SAW Device Pillar Terminal Corrosion Protection
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Solution Overview
Problem
Acoustic wave devices with wafer level packages face corrosion issues at the connection portion between terminals and electrode pads due to peeling caused by heat expansion differences, leading to moisture invasion and corrosion.
Innovation Solution
The acoustic wave device incorporates a substrate with an excitation electrode, electrode pads, pillar-shaped terminals, and conductive projections extending from the terminals' side surfaces, covered by a frame and lid structure to protect the excitation electrode and prevent moisture ingress, along with a manufacturing process involving plating and resist layer deposition to form metal connections and terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a terminal part is exposed from the second sealing part to enable electrical connection, then ease of operation is improved, but reliability deteriorates due to peeling and moisture invasion
Solution Approach 1:
The patent introduces a cover as an intermediary component that bridges the terminal part and the external environment. The cover includes a through-hole for electrical connection while providing protective coverage over the terminal part, preventing direct exposure to moisture while maintaining connectivity functionality
Solution Approach 2:
The patent transitions from a two-dimensional sealing surface to a three-dimensional protective structure. The cover is positioned above the main surface at a height that allows it to overlook and protect the terminal part, creating a spatial barrier against moisture invasion while maintaining electrical access
2Reliability
If the terminal part is covered completely to prevent moisture ingress, then reliability is improved, but ease of operation deteriorates due to reduced accessibility
Solution Approach 1:
The cover is segmented with a through-hole that selectively opens only the necessary portion for electrical connection while maintaining coverage over the rest of the terminal part. This segmentation allows the cover to simultaneously provide protection and accessibility without compromising either function
3Reliability
If the bonding area between terminal and electrode pad is increased to prevent peeling, then reliability is improved, but device complexity increases
Solution Approach 1:
The manufacturing process includes preliminary plating steps where a plating foundation layer is formed on the frame part and electrode pad before terminal assembly. This preliminary metallurgical bonding creates strong adhesion between the terminal and substrate, preventing peeling without requiring complex mechanical fastening structures
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 suppresses corrosion at the terminal and electrode pad connection, enhancing the reliability and durability of the acoustic wave device by increasing the bonding area and preventing moisture from reaching the sensitive areas.
Implementation Method 1
a step of depositing metal on the plating foundation layer exposed from the resist layer by plating
Data Source
AI summary
A SAW device (1) has a substrate (3) configured to propagate acoustic waves; an IDT electrode (15) on a first main surface (3a) of a substrate (3); and an electrode pad (13) on the first main surface (3a) electrically connected to the IDT electrode (15). The SAW device (1) also has a terminal with a pillar-shape (column part (7z)) setted up on the electrode pad (13); a third conductive layer (39) extending from a side surface of the column part (7z); and a cover (5) forming a vibration space (S) above the IDT electrode (15) and covering the side surface of the column part (7z), and the third conductive layer (39).