Coil Component Dummy Lead Conductor Plating Growth Control
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Solution Overview
Problem
High-density mounting of surface-mounting type coil components requires preventing excessive lateral growth of the outermost turn of planar spiral conductors during electrolytic plating to maintain precise patterns and ensure desired mounting strength with minimal solder usage.
Innovation Solution
Incorporating a dummy lead conductor between the outermost turn of the planar spiral conductor and the substrate end, along with bump electrodes and external electrodes of larger area, to suppress lateral growth and enhance mounting strength during surface mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If high plating current is used for electrolytic plating to increase conductor thickness, then the conductor thickness can be made greater, but the outermost turn of the planar spiral conductor experiences excessive lateral growth causing pattern deformation
Solution Approach 1:
A dummy lead conductor is formed adjacent to the outermost turn of the planar spiral conductor before electrolytic plating. This dummy lead conductor acts as a barrier that prevents lateral growth of the plating layer at the outermost turn during high-current plating, while allowing the plating layer to grow normally on adjacent turns. This preliminary structure counteracts the harmful lateral growth effect before it occurs.
Solution Approach 2:
The dummy lead conductor serves as an intermediary element between the plating solution and the outermost turn of the spiral conductor. It intercepts the plating current and metal ions, providing a controlled interface that allows vertical growth of the plating layer while blocking lateral expansion at the outermost turn, thus mediating between the high plating current and the pattern accuracy requirements.
2Area of stationary object
If external electrodes are formed only on the chip bottom for high-density mounting, then the area occupied by the chip component can be reduced, but the mounting strength may be insufficient
Solution Approach 1:
The electrode structure transitions from a two-dimensional planar configuration to a three-dimensional vertical configuration. Bump electrodes are formed that extend vertically from the substrate surface, and external electrodes are formed on the bottom surface with areas larger than the bump electrodes. This dimensional change allows the electrodes to provide sufficient mounting strength through vertical bonding while keeping the horizontal chip area minimal for high-density mounting.
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 prevents excessive lateral growth, allows for high-precision pattern formation, and provides desired mounting strength with reduced solder usage, optimizing coil component performance for high-density mounting.
Implementation Method 1
a direct current (hereinafter, referred to as 'plating current') is passed through the seed layer, whereby metal ions in the plating solution are electrodeposited on the seed layer
Implementation Method 2
HAP uses a current higher than heretofore for electrolytic plating to quickly grow a plating layer of electrodeposited metal ions
Data Source
AI summary
A coil component includes a substrate, a planar spiral conductor formed on a top surface of the substrate, a lead conductor connected to an outer peripheral end of the planar spiral conductor, a dummy lead conductor formed on the top surface of the substrate between an outermost turn of the planar spiral conductor and an end of the substrate and free from an electrical connection with another conductor within the same plane, external electrodes and arranged in parallel with the top surface of the substrate, and a bump electrode formed on a surface of the lead conductor and connects the lead conductor with the external electrode. The external terminals have a larger area than the bump electrodes for securing a bonding strength.