Nanoparticle-Modified Ag Plated Lead Frame for Semiconductor Devices
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Solution Overview
Problem
Conventional semiconductor devices face issues with copper diffusion onto the Ag film due to its thickness reduction during manufacturing processes, leading to poor contact between the metallic wire and the Ag film, resulting in connection failures.
Innovation Solution
Employing an Ag-plated film with nanoparticles, specifically carbon grains, in the gaps among Ag crystal grains to block copper diffusion paths, allowing for a thinner Ag film thickness (0.3 μm to 3 μm) while ensuring reliable wire connection and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the Ag film thickness is decreased to reduce cost, then material cost is reduced, but Cu diffusion onto the Ag film surface occurs during heating processes
Solution Approach 1:
Nanoparticles are introduced as intermediary substances within the Ag film structure. These nanoparticles fill the gaps between Ag crystal grains and act as diffusion barriers, preventing Cu atoms from migrating through the Ag film to the surface during heating processes. This allows the Ag film to be thinner while maintaining protection against Cu diffusion.
Solution Approach 2:
The Ag film is transformed from a pure metal film into a composite material structure containing Ag crystal grains and dispersed nanoparticles. This composite structure combines the electrical conductivity of Ag with the diffusion-blocking capability of nanoparticles, enabling thin film thickness while preventing Cu contamination.
2Reliability
If the Ag film thickness is increased to prevent Cu diffusion, then wire connection reliability is improved, but material cost increases
Solution Approach 1:
Nanoparticles serve as intermediary diffusion barriers distributed within the Ag film matrix. Their presence creates multiple obstruction points for Cu diffusion paths, allowing thinner Ag films to achieve the same level of Cu diffusion prevention that would otherwise require much thicker films.
Solution Approach 2:
The invention changes the internal structure parameters of the Ag film by incorporating nanoparticles with specific size ranges (0.1-10 μm). This structural parameter modification enhances the diffusion-blocking capability per unit thickness, allowing reduced Ag film thickness while maintaining or improving Cu diffusion prevention effectiveness.
3Reliability
If nanoparticles are added to the Ag film to block Cu diffusion, then Cu diffusion prevention is improved, but manufacturing complexity increases
Solution Approach 1:
The invention specifies particular parameter ranges for nanoparticles (size: 0.1-10 μm, content: 1-50 wt%) to optimize diffusion blocking while maintaining manufacturability. These controlled parameters ensure the nanoparticles provide effective Cu diffusion barriers without creating excessive structural complexity or processing difficulties.
Solution Approach 2:
Nanoparticles are strategically positioned within the Ag film structure, specifically filling gaps between Ag crystal grains where Cu diffusion occurs. This localized placement provides maximum diffusion blocking effectiveness with minimal nanoparticle content, avoiding unnecessary overall structural complexity.
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 Ag-plated film with nanoparticles effectively prevents copper deposition on the Ag film surface, ensuring reliable connections and improving productivity by allowing for a shorter formation time and reduced material costs.
Implementation Method 1
nanoparticles arranged in gaps among Ag crystal grains... block copper diffusion paths
Implementation Method 2
an Ag-plated film with nanoparticles arranged in gaps among Ag crystal grains
Data Source
AI summary
A lead frame includes a lead frame body 21 having a die pad 24 to which a semiconductor chip 12 is bonded and a plurality of leads 25 arranged around the die pad 24 and made of Cu or an alloy containing Cu, and a metallic film formed on the lead frame body 21 and to connected to a metallic wire 15 connected to the electrode pad 36 of the semiconductor chip 12. The metallic film is an Ag-plated film 22 with nanoparticles 34 arranged in gaps 33 among Ag crystal grains 31.