Dual-Gauge Leadframe for LED Heat Dissipation

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Solution Overview

Problem

Conventional LED packages face challenges in heat dissipation and thermal resistance due to thin leadframes, which limits their power handling capacity and efficiency, especially when multiple LEDs are mounted closely together for applications like general lighting that require specific color and intensity of light.

Innovation Solution

A modular package design featuring a dual-gauge leadframe with a thicker central region for improved heat dissipation and a thermoset package body that fills recesses and provides a strong mechanical connection, reducing thermal resistance and enhancing hermeticity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If thin leadframes are used in conventional LED packages, then ease of manufacture and handling are improved, but heat dissipation capability deteriorates

Engineering Contradiction:

Improveease of handlingVSAvoidheat dissipation capability

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The leadframe is designed with non-uniform thickness, featuring a thicker central region (first thickness) for heat dissipation and a thinner peripheral region (second thickness) for ease of handling and electrical connection. This local differentiation allows the same component to simultaneously optimize both heat dissipation performance and manufacturing ease.

Inventive Principle:

Principle #3Local quality

2Illumination intensity

If multiple LEDs are mounted closely together, then light intensity and color quality are improved, but thermal resistance increases

Engineering Contradiction:

Improvelight intensityVSAvoidthermal resistance

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The thicker central region of the leadframe is specifically positioned beneath the LED array to provide enhanced heat dissipation capacity where it is most needed, while the thinner peripheral regions maintain ease of handling. This allows multiple LEDs to be mounted closely together for high light intensity without excessive thermal resistance.

Inventive Principle:

Principle #3Local quality

3Temperature

If leadframe thickness is increased for better heat dissipation, then heat extraction is improved, but manufacturing difficulty increases

Engineering Contradiction:

Improveheat extractionVSAvoidmanufacturing difficulty

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The leadframe uses different thicknesses in different regions: a thicker central region (first thickness) for heat extraction and a thinner peripheral region (second thickness) for manufacturing ease. The second thickness is specifically designed to be less than 0.50 mm to maintain ease of handling and electrical connection, while the first thickness provides sufficient heat dissipation capability.

Inventive Principle:

Principle #3Local quality

4Device complexity

If conventional leadframe designs are used, then device complexity is reduced, but hermeticity deteriorates

Engineering Contradiction:

Improvedevice complexityVSAvoidhermeticity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The thermoset package body is applied specifically to the thicker central region of the leadframe, where it provides hermetic sealing and mechanical support. This localized application of the package body enhances hermeticity without requiring complex overall device design.

Inventive Principle:

Principle #3Local quality

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 enables better heat extraction and thermal performance, allowing for higher power handling and improved optical quality with enhanced mechanical stability and hermeticity, suitable for high-power LED applications.

Implementation Method 1

The leadframe is placed into a mold having a mold cavity, and a thermoset precursor material is dispensed into the mold cavity. Pressure is applied to the mold, and the thermoset precursor material is cured to form a thermoset package body on the leadframe.

Methodology Applied

Scientific EffectThermoset material properties:

Implementation Method 2

A solid state light emitting device may be, for example, an organic or inorganic light emitting diode (LED). Some packages for light emitting diodes are described in U.S. Pre-grant Publication Nos. 2004/0079957, 2004/0126913, and 2005/0269587 which are assigned to the assignee of the present invention, and which are incorporated herein by reference as if set forth fully herein.

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS8941134B2Leadframe-based packages for solid state light emitting devices having heat dissipating regions in packaging

Publication Date: 2015.01.27 CREELED INC

AI summary

A modular package for a light emitting device includes a leadframe including a first region having a top surface, a bottom surface and a first thickness and a second region having a top surface, a bottom surface and a second thickness that is less than the first thickness. The leadframe further includes an electrical lead extending laterally away from the second region, and the package further includes a thermoset package body on the leadframe and surrounding the first region. The thermoset package body may be on both the top and bottom surfaces of the second region. A leak barrier may be on the leadframe, and the package body may be on the leak barrier. Methods of forming modular packages including thermoset package bodies on leadframes are also disclosed.