Thermal Inkjet Printhead Bond Pad Electrical Isolation
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Solution Overview
Problem
Thermal inkjet printheads face reliability issues due to unwanted electrical connections between adjacent bond pads, leading to printer failures, which existing encapsulation methods like polymer and epoxy do not fully address, and modifying the bonding process to include a barrier layer complicates manufacturing.
Innovation Solution
Incorporating a dielectric layer between adjacent bond pads to achieve electrical isolation, using photolithography to create cavities and deposit SU8 primer as the dielectric material, which acts as an insulating strip and adhesion promoter, enhancing the encapsulation process with polymer and epoxy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing encapsulation methods (polymer and epoxy) are used to protect bond pads, then the bond pads are protected, but unwanted electrical connections between adjacent bond pads still occur causing reliability issues
Solution Approach 1:
A dielectric layer is introduced as an intermediary substance between adjacent bond pads to prevent unwanted electrical connections. This dielectric layer acts as a mediator that blocks electrical current while allowing the bond pads to maintain their protective encapsulation.
Solution Approach 2:
The space between adjacent bond pads is segmented by introducing a dielectric layer, effectively dividing the continuous conductive path into isolated sections. This segmentation prevents electrical current from flowing between neighboring bond pads.
2Reliability
If a barrier layer is added to the bonding process to prevent electrical connections, then electrical isolation is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The dielectric layer is combined with the existing encapsulation process, merging the electrical isolation function with the protective encapsulation step. This integration avoids adding a separate complex barrier layer process while still achieving electrical isolation.
3Manufacturing precision
If bond pads are placed closer together to increase printing resolution, then print quality improves, but the risk of electrical connections between bond pads increases
Solution Approach 1:
The dielectric layer serves as a mediator that enables closer spacing of bond pads by providing electrical isolation. This allows the bond pads to be positioned closer together for higher printing resolution while preventing harmful electrical connections through the insulating dielectric material.
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 dielectric layer effectively prevents shorting between bond pads, increasing the reliability and operational life of thermal inkjet printheads, reducing maintenance costs and ensuring effective protection of TAB connections.
Implementation Method 1
Incorporating a dielectric layer between adjacent bond pads to achieve electrical isolation
Implementation Method 2
deposit SU8 primer as the dielectric material, which acts as an insulating strip and adhesion promoter
Data Source
AI summary
A thermal inkjet printhead may include a passivation layer, a bond pad formed over the passivation layer and insulating strips of a dielectric material formed over the passivation layer on opposite sides of the bond pad.