Nanoparticle Electrical Interconnects Across Microscopic Steps
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Solution Overview
Problem
Existing methods for forming electrical connections on micro-LEDs with lateral dimensions of 100 μm or less, such as wire-bonding, are less desirable due to the large diameters of wires required, which do not effectively traverse microscopic steps on the substrate.
Innovation Solution
A method involving the continuous extrusion of a metallic nanoparticle composition from a capillary tube while displacing it relative to the substrate to form an elongate electrical connection feature that traverses microscopic steps, comprising a first portion contacting the step bottom, a second portion extending between the step bottom and top and contacting the sidewall, and a third portion contacting the step top, with line widths in the range of 2 μm to 30 μm and step heights of at least 10 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If wire-bonding is used to make electrical connections on micro-LEDs, then electrical connections can be formed, but the wire diameter is at least 15 μm which is too large for micro-LEDs with lateral dimensions of 100 μm or less
Solution Approach 1:
The patent changes the material state from bulk metal wire to metallic nanoparticle composition, enabling continuous extrusion of conductive material with controllable line width (2-30 μm) that is suitable for micro-LED dimensions while maintaining electrical conductivity through nanoparticle aggregation and sintering
Solution Approach 2:
The electrical connection feature is formed in three distinct portions (first portion at step bottom, second portion along sidewall, third portion at step top) that are deposited sequentially, allowing each segment to be optimized for its specific function and position on the substrate topography
2Shape
If conventional wire-bonding is used, then electrical connections can be made, but the wires cannot effectively traverse microscopic steps on the substrate
Solution Approach 1:
The capillary tube is dynamically positioned and displaced during the extrusion process to follow the contour of the substrate steps, allowing the metallic nanoparticle composition to be deposited precisely along the step contours (bottom, sidewall, top) rather than requiring a fixed deposition path
Solution Approach 2:
The metallic nanoparticle composition is continuously extruded from the capillary tube throughout the entire process of traversing the step, ensuring an unbroken conductive path is formed from the step bottom through the sidewall to the step top without interruption or discontinuity
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
Enables the formation of conductive features that traverse large steps with compact line widths, improving mechanical stability and facilitating miniaturization by directly contacting the step contours, thus addressing the limitations of conventional wire-bond connections.
Implementation Method 1
continuously extruding a metallic nanoparticle composition from a capillary tube while displacing the capillary tube relative to the substrate
Data Source
AI summary
A method of forming an elongate electrical connection feature that traverses at least one step on or in a substrate is disclosed. A metallic nanoparticle composition is extruded from a capillary tube while the capillary tube is displaced relative to the substrate. The method includes: (1) continuously extruding the composition from the capillary tube while displacing the capillary tube by a height increment during a displacement period; (2) continuously extruding the composition from the capillary tube while the capillary tube is stationary during a stationary period; and (3) repeatedly executing (1) and (2) until the capillary tube is displaced from a position at a step bottom portion to another position at a height not lower than a step top portion.