SAW Filter Cavity Frame Layout for Heat Dissipation in Small Packages
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Solution Overview
Problem
The challenge in miniaturizing surface acoustic wave (SAW) filters for mobile devices is to achieve size reduction while effectively dissipating heat, as smaller devices generate higher operating temperatures, which can affect performance and lifespan.
Innovation Solution
The use of an enhanced thermally conductive cavity frame, such as diamond material with a thermal conductivity of at least 5 W/m-K, in conjunction with a co-planar cap substrate and cavity frame configuration, to improve heat dissipation and reduce the package size by aligning side walls for shorter metal interconnect paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the SAW filter package size is reduced, then the device can be miniaturized for mobile applications, but heat dissipation becomes insufficient leading to higher operating temperatures
Solution Approach 1:
The patent changes the thermal conductivity parameter of the cavity frame material from conventional materials (with thermal conductivity around 1-5 W/m-K) to diamond material (with thermal conductivity of 600-2000 W/m-K). This parameter change enables effective heat dissipation in the miniaturized package by providing a high thermal conductivity path from the IDTs through the diamond cavity frame to the cap substrate, resolving the heat dissipation issue while maintaining small package size
Solution Approach 2:
The patent employs a composite structure combining diamond material with the cap substrate and interconnect structures. The diamond cavity frame acts as a thermal interface material between the piezoelectric substrate and the cap substrate, creating a composite thermal management system that efficiently conducts heat away from the active IDT regions while maintaining the mechanical and electrical functionality of the overall package
2Manufacturing precision
If the cavity frame extends outward forming a shoulder area, then alignment tolerance is provided, but the package area increases
Solution Approach 1:
The patent inverts the conventional approach by making the cap substrate larger than the cavity frame footprint. Instead of the cavity frame extending beyond the cap substrate to provide alignment tolerance, the cap substrate extends beyond the cavity frame, providing the alignment tolerance in the opposite direction. This inversion reduces the overall package area while maintaining manufacturing feasibility through co-planar side walls
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 effectively dissipates heat, maintains performance, and reduces the SAW filter package size, addressing the issue of increased temperatures in smaller devices and enhancing the reliability of SAW filters in mobile devices.
Implementation Method 1
the cavity frame is comprised of a material that has an enhanced thermally conductivity. For example, the cavity frame may be comprised of a diamond material to provide a diamond cavity frame. As another example, the cavity frame may be comprised of a material that has a thermal conductivity of at least five (5) Watts (W) per meter (m)-Kelvin (W/m-K). In this manner, heat generated in the SAW filter package can more effectively be dissipated
Data Source
AI summary
Surface acoustic wave (SAW) filter packages employing an enhanced thermally conductive cavity frame for heat dissipation, and related fabrication methods are disclosed. The SAW filter package also includes a cavity frame comprising a perimeter structure and a cavity inside the perimeter structure coupled to a substrate of a piezoelectric material that contains interdigital transducers (IDTs). A cap substrate is disposed on the perimeter structure of the cavity frame to enclose an air cavity inside the perimeter structure between a substrate and the cap substrate. In exemplary aspects, to effectively dissipate heat generated in the SAW filter package to maintain the desired performance of the SAW filter, the cavity frame is comprised of a material that has an enhanced thermal conductivity. The heat generated in the SAW filter package can more effectively be dissipated, particularly at edges and corners of the cavity frame where hot spots can particularly occur.