Chip Stack Protection Ring for Acoustic Wave Device
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Solution Overview
Problem
Conventional packaging methods for surface acoustic wave devices, bulk acoustic wave devices, and micro-electro-mechanical devices often result in insufficient structure strength and performance degradation due to direct contact with packaging materials, which can be mitigated by forming a cavity around these devices.
Innovation Solution
A chip stack design featuring a first and second chip with metal pillars and protection rings, where the electrical devices are housed within the protection rings, creating a gap that prevents packaging material contact and enhances structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a cavity is formed around the acoustic wave device using conventional SU8 photoresist layers, then the packaging material is prevented from contacting the device, but the structure strength becomes insufficient causing the photoresist layers to concave down
Solution Approach 1:
The cavity formation process is segmented into multiple steps with different photoresist layers (first and second SU8 photoresist layers) applied at different stages. This segmentation allows each layer to serve specific functions: the first layer provides initial cavity definition while the second layer reinforces the structure, collectively preventing packaging material contact while maintaining structural integrity.
Solution Approach 2:
The first SU8 photoresist layer is applied and cured before the cavity etching process, creating a preliminary protective structure. This preliminary action establishes the cavity boundaries in advance, allowing subsequent processing steps to proceed without the photoresist layers bearing excessive mechanical loads that would cause concavity.
2Area of stationary object
If the area of the acoustic wave device is increased, then the device functionality is improved, but the cavity area increases causing insufficient structure strength
Solution Approach 1:
The protection structure utilizes composite construction with multiple SU8 photoresist layers of different thicknesses applied in sequence. The first layer has a specific thickness for initial protection, while the second layer adds additional thickness for reinforcement. This composite approach allows the structure to maintain adequate strength even as the cavity area increases with larger device dimensions.
Data Source
AI summary
A chip stack having a protection structure for semiconductor device package, which comprises a first chip and a second chip stacked with each other, wherein said first chip has a first surface, said second chip has a second surface, said first surface and said second surface are two surfaces facing to each other, wherein at least one metal pillar is formed on at least one of said first surface and said second surface and connected with the other, at least one protection ring is formed on at least one of said first surface and said second surface and having a first gap with the other, and at least one electrical device is formed on at least one of said first surface and said second surface, wherein said at least one electrical device is located inside at least one of said at least one protection ring.