DE102020209542A1 - Sensor for detecting a physical variable - Google Patents

Abstract

The invention relates to a sensor for detecting a physical variable, in particular moisture. The sensor has a molded body and at least two electrodes, the electrodes being connected to the molded body and being arranged in a recess of the molded body. According to the invention, the molded body has at least one or only one recess for each electrode. The recesses are preferably arranged at a distance from one another.

Description

State of the art

The invention relates to a sensor for detecting a physical variable, in particular moisture. The sensor has a molded body and at least two electrodes, the electrodes being connected to the molded body and being arranged in a recess of the molded body.

From the DE 11 2013 006 033 T5 there is known a thermal sensor formed of a mold resin with an opening and a measuring unit, the measuring unit being exposed to the outside through the opening.

Disclosure of Invention

According to the invention, the molded body has at least one or only one recess for each electrode. The recesses are preferably arranged at a distance from one another. Advantageously, no electrically conductive foreign body, for example a metal chip, can bridge the electrodes insofar as the electrodes are arranged in recesses that are separate from one another and lead each electrode to the outside.

The molded body is preferably a plastic body. More preferably, the molar body has particle-filled epoxy resin. The mold body can thus be provided in a cost-effective manner.

In a preferred embodiment, the electrode is designed as an electrically conductive layer. The electrode is preferably accessible through at least two recesses for the physical quantity, in particular for moisture. The electrodes, or electrode sections, which can each detect the physical variable to an exterior space outside of the sensor through their own opening in the mold body, can be at the same electrical potential. Detection reliability can advantageously be formed in this way, for example in the event that an opening is blocked, the physical quantity can still be detected through the further opening.

The electrode is preferably formed by an electrically conductive layer that is connected to a circuit carrier. The circuit carrier is, for example, a fiber-reinforced printed circuit board or a ceramic circuit carrier, for example an LTCC circuit carrier (LTCC=low-temperature co-fired ceramics) or an HTCC circuit carrier (HTCC=high-temperature co-fired ceramics).

In an advantageous variant of the sensor, the electrode is arranged in a recess in a circuit carrier. The recess in the circuit carrier preferably adjoins the recess in the molded body. In this way, the electrode can be enclosed in the circuit carrier, in particular formed as an internal electrically conductive layer. The electrically conductive layer is preferably connected to the circuit carrier. As a result, the electrode can advantageously be formed as a conductor track on the circuit carrier.

In a preferred embodiment, the electrode is arranged on a base or floor of the recess, the depth of the recess being between 50 micrometers and 10,000 micrometers. Advantageously, the sensor can thus be produced in a cost-effective manner using two tool halves by means of a molding process, with a projection region for the respective recess being formed onto one tool half to produce the recess.

In a preferred embodiment of the sensor, the diameter of the recess is between 100 micrometers and 500 micrometers. Advantageously, no foreign body that is larger than the diameter of the recess can penetrate into the recess.

In a preferred embodiment, the recess is cylindrical. The recess can thus advantageously be produced in a solid molded body by drilling, in particular mechanical drilling or laser drilling.

In a preferred embodiment, the recess tapers towards an opening in the molded body. The opening thus advantageously has a smaller diameter than a diameter of the electrode surface which is accessible through the opening.

In another advantageous embodiment, the recess tapers towards the electrode. The recess is formed, for example, in the shape of a truncated cone. Advantageously, the sensor, in particular the mold housing, can thus be easily removed from the mold during molding.

In a preferred embodiment, the recesses that lead to the same electrode are offset from one another, preferably offset from one another in relation to a straight line. Advantageously, pairs of recesses can be formed in this way, which are arranged offset from one another, with the recesses of a pair of recesses leading to electrodes that are different from one another.

The sensor is preferably designed to detect moisture surrounding the sensor. The sensor is preferably designed to detect an impedance formed between the electrodes, in particular a capacitance formed between the electrodes and/or an ohmic resistance formed between the electrodes.

The invention also relates to a method for producing a recess in an electronic component with a molded body. In the method, a fluid-soluble shaped body is applied to a substrate with an electrically conductive layer in such a way that at least part of the electrically conductive layer is covered by the shaped body. The shaped body is, for example, glued or printed onto the substrate. The fluid for dissolving the shaped body is, for example, a liquid or a gas.

In the method, in a further step, the substrate is preferably encapsulated together with the shaped body with molding compound—in particular by means of transfer molding, hard-cover dispensing, conformal coating, injection molding or potting, so that the shaped body is accessible from the outside. A surface area of the molded body is preferably flush with a surface area of the molded body. In a further step, the molded body is detached or washed out of the molded body by means of a solvent fluid, so that a recess is produced in the molded body at its location, which extends as far as the electrode.

The shaped body can be produced, for example, by means of a water-soluble or alcohol-soluble plastic, a resin, for example by means of shellac. In a preferred embodiment, the shaped body is formed from HIPS (HIPS=high-impact polystyrene). In another embodiment, the shaped body can be formed from starch, in particular corn starch.

In a preferred embodiment, the shaped body is produced on the substrate by means of an additive manufacturing process, in particular 3D printing. In another embodiment, the shaped body can be applied, preferably glued, to the substrate, in particular by means of an automatic placement machine.

The shaped body, in particular HIPS shaped body, can be washed out of the recess, for example by means of a terpentene-containing fluid, in particular limonene-containing fluid, or by means of PVA fluid (PVA=polyvinyl alcohol), especially after remoulding. A fine recess structure can advantageously be produced in the mold body in this way.

• 1 zeigt ein Ausführungsbeispiel für einen Sensor mit Elektroden zum Erfassen von Feuchtigkeit, die in ein Moldgehäuse des Sensors wenigstens teilweise eingebettet sind und durch eine Öffnung in dem Moldgehäuse eine den Sensor umgebende Feuchtigkeit erfassen können;
• 2 zeigt den in 1 gezeigten Sensor in einer Schnittdarstellung;
• 3 zeigt ein Ausführungsbeispiel für einen Sensor zu Erfassen von Feuchtigkeit, der in das Moldgehäuse eingebettete Elektroden aufweist, wobei Öffnungen bildende Ausnehmungen in dem Moldgehäuse gebildet sind, die jeweils zu der Elektrode führen und wobei die Öffnungen in einer ebenen Erstreckung der Elektrode zueinander versetzt, insbesondere im Zick-Zack angeordnet sind.

The invention is now described below with reference to figures and further exemplary embodiments. Further advantageous embodiment variants result from a combination of the features described in the figures and in the dependent claims.

• 1 shows an exemplary embodiment of a sensor with electrodes for detecting moisture, which are at least partially embedded in a molded housing of the sensor and can detect moisture surrounding the sensor through an opening in the molded housing;
• 2 shows the in 1 sensor shown in a sectional view;
• 3 shows an exemplary embodiment of a sensor for detecting moisture, which has electrodes embedded in the mold housing, with openings forming recesses being formed in the mold housing, which each lead to the electrode and with the openings being offset from one another in a planar extent of the electrode, in particular in are arranged zigzag.

1 shows - schematically - an embodiment of a sensor 1. In this embodiment, the sensor 1 is designed to detect the moisture surrounding the sensor. The sensor 1 has a processing unit 2, in particular a microcontroller, a microprocessor, an ASIC (ASIC=Application Specific Integrated Circuit), or a system-in-package. The sensor 1 also has two electrodes for detecting moisture, namely an electrode 3 and an electrode 4. In this exemplary embodiment, the electrodes 3 and 4 are arranged at a distance from one another. The sensor 1 also has a molded housing 5, previously also called a molded body, which is formed in particular by a plastic housing.

The electrodes 3 and 4 are embedded in the mold housing 5 together with the processing unit 2 . The electrodes 3 and 4 are each formed by an electrically conductive layer, the electrically conductive layer being arranged on a circuit carrier 16 and being connected to the circuit carrier 16 .

The electrodes 3 and 4 are each accessible from the outside through recesses in the mold housing 5 and can thus detect moisture outside of the mold housing 5 . The sensor 1 is an impedance sensor, for example, which can detect an impedance formed between the electrodes 3 and 4, in particular a capacitance and/or an ohmic resistance. The recesses form an opening in the mold housing 5 through which the electrodes 3 and 4 of are accessible outside. The electrode 3 is accessible from the outside through three recesses 6 , 7 and 8 which are spaced apart from one another along a straight line 12 . The electrode 4 is accessible from the outside through three recesses 9 , 10 and 11 , each spaced apart from one another along a straight line 13 .

The straight lines 12 and 13 are spaced apart from one another by a distance 14--in particular in a planar extension of the circuit carrier 16.

The recesses leading to the first electrode 3 are thus arranged along a row spaced by the same distance 14 from the row of recesses formed by the recesses 9, 10 and 11 leading to the further electrode 4.

The processing unit 2 is connected to the electrodes 3 and 4 on the input side. The processing unit 2 is designed to detect the moisture detected by the electrodes through the recesses outside of the sensor 1, in particular capacitively and/or by means of an ohmic resistance measurement, and to generate a sensor signal that represents the detected physical quantity, in this exemplary embodiment the moisture. The sensor 1 also has electrical connections, of which a connection 15 is designated as an example. The sensor 1 can provide the sensor signal, in particular the moisture signal, for example at the connection 15 .

The sensor 1 can thus detect the moisture surrounding the sensor 1, in particular atmospheric moisture, or liquid, through six recesses through the mold housing 5, with each of the recesses leading to one of the electrodes.

2 shows the in 1 already shown sensor 1 in a sectional view. The electrodes 3 and 4 are each formed as an electrically conductive layer on the circuit carrier 16 . The circuit carrier 16 is formed, for example, by a printed circuit board. 2 12 shows the recesses 8 and 11, which are each spaced apart from one another by means of the distance 14, and wherein each of the recesses 8 and 11 lead to mutually different electrodes, namely the electrodes 3 and the electrode 4, respectively.

In this exemplary embodiment, the recesses 8 and 11 are each designed in the shape of a truncated cone, with the recesses each being designed to taper away from the electrode. Advantageously, the moisture-sensing electrode surface of the electrode 3 or of the electrode 4 can be made larger than the opening in the mold housing 5 through which the electrode is accessible from the outside.

The recesses 8 and 11 can be produced by a method in which the circuit carrier 16, in particular the electrode 3 and/or 4, is provided with a 2 Shaped body 17, indicated by dashed lines, is applied, for example by means of an additive manufacturing process. In a further step, the circuit carrier can be overmolded with molding compound. The molded body 17 can be removed from the molded body in a further step, in particular washed out or melted out. Advantageously, the recess can thus have a cone that tapers outwards. The cone thus forms an undercut that could not be produced using a two-part injection molding tool.

In another embodiment, the molded housing 5 with the recesses 8 and 11 widened inwards towards the electrodes can be produced by means of an additive manufacturing process, for example 3D printing. In this embodiment, the molded body is formed from polylactate, for example.

3 shows an exemplary embodiment of a sensor 20. The sensor 20 has a molded housing 21, in particular a plastic housing, for example an epoxy resin housing. The sensor 20 also has a processing unit 22 which is formed, for example, by an ASIC, a microcontroller or a microprocessor. The processing unit 22 is connected on the input side to two electrodes 23 and 24 which are spaced apart from one another. The electrodes 23 and 24 are each formed by an electrically conductive layer. The processing unit 22 and the electrodes 23 and 24 can, for example, be arranged together on a circuit carrier. The processing unit 22 and the electrodes 23 and 24 are embedded in the mold case 21, respectively. The electrodes 23 and 24 are thus spaced from an outer surface of the mold housing 21 .

The processing unit 22 is designed, for example, to generate a test signal for detecting the physical variable and to send it to the electrodes and to detect the physical variable as a function of the test signal. In this way, a digital connection of the microcontroller can advantageously be connected directly to the electrodes. Such a test arrangement is, for example, in DE 10 2017 222 845 A1 Or applicant described.

For each of the electrodes 23 and 24 , the mold housing 21 has at least two, in this exemplary embodiment four, recesses through which the electrodes are accessible from the outside and can thus detect moisture outside of the mold housing 21 .

The recesses, which each lead to the same electrode, are in this embodiment along a longitudinal extension 31 - unlike in 1 - arranged offset to each other.

The recesses leading to the same electrode are in this way offset to one another along the longitudinal extent 31, in particular arranged in a zigzag pattern. In this exemplary embodiment, a recess 26 leads to the electrode 24, and a recess 25 opposite this leads to the electrode 23.

A further recess 28 which leads to the electrode 24 and is spaced apart from the electrode 26 along the longitudinal extent 31 is arranged opposite a recess 27 , the recess 27 leading to the further electrode 23 .

The recesses 28 and 27 which face each other are spaced apart by a distance 30 from each other. The recesses 26 and 25, which face each other, are spaced apart from each other by a distance 29. FIG. The distances 29 and 30 are the same in this embodiment. Recesses spaced apart from one another along the longitudinal extent 31 leading to the same electrode each face a corresponding recess leading to the further electrode, with opposite recesses leading to different electrodes being equally spaced from one another. Advantageously, such a zigzag arrangement of the recesses can provide detection reliability if some of the recesses are clogged, for example due to dirt. Blockages that act on the recesses arranged along the geometric line along a geometric line can therefore not block all of the recesses that lead to the same electrode.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 112013006033 T5 [0002]
• DE 102017222845 A1 [0033]

Claims (11)

Sensor (1, 20) for detecting moisture, the sensor (1, 20) having a molded body (5, 21) and at least two electrodes (3, 4, 23, 24) which are connected to the molded body (5, 21) connected and in a recess (6, 7, 8, 9, 10, 11, 25, 26, 27, 28) of the molded body (5, 21) are arranged, characterized in that the molded body (5, 21) for each electrode (3, 4, 23, 24) has at least or only one recess (6, 7, 8, 9, 10, 11, 25, 26, 27, 28), the recesses (6, 7, 8, 9, 10 , 11, 25, 26, 27, 28) spaced (13) from each other. sensor after claim 1 , characterized in that the electrode (3, 4, 23, 24) is designed as an electrically conductive layer, the electrode (3, 4, 23, 24) being accessible to moisture from the outside through at least two recesses. sensor after claim 1 or 2 , characterized in that the electrode (3, 4, 23, 24) is arranged in a recess (6, 7, 8, 9, 10, 11, 25, 26, 27, 28) of a circuit carrier (16). Sensor according to one of the preceding claims, characterized in that the electrode (3, 4, 23, 24) is arranged on a base of the recess (6, 7, 8, 9, 10, 11, 25, 26, 27, 28). and a depth of the recess (6, 7, 8, 9, 10, 11, 25, 26, 27, 28) is between 50 microns and 10,000 microns. Sensor (1, 20) according to one of the preceding claims, characterized in that a diameter of the recess (6, 7, 8, 9, 10, 11, 25, 26, 27, 28) is between 100 micrometers and 500 micrometers. Sensor (1, 20) according to one of the preceding claims, characterized in that the recess (6, 7, 8, 9, 10, 11, 25, 26, 27, 28) is cylindrical. Sensor (1, 20) according to any one of the preceding Claims 1 until 5 , characterized in that the recess (6, 7, 8, 9, 10, 11, 25, 26, 27, 28) to an opening in the mold body (5, 21) is tapered. Sensor (1, 20) according to one of the preceding claims, characterized in that the recesses (6, 7, 8, 9, 10, 11, 25, 26, 27, 28) leading to different electrodes (3, 4, 23, 24) have the same distance (29, 30) to each other. Sensor (1, 20) according to one of the preceding claims, characterized in that the recesses (6, 7, 8, 9, 10, 11, 25, 26, 27, 28) leading to the same electrode (3, 4, 23, 24) lead to each other are offset. Method for producing a recess in an electronic component (1, 20) with a molded body (5, 21), in which a fluid-soluble shaped body (17) is applied to a substrate (16) with an electrically conductive layer (3, 4, 23, 24) in such a way that at least part of the electrically conductive layer (3, 4, 23, 24) is of the shaped body (17) is covered, and the substrate (16) together with the shaped body (17) is molded around with molding compound (5, 21), so that the shaped body (17) is accessible from the outside, and the molded body (17) is detached or washed out of the molded body, in particular by means of a solvent fluid, so that a recess (8, 11) is produced in the molded body (5, 21) at its location, which extends as far as the electrode (3, 4, 23, 24) is enough. procedure after claim 10 , characterized in that the molded body is formed from high-impact polystyrene.

Images