Microsensor device having at least one additional bonding wire in a protective compound

Abstract

The invention relates to a microsensor device (10) for measuring at least one environmental variable in a sensor environment (24), the microsensor device comprising: a carrier element (14); an electronics unit (18) arranged on the carrier element (14); a sensor element (20) having a sensor component (22) for measuring the environmental variable; a plurality of bonding wires (26) electrically connecting the sensor element (20) to the electronics unit (18) and / or the electronics unit (18) to the carrier element (14); and a protective compound (44) which covers the sensor element (20) with respect to the sensor surroundings (24) at least on top in relation to a vertical direction (32) and which surrounds the bonding wires (26) and thus shields the bonding wires from the sensor surroundings (24); wherein at least one additional bonding wire (34, 34.1, 34.2) is arranged entirely within the protective compound (44) and at least partially spans at least one bonding wire (26) of the bonding wires on top in relation to the vertical direction (32).

Description

[0001] Microsensor device with at least one additional bonding wire in a protective compound

[0002] The invention relates to a microsensor device according to the preamble of claim 1.

[0003] State of the art

[0004] DE 102008 012 895 A1 describes a capacitive pressure sensor with a sensor element bonded to a substrate. The sensor element is electrically connected to the substrate via bond wires. A protective gel is arranged on the sensor element and around the bond wires.

[0005] Disclosure of the invention

[0006] According to the present invention, a microsensor device with the features of claim 1 is proposed. This allows the microsensor device to be designed more reliably and with a more compact footprint. Furthermore, interference from the sensor environment, such as changes in the electromagnetic environment caused by the accumulation of liquids instead of air on the protective compound, can be reduced on the bonding wires. The layer thickness of the protective compound above the bonding wires can exhibit less fluctuation.

[0007] The microsensor device may be a microelectromechanical sensor device. The microsensor device may be a pressure sensor and / or microphone. The microsensor device may be a barometric pressure sensor. The microsensor device may be installed in a vehicle, watercraft, aircraft, robot, a mobile, stationary, or movable device, an industrial device, or a consumer end product.

[0008] Spanning or bridging means that the spatial paths of the additional bonding wire and the bonding wire of the bonding wires, projected onto a reference plane having the vertical direction as its normal, have at least one intersection point. At the intersection point, however, the additional bonding wire is spaced apart from the bonding wire with respect to the vertical direction and arranged above the bonding wire. Sectional spanning refers to the intersection point. If, for example, the additional bonding wire runs parallel above the bonding wire and the spatial paths projected onto the reference plane overlap, the additional bonding wire completely spans the bonding wire.

[0009] The vertical direction may be a direction perpendicular to the main extension plane of the support element.

[0010] The ambient variable can be a fluid pressure, in particular an air pressure, of an ambient medium. The ambient medium can be air or a liquid, for example, water.

[0011] The carrier element can be a substrate, for example, an LGA substrate or a ceramic substrate. The carrier element can be made of silicon or glass. The carrier element can accommodate or form a housing that defines a boundary for the protective mass.

[0012] The sensor element can measure the ambient variable capacitively, piezoelectrically, and / or piezoresistively. The sensor component, particularly as a membrane, can be deflectable depending on the ambient variable. The sensor element can provide a measurement signal dependent on the deflection. The protective mass can be arranged above the sensor component in the vertical direction, facing the sensor environment. The sensor element can be attached to the electronics unit and / or the carrier element. The sensor element can be connected to the electronics unit and / or the carrier element in a form-fitting, material-fitting, and / or force-fitting manner. The sensor element can be adhesively bonded to the electronics unit and / or the carrier element.

[0013] The electronics unit can be an ASIC. The electronics unit can provide a sensor signal depending on the state of the sensor element, which in turn depends on the ambient variable. The sensor signal can be dependent on the measurement signal. The electronics unit can include an evaluation unit. The sensor element and the electronics unit can be arranged side by side or one above the other on the carrier element.

[0014] The bond wires can electrically connect the sensor element to the carrier element.

[0015] The protective compound can have a solid-liquid, pasty, or elastically solid consistency. The protective compound can have a consistency different from that of a gas or liquid. The protective compound can be a gel, in particular a silicone gel or fluorosilicone gel. The protective compound can completely fill the volume in the vertical direction between the bonding wires and the additional bonding wire. The protective compound can protect the sensor element, in particular the sensor component, from environmental influences from the sensor environment, for example water, rain, dirt, particles, substances, sand, and / or dust. The sensor element can be shielded from the sensor environment by the protective compound.

[0016] The additional bonding wire can reduce a stray electrical field between the bonding wires. For example, the stray field can be many times higher when liquids, particularly water, are deposited on the protective compound than when no liquid is present. The variability of the stray field can be reduced by the additional bonding wire, particularly in conjunction with the surrounding protective compound. The additional bonding wire can be straight, angled, bent, wavy, and / or curved with respect to the reference plane. The additional bonding wire and the bonding wire are contact-free. The additional bonding wire can be made of the same or different material as the bonding wires. The additional bonding wire can be free of a deliberately applied electrical voltage or a deliberately applied electrical potential. However, the additional bonding wire can have an electrical ground potential.

[0017] The bond wires and the at least one additional bond wire can each be attached to the respective connection component, i.e., the sensor element, the electronics unit, and / or the carrier element, via attachment points. The attachment points of the additional bond wire are spaced apart from the attachment points of the bond wires with respect to the reference plane. At least one attachment point of the additional bond wire can be spaced apart from at least one attachment point of at least one bond wire with respect to the vertical direction or arranged at the same height. The attachment points of the additional bond wire can be arranged at the same height or offset from one another with respect to the vertical direction.

[0018] In a preferred embodiment of the invention, it is advantageous if a maximum layer thickness of the protective compound in the vertical direction is less than or equal to 25 μm, at least in the region of the sensor element, preferably in the region of the sensor component, in particular in the entire region of the sensor component. This can increase the sensitivity of the sensor element to changes in the ambient variable and reduce the interference of the dirt mass on the measurement of the ambient variable.

[0019] A preferred embodiment of the invention is advantageous in which a maximum layer thickness of the protective compound in the vertical direction in the region of the sensor element, preferably in the region of the sensor component, in particular in the entire region of the sensor component, is smaller than a minimum layer thickness in the vertical direction in the region of the bonding wires. This allows the sensitivity of the sensor element to changes in the ambient variable to be achieved while still providing reliable protection for the bonding wires.

[0020] In a specific embodiment of the invention, it is advantageous if the additional bonding wire has an electrical potential that differs from the bonding wires that connect an output voltage of the sensor element to the carrier element or the electronics unit. The additional bonding wire can be grounded. The additional bonding wire and at least one of the bonding wires can have a common electrical ground potential. The electrical ground potential can be the common electrical ground potential of the electronics unit and the sensor element. The additional bonding wire can be electrically connected to the electronics unit.

[0021] In an advantageous embodiment of the invention, the additional bonding wire is attached at least to the carrier element, the sensor element, and / or the electronics unit. The additional bonding wire can have at least two or exactly two spaced-apart attachment points. The additional bonding wire can have more than two attachment points and at least two loops, for example, to increase the mechanical stability of the composite of the additional bonding wire and protective compound.

[0022] In an advantageous embodiment of the invention, the additional bonding wire spans the sensor element at least partially in the vertical direction above it. This allows the sensor element to be additionally protected from environmental influences, such as particle impacts and / or electromagnetic environmental influences. The protective compound can have a cavity above the sensor element, in particular above the sensor component, with respect to the vertical direction. The cavity can be arranged between the sensor element, in particular the sensor component, and the additional bonding wire with respect to the vertical direction.

[0023] A preferred embodiment of the invention is advantageous in which, with respect to a reference plane having the vertical direction as the normal, a direction of travel of the additional bonding wire is angled relative to a direction of travel of at least one of the bonding wires. The angle can be 0°, 45°, or 90°. The angle can take on any value between 0° and 90°. The additional bonding wire can run parallel to at least one of the bonding wires and completely span it. This allows the sensor element, in particular a capacitive one, to be effectively shielded from electromagnetic influences by the bonding wire.

[0024] In a preferred embodiment of the invention, it is advantageous if, within the protective mass, in addition to the additional bonding wire as the first additional bonding wire, at least one further second additional bonding wire is arranged, which at least partially spans at least one of the bonding wires or the bonding wire, which is also spanned above at least partially by the first additional bonding wire, with respect to the vertical direction. The second additional bonding wire can be electrically connected to the sensor element, the electronics unit, and / or the carrier element. The electronics unit can perform a measurement of the medium present in the vertical direction above the protective mass at least via the first and second additional bonding wires.

[0025] The additional bonding wire can be used to detect a change in the nature of the ambient medium. The first and second additional bonding wires can form sensor means for detecting and / or sensing accumulations on the protective compound. For example, a change in capacitance between the first and second additional bonding wires can be detected depending on the deposition or accumulation of a medium, such as a liquid, above the protective compound.

[0026] A preferred embodiment of the invention is advantageous in which the first and second additional bonding wires are arranged at a distance from one another. The first and second additional bonding wires can be arranged at least partially above one another with respect to the vertical direction. The first and second additional bonding wires can be stacked one above the other. The first and second additional bonding wires can be arranged next to one another. The first additional bonding wire can span the second additional bonding wire above the vertical direction, at least partially. The first and second additional bonding wires can extend parallel, at an angle, or offset from one another.

[0027] In a preferred embodiment of the invention, it is advantageous if the first and second additional bonding wires have the same electrical potential. The first and second additional bonding wires can be short-circuited to each other.

[0028] Further advantages and advantageous embodiments of the invention emerge from the description of the figures and the illustrations.

[0029] Character description

[0030] The invention is described in detail below with reference to the figures, in which: Figure 1: A spatial view of a microsensor device in a special

[0031] Embodiment of the invention.

[0032] Figures 2 to 4: A respective cross section of a microsensor device in a further specific embodiment of the invention.

[0033] Figures 5 to 7: A respective plan view of a microsensor device in a further specific embodiment of the invention.

[0034] Figure 1 shows a spatial view of a microsensor device in a specific embodiment of the invention. The microsensor device 10 is designed, for example, as a capacitive pressure sensor 12 and comprises a carrier element 14, in particular a substrate 16, an electronics unit 18 arranged on the carrier element 14, and a sensor element 20 with a deflectable membrane 22 for measuring at least one ambient variable of a sensor environment 24. For example, the ambient variable is a fluid pressure of the sensor environment 24, which deflects the membrane 22. The sensor element 20 is electrically connected to the electronics unit 18 via a plurality of bond wires 26. A respective bond wire 26 of the bond wires comprises a first fastening point 28 on the electronics unit 18 and a second fastening point 30 on the sensor element 20. The two fastening points 38 are spaced apart from one another with respect to a vertical direction 32.

[0035] The bond wires 26 are spanned in sections above with respect to the vertical direction 32 by a first additional bond wire 34.1 and a second additional bond wire 34.2. The fastening points 38 of the first and second additional bond wires 34.1, 34.2 are arranged on the electronics unit 18. The first and second additional bond wires 34.1, 34.2 shield the bond wires 26 from electromagnetic influences from the sensor environment 24. The first and second additional bond wires 34.1, 34.2 extend parallel to one another with respect to a reference plane 40 having the vertical direction 32 as the normal. The spatial paths 42 of the first and second additional bond wires 34.1, 34.2 projected onto the reference plane 40 correspond to parallel lines.

[0036] Figures 2 to 4 show a respective cross-section of a microsensor device in a further specific embodiment of the invention. The microsensor device 10 in Figure 2 comprises bonding wires 26, which are fastened on the one hand to the sensor element 20, which is fastened to the electronics unit 18 via an adhesive 43, and on the other hand to the electronics unit 18. The bonding wires 26 are completely spanned above in the vertical direction 32 by a first additional bonding wire 34.1 and a second additional bonding wire 34.2. The first and second additional bonding wires 34.1, 34.2 are arranged completely within a protective mass 44, which covers the sensor element 20 from the sensor environment 24, at least with respect to the vertical direction 32 above, and which also encloses the bonding wires 26 and shields them from the sensor environment 24.

[0037] The second additional bonding wire 34.2 is arranged above the first additional bonding wire 34.1 with respect to the vertical direction 32. As a result, the bonding wires 26 and the first and second additional bonding wires 34.1, 34.2 are arranged stacked one above the other. An electrical potential of the first and second additional bonding wires 34.1, 34.2 is in particular the same and corresponds to an electrical ground potential also present on at least one bonding wire 26. In addition to the first additional bonding wire 34.1, further first additional bonding wires and / or in addition to the second additional bonding wire 34.2, further second additional bonding wires can be arranged.

[0038] The first and second additional bonding wires 34.1, 34.2 are fastened to the electronics unit 18 and the sensor element 20. The fastening points of a respective bonding wire 26 of the bonding wires are offset from one another in the vertical direction 32. A first fastening point 28 of the bonding wire 26 is arranged on the electronics unit 18, and the other second fastening point 30 assigned to the bonding wire 26 is arranged on the sensor element 20. The fastening points of the first additional bonding wire 34.1 are also offset from one another in the vertical direction 32. A first fastening point 46 of the first additional bonding wire 34.1 is arranged on the electronics unit 18, and the other second fastening point 48 assigned to the first additional bonding wire 34.1 is arranged on the sensor element 20. Likewise, a first fastening point 50 of the second additional bonding wire 34.2 is arranged on the electronics unit 18, and the second additional bonding wire 34.2 assigned other second fastening point 52 is arranged on the sensor element 20.

[0039] In the reference plane 40, the first fastening point 28 of the bonding wire 26, the first fastening point 46 of the first additional bonding wire 34.1, and the first fastening point 50 of the second additional bonding wire 34.2 are arranged at a distance from one another. Furthermore, the second fastening point 30 of the bonding wire 26, the second fastening point 48 of the first additional bonding wire 34.1, and the second fastening point 52 of the second additional bonding wire 34.2 are arranged at a distance from one another in the reference plane 40.

[0040] A maximum layer thickness 54 of the protective mass 44 in the vertical direction 32 is smaller across the entire region of the membrane 22 than a minimum layer thickness 56 in the vertical direction 32 in the region of the bonding wires 26. The first and second additional bonding wires 34.1, 34.2 increase a minimum layer thickness 56 above the bonding wires 26. This reduces the influence of an ambient medium above the protective mass 44 on a stray electric field between the bonding wires 26. The maximum layer thickness 54 of the protective mass 44 across the entire region of the membrane 22 is preferably less than or equal to 25 pm.

[0041] The microsensor device 10 in Figure 3 comprises a first additional bonding wire 34.1, which, in addition to the bonding wires 26, also spans the sensor element 20 above in the vertical direction 32. This allows the sensor element 20 to be additionally protected from environmental influences, for example, particle impacts, and / or electromagnetic environmental influences. With respect to the vertical direction 32, a cavity 58 of the protective compound 44 is formed above the sensor element 20, in particular, and is connected to the sensor environment 24. In the vertical direction 32, this cavity 58 is dimensioned such that a thermal expansion difference between the electronics unit 18 and the sensor element 20, and optionally the adhesive 43, compared to the first additional bonding wire 34.1 and the protective compound 44 does not lead to contact between the top and bottom of the cavity 58 over an entire operating temperature range, for example, from -40 to 200°C. The first additional bonding wire 34.1 forms, together with the protective mass 44 surrounding it, a protection for the membrane 22, for example, against particle impacts and / or particle contamination.

[0042] The microsensor device 10 in Figure 4 comprises a first additional bonding wire 34.1, which has a total of three attachment points 38 and two loops. This allows the layer thickness above the sensor element 20 and the bonding wires 26 to differ from one another and be adapted to the requirements. Alternatively, the first additional bonding wire 34.1 can be split into two parts.

[0043] Figures 5 to 7 each show a top view of a microsensor device in a further specific embodiment of the invention. The microsensor device 10 in Figure 5 comprises the sensor element 20 with the membrane 22. The sensor element 20 is arranged on the electronics unit 18 and electrically connected to the electronics unit 18 via parallel bonding wires 26. Some of the bonding wires 26 are spanned above in sections by several additional bonding wires 34. With respect to the reference plane 40, a direction of travel 60 of a first additional bonding wire 34.1 is angled by an angle 64 relative to a direction of travel 62 of at least one bonding wire 26 of the bonding wires. A second additional bonding wire 34.2 of the additional bonding wires is arranged parallel to the first additional bonding wire 34.1.

[0044] Compared to the microsensor device of Figure 5, in the microsensor device 10 of Figure 6, the additional bonding wires 34 are curved and / or bent with respect to the plane, and some of the bonding wires 26 extend above, spanning them in sections. The microsensor device 10 in Figure 7 comprises the sensor element 20 with the membrane 22, the electronics unit 18, and the carrier element 14. The bonding wires 26 connect the sensor element 20 to the electronics unit 18. A first and second additional bonding wire 34.1, 34.2 are attached to the carrier element 14, extending at an angle of 90° to the bonding wires 26, and spanning all of the bonding wires 26 in sections above.

Claims

Patent claims 1. A microsensor device (10) for measuring at least one environmental variable of a sensor environment (24), comprising a carrier element (14), an electronics unit (18) arranged on the carrier element (14), a sensor element (20) with a sensor component (22) for measuring the environmental variable, a plurality of bonding wires (26) electrically connecting the sensor element (20) to the electronics unit (18) and / or the electronics unit (18) to the carrier element (14), a protective mass (44) which covers the sensor element (20) with respect to the sensor environment (24) at least with respect to a vertical direction (32) above and which encloses the bonding wires (26) and thus shields them from the sensor environment (24), characterized in that at least one additional bonding wire (34, 34.1, 34.2) is arranged completely within the protective mass (44), which additional bonding wire (34, 34.1, 34.2) connects at least one bonding wire (26) of the bonding wires with respect to the vertical direction (32) above at least partially spanned.

2. Microsensor device (10) according to claim 1, characterized in that a maximum layer thickness (54) of the protective mass (44) in the vertical direction (32) is less than or equal to 25 pm at least in the region of the sensor component (22).

3. Microsensor device (10) according to claim 1 or 2, characterized in that a maximum layer thickness (54) of the protective mass (44) in the vertical direction (32) in the region of the sensor component (22) is smaller than a minimum layer thickness (56) in the vertical direction (32) in the region of the bonding wires (26).

4. Microsensor device (10) according to one of the preceding claims, characterized in that the additional bonding wire (34, 34.1, 34.2) has an electrical potential which differs from the bonding wires (26) which connect an output voltage of the sensor element (20) to the carrier element (14) or the electronics unit (18).

5. Microsensor device (10) according to one of the preceding claims, characterized in that the additional bonding wire (34, 34.1, 34.2) and the bonding wire (26) have a common electrical ground potential.

6. Microsensor device (10) according to one of the preceding claims, characterized in that the additional bonding wire (34, 34.1, 34.2) is attached at least to the carrier element (14), the sensor element (20) and / or the electronics unit (18).

7. Microsensor device (10) according to one of the preceding claims, characterized in that the additional bonding wire (34, 34.1, 34.2) spans the sensor element (20) in the vertical direction (32) above at least in sections.

8. Microsensor device (10) according to one of the preceding claims, characterized in that in each case with respect to a reference plane (40) having the vertical direction (32) as a normal, a direction of extension of the additional bonding wire (34, 34.1, 34.2) is angled by an angle (64) with respect to a direction of extension of at least one of the bonding wires (26).

9. Microsensor device (10) according to one of the preceding claims, characterized in that within the protective mass (44), in addition to the additional bonding wire as the first additional bonding wire (34.1), at least one further second additional bonding wire (34.2) is arranged, which spans at least one of the bonding wires (26) above with respect to the vertical direction (32) at least in sections.

10. Microsensor device (10) according to claim 9, characterized in that the first and second additional bonding wires (34, 34.1, 34.2) are arranged at a distance from one another.

11. Microsensor device (10) according to claim 9 or 10, characterized in that the first and second additional bonding wires (34, 34.1, 34.2) have the same electrical potential.

12. Microsensor device (10) according to one of the preceding claims, characterized in that the additional bonding wire (34, 34.1, 34.2) is used to detect a change in the nature of the ambient medium.

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