Flip-Chip Solder Sealing for Hermetic Electronic Device Cavity

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Solution Overview

Problem

Existing electronic device fabrication methods face challenges in achieving reduced size and cost while maintaining high airtightness and robustness, particularly in flip-chip bonding techniques, where foreign material contact and moisture ingress can lead to malfunction, and current sealing methods either compromise on airtightness or increase costs and shape restrictions.

Innovation Solution

A method involving flip-chip mounting of device chips on a substrate with solder supplied between adjacent chips, applying heat and pressure to create a solder sealing portion with a contact angle greater than 90°, resulting in a robust, hermetically sealed cavity with high electric shielding effectiveness and bonding strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If sealing resin is used to reduce size and cost, then manufacturing cost and device size are reduced, but airtightness deteriorates

Engineering Contradiction:

Improvemanufacturing costVSAvoidairtightness

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent combines sealing and outer shape formation into a single integrated structure using solder. The solder serves dual purposes: providing hermetic sealing for the device chip and simultaneously forming the outer package shape, eliminating the need for separate sealing resin layers and achieving both cost reduction and high airtightness.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the material parameter from organic sealing resin to metallic solder, which fundamentally alters the sealing performance. Solder provides superior airtightness and electrical shielding while maintaining compatibility with flip-chip bonding processes, resolving the contradiction between cost reduction and airtightness maintenance.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If sealing resin is used to form outer shape, then device size is reduced, but electric shielding effectiveness deteriorates

Engineering Contradiction:

Improvedevice sizeVSAvoidelectric wave interference

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent changes the material parameter from non-conductive sealing resin to conductive solder, which provides both mechanical encapsulation and electrical shielding. The metallic nature of solder creates an effective barrier against external electric waves while maintaining compact device dimensions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs solder as a composite functional material that simultaneously provides mechanical sealing, structural support, and electromagnetic shielding. This multi-functional material replaces the need for separate shielding layers, achieving high-frequency performance in a compact form factor.

Inventive Principle:

Principle #40Composite materials

3Device complexity

If solder sealing is performed simultaneously with chip mounting, then manufacturing process is simplified, but sealing reliability deteriorates due to metal layer melting

Engineering Contradiction:

Improvemanufacturing process complexityVSAvoidsealing reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent performs solder sealing as a preliminary step before chip mounting. By pre-forming the solder sealing structure on the substrate, subsequent chip placement and reflow soldering do not compromise the sealing integrity, as the sealing has already been established at a lower temperature stage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent segments the manufacturing process into distinct stages: first forming the solder sealing structure, then mounting chips, and finally performing reflow soldering for bump bonding. This segmentation allows each process to be optimized independently, preventing metal layer melting during sealing while maintaining process simplicity.

Inventive Principle:

Principle #1Segmentation

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

This approach enables the fabrication of electronic devices with high airtightness, robust bonding, and reduced size and cost, while ensuring effective electric shielding and reliable sealing by defining cavities between device chips and substrates using solder.

Implementation Method 1

applying heat and pressure on the solder, and a contact angle of the device chip and the solder is greater than 90° with the solder melted

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

supplying solder between adjacent device chips by supplying the solder on the device chips and applying heat and pressure on the solder

Methodology Applied

Scientific EffectSoldering: Soldering

Implementation Method 3

a contact angle of the device chip and the solder is greater than 90° with the solder melted

Methodology Applied

Scientific EffectSurface tension: Surface Tension

Data Source

PatentUS8093101B2Electronic device and method of fabricating the same

Publication Date: 2012.01.10 TAIYO YUDEN KK

AI summary

There is provided a method of fabricating an electronic device including flip-chip mounting a device chip on a substrate, and supplying solder between adjacent device chips by supplying the solder on the device chips and applying heat and pressure on the solder, and a contact angle of the device chip and the solder is greater than 90° with the solder melted.