Multilayer Substrate Dummy Conductor Ultrasonic Bonding Tilt
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Solution Overview
Problem
In semiconductor mounting methods, the semiconductor bare chip often tilts during bonding to a flexible wiring board due to uneven distribution of bumps and wires, leading to concentrated force in certain areas and potential breakage.
Innovation Solution
A multilayer substrate with a flexible element assembly and at least one dummy conductor in a floating state is used, where the dummy conductor is strategically placed within areas with a radius smaller than the average distance between external electrodes, preventing the component from tilting by distributing the force more evenly during ultrasonic bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic vibration is applied to bond semiconductor bare chip to flexible wiring board, then bonding is achieved, but the semiconductor bare chip tilts due to uneven force distribution in dense and sparse regions
Solution Approach 1:
The patent applies local quality by creating a dummy wire in the sparse region that has different mechanical properties (higher flexibility) compared to wires in dense regions. This local modification allows the sparse region to deform more easily during bonding, compensating for the uneven force distribution and preventing chip tilt while maintaining bonding reliability.
2Strength
If mounting apparatus presses the top surface of tilted semiconductor bare chip, then bonding pressure is applied, but force concentrates on specific areas causing chip breakage
Solution Approach 1:
The patent implements beforehand cushioning by pre-installing a dummy wire in the sparse region before the bonding process. This dummy wire acts as a cushion that absorbs and redistributes the bonding pressure, preventing excessive force concentration on the chip structure and reducing breakage risk while ensuring adequate bonding strength.
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 effectively prevents the component from tilting on the multilayer substrate, reducing the risk of breakage and ensuring stable bonding by distributing the force more evenly across the substrate.
Implementation Method 1
bumps of a semiconductor bare chip are bonded to wires of a flexible wiring board, which includes films of liquid crystal polymer, by ultrasonic flip-chip bonding. By applying ultrasonic vibration to the semiconductor chip in a direction that is substantially the same as the alignment direction of the liquid crystal polymer, the wires and the bumps are bonded together.
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 and being in a floating state. When the element assembly is viewed from a normal direction that is normal to 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 when the element assembly is viewed from the normal direction, an area within a circle with a center on the m-th external electrode and with a radius of Dm is defined as an area Am. The first dummy conductor is located in at least one area Am with a radius of Dm smaller than the average Dave when viewed from the normal direction.