Surface Acoustic Wave Package Layout for Isolation in WLCSP
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Solution Overview
Problem
In surface and boundary acoustic wave devices, capacitive coupling between signal lines increases with reduced device sizes using wafer-level chip-size packaging, leading to deteriorated isolation characteristics and VSWR.
Innovation Solution
The introduction of a support layer between the piezoelectric substrate and a cover with strategically placed interconnection lines, including cover lines and via lines, reduces capacitive coupling by minimizing the length of lines on the piezoelectric substrate and separating signal connections, thereby improving isolation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If wafer-level chip-size packaging is used to reduce device size, then device size is reduced, but capacitive coupling between signal lines increases
Solution Approach 1:
The patent moves interconnection lines from the two-dimensional piezoelectric substrate surface to the three-dimensional cover structure (top and bottom surfaces). This dimensional transition reduces capacitive coupling by physically separating signal lines that would otherwise be closely spaced on the substrate, thereby resolving the contradiction between miniaturization and capacitive coupling reduction.
Solution Approach 2:
The cover acts as an intermediary structure that carries interconnection lines away from the piezoelectric substrate. By introducing this intermediate element, the patent successfully reduces capacitive coupling between signal lines while maintaining the compact WLCSP package structure, thus resolving the technical contradiction.
2Volume of moving object
If device size is reduced, then miniaturization is achieved, but isolation characteristics deteriorate
Solution Approach 1:
By relocating interconnection lines to the cover's top and bottom surfaces, the patent creates additional spatial separation between signal lines. This dimensional reorganization improves isolation characteristics while maintaining the reduced device size, directly addressing the contradiction between miniaturization and isolation performance.
3Volume of moving object
If device size is reduced, then compactness is improved, but VSWR deteriorates
Solution Approach 1:
The cover serves as an intermediary that carries interconnection lines away from the piezoelectric substrate, reducing parasitic capacitance and improving VSWR. This allows the patent to achieve compact device size while maintaining good VSWR characteristics, resolving the technical contradiction.
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 reduces capacitive coupling, enhancing the isolation and balanced characteristics of surface and boundary acoustic wave devices, even at reduced sizes, without the need for additional resin coverage.
Implementation Method 1
capacitive coupling tends to increase. In particular, when the sizes of the devices are reduced by using a wafer-level chip-size packaging (WLCSP) structure, the capacitive coupling significantly increases
Implementation Method 2
a surface acoustic wave device includes a piezoelectric substrate 1 and a resin substrate 7 that faces the piezoelectric substrate 1. The piezoelectric substrate 1 includes a conductor pattern having an IDT (a comb-shaped electrode) 2
Data Source
AI summary
A piezoelectric substrate is joined to a cover with a support layer disposed therebetween and with a space maintained therebetween. A transmission surface acoustic wave filter and a reception surface acoustic wave filter are disposed on a major surface of the piezoelectric substrate adjacent to the cover and inside the support layer. External electrodes are provided on the side of the cover opposite to the side facing the piezoelectric substrate. The external electrodes include an antenna terminal electrically connected to the transmission surface acoustic wave filter and the reception surface acoustic wave filter, a transmission input terminal electrically connected to the transmission surface acoustic wave filter, and a reception output terminal electrically connected to the reception surface acoustic wave filter. A portion of an interconnection line that electrically connects the reception surface acoustic wave filter to the antenna terminal is disposed on the cover.