Optoelectronics Assembly Optical Crosstalk Isolation
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Solution Overview
Problem
Optoelectronics assemblies face issues with optical crosstalk due to transparent passivation layers allowing light leakage between the light source and light sensor chambers, leading to erroneous results.
Innovation Solution
The implementation of a semiconductor die assembly encapsulated in a molded material with conductive pillars and an encapsulation layer that blocks optical crosstalk, along with an enclosure defining separate chambers for the light source and light sensor, ensures electrical connections while preventing light leakage between the chambers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transparent passivation layer is formed on the semiconductor die, then electrical connections and protection are achieved, but optical crosstalk occurs between chambers allowing light leakage
Solution Approach 1:
An opaque encapsulation layer is introduced as an intermediary between the transparent passivation layer and the light source chamber. This encapsulation layer acts as a light barrier that prevents optical crosstalk while allowing the passivation layer to maintain its electrical and protective functions. The encapsulation layer is positioned strategically to block light paths without interfering with electrical connections through the conductive pillars.
Solution Approach 2:
The semiconductor die structure is segmented into multiple functional layers with distinct optical properties. The passivation layer remains transparent for electrical functions, while the encapsulation layer is made opaque specifically for optical isolation. This segmentation allows each layer to perform its specialized function without compromising the other, resolving the contradiction between electrical reliability and optical isolation.
2Volume of moving object
If the semiconductor die is positioned below both chambers, then compact packaging is achieved, but light from the light source leaks into the light sensor chamber through the passivation layer
Solution Approach 1:
The opaque encapsulation layer serves as a light-blocking intermediary that allows the semiconductor die to remain positioned below both chambers for compact packaging. The encapsulation layer is applied over the passivation layer in the region exposed to the light source chamber, creating a selective light barrier that maintains compact geometry while protecting the light sensor from stray light and ensuring measurement precision.
3Object-affected harmful factors
If separate chambers are defined for light source and light sensor, then optical isolation is improved, but manufacturing complexity increases
Solution Approach 1:
The optical isolation function is merged with the existing encapsulation process rather than requiring separate chamber structures. The opaque encapsulation layer is applied during the standard semiconductor packaging process, combining the optical isolation benefit with the existing manufacturing flow. This approach prevents optical crosstalk without significantly increasing device complexity, as it utilizes the encapsulation step already present in the production process.
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 effectively isolates the light source and light sensor, preventing optical crosstalk and ensuring accurate detection in optoelectronics assemblies by using conductive pillars and an encapsulation layer to block light leakage, thereby enhancing the reliability of optoelectronics assemblies.
Implementation Method 1
The encapsulation layer blocks optical crosstalk between the first and second chambers
Data Source
AI summary
An electronics assembly includes a semiconductor die assembly, an enclosure affixed to the semiconductor die assembly, the enclosure defining first and second chambers over the semiconductor die assembly, and first and second optical elements mounted in the first and second chambers, respectively. The semiconductor die assembly includes a semiconductor die encapsulated in a molded material, an encapsulation layer located on the top surface of the semiconductor die, and at least one patterned metal layer and at least one dielectric layer over the encapsulation layer. Conductive pillars extend through the encapsulation layer for electrical connection to the semiconductor die. The encapsulation layer blocks optical crosstalk between the first and second chambers. A method is provided for making the electronics assembly.