Wafer-Level Optical Sensor Packaging with Stray Light Blocking
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Solution Overview
Problem
Current optical sensor packaging technologies are either complex and costly or unsuitable for wafer-level applications due to aspect ratio and pin dimension requirements, leading to errors from stray light and optical crosstalk.
Innovation Solution
A method of producing optical sensors at wafer-level using a combination of transparent and opaque mold structures through wafer-level molding, where the transparent first mold structure encloses the light sensitive component and the opaque second mold structure blocks stray light, reducing optical crosstalk and enhancing flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If open cavity package technology is used to reduce optical crosstalk and stray light errors, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple packaging functions (encapsulation, optical filtering, mechanical protection, and electrical isolation) into a single integrated wafer-level mold structure. This eliminates the need for separate open cavity components while maintaining optical performance, directly resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The invention changes the packaging scale from individual device level to wafer level, and transitions from open cavity to closed mold structure. These parameter changes enable mass production with consistent optical properties while reducing complexity through standardization.
2Measurement precision
If open cavity package technology is used to reduce optical crosstalk, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges multiple manufacturing steps into a single wafer-level molding process, eliminating sequential operations required by open cavity packaging. This integration dramatically reduces manufacturing cost while achieving the same optical isolation performance.
Solution Approach 2:
The transition to wafer-level processing changes the manufacturing parameter from individual device assembly to batch processing. This parameter change enables economies of scale, reducing per-unit cost while maintaining optical precision through mold-integrated features.
3Measurement precision
If traditional packaging is used to block stray light, then measurement precision is improved, but the device size increases
Solution Approach 1:
The patent merges optical filtering features directly into the mold structure, eliminating the need for separate aperture components and mounting hardware. This integration blocks stray light while minimizing package volume by combining multiple functions in a single compact structure.
Solution Approach 2:
The invention uses the vertical dimension of the mold structure to achieve optical isolation, with the mold material itself forming the light-blocking barriers. This dimensional approach reduces lateral footprint while maintaining optical precision through vertically integrated features.
4Measurement precision
If wafer-level molding with opaque material is used to block stray light, then measurement precision is improved, but light transmission to the sensor is reduced
Solution Approach 1:
The patent applies local quality by making the mold material opaque only in specific regions where stray light blocking is needed, while maintaining transparency or optical accessibility in regions where light must reach the sensor. This spatial differentiation resolves the contradiction between stray light rejection and light transmission efficiency.
Solution Approach 2:
The mold structure is segmented into functional zones: opaque regions for stray light blocking and transparent/optically accessible regions for signal transmission. This segmentation enables simultaneous achievement of both optical isolation and efficient light coupling to the sensor.
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 approach reduces errors from stray light and optical crosstalk, provides a more flexible and cost-effective packaging solution, and allows for smaller, more compact optical sensor designs with integrated diffuser layers, meeting manufacturing requirements for mass production.
Implementation Method 1
The first mold structure is formed by wafer-level molding a first mold material over the top surface of the wafer
Implementation Method 2
The second mold structure is made at least partly opaque by using an optically opaque mold material as second mold material
Data Source
Figure 1
Figure 2(A)~2(C)
Figure 2(D)~2(F)
AI summary
A method of producing an optical sensor at wafer-level, comprising the steps of providing a wafer (1) having a main top surface (10) and a main back surface (13) and arrange at or near the top surface (10) of the wafer at least one first integrated circuit (11) having at least one light sensitive component (12). Furthermore, providing in the wafer (1) at least one through-substrate via (14) for electrically contacting the at least one first integrated circuit (11) via the back surface (13) and forming a transparent first mold structure (2) by wafer-level molding a first mold material over the top surface (10) of the wafer (1), such that the first mold structure (2) at least partly encloses the first integrated circuit (11). Finally, forming an opaque second mold structure (3) by wafer-level molding a second mold material over the first mold structure (2), such that the second mold structure (3) at least partly encloses the first mold structure (2), leaving an aperture (30) open on top of the at least one top surface (21) of the transparent first mold structure (2).