Chip Package Pad Structure With Tin Shielding for Nickel Oxidation

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Solution Overview

Problem

Existing chip packaging technologies face challenges in maintaining the integrity of nickel-containing layers during deflux processes, leading to potential oxidation and reduced adhesion between pads and conductive bumps, which affects the yield and reliability of the chip bonding process.

Innovation Solution

A conductive protection layer, typically made of tin or its alloys, is formed over the nickel-containing layer to protect it from oxidation and enhance adhesion, comprising a denser structure that separates the nickel layer from deflux solutions, and an intermetallic compound layer is formed through a reflow process to provide additional protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If deflux processes are used to remove flux, then flux removal is achieved, but nickel-containing layer oxidation occurs and adhesion decreases

Engineering Contradiction:

Improveflux removalVSAvoidadhesion between pads and conductive bumps

Core Design Contradiction:

Loss of substanceVSReliability

Solution Approach 1:

A conductive protection layer is introduced as an intermediary between the nickel-containing layer and the deflux solution. This protection layer acts as a mediator that allows the deflux process to proceed while preventing direct contact between the deflux solution and the nickel-containing layer, thereby preventing oxidation and maintaining adhesion.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The conductive protection layer is formed in advance before the deflux process. This preliminary action prepares the structure to withstand the subsequent deflux process by already having the protective barrier in place, preventing oxidation before it can occur.

Inventive Principle:

Principle #10Preliminary action

2Loss of substance

If nickel-containing layer is exposed to deflux solutions, then flux removal is complete, but oxidation of nickel layer occurs

Engineering Contradiction:

Improveflux removal completenessVSAvoidoxidation of nickel layer

Core Design Contradiction:

Loss of substanceVSObject-affected harmful factors

Solution Approach 1:

The conductive protection layer serves as a protective intermediary that blocks harmful oxidation effects from reaching the nickel-containing layer while still allowing the deflux solution to effectively remove flux from the structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The conductive protection layer, which could be seen as an additional material layer, actually converts the potential harm of oxidation into a benefit by creating a controlled interface that protects the nickel-containing layer while enabling complete flux removal.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If conductive protection layer is formed over nickel-containing layer, then adhesion is improved and oxidation is prevented, but process complexity increases

Engineering Contradiction:

Improveadhesion between pads and conductive bumpsVSAvoidlayer structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The conductive protection layer performs multiple functions simultaneously: it provides adhesion between layers, prevents oxidation of the nickel-containing layer, and maintains electrical conductivity. This multi-functionality justifies the additional layer by delivering multiple benefits from a single structural addition.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The structure employs composite material principles by combining the nickel-containing layer with the conductive protection layer (typically tin or tin alloy), creating a composite structure that leverages the beneficial properties of both materials - the adhesion and conductivity of nickel with the oxidation resistance and protective qualities of tin.

Inventive Principle:

Principle #40Composite 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 conductive protection layer and intermetallic compound layer improve the adhesion between pads and conductive bumps, enhancing the yield and reliability of the chip bonding process by preventing nickel layer oxidation and allowing for the use of stronger deflux solutions for complete flux removal.

Implementation Method 1

a denser structure that separates the nickel layer from deflux solutions

Methodology Applied

Scientific EffectPhysical barrier formation:

Implementation Method 2

an intermetallic compound layer is formed through a reflow process

Methodology Applied

Scientific EffectIntermetallic compound formation:

Data Source

PatentUS12002746B2Chip package structure with metal-containing layer

Publication Date: 2024.06.04 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A chip package structure is provided. The chip package structure includes a first wiring substrate including a substrate, a first pad, a second pad, and an insulating layer. The chip package structure includes a nickel-containing layer over the first pad. The chip package structure includes a conductive protection layer over the nickel-containing layer. The conductive protection layer includes tin, and a recess is surrounded by the conductive protection layer and the insulating layer over the first pad. The chip package structure includes a chip over the second surface of the substrate. The chip package structure includes a conductive bump between the second pad and the chip.