Coil Device Sn Amount Control Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing coil devices with surface-mounted electrodes face bonding issues due to the low melting point of Sn, leading to deterioration and disconnection during reflow, especially at the connecting wire faces, which affects the reliability and durability of the bonding between the winding coil, electrodes, and magnetic parts.
Innovation Solution
The coil device incorporates a winding coil with a magnetic part covering the connecting wire face, where the Sn amount per unit area is less than at the mounting base, preventing Sn melting and alloy-related bonding deterioration, and features a conductive connecting wire part with a separate conductor piece to enhance bonding reliability and reduce stress on the magnetic part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic part covers the connecting wire face, then durability and reliability are improved, but stress is applied to the bonding part between extension line part and connecting wire face
Solution Approach 1:
The magnetic part is designed to cover only specific areas (winding coil and mounting base face) while deliberately leaving the connecting wire face exposed. This localized coverage provides protection and magnetic functionality where needed while avoiding stress concentration on the vulnerable bonding parts of the connecting wire face.
2Ease of operation
If extension line part is pulled out excessively from winding part, then connecting wire face can be accessed, but bonding condition deteriorates due to increased stress
Solution Approach 1:
The electrode structure utilizes three-dimensional spatial arrangement by projecting the connecting wire face outward from the base part in a direction opposite to the mounting base face. This dimensional positioning allows the connecting wire face to be easily accessible for wire bonding operations while maintaining optimal bonding conditions without excessive pulling of the extension line part.
Data Source
AI summary
A coil device comprising a winding coil including Cu and having a winding part and an extension line part which is pulled out from said winding part, a pair of electrodes made of a conductive material having a base part provided with a mounting base face at one of the face, and a connecting wire part having a connecting wire face connected with the extension line part and said connecting wire part projects out towards an opposite side of said mounting base face with respect to the base part, a magnetic part including a magnetic material and said magnetic part uncovering said mounting base and covering at least said winding part and said connecting wire face, wherein Sn amount per unit area of said connecting wire face is less than Sn amount per unit area of said mounting base.