Ultrasonic Bonding Device Step Wall Positioning for Small Pitch Wiring
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Solution Overview
Problem
The increasing small pitch interval of wiring patterns in electronic connections leads to short-circuit failures in existing anisotropic conductive film (ACF) techniques, and there is a need for reliable bonding methods that can handle short bonding lengths and large display sizes, such as in smartphones.
Innovation Solution
An ultrasonic bonding device with a stage featuring a step wall surface allows for precise positioning and bonding of flat members, using an ultrasonic horn to press a laminated portion at the step wall surface, ensuring reliable electrical connections without short-circuit failures, even with small pitch intervals and large widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If anisotropic conductive film (ACF) is used for wiring connection, then electrical connection can be achieved, but short-circuit failure occurs when pitch interval is small
Solution Approach 1:
The patent replaces the ACF-based mechanical/electrical connection system with an ultrasonic bonding system that uses mechanical vibration to directly bond metal wiring patterns. The ultrasonic horn applies high-frequency vibrations to create solid-phase bonding between metal surfaces, eliminating the need for ACF and preventing short-circuit failures that occur with small pitch intervals in ACF-based connections.
Solution Approach 2:
The patent changes the bonding mechanism from chemical/adhesive-based (ACF) to physical/mechanical-based (ultrasonic vibration). By applying ultrasonic vibrations at specific frequencies and amplitudes, the metal surfaces undergo solid-phase bonding through localized plastic deformation and metallurgical bonding, enabling reliable connections at small pitch intervals without short-circuit risks.
2Area of stationary object
If display size is increased, then screen area is enlarged, but bonding length must be shortened leading to connection reliability problems
Solution Approach 1:
The ultrasonic bonding system replaces traditional bonding methods with a mechanism that generates intense localized mechanical vibrations at the bonding interface. This creates strong metallurgical bonds over very short bonding lengths, enabling reliable electrical connections even when the display area is large and the available bonding length is limited.
3Productivity
If wiring pitch interval is reduced, then circuit integration is improved, but positioning precision must be increased to prevent short-circuit failure
Solution Approach 1:
The patent segments the bonding process into precise positional stages using the step wall surface as a reference. The first flat member is positioned on the lower-side surface with its edge aligned to the step wall, while the second flat member is positioned on the higher-side surface. This segmentation provides automatic mechanical positioning that ensures accurate alignment even with small pitch intervals, eliminating the need for complex positioning systems.
4Ease of operation
If step wall surface is added for positioning, then positioning ease is improved, but device complexity increases
Solution Approach 1:
The patent introduces asymmetry into the stage structure by adding a step wall surface that creates different height levels (lower-side surface and higher-side surface). This asymmetric design provides automatic mechanical positioning through the height difference, making the bonding process easier to operate while the added structural element is minimal and integrated into the existing stage.
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 solution enables secure ultrasonic bonding of metals, ensuring reliable electrical connections without short-circuit failures, even with small pitch intervals and large widths, and supports the bonding of large displays by solid-phase bonding, enhancing connection reliability.
Implementation Method 1
an ultrasonic horn including a press part to be pressed on a laminated portion of the first flat member and the second flat member
Data Source
AI summary
An ultrasonic bonding device includes a stage and an ultrasonic horn. A first flat member and a second flat member to be bonded are placed on the stage. The ultrasonic horn includes a press part to be pressed on a laminated portion of the first flat member and the second flat member. The stage includes a lower-side surface, a higher-side surface, and a step wall surface. The first flat member is to be placed on the lower-side surface. The higher-side surface is positioned higher than the lower-side surface by a predetermined step height. The second flat member is to be placed on the higher-side surface. The step wall surface is positioned in a boundary between the lower-side surface and the higher-side surface.