Megasonic Cleaning System for Semiconductor Packages

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Solution Overview

Problem

Existing cleaning methods for singulated electronic packages, such as mechanical agitation and megasonic vibrations, face issues like residue trapping in brushes, incomplete particle removal, and risk of dislodging small packages due to high pressure or contact forces, and limited cleaning area coverage.

Innovation Solution

A system using a pickhead to hold semiconductor packages in an array, with multiple nozzles projecting upward jets of cleaning fluid infused with megasonic energy, and a driving device for relative movement to ensure thorough cleaning without damaging packages, utilizing inclined megasonic jets to increase coverage and reduce water consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If mechanical agitation with a brush is used to clean sawing residue, then cleaning effectiveness is improved, but the brush traps residue requiring periodic maintenance and may introduce dirt onto surfaces

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidmaintenance requirements

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the mechanical brush system with a jet of liquid infused with megasonic vibrations. This substitution eliminates the mechanical contact and residue trapping issues inherent in brush-based cleaning while maintaining effective removal of sawing residue through the combination of liquid flow and high-frequency acoustic vibrations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If high pressure water jets are used to wash off loosened residue, then cleaning effectiveness is improved, but small packages may be dislodged from the pickhead

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidpackage dislodgement risk

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent infuses megasonic vibrations (high-frequency acoustic waves) into the cleaning liquid jet. This vibration energy enhances the cleaning effectiveness by disrupting and removing adhered sawing residue through acoustic cavitation and mechanical vibration effects, allowing lower overall pressure to be used compared to conventional high-pressure water jets, thereby reducing the risk of dislodging small packages.

Inventive Principle:

Principle #18Mechanical vibration

3Manufacturing precision

If megasonic vibrations are used to clean electronic packages, then particle removal effectiveness is improved, but only a limited area can be cleaned at once

Engineering Contradiction:

Improveparticle removal effectivenessVSAvoidcleaning area coverage

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent employs a linear array of multiple megasonic jet nozzles that can be moved relative to the pickhead carrying the array of electronic packages. This segmentation of the cleaning system into multiple movable jet units allows systematic coverage of the entire package array, overcoming the limited area coverage of a single stationary megasonic source while maintaining the high particle removal effectiveness of megasonic vibrations.

Inventive Principle:

Principle #1Segmentation

4Use of energy by moving object

If water flows at low speed in the megasonic cleaning tank, then energy consumption is reduced, but loosened residue may remain and re-adhere to package surfaces

Engineering Contradiction:

Improveenergy consumptionVSAvoidresidue removal completeness

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent uses periodic megasonic vibrations applied to the cleaning liquid jet to continuously disrupt and prevent re-adhesion of loosened sawing residue to package surfaces. The high-frequency acoustic cycles create repeated cavitation and vibration effects that keep particles suspended and removed, ensuring complete cleaning effectiveness even at lower water flow speeds that consume less energy.

Inventive Principle:

Principle #19Periodic action

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

Effectively removes sawing residue without dislodging packages, reduces maintenance needs, and shortens cleaning time while minimizing the risk of missing units and water usage, ensuring thorough and efficient cleaning with reduced operational complexity.

Implementation Method 1

Megasonic cleaning uses vibration frequencies of approximately 800 KHz to 1.8 MHz. Therefore, megasonic cleaning can be highly effective for removing particles having a particle size of about 1 micron or less.

Methodology Applied

Scientific EffectMegasonic vibration: Ultrasonic Vibration

Implementation Method 2

the water carrying the loosened sawing residue flows into a second water tank surrounding the first water tank

Methodology Applied

Scientific EffectGravity: Gravitation

Data Source

PatentUS8978673B2Megasonic cleaning system

Publication Date: 2015.03.17 ASM ASSEMBLY AUTOMATION LTD

AI summary

A system for cleaning semiconductor packages is provided which includes a pickhead that is configured to hold the semiconductor packages in an array arrangement and a plurality of nozzles, each of which is constructed and arranged to project a separate jet of cleaning fluid upwardly against the semiconductor packages. A megasonic energy generator is coupled for imparting megasonic energy to the cleaning fluid and a driving device drives relative movement between the plurality of nozzles and the pickhead to direct the said jets to clean the array of packages on the pickhead.