Semiconductor Light Emitting Device Lead Frame Heat Dissipation
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Solution Overview
Problem
Conventional semiconductor light emitting devices face challenges in reducing thickness while effectively dissipating heat from the LED chip, as increasing the thickness of the lead frame to enhance heat dissipation results in an overall larger device size.
Innovation Solution
A semiconductor light emitting device design featuring a lead frame with a constant thickness, including a die bonding pad and an elevated portion that allows for efficient heat dissipation by exposing the reverse surface of the die bonding pad from the case, enabling the device to be reduced in thickness and facilitating easy bending for forming the elevated portion and wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the thickness of the first frame element is increased to promote heat dissipation from the LED chip, then heat dissipation performance is improved, but the entire size of the semiconductor light emitting device increases
Solution Approach 1:
The invention transitions from increasing thickness in the vertical dimension to creating an elevated portion that extends in the horizontal dimension. The lead frame maintains constant thickness but forms an elevated portion shifted from the die bonding pad, providing heat dissipation surface area without increasing overall device thickness.
Solution Approach 2:
The lead frame is segmented into distinct functional portions: a die bonding pad for mounting the LED chip and an elevated portion for heat dissipation. This segmentation allows each portion to perform its specific function optimally without compromising the other, resolving the contradiction between heat dissipation and device thickness.
2Temperature
If the lead frame thickness is increased to improve heat dissipation, then thermal management is improved, but the device becomes more complex and harder to manufacture
Solution Approach 1:
The invention changes the geometric parameters of the lead frame by forming an elevated portion with specific dimensions (shifted position, height, and area) rather than uniformly increasing thickness. This parameter change achieves heat dissipation improvement while maintaining manufacturing simplicity through a constant thickness design.
3Length of stationary object
If the lead frame is made thinner to reduce device size, then device thickness is reduced, but heat dissipation capability deteriorates
Solution Approach 1:
The invention compensates for reduced vertical thickness by creating horizontal extension through the elevated portion. The heat dissipation function is achieved in the horizontal plane rather than relying on vertical thickness, thus reducing device thickness while maintaining or improving heat dissipation capability.
Solution Approach 2:
The elevated portion acts as an additional heat dissipation structure that copies the thermal management function of a thicker frame. By creating this separate elevated portion, the device achieves heat dissipation equivalent to a thicker design without actually increasing thickness.
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 design allows for efficient heat dissipation and reduced device thickness, while maintaining the functionality of the semiconductor light emitting device, including enhanced light directivity through the use of a light transmitting member and optional components like a zener diode.
Implementation Method 1
The light transmitting member 94 fills the space in the case 93 to cover the LED chip 92. The light transmitting member 94 is formed with a lens 94a for enhancing the directivity of the light emitted from the LED chip 92.
Implementation Method 2
Since the reverse surface of the die bonding pad on which the semiconductor light emitting element is mounted is exposed from the case, heat is efficiently dissipated from the semiconductor light emitting device to the outside.
Data Source
AI summary
A semiconductor light emitting device (A) includes a lead frame (1) having a constant thickness, a semiconductor light emitting element (2) supported by the lead frame (1), a case (4) covering part of the lead frame (1) and a light transmitting member (5) covering the semiconductor light emitting element (2). The lead frame (1) includes a die bonding pad (11a) and an elevated portion (11b). The die bonding pad (11a) includes an obverse surface on which the semiconductor light emitting element (2) is mounted, and a reverse surface exposed from the case (4). The elevated portion (11b) is shifted in position from the die bonding pad (11a) in the direction normal to the obverse surface of the die bonding pad (11a).