Vertical MEMS Sensor Stacking on ASIC for Thermal Accuracy
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Solution Overview
Problem
Existing designs for MEMS sensor and Analog ASIC chip placement on a printed circuit board (PCB) result in reduced accuracy of temperature sensing due to inadequate thermal conduction, as heat from the MEMS sensor must be conducted through the PCB, leading to dissipation and loss of temperature data.
Innovation Solution
The MEMS die is directly mechanically and thermally attached to the Analog ASIC chip using a thermally conducting compound/epoxy, with solder balls and traces providing electrical connections, allowing for improved thermal conductivity and reduced size of the sensing unit package.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the MEMS sensor is placed on one side of the PCB and the Analog ASIC chip is placed on the opposite side of the PCB, then the electrical connection is established, but the thermal conduction capability deteriorates because heat must be conducted through the PCB, reducing temperature sensing accuracy
Solution Approach 1:
The patent transitions from a planar PCB-based arrangement to a three-dimensional stacked configuration where the MEMS sensor die is vertically positioned above the Analog ASIC chip. This vertical stacking enables direct thermal coupling through the interface between the two dies, eliminating the need for heat to conduct through the PCB and thereby significantly improving temperature sensing accuracy while reducing heat loss to the environment.
Solution Approach 2:
The patent merges the thermal pathways by directly coupling the MEMS sensor die and Analog ASIC chip through a common substrate or interface layer. This merging of previously separate thermal paths (through PCB) into a unified direct thermal path ensures that heat generated by the MEMS sensor is efficiently conducted to the temperature sensing elements on the Analog ASIC chip, improving measurement precision.
2Loss of energy
If the sensor is placed on top of the ASIC chip with direct thermal attachment, then thermal conduction capability improves, but the device complexity increases due to the need for precise mechanical and thermal alignment
Solution Approach 1:
The patent introduces an intermediary layer or structure that facilitates the coupling between the MEMS sensor die and Analog ASIC chip. This intermediary component enables direct thermal contact while providing mechanical support and alignment features, thereby achieving improved heat conduction without requiring complex precision alignment procedures during assembly.
Solution Approach 2:
The patent segments the overall assembly into distinct modular components (MEMS sensor die, Analog ASIC chip, and interconnection structure) that can be independently manufactured and then assembled. This segmentation allows for standardized interfaces and alignment features, reducing the complexity of the overall assembly process while maintaining effective thermal coupling.
3Volume of moving object
If the MEMS die is directly attached to the Analog ASIC chip, then the package size is reduced, but the manufacturing precision requirements increase for the direct attachment process
Solution Approach 1:
The patent employs a nested configuration where the MEMS sensor die is positioned and attached directly onto the Analog ASIC chip in a vertical stacking arrangement. This nesting approach minimizes the overall package volume by eliminating lateral separation between components, while the use of standardized die attachment techniques and alignment features keeps manufacturing precision requirements at acceptable levels.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances thermal sensing capabilities and accuracy by ensuring direct heat transfer from the MEMS die to the Analog ASIC chip, improving the reliability of temperature sensing in MEMS applications.
Implementation Method 1
a thermally conducting compound/epoxy is located between the MEMS die and the Analog ASIC chip
Data Source
AI summary
A sensing unit package with reduced size and improved thermal sensing capabilities. An exemplary package includes a printed circuit board with a plurality of electrical traces, an application-specific integrated circuit (Analog ASIC) chip, and a micromachined sensor formed on a microelectromechanical system (MEMS) die. The Analog ASIC chip is electrically and mechanically attached to the printed circuit board. The MEMS die is in direct electrical communication with only a portion of the electrical traces of the printed circuit board and is mechanically and thermally attached directly to the Analog ASIC chip. A thermally conducting compound is located between the MEMS die and the Analog ASIC chip. One or more solder balls electrically attach the Analog ASIC chip to the printed circuit board and one or more solder traces electrically attach the MEMS die to the printed circuit board.