Curved Cover Member for Elastic Wave Device Resin Sealing
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Solution Overview
Problem
Existing elastic wave devices with WLP structure face challenges in fully filling the space between the mounting substrate and the cover member with mold resin due to the flat cover member design, leading to potential recessing and insufficient sealing.
Innovation Solution
The design includes a piezoelectric substrate with a pair of main surfaces, an excitation electrode, first and second support layers, and a cover member that convexly curves towards the substrate, allowing the mold resin to fill the space between the mounting substrate and the cover member, with the first support layer being thinner and narrower than the second support layer to enhance resin filling and structural support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a flat cover member is used in the elastic wave element, then the device height can be reduced, but the space between the mounting substrate and the cover member is not sufficiently filled with mold resin
Solution Approach 1:
The cover member is designed with a curved surface instead of a flat surface. Specifically, the lower surface of the cover member is curved such that it is closer to the piezoelectric substrate at the center portion and farther at the peripheral portions. This curvature creates a wedge-shaped space that allows mold resin to be sufficiently filled while maintaining compact device height.
Solution Approach 2:
The cover member exhibits different characteristics at different locations: the peripheral portions are positioned farther from the piezoelectric substrate to create space for mold resin filling, while the center portion is closer to maintain structural integrity and achieve compact height. This local variation in spacing resolves the contradiction between height reduction and sealing quality.
2Length of stationary object
If the distance between mounting substrate and cover member is narrowed to reduce device height, then the device becomes more compact, but the cover member is more prone to recessing
Solution Approach 1:
The curved lower surface of the cover member distributes mechanical stresses more effectively compared to a flat surface. The curvature provides structural reinforcement that prevents recessing while allowing the overall device height to be reduced, as the curved geometry inherently resists deformation better than flat panels of the same thickness.
Solution Approach 2:
The support layers are positioned between the piezoelectric substrate and the cover member to provide preliminary mechanical support. This prevents the cover member from recessing under subsequent operational stresses, allowing the device to maintain reduced height without compromising cover member stability.
3Ease of manufacture
If a flat cover member is used, then the manufacturing process is simpler, but the mold resin filling is insufficient and recessing occurs
Solution Approach 1:
The curved surface of the cover member can be manufactured using standard semiconductor fabrication techniques such as photolithography and etching, which are capable of creating curved profiles. The curvature is defined by a radius of curvature that is larger than the thickness of the piezoelectric substrate, making it manufacturable with conventional equipment while achieving the dual benefits of proper resin filling and recess prevention.
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 ensures sufficient filling of the space with mold resin, prevents cover member recessing, and improves the structural strength and durability of the elastic wave device.
Implementation Method 1
a piezoelectric substrate that includes a pair of main surfaces opposing each other, an excitation electrode provided on one main surface of the piezoelectric substrate
Data Source
AI summary
An elastic wave device includes an elastic wave element that includes first support layers provided on a piezoelectric substrate, a second support layer provided on the piezoelectric substrate so as to surround the first support layers when viewed in a plan view, and a cover member provided on the first support layers and the second support layer, a mounting substrate on which the elastic wave element is mounted, and a mold resin provided on the mounting substrate and sealing the elastic wave element. A thickness of each of the first support layers is less than a thickness of the second support layer. The cover member convexly curves towards the piezoelectric substrate so as to be spaced away from the mounting substrate. A space between the mounting substrate and the cover member is filled with the mold resin.