Through Electrode Plating for Moisture Corrosion
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Solution Overview
Problem
Existing surface-mounted electronic devices face issues with moisture permeation and corrosion due to the use of nickel-iron alloys and gold thin films, leading to conductivity decreases and exposure of boundary portions, which are prone to corrosion.
Innovation Solution
A method involving the formation of through electrodes using a nickel-iron alloy, covered with a conductive film and electrolytic plating films, where a first electrolytic plating film of nickel or copper is applied with a thickness of 1 μm to 3 μm, and a second electrolytic plating film of tin or tin alloy is applied with a thickness of 10 μm to 30 μm, to prevent moisture permeation and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nickel-iron alloy is used as the through electrode and a gold thin film is used as the first metal film, then the through electrode is protected from oxidizing, but moisture and like can still attach between the through electrode and the first metal film causing corrosion due to battery effect
Solution Approach 1:
The patent applies a multi-layer composite structure consisting of a conductive adhesive layer, a nickel or copper plating layer, and a tin plating layer. This composite material system combines the advantages of each layer: the conductive adhesive provides initial conductivity and bonding, the nickel/copper layer provides moisture barrier and corrosion resistance, and the tin layer provides solderability and additional corrosion protection. This composite structure effectively prevents moisture attachment and battery effect corrosion while maintaining electrical conductivity.
Solution Approach 2:
The patent introduces a conductive adhesive layer as an intermediary between the through electrode and the metal plating layers. This intermediary layer facilitates the bonding of subsequent plating layers to the through electrode while maintaining electrical conductivity. The conductive adhesive acts as a mediator that enables the formation of a complete protective structure without direct contact between the nickel-iron alloy and potentially corrosive environments.
2Reliability
If a low melting point glass is used between the through electrode and the base, then air tightness is improved by thermal welding, but the boundary portion between the through electrode and the first metal film is exposed and prone to corrosion
Solution Approach 1:
The patent uses a multi-layer composite plating structure (conductive adhesive + nickel/copper + tin) to cover the boundary portion between the through electrode and the first metal film. This composite material system provides comprehensive protection: the conductive adhesive ensures bonding, the nickel/copper layer provides moisture barrier protection at the exposed boundary, and the tin layer provides additional corrosion resistance and solderability. This effectively seals and protects the previously exposed boundary areas while maintaining the air tightness benefits of the low melting point glass.
3Ease of manufacture
If a conductive adhesive such as silver paste is used for the external electrode, then the external electrode can be formed easily, but it is difficult to completely block moisture due to insufficient humidity resistance
Solution Approach 1:
The patent replaces the single-layer conductive adhesive with a multi-layer composite structure consisting of conductive adhesive, nickel or copper plating, and tin plating. This composite structure maintains the ease of manufacture (the conductive adhesive still provides the bonding foundation) while dramatically improving moisture barrier performance through the nickel/copper and tin layers that provide excellent humidity resistance and completely block moisture permeation.
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, reduces stress on the base substrate, and facilitates easy soldering during mounting, thereby enhancing the reliability and durability of the electronic device.
Implementation Method 1
a first electrolytic plating film forming process of forming a first electrolytic plating film on a surface of the conductive film by an electrolytic plating method; and a second electrolytic plating film forming process of forming a second electrolytic plating film, formed of tin or a tin alloy, on a surface of the first electrolytic plating film by an electrolytic plating method
Implementation Method 2
a glass lid is bonded thereto by anodic bonding, thereby sealing the electronic element
Data Source
AI summary
An electronic device includes an insulating base substrate having a through electrode, an electronic element provided on one surface of the insulating base substrate and connected to the through electrode, a lid provided on the one surface of the insulating base substrate, and an external electrode covering an end face of the through electrode that is exposed on another surface of the insulating base substrate different from the one surface thereof. The external electrode has a conductive film, a first electrolytic plating film provided on the conductive film, and a second electrolytic plating film provided on the first electrolytic plating film. The conductive film is provided on the exposed end face of the through electrode and on portions of the another surface of the insulating base substrate in the vicinity of the exposed end face of the through electrode.