Elastic Wave Package Structure for Via Electrode Retention
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Solution Overview
Problem
Elastic wave devices with WLP structures face issues where via hole electrodes tend to come out due to small inclination angles of side surfaces, leading to potential separation and reduced joining strength.
Innovation Solution
Incorporating a projection portion within the cover with a projection surface extending orthogonally to the via hole electrode direction, and using an adhesive layer with a lower elastic modulus than the protective layer, which increases the joining strength and prevents electrode egress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the inclination angle of the side surface of the via hole electrode is small, then the via hole electrode can be easily manufactured, but the via hole electrode tends to come out from the frame member and cover
Solution Approach 1:
The invention transitions from a simple inclined side surface design to a three-dimensional projection portion structure. The projection portion extends in the width direction of the via hole electrode, creating a mechanical interlock with the cover that prevents extraction. This dimensional addition transforms the retention mechanism from relying solely on friction from an inclined surface to a geometric constraint that physically blocks removal.
Solution Approach 2:
The invention uses a composite structure combining the via hole electrode with the cover, where the projection portion of the electrode integrates with the cover's interior space. This composite design creates a unified structure where the electrode and cover mutually reinforce each other, preventing the electrode from being pulled out while maintaining manufacturing feasibility.
2Device complexity
If the via hole electrode has a simple columnar structure, then the manufacturing process is simplified, but the joining strength between the via hole electrode and cover is reduced
Solution Approach 1:
The projection portion is formed in advance during the via hole electrode fabrication process, before the cover is attached. This preliminary structuring of the electrode with the projection portion ready ensures that when the cover is placed, the mechanical interlock is immediately established, maximizing joining strength without requiring additional manufacturing steps.
Solution Approach 2:
The projection portion introduces a geometric feature that deviates from the simple columnar shape, creating a form that fits into the cover's receiving space. This geometric modification, while adding some complexity, provides significant improvement in joining strength through the creation of a mechanical key-and-lock type connection.
3Strength
If the cover and support are bonded with a rigid adhesive layer, then the structural strength is improved, but the via hole electrode is more likely to come out under stress
Solution Approach 1:
The invention changes the elastic modulus parameter of the adhesive layer, selecting a material with lower elastic modulus (more flexible) rather than high rigidity. This parameter change allows the adhesive to provide cushioning and stress distribution, preventing the via hole electrode from being pulled out while still maintaining adequate bond strength between the cover and support.
Solution Approach 2:
The flexible adhesive layer acts as a cushioning element that absorbs and distributes stress before it can reach the via hole electrode. This beforehand cushioning effect prevents stress concentration at the electrode-cover interface, reducing the likelihood of electrode extraction while maintaining structural integrity.
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
Effectively prevents via hole electrodes from coming out from the support and cover while maintaining or enhancing the joining strength, even under applied forces.
Implementation Method 1
the cover includes an adhesive layer bonded to the support and a protective layer provided on the adhesive layer
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate, an interdigital transducer electrode on the piezoelectric substrate, a support on the piezoelectric substrate, including a cavity, and surrounding the interdigital transducer electrode at the cavity, a cover covering the cavity and provided on the support, and a via hole electrode penetrating the cover and the support. The via hole electrode includes a projection portion projecting outward from a side surface portion when seen in a plan view. The projection portion is located within the cover.