Symmetric Phosphor Conversion Element for Low-Bending LED Packaging
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Solution Overview
Problem
Existing conversion elements with phosphor particles suffer from mechanical stress and bending due to enrichment zones with different thermal expansion coefficients, making them poorly suited for application on radiation-emitting semiconductor chips.
Innovation Solution
A method involving a conversion element with a conversion layer and a compensation layer, where phosphor particles convert electromagnetic radiation and compensation particles are used to mitigate mechanical stress by having similar mechanical and thermal properties, arranged symmetrically to minimize bending, and bonded without a joining layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphor particles are enriched in a conversion layer, then converting efficiency is improved, but mechanical stress and bending increase due to different thermal expansion coefficients
Solution Approach 1:
The patent applies asymmetry by creating an asymmetric structure with an enrichment zone containing phosphor particles positioned at a specific distance from the semiconductor chip, rather than uniform distribution. This asymmetric arrangement allows the enrichment zone to be optimized for converting efficiency while the overall symmetric structure (with compensation layer) maintains mechanical stability.
Solution Approach 2:
The compensation layer acts as a counterweight to balance the mechanical stress and bending caused by the enrichment zone. By positioning the compensation layer symmetrically opposite to the enrichment zone relative to the center plane, it counteracts the thermal expansion differences and mechanical stress, thereby reducing overall bending of the conversion element.
2Device complexity
If conversion layer is bonded directly to semiconductor chip, then device complexity is reduced, but mechanical stress concentration increases
Solution Approach 1:
The conversion element is segmented into multiple functional layers: conversion layer with enrichment zone, compensation layer, and optional scattering layer. This segmentation distributes mechanical stress across multiple interfaces rather than concentrating it at a single bonding interface, reducing stress concentration while maintaining relatively simple overall structure.
Solution Approach 2:
The compensation layer serves as a pre-positioned cushioning element that absorbs and distributes mechanical stress before it can concentrate at the bonding interfaces. By incorporating this stress-distributing layer in advance during manufacturing, the design prevents stress concentration rather than addressing it after the fact.
3Stability of the object's composition
If phosphor particles are distributed uniformly, then mechanical stress is reduced, but converting efficiency decreases
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of phosphor particles through an enrichment zone with higher concentration at a specific location rather than uniform distribution. This localized enrichment optimizes converting efficiency in the region closest to the semiconductor chip where radiation intensity is highest, while the overall structure maintains mechanical stability through the symmetric compensation layer.
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 results in a conversion element with low bending, allowing for stable fixation on semiconductor chips, enhancing performance and longevity by effectively dissipating heat and reducing mechanical stress.
Implementation Method 1
The phosphor particles convert electromagnetic radiation of a first wavelength range into electromagnetic radiation of a second wavelength range
Implementation Method 2
The host lattice alters the electronic structure of the activator in such a way that electromagnetic radiation of the first wavelength range is absorbed and excites an electronic transition in the phosphor particles
Implementation Method 3
the compensation particles preferably do not comprise activator ions. In particular, the compensation particles are preferably non-converting. Preferably, the compensation particles are transmissive of electromagnetic radiation of the first wavelength range
Data Source
AI summary
A method for producing a conversion element comprising the following steps is described: providing a conversion layer having a matrix, in which phosphor particles are brought in, the phosphor particles comprising a host lattice having activator ions and being concentrated in a enrichment zone, providing a compensation layer having the matrix, in which compensation particles are brought in, which comprise the host lattice and are concentrated in a enrichment zone, and joining the conversion layer and the compensation layer in such a way that the enrichment zone of the conversion layer and the enrichment zone of the compensation layer are arranged symmetrically to one another with respect to a symmetry plane of the conversion element. A conversion element and a component are also specified.