XBAR Contact Pad Thermal Via Layout for Lower Thermal Resistance
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Solution Overview
Problem
Existing RF filters, particularly those using acoustic wave resonators, face challenges in efficiently handling high-frequency and wide bandwidth communications due to thermal resistance issues, which hinder their performance in next-generation communication systems.
Innovation Solution
The implementation of a Transversely-Excited Film Bulk Acoustic Resonator (XBAR) with the piezoelectric plate and bonding oxide layer removed from beneath the contact pads to create a thermal via, reducing thermal resistance between the contact bumps and the substrate, thereby enhancing heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piezoelectric plate and bonding oxide layer are kept beneath the contact pads, then electrical insulation and structural integrity are maintained, but thermal resistance between substrate and contact bumps increases
Solution Approach 1:
The contact pad structure is segmented into multiple regions: a first contact pad region with the piezoelectric plate and bonding oxide layer for electrical insulation, and a second contact pad region without these layers for thermal conduction. This segmentation allows simultaneous achievement of electrical insulation and thermal management.
Solution Approach 2:
Different regions of the contact pad structure have different properties: the first region maintains full layering for electrical insulation, while the second region removes insulating layers to create thermal pathways. This local differentiation resolves the contradiction between insulation and heat dissipation.
2Temperature
If the piezoelectric plate is removed from beneath contact pads, then substrate-to-bump thermal resistance is reduced, but electrical insulation between substrate and contact pad is compromised
Solution Approach 1:
The contact pad is divided into a first contact pad portion with the piezoelectric plate for electrical insulation and a second contact pad portion without the plate for thermal conduction. This segmentation allows the structure to simultaneously provide both electrical insulation and thermal management functions.
Solution Approach 2:
The contact pad structure is designed to perform multiple functions: the first portion provides electrical insulation while the second portion provides thermal conduction pathways. This multi-functionality resolves the contradiction between insulation and heat dissipation.
3Device complexity
If traditional acoustic wave resonators are used, then device structure is simple, but thermal management efficiency is insufficient for high-frequency applications
Solution Approach 1:
The resonator structure is segmented with specific regions having different layer configurations. The contact pad regions are divided into insulating portions and thermally conductive portions, enabling improved thermal management while maintaining the overall simplicity of the resonator structure.
Solution Approach 2:
Specific local regions of the resonator (contact pad areas) have modified properties compared to the bulk structure. The selective removal of insulating layers in certain regions creates thermal pathways without fundamentally changing the overall device architecture, thus maintaining simplicity while improving thermal management.
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 improves thermal management, reducing temperature rise and enhancing the performance of RF filters by allowing efficient heat removal, which is critical for high-frequency and wide bandwidth applications.
Implementation Method 1
A microwave signal applied to the IDT excites a shear primary acoustic wave in the piezoelectric diaphragm
Implementation Method 2
reducing substrate to contact bump thermal resistance... allowing efficient heat removal
Data Source
AI summary
An acoustic resonator device with low thermal impedance has a substrate and a single-crystal piezoelectric plate having a back surface attached to a top surface of the substrate via a bonding oxide (BOX) layer. An interdigital transducer (IDT) formed on the front surface of the plate has interleaved fingers disposed on the diaphragm, the overlapping distance of the interleaved fingers defining an aperture of the resonator device. Contact pads are formed at selected locations over the surface of the substrate to provide electrical connections between the IDT and contact bumps to be attached to the contact pads. The piezoelectric plate is removed from at least a portion of the surface area of the device beneath each of the contact pads to provide lower thermal resistance between the contact bumps and the substrate.