Aluminum Alloy Lead-Frame Oxidation Prevention
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Solution Overview
Problem
Aluminum alloy lead-frames are difficult to produce in mass quantities due to cracking and breaking during punching or bending, and they oxidize easily, leading to poor electrical connections in power semiconductor devices, making them unsuitable for industrial-scale production.
Innovation Solution
An aluminum alloy lead-frame with optimized composition (0.20% to 0.6% Si, 0.3% to 0.8% Fe, 0.1% to 0.3% Cu, 0.1% to 1% Mn, 0.5% to 5% Mg, 0.1% to 0.5% Cr, 0.1% to 0.4% Zn, and the rest Al) is used, and a multi-layer electroplating process (zinc, nickel, copper, and tin) is applied to prevent oxidation and ensure reliable connections without noble metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aluminum alloy material is used for lead-frame, then cost is reduced and heat dissipation is improved, but the material cracks or breaks during punching or bending
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the aluminum alloy (Si: 0.03-0.6%, Fe: 0.01-0.8%, Cu: 0.01-0.3%, Mn: 0.01-1.0%, Mg: 0.05-5.0%, Cr: 0.01-0.5%, Zn: 0.01-0.4%, Al: balance) to achieve the optimal balance between cost, heat dissipation, and ductility, preventing cracking during forming operations
Solution Approach 2:
The patent uses composite materials by creating a multi-layer electroplating structure (zinc layer 3-10μm, nickel layer 2-5μm, copper layer 3-8μm, tin layer 3-8μm) on the aluminum alloy substrate, combining the advantages of different materials to improve surface properties while maintaining the base metal's cost and heat dissipation benefits
2Device complexity
If aluminum alloy lead-frame is exposed to air, then manufacturing process is simplified, but oxidation occurs causing poor electrical interconnection
Solution Approach 1:
The patent applies composite materials by creating a multi-layer electroplating structure where the tin outer layer provides oxidation resistance while the underlying zinc, nickel, and copper layers provide structural integrity and electrical conductivity, ensuring both simplified manufacturing and reliable electrical connections
Solution Approach 2:
The patent uses inexpensive base metals (zinc, nickel, copper, tin) instead of expensive noble metals for electroplating, achieving the required protection and conductivity functions through optimized multi-layer construction rather than relying on costly materials
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 solution enables the production of durable, oxidation-resistant aluminum alloy lead-frames suitable for power semiconductor packages, improving manufacturing efficiency and reducing costs by avoiding the use of expensive noble metals, while maintaining reliable electrical connections and heat dissipation.
Implementation Method 1
a multi-layer electroplating process (zinc, nickel, copper, and tin) is applied to prevent oxidation and ensure reliable connections
Data Source
AI summary
A semiconductor package is provided with an Aluminum alloy lead-frame without noble metal plated on the Aluminum base lead-frame. Aluminum alloy material with proper alloy composition and ratio for making an aluminum alloy lead-frame is provided. The aluminum alloy lead-frame is electroplated with a first metal electroplating layer, a second electroplating layer and a third electroplating layer in a sequence. The lead-frame electroplated with the first, second and third metal electroplating layers is then used in the fabrication process of a power semiconductor package including chip connecting, wire bonding, and plastic molding. After the molding process, the area of the lead-frame not covered by the molding compound is electroplated with a fourth metal electroplating layer that is not easy to be oxidized when exposing to air.