LED Surface Mount Device Lead Frame Thermal Management

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Solution Overview

Problem

Existing surface mount devices (SMDs) in LED displays face challenges with color fidelity and heat dissipation, particularly at wider viewing angles and increased temperatures, due to reflective materials and insufficient heat dissipation through conventional lead structures.

Innovation Solution

The use of a lead frame with an electrically conductive LED chip carrier and separate connection parts, housed in a black casing with a thermally conductive material, where LEDs are arranged in a linear configuration to enhance color fidelity and heat dissipation, with the casing designed to minimize glare and reflection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If conventional lead structures are used for heat dissipation, then the device structure remains simple, but the heat dissipation effectiveness is insufficient

Engineering Contradiction:

Improveheat dissipation effectivenessVSAvoiddevice structure complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The lead frame is divided into functionally distinct segments: a chip carrier portion for mounting LEDs, separate connection portions for electrical connection, and an extended heat dissipation portion with increased mass and surface area. This segmentation allows each part to optimize its specific function while maintaining overall structural integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The heat dissipation structure extends in multiple dimensions beyond the conventional lead configuration. The lead frame includes extended portions that protrude from the casing in directions optimized for thermal radiation and convection, adding spatial dimensions to the heat dissipation function.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Ease of manufacture

If reflective materials are used in LED packaging, then the manufacturing process is simplified, but color fidelity deteriorates due to unwanted light reflection and glare

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidcolor fidelity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The casing is designed with a black color specifically to minimize light reflection and improve color fidelity. This color choice absorbs unwanted reflected light that would otherwise interfere with the perceived color accuracy of the LED display, directly addressing the color fidelity issue while maintaining manufacturing simplicity.

Inventive Principle:

Principle #32Color changes

3Illumination intensity

If high intensity LEDs are used to increase brightness, then illumination intensity improves, but heat generation increases making heat dissipation more difficult

Engineering Contradiction:

ImproveLED brightnessVSAvoidheat dissipation difficulty

Core Design Contradiction:

Illumination intensityVSTemperature

Solution Approach 1:

The patent converts the harmful heat generated by high-intensity LEDs into a manageable thermal management challenge by designing an integrated lead frame that serves dual purposes: electrical connection and active heat dissipation. The extended lead portions with increased mass and surface area transform the heat problem into a controlled thermal conduction and radiation system.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 improves color fidelity over a wide range of viewing angles and effectively dissipates heat, reducing the risk of premature component failure while minimizing unwanted light reflection and glare.

Implementation Method 1

a black casing that at least partially encases the lead frame

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 2

the casing designed to minimize glare and reflection

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

a linear array of LEDs adapted to be energized to produce in combination a substantially full range of colors

Methodology Applied

Scientific EffectLight emitting diode effect: Light Emitting Diode

Data Source

PatentUS8049230B2Apparatus and system for miniature surface mount devices

Publication Date: 2011.11.01 CREELED INC

AI summary

In one embodiment, a surface-mount device comprises a casing having opposed, first and second main surfaces, side surfaces, and end surfaces. A lead frame partially encased by the casing comprises (1) an electrically conductive LED chip carrier part having a surface carrying a linear array of LEDs adapted to be energized to produce in combination a substantially full range of colors, each LED having a first electrical terminal and a second electrical terminal, the first terminal of each of the LEDs being electrically and thermally coupled to the chip carrying surface of the chip carrier part; and (2) electrically conductive connection parts separate from the chip carrier part, each of the connection parts having a connection pad, the second terminal of each of the LEDs being electrically coupled to the connection pad of a corresponding one of the connection parts with a single wire bond. The linear array of LEDs extends in a first direction, and each of the chip carrier part and connection parts has a lead. The leads may be disposed in parallel relationship with each other and extend through the end surfaces of the casing in a second direction, the second direction being orthogonal to the first direction. An array of the surface-mount devices may be used in an LED display such as an indoor LED screen.