Acceleration Sensor Solder Fillet Suppression
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Solution Overview
Problem
Existing acceleration sensors face limitations in detection accuracy due to solder fillets formed during electrical and mechanical connection, which restrict movement and hinder accurate correspondence of electric charge to acceleration loads.
Innovation Solution
An acceleration sensor design featuring a stacked structure with terminal electrodes covered by a non-solder-wettable material, where the covering portion suppresses solder fillet formation, allowing for improved sensitivity and reliable connection to a circuit substrate by preventing solder fillet rise and enhancing bonding forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the acceleration sensor is electrically and mechanically connected to a circuit substrate by soldering, then reliable connection is achieved, but the solder fillet limits movement in slide direction and reduces detection accuracy
Solution Approach 1:
A resin covering portion is introduced as an intermediary material between the terminal electrode and the solder fillet. This resin layer prevents the solder fillet from directly contacting and restricting the terminal electrode, allowing the electrode to move freely in the slide direction while still maintaining electrical connection through the soldering process. The intermediary resin thus resolves the contradiction by enabling both reliable solder connection and unrestricted electrode movement for accurate detection.
2Measurement precision
If the piezoelectric layer is disposed away from the circuit substrate to avoid solder fillet limitation, then detection accuracy improves, but the structural complexity increases
Solution Approach 1:
Instead of displacing the piezoelectric layer in the vertical direction (away from the substrate), the solution moves the terminal electrode laterally by forming it on the side surface of the element body. This dimensional change allows the electrode to be positioned such that the solder fillet does not restrict its movement, while keeping the piezoelectric layer in its optimal position for detecting acceleration-induced electric charge, thus improving detection accuracy without significant structural complexity increase.
3Measurement precision
If a covering portion is formed over the terminal electrode to suppress solder fillet rise, then sensitivity improves, but the manufacturing process becomes more complex
Solution Approach 1:
The covering portion is merged with the element body structure, forming an integrated component rather than a separate assembly step. The resin covering is formed to extend from the upper surface to the side surface of the element body, creating a unified structure that suppresses solder fillet rise while maintaining manufacturing simplicity. This integration approach improves sensitivity without significantly complicating the manufacturing 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
The solution enhances the sensitivity of the acceleration sensor by preventing solder fillet-induced limitations, ensuring accurate electric charge correspondence to acceleration loads and maintaining reliable connections, thereby improving detection accuracy.
Implementation Method 1
when inertial force acts on the weight layer due to external acceleration, electric charge is generated in the piezoelectric ceramic element due to the inertial force
Implementation Method 2
a covering portion which covers the terminal electrodes and is formed of a non-solder-wettable material, wherein the covering portion covers the terminal electrode in a portion of the side surface of the element body
Data Source
AI summary
An acceleration sensor capable of improving sensitivity is provided. In the acceleration sensor, although a solder fillet is formed in a lower end of a terminal electrode exposed from a covering portion, the covering portion suppresses the rise of the solder fillet. Due to this, the operation of the acceleration sensor is not easily limited by the solder fillet, and the acceleration sensor can generate electric charge which corresponds to a load more accurately. Therefore, the sensitivity of the acceleration sensor can be improved.