Patent Application
20090056446
The present invention generally relates to sensor packaging and, more particularly, to a multiple-axis sensor package and method of assembling a sensor package to sense parameters in multiple sensing axes.
Automotive vehicles are generally equipped with various crash sensing systems that typically include an array of sensors located near anticipated points of contact for relevant potential crashes. In conventional crash sensing systems, crash sensors are usually located on the front, rear, and lateral sides of the vehicle. Accelerometers, also referred to as acceleration sensors, are predominately employed at these locations in vehicle crash sensing systems to sense acceleration. Other types of sensors employed in such crash sensing systems include pressure sensors for detecting side crashes and magnetic field sensors which generally are limited to very low rate applications.
Many sensors, such as the accelerometers, employed in crash sensing systems are generally directional sensitivity sensors that sense a parameter (e.g., acceleration) in a direction along a sensing axis. An accelerometer typically senses acceleration parallel to the axis of sensitivity of the device, and is generally insensitive to accelerations perpendicular to the sensing axis. For signals at an oblique angle (neither parallel nor perpendicular) that the sensor responds to the component parallel to the sensing axis and is generally insensitive to the perpendicular component.
With the increasing number of different types of crashes that are desired to be sensed on a vehicle, the number of sensing axes required is also increasing. To sense signals in multiple sensing axes, vehicle designers are required to use additional crash sensors or to employ sensing devices that sense acceleration or other parameters in multiple sensing axes. Multiple-axis sensing elements may be implemented with micro-electro-mechanical systems (MEMS) technology in which capacitively coupled fingers or plates are arranged in a plane to sense acceleration in two perpendicular sensing axes oriented parallel to the plane of the MEMS device. The in-plane sensing technologies generally have inherent limitations that may be challenging to achieve performance that may be desired for the sensing ranges needed for some automotive crash sensors, particularly those located in peripheral locations. Consequently, the availability of the sensing devices for multiple-axis sensing applications is currently limited for some applications.
Single-axis sensing elements may also be implemented with MEMS technology. The use of multiple single-axis acceleration sensors allows the use of technologies that sense acceleration perpendicular to the plane of the MEMS device. However, the use of such single-axis acceleration sensors in a multiple sensor system generally requires that the MEMS devices be mounted in separate planes relative to each other and electrically connected to each other or to common processing circuitry. This may introduce a significant manufacturing challenge and sufficient additional cost as to make such a sensor impractical in some situations.
Accordingly, it is more desirable to provide for a sensor arrangement to provide multiple-axis sensing that is cost affordable and easy to manufacture. Particularly, it is desirable to provide for a sensor package employing multiple single-axis sensors to effectively achieve a multiple-axis sensing device that is particularly well suited for use on a vehicle, such as for a crash sensor.
In accordance with the teachings of the present invention, a multiple-axis sensor package and method of assembling a multiple-axis sensor package are provided. According to one aspect of the present invention, a multiple-axis sensor package includes a first substrate having first sensing circuitry for sensing a first parameter in a first sensing axis. The package also includes a second substrate having second sensing circuitry for sensing a second parameter in a second sensing axis. The package further includes one or more bent leads connecting the first substrate to the second substrate, wherein the one or more bent leads are bent so that the first sensing axis is different than the second sensing axis.
According to another aspect of the present invention, a method of assembling a multiple-axis sensor package is provided. The method includes the steps of providing a first substrate and forming a first sensing circuit on the first substrate. The first sensing circuit senses a first parameter in a first sensing axis. The method also includes the steps of providing a second substrate and forming a second sensing circuit on the second substrate. The second sensing circuit senses a second parameter in a second sensing axis. The method further includes the steps of connecting the first substrate to the second substrate with one or more bendable leads and bending the one or more bendable leads so as to orient the first substrate at an angle different than the second substrate such that the first sensing axis is different than the second sensing axis.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Referring now to
The crash sensing system further includes an electronic control unit (ECU) 24 shown coupled to each of the crash sensor packages 20 by way of signal communication lines 22. The signal communication lines 22 may be configured as a communication bus, such as for example in a star, a ring, or other configuration. The signal communication lines 22 communicate sensed data to the ECU 24 and may provide power and control signals to the sensor packages 20. The ECU 24 may include an airbag ECU or other dedicated control unit for processing signals generated by the crash sensor packages 20, as is generally known in a vehicle crash sensing system.
Referring to
The first and second substrates 30 and 40 are physically and electrically connected together by way of a plurality of bent lead connectors 90. The lead connectors 90 are electrically conductive and are soldered or otherwise connected at opposite ends to contact pads 34 and 44 on first and second substrates 30 and 40, respectively. The bent lead connectors 90 are bent so that the first sensing X-axis is different than the second sensing Y-axis. In the exemplary embodiment, the first sensing X-axis is perpendicular (i.e., 90 degrees) to the second sensing Y-axis. While five bent lead connectors 90 are shown, it should be appreciated that the sensor package 20 may employ one or more bent lead connectors 90.
The first substrate 30 and first sensing circuit 32 are electrically coupled via the lead connectors 90 to the second substrate 40 and circuitry thereon. Output signals generated by the first and second sensing circuits 32 and 42 may be communicated to common signal processing circuitry or other circuitry so as to process the sensed signals. In one embodiment, ASIC 46 may be provided on one or both of the first and second substrates 30 and 40 to provide common signal processing. In the exemplary embodiment, ASIC 46 is located on the second substrate 40. Additionally, the sensor package 20 includes one or more connector pins 54 that enable the sensor package 20 to be connected to other devices. Connector pins 54 are shown soldered or otherwise connected to contact pads 48. In the embodiment shown, connector pins 54 are housed within a connector sheath 72.
In the embodiment shown, the first substrate 30 is substantially encapsulated in an overmold 50, and the second substrate 40 is substantially encapsulated in an overmold 60. The overmold material may include a known electrically non-conductive (dielectric) material such as an epoxy thermoset polymer. The overmolds 50 ad 60 thereby protect the electrical circuitry and reinforce the mechanical connections of the lead connectors 90 to substrates 30 and 40 by covering the interconnections so that the lead connectors 90 can be bent without damaging the mechanical and electrical interconnections between each of contact pads 34 and 44 and lead connectors 90.
Additionally, the sensor package 20 includes an injection molded housing 70 substantially molded around the overmolded first and second substrates. The injection molded housing 70 is also shown molded over a metal connector bushing 76 that is shown located adjacent to both overmolded substrates. The connector bushing 76 allows the sensor package 20 to be fastened or otherwise connected to a supporting structure, such as a structure on a vehicle.
The sensor package 20 employs first and second single-axis sensors 32 and 42 connected together and arranged so as to sense signals in first and second sensing axes, according to the present invention. In the exemplary embodiment, the sensors illustrated are first and second accelerometers with first accelerometer 32 sensing acceleration Ax in the X-axis and the second accelerometer 42 sensing acceleration Ay in the Y-axis. According to one embodiment, the accelerometers 32 and 42 may each include a piezo resistive micro-electro-mechanical system (MEMS) type accelerometer. One example of a piezo resistive accelerometer is found in sensor Model No. 10381279, commercially available from General Motors, used as the side impact sensor in model year 2007 pickup trucks such as the Chevrolet Silverado and GMC Sierra, and in model year 2007 sport utility vehicles such as the Chevrolet Suburban, Chevrolet Tahoe, GMC Envoy and GMC Yukon. According to another embodiment, the accelerometers 32 and 42 may each include a capacitive type MEMS accelerometer having one or more capacitive plates formed on a substrate for sensing acceleration based on a change of capacitive coupling between the plates. Capacitive type accelerometers may be fabricated using micro-electro-mechanical system (MEMS) fabrications techniques. One example of a MEMS type single-axis accelerometer is disclosed in U.S. Pat. No. 6,761,070, entitled “MICROFABRICATED LINEAR ACCELEROMETER,” the entire disclosure which is hereby incorporated herein by reference. While the sensors 32 and 42 are described herein as accelerometers according to exemplary embodiments, it should be appreciated that other sensors may be employed in the sensor package 20 to sense other parameters. According to other embodiments, the sensors 32 and 42 may include angular rate sensors, electromagnetic sensors, and other types of sensors for sensing parameters (e.g., acceleration, velocity, etc.) that are generally directional.
The assembly of the sensor package 20 will now be described with reference to
Referring to
Following overmolding of the first and second substrates 30 and 40, the overmolded substrates 50 and 60 are configured into a desired orientation relative to each other by bending the electrical lead connectors 90 as shown in
Referring to
Referring to
Following assembly of the lead frame 80 to the first and second substrates 30 and 40, each of the first and second substrates 30 and 40 are substantially overmolded as seen in
Accordingly, the sensor package 20 and assembly method provides for a cost affordable and easy to manufacture multiple-axis sensing device. The sensor arrangement is particularly useful for use on a vehicle 10, such as for crash sensing.
The above description is considered that of the preferred embodiments only. Modifications of the invention will occur to those skilled in the art and to those who make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and not intended to limit the scope of the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the doctrine of equivalents.
