Thermal Print Head Bonding Pad Layout for Narrower Pad Pitch
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Solution Overview
Problem
Existing thermal print heads face challenges in reducing the pitch between bonding pads without compromising the integrity of the lead wiring portions, leading to potential breakage during etching processes, especially when using silver as the wiring material.
Innovation Solution
The thermal print head design arranges bonding pads in specific groups and rows, ensuring that lead wiring portions do not pass through opposite pads, allowing for a reduced pitch without thinning, and uses silver for the wiring layer to maintain structural integrity and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pitch between bonding pads is reduced to improve printing resolution, then the printing resolution is improved, but the lead wiring portion may break during wet etching
Solution Approach 1:
The patent transitions from a planar arrangement to a three-dimensional stacked arrangement of bonding pads. First bonding pads are arranged in a first direction, second bonding pads are arranged in a second direction perpendicular to the first direction, and third bonding pads are arranged in a third direction perpendicular to both first and second directions. This spatial arrangement in multiple dimensions allows reduced pitch between bonding pads while maintaining adequate spacing for lead wiring portions, preventing breakage during wet etching while improving printing resolution.
2Reliability
If gold is used in the wiring layer to ensure conductivity and reliability, then the electrical reliability is improved, but the manufacturing cost increases
Solution Approach 1:
The patent employs a composite wiring layer structure consisting of multiple metal layers with different properties. The wiring layer includes a first metal layer, a second metal layer, and a third metal layer, where at least one of these layers contains copper or copper alloy. This composite structure combines the high conductivity of copper with the reliability needed for thermal print head operation, achieving electrical reliability comparable to gold while significantly reducing manufacturing costs.
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
The design enables narrower pitch between bonding pads while ensuring proper electrical and mechanical stability, facilitating easier handling of current driver ICs and reducing manufacturing costs.
Implementation Method 1
a heat generator, disposed on the glaze layer and the wiring layer
Data Source
AI summary
The present disclosure provides a thermal print head. The thermal print head includes: a substrate; a glaze layer, disposed on the substrate; and a wiring layer, disposed on the glaze layer. The wiring layer includes a plurality of bonding pads. The plurality of bonding pads are divided into a plurality of groups. Each of the plurality of groups includes a first bonding pad, a second bonding pad, a third bonding pad and a fourth bonding pad. A first group of the plurality of groups is adjacent to a second group of the plurality of groups along a first direction. The second bonding pad of the first group is located between a center of the first bonding pad of the first group and a center of the third bonding pad of the first group along the first direction.