Wound Capacitor Substrate Packaging to Avoid Molding Stress
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Solution Overview
Problem
Existing packaging methods for roll-type solid electrolytic capacitors are limited by device size and vibration resistance, leading to reliability issues in applications like the vehicle and transportation industries, and are difficult due to the fragility of the capacitors and high viscous stress during conventional packaging processes.
Innovation Solution
A packaging structure using two protective substrates with insulating material to sandwich the capacitor element, with shorted leads passing through holes for external connection, and a multi-step plating process for aluminum leads, and soldering for copper clad leads, allowing for reduced device size and improved mechanical support, and enabling batch processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional can-type packaging is used to contain the capacitor body, then the capacitor is protected and sealed, but the device volume increases significantly due to sealing materials and the capacitor lacks mechanical support leading to poor vibration resistance
Solution Approach 1:
The patent merges the protective substrate and support structure into a single integrated component. The protective substrate serves dual functions: providing mechanical support to prevent material fatigue at the aluminum leads during vibration, and containing the capacitor body without requiring separate sealing materials. This eliminates the need for additional sealing components and reduces overall device volume while improving vibration resistance.
Solution Approach 2:
The protective substrate is designed to perform multiple functions simultaneously: it acts as a mechanical support structure, a containment housing, and a sealing barrier. By integrating these functions into one component, the patent eliminates the need for separate sealing materials and support structures, thereby reducing device volume while enhancing vibration resistance.
2Reliability
If molding compound by transfer molding is used to package the capacitor, then the capacitor is enclosed and protected, but the highly viscous material flow under large pressure creates high viscous stress that may damage the fragile capacitor
Solution Approach 1:
The patent extracts the high-viscous-stress packaging step from the process by using a pre-formed protective substrate with a cavity instead of injecting molding compound under pressure. The capacitor is placed into the pre-formed substrate cavity, eliminating the need for high-pressure material flow and thereby avoiding viscous stress damage to the fragile capacitor.
Solution Approach 2:
The protective substrate acts as an intermediary structure that receives and secures the capacitor without requiring high-pressure molding compound flow. The substrate cavity provides a pre-formed housing that accommodates the capacitor, eliminating the need for direct high-pressure material contact and reducing viscous stress on the capacitor.
3Stress or pressure
If compression molding is used to reduce pressurized flow, then less pressure is applied, but viscous stress is not completely eliminated and may still damage the capacitor
Solution Approach 1:
The patent completely removes the compression molding step from the packaging process by using a pre-formed protective substrate with a cavity. The capacitor is simply placed into the cavity and secured, eliminating any pressurized flow or viscous stress application to the capacitor, thereby ensuring capacitor integrity.
4Reliability
If sheet compound molding is used to package the capacitor, then the capacitor is enclosed, but high pressure is applied that may damage the fragile capacitor
Solution Approach 1:
The patent extracts the high-pressure sheet compound molding step by using a pre-formed protective substrate with a cavity. The capacitor is placed into the cavity without requiring high-pressure molding, thereby protecting the fragile capacitor from pressure damage while still providing enclosure and protection.
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 solution enhances vibration resistance, reduces device size, and facilitates batch manufacturing, improving reliability and efficiency in packaging roll-type capacitors while minimizing damage during the filling process.
Implementation Method 1
The filling of the insulating material can be conducted by a capillary filling process or by a simple pouring and flooding process
Implementation Method 2
the external terminals and the electric connections from the terminals to the aluminum electrode leads of the capacitor element is in general made by a multi-step plating process
Implementation Method 3
the electric connection between the leads and the external terminal is basically by soldering followed by electroplating
Data Source
AI summary
This invention describes a packaging structure for roll-type (wound-type) aluminum conductive polymer capacitor element. Two protective substrates are applied to sandwich a roll-type capacitor element in between with an insulating material surrounding the capacitor element also in between the protective substrates. The protective substrates comprise electrically separated anodic conductive pad and cathodic conductive pad on their surfaces and through holes that pass through the conductive pads. The capacitor element is oriented with its axis perpendicular to the two substrates. The anodic and cathodic leads of the capacitor element pass through the through holes. An anodic external terminal is plated over the anodic conductive pad and a cathodic external terminal is plated over the cathodic conductive pad so that the anodic external terminal is electrically connected to the anodic lead and the cathodic external terminal is electrically connected to the cathodic lead.