Ambient Temperature Ball Bonding for Gold Wire

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Solution Overview

Problem

Wedge bonding has limitations such as restricted take-off angle and direction, large bond foot size, inability to stack additional bonds, and oxidation issues with small bonding pads, while ball bonding may damage sensitive IC devices with heat application.

Innovation Solution

Ball bonding a less than 1 thousandth of an inch diameter gold alloy wire to a gold alloy contact pad at ambient temperature using ultrasonic bonding frequencies greater than 60 kHz and less than 200 kHz, avoiding heat application to sensitive components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If ball bonding is performed using conventional heating methods, then bonding strength is improved, but sensitive IC devices adjacent to the bonding pad may be damaged due to heat

Engineering Contradiction:

Improvebonding strengthVSAvoidheat damage to sensitive IC devices

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the thermal field (heating system) with a mechanical field (ultrasonic vibration system) to achieve bonding. The ultrasonic bond head vibrates at frequencies between 60-200 kHz with an amplitude of 0.5-5 micrometers, generating mechanical energy that facilitates bonding without thermal damage to adjacent sensitive components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the bonding parameters by using ultrasonic vibration frequency (60-200 kHz) and low amplitude (0.5-5 micrometers) instead of conventional heating temperatures. This parameter transformation allows bonding to occur at ambient temperature, eliminating heat damage while maintaining bond strength.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If wedge bonding is used to achieve bonding, then bonding can be performed at room temperature, but the take-off angle and direction are substantially limited

Engineering Contradiction:

Improvebonding temperatureVSAvoidtake-off angle and direction flexibility

Core Design Contradiction:

TemperatureVSAdaptability or versatility

Solution Approach 1:

The patent segments the bonding process into two distinct phases: first forming a ball at the wire end, then using that ball as a new bonding point that can be positioned at various angles and directions. This segmentation allows the bond head to achieve greater angular flexibility (up to 45 degrees from vertical) compared to conventional wedge bonding.

Inventive Principle:

Principle #1Segmentation

3Ease of manufacture

If wedge bonding is used, then bonding can be performed simply, but the bond foot size is relatively large

Engineering Contradiction:

Improvebonding process simplicityVSAvoidbond foot size

Core Design Contradiction:

Ease of manufactureVSArea of moving object

Solution Approach 1:

The patent uses a spherical ball at the end of the wire as the bonding element. This spherical geometry concentrates the bonding force into a small contact area, achieving bond foot dimensions of 1-10 micrometers, which is significantly smaller than conventional wedge bond foot sizes while maintaining process simplicity.

Inventive Principle:

Principle #14Spheroidality (Curvature)

4Productivity

If additional wedge bonds are attempted on top of a previous bonded spot, then wiring density can be increased, but oxidation prevents bonding pad reuse

Engineering Contradiction:

Improvewiring densityVSAvoidbonding pad reusability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The ultrasonic bonding process inherently cleans and prepares the bonding pad surface during each bonding operation, removing oxidation and contaminants. This self-cleaning effect allows the same bonding pad to be reused multiple times for additional bonds without degradation, enabling higher wiring density on the same substrate.

Inventive Principle:

Principle #25Self-service

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

Enables flexible take-off direction and angle without stressing the bond, reduces bond size, allows stacking, and prevents oxidation, making it suitable for small bonding pads and sensitive devices.

Implementation Method 1

using a ultrasonic bonding frequency greater than 60 kHz and less than 200 kHz

Methodology Applied

Scientific EffectUltrasonic vibration: Ultrasonic Vibration

Data Source

PatentUS8767351B1Ambient temperature ball bond

Publication Date: 2014.07.01 SEAGATE TECH LLC

AI summary

The presently disclosed technology describes systems and methods for attaining a ball bond using less than 1 thousandth of an inch diameter gold wire using ultrasonic bonding energy and without heating an underlying bonding pad. The ball bond allows the use of particularly small bonding pads that are particularly close to adjacent microelectronic structures that limit the use of other bonding techniques that have shallow take-off angles.