Micromechanical component with external contact

Abstract

The invention relates to a micromechanical component with an arrangement of external electrical contacts (10) for contacting a printed circuit board, wherein the component can be contacted in a first soldering configuration (11). The core of the invention consists in the fact that the component can be contacted in at least one second soldering configuration (12), and a matching data set (31, 32) is configurable for the first soldering configuration or the second soldering configuration.

Description

State of the art

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

[0002] MEMS sensor units such as the BMI270 are used to measure various physical quantities, such as acceleration and angular rate in three axes. They consist of a housing ( Fig. 1), in which one or more MEMS chips are integrated as measuring elements and one or more ASICs as sensor data evaluation elements.

[0003] The ASICs contain, among other things, a sensor front end to convert the MEMS-characteristic physical quantities (e.g., capacitance) first into analog and then digital values. A compensation unit is located downstream of the sensor front end, whose task is to compensate for component- and environment-dependent deviations (e.g., temperature) of the sensor front end's output data and thus achieve the accuracy of the MEMS sensor unit's output data according to the specification ( Fig. 6).

[0004] This compensation unit uses a set of adjustment parameters that are determined during the manufacturing process and stored in a non-volatile memory (NVM) on the ASIC.

[0005] The MEMS sensor unit is contacted in a socket, and physical variables (such as acceleration and rotation) are applied to measure the sensor and determine calibration values. For example, calibration parameters for correcting offset and sensitivity are determined and stored in the sensor unit.

[0006] The MEMS sensor unit is later soldered onto a circuit board, e.g. in the customer application, usually using the reflow process ( Fig. 5). The process involves mechanical stresses being introduced into the housing, which can lead to deviations in the sensor output signals. For example, offset and sensitivity may exhibit different values ​​after soldering. This behavior is characterized and quantified during product development and taken into account during calibration, so that the required sensor accuracy values ​​are only available after soldering (so-called lead calibration). The calibration parameters are modified according to the findings from characterization so that the sensor only achieves optimal sensor accuracy after soldering.

[0007] When developing a new sensor unit, the user should be given the option of choosing between several different soldering configurations. For example, in a first configuration, only the outer 14 pads can be soldered ( Fig. 2), while in a second configuration 6 pads further inside are soldered ( Fig. 3). The user has the freedom to choose whether to use one or the other configuration.

[0008] As described above, soldering imposes mechanical stresses on the package, and the magnitude and type of these stresses also depend on the soldering configuration chosen. However, this means that the lead adjustment procedure described above can only be valid for one of the two configurations. If the other soldering configuration is selected, the sensor will be incorrectly or inaccurately adjusted. Object of the invention

[0009] The object of the invention is to enable the most accurate adjustment possible for several different soldering configurations of a micromechanical component using the lead adjustment. Core and advantages of the invention

[0010] The invention is based on a micromechanical component with an arrangement of external electrical contacts for contacting 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 a calibration data set can be configured for the first soldering configuration or the second soldering configuration. According to the invention, there is a separate set of calibration parameters for each soldering configuration. This provides the user with a configuration option for the operation of the sensor. The user can configure the sensor according to the used soldering configuration, and the corresponding set of calibration parameters can be applied in the sensor.

[0011] An advantageous embodiment of the invention provides that the component has an internal memory in which a first adjustment data set for the first soldering configuration or also a second adjustment data set for the second soldering configuration is selectably stored.

[0012] Another advantageous embodiment of the invention provides that the component has an internal memory in which a basic adjustment data set is stored as a first adjustment data set for the first soldering configuration and difference values, related to the basic adjustment data set, for determining a second adjustment data set for the second soldering configuration are stored.

[0013] Another advantageous embodiment of the invention provides that the component has a type-specific or individual serial number and, associated with this serial number, a first adjustment data set for the first soldering configuration and / or a second adjustment data set for the second soldering configuration or also a difference value to a basic adjustment data set is stored in an external database or a host processor in a retrievable manner.

[0014] An advantageous embodiment of the invention provides that the component is designed to automatically detect its soldering configuration.

[0015] The advantage of the invention is that it enables products that can be interchangeably soldered onto the same circuit board as existing products. For example, the housing size of the IMUs (acceleration and angular rate sensors) has been reduced to 2.5×3 mm. 2with 14 pads across manufacturers. Since new products require additional pads for new functions, these pads can be placed in the free inner area of ​​the pad layout and used for optional functions (see Fig. 2). This allows the user to use the same board for multiple device variants or to continue using an existing board.

[0016] Examples of such optional functions are debug interfaces for embedded microprocessors, reset input, and interfaces for connecting additional sensors, external memory, or other peripheral components.

[0017] A further advantage of the invention is that it enables the application of the sensors on inexpensive circuit boards. These are characterized by having only a few (for example, one or two) wiring levels, and the signals from the inner pads cannot be connected or are difficult to connect due to the lack of a path for the conductor tracks. In this case, the functions of the optional inner pads can be dispensed with and left open. drawing Fig. Figure 1 shows a schematic diagram of a sensor packaging with soldering pads in the prior art. Fig. 2 shows schematically a sensor packaging with soldering pads in a first soldering configuration. Fig. 3 schematically shows a sensor package with soldering pads in a second soldering configuration. Fig. Figure 4 shows schematically the sensor packaging in the first soldering configuration mounted on a circuit board. Fig. Figure 5 shows schematically the sensor packaging in the second soldering configuration mounted on a circuit board. Fig. 6 shows schematically the structure of a MEMS sensor unit with calibration data in a non-volatile memory in the prior art. Fig. 7 schematically shows the structure of a MEMS sensor unit with two sets of calibration data in a non-volatile memory in a first embodiment of the invention. Description

[0018] Fig. Figure 1 schematically shows a prior art sensor package with solder pads. It depicts a leadless package with an array of external electrical contacts 10 for contacting a printed circuit board.

[0019] Fig. Figure 2 shows a schematic diagram of a sensor package with solder pads in a first soldering configuration. The bottom of the leadless package is shown. Fig. 1 with the arrangement of external electrical contacts 10, of which the hatched peripheral contacts are provided as the first soldering configuration 11 for contacting a printed circuit board.

[0020] Fig. Figure 3 shows a schematic of a sensor package with solder pads in a second soldering configuration. The bottom of the leadless package is shown. Fig. 1 with the arrangement of external electrical contacts 10, of which all the hatched contacts are provided as a second soldering configuration 12 for contacting a printed circuit board.

[0021] Fig. Figure 4 schematically shows the sensor package in the first soldering configuration 11 mounted on a printed circuit board 50. The printed circuit board can transmit forces to the micromechanical component via the peripheral solder contacts of the leadless package, which is why calibration of the component must take the assembly conditions into account.

[0022] Fig. Figure 5 schematically shows the sensor package in the second soldering configuration 12 mounted on a printed circuit board 50. The printed circuit board can transmit forces to the micromechanical component via all solder contacts of the leadless package, which is why an adjustment of the component can reduce the Fig. 4 changed assembly conditions must be taken into account.

[0023] Fig. Figure 6 schematically shows the structure of a MEMS sensor unit with calibration data stored in a non-volatile memory according to the prior art. A micromechanical component has a MEMS sensor unit 100 with a micromechanical sensor element 110 inside its packaging. The signals from the sensor element are fed to an ASIC 200 with an electronic signal input circuit, the sensor front end 210, and a compensation unit 220. The compensation unit receives calibration information from a non-volatile internal memory 40. Calibration data is stored for this purpose in the internal memory 40. Calibrated sensor signals 60 are output by the MEMS sensor unit 100.

[0024] Fig. Figure 7 schematically shows the structure of a MEMS sensor unit with two sets of calibration data in a non-volatile memory in a first embodiment of the invention. The MEMS sensor unit is designed such that several different sets of calibration data can be stored in the non-volatile memory. The different sets of calibration data are assigned to the different soldering configurations. In contrast to the micromechanical component in Fig. 6, a first calibration data set 31 for the first soldering configuration and a second calibration data set 32 ​​for the second soldering configuration are selectively stored in the internal memory 40. The compensation unit 220 can be configured with the first or second calibration data set, which is symbolized by the switch 42.

[0025] The MEMS sensor unit therefore provides a configuration option that allows the application to select the soldering configuration used. This configuration is performed during initialization of the MEMS sensor unit by writing a register address.

[0026] When the MEMS sensor unit is initialized, for example after the power supply is applied, the calibration data set assigned to the selected soldering configuration is selected and provided to the compensation unit for compensating the sensor signals.

[0027] The invention can be realized in various embodiments.

[0028] In a second embodiment, the configuration for selecting the calibration data set is performed by writing a memory cell in the non-volatile memory in the MEMS sensor unit once.

[0029] In a third embodiment, different adjustment data sets for the soldering configurations are realized by adding difference values ​​to a basic adjustment data set, and the difference values ​​are stored in the non-volatile memory.

[0030] In a fourth embodiment, the calibration data sets or difference values ​​are not stored in the MEMS sensor unit, but in a separate database. The matching set of difference values ​​can be identified in the database using a part-specific, i.e., individual serial number and then written to the MEMS sensor unit in the application, for example, through register access.

[0031] In a fifth embodiment, the difference values ​​are characterized on a type-specific basis and not adjusted for a part-specific basis. This allows working with fixed difference values ​​that can also be stored outside of the non-volatile memory, for example, in a host processor. For example, if it is determined during characterization that an offset value between the first soldering configuration and the second soldering configuration always has a fixed offset of Δo with sufficient accuracy, the sensor can be adjusted to the first soldering configuration, and when the second soldering configuration is used, the offset Δo can be added to the sensor values ​​in the host processor.

[0032] In a sixth embodiment, the MEMS sensor unit automatically determines the soldering configuration, for example, by performing a contact test on the optional contact pads. For example, the level of a pad equipped with a pull-up in the MEMS sensor unit can be determined. Depending on the soldering configuration, this pad can be externally connected to ground or open. Depending on the level at the pad during sensor startup, the first soldering configuration or the second soldering configuration can be selected. List of reference symbols 10 Arrangement of external electrical contacts 11 first soldering configuration 12 second soldering configuration 20 internal memory 31 first comparison data set 32 second comparison data set 40 internal memory 42 switches 50 circuit boards 60 calibrated sensor signal 100 MEMS sensor unit 110 MEMS sensor element 200 ASIC 210 Sensor Frontend 220 compensation unit

Claims

[1] Micromechanical component with an arrangement of external electrical contacts (10) for contacting a printed circuit board, wherein the component can be contacted in a first soldering configuration (11), characterized by that the component can be contacted in at least one second soldering configuration (12), and a calibration data set (31, 32) can be configured for the first soldering configuration or the second soldering configuration. [2] Micromechanical component according to claim 1, characterized by that the component has an internal memory (40) in which a first adjustment data set (31) for the first soldering configuration (11) and / or a second adjustment data set (32) for the second soldering configuration (12) is selectably stored. [3] Micromechanical component according to claim 1, characterized bythat the component has an internal memory (40) in which a basic adjustment data set is stored as a first adjustment data set (31) for the first soldering configuration (11) and difference values, related to the basic adjustment data set, for determining a second adjustment data set (32) for the second soldering configuration (12). [4] Micromechanical component according to claim 1, characterized by that the component has a type-specific or individual serial number and, associated with this serial number, a first adjustment data set (31) for the first soldering configuration (11) and / or a second adjustment data set (32) for the second soldering configuration (12) and / or a difference value to a basic adjustment data set is stored in an external database or a host processor so that it can be retrieved. [5] Micromechanical component according to one of claims 1 to 4, characterized bythat the component is designed for automatic detection of its soldering configuration (11, 12).

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