Wafer-Level Package Cavities for Dense Acoustic Interconnect Layout
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Solution Overview
Problem
Current wafer level packages require excessive space due to safety distances needed for process errors and fluctuations, leading to sub-optimal space usage and reduced active filter and interconnect areas.
Innovation Solution
A wafer level package design that minimizes space usage by using a substrate with a top functional layer, a first package layer forming domes over cavities, and a second reinforcing package layer with exposed contact areas for interconnect structures, allowing for flexible placement of interconnects without additional safety distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple safety distances are added to shield acoustics from outer influences, then protection of sensitive device structures is improved, but substrate surface area is reduced
Solution Approach 1:
The patent transitions from two-dimensional planar safety distances to three-dimensional cavity structures. By forming cavities that extend vertically through the substrate thickness, acoustic shielding is achieved in the third dimension (depth) rather than requiring excessive lateral spacing. The cavities are positioned between active regions and allow signal paths to pass through vertically, eliminating the need for large horizontal exclusion zones while maintaining acoustic isolation.
Solution Approach 2:
The cavity structures are nested within the substrate thickness, utilizing the vertical space between the top and bottom surfaces. Multiple cavities can be stacked or arranged in three-dimensional configurations within the substrate volume, maximizing the use of available space. This nesting approach allows acoustic shielding without consuming additional lateral substrate area, as the shielding structures are embedded within the existing substrate footprint.
2Manufacturing precision
If safety distances are increased to account for process errors and fluctuations, then manufacturing reliability is improved, but active filter and interconnect areas are reduced
Solution Approach 1:
The invention moves safety margins from the lateral dimension to the vertical dimension by utilizing cavity depth. The cavities extend through the substrate thickness, providing acoustic shielding that does not consume lateral space needed for active filter and interconnect structures. This allows process tolerances to be accommodated within the vertical profile rather than requiring reduced active areas.
3Area of stationary object
If interconnect structures are placed closer to sensitive device structures, then substrate surface usage is improved, but acoustic interference risk increases
Solution Approach 1:
The cavity structures serve as acoustic intermediaries or barriers between sensitive device structures and interconnect structures. The cavities are positioned to intercept and shield acoustic signals, creating a protective zone that allows interconnects to be placed closer to active regions without direct acoustic coupling. The cavity walls act as acoustic barriers that block harmful acoustic interference while permitting the closer spatial arrangement.
Solution Approach 2:
Acoustic shielding is achieved by positioning cavity structures in the vertical dimension between the top and bottom surfaces of the substrate. This three-dimensional arrangement allows interconnect structures to be placed closer to active regions in the lateral plane, as the acoustic protection is provided vertically through the cavity depth rather than requiring lateral separation distances.
Data Source
AI summary
A fullcover package solution in combination with copper pillars or solder bumps and acoustic cavities is proposed to provide maximum usable design area compared to current thin film acoustic wafer level packages. Manufacturing can be done in a self-aligned interconnection process.