Thin-Film RF Filter Packaging for Sealed Low-Cost BAW Cavities
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Solution Overview
Problem
The existing radio frequency filter manufacturing process is lengthy and costly due to the use of conventional protective substrates like silicon, glass, or metal housing, which complicates the preparation and increases the cost of Bulk Acoustic Wave (BAW) filters, hindering large-scale application and market competitiveness.
Innovation Solution
A radio frequency filter design that replaces the conventional protective wafer substrate with a thin film structure, using a supporting electrode and seed layers made of materials like titanium, tungsten, and copper to form a protective cavity, significantly simplifying the packaging process and reducing costs by eliminating the need for gold and complex bonding techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional protective substrates (silicon, glass, ceramic, metal housing) are used to isolate and protect the filter, then the radio frequency performance index is maintained, but the preparation process becomes longer and more complex
Solution Approach 1:
The patent uses a thin film structure (10-100 nm thickness) as the protective substrate instead of conventional thick materials like silicon, glass, or ceramic. This thin film forms a protective cavity that isolates the filter while significantly simplifying the preparation process and reducing device complexity, while maintaining the necessary radio frequency performance
Solution Approach 2:
The invention extracts and eliminates the need for complex intermediate layers and materials (such as gold wafer bonding layers, TSV through-hole electrode processing) from the conventional protective substrate structure. By using a simplified thin film structure with supporting electrodes, the patent removes unnecessary process steps while retaining the protective and isolating functions
2Reliability
If conventional protective substrates with wafer bonding and deep hole electrode filling are used, then the filter is protected from external moisture and particles, but the preparation cost increases significantly
Solution Approach 1:
The thin film structure (10-100 nm) serves as both the protective barrier and the substrate, eliminating the need for expensive conventional materials like gold for wafer bonding and deep hole electrode filling. This dramatically reduces preparation cost while maintaining protection from external moisture and particles through the sealed protective cavity
Solution Approach 2:
The patent replaces expensive, complex materials (gold, silicon wafers requiring TSV processing) with a simpler, cheaper thin film structure that achieves the same protective function. The thin film with supporting electrodes provides adequate protection without requiring expensive intermediate layers or complex bonding processes
3Reliability
If gold is used for wafer bonding and electrode material in conventional protective substrates, then reliable electrical connection and sealing are achieved, but the device cost increases
Solution Approach 1:
The thin film structure itself serves as both the protective substrate and the sealing layer, eliminating the need for separate gold wafer bonding layers. The supporting electrodes integrated with the thin film provide electrical connection while the thin film provides sealing, reducing material cost while maintaining reliability
Solution Approach 2:
The invention merges the functions of the protective substrate, sealing layer, and electrode support into a single integrated thin film structure with supporting electrodes. This consolidation eliminates the need for separate gold bonding layers and intermediate structures, reducing device cost while achieving reliable electrical connection and sealing through the integrated design
Data Source
AI summary
The present disclosure provides a radio frequency filter, including: a substrate; a supporting electrode protruded on a front surface of the substrate; and a thin film structure formed on the substrate and spaced with the substrate by the supporting electrode. An end surface of a top end of the supporting electrode is in sealing contact with a front surface of the thin film structure.