Coaxial Laser Illumination for High Aspect Ratio Fluorescence Detection
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Solution Overview
Problem
Existing fluorescence imaging systems for inspecting electronic devices with high aspect ratio (HAR) structures face challenges in efficient illumination and image contrast due to strong reflections from copper or other reflective surfaces, leading to reduced illumination intensity and inefficient diffuse illumination.
Innovation Solution
A system utilizing a laser light source coupled with an optical fiber to guide laser light perpendicular to the workpiece, accompanied by an illumination optical assembly to direct the laser light effectively between HAR structures, and a collection optical assembly to separate fluorescent light from reflected laser light, enabling clear fluorescence imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LEDs are used to illuminate the PCB, then the illumination source is simple and inexpensive, but strong reflection from copper surfaces reduces illumination intensity and image contrast
Solution Approach 1:
The patent changes the illumination parameters by using laser light with specific wavelengths (350-450 nm) that optimize fluorescence excitation while penetrating HAR structures more effectively. The laser provides coherent, monochromatic light that can be precisely controlled in intensity and direction, overcoming the reflection issues that plague LED-based systems.
Solution Approach 2:
The patent employs optical fibers to deliver laser light in a flexible, curved path to the illumination point. The optical fiber acts as a flexible waveguide that can navigate around HAR structures and deliver light from multiple angles, creating effective diffuse illumination that penetrates deep into the PCB structure between high aspect ratio features.
2Object-affected harmful factors
If LEDs are angled relative to the substrate to reduce reflection, then reflection is minimized, but illumination intensity between HAR structures is reduced and diffuse illumination becomes inefficient
Solution Approach 1:
The patent segments the illumination path by using optical fibers to deliver light from multiple independent sources to different locations on the PCB. This allows simultaneous illumination from multiple angles and positions, ensuring that light penetrates effectively between HAR structures while minimizing reflection from any single surface angle.
Solution Approach 2:
The patent introduces optical fibers as intermediaries between the laser source and the PCB surface. These fibers act as flexible light guides that can deliver illumination from optimal angles while the laser light itself maintains perpendicular incidence on the workpiece, separating the function of angle control (handled by fiber positioning) from the function of illumination (handled by perpendicular laser incidence).
3Illumination intensity
If perpendicular laser illumination is used, then homogeneous illumination between HAR structures is achieved, but reflected laser light interferes with fluorescence detection
Solution Approach 1:
The patent extracts the harmful reflected laser light from the detection path using optical filters and beam splitters. These components separate the reflected laser wavelengths from the fluorescence wavelengths, allowing only the fluorescent signal to reach the detector while blocking the intense reflected laser light that would otherwise overwhelm the weak fluorescence signal.
Solution Approach 2:
The patent applies local quality by using wavelength-specific optical filters at the detection point. These filters are tailored to transmit only the fluorescence wavelength range while blocking the laser wavelength, creating a localized spectral filtering effect that eliminates interference exactly where detection occurs without affecting the perpendicular illumination geometry.
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 system achieves improved fluorescence generation and detection by providing high-intensity, homogeneous illumination between HAR structures, resulting in sharper, high-contrast fluorescence images that enhance defect detection in electronic devices.
Implementation Method 1
The workpiece may emit fluorescent light along an emission path based on illumination from the laser light
Implementation Method 2
an optical fiber coupled to the laser light source and configured to guide the laser light along an illumination path
Data Source
AI summary
The system includes a laser light source configured to emit laser light; an optical fiber coupled to the laser light source and configured to guide the laser light along an illumination path; and an illumination optical assembly disposed in the illumination path and configured to direct the laser light on a workpiece. The workpiece emits fluorescent light along an emission path based on illumination from the laser light. The system further includes a collection optical assembly disposed in the emission path and configured to separate the fluorescent light from reflected laser light; and a detector disposed in the emission path and configured to generate one or more fluorescence images based on the fluorescent light.