Thermal Print Head Wiring Layout for Dense Electrodes
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Solution Overview
Problem
The challenge of reducing short circuits and disconnection in high-definition thermal print heads due to densely integrated wiring, and the difficulty in forming high-definition wiring patterns due to solvent spreading in metal paste used for electrode formation, leading to reduced manufacturing yield.
Innovation Solution
A thermal print head design featuring a substrate with convex parts, a wiring layer, a heat storage layer, and electrodes arranged to allow for high integration without folded shapes, combined with a manufacturing method using silicide and single crystal semiconductor to form connections and electrodes, and a heat storage layer with a porous layer to prevent solvent spreading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pitch between wiring is reduced to increase integration density for high-definition printing, then printing definition is improved, but short circuits and disconnection of wiring occur more frequently
Solution Approach 1:
The patent transitions from planar wiring layout to three-dimensional stacked wiring layers. Multiple wiring layers are formed at different heights, allowing electrical connections to route vertically through insulating layers. This spatial reconfiguration enables reduced pitch in the horizontal plane while maintaining adequate separation between conductors through vertical stacking, thus achieving high-definition printing without compromising wiring reliability.
Solution Approach 2:
The wiring structure is divided into multiple discrete layers separated by insulating materials. Each wiring layer contains specific conductive paths, and connections between layers are established through vertical vias or contact holes. This segmentation allows independent optimization of each layer's routing, reduces interference between adjacent wires, and enables higher integration density while maintaining signal integrity and reducing short circuit risks.
2Ease of manufacture
If metal paste with solvent is used for screen-printing wiring patterns, then electrode formation is simplified, but the wiring pattern spreads beyond the designed pattern
Solution Approach 1:
A barrier layer is introduced as an intermediary between the metal paste and the underlying substrate. This barrier layer has low solvent permeability and prevents the solvent in the metal paste from penetrating into the substrate, thereby preventing unwanted spreading of the wiring pattern. The barrier layer allows the screen-printing process to remain simple while achieving precise pattern definition, as the solvent is contained within the paste application zone.
3Productivity
If wiring is integrated more densely to enable high-speed high-volume printing, then printing speed and productivity are improved, but manufacturing yield is significantly reduced
Solution Approach 1:
The patent employs multiple stacked wiring layers to achieve high integration density. By routing signals through vertical channels and utilizing three-dimensional space, the design accommodates higher wiring density without increasing the horizontal footprint. This enables high-speed printing capability while maintaining adequate wiring separation and reducing manufacturing defects, thus improving both productivity and manufacturing yield simultaneously.
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 high-definition printing with reduced electrode pitch and improved manufacturing yield by preventing solvent spread and allowing for dense electrode integration.
Implementation Method 1
a heat storage layer with a porous layer to prevent solvent spreading
Implementation Method 2
the exposed part (the heating part) of the resistor layer generates heat due to Joule heat
Data Source
AI summary
Provided is a thermal print head including: a substrate having a convex part thereon; a wiring layer over the convex part; a heat storage layer over the wiring layer; a heating resistive part that is formed over the heat storage layer and is arranged along a main scanning direction; a first electrode in contact with the heating resistive part on one side in a sub-scanning direction; a second electrode in contact with the heating resistive part on another side in the sub-scanning direction; and a connection wiring formed in an opening that passes through the heating resistive part and the heat storage layer and reaches the wiring layer, in which the first electrode is electrically connected to the wiring layer via the connection wiring.