Surface-Mounted Choke Coil with Notched Electrodes for High Density Mounting
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Solution Overview
Problem
Existing surface-mounted choke coils face challenges in achieving higher mounting density and improved performance due to increased mounting area and reduced drum core volume, as well as difficulty in confirming solder fillet formation.
Innovation Solution
A surface-mounted choke coil design featuring a drum core with circular flanges and notched electrodes, where the second part of each electrode holds the solder fillet within the square area, and a heat-curing adhesive agent with controlled viscosity and hardness to suppress magnetic resistance and facilitate solder fillet confirmation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder fillet formation parts extend on the lateral face of the drum core to enable solder fillet confirmation, then solder connection reliability is improved, but the mounting area increases and mounting density decreases
Solution Approach 1:
The solder fillet formation part is repositioned from the lateral face (horizontal dimension) to the lower face (vertical dimension relative to the board). This dimensional relocation allows the solder fillet to form and be confirmed in a different spatial plane, eliminating the need for lateral extension beyond the square area boundary while maintaining solder connection reliability.
Solution Approach 2:
The invention creates a duplicate solder fillet formation structure on the lower face that mirrors the functionality of the lateral face design. By providing solder fillet formation parts on both the lower face and lateral face, the system ensures solder connection reliability while containing the primary confirmation area within the square boundary.
2Area of stationary object
If the drum core volume is reduced to fit within the square area including lateral extensions, then the mounting area is increased, but the choke coil performance deteriorates
Solution Approach 1:
By relocating the solder fillet formation functionality to the lower face, the drum core is no longer constrained by lateral extensions. This allows the drum core to maintain a larger volume within the square area boundary, improving choke coil performance while keeping the mounting area compact.
3Reliability
If external electrodes extend to the side face of the flange to provide mounting surfaces, then electrode connection reliability is improved, but the mounting area increases and high density mounting is impeded
Solution Approach 1:
The electrode structure is separated into distinct functional parts: the external electrode for electrical connection and the solder fillet formation part for mechanical attachment and soldering. This extraction allows the electrode to remain compact on the lower face while the solder fillet formation part provides the necessary mounting surface, reducing the overall mounting area.
4Reliability
If solder plating layer is provided on the lower face of external electrodes for surface mounting, then electrode-to-board connection is improved, but solder fillet formation confirmation becomes difficult
Solution Approach 1:
A dedicated solder fillet formation part made of resin material is introduced as an intermediary structure between the external electrode and the connection land. This mediator provides a visually distinct surface that facilitates solder fillet formation and confirmation, while the silver paste layer on the external electrode maintains the electrical connection reliability.
Data Source
AI summary
In a choke coil adapted to be surface-mounted on a board, a drum core including a core rod, and a circular first flange provided on a lower end of the core rod. A coil is wound around the core rod. Each of a pair of electrodes is electrically connected to an associated one end of the coil, and includes a first part provided on a lower face of the first flange adapted to oppose a connection land on the board and a second part provided on a side face of the first flange. The second part of each of the electrodes is adapted to hold a solder fillet together with the land. In a case where a hypothetic square circumscribing an outer periphery of the first flange is defined, the second part is located within the square and on a line connecting diagonal corners of the square.