Tin Paste Film on Nickel-Iron Through Electrodes
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Solution Overview
Problem
Existing electronic devices with glass packages face issues of moisture permeation and corrosion due to the use of nickel-iron alloys and gold films, leading to conductivity decreases and stress on the base substrate, especially when using conductive adhesives like silver paste for external electrodes.
Innovation Solution
An electronic device design featuring a nickel-iron alloy through electrode, a conductive film covering the exposed end face, and a paste film made of tin or tin alloy, applied using a printing method to cover both the conductive film and its side surfaces, preventing moisture ingress and reducing stress on the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive adhesive such as silver paste is used for the external electrode, then conductivity is improved, but moisture resistance deteriorates due to insufficient humidity resistance of the conductive paste
Solution Approach 1:
The patent applies composite materials by combining a conductive adhesive layer with a protective coating layer (such as glass epoxy resin or other moisture-resistant materials). This composite structure maintains the electrical conductivity provided by the conductive adhesive while the protective coating layer provides moisture resistance, thereby resolving the contradiction between conductivity and moisture resistance.
Solution Approach 2:
The patent applies local quality by providing different functional properties to different regions or layers of the external electrode structure. The conductive adhesive layer provides conductivity where needed, while the protective coating layer provides moisture resistance at the exposed surfaces, allowing each layer to perform its specific function optimally without compromising the other.
2Reliability
If a gold thin film is formed on the through electrode by electroless plating, then oxidation resistance is improved, but the boundary portion between the through electrode and the first metal film becomes exposed and prone to corrosion
Solution Approach 1:
The patent applies local quality by providing different protective measures to different portions of the through electrode structure. The electroless plating provides oxidation resistance on the main surface, while additional protective coating or sealing structures are applied specifically to the boundary portions that are prone to corrosion, addressing each region's specific requirements.
Solution Approach 2:
The patent uses composite materials by combining the gold thin film formed by electroless plating with additional protective materials such as glass epoxy resin or other sealing coatings. This composite structure maintains the oxidation resistance of the gold film while adding corrosion protection at vulnerable boundary areas.
3Strength
If a nickel-iron alloy is used as the through electrode, then mechanical strength is improved, but ionization tendency increases leading to battery effect and conductivity decrease when moisture is present
Solution Approach 1:
The patent applies composite materials by combining the nickel-iron alloy through electrode with protective coating layers that prevent moisture contact. This allows the nickel-iron alloy to provide mechanical strength while the protective coatings prevent the battery effect that would otherwise occur when moisture reaches the nickel-iron alloy surface.
Solution Approach 2:
The patent uses an intermediary approach by introducing protective coating layers as intermediaries between the nickel-iron alloy through electrode and the moisture environment. These coating layers act as mediators that prevent direct contact between moisture and the nickel-iron alloy, thereby preventing the battery effect while allowing the nickel-iron alloy to maintain its mechanical strength.
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 blocks moisture, prevents corrosion, and facilitates easy soldering during external component mounting by using a flexible tin or tin alloy paste film, thereby enhancing the reliability and durability of the electronic device.
Implementation Method 1
it is possible to block the permeation of moisture between a through electrode and an insulating base substrate to thereby prevent the occurrence of corrosion
Implementation Method 2
a gold thin film of the first metal film 122 is formed on an end face of the through electrode 121 by an electroless plating method
Implementation Method 3
a glass lid is bonded thereto by anodic bonding, thereby sealing the electronic element
Implementation Method 4
a low melting point glass is used between the through electrode 121 and base 110 to improve air tightness by thermal welding
Data Source
AI summary
An electronic device of the present invention includes an insulating base substrate in which a plurality of through electrodes are formed, an electronic element which is electrically connected to the through electrodes and is mounted on one surface of the base substrate, a lid which accommodates the electronic element and is bonded to the one surface of the base substrate, and an external electrode which covers a region from an end face of the through electrode, which is exposed by the other surface of the base substrate, to the other surface in the vicinity of the end face. The external electrode includes a conductive film which covers a region ranging from the end face to the other surface in the vicinity of the end face, and a paste film which covers a surface of the conductive film and is formed of a conductive paste. The paste film is formed by a printing method and is formed of tin or a tin alloy.