Reflective Optical Encoder Package Using Wafer-Level Packaging
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Solution Overview
Problem
Reflective optical encoders suffer from low contrast and resolution, limiting their operational speed and accuracy compared to transmissive and imaging encoders, which often require higher profiles and more materials.
Innovation Solution
A reflective optical encoder package with an integrated circuit featuring a recess for the light emitter and a pre-formed optically transmissive glass or plastic layer, allowing light to traverse and reflect from a code scale for detection, eliminating the need for a separate lens and reducing package height, while using wafer level packaging for enhanced stability and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If light emitters and detectors are placed on the same substrate to achieve low profile design, then package height is reduced, but measurement precision and resolution deteriorate due to low contrast
Solution Approach 1:
The package is segmented into distinct functional layers: the integrated circuit substrate containing detectors, a separate optically transmissive layer, and a recess structure for the light emitter. This segmentation allows each component to be optimized independently while maintaining compact overall dimensions, resolving the contradiction between low profile design and measurement precision.
Solution Approach 2:
The invention transitions from a planar arrangement to a three-dimensional stacked architecture with vertical layering. The recess structure creates depth variation, allowing the light emitter to be positioned at a different vertical level than the detectors, improving optical path geometry and contrast while maintaining a compact footprint.
2Ease of manufacture
If conventional packaging methods are used, then assembly is simpler, but manufacturing precision and reliability deteriorate due to stack-up tolerances and CTE mismatches
Solution Approach 1:
The optically transmissive layer is integrated directly onto the integrated circuit substrate as a unified structure, eliminating separate assembly steps for aligning and bonding multiple components. This merging of layers reduces the number of interfaces and associated tolerances, improving manufacturing precision while maintaining ease of manufacture through streamlined processing.
Solution Approach 2:
The invention changes the material parameters by selecting an optically transmissive layer with thermal expansion characteristics matched to the integrated circuit substrate. This parameter matching eliminates CTE mismatches that would otherwise cause reliability issues, while the layer integration simplifies the manufacturing process.
3Measurement precision
If transmissive optical encoder design is used to achieve high resolution and speed, then measurement precision is improved, but device complexity increases due to requiring light emitters opposite light detectors
Solution Approach 1:
Instead of placing the light emitter opposite the detector as in conventional transmissive encoders, this invention inverts the arrangement by positioning both components on the same substrate in a stacked configuration. The recess structure enables the emitter to illuminate through the optically transmissive layer down to the detector, achieving high resolution while simplifying the package structure.
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
The solution enhances the stability and precision of the encoder package, allowing for improved performance, reduced manufacturing costs, and increased reliability by eliminating CTE mismatches and shrinkage issues, enabling higher resolution and speed operations.
Implementation Method 1
a light emitter, the first layer and the light detector are configured to permit at least a portion of light emitted by the light emitter to traverse the first layer
Implementation Method 2
traverse the first layer in an upward direction for reflection from a code scale disposed above the reflective optical encoder package
Implementation Method 3
a first optically transmissive pre-formed layer disposed over the light detector and the light emitter and attached to at least portions of the first surface, wherein the light emitter, the first layer and the light detector are configured to permit at least a portion of light emitted by the light emitter to traverse the first layer
Data Source
AI summary
Disclosed are various embodiments of a reflective optical encoder package having a light emitter and a light detector disposed on an integrated circuit having an optically transparent glass layer disposed thereover. The package can be manufactured without resort to wirebonding techniques and instead can be made using wafer level packaging methods and materials. The package can also be made of lower profile or smaller footprint than many conventional optical encoder packages, and may be employed to sense or detect rotary or linear motion.