Three-Layered Sealing Resin for SAW Device Bump Protection
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Solution Overview
Problem
Conventional surface acoustic wave devices are prone to electrical faults and reliability issues due to crushing of solder bumps under external pressure and temperature cycling, as they lack sufficient structural integrity in their resin and solder configurations.
Innovation Solution
A surface acoustic wave device with a three-layered sealing resin structure, where the elastic modulus of the intermediate layer is higher than the outermost layer and lower than the innermost layer, effectively reducing bump crushing and maintaining reliability under pressure and temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-layer sealing resin structure is used, then the device structure is simple and manufacturing is easy, but the bump is easily crushed under external pressure causing electrical faults
Solution Approach 1:
The sealing resin is divided into three distinct layers with different elastic moduli. The first layer (contacting the bump) has low elastic modulus to absorb pressure, the second layer has high elastic modulus to provide structural support, and the third layer (outermost) has medium elastic modulus to distribute stress. This segmentation allows each layer to perform its specific function in resisting bump crushing while maintaining overall structural integrity.
Solution Approach 2:
The sealing resin structure uses composite materials with different elastic moduli arranged in layers. By combining materials with varying mechanical properties (low, high, and medium elastic modulus), the structure achieves optimal performance in resisting external pressure and preventing bump crushing, while the composite nature provides both flexibility and strength.
2Reliability
If solder bump material is softened to improve bonding, then bonding reliability improves, but the bump becomes more susceptible to crushing under pressure
Solution Approach 1:
The first sealing resin layer with low elastic modulus acts as a cushioning layer that is applied beforehand to protect the softened solder bump. This layer absorbs and distributes the external pressure before it reaches the bump, preventing crushing while allowing the bump material to remain soft for reliable bonding to the electrode.
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 configuration prevents electrical faults and enhances reliability by distributing pressure and reducing stress on the bumps, ensuring stable operation under external pressures and temperature cycling.
Implementation Method 1
the elastic modulus of resin of the intermediate layer is higher than that of resin of the outermost layer and the elastic modulus of resin of the innermost layer is lower than that of resin of the outermost layer
Data Source
AI summary
A surface acoustic wave device having a three-layered structure of sealing resin for sealing a mounting substrate and a surface acoustic wave element in which the elastic modulus of resin of the intermediate layer is higher than that of resin of the outermost layer and the elastic modulus of resin of the innermost layer is lower than that of resin of the outermost layer. The three-layered structure of the sealing resin suppresses crush of a bump when a pressure is applied from the outside and reduces stress applied to the bump due to the change in temperature.