White LED Manufacturing via Expansion Sheet Stretching

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Solution Overview

Problem

Existing methods for manufacturing white light-emitting diode (LED) elements using blue light-emitting diode chips are costly and result in non-uniform light tones due to the need for multiple masks and irregular coating surfaces, making it difficult to achieve consistent white light emission.

Innovation Solution

A method involving an integral LED material plate bonded to an expansion sheet, diced into individual chips, with the sheet stretched to widen spacing and a light-pervious synthetic resin layer applied, allowing for uniform coating thickness and easy tone adjustment by varying stretching dimensions and cutting widths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If photolithography or screen printing is used to apply the synthetic resin coating, then the coating can be applied to the LED chips, but irregularities are formed at the surface of the coating making it non-smooth and non-flat

Engineering Contradiction:

Improvecoating applicationVSAvoidsurface smoothness

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The process segments the coating application into two distinct steps: first embedding the LED chips in the synthetic resin layer, then separately removing the resin between chips through dicing. This separation allows the coating surface to be formed smoothly during embedding while the spacing areas are cleanly removed afterward, eliminating the surface irregularities caused by direct mask-based application methods.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If different masks are prepared for different coating thicknesses to achieve different white tones, then the desired light tone can be achieved, but manufacturing cost increases significantly

Engineering Contradiction:

Improvelight tone adjustmentVSAvoidmask variety

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The invention changes the parameter being controlled from mask pattern geometry to expansion sheet stretching ratio. By varying the stretching dimensions and cutting width of the expansion sheet, different coating thicknesses and light tones can be achieved with a single mask design, eliminating the need for multiple masks while maintaining full adaptability for tone adjustment.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If the LED chips are mounted at fixed pitch on the substrate, then the manufacturing process is simplified, but the coating thickness cannot be easily adjusted to change light tone

Engineering Contradiction:

Improvechip mountingVSAvoidcoating thickness adjustment

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The invention introduces dynamic adjustability through the expansion sheet stretching process. The fixed pitch mounting is maintained during chip placement, but the subsequent stretching of the expansion sheet dynamically adjusts the spacing between chips and the resulting coating thickness. This allows the system to maintain manufacturing simplicity while gaining flexibility for tone adjustment.

Inventive Principle:

Principle #15Dynamics

4Manufacturing precision

If the expansion sheet is stretched to widen spacing between LED chips, then uniform coating thickness can be achieved, but the process complexity increases

Engineering Contradiction:

Improvecoating thickness uniformityVSAvoidprocess steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention merges multiple functions into the expansion sheet: it serves as both the mounting substrate for LED chips and the medium for forming the synthetic resin coating. The stretching of this single component simultaneously achieves chip spacing adjustment and coating thickness control, reducing overall process complexity despite the added stretching step.

Inventive Principle:

Principle #5Merging (Combining)

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 method reduces manufacturing costs and enhances light emission brightness by ensuring a smooth, uniform coating on LED chips, allowing for precise control over light tone and increased light emission from side surfaces.

Implementation Method 1

part of the blue light emission is converted into yellow light by the fluorescent material in the coating

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 2

stretching the expansion sheet in two directions which are perpendicular to each other along a surface so that the spacing between adjacent LED chips is widened

Methodology Applied

Scientific EffectElastic deformation: Deformation

Data Source

PatentUS7759145B2Process for producing light-emitting diode element emitting white light

Publication Date: 2010.07.20 ROHM CO LTD

AI summary

An object of the present invention is to manufacture a white light-emitting diode element by coating a blue light-emitting diode chip with a coating of a synthetic resin containing a fluorescent material.The object is achieved by bonding an LED material plate corresponding to a plurality of LED chips to an expansion sheet, dividing the LED material plate into individual LED chips, stretching the expansion sheet to widen the spacing between the LED chips, forming a synthetic resin layer between the chips, and dicing the synthetic resin layer to remove portions of the synthetic resin layer between the LED chips while leaving part of the synthetic resin layer on a side surface of each of the LED chips.