Thermal Print Head COF Structure with Low-Profile Protective Resin
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Solution Overview
Problem
Existing thermal print heads (TPHs) face issues of low productivity due to quality problems during wire bonding, large protective resin areas, and gaps between ceramic substrates and printed circuit boards, as well as paper jamming caused by protruding resin.
Innovation Solution
A TPH with a Chip on Film (COF) structure that minimizes the height of the protective resin by using thermocompression bonding with an anisotropic conductive film (ACF), positions the driving IC on the bottom surface, and accommodates electronic components within a heat sink groove, reducing upward protrusions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wire bonding method is used to install driving IC, then electrical connection can be achieved, but productivity is low due to quality problems during wire bonding
Solution Approach 1:
The patent replaces the wire bonding mechanical process with a chip mounting process. The driving IC is mounted directly onto the ceramic substrate using conventional chip mounting techniques rather than wire bonding, eliminating the quality issues and productivity limitations associated with wire bonding operations.
Solution Approach 2:
The patent introduces a protective resin layer as an intermediary that encapsulates the driving IC and provides both mechanical protection and electrical insulation. This allows the driving IC to be mounted in a different orientation (facing downward) while still providing necessary protection and maintaining electrical connections through the resin medium.
2Ease of manufacture
If driving IC is installed on top surface of ceramic substrate, then electrical connection is achieved, but protective resin area becomes large and causes paper jamming
Solution Approach 1:
The patent inverts the conventional mounting orientation by placing the driving IC on the bottom surface of the ceramic substrate rather than the top surface. The driving IC faces downward toward the heat sink, which eliminates the need for large protective resin areas that would protrude upward and cause paper jamming during printing operations.
Solution Approach 2:
The patent changes the spatial dimension of IC mounting from the top surface (vertical dimension) to the bottom surface (horizontal dimension relative to printing direction). This dimensional repositioning allows the protective resin to be contained within the substrate thickness rather than protruding into the paper path.
3Length of stationary object
If driving IC is mounted on ceramic substrate, then electrical connection is achieved, but gap between ceramic substrate and printed circuit board increases
Solution Approach 1:
The patent merges the driving IC mounting location with the heat sink interface by positioning the IC on the bottom surface of the ceramic substrate, adjacent to where the heat sink contacts the substrate. This integration allows the IC to be housed within the heat sink structure, eliminating gaps and improving structural compactness.
Solution Approach 2:
The patent implements nesting by placing the driving IC within the heat sink structure. The heat sink serves as a container that houses both its thermal function and the electronically function, with the driving IC positioned in the space between the ceramic substrate bottom surface and the heat sink top surface.
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
Improves productivity by minimizing the protective resin step and preventing paper jams, while maintaining efficient thermal energy transfer and reducing the overall size of the TPH.
Implementation Method 1
thermocompression bonding with an anisotropic conductive film (ACF)
Implementation Method 2
thermocompression bonding with an anisotropic conductive film (ACF)
Implementation Method 3
a heat sink 16 attached to the lower part of the ceramic substrate 11 and the printed circuit board 12 to release heat
Implementation Method 4
a heat sink 16 attached to the lower part of the ceramic substrate 11 and the printed circuit board 12 to release heat
Implementation Method 5
a heating element 11a made of heating resistors
Implementation Method 6
the heat generated from the heating resistor is heated to a thermal paper so that printing can be accomplished
Data Source
AI summary
The thermal print head having COF structure is disclosed. According to the present invention, productivity can be improved with a low step of a protective resin by using a COF method, the height of the thermally compressed COF can be minimized in comparison with the surface of the ceramic substrate by electrically connecting the ceramic substrate and the COF through thermal compression using ACF, and the height of the thermally compressed COF can be minimized in comparison with the surface of the ceramic substrate.