Carbon Diffusion Barrier for Copper Corrosion in PCBs

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Solution Overview

Problem

Current protection methods for copper layers in electronic devices are insufficient, as available dielectrics do not act as effective diffusion barriers against moisture, leading to oxidation and electrical/mechanical failures, particularly in packages like Wafer Level Ball Grid Array and Flip-Chip bonding, where traditional dielectrics are problematic.

Innovation Solution

A thin carbon layer, 10-40 nm thick, is deposited as a diffusion interlayer to prevent moisture ingress and corrosion, acting as both a protective barrier and adhesion promoter for dielectric layers, and can be used in various locations such as Cu lines, pads, and substrates, potentially eliminating conditioning steps and preventing delamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional dielectric materials are used to cover copper layers, then the copper layer is provided with some protection, but the dielectric does not act as an effective diffusion barrier against moisture, leading to oxidation and failure

Engineering Contradiction:

Improveprotection of copper layerVSAvoidmoisture diffusion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A carbon interlayer is introduced between the copper layer and the overlying dielectric structure. This intermediary carbon layer serves as an effective diffusion barrier to moisture, preventing moisture from reaching the copper layer and causing oxidation, while the dielectric layers provide additional protection. The carbon layer specifically addresses the moisture diffusion problem that traditional dielectric materials cannot solve.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The protective structure uses a composite approach by combining carbon material with dielectric materials. The carbon layer provides superior moisture diffusion barrier properties, while the dielectric layers provide additional protection and structural support. This composite structure leverages the complementary strengths of different materials to achieve both electrical insulation and effective moisture protection.

Inventive Principle:

Principle #40Composite materials

2Device complexity

If no protective layer is used on copper layers, then the fabrication process is simpler, but the copper layer is susceptible to oxidation and corrosion during processing and after fabrication

Engineering Contradiction:

Improvefabrication processVSAvoidresistance to oxidation

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If dielectric layers are used to cover copper layers, then some protection is provided, but delamination and corrosion may still occur under temperature cycling and humidity conditions

Engineering Contradiction:

Improveprotection during processingVSAvoidadhesion under thermal stress

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The carbon interlayer not only provides moisture barrier protection but also serves as an adhesion promoter for the dielectric layers. This intermediary layer improves the bonding between the copper layer and the dielectric structure, preventing delamination under temperature cycling and humidity conditions while maintaining effective corrosion protection.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 carbon layer effectively prevents moisture from contacting copper layers, reducing the risk of oxidation and corrosion, enhancing the reliability of electronic devices under temperature cycling and humidity conditions, and can be easily removed via reactive ion etching.

Implementation Method 1

a non-conductive carbon layer on the substrate, the non-conductive carbon layer configured to act as a diffusion barrier to moisture for the copper layer

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 2

can be easily removed via reactive ion etching

Methodology Applied

Scientific EffectReactive ion etching: Plasma

Data Source

PatentUS10546826B2Device containing and method of providing carbon covered copper layer

Publication Date: 2020.01.28 INTEL CORP

AI summary

A device and method of preventing corrosion of a copper layer in a PCB is disclosed. A first dielectric is disposed on a substrate. A copper layer is plated in an opening in the first dielectric and, after conditioning the copper layer, a redistribution layer is plated on the copper layer. A solder resist layer is disposed above the copper layer. A solder ball is disposed in an opening in the solder resist layer. The solder ball is in conductive contact with the copper layer and in physical contact with the redistribution layer. A non-conductive carbon layer is disposed on and in contact with the redistribution layer or tsi-diehe solder resist layer. The carbon layer is substantially thinner than the copper layer and acts as a diffusion barrier to moisture for the copper layer.