SAW Device Package Sandwich Structure with Spacer
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Solution Overview
Problem
Conventional SAW device packaging methods are lengthy, expensive, and result in larger devices due to a two-step mounting process, which increases the size of the package and is not suitable for smaller form factor requirements in wireless communication appliances.
Innovation Solution
A device-scale packaging method using a sandwich structure with a substrate and a lid made from LiNbO3 material, where a spacer creates a vertical clearance for unobstructed surface acoustic wave propagation and prevents capillary flow of sealing materials, and a hermetic seal is formed using a two-phase seal glass system with conductive glass feed-throughs and contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-step mounting process is used (mounting piezoelectric substrate on LTCC substrate, then mounting LTCC substrate on printed circuit board), then the SAW filter can be hermetically sealed and protected, but the package size increases and manufacturing complexity increases
Solution Approach 1:
The patent combines the piezoelectric substrate mounting and hermetic sealing operations into a single integrated process. The lid is directly mounted onto the piezoelectric substrate after the SAW filter circuit is formed, eliminating the intermediate LTCC substrate step. This merging of operations reduces the overall package size while maintaining hermetic sealing through the direct lid-to-substrate connection.
Solution Approach 2:
The patent extracts and eliminates the intermediate LTCC substrate from the conventional two-step mounting process. By removing this unnecessary intermediate layer, the package footprint is reduced while the essential hermetic sealing function is achieved through the simplified direct-mount structure with lid, spacer, and sealant assembly.
2Reliability
If a two-step mounting process is used (mounting piezoelectric substrate on LTCC substrate, then mounting LTCC substrate on printed circuit board), then the SAW filter can be hermetically sealed and protected, but the manufacturing process becomes lengthy and expensive
Solution Approach 1:
The patent merges multiple manufacturing operations into a single streamlined process. The lid mounting step simultaneously achieves both the mechanical attachment and hermetic sealing functions that would otherwise require separate operations. This consolidation eliminates the intermediate LTCC substrate mounting step, reducing manufacturing cycle time and complexity while maintaining reliable hermetic sealing through the integrated lid-spacer-sealant structure.
Solution Approach 2:
The spacer is pre-formed with protrusions that extend beyond the lid edges before lid mounting. This preliminary preparation ensures proper positioning and prevents capillary flow of sealant material during the sealing operation, eliminating the need for additional positioning or sealing control steps during manufacturing, thus reducing overall process time and complexity.
3Manufacturing precision
If a spacer is formed on the lid with protrusions extending beyond edges, then capillary flow of sealant is prevented and positioning is improved, but additional manufacturing steps are required
Solution Approach 1:
The spacer is designed with localized protrusions only at specific regions where positioning and sealant flow control are needed, rather than a completely complex three-dimensional structure. This localized feature addition provides precise lid positioning and prevents capillary flow of sealant material into unwanted areas, achieving high manufacturing precision with minimal increase in structural complexity.
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 method reduces the size and cost of SAW device packages while providing a hermetic seal and minimal dimensions, allowing for efficient signal propagation and mechanical protection, thus addressing the limitations of conventional packaging methods.
Implementation Method 1
A spacer is disposed on the substrate between the lid and the SAW device, Spacing the lid and substrate apart to define a cavity therebetween to allow for unimpeded propagation of surface acoustic waves
Implementation Method 2
The spacer...prevents capillary flow of sealing materials onto the SAW device
Implementation Method 3
using conductive glass feed-throughs and a two-phase seal glass system for a hermetic seal
Implementation Method 4
using conductive glass feed-throughs and a two-phase seal glass system for a hermetic seal
Data Source
AI summary
A surface acoustic wave (SAW) device package and method for packaging a SAW device provide a surface excited device having a small footprint, low cost and fabricated according to a unique manufacturing process. A substrate including a SAW active area on a first side is bonded to another similar sized substrate with a space sufficient to allow the propagation of the SAW on a top surface of the substrate. The two substrates have similar thermal expansion coefficients such that stress from the sealing process is minimized. The two substrates are sealed using either a low melting point glass or an organic compound such that conductive pathways exist through the seal allowing the internal device to access an external electrical connection.