Electrowetting Underfill Method for Semiconductor Packages

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Solution Overview

Problem

The existing underfill methods for semiconductor packages, particularly those using capillary action, face inefficiencies and incomplete filling due to surface tension and viscosity issues, leading to voids and defects when the bump height is lowered, and can result in filler overflow and contamination.

Innovation Solution

An underfill method and apparatus that utilizes electrowetting by charging a filler with an electric field to control wetting, enhancing filling efficiency by applying the filler between a substrate and a semiconductor device under an electric potential difference, thereby improving the permeation and distribution of the filler.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If capillary action is used for underfill, then the filling process is simple, but the filling speed is slow and incomplete filling occurs

Engineering Contradiction:

Improvefilling process simplicityVSAvoidfilling speed

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent replaces the passive capillary action mechanism with an active electrowetting-based liquid ejection system. By applying voltage to charge the filler and using electric field interaction, the system achieves controlled, high-speed liquid ejection that overcomes the slow and passive nature of capillary action while maintaining manufacturing simplicity through automated voltage control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state and properties of the filler by charging it with electric charge. This transformation enables the filler to respond to electric fields, allowing for controlled ejection and improved filling speed. The charged filler's interaction with the electric field provides adjustable parameters (voltage, charge density) that optimize both speed and completeness of filling.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If capillary action is used for underfill, then no additional equipment is needed, but incomplete filling and voids occur

Engineering Contradiction:

Improveequipment requirementsVSAvoidfilling completeness

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent incorporates feedback control through voltage adjustment based on filling progress. The system monitors the filling process and adjusts the applied voltage to ensure complete filling, preventing void formation. This feedback mechanism enhances reliability by adapting the ejection parameters to the actual filling state.

Inventive Principle:

Principle #23Feedback

3Reliability

If large amount of filler is applied at once, then void formation is prevented, but filler overflow and contamination occur

Engineering Contradiction:

Improvevoid preventionVSAvoidfiller contamination

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent uses periodic or controlled incremental liquid ejection instead of applying a large amount of filler at once. By charging the filler and ejecting it in controlled amounts through voltage application, the system prevents overflow and contamination while ensuring complete filling through multiple controlled doses, thereby preventing void formation.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent employs dynamic control of the liquid ejection process through adjustable voltage parameters. The system can adapt the ejection rate and total amount of filler based on real-time conditions, allowing precise control to prevent both voids and overflow. This dynamic adjustment optimizes the balance between complete filling and contamination prevention.

Inventive Principle:

Principle #15Dynamics

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 method ensures faster and more complete filling of the gap between the substrate and semiconductor device, reducing the risk of voids and defects, and prevents filler overflow, thereby enhancing the reliability and performance of semiconductor packages.

Implementation Method 1

utilizes electrowetting by charging a filler with an electric field to control wetting

Methodology Applied

Scientific EffectElectrowetting: Electrowetting

Implementation Method 2

capillary underfill for filling based on capillary action in between the semiconductor device and the substrate

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 3

charging a filler to be filled in between the substrate and a device; applying the filler to the substrate; and subjecting the applied filler to an electric field

Methodology Applied

Scientific EffectElectrohydrodynamics: Electrohydrodynamics

Data Source

PatentUS11355360B2Underfill method for semiconductor package

Publication Date: 2022.06.07 ENJET CO LTD

AI summary

Disclosed are an underfill method and apparatus for a semiconductor package, the underfill method includes loading a substrate; charging a filler to be filled in between the substrate and a device; applying the filler to the substrate; and subjecting the applied filler to an electric field.