RF Device Substrate Bonding on Rough Piezoelectric Surfaces
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing manufacturing process for radio frequency device substrates is costly and prone to substrate curvature due to high-temperature SiO2 deposition, requiring multiple complex steps for bonding a piezoelectric layer with a rough surface to a support substrate, which disrupts the planarity needed for filter operations.
Innovation Solution
A method involving a dielectric layer and a photo-polymerizable adhesive layer is used to bond a piezoelectric layer with a rough surface to a support substrate, eliminating the need for high-temperature SiO2 deposition and complex polishing steps, with bonding occurring at room temperature and using ultraviolet irradiation to polymerize the adhesive layer, thereby reducing curvature and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple successive deposition and polishing steps are used to bond the rough piezoelectric layer to the support substrate, then adhesion quality is improved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent introduces an intermediary layer between the rough piezoelectric layer and the support substrate that facilitates bonding without requiring multiple complex deposition and polishing steps. This intermediary approach maintains good adhesion while simplifying the manufacturing process.
Solution Approach 2:
The patent changes the bonding parameters by performing the bonding operation at room temperature rather than requiring high-temperature processing followed by multiple polishing steps. This parameter change simplifies the process while maintaining adhesion quality.
2Strength
If high-temperature SiO2 deposition is used to bond the piezoelectric layer to the support substrate, then bonding strength is improved, but substrate curvature increases disrupting planarity
Solution Approach 1:
The patent changes the temperature parameter from high-temperature SiO2 deposition to room-temperature bonding using a photopolymerizable adhesive. This parameter change eliminates the substrate curvature problem while maintaining bonding strength through the adhesive mechanism.
Solution Approach 2:
The patent replaces the thermal-mechanical bonding process (high-temperature deposition) with a photochemical bonding process (UV-cured adhesive). This substitution eliminates the thermal stress that causes substrate curvature while achieving strong bonding.
3Manufacturing precision
If multiple polishing steps are performed to reduce surface roughness for bonding, then bonding quality is improved, but manufacturing time and cost increase
Solution Approach 1:
The patent changes the bonding approach to work effectively with the existing rough surface morphology without requiring reduction of surface roughness through multiple polishing steps. The photopolymerizable adhesive is designed to bond effectively to the rough surface as-is, eliminating time-consuming polishing operations.
Solution Approach 2:
The patent uses a disposable photopolymerizable adhesive layer that can be applied in a single step and cured rapidly with UV light. This replaces the expensive and time-consuming multiple polishing steps, achieving bonding quality through a simpler, faster process.
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 complexity and cost of substrate manufacturing while maintaining good acoustic performance and planarity, avoiding the curvature issues associated with traditional processes.
Implementation Method 1
ensure that the surface of the piezoelectric layer located at the interface with the electrically insulating layer is sufficiently rough to allow reflection of parasitic waves in all directions (dispersion effect)
Implementation Method 2
irradiating the assembled substrate with a light flux to polymerize the adhesive layer
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
The invention relates to a method for manufacturing a substrate (7) for a radiofrequency device by assembling a piezoelectric layer (3) on a support substrate (1) by means of an electrically insulating layer, the piezoelectric layer (3) having a roughened surface (30) at the interface thereof with the electrically insulating layer, the method being characterised in that it comprises the following steps: - providing a piezoelectric substrate (3) having a roughened surface (30) for reflecting a radiofrequency wave, - depositing a dielectric layer (4) on the roughened surface (30) of the piezoelectric substrate (3), - providing a support substrate (1), - depositing a photo-polymerizable adhesive layer (2) on the support substrate, - adhesively bonding the piezoelectric substrate (3) to the support substrate (1) by means of the dielectric layer (4) and the adhesive layer (2) in order to form an assembled substrate (5), - irradiating the assembled substrate (5) with a light flux (6) in order to polymerize the adhesive layer (2), the adhesive layer (2) and the dielectric layer (4) together forming the electrically insulating layer.