Inner Lead Metal Layer Layout to Prevent Resin Peeling
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Solution Overview
Problem
The bonding strength between a metal layer on the inner lead and the sealing resin in semiconductor devices is weaker than the bonding strength between the inner lead and the sealing resin, leading to peeling and defects such as increased leakage current when a tensile force is applied.
Innovation Solution
The terminal leads in the semiconductor device include a base member with a higher bonding strength to the sealing resin, featuring a metal layer between the base member and the wire, and an obverse surface with an opposing side exposed from the metal layer to enhance bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal layer is formed on the surface of the inner lead to mitigate thermal shock, then thermal shock resistance is improved, but bonding strength between the metal layer and sealing member becomes weaker than bonding strength between the inner lead and sealing member
Solution Approach 1:
The patent applies different materials with different properties to different parts of the lead structure. The metal layer (e.g., nickel or palladium) is applied only to the surface of the inner lead that contacts the sealing member, providing localized thermal shock resistance and enhanced bonding, while the bulk lead material (e.g., copper) maintains its electrical and mechanical properties. This local differentiation resolves the contradiction by concentrating the protective function where it is most needed.
Solution Approach 2:
The patent creates a composite structure by combining the inner lead material (e.g., copper) with a metal layer (e.g., nickel, palladium, or their alloys) having different properties. The composite structure leverages the high electrical conductivity of copper while adding the thermal shock resistance and bonding enhancement properties of the metal layer, thus resolving the contradiction between thermal shock resistance and bonding strength.
2Area of stationary object
If the surface area of the inner lead is reduced, then device size is minimized, but peeling is more likely to occur at the interface between the metal layer and sealing member
Solution Approach 1:
The patent enhances the interface region between the lead and sealing member by applying a metal layer with superior bonding properties specifically at this critical interface. This local enhancement ensures that even with reduced overall surface area, the bonding strength at the interface is sufficient to prevent peeling, thus resolving the contradiction between miniaturization and reliability.
Solution Approach 2:
The patent changes the material parameters (composition, thickness, properties) of the metal layer to optimize bonding strength. By carefully selecting the metal layer material (nickel, palladium, or their alloys) and controlling its thickness (5-50 μm), the patent achieves adequate bonding strength and peeling resistance even with reduced lead surface area, resolving the contradiction between device size and reliability.
3Strength
If the metal layer thickness is increased to improve bonding strength, then bonding strength between metal layer and sealing member is improved, but device size increases
Solution Approach 1:
The patent optimizes the metal layer thickness parameter within a specific range (5-50 μm) to achieve the necessary bonding strength while minimizing device size. This parameter optimization resolves the contradiction by finding the optimal balance point where sufficient bonding strength is achieved without excessive thickness that would increase device volume.
Solution Approach 2:
The patent concentrates the metal layer function at the critical interface region between the lead and sealing member, applying the layer only where bonding is needed rather than uniformly throughout the entire lead structure. This localized application improves bonding strength while minimizing the overall volume and device size.
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 suppresses peeling at the interface between the terminal leads and the sealing resin, maintaining electrical connectivity and reducing defects.
Implementation Method 1
the base member has a greater bonding strength with respect to the sealing resin than the metal layer
Data Source
AI summary
A semiconductor device includes: a semiconductor element; an island lead on which the semiconductor element is mounted; a terminal lead electrically connected to the semiconductor element; a wire connected to the semiconductor element and the terminal lead; and a sealing resin covering the semiconductor element, the island lead, the terminal lead, and the wire. The terminal lead includes a base member having an obverse surface facing in a thickness direction of the terminal lead, and a metal layer located between the obverse surface and the wire. The base member has a greater bonding strength with respect to the sealing resin than the metal layer. The obverse surface includes an opposing side facing the island lead. The obverse surface includes a first portion that includes at least a portion of the opposing side and that is exposed from the metal layer.