Micro-LED Bonding Structure Using Nonconductive Adhesive Contacts
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Solution Overview
Problem
The high cost and thermal stress issues associated with traditional eutectic bonding processes for micro-LEDs, which use precious metals and require high temperatures, are addressed by employing a nonconductive adhesive layer to bond LED units and driving circuits.
Innovation Solution
A nonconductive adhesive layer, such as polyimide or polydimethylsiloxane, is used to bond LED units to driving circuits, with embedded metal contacts for electrical connectivity, reducing the need for precious metals and minimizing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If eutectic bonding process with precious metals is used to bond LED units to driving circuits, then electrical connectivity is achieved, but manufacturing cost increases significantly
Solution Approach 1:
A nonconductive adhesive layer is introduced as an intermediary between the driving circuit substrate and LED units. This adhesive layer provides mechanical bonding while small metal contacts embedded within it provide the electrical connectivity pathway, replacing the need for extensive precious metal bonding layers while maintaining electrical function.
Solution Approach 2:
Instead of using precious metals throughout the entire bonding interface, metal contacts are localized to specific points where electrical connection is needed. The nonconductive adhesive material fills the remaining areas, providing mechanical support and insulation while reducing precious metal consumption to minimal necessary locations.
2Strength
If high temperature eutectic bonding is used to bond LED units with driving circuits, then bonding strength is achieved, but internal stress increases due to thermal mismatch
Solution Approach 1:
The bonding process temperature parameter is changed from high temperature (required for eutectic bonding) to low temperature (suitable for the nonconductive adhesive). This parameter change allows bonding to proceed without subjecting the semiconductor layers to thermal stress from high temperature exposure, while the adhesive material is selected to provide adequate bonding strength at the lower temperature.
3Reliability
If thick precious metals are used in eutectic bonding, then electrical connectivity is ensured, but material cost and process complexity increase
Solution Approach 1:
The complex multi-layer precious metal bonding structure is extracted and replaced with a simpler configuration: a nonconductive adhesive layer with embedded metal contacts. This extraction removes the complexity of thick metal layer deposition, patterning, and eutectic bonding processes while maintaining the essential electrical connectivity function through the simplified metal contact-adhesive structure.
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 approach lowers manufacturing costs and reduces internal stress, while maintaining electrical connectivity, by using a nonconductive adhesive layer with small metal contacts.
Implementation Method 1
The nonconductive adhesive layer bonds the substrate and the plurality of LED units
Data Source
AI summary
A method for manufacturing a light emitting diode (LED) structure is provided. A driving circuit having a plurality of contact pads is formed in a first substrate. A plurality of metal contacts is formed on the first substrate, each metal contact being located on one of the plurality of contact pads. A nonconductive adhesive layer is formed on the first substrate covering the plurality of contact pads and the plurality of metal contacts. A plurality of LED units is formed on the nonconductive adhesive layer. Each LED unit is electrically connected to one of the plurality of contact pads through one of the plurality of metal contacts.