System assembly, pressure sensor assembly and method for producing a system assembly

Abstract

The invention relates to a system assembly. The system assembly has a printed circuit board which is fastened to a support structure by means of a closed adhesive contour. The support structure has a means of ventilation which is designed to discharge gases from the space between the printed circuit board and the support structure that is enclosed by the adhesive contour.

Description

[0001] P2024, 0771 WO N 4. August 2025

[0002] 1

[0003] Description

[0004] System arrangement, pressure sensor arrangement and method for manufacturing a system arrangement

[0005] In many applications and system configurations, it is necessary to mount printed circuit boards (PCBs) onto a substrate. This can be done, for example, by adhesive bonding. It may be essential that the adhesive bond does not trap air bubbles. Uncontrolled gas migration can also lead to further disadvantages.

[0006] Previous approaches had problems and were sometimes unsatisfactory.

[0007] Accordingly, according to claim 1, a system arrangement is provided which at least partially solves the aforementioned problems or other problems mentioned below, or which can improve a condition. Further advantageous embodiments, which also either improve the aforementioned problems or bring about improvements mentioned below, are described in dependent claims, in subclaims, or below in the context of embodiments and exemplary embodiments.

[0008] According to a first embodiment, a system arrangement is described which includes a printed circuit board. This printed circuit board is attached to a carrier by means of a closed adhesive contour. The carrier can be any type of carrier, for example, it can be an enclosure, but is not limited to this. It can also be a flat carrier. A venting device is formed in the carrier, which is described in P2024, 0771 WO N 4. August 2025.

[0009] 2 is designed and intended to drain gases from a gap formed or emerging between a printed circuit board and the substrate, which is created by the closed adhesive contour.

[0010] The corresponding adhesive bond, particularly due to the closed adhesive contour, offers the advantage of a stable bond. Unlike previous adhesive bonds, which were, for example, fully bonded, meandering, or cross-shaped, this design, in conjunction with the venting device, allows gases to be vented from the volume enclosed by the adhesive contour, the circuit board, and the substrate during or after the manufacturing process. For example, it may be necessary to degas or cure some adhesives, e.g., by means of heat treatment. Pressure differentials or gas migration may also occur for other reasons. If no venting device is provided in such a case, gases can migrate through the adhesive, potentially leading to blistering within the material.This can negatively affect the quality of the bond, but also the functionality of the entire system assembly. The venting device at least reduces the tendency for bubbles to migrate through the adhesive structure.

[0011] The aforementioned structure can also have the advantage that other components, which may be arranged on or above the printed circuit board and which may be sensitive to gas migration, can also be better protected from gas migration or, in particular, from bubble formation. P2024, 0771 WO N 4. August 2025

[0012] 3

[0013] The volume enclosed by the adhesive contour may in particular be a passive volume that has no functionality in the system arrangement during its operation.

[0014] The adhesive used to form the bond line is not limited. Depending on the preferred design, it could be, for example, an epoxy adhesive or a silicone adhesive.

[0015] According to another embodiment, which may be preferred, the venting device can be designed as a venting channel extending through the carrier. A venting channel can, for example, be a bore through the carrier at a suitable location. The venting channel or bore can, for example, begin below the bonded printed circuit board, so that the volume enclosed by the surrounding adhesive contour is in contact. The venting channel can further extend to any point on an outer surface of the carrier facing away from the adhesive side.

[0016] Such a venting channel has proven to be easy to implement from a process engineering perspective. It can, for example, be incorporated during the manufacturing of the support, especially if it is a molded part. In the case of a bore, this can be introduced into the support in one or more simple process steps.

[0017] The venting device or venting channel may, in particular, have no function other than its venting function of the volume enclosed by the adhesive contour for P2024 , 0771 WO N 4 . August 2025

[0018] 4. The operation and functionality of the system arrangement. For example, functional openings can be additionally implemented, as described below.

[0019] According to another design, the exiting end of the vent can be sealed with a separate seal. Such a seal could be, for example, a membrane, a sticker, or a hot-stamped closure. In some cases, this can offer advantages in that it makes it more difficult for contaminants to penetrate the vent.

[0020] According to a design preferred in some cases compared to the previous embodiment, the exiting end of the vent channel can also be free of a separately implemented or installed seal. The inventors have discovered that a separate seal can unexpectedly be dispensed with, which allows for a simpler process. Furthermore, alternative measures can be taken to prevent the ingress of contaminants.

[0021] According to one embodiment, an external opening of the vent can exit the support at such a point that a structural component at least partially obscures the external opening. This obscuration can be a spatial arrangement that makes spatial access to the vent outlet more difficult. Examples are given below of components that can obscure a corresponding outlet hole or external opening in specific applications. Such obscuration can have the advantage that a P2024, 0771 WO N 4 August 2025

[0022] 5. Subsequent sealing using the measures mentioned above can be avoided. This provides protection against contamination and a simpler process.

[0023] According to another version, the outer opening of the vent channel can be less than or equal to 2.5 mm. 2The inventors of the present invention have determined that a corresponding external cross-section may be sufficient to ensure ventilation.

[0024] According to one design, the vent channel can have the diameters described here along its entire length. This is particularly easy to achieve in the case of a bore.

[0025] According to one design specification, the minimum size of the vent channel can be, for example, a cross-section of 0.1 mm². 2 or larger. Preferably it can be 0.5 mm. 2 or larger. This results in design forms with an outer cross-section or cross-section over the entire length of 0.1 mm. 2 up to 2.5 mm 2 or 0.5 mm 2 up to 2.5 mm 2 According to one design specification, the diameter can be, for example, 0.7 ± 0.1 mm. 2 be.

[0026] According to another embodiment, passivation can be provided on one side of the printed circuit board (PCB), preferably not the side where the PCB is bonded to the substrate, which at least partially covers the PCB and / or components on it. Such passivation can preferably completely cover an area of ​​the PCB facing away from the bonded side, including all components located on that side. P2024, 0771 WO N 4, August 2025

[0027] 6

[0028] In the aforementioned embodiment, the circumferential adhesive structure and the venting device are particularly advantageous. Without these structures, the passivation would provide a pathway for escaping gases, such as escaping air. In this case, bubbles can form within the passivation. For example, gas migration can occur when the passivation is heated or cured. The adhesive contour and the venting device can reduce or prevent bubble formation within the passivation.

[0029] Passivation can be, for example, an applied gel that encapsulates or surrounds components on the printed circuit board. Alternatively, solid or foam-based passivations can be used. The gel could be, for example, a silicone gel. Alternative passivations could be, for example, a fluorosilicone or an epoxy or polyurethane potting compound. These can be gel-based, foam-based, or solid, depending on the specific case. A gel can be applied as a gel layer or as a gel potting compound.

[0030] According to another design, the adhesive contour can mimic or correspond to the outer contour of the printed circuit board. This can offer the advantage of a particularly strong bond.

[0031] According to a preferred embodiment, the adhesive contour can be designed such that it completely replicates or corresponds to the outer contour of the printed circuit board (PCB), and that, at least in the installed, i.e., bonded, state, there are no undercuts between the PCB and the substrate. Consequently, the side of the PCB facing the substrate is in its P2024, 0771 WO N 4. August 2025

[0032] 7

[0033] The edge area is covered by the adhesive, and all areas on this side of the circuit board free of adhesive are located within the adhesive contour. Accordingly, in the current design, there are no free areas of the circuit board at the edge that face the substrate to which the circuit board is glued and that lie outside the adhesive contour.

[0034] The aforementioned design has the advantage that, particularly in the case of the aforementioned passivation, but also in other cases of components that may be sensitive to gas migration, no air volumes are created that could cause gas migration through the passivation or through the adhesive contour.

[0035] According to another preferred embodiment, no further adhesive bonds are formed within the closed adhesive contour. Additional adhesive structures within the contour can pose the risk of forming separate, enclosed air volumes that cannot be vented via the venting device because it does not contact these volumes. Accordingly, an adhesive contour free of such additional internal adhesive structures is preferred, as otherwise bubble formation is more likely.

[0036] According to a preferred embodiment, the support can be an enclosure or part of an enclosure. For example, an enclosure can hold a printed circuit board. This can be arranged, for example, on the floor inside the enclosure. The enclosure can also include additional walls or components, forming part of P2024, 0771 WO N 4. August 2025

[0037] 8 have a different orientation than the base of the enclosure on which the circuit board is located.

[0038] Building upon the previous embodiment, the enclosure can, according to a further embodiment, for example comprise a housing and a lid. The lid can be designed to close the housing. The circuit board can, for example, be arranged inside the housing or on its base.

[0039] An enclosure can have the advantage that the printed circuit board can be embedded in a closed internal volume and thus better protected. Such an enclosure can also facilitate the application of a potting compound, such as a gel potting compound, for passivation, as the walls can prevent the potting compound from running.

[0040] According to another embodiment, the printed circuit board can be designed such that no sensitive components are present on the side where the adhesive contour is applied. "Sensitive" can be defined according to the specific application for which the system arrangement is designed or intended. For example, a component can be classified as sensitive if it can be damaged by contaminants or moisture penetrating through the unsealed vent channel. In the design according to the invention, only the volume enclosed by the adhesive contour is exposed to certain media, such as moisture or contaminants, via the vent channel. The adhesive contour prevents these from penetrating further into the interior and, in particular, to the other side of the printed circuit board, which may, for example, have sensitive structures. By avoiding P2024, 0771 WO N 4. August 2025

[0041] With nine sensitive components on the bonded side, a robust system arrangement can be provided using a simple, inventive design. These components can be, in particular, electronic components.

[0042] According to another embodiment, the underside of the circuit board, where the adhesive contour is applied, can also be free of any components. This can further improve its robustness.

[0043] A pressure sensor arrangement is described according to another embodiment. This arrangement exhibits all the features of the system arrangement according to one or more of the embodiments mentioned above. Furthermore, a pressure sensor function is implemented in the pressure sensor arrangement. The pressure sensor arrangement represents an example of a system arrangement. For example, the pressure sensor arrangement could be a relative pressure sensor. In this case, external pressure can be present inside an enclosure. The pressure to be measured is present within an application, e.g., on a connector through which the pressure sensor is connected to a system.

[0044] In the case of a sensor, the air volume enclosed by the adhesive contour can be, in particular, a passive volume that does not contribute any sensor functionality. The venting device, as described above, can also be independent of the sensor functionality. For example, separate openings for the sensor functionality can be implemented depending on the sensor type.

[0045] In particular, for a pressure sensor system, according to one implementation form, the venting device P2024 , 0771 WO N 4 . August 2025

[0046] 10. Functionally separate from the external opening and the connector. According to another variant of this design, the venting device is exclusively designed to vent gases from a space enclosed between the circuit board and the substrate by the adhesive contour. For example, in a pressure sensor system, one or more separate external openings can be implemented, which, for the measuring functionality, connect the external pressure with a pressure-sensitive measuring device arranged in the pressure sensor. For example, in a differential pressure sensor, the pressure can be measured between an external opening and a connector, where the venting device is a separate opening and the volume enclosed by the adhesive contour is a non-functional volume.

[0047] According to another embodiment of the pressure sensor arrangement, the structural component can be, in particular, a connector, a seal, or a sensor receptacle. These components can spatially obstruct or cover the opening of the vent channel or venting device. A seal can even allow for complete closure. For example, the outlet of the vent channel can be located close to a connector with which the pressure sensor arrangement can be connected to a system to be measured. In this way, at least the connector, but also potentially the system to be measured, can represent a spatially steric barrier to contaminating media within an application and make ingress more difficult.In particular, a seal that seals the connection between the fitting and the system can also enable or facilitate complete sealing. P2024, 0771 WO N 4. August 2025.

[0048] 11

[0049] According to another embodiment, a method for manufacturing a system arrangement is specified. A pressure sensor arrangement can also be manufactured using the same method. The characteristics described above for both the system arrangement and the pressure sensor arrangement apply accordingly. The advantages mentioned above can therefore result. The characteristics and embodiments described within the framework of the method can also represent characteristics or embodiments of the system arrangement or the pressure sensor arrangement.

[0050] The method, according to one embodiment, can include providing a substrate and a printed circuit board (PCB). Furthermore, a closed adhesive contour is provided on the PCB or on the substrate. This can be applied or otherwise provided. The closed adhesive contour is preferably arranged or applied to the PCB. Alternatively, the adhesive contour can also be provided on the substrate at a location designated or designed for attaching the PCB. Subsequently, the PCB is adhered to the substrate by means of the adhesive contour. Parts of the adhesive contour can also be applied to both the PCB and the substrate. A closed adhesive contour can then be formed by joining these parts.

[0051] According to one embodiment of the method, a venting device can be formed in the carrier below the point for attaching the printed circuit board, such that the aforementioned construction is created. This venting device can be a venting channel. This can be, for example, from P2024, 0771 WO N 4, August 2025.

[0052] 12. The vent channel can be provided for in advance, for example, by manufacturing the carrier accordingly, or it can be introduced as a hole in a process step. Generally, the vent channel can also be introduced by other means. The hole can be created at any point in the process before degassing or venting is necessary. Preferably, the hole can be made before the printed circuit board is attached using the adhesive contour. Drilling a hole afterward carries the risk of damaging the printed circuit board or introducing contaminants into the adhesive or the system.

[0053] According to another implementation, a heating step can be carried out either as part of the process of gluing the printed circuit board to the substrate or as a separate step afterwards. This heating step cures the adhesive bond.

[0054] According to another implementation method, a passivation layer can also be applied, for which the characteristics described above may apply. This can be solidified by a heating step. "Solidified" here does not necessarily mean that a hard state is achieved. Solidification transforms a liquid state into a non-liquid state. Even after solidification, a gel-like state, for example, may still be present. The heating or solidification step can be a separate step from the aforementioned step of heating the adhesive contour. Alternatively, the heating step can be performed in conjunction with the heating step.

[0055] According to another embodiment of the method, the adhesive contour can be applied in such a way that before gluing or P2024 , 0771 WO N 4 . August 2025

[0056] 13

[0057] When pressing the circuit board onto the substrate, undercuts may still be present along the outer contour of the circuit board. Such undercuts may also be absent. However, after bonding or at the latest after heating, it is preferable that, as mentioned above, no such undercuts are present. For example, the adhesive, while still soft, can be pressed or deformed in such a way that undercuts disappear completely.

[0058] Further embodiments may arise from the explanations of the exemplary embodiments described below. The invention is not limited to the exemplary embodiments shown below. In particular, one exemplary embodiment is explained with reference to various figures. In the figures, both absolute dimensions and ratios may be distorted. The invention is not limited to the dimensions or ratios shown. Unless otherwise stated, no dimensions or ratios can generally be derived from the figures.

[0059] Figure 1 shows an exploded view of an exemplary embodiment of a pressure sensor arrangement.

[0060] Figure 2 shows a view of the underside of the exemplary embodiment of the pressure sensor arrangement.

[0061] Figure 3 shows a view of the underside of the circuit board with an adhesive contour according to the exemplary embodiment of the pressure sensor arrangement.

[0062] Figures 1 to 3 show an exemplary embodiment of a pressure sensor arrangement. This pressure sensor arrangement P2024, 0771 WO N 4, August 2025

[0063] Figure 14 is an embodiment of a system arrangement. Figure 1 shows an exploded view of the pressure sensor arrangement. Figure 2 shows a view of the underside of the pressure sensor arrangement. Figure 3 shows the circuit board 4 from the underside with the adhesive contour 8 applied to it.

[0064] The pressure sensor assembly has an enclosure 1. The enclosure 1 consists of a housing 2 and a cover 3, as shown in the exploded view. The interior of the enclosure 1, or housing 2, is designed as a two-chamber structure with a main chamber 22 and a pre-chamber 21. A labyrinth seal is formed between the pre-chamber and the main chamber by corresponding housing and cover structural components, as partially shown in the exploded view. The cross-section of this seal at its narrowest point is smaller than the sum of the cross-sections of the external openings 24, which can be seen in the view in Figure 2. These external openings 24 contact the pre-chamber 21. The labyrinth seal connects the pre-chamber 21 to the main chamber 22. Thus, the main chamber 22 is under external pressure.

[0065] The main chamber 22 has a designated space for the placement of a printed circuit board 4. The printed circuit board 4 can be glued into the corresponding space within the main chamber 22 using the adhesive contour 8, which is explained in more detail below. The housing 2, or more generally the enclosure 1, therefore represents an example of a support.

[0066] Circuit board 4 has electronic components on its upper side, which are visible in the structures and in the illustrations, but which are part of P2024, 0771 WO N 4. August 2025

[0067] 15

[0068] For clarity, no separate reference symbols are given. Some of the components are connected to the connecting leads 6 via the wiring 5. The connecting leads 6 lead to a connector 10. The electronics can be contacted via the connector 10 using a complementary connector within an application or within a measuring system, for example, to be read or controlled.

[0069] Furthermore, the housing has a connector 9. This is designed so that the pressure sensor assembly can be connected to a system to be measured. In this way, the pressure of the corresponding system can be determined relative to the external pressure. A pressure sensor function is implemented internally above or as part of the connector.

[0070] The connection to the external system, whose pressure is to be measured, can be made using seal 11. The corresponding connection design can be a plug seal.

[0071] As described, the printed circuit board 4 is attached to the housing with the closed circumferential adhesive contour 8. In Figure 8 and Figure 3, the adhesive contour 8 is shown in the form it is applied during the manufacturing process. As can be seen, undercuts or free areas are still visible on the outer perimeter of the adhesive contour 8 and on the outer edge of the printed circuit board 4. By gluing or inserting the board, the adhesive contour 8 is preferably widened and spread in such a way that the undercuts disappear. As can be seen, this is due to the adhesive contour 8 below the printed circuit board 4. P2024, 0771 WO N 4. August 2025

[0072] 16 enclosed volumes are non-functional, i.e., not involved in the operation of the differential pressure sensor.

[0073] Furthermore, the housing 2 has a vent channel 12 on its underside, which is an embodiment of the venting device described in the introduction. The vent channel 12 is positioned within the enclosure, i.e., in the housing 2, such that it contacts the area enclosed by the circumferential adhesive contour 8, i.e., the air volume formed between the circuit board, the circumferential adhesive contour 8, and the housing. The vent channel 12 terminates on the outside of the housing near the connector 9, or at its base. The seal 11 overlaps, at least spatially, the immediate outer volume of the outlet of the vent channel 12, just as the connector 9 does. This allows the outlet of the vent channel 12 to be at least partially protected from media such as splashing water or dirt. Further protection for the components inside is provided by the closed circumferential adhesive contour 8.Furthermore, no electronic components are arranged on the underside of the circuit board, thus the circuit board forms a kind of seal against contamination. The vent channel has a cross-sectional area of ​​0.7 mm². 2 on, which can be easily manufactured by injection molding or drilling. Alternatively, the cross-section of the vent channel can be between 0 and 1 mm. 2 and 2.5 mm 2 be .

[0074] As can be seen in Figures 1 and 2, the vent channel 12 is also a non-functional component with regard to the operation of the differential pressure sensor. As shown, the pressure is measured between the external opening 24 and the connector 9. The vent channel 12 is P2024, 0771 WO N 4, August 2025.

[0075] 17 is trained separately and has no function to actively measure a functional volume within the sensor.

[0076] Furthermore, as shown in the exploded view in Figure 7, a gel layer 7 is arranged as passivation on the top side of the circuit board and thus protects the electronic components.

[0077] The overall design has the advantage that no gas is trapped in the system during a degassing or heating step without being able to escape easily. In particular, all the gas below the circuit board 4 can escape via the vent channel 12. Thus, the gas does not have to escape through the adhesive contour 8 or the gel layer 7. This prevents bubble formation.

[0078] The following section describes the production of the pressure sensor assembly.

[0079] First, the enclosure 1, consisting of housing 2 and cover 3, is provided. According to its original design, housing 2 may already have a vent 12 as shown. Alternatively, the vent 12 can be formed as a bore at the designated location.

[0080] The circuit board is then provided with the corresponding components, and the adhesive contour 8 is applied to the underside. The adhesive may, in particular, have the contour shown in Figure 3. P2024, 0771 WO N 4. August 2025

[0081] 18

[0082] The circuit board 4 is then glued to the bottom of the main chamber 22 of the housing 2 by pressing it down. Pressing down widens the adhesive contour so that none of the undercuts described above remain.

[0083] Depending on the type of adhesive, it can be degassed or solidified by heating.

[0084] The circuit board can then be connected to the connecting leads 6 via the wiring connections 5, as necessary. Alternatively, this connection can be established beforehand.

[0085] The top surface of the printed circuit board, including all components and, at least insofar as they are otherwise exposed, the wiring 5 and parts of the connecting leads 6, is then coated with the gel layer 7. The gel layer can subsequently be cured, as described in the introduction. In particular, it is not necessary to achieve a hard state. It is preferred that the gel layer 7 retains a gel-like state. For example, a polymerization process can be initiated. Due to the adhesive contour, the absence of undercuts, and especially the venting channel, no gas migrates through the adhesive contour 8 or through the gel layer 7 during the heating or degassing processes.

[0086] Furthermore, the enclosure can be closed by attaching the cover 3 to the housing 2. P2024, 0771 WO N 4. August 2025

[0087] - 19 -

[0088] Reference character list

[0089] 1 Enclosure

[0090] 2 housings 3 covers

[0091] 4 circuit boards

[0092] 5 Wiring

[0093] 6 connection cable

[0094] 7 Gel layer 8 Adhesive contour

[0095] 9 connector

[0096] 10 contact plugs

[0097] 11 Seal

[0098] 12 Venting duct 21 Pre-chamber

[0099] 22 Main Chamber

[0100] 24 Outdoor opening

Claims

P2024, 0771 WO N August 4, 2025 20 Patent claims 1. System arrangement comprising a printed circuit board which is attached to a carrier by means of a closed adhesive contour, wherein a venting device is formed in the carrier which is designed to drain gases from the space enclosed between the printed circuit board and the carrier by the adhesive contour.

2. System arrangement according to claim 1, wherein the venting device is designed as a venting channel leading through the support.

3. System arrangement according to claim 2, wherein an outer opening of the vent channel leaves the carrier in such a way that a structural component at least partially covers this outer opening.

4. System arrangement according to claim 2 or 3, wherein an outer opening of the vent channel is free from a separately attached closure.

5. System arrangement according to one of claims 2 to 4, wherein an outer opening of the vent channel has a cross-sectional area of ​​at most 2.5 mm² 2 exhibits.

6. System arrangement according to one of claims 1 to 5, wherein a passivation at least partially covers a side of the printed circuit board or components thereon which is not facing the side of the substrate to which the printed circuit board is glued. P2024, 0771 WO N 4. August 2025 21 7. System arrangement according to one of claims 1 to 6, wherein the adhesive contour corresponds to the outer contour of the printed circuit board.

8. System arrangement according to one of claims 1 to 7, wherein no further adhesive bonds are formed within the closed adhesive contour.

9. System arrangement according to one of claims 1 to 8, wherein the adhesive contour extends to the edge of the side of the printed circuit board on which it is arranged, so that there are no undercuts outside the adhesive contour.

10. System arrangement according to any one of claims 1 to 9, wherein the support is an enclosure or part of an enclosure.

11. System arrangement according to claim 10, wherein the enclosure comprises a housing and a lid and the circuit board is glued to a bottom side of the housing.

12. System arrangement according to one of claims 1 to 11, wherein the side of the printed circuit board on which the bonding is carried out is free of sensitive components or completely free of components.

13. System arrangement according to one of claims 1 to 12, wherein neither the space enclosed between the circuit board and the carrier and the adhesive contour, nor the venting device has any function for the operation of the system arrangement.

14. Pressure sensor arrangement which has all the features of the system arrangement according to one or more of claims 1 to 13, wherein a pressure sensor function is implemented. P2024, 0771 WO N 4. August 2025 22 15. Pressure sensor arrangement comprising the combined features of claim 3 and claim 14, wherein the structural component is a connector, a seal or a sensor receptacle.

16. Method for producing a system arrangement comprising Providing a carrier and a printed circuit board, wherein a venting device is formed in the carrier below a point for attaching the printed circuit board, and providing a closed adhesive contour on the printed circuit board or carrier, and adhering the printed circuit board to the carrier by means of the adhesive contour.

17. Method according to claim 16, wherein the venting device is a venting channel passing through the carrier, which is provided in the carrier from the outset or which is carried out as a bore in a process step before, between or after the steps mentioned in claim 16.

18. Method according to claim 16 or 17, wherein a heating step is carried out as a partial step of gluing the printed circuit board onto the substrate or thereafter.

19. Method according to any one of claims 16 to 18, wherein the adhesive contour extends at least after application to the edge of the side of the printed circuit board on which it is arranged, so that no undercuts are present outside the adhesive contour.

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