Ink-Jet Assembly Manufacturing via Copper-Tin Alloy Bonding
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Solution Overview
Problem
The existing methods for manufacturing ink-jet heads with piezoelectric actuators result in increased electrical resistance due to tin ions scattering over conductive adhesives, leading to higher manufacturing costs and complex procedures when tin-plating terminals for bonding.
Innovation Solution
The method involves tin-plating and copper-plating terminals on a circuit board, forming a copper-tin alloy by heating, and bonding these terminals using a thermosetting conductive adhesive, which reduces electrical resistance and eliminates the need for covering and removing protective layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If terminals of the FPC to be bonded to the piezoelectric actuator are tin-plated, then the bonding process is simplified, but tin ions scatter over the conductive adhesive forming voids, thus increasing electrical resistance
Solution Approach 1:
The patent applies different plating materials to different terminals of the same FPC. Terminals bonded to the piezoelectric actuator are tin-plated for ease of bonding, while terminals bonded to the IC chip are gold-plated to prevent tin ion scattering. This local differentiation resolves the contradiction by allowing each terminal to have the optimal plating material for its specific bonding purpose.
Solution Approach 2:
The FPC terminals are segmented into two groups with different plating treatments: tin-plated terminals for piezoelectric actuator bonding and gold-plated terminals for IC chip bonding. This segmentation allows the manufacturing process to be simplified for piezoelectric actuator connections while maintaining low electrical resistance for IC chip connections.
2Reliability
If terminals to be bonded to the piezoelectric actuator are covered to prevent tin plating, then electrical resistance is reduced, but manufacturing procedures become complicated and costs increase
Solution Approach 1:
Instead of covering terminals to prevent tin plating (the conventional approach), the patent inverts the approach by selectively applying tin plating only to terminals that need it. This eliminates the need for covering and removing protective layers, thereby reducing manufacturing complexity while maintaining low electrical resistance where needed.
Solution Approach 2:
The patent applies tin plating locally only to terminals that require it for bonding to the piezoelectric actuator, rather than covering all terminals. This selective local treatment eliminates unnecessary manufacturing steps while achieving the desired electrical resistance characteristics.
3Ease of manufacture
If all terminals are tin-plated for simplified bonding, then manufacturing cost is reduced, but electrical resistance increases due to tin ion scattering in conductive adhesive
Solution Approach 1:
The patent implements local quality differentiation by tin-plating only the terminals that require cost-effective bonding (those connected to the piezoelectric actuator), while gold-plating terminals connected to the IC chip. This selective approach reduces overall manufacturing cost compared to universal tin plating, while preventing electrical resistance issues at critical connections.
Solution Approach 2:
The patent changes the material parameter (plating type) based on the specific bonding requirements of each terminal. By adjusting the plating material parameter locally rather than uniformly, the patent achieves both cost reduction and electrical resistance control.
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
This approach lowers electrical resistance between the circuit board and piezoelectric actuator, simplifies the manufacturing process, and reduces costs by avoiding complex protective layer procedures while maintaining strong bond strength.
Implementation Method 1
forming a copper-tin alloy on a surface of the second terminal by heating the circuit board after the mounting step
Implementation Method 2
bonding the second terminal having the copper-tin alloy formed on its surface to a terminal of another board by means of a thermosetting conductive adhesive
Data Source
AI summary
A method for manufacturing a board assembly comprises the steps of: tin-plating a first terminal and a copper-made second terminal that are formed on a circuit board; mounting an electronic component on the circuit board by means of gold-tin eutectic bonding between a gold electrode of the electronic component and the tin-plated first terminal; forming a copper-tin alloy on a surface of the second terminal by heating the circuit board after the mounting step; and bonding the second terminal having the copper-tin alloy formed on its surface to a terminal of another board by means of a thermosetting conductive adhesive.