Composite Converter Sintering to Eliminate Roughness and Microcracks
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Solution Overview
Problem
The high surface roughness and microcracks in polymer-based composite converters produced by the wet gelation process cause damage to blue LED chips during assembly, leading to functional failures, as the process results in excessive volume shrinkage and optical performance issues.
Innovation Solution
A dry process involving pyrolysis and sintering at ultra-low temperatures, assisted by external forces like pressing and extruding, is used to create composite materials with polymethylsilsesquioxane (PMSQ) or polysilesquioxane (PSQ) and phosphors, which eliminates surface roughness and microcracks by inducing gelation and densification simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If wet gelation process is used to produce polymer-based composite converters, then brightness and flexible color tuning are improved, but surface roughness increases excessively causing LED chip damage
Solution Approach 1:
The patent changes the fundamental processing parameters from wet gelation to dry sintering. This parameter change transforms the chemical reaction environment from liquid-based to solid-state, eliminating the volume shrinkage that causes surface roughness while preserving the phosphor dispersion needed for brightness and color tuning.
Solution Approach 2:
The patent replaces the chemical gelation mechanism with a thermal sintering mechanism. Instead of using liquid polymer precursors and catalysts that cause shrinkage, the invention uses controlled heating to activate phosphors and form the composite structure, substituting chemical action with thermal-mechanical action that produces smoother surfaces.
2Adaptability or versatility
If wet gelation process with liquid polymer precursor is used, then flexible color tuning is achieved, but volume shrinkage increases causing microcracks and surface spikes
Solution Approach 1:
The patent changes the physical state parameter of the polymer from liquid precursor to solid particles. This parameter change eliminates the volume shrinkage associated with gelation while maintaining the ability to tune colors through phosphor selection and composition, as color tuning depends on phosphor properties rather than polymer chemistry.
Solution Approach 2:
The patent extracts the harmful liquid gelation step from the processing sequence. By removing the liquid polymer precursor and catalyst system that cause shrinkage and microcracks, the invention retains only the essential functions of phosphor dispersion and color conversion, achieving structural integrity while preserving color flexibility.
3Manufacturing precision
If fillers are introduced to reduce volume shrinkage in wet process, then surface roughness is reduced, but optical properties of converters are affected
Solution Approach 1:
The patent inverts the conventional approach by not adding fillers to reduce shrinkage, but rather eliminating the shrinkage-causing liquid gelation process itself. This inversion removes the need for optical fillers that would compromise converter performance, as the dry sintering process inherently produces smooth surfaces without requiring additional filler materials.
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 method achieves a significant reduction in surface roughness below 1.0 μm, minimizing damage to LED chips and enhancing the optical performance and service life of the converters by eliminating spikes and nodules, while maintaining brightness and cost-effectiveness.
Implementation Method 1
A dry process involving pyrolysis and sintering at ultra-low temperatures
Implementation Method 2
A dry process involving pyrolysis and sintering at ultra-low temperatures
Implementation Method 3
assisted by external forces like pressing and extruding
Implementation Method 4
assisted by external forces like pressing and extruding
Implementation Method 5
the blue light emitted by an GaN or InGaN-LED is absorbed by a converter (phosphor or luminescent material) that can re-emit the absorbed energy in the form of photons
Data Source
AI summary
The present invention concerns a method of ultra-low temperature sintering for making a composite material which is useful for composite converters. The invention also concerns a composite material comprising a phosphor and a polymer, wherein the polymer is selected from polymethylsilesquioxane (PMSQ) or polysilesquioxane (PSQ), and wherein the composite material has a surface roughness below 1.000 μm.