Conductive Ink Solderable Surface via Partial Curing
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Solution Overview
Problem
Conductive inks used in printed electronics face challenges in creating reliable solder connections due to a thin polymer coating that hinders solder wetting and can be damaged by excessive heat or abrasion, affecting circuit reliability.
Innovation Solution
Applying a conductive paste to a partially cured conductive ink trace, comprising conductive particles and solvent, which is then fully cured to create a suitable surface for solder bonding, avoiding damage to surrounding circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conductive ink is fully cured to ensure durability, then the trace strength is improved, but solderability deteriorates due to the formation of a protective polymer coating
Solution Approach 1:
The patent applies conductive paste to the conductive ink trace before complete curing. This preliminary action allows the trace to gain sufficient structural strength while the surface remains partially uncured, creating a window of opportunity where the polymer coating is not yet fully formed to prevent solder wetting. The conductive paste is then applied to the partially cured trace, and after final curing, the combined structure provides both strength and solderability.
Solution Approach 2:
The patent creates a composite structure by combining conductive ink with conductive paste. The conductive ink provides the base trace with polymer coating, while the conductive paste (comprising conductive particles and solvent) is applied on top. This composite approach allows the underlying ink trace to provide structural integrity while the paste layer provides a solderable surface, as the paste contains conductive particles that promote solder wetting without requiring complete curing of the underlying ink.
2Reliability
If heat or abrasion is applied to remove polymer coating for soldering, then solderability is improved, but the surrounding circuits may be damaged
Solution Approach 1:
The conductive paste acts as an intermediary layer between the conductive ink trace and the solder. Instead of directly applying heat or abrasion to the polymer-coated ink trace (which would damage surrounding circuits), the paste is applied first as a mediator. This paste layer contains conductive particles that facilitate solder wetting without requiring aggressive removal of the underlying polymer coating. The paste serves as a protective intermediary that enables soldering while preventing harmful effects from reaching the surrounding circuits.
Solution Approach 2:
The patent changes the surface properties of the conductive ink trace by applying conductive paste before final curing. This parameter change modifies the surface chemistry and conductivity characteristics, creating a solderable surface without altering the underlying polymer coating structure. The paste application changes the surface energy and conductivity parameters, enabling solder wetting while the intact polymer coating continues to protect the trace from environmental factors and prevents the need for aggressive heat or abrasion treatment.
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 reliable solder connections without damaging surrounding circuits by enhancing solderability and connectivity, ensuring consistent conductivity.
Implementation Method 1
a conductive paste comprising conductive particles
Implementation Method 2
curing the partially cured conductive ink trace and the conductive paste
Data Source
AI summary
Applying a solderable surface to conductive ink may include partially curing a conductive ink trace; applying, to the partially cured conductive ink trace, a conductive paste comprising conductive particles; and curing the partially cured conductive ink trace and the conductive paste.