Micromechanical component with external contact

Abstract

The invention relates to a micromechanical component having an arrangement (10) of external electrical contacts for contacting on a printed circuit board, the component being contactable in a first solder arrangement (11). The core of the invention is that the structural element can be contacted in at least one second welding configuration (12), and an alignment data set (31, 32) for the first welding configuration (11) or the second welding configuration (12) can be configured.

Description

Technical Field

[0001] The invention proceeds from a micromechanical component having an arrangement of external electrical contacts for contacting on a printed circuit board, wherein the component can be contacted in a first soldering configuration. Such components are widely known in the prior art. Background Art

[0002] The MEMS sensor unit, such as BMI270, is used to measure different physical parameters, such as acceleration and rotation speed in three axes. The MEMS sensor unit consists of a housing ( Figure 1 ), one or more MEMS chips as measuring elements and one or more ASICs as sensor data analysis and processing elements are integrated into the housing.

[0003] The ASIC essentially contains a sensor front end in order to convert a physical variable characteristic of the MEMS (e.g. capacitance) first into an analog value and then into a digital value. Downstream of the sensor front end is a compensation unit, the task of which is to compensate for component- and environment-related deviations (e.g. temperature) in the output data of the sensor front end and thus to achieve an accuracy of the output data of the MEMS sensor unit in accordance with the specifications ( Figure 6 ).

[0004] The compensation unit uses a set of calibration parameters which are ascertained during the manufacturing process and stored in a non-volatile memory (NVM) on the ASIC.

[0005] Here, the MEMS sensor unit is contacted in a base and physical variables (such as acceleration and rotation) are applied in order to measure the sensor and determine the alignment values. For example, alignment parameters for correcting deviations (offsets) and sensitivities are determined and stored in the sensor unit.

[0006] Later, for example in a customer application, the MEMS sensor unit is typically soldered to a circuit board in a reflow process ( Figure 5 ). According to this method, mechanical stresses are introduced into the housing, which can lead to deviations in the sensor output signal. Thus, for example, the offset and sensitivity can have different values ​​after welding. This behavior is characterized and quantified within the framework of product development and taken into account during calibration, so that the required accuracy values ​​are present only after welding (so-called pre-calibration). In this case, the calibration parameters are changed based on the knowledge from the characterization so that the sensor achieves the best sensor accuracy only after welding.

[0007] When developing new sensor units, the user should be given the option of choosing between a plurality of different welding configurations during welding. Thus, for example, only the outer 14 welding pads ( Figure 2 ), while in the second configuration the pads further inside are soldered ( Figure 3 ). The user is free to choose to use one or the other configuration.

[0008] As mentioned above, mechanical stresses are introduced into the housing during welding, and the magnitude and type of these stresses also depend on which of the welding configurations is selected. However, this results in the above-mentioned pre-alignment method being applicable only to one of the two configurations. If the other configuration is selected, the sensor is incorrectly or inaccurately aligned. Summary of the invention

[0009] The object of the present invention is to achieve the most precise possible alignment for a plurality of different soldering configurations of a micromechanical component using pre-alignment.

[0010] The invention is based on a micromechanical component having an arrangement of external electrical contacts for contacting on a printed circuit board, wherein the component can be contacted in a first soldering configuration. The core of the invention is that the component can be contacted in at least one second soldering configuration and can be configured with an alignment data set for the first soldering configuration or the second soldering configuration.

[0011] According to the invention, a dedicated calibration data set exists for each welding configuration. Thus, a configuration option for operating the sensor is provided to the user. The user can configure the sensor according to the welding configuration used and can use the corresponding calibration data set in the sensor.

[0012] An advantageous embodiment of the invention provides that the component has an internal memory in which a first adjustment data set for a first welding configuration and / or a second adjustment data set for a second welding configuration are stored in a selectable manner.

[0013] Another advantageous embodiment of the invention provides that the structural element has an internal memory in which a basic adjustment data set is stored as a first adjustment data set for a first welding configuration and in which differences relative to the basic adjustment data set are stored for determining a second adjustment data set for a second welding configuration.

[0014] Another advantageous embodiment of the present invention provides that the structural element has a type-specific or personalized serial number, and the first adjustment data set for the first welding configuration and / or the second adjustment data set for the second welding configuration and / or the difference to the basic adjustment data set are stored in an external database or a host processor in a callable manner in a manner assigned to the serial number.

[0015] An advantageous embodiment of the invention provides that the component is designed for automatic recognition of its welding configuration.

[0016] The advantage of the invention is that it enables products that can be soldered onto the same circuit board in such a way that they can replace already existing products. Thus, in the case of IMUs (sensors for acceleration and rotation speed), 2.5x3mm has been established across manufacturers. 2 Since additional pads are required in new products for new functions, these pads can be placed in the free inner area of ​​the pad layout and can be used for optional functions (see Figure 2 ). This enables users to use the same circuit board for multiple device variants or to continue using existing circuit boards.

[0017] Examples for such optional functions are: a debug interface for an embedded microprocessor, a reset input, and also interfaces for attaching additional sensors, external memory or other peripheral components.

[0018] Another advantage of the invention is that the sensor can be used on inexpensive printed circuit boards. These printed circuit boards are distinguished by the fact that they have only a few (e.g. one or two) wiring planes and that the signals of the internal pads cannot be connected or can only be connected with difficulty because there are no paths for the conductor paths. In this case, the function of the optional internal pads can also be omitted and they can be left empty. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematically, a sensor package with a welding surface in the prior art is shown.

[0020] Figure 2 A sensor package with a soldering surface is schematically shown in a first soldering configuration.

[0021] Figure 3 The sensor package with the welding surface is schematically shown in a second welding configuration.

[0022] Figure 4 The sensor package is schematically shown mounted on a printed circuit board in a first soldering configuration.

[0023] Figure 5 The sensor package mounted on a printed circuit board is schematically shown in a second soldering configuration.

[0024] Figure 6 The design of a MEMS sensor unit according to the prior art is schematically shown, which has alignment data in a non-volatile memory.

[0025] Figure 7 The design of a MEMS sensor unit in a first exemplary embodiment of the invention is schematically shown, which has two alignment data sets in a non-volatile memory. DETAILED DESCRIPTION

[0026] Figure 1 A sensor package with soldering surfaces from the prior art is schematically shown. A leadless package is shown with an arrangement 10 of external electrical contacts for contacting on a printed circuit board.

[0027] Figure 2 A sensor package with a welding surface in a first welding configuration is schematically shown. Figure 1 The underside of the leadless package in FIG. 1 has an arrangement 10 of external electrical contacts, of which peripheral contacts shown in hatched areas are provided as a first soldering arrangement 11 for contacting on a printed circuit board.

[0028] Figure 3 The sensor package with the welding surface in the second welding configuration is schematically shown. Figure 1 The underside of the leadless package in FIG. 1 has an arrangement 10 of external electrical contacts, all of which are shown in hatched areas and are provided as a second soldering configuration 12 for contacting on a printed circuit board.

[0029] Figure 4 The sensor package is schematically shown in a first soldering arrangement 11, mounted on a printed circuit board 50. The printed circuit board can transmit forces to the micromechanical components via peripheral solder contacts of the leadless package, so that the components must be aligned to take the mounting conditions into account.

[0030] Figure 5 The sensor package mounted on a printed circuit board 50 is schematically shown in a second soldering configuration 12. The printed circuit board can transmit forces to the micromechanical structural element via all solder contacts of the leadless package, so that the alignment of the structural element needs to take into account the mounting and Figure 4 Compared to the changed situation.

[0031] Figure 6 The structure of a MEMS sensor unit in the prior art is schematically shown, which has calibration data in a non-volatile memory. The micromechanical structure element has a MEMS sensor unit 100 inside its package, which has a micromechanical sensor element 110. The signal of the sensor element is provided to an ASIC 200 with an electronic signal receiving circuit, a sensor front end 210 and a compensation unit 220. The compensation unit obtains the calibration information from the non-volatile internal memory 40. For this purpose, the calibration data is stored in the internal memory 40. The calibrated sensor signal 60 is output by the MEMS sensor unit 100.

[0032] Figure 7 The design of a MEMS sensor unit in a first exemplary embodiment of the present invention is schematically shown, which has two alignment data sets in a non-volatile memory.

[0033] The MEMS sensor unit is designed in such a way that a plurality of different adjustment data sets can be stored in the non-volatile memory. In this case, different adjustment data sets are assigned to different welding configurations. Figure 6 The compensation unit 220 can be configured with the first or second adjustment data set, which is symbolically indicated by the switch 42.

[0034] The MEMS sensor unit thus offers a configuration option by means of which the soldering configuration used in the application can be selected. This configuration is performed during initialization of the MEMS sensor unit by writing register addresses.

[0035] During initialization of the MEMS sensor unit, for example after the current supply has been applied, an adjustment data set assigned to the selected welding configuration is selected and provided to a compensation unit for compensating the sensor signal.

[0036] The present invention can be implemented in different embodiments.

[0037] In a second exemplary embodiment, the configuration for selecting the alignment data set is implemented by one-time writing into a storage unit in a non-volatile memory in the MEMS sensor unit.

[0038] In a third embodiment, different alignment data sets for a welding configuration are achieved by adding differential values ​​to a base alignment data set, and the differential values ​​are stored in a non-volatile memory.

[0039] In a fourth embodiment, the adjustment data sets or difference values ​​are not stored in the MEMS sensor unit, but in a separate database. Matching difference value sets can be identified in the database based on component-specific, i.e., individual serial numbers and then written into the MEMS sensor unit in the application, for example by accessing a register.

[0040] In a fifth exemplary embodiment, the difference value is characterized in a type-specific manner and is not adjusted in a component-specific manner. Thus, it is possible to work with a fixed difference value, which can also be stored outside of a non-volatile memory, for example in a host processor.

[0041] For example, if it is determined in the characterization that the offset values ​​between a first welding configuration and a second welding configuration always have a fixed deviation Δo with sufficient accuracy, the sensor can be adjusted to the first welding configuration and this deviation Δo can be calculated into the sensor value in the host processor when using the second welding configuration.

[0042] In a sixth embodiment, the soldering configuration is determined automatically by the MEMS sensor unit, for example by performing a contact test on an optional contact pad. In this way, for example, the level of a pad that is equipped with a pull-up in the MEMS sensor unit can be determined. Depending on the soldering configuration, the pad can be grounded externally or open. Depending on the level on the pad when the sensor is activated, a first soldering configuration or a second soldering configuration can be selected.

[0043] Reference numerals list

[0044] 10 Arrangement of external electrical contacts

[0045] 11. First welding configuration

[0046] 12 Second welding configuration

[0047] 20 Internal Memory

[0048] 31 First alignment data set

[0049] 32 Second alignment data set

[0050] 40 Internal Memory

[0051] 42 Switch

[0052] 50 PCB

[0053] 60 Adjusted sensor signal

[0054] 100MEMS sensor units

[0055] 110MEMS sensor element

[0056] 200ASIC

[0057] 210 Sensor front end

[0058] 220 Compensation unit

Claims

1. A micromechanical component having an arrangement (10) of external electrical contacts for contacting on a printed circuit board, wherein: The structural element can be contacted in a first welding configuration (11), It is characterized in that The structural element is capable of being contacted in at least one second welding configuration (12), and An adjustment data set (31, 32) can be provided for the first welding arrangement (11) or the second welding arrangement (12).

2. The micromechanical structure element according to claim 1, characterized in that The component has an internal memory (40) in which a first adjustment data set (31) for the first welding configuration (11) and / or a second adjustment data set (32) for the second welding configuration (12) are stored in a selectable manner.

3. The micromechanical structure element according to claim 1, characterized in that The structural element has an internal memory (40) in which a basic adjustment data set is stored as a first adjustment data set (31) for the first welding configuration (11) and in which difference values ​​relative to the basic adjustment data set are stored for determining a second adjustment data set (32) for the second welding configuration (12).

4. The micromechanical structure element according to claim 1, characterized in that The structural element has a type-specific or individual serial number, and a first adjustment data set (31) for the first welding configuration (11) and / or a second adjustment data set (32) for the second welding configuration (12) and / or differences to a basic adjustment data set are stored in an external database or a host processor in a callable manner in a manner assigned to the serial number.

5. The micromechanical component according to any one of claims 1 to 4, characterized in that The structural element is designed to automatically identify its welding configuration (11, 12).

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