Sewn Carbon Nanotube Threads for Flexible IC Interconnects
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Solution Overview
Problem
Conventional flexible integrated circuit (IC) device assembly processes are complex and expensive due to the need for multiple lithographic steps and intricate formation of copper vias, plated through-holes, and traces.
Innovation Solution
The use of carbon nanotube (CNT) threads to electrically connect components of flexible IC devices by sewing them into a substrate, similar to conventional fiber threads, simplifying the assembly process and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flexible IC device assembly processes are used, then reliable electrical connections are achieved, but the assembly process becomes complex and expensive due to multiple lithographic steps and copper via formation
Solution Approach 1:
The patent replaces the conventional lithographic and electroplating processes with a mechanical sewing process. Conductive threads are sewn through the substrate using a needle and thread mechanism, substituting the complex chemical and physical processes of copper via formation with a straightforward mechanical stitching operation. This maintains electrical connection reliability while dramatically simplifying the assembly process.
Solution Approach 2:
The patent changes the fundamental parameter of how conductive paths are created - instead of depositing metal layers through lithography and electroplating, the invention uses pre-formed conductive threads with controlled resistance and conductivity properties. This parameter change enables a simpler process while achieving the same functional outcome of reliable electrical connections.
2Reliability
If conventional flexible IC device assembly processes are used, then reliable electrical connections are achieved, but manufacturing costs increase due to intricate formation of copper vias and multiple lithographic steps
Solution Approach 1:
The sewing-based conductive thread integration replaces expensive lithographic and electroplating equipment and processes with simpler mechanical sewing equipment. This substitution maintains connection reliability while reducing manufacturing costs by eliminating the need for cleanrooms, photoresist materials, and complex plating infrastructure.
Solution Approach 2:
The patent employs conductive threads that can be mass-produced at low cost and integrated through a simple sewing process. These threads serve as disposable or replaceable interconnect elements, eliminating the need for expensive, multi-step metal deposition processes and reducing overall manufacturing costs while maintaining adequate electrical performance.
3Reliability
If conventional flexible IC device assembly processes are used, then proper interconnections are formed, but the assembly process requires multiple lithographic steps making it time-consuming
Solution Approach 1:
The mechanical sewing process creates interconnections in a single pass operation, replacing the sequential lithographic steps that require multiple cycles of coating, patterning, etching, and plating. This substitution maintains interconnection integrity through precise needle positioning and thread tension control while dramatically reducing assembly time.
Solution Approach 2:
The conductive threads are prepared and positioned in advance through the sewing process, with the needle creating precise pathways through the substrate before final connection is made. This preliminary action of creating the physical pathway ahead of time eliminates the need for subsequent alignment and deposition steps, reducing overall assembly time while ensuring proper interconnection.
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 allows for the cost-effective assembly of flexible IC devices with similar functionality to conventional packaged IC devices, leveraging the conductivity and flexibility of CNT threads to establish reliable interconnections without the need for complex lithographic processes.
Implementation Method 1
conductive threads for interconnections within a packaged IC device
Data Source
AI summary
A packaged integrated circuit (IC) device includes a flexible substrate having contact pads, an IC die mounted on the substrate and electrically connected to the contact pads, and conductive threads sewn into the substrate. The conductive threads have proximal ends electrically connected to corresponding ones of the contact pads with conductive bumps. The conductive threads eliminate the need for a complicated multi-layer substrate structure for interconnect fan-out so the substrate may be formed of a variety of materials such as cloth or paper.