Double-Sided Flip-Chip LED on Leadframe
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Solution Overview
Problem
Existing semiconductor light emitting devices with LED dies mounted on both sides of a leadframe face challenges in light emitting efficiency due to wire shadows and complex fabrication processes, particularly when using flip-chip mounting methods.
Innovation Solution
A double-sided semiconductor light emitting device is fabricated using a batch method with two adhesive sheets and a large-sized leadframe, where LED dies are flip-chip mounted on both sides of the leadframe, allowing for a single heating step and simplified fabrication conditions, and a covering member with reflective and fluorescent components is used to enhance light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is used to connect LED dies to leadframe, then electrical connection is achieved, but light emitting efficiency decreases due to wire shadow and device size increases due to routing area requirements
Solution Approach 1:
The patent extracts and removes the wire bonding element from the system by implementing direct flip-chip mounting of LED dies to the leadframe. This eliminates the wire shadow that blocks light emission and removes the need for routing areas, thereby resolving the contradiction between achieving electrical connection and maintaining light emitting efficiency
Solution Approach 2:
The patent transitions from planar wire bonding connections to three-dimensional flip-chip mounting where LED dies are mounted upside down with direct contact to leadframe pads. This dimensional change enables electrical connection without requiring wire routing space, eliminating the trade-off between connection reliability and light emitting efficiency
2Manufacturing precision
If individual LED dies are mounted one by one on leadframe, then precise positioning is achieved, but fabrication time increases and productivity decreases
Solution Approach 1:
The patent merges multiple individual LED die mounting operations into a single batch processing step. LED dies are mounted simultaneously on both sides of the leadframe in one fabrication process, eliminating the need for sequential individual mounting and thereby significantly improving productivity while maintaining positioning accuracy through the batch mounting technique
3Reliability
If multiple heating steps are used for mounting LED dies, then reliable bonding is achieved, but fabrication process complexity increases and manufacturing time extends
Solution Approach 1:
The patent combines multiple separate heating and bonding steps into a single integrated heating process. By mounting LED dies on both sides of the leadframe simultaneously and applying heat in one step, the method achieves reliable bonding while dramatically simplifying the fabrication process and reducing manufacturing time
Solution Approach 2:
The patent performs preliminary positioning and arrangement of LED dies on both sides of the leadframe before the heating step. This preliminary action ensures that when heating is applied, the dies are already in their final positions, allowing reliable bonding to be achieved in a single heating step rather than requiring multiple heating cycles
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 improves light emitting efficiency and simplifies the fabrication process by eliminating the need for multiple heating steps and complex solder reflow processes, while increasing brightness with multiple LED dies mounted on both sides.
Implementation Method 1
a first adhesive sheet on which a plurality of LED dies are mounted, and a second adhesive sheet with which the plurality of LED dies are bonded to a leadframe
Implementation Method 2
a covering member that covers the plurality of LED dies, wherein an end portion of one of the plurality of leadframes is located in close proximity to an end portion of another one of the plurality of leadframes, forming a gap therebetween
Implementation Method 3
a covering member that covers the plurality of LED dies
Data Source
AI summary
The purpose of the present invention is to provide a double-sided light emitting type semiconductor light emitting device that can be easily fabricated even if a semiconductor light emitting element is flip-chip mounted, and to provide a fabrication process for the same. The semiconductor light emitting device has a plurality of lead frames, a plurality of semiconductor light emitting elements connected to the plurality of lead frames, and a covering member that covers the plurality of semiconductor light emitting elements. The semiconductor light emitting device is characterized in that the edge of one lead frame among the plurality of lead frames is disposed in close proximity to the edge of another lead frame so as to form a gap, and the plurality of semiconductor light emitting elements are flip-chip mounted on the front surface and rear surface of the one lead frame and the other lead frame so as to straddle the gap.