Silver-Coated Metal Foil Assembly for Reliable Copper Wire Bonding
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Solution Overview
Problem
Aluminum bond wires exhibit low electrical conductivity and unreliable electrical connections with electronic components, while copper bond wires, though more conductive, are difficult to bond directly to the top surface of electronic components, necessitating a substrate arrangement with improved adhesion and metallurgical bonding.
Innovation Solution
A substrate arrangement comprising a metal foil with a silver layer of specific thickness (20-1500 nm) bonded to a silver sinter layer, allowing copper bond wires to connect reliably to electronic components through a silver sintered layer, facilitating a metallurgical bond with high adhesive strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum bond wires are used to connect electronic components to the substrate, then the manufacturing process is simple, but the electrical conductivity and reliability are low
Solution Approach 1:
The patent introduces a substrate arrangement with a metal foil and silver sintered layer as an intermediary between the electronic component and the bonding wire. The silver sintered layer acts as a mediator that enables copper bonding wires to be reliably connected to the electronic component top surface, which would otherwise be difficult to bond directly. This intermediary structure resolves the contradiction by providing both high reliability and manufacturability.
Solution Approach 2:
The substrate arrangement uses a composite structure consisting of a metal foil (copper or copper alloy) combined with a silver sintered layer. This composite material approach allows the system to achieve both high electrical conductivity from the copper and reliable bonding capability from the silver sintered layer, resolving the contradiction between reliability and ease of manufacture.
2Reliability
If copper bond wires are used to replace aluminum bond wires, then electrical conductivity is improved, but direct bonding to the top surface of electronic components becomes difficult
Solution Approach 1:
The substrate arrangement with metal foil and silver sintered layer serves as an intermediary that enables copper bonding wires to be reliably connected to electronic components. The silver sintered layer specifically facilitates the bonding process, making it easy to manufacture while maintaining the high electrical conductivity of copper.
Solution Approach 2:
The metal foil in the substrate arrangement is designed to be self-bonding to the silver sintered layer, which is already attached to the electronic component top surface. This self-service mechanism simplifies the manufacturing process by eliminating the need for complex multi-layer coatings while ensuring reliable copper wire bonding.
3Reliability
If a multi-layer structure (metal foil, nickel layer, palladium layer, gold layer) is used to improve silver sinter layer adhesion, then bonding reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts and eliminates the unnecessary nickel and palladium layers from the traditional multi-layer structure, keeping only the essential metal foil and silver sintered layer combination. This extraction maintains the required adhesive strength while significantly reducing manufacturing complexity.
Solution Approach 2:
Instead of adding multiple layers to improve adhesion, the patent inverts the approach by using a simpler two-layer structure (metal foil with silver sintered layer) that achieves the same or better bonding reliability. This inversion simplifies the device structure while maintaining performance.
4Strength
If the silver layer thickness is increased to improve bond strength, then adhesive strength is improved, but material cost and processing time increase
Solution Approach 1:
The patent optimizes the silver layer thickness parameter to a specific range (20-1500 nm) that provides sufficient bond strength while minimizing silver material consumption. This parameter optimization resolves the contradiction by finding the optimal balance between strength and material quantity.
Solution Approach 2:
The patent uses a thin silver layer that is sufficient for the bonding function but not excessive, effectively using a minimal amount of expensive material (silver) to achieve the required performance. This approach is economically efficient by using only the necessary quantity of high-value material.
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 substrate arrangement enables a strong bond between the metal foil and silver sintered layer, allowing copper bond wires to form a metallurgical connection with high adhesive strength, enhancing electrical conductivity and reliability.
Implementation Method 1
the metal foil of the substrate arrangement is then metallurgically bonded to the top surface of the electronic component via the silver sintered layer
Implementation Method 2
it is necessary that the metallurgical bond created via the silver sintered layer between the underside of the metal foil and the top of the electronic component has a high adhesive strength
Implementation Method 3
a silver sintered layer... typically a pre-dried sintering paste
Implementation Method 4
the metal foil of the substrate arrangement is then metallurgically bonded to the top surface of the electronic component via the silver sintered layer
Implementation Method 5
copper bond wires can be bonded particularly reliably to the metal of the base substrate... The top surface of the metal foil is available for a metallurgical bond with the copper bonding wire
Data Source
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AI summary
The invention relates to a substrate arrangement, a method for manufacturing an electronic assembly, and an electronic assembly. The substrate arrangement comprises (a) a metal foil comprising a top and a bottom, (b) a silver layer arranged on the bottom of the metal foil, and (c) a silver sintered layer arranged on the silver layer, wherein the silver layer has a thickness d(Ag) in the range of 20–1500 nm.