Silver-Palladium PCB Surface Treatment for Copper Wire Bonding

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Solution Overview

Problem

The electronics industry faces challenges in reducing the cost and improving the bonding ability of printed circuit boards, as conventional surface treatments using gold or silver result in low bonding yields for copper wires due to the soft properties of these metals.

Innovation Solution

A printed circuit board structure is developed with a silver metal layer sandwiched between two palladium metal layers, which enhances hardness and bonding ability, reducing the need for gold and preventing silver migration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a soft gold plated layer is used for surface treatment, then the surface treatment is suitable for gold wire connection, but the bonding ability for copper wire is reduced and bonding yield is low

Engineering Contradiction:

Improvesuitability for gold wire connectionVSAvoidbonding yield for copper wire

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The surface treatment layer is divided into multiple functional layers: a soft gold layer (0.01-0.1 μm) for gold wire bonding compatibility, an intermediate layer (0.1-1.0 μm) for adhesion and transition, and a hard metal layer (1.0-5.0 μm) for structural support and copper wire bonding strength. This segmentation allows each layer to perform its specific function optimally.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite plated layer structure combining multiple metals with different properties: soft gold provides electrical conductivity and gold wire bonding capability, while the hard metal layer (nickel, palladium, or platinum) provides mechanical strength and copper wire bonding capability. This composite structure resolves the contradiction between softness for gold wire and hardness for copper wire bonding.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If a silver plated layer is used for surface treatment, then the cost is reduced compared to gold, but the bonding ability is reduced due to the soft property of silver

Engineering Contradiction:

Improvecost reductionVSAvoidbonding ability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The invention creates a composite plated layer combining silver (for cost reduction and electrical conductivity) with hard metals such as nickel, palladium, or platinum (for bonding strength). The hard metal layer provides the necessary mechanical strength to support copper wire bonding while the silver layer maintains cost effectiveness and electrical performance.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The plated layer is segmented into a silver-based layer for cost and conductivity, and a hard metal layer (0.1-5.0 μm) for bonding strength. This segmentation allows the silver to fulfill its cost-saving role while the hard metal layer compensates for the softness issue through proper thickness and material selection.

Inventive Principle:

Principle #1Segmentation

3Reliability

If gold is used for surface treatment, then the bonding ability for gold wire is improved, but the cost for surface treatment increases

Engineering Contradiction:

Improvebonding ability for gold wireVSAvoidcost for surface treatment

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention applies a thin soft gold layer (0.01-0.1 μm) only where gold wire bonding is required, rather than covering the entire surface with thick gold. This localized application maintains the essential gold wire bonding capability while dramatically reducing gold consumption and cost.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention replaces expensive thick gold plating with a combination of cheaper metals (silver, nickel, palladium, or platinum) that provide equivalent or superior performance when properly configured. The thin gold layer serves its specific purpose without the excessive cost of traditional thick gold plating.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 reduces surface treatment costs, improves copper wire bonding, and ensures reliability by controlling metal migration, thereby lowering assembly costs and enhancing the printed circuit board's corrosion resistance.

Implementation Method 1

forming a first palladium metal layer on the circuit pattern or the base pad using a palladium plating solution including palladium

Methodology Applied

Scientific EffectElectroplating: Electroplating

Implementation Method 2

forming a silver metal layer on the first palladium metal layer using a silver plating solution including silver

Methodology Applied

Scientific EffectElectroplating: Electroplating

Implementation Method 3

forming a second palladium metal layer on the silver metal layer using the palladium plating solution including palladium

Methodology Applied

Scientific EffectElectroplating: Electroplating

Data Source

PatentUS9661750B2Printed circuit board and method of manufacturing the same

Publication Date: 2017.05.23 LG INNOTEK CO LTD

AI summary

Provided is a printed circuit board, including: a circuit pattern or a base pattern formed on an insulating layer; and a plurality of metal layers formed on the circuit pattern or the base pattern, wherein the metal layers includes: a silver metal layer formed of a metal material including silver; a first palladium metal layer formed at a lower part of the silver metal layer; and a second palladium metal layer formed at an upper part of the silver metal layer.