Transparent LED Laminate Bonding for Flex and Heat-Cycle Reliability
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Solution Overview
Problem
Flexible light-transmissive light-emitting devices used in applications like vehicle windows face reliability issues under varying temperatures and repetitive stresses, with existing methods leading to cracks, breakages, and poor resistance to bending and heat cycles, limiting their practical utility.
Innovation Solution
A light-emitting device design featuring a light-transmissive elastomer between an LED chip and a light-transmissive electroconductive layer, with the elastomer filling concavities and unevenness on the electrode surfaces, and subjected to vacuum hot pressing to enhance adhesion and mechanical junction, preventing cracks and ensuring reliable electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wirebonding method is used to connect electrodes to light-transmissive electroconductive layers, then electrical connection is achieved, but the device cannot be made transparent and flexibility is lost
Solution Approach 1:
The patent extracts and eliminates the wirebonding method from the device structure, replacing it with a direct bonding approach between electrodes and light-transmissive electroconductive layers. This removal of the wirebonding component enables device transparency while maintaining electrical connection through alternative means such as conductive adhesives or direct metallurgical bonding.
Solution Approach 2:
The patent introduces light-transmissive electroconductive layers as intermediary elements between the electrodes and the external circuit. These layers serve as both electrical conductors and transparent windows, eliminating the need for opaque wirebonding while maintaining electrical connectivity. The intermediary layer approach allows light transmission and mechanical flexibility.
2Adaptability or versatility
If flexible light-transmissive light-emitting device is made with conventional structures, then flexibility and transparency are achieved, but reliability under temperature variations and repetitive stresses is insufficient
Solution Approach 1:
The patent employs flexible thin film structures for the light-transmissive electroconductive layers and encapsulation materials. These thin films are designed with appropriate thickness and material composition to provide both flexibility for bending applications and sufficient mechanical strength to withstand repetitive stresses and temperature variations without delamination or cracking.
Solution Approach 2:
The patent utilizes composite material structures combining different materials with complementary properties. The device integrates light-transmissive electroconductive layers, flexible substrates, encapsulation materials, and LED chips into a composite structure where each material is selected for its specific properties (electrical conductivity, transparency, flexibility, thermal stability) to collectively enhance reliability under environmental conditions.
3Reliability
If pressure is applied during production to ensure contact, then electrical connection is improved, but cracks and breakages occur in the light-transmissive conductive layer
Solution Approach 1:
The patent applies beforehand cushioning by introducing compliant intermediate layers or buffer structures between the rigid electrodes and the fragile light-transmissive conductive layers. These cushioning elements absorb and distribute applied pressure during production, preventing stress concentration that would cause cracks in the conductive layers while still ensuring adequate electrical contact.
Solution Approach 2:
The patent modifies process parameters such as reducing pressing force, controlling temperature profiles, and adjusting bonding time during manufacturing. By optimizing these parameters, the device achieves reliable electrical connection without applying excessive pressure that would damage the light-transmissive conductive layers. The parameters are tuned to balance contact quality with structural integrity.
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 provides a light-emitting device with improved flexural resistance and heat-cycle characteristics, preventing cracks and breakages, ensuring persistent lighting under severe conditions and maintaining reliable electrical connections.
Implementation Method 1
the light-transmissive elastomer filling concavities and unevenness on the electrode surfaces
Implementation Method 2
subjected to vacuum hot pressing to enhance adhesion and mechanical junction
Implementation Method 3
subjected to vacuum hot pressing
Data Source
AI summary
A light-emitting device includes a pair of light-transmissive insulator sheets disposed opposite to each other and two types of light-transmissive electroconductive layers disposed on a common one of or separately on one and the other of the pair of light-transmissive insulator sheets, and at least one light-emitting semiconductor each provided with a cathode and an anode which are individually and electrically connected to the two types of the light-transmissive electroconductive layers. The electrical connection and mechanical bonding between the members are improved by a light-transmissive elastomer which is between the pair of light-transmissive insulator sheets. A method in which a light-emitting semiconductor element and a light-transmissive electroconductive member are subjected to vacuum hot-pressing.