump 71 is also provided to generate a vacuum; this pump is connected to the interior of the housing via a second line 81. A vacuum reservoir 73 can optionally be provided. The second line 81 can be opened and closed by means of a second valve 83.
[0034] Advantageously, a target pressure Psou is set inside the housing, where Psou is selected to be in the range 1 mbar < Psou < 100 mbar, and particularly in the range 15 mbar < Psou < 30 mbar. Once the target pressure Psou has been established inside the housing, the second valve 83 can be closed. During or after the closing of the second valve 83, the first valve 63 can be opened, allowing the foam (foaming potting compound 57) in the foam chamber 51 to flow into the housing interior. The foam chamber 51 is connected to an external pressure Pext via the air filter 55, where Pext > Psou. For example, the air filter 55 can provide a connection between the foam chamber 51 and ambient air at normal atmospheric pressure. The external pressure P ex t can therefore be advantageously converted to P exThe pressure difference AP = Pext - Psou is selected to be 1 bar. The foam 57 located in the foam chamber 51 is thus forced into the interior of the housing via the first line 61 due to the pressure difference AP = Pext - Psou. This allows up to 99% of the cavity 101 to be filled with the foam 57. In particular, the combination of a short first line 61, a comparatively large diameter of the first line 61, and the pressure difference AP can be advantageous, enabling rapid transport of the foamed potting compound 57 into the housing 3 and ensuring that the bubbles in the foamed potting compound 57 are retained during transport.
[0035] Alternatively, instead of the external ambient pressure Pext, an overpressure Pi can be set at the foam chamber. For example, the overpressure Pi can be greater than 3 bar, and in particular greater than 5 bar. After opening the first valve 63, the pressure applied to the foam chamber 51 can be reduced to a pressure P2 < 2 bar, and the first valve 63 can then be closed.
[0036] For example, P2 can be equal to the external pressure P ex t of the external environment.
[0037] To connect the first supply line 61 and the second supply line 81 to the interior of the housing, two openings can be formed on the housing 3. These openings are closed by means of a closure, for example in the form of a plug, before the foam has fully cured. For example, a plug made of a material comprising a fluoroelastomer, a fluororubber, or a ceramic can be used. Optionally, an additional cover can be attached to the housing base 6 to close each of the two openings. After a waiting period for the foaming potting compound 57 to cure, a foam potting body 103 can finally be formed (see Figures 5 and 6).
[0038] The foam potting compound 103 can provide a seal against contamination, moisture, and / or protection against chemical substances such as cleaning agents. Furthermore, the foam potting compound 103 can reduce vibrations and, for example, securely mount the printed circuit board 13. The foam potting compound 103 is shown schematically only in contact with the underside of the printed circuit board. Of course, the top side of the printed circuit board 13 can also be at least partially encased by the foam potting compound 103.
[0039] Figures 5 and 6 each show a sectional view of the field device 1, with Figure 5 showing a section along section line HH and Figure 6 showing a section along section line AA. In contrast to Figure 4, the field device 1 in Figures 5 and 6 is shown after the vacuum potting process. In particular, the foam potting body 103 produced by the vacuum potting process is also shown schematically in each figure.
[0040] The housing base 6 has several projections 11 extending towards the interior of the housing, thereby reducing the distance between the printed circuit board 13 and the housing base 6 in certain areas. Thermal bridges, for example in the form of thermal pads 31, can be provided between the printed circuit board 13 and the projections 11 to dissipate thermal energy. Advantageously, the distance d between the projections 11 and the printed circuit board 13 is chosen to be in the range of 1 cm < d < 3 cm. This allows for a short and direct heat path between the printed circuit board 13 or components mounted on it and the housing base 6, enabling efficient dissipation of thermal energy to the environment. Furthermore, the projections 11 increase the surface area of the metallic housing base 6, thus improving heat transfer from the interior of the housing to the housing base 6 and / or from the housing base 6 to the environment.Furthermore, the stability of the housing 3 can be improved by means of the features 11. The features 11 are shown as examples of indentations / bulges formed in a deep-drawing process.
[0041] Figure 6 further illustrates an example of a pressing force F for ejecting the foam potting element 103 and, if applicable, other components of the field device. The pressing force F can be applied by means of a suitable device at the IO-Link interfaces 7 or via the corresponding openings of the molded recesses 21, so that the housing base 6 can be detached and the foam potting element 103, including the circuit board 13, can be ejected. Thus, the field device can be easily disassembled and recycled. Reference numeral list
[0042] 1 field device
[0043] 3 cases
[0044] 5 Housing bodies
[0045] 5b Side wall
[0046] 6 Case base
[0047] 6b Side wall
[0048] 7 IO-Link interfaces
[0049] 9 optical display
[0050] 11. Shaping
[0051] 13 Circuit board
[0052] 15 sealing element
[0053] 21. Shaping
[0054] 25 spring element
[0055] 27 Seal
[0056] 29 Seal
[0057] 31 thermal pads
[0058] 40 Vacuum potting device 41 Holding device
[0059] 51 foam chamber
[0060] 53 Foam generator
[0061] 55 Air filters
[0062] 57 foaming potting compound 61 first line
[0063] 63 first valve
[0064] 71 Vacuum pump
[0065] 73 Vacuum pre-tanks
[0066] 81 second line
[0067] 83 second valve
[0068] 101 Cavity
[0069] 103 Foam potting compounds
[0070] F Press force
Claims
P2024.1360-WÖ / JH - 12 - Patent claims 1. Method for manufacturing a field device (1) with a housing (3), the method comprising the steps: - Mounting components of the field device (1) in the housing (3) and closing the housing (3); - Arranging the housing (3) in a vacuum potting device (40), wherein the inside of the housing is connected via a first valve (63) to a foam chamber (51) and via a second valve (83) to a vacuum pump (71) of the vacuum potting device (40); - Foaming and providing a foaming potting compound (57) in the foam chamber (51); - Evacuating the inside of the housing using the vacuum pump (71) so that a target pressure Psou in the range of 1 mbar to 100 mbar is established inside the housing; - Closing of the second valve (83) when the target pressure P is reached S0n and introduction of the foaming potting compound (57) from the foam chamber (51) into the interior of the housing by opening the first valve (63).
2. Method according to claim 1, wherein the target pressure P S0 n is selected to lie in the range of 10 mbar to 30 mbar.
3. Method according to claim 1 or 2, wherein the closing of the second valve (83) and the opening of the first valve (63) overlap in time.
4. Method according to any one of claims 1 to 3, wherein the arrangement of the housing (3) in the vacuum potting device (40) comprises an airtight sealing of the housing (3) by means of the vacuum potting device (40).
5. A method according to any one of the preceding claims, comprising applying an overpressure Pi to the foam chamber (51) before opening the first valve (63), wherein Pi > 3 bar, in particular wherein Pi > 5 bar.
6. A method according to claim 5, comprising reducing the pressure Pi to a pressure P2 < 2 bar after opening the first valve (63).
7. Method according to any of the preceding claims, wherein the housing (3) comprises a metallic housing body (5), the method comprising a step for forming the housing body (5) by means of a deep drawing process.
8. Field device (1) comprising a housing (3) and a printed circuit board (13), wherein the field device (1) was manufactured according to a method according to one of the preceding claims, and wherein the printed circuit board (13) is at least partially surrounded by a foam potting body (103) formed from the foaming potting compound (57) and is fixed in the housing (3).
9. Field device (1) according to claim 8, wherein the housing (3) comprises a metallic housing body (5) and a metallic housing base (6), and wherein the housing body (5) is a deep-drawn part.
10. Field device (1) according to claim 9, wherein the housing base (6) is connected to the housing body (5) by friction and / or form-fitting means, and wherein the foam potting body (103) including the circuit board (13) can be squeezed out of the housing body (5) at least after the housing base (6) has been removed.
11. Field device (1 ) according to one of claims 8 to 10, wherein the field device (1 ) is a network component of a data bus or an IO-Link system.
12. Method for recycling a field device (1) designed according to one of claims 8 to 11, comprising separating the housing (3) from the foam potting body (103) and the circuit board (13) surrounded by the foam potting body (103), wherein the separation is carried out by squeezing out the foam potting body (103) including the circuit board (13).