Sensor Assembly Sealing and Strain Relief for Head-Mounted Devices
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Solution Overview
Problem
Head-mountable devices face challenges in protecting sensors from external environmental influences such as temperature and humidity, which can affect their performance and longevity, and excessive strain on sensors can diminish their effectiveness.
Innovation Solution
A sensor assembly that securely mounts sensors within a sealed enclosure, using a flex circuit and a base plate with a complementary thermal expansion adhesive, and a sealing member to isolate the sensor from external factors, while allowing for flexible mounting and strain relief to prevent excessive force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sensors are exposed to external environment, then ease of mounting is improved, but sensor performance deteriorates due to temperature and humidity influences
Solution Approach 1:
The device is divided into separate functional modules: a sensor module containing the sensor, a flex circuit board for electrical connections, and a housing structure. This segmentation allows the sensor to be mounted easily on the flex circuit while the housing provides environmental protection, resolving the contradiction between ease of mounting and sensor performance protection.
Solution Approach 2:
The flex circuit board acts as an intermediary between the sensor and the housing structure. It provides both mechanical support for easy sensor mounting and electrical connectivity, while the housing serves as an intermediary protective barrier that shields the sensor from environmental factors like temperature and humidity, thus maintaining sensor performance.
2Stability of the object's composition
If sensors are rigidly mounted, then structural stability is improved, but sensor effectiveness deteriorates due to excessive strain
Solution Approach 1:
The patent uses a flex circuit board with a flexible substrate to mount the sensor. This flexible mounting structure provides structural stability while accommodating thermal expansion and contraction, preventing excessive strain on the sensor that would diminish its effectiveness, thus resolving the contradiction between structural stability and sensor effectiveness.
Solution Approach 2:
The flexible substrate's mechanical properties allow it to change its physical state in response to thermal parameters. As temperature changes cause expansion or contraction, the flexible substrate absorbs these dimensional changes, maintaining structural stability while preventing harmful strain transmission to the sensor, thereby preserving sensor effectiveness.
3Object-affected harmful factors
If sealed enclosure is used, then protection from environmental factors is improved, but heat dissipation deteriorates
Solution Approach 1:
The flexible substrate in the sealed enclosure acts as a thermal management component. While the enclosure seals the sensor from environmental factors like humidity and dust, the flexible substrate's thin-film structure allows heat to conduct through it, enabling heat dissipation while maintaining the protective seal, thus resolving the contradiction between environmental protection and heat dissipation.
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 solution ensures predictable and robust sensor performance over the life of the head-mountable device by isolating sensors from environmental influences and minimizing strain, maintaining accurate orientation measurements without the need for repeated calibration.
Implementation Method 1
the adhesive layer having a coefficient of thermal expansion that is complementary to a coefficient of thermal expansion of the circuit board and the sensor package to minimize strain on the sensor
Data Source
AI summary
A sensor assembly for a head-mountable device, the sensor assembly comprising: a flex circuit, an inertial measurement unit coupled to the flex circuit, an enclosure disposed around the inertial measurement unit and a portion of the flex circuit, to define a sealed volume containing the inertial measurement unit and the portion of the flex circuit. Thereby, a head-mountable device can securely support sensors in a manner that maintains their positions and orientations over time and isolates the sensors from an external environment. The sensor can be mounted within a sealed enclosure while maintaining an operable connection to the sensor. The sensor assemblies provides high robustness during the entirety of the service life of the head-mountable device without placing strain on the sensors themselves. The seal of the enclosure can isolate the sensor from external influences by preventing ingress of elements through the case and plate.