Encapsulated Sensor Circuit Layout for Moisture-Stable Measurement
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Solution Overview
Problem
Existing pressure sensors are susceptible to moisture and thermomechanical stresses, leading to hysteresis and complexity in manufacturing and design.
Innovation Solution
The solution involves encapsulating the measuring and operating circuit on a carrier body, using a chip-scale package with a ball grid array connection, and employing materials with differing thermal expansion coefficients to absorb deformation energy, while integrating an A/D converter for early digitization to reduce humidity influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the measuring and operating circuit is hermetically sealed using active brazing alloy along a circumferential joint, then moisture protection is improved, but manufacturing complexity increases and thermomechanical stresses increase
Solution Approach 1:
The patent extracts the circuit board and electronic components from the sensor housing, mounting them directly on the sensor element's rear surface. This eliminates the need for separate hermetic sealing of a circuit housing, thereby reducing manufacturing complexity while maintaining moisture protection through the direct integration and conformal coating approach.
Solution Approach 2:
The patent merges the circuit board mounting surface with the sensor element rear surface, creating an integrated structure. The circuit board is directly bonded to the sensor element using adhesive layers, combining previously separate components (sensor element, circuit board, housing) into a unified assembly that reduces sealing interfaces and manufacturing steps.
2Reliability
If the measuring and operating circuit is hermetically sealed using active brazing alloy, then moisture protection is improved, but thermal stress during production increases
Solution Approach 1:
The patent replaces the high-temperature active brazing alloy process with lower-temperature alternative bonding methods such as adhesive bonding or eutectic bonding. These methods achieve hermetic sealing at reduced temperatures, minimizing thermal stress on the sensor element and surrounding components during manufacturing.
3Strength
If the cup serves as rear support and is hermetically sealed to sensor body, then mechanical support is improved, but connection complexity and hysteresis increase
Solution Approach 1:
The patent extracts the separate cup component and its complex hermetic sealing requirement, replacing it with a simplified approach where the circuit board is directly mounted on the sensor element rear surface using adhesive bonding. This eliminates the cup-sensor body connection interface, reducing both mechanical complexity and potential hysteresis sources.
4Reliability
If bonding wires are routed within housing from rear sensor surface, then electrical connection is achieved, but housing footprint increases
Solution Approach 1:
The patent merges the electrical connection points with the sensor element rear surface, eliminating the need for a separate housing interior space for wire routing. The circuit board is positioned directly adjacent to the sensor element, with electrical connections made through controlled impedance traces on the circuit board itself, reducing the required footprint.
5Adaptability or versatility
If large housing base area is used with different thermal expansion coefficients, then component accommodation is improved, but thermomechanical stresses increase
Solution Approach 1:
The patent applies local quality by using materials with matched thermal expansion coefficients at each bonding interface. The adhesive layer or eutectic bonding material is specifically selected to have thermal expansion properties intermediate between the sensor element and circuit board, creating a compliant interface that accommodates thermal expansion differences without generating excessive stress.
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 design minimizes moisture sensitivity and thermomechanical stress effects, ensuring high measurement accuracy and miniaturization with reduced electrical connections, thus enhancing the sensor's reliability and performance.
Implementation Method 1
encapsulating the measuring and operating circuit on a carrier body
Implementation Method 2
connection to the connection contacts in the surface section by means of a ball grid array
Implementation Method 3
employing materials with differing thermal expansion coefficients to absorb deformation energy
Implementation Method 4
integrating an A/D converter for early digitization to reduce humidity influence
Data Source
Figure 1
AI summary
The measuring device (1) according to the invention comprises: a sensor element (100) with an electrical transducer (130) for providing a primary signal dependent on the measured variable and a sensor body with a flat surface portion; and a measurement and operation circuit (200) for driving the transducer and for processing the primary signals, the measurement and operation circuit (200) comprising at least one carrier, and a plurality of circuit components including at least one integrated circuit, and passive components, the carrier comprising an electrically insulating carrier body (221, 241, 261) and conductor paths which extend in the carrier body or on its surface, the integrated circuit (224, 244, 246) and the passive component (226, 266) being arranged on the carrier body surface and contacted by the conductor paths; wherein the at least one carrier body (221) is fixed to the surface portion, and the transducer is electrically connected to circuit components (224, 226) of the measurement and operation circuit via conductor paths, the components (224, 246, 244, 246, 264, 266) being encapsulated with a molding compound (222, 242, 262).