Surface Mount Capacitor External Anode Connection
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Solution Overview
Problem
Surface mount capacitors face challenges in achieving high volumetric efficiency, particularly with single-sided terminations, where the size of the capacitive element is limited by the need for substantial space for electrical connections, leading to reduced capacitance per unit volume and increased case size, which is problematic in miniaturized electronic devices.
Innovation Solution
The implementation of single-sided terminations with an external conductive path that connects the anode wire to the termination on the outside of the case, eliminating the need for internal conductive paths and allowing a longer capacitive pellet, thereby increasing the volume occupied by the pellet within the fixed case size, and using an insulative adhesive to support the pellet during molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-sided terminations are used with internal conductive paths, then electrical connections are achieved, but the case size increases and volumetric efficiency decreases
Solution Approach 1:
The conductive path is extracted from the internal case space and relocated to the exterior surface of the case. The anode wire extends through the case wall to make external contact with the termination, eliminating the need for internal conductive pathways and associated insulation structures, thereby reducing case volume while maintaining electrical connection reliability
Solution Approach 2:
The electrical connection is transitioned from a three-dimensional internal path requiring volume occupation to a two-dimensional surface-level connection. The anode wire contact point is positioned on the exterior case surface, allowing terminations to be mounted externally without consuming internal case volume, thus improving volumetric efficiency
2Reliability
If wrap-around terminations are used, then electrical connections are achieved, but shorting risks increase
Solution Approach 1:
The anode wire is extracted from the enclosed internal space and extended to make contact with the termination on the exterior case surface. This removes the wire from the confined internal environment where shorting could occur between adjacent components, placing it in an open external configuration that eliminates this shorting hazard
Solution Approach 2:
The case wall itself serves as an intermediary barrier between the anode wire and other internal components. By having the wire contact the exterior surface rather than extending through the internal space, the case structure acts as a physical separator that prevents potential shorting paths while maintaining the electrical connection function
Data Source
AI summary
A surface mount capacitor (10) and method for making the same. A solid slug or pellet anode body (1) is encapsulated in a case (6) of insulating material. An anode and cathode termination pair (2, 3) are formed with surface mount mounting portions on one side of the case (6). An electrical connection (4) is made from the cathode termination (2) to a cathode on pellet (1) through the case (6). An electrical connection (7) is made between an anode associated with the pellet (1) and the anode termination (3) externally of the case (6). The external connection (7) allows improved volumetric efficiency by freeing up space in the case (6) for a bigger pellet (1). The method includes mass producing these capacitors (10) by mounting a plurality of pellets (1) on a lead frame (11) with pre-formed anode/cathode termination pairs (2, 3), at least substantially encapsulating the plurality of mounted pellets (1) and each pellet's associated anode and cathode, singulating the encapsulated pellets (1) to expose a portion of the pellet anode, and applying the electrical external conductive path (7) between pellet anode and anode termination (3).