LED Wavelength Measurement and Conformal Coating
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Solution Overview
Problem
Existing methods for producing white light from LEDs often result in chip waste and inconsistent results due to phosphor ratio variations not being based on underlying device measurements, leading to color dispersion and increased costs from separate chip-level processing.
Innovation Solution
Measuring the wavelength of an LED's light output at the wafer level and applying a conformal coating with a phosphor ratio of yellow, green, or red to convert the light to white, allowing for uniformity and consistency in results, which can be applied at either the wafer or chip level using methods like paraffin wax, silk screen, or photo resist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If phosphor ratio is not adjusted based on wavelength measurement, then manufacturing process is simpler, but color consistency and white light quality deteriorate
Solution Approach 1:
The patent measures the wavelength of the LED chip before applying the phosphor coating, and prepares phosphor mixtures with different ratios in advance based on these measurements. This preliminary action ensures that each chip receives the appropriate phosphor ratio for its specific wavelength, achieving consistent white light output across all chips.
Solution Approach 2:
The patent applies different phosphor ratios to different LED chips based on their individual wavelength characteristics. Instead of using a uniform phosphor ratio for all chips, the system tailors the phosphor composition to each chip's specific properties, ensuring optimal color consistency for each individual device.
2Manufacturing precision
If processing is performed at chip level instead of wafer level, then individual chip customization is possible, but chip waste and processing costs increase
Solution Approach 1:
The patent combines multiple functions into the wafer-level processing step: wavelength measurement, phosphor ratio determination, and conformal coating application are all performed together on the entire wafer in a single integrated process. This merging eliminates the need for separate chip-level processing steps, reducing both waste and costs while maintaining customization.
Solution Approach 2:
The conformal coating apparatus is designed to perform multiple functions simultaneously: it measures wavelengths across all chips, determines appropriate phosphor ratios, and applies the customized phosphor coating to each chip location on the wafer. This multi-functional approach enables individual chip customization without requiring separate processing equipment or steps for each chip.
3Manufacturing precision
If conformal coating with customized phosphor ratio is applied, then white light quality and uniformity improve, but manufacturing process complexity increases
Solution Approach 1:
The patent introduces a conformal coating apparatus as an intermediary system that bridges the gap between LED chip wavelength characteristics and phosphor coating application. This apparatus automatically measures wavelengths, determines appropriate phosphor ratios, and applies the customized coating, eliminating the need for manual intervention and simplifying the overall process despite the customization requirements.
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 approach reduces color deviation between chips, eliminates the need for separate sorting and packaging, and decreases production costs by achieving consistent white light output directly at the wafer level, enhancing yield and reducing process time and equipment investment.
Implementation Method 1
converting a light output of the LED to white light using the conformal coating
Data Source
AI summary
The present invention provides an LED and method of manufacture in which white light is produced. Specifically, under the present invention, a wavelength of a light output by an LED (e.g., blue or ultra-violet (UV)) is measured (e.g., at the wafer level). Based on the wavelength measurement, a conformal coating is applied to the LED. The conformal coating has a phosphor ratio that is based on the wavelength. Moreover, the phosphor ratio is comprised of at least one of the following colors: yellow, green, or red. The light output of the LED is then converted to white light using the conformal coating. In a typical embodiment, these steps are performed at the wafer level so that uniformity and consistency in results can be better obtained. However, it should be understood that the same teachings could be applied at the chip level. Moreover, several different approaches can be implemented for isolating the coating area. Examples include the use of a paraffin wax, a silk screen, or a photo resist.