Flexible Conductive Ink Interconnects via Segmented Solderable Inks
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Solution Overview
Problem
Conductive ink used in electronics is typically not solderable, and even solderable conductive ink lacks the flexibility and bonding strength of traditional soldered interconnects, making it difficult to create robust and flexible electronic components that can be easily attached to substrates using the reflow process.
Innovation Solution
Combining solderable and non-solderable conductive inks to create flexible and stretchable traces, with selective plating to make non-solderable ink pads solderable, allowing for the use of a reflow process to form permanent interconnects between electronic components and substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solderable conductive ink is used, then bonding strength is improved, but flexibility is reduced
Solution Approach 1:
The conductive ink system is segmented into two distinct types: solderable conductive ink for bonding areas and non-solderable conductive ink for flexible trace areas. This segmentation allows each region to have optimized properties - the solderable ink provides strong bonding at contact pads while the non-solderable ink maintains flexibility in interconnect traces, resolving the contradiction between bonding strength and flexibility.
Solution Approach 2:
Different regions of the conductive ink structure are assigned different local qualities. Contact pad areas use solderable conductive ink with high bonding strength, while interconnect trace areas use non-solderable conductive ink with superior flexibility. This local differentiation allows the overall system to achieve both strong bonding where needed and flexibility where required, eliminating the need to compromise one property for the other.
2Strength
If traditional soldering reflow process is used, then bonding strength is improved, but compatibility with conductive ink is reduced
Solution Approach 1:
The bonding approach is segmented by applying solderable conductive ink only at contact pad regions where components will be attached, while the rest of the conductive interconnects use non-solderable ink. This allows the traditional soldering reflow process to be applied locally at contact pads without requiring the entire conductive ink structure to be solderable, thus maintaining process compatibility while achieving strong bonding where needed.
Solution Approach 2:
The solderable conductive ink acts as an intermediary material at contact pads that enables the traditional soldering reflow process to work with conductive ink-based circuits. By providing a solderable surface at the interface between component leads and the conductive ink substrate, it mediates between the component soldering process and the conductive ink material properties, allowing strong bonding without requiring the entire conductive path to be solderable.
3Ease of operation
If anisotropic conductive film or paste is used, then ease of attachment is improved, but reliability is reduced
Solution Approach 1:
Instead of using expensive anisotropic conductive films or pastes that have limitations in reliability and bonding strength, the invention uses a more economical approach: applying solderable conductive ink at contact pads and using the traditional soldering reflow process. This creates permanent, reliable soldered joints that are more durable than adhesive-based methods, while still maintaining ease of attachment through automated printing and soldering processes suitable for high-volume production.
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 creation of flexible and robust electronic components that can be easily attached to substrates using a reflow process, achieving strong and reliable soldered interconnects while maintaining flexibility and scalability for high-volume production.
Implementation Method 1
a first layer of conductive ink is printed onto a substrate to form first conductive traces and first contact pads
Implementation Method 2
conductive ink is printed to fill the vias and form second conductive traces on the second surface of the substrate
Data Source
AI summary
Attaching electronic components to a substrate can be challenging in certain applications. By utilizing printed conductive ink to fill vias, one or more conductive layers may be provided, which allow for fine pin pitches or other crowded substrates to utilize multiple layers for traces connecting the contact pad to the pins of an electronic component. By applying a substrate with conductive ink and then selectively applying a solderable ink on the conductive ink, and with conductive ink filling the vias, electronic components may be attached to a substrate that provides mechanical attachment and electrical connectivity which may also be formable or flexible.