Stacked Multilayer Capacitor Split Lead Frame Thermal Management
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Solution Overview
Problem
Stacked multilayer ceramic capacitors face inefficiencies in heat dissipation, thermal stress, and mechanical shock resistance due to their design, which can lead to issues like cracking, shorting, and vibration-induced failures, particularly in high-power applications and extreme environments.
Innovation Solution
A split lead frame configuration that enhances heat transfer, tolerates thermal stresses, and provides mechanical stability by increasing contact areas with the substrate, allowing for optional fastening and orientation that reduces inductance and improves performance under vibration and shock conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If stacked multilayer ceramic capacitors are used in high-power applications, then capacitance and voltage rating are improved, but heat dissipation efficiency deteriorates due to longer conduction path
Solution Approach 1:
The capacitor structure is divided into multiple individual ceramic chips stacked together, each with its own heat dissipation path. This segmentation allows heat to be dissipated from multiple surfaces simultaneously rather than through a single long conduction path, improving overall heat dissipation efficiency while maintaining high capacitance and voltage ratings.
Solution Approach 2:
The patent transitions from a single-plane heat dissipation approach to a three-dimensional stacked configuration. By stacking multiple chips vertically, heat can be dissipated from the top, bottom, and side surfaces of the stack, adding dimensional pathways for heat flow and reducing thermal resistance in high-power applications.
2Temperature
If aluminum substrate is used for heat dissipation, then heat discharge capacity is improved, but thermal stress increases due to high coefficient of thermal expansion
Solution Approach 1:
The patent applies different materials with different thermal expansion coefficients to different parts of the mounting structure. By using a compliant mounting structure or intermediate layer between the aluminum substrate and ceramic capacitor, the local thermal expansion mismatch is accommodated, reducing thermal stress while maintaining the high heat discharge capacity of the aluminum substrate.
Solution Approach 2:
The patent changes the thermal and mechanical parameters of the mounting interface by introducing a compliant layer or modifying the substrate properties. This allows the system to maintain high heat discharge capacity while adjusting the thermal expansion characteristics at the interface to reduce thermal stress on the ceramic capacitor during temperature cycling.
3Stability of the object's composition
If epoxy is used to adhere capacitor to board, then mechanical stability is improved, but thermal stress problems arise due to expansion and contraction of epoxy
Solution Approach 1:
The patent replaces the single-material epoxy adhesive with a composite mounting structure that combines multiple materials with complementary properties. This composite approach provides both mechanical stability for vibration resistance and thermal compliance to accommodate expansion and contraction, eliminating the thermal stress problems associated with epoxy while maintaining strong mechanical attachment.
4Quantity of substance
If stacked capacitor height is increased, then capacitance value is improved, but resistance to vibration and mechanical shock deteriorates
Solution Approach 1:
The patent divides the total capacitance into multiple smaller ceramic chips stacked together, each chip being mechanically robust. This segmentation allows the use of individual standardized chips with proven mechanical reliability while achieving the required total capacitance through the stack, rather than using a single tall capacitor that would be more susceptible to vibration and shock damage.
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 split lead frame design improves heat dissipation, reduces thermal stress, and enhances mechanical stability, resulting in improved performance and reliability of stacked multilayer capacitors in high-power applications and harsh environments.
Implementation Method 1
Heat conduction occurs through an internal electrode to the silver end terminations through the solder to the lead frames and then into a circuit board or other substrate. The split lead frame provides larger areas in electrical contact with the capacitor and a substrate to substantially improve heat transfer from the capacitor.
Implementation Method 2
since the temperature in the vicinity of the source changes greatly when the source is turned on and off, a significant amount of thermal stress occurs at a ceramic capacitor mounted on the aluminum substrate, which has a high coefficient of thermal expansion.
Data Source
AI summary
A capacitor device mountable on a plane of a substrate includes an electrically conductive bottom plate adapted to be mounted substantially parallel to, and in electrical contact at the plane of the substrate and a first multilayer capacitor having substantially parallel first and second electrode plates oriented substantially perpendicular to the bottom plate with the first electrode plates being electrically connected to the bottom plate. An electrically conductive top lead frame overlaps with, and is electrically isolated from, the bottom plate. The top lead frame electrically connected to the second electrode plates and adapted to be electrically connected at the plane of the substrate. The bottom lead frame may have a corrugated shape, where the corrugated shape provides compliance between the first multilayer capacitor and the substrate. A portion of the top lead frame may contact at least a portion of a side of the first multilayer capacitor.