External Connection Terminals Electrolytic Gold Plating Moisture Ingress
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Solution Overview
Problem
The bondability between connection bumps and external connection terminals in semiconductor devices is degraded due to moisture ingress through the surface of electroless plating layers, which are not dense and can expose underlying metal atoms, leading to changes in the surface condition and reliability issues.
Innovation Solution
The formation of an electrolytic gold plating layer on top of the electroless plating layers prevents moisture ingress and ensures a dense surface, enhancing the bondability and reliability of the connection between connection bumps and external connection terminals by using electroplating wiring patterns made of copper film extending from the terminals to the substrate periphery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electroless plating layer is formed on the terminal portion, then connection reliability is improved and solder eating is prevented, but the surface is not dense and moisture can enter through the surface
Solution Approach 1:
The patent applies a composite plating structure consisting of multiple layers: an electroless plating layer (first and second layers) combined with an electroplating layer (third layer). This composite structure leverages the advantages of both plating methods - the electroless plating provides good adhesion and corrosion resistance, while the electroplating layer provides a dense surface that prevents moisture ingress. The combination resolves the contradiction between improving connection reliability and preventing moisture damage.
Solution Approach 2:
The patent implements a nested multi-layer plating structure where the electroless plating layers are embedded within the overall terminal structure, and the electroplating layer is formed on top of them. This nested arrangement allows each layer to perform its specific function - the inner electroless layers provide structural foundation and adhesion, while the outer electroplating layer provides moisture barrier protection.
2Reliability
If multiple electroless plating layers are formed sequentially, then bondability is improved, but the surface remains porous and bondability degrades over time due to moisture
Solution Approach 1:
The patent creates a composite plating system where electroless plating layers (提供良好的结合力) are combined with an electroplating layer (提供致密表面). This composite structure maintains bondability over time by preventing moisture from penetrating to the underlying metal layers, thus resolving the degradation issue while preserving initial bondability.
Solution Approach 2:
The patent applies different plating methods to different regions/layers of the terminal structure. The electroless plating is applied to inner layers where adhesion is critical, while electroplating is applied to the outer surface where moisture barrier properties are critical. This local differentiation of plating quality resolves the contradiction between initial bondability and long-term durability.
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 electrolytic gold plating layer maintains the surface integrity of the external connection terminals, improving the bondability and preventing peeling off, even under thermal expansion differences between substrates, thus ensuring reliable connections.
Implementation Method 1
an electroless plating layer formed on the terminal portion
Implementation Method 2
an electroplating layer formed on the electroless plating layer
Data Source
AI summary
A semiconductor device includes a substrate having external connection terminals, and a semiconductor chip mounted over a semiconductor-chip mounting portion of the substrate. The external connection terminals are formed by sequentially forming an electroless nickel plating layer, an electroless gold plating layer, and an electrolytic gold plating layer on a terminal portion formed on a surface of the substrate.