Flexible Substrate Dummy Conductors for Bonding Deformability
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Solution Overview
Problem
The challenge lies in securely mounting semiconductor chips on flexible wiring boards due to the deformability differences between dense-wire and sparse-wire regions, which affects the bonding conditions and stability of the chip on the board.
Innovation Solution
A multilayer substrate with a flexible element assembly featuring external electrodes and dummy conductors, where the dummy conductors are strategically placed in areas with radii greater than the average distance between electrodes, ensuring consistent deformability and improved bonding by ultrasonic bonding of the electrodes to the chip bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic vibration is applied to bond bumps to wires on a flexible wiring board, then bonding is achieved, but the deformability difference between dense-wire and sparse-wire regions causes inconsistent bonding conditions
Solution Approach 1:
The patent applies local quality by introducing dummy wires specifically in sparse-wire regions to balance the deformability characteristics. The dummy wires are positioned at locations where the distance to adjacent wires exceeds the average distance, creating localized structural modifications that compensate for regional deformability differences without affecting dense-wire regions
Solution Approach 2:
The patent changes the structural parameter of the flexible wiring board by adding dummy wires with specific spacing relationships. The dummy wires are positioned such that their distance to adjacent wires is controlled to match or exceed the average wire distance, thereby modifying the local deformability parameter to achieve uniformity across different regions
2Adaptability or versatility
If the flexible wiring board is made deformable for flexibility, then adaptability is improved, but mounting security of semiconductor chips deteriorates due to inconsistent deformation across regions
Solution Approach 1:
The patent maintains overall flexibility while improving mounting security by applying local quality modifications through dummy wires. These dummy wires are strategically placed in sparse-wire regions to create localized deformability balance, allowing the board to remain flexible overall while providing consistent bonding conditions at mounting locations
Solution Approach 2:
The patent applies preliminary action by pre-positioning dummy wires in the flexible wiring board before semiconductor chip mounting. This preliminary structural adjustment ensures that when ultrasonic bonding is later applied, the deformability is already balanced across regions, preventing inconsistent bonding conditions
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 enhances the secure mounting of components by minimizing deformability differences across the substrate, leading to more reliable bonding and improved stability of the semiconductor chip on the flexible wiring board.
Implementation Method 1
the wires and the bumps are bonded together by ultrasonic flip-chip bonding. By applying ultrasonic vibration to the semiconductor chip
Data Source
AI summary
A multilayer substrate includes a flexible element assembly including a principal surface, a first to an n-th external electrode disposed on the principal surface, and at least one first dummy conductor disposed inside the element assembly in a floating state. When the element assembly is viewed from a normal direction of the principal surface, a distance between an m-th external electrode and a nearest external electrode therefrom among the first to the n-th external electrodes is defined as a distance Dm, an average of distances D1 to Dn is defined as an average Dave, and an area within a circle having a center on the m-th external electrode and having a radius of Dm is defined as an area Am. The first dummy conductor is located in at least one area Am having a radius of Dm greater than the average Dave when viewed from the normal direction.