Reflow-Stable Optical Diffuser for High-Temp Sensor Packaging
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Solution Overview
Problem
High-temperature manufacturing processes for optical sensor modules, such as reflow processes, can adversely impact the mechanical stability and optical performance of integrated diffusers, leading to performance drift and calibration challenges.
Innovation Solution
The integration of a reflow-stable optical diffuser, composed of materials like hardened epoxy resin or porous quartz glass, surrounded by an epoxy molding compound, which maintains transmissivity and stability even at high temperatures, and a film-assisted transfer molding process to ensure precise placement and curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-temperature reflow processes are used for manufacturing, then productivity and manufacturing capability are improved, but the mechanical stability and optical performance of the diffuser deteriorate
Solution Approach 1:
The patent changes the material parameters of the diffuser by using a glass substrate with specific thermal properties that can withstand high reflow temperatures. The glass substrate is selected to have thermal expansion characteristics matching the surrounding components, allowing it to maintain structural integrity and optical performance through the high-temperature manufacturing process without degradation
Solution Approach 2:
The patent creates a composite structure where the diffuser is integrated with a glass substrate and surrounded by epoxy molding compound. This composite design combines the optical properties of the diffuser material with the thermal stability of glass and the protective encapsulation of epoxy, enabling the assembly to survive high-temperature reflow processing while maintaining optical functionality
2Ease of manufacture
If traditional diffuser materials are used, then ease of manufacture is improved, but mechanical stability at high temperatures deteriorates
Solution Approach 1:
The patent changes the material composition parameter from traditional plastic or acrylic diffusers to glass-based materials that exhibit thermal stability at reflow temperatures. This material substitution maintains manufacturability through standard semiconductor packaging processes while providing the necessary thermal resistance to prevent degradation during high-temperature assembly operations
3Device complexity
If integrated diffuser design is used, then device complexity is reduced, but susceptibility to temperature-induced performance drift increases
Solution Approach 1:
The patent introduces a glass substrate as an intermediary layer between the optical sensor die and the diffuser material. This glass intermediary acts as a thermal buffer and mechanical support that protects the integrated diffuser structure from temperature-induced stress and deformation during reflow processing, maintaining optical performance stability while preserving the benefits of the integrated compact design
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 provides a stable optical performance with negligible parameter drift after reflow processes, enabling unit-level calibration and compact package design suitable for various applications, including ambient light sensors and camera modules.
Implementation Method 1
curing the liquid epoxy resin material to form a reflow-stable optical diffuser
Implementation Method 2
Diffusers are optical elements that can be used to cause light to spread more evenly across a surface, reducing or removing high intensity bright spots
Implementation Method 3
sputtering a metal mask on the glass substrate to define an optical aperture
Implementation Method 4
performing a film assisted transfer molding process to provide an epoxy molding compound that laterally surrounds the optical sensor die and the glass substrate
Data Source
AI summary
An apparatus comprises an optical sensor package that includes an optical sensor die. The optical sensor package further includes a reflow-stable optical diffuser disposed over the optical sensor die. The optical diffuser is surrounded laterally by an epoxy molding compound.