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METHODS FOR COOLING A PIEZOELECTRIC TRANSDUCER (PZT) SENSOR STACK ON AN ASIC CHIP

IP.com Disclosure Number: IPCOM000185671D
Publication Date: 2009-Jul-30
Document File: 8 page(s) / 61K

Publishing Venue

The IP.com Prior Art Database

Abstract

A piezoelectric transducer (PZT) sensor is stacked on an organic interposer directly on an ASIC chip. The digital connections (e.g., power or ground connections)on the ASIC chip are attached using a flexible carrier using a thermal compression bonding. Various methods for cooling the PZT sensor stack are disclosed. The various methods reduce the amount of heat that is transferred from the ASIC chip to the PZT sensor stack. In addition, the various cooling methods improve performance and reliability of the PZT sensor.

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RP13113

METHODS FOR COOLING A PIEZOELECTRIC TRANSDUCER (PZT) SENSOR STACK ON AN ASIC CHIP

BRIEF ABSTRACT

    A piezoelectric transducer (PZT) sensor is stacked on an organic interposer directly on an ASIC chip. The digital connections (e.g., power or ground connections) on the ASIC chip are attached using a flexible carrier using a thermal compression bonding. Various methods for cooling the PZT sensor stack are disclosed. The various methods reduce the amount of heat that is transferred from the ASIC chip to the PZT sensor stack. In addition, the various cooling methods improve performance and reliability of the PZT sensor.

KEYWORDS

    ASIC, Application Specific Integrated Circuit, PZT, piezoelectric transducer, stack, sensor, heat sink, cooling, heating, thermal, temperature, phase change material, PCM, convection cooling, thermoelectric (T/E), synthetic jet.

DETAILED DESCRIPTION

    A monolithic stack of PZT (piezoelectric transducer) layers and electrode, called a PZT stack, is used for producing displacement piezo actuators. In general, PZT sensors measure and convert a variety of mechanical actions, such as a force, acceleration or pressure into electrical signals and then these signals are fed into data processing systems for electronic evaluation and processing. For example, the PZT sensors (e.g., knock sensors, crash sensors and others) are used in safety devices for passengers.

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RP13113

    In addition, an increased demand of compact and complex electronic devices has led to miniaturization and development of the various electronic components (e.g., application specific integration circuits (ASIC). Accordingly, the PZT sensors are stacked on an ASIC chip either using an organic interposer (e.g., a Kapton layer in combination with Ag-epoxy filler) or using pillar (e.g., gold (Au) pillar). Further, the PZT sensor stack is connected to the ASIC chip using a flexible carrier.

    Generally, during operations, the ASIC chip, and associated electrical/electronic circuitries dissipate relatively large amounts of heat. The PZT sensors are very sensitive to temperature, and heat dissipated from the ASIC during such operations lowers the performance of these sensors. Thus an efficient heat sink mechanism is desirable to efficiently dissipate the heat that is emitted from the ASIC chips and associated electronic circuitry.

    Accordingly, various active and passive cooling methods are described and these methods efficiently remove the generated heat from the backside of the ASIC.

    Figure 1 illustrates a schematic design of a cooling apparatus that uses Phase Change Material (PCM) for cooling a PZT sensor stack disposed on an ASIC chip. PZT sensor stack is coupled with the ASIC chip through an organic interposer and Au plated pillar. On the other side, a thermal material block is connected to the ASIC chip through Thermal Interface Material (TIM). The thermal material block is a rigid block h...