Semiconductor Device Frame Cap Jointing for Hermetic Sealing

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Solution Overview

Problem

Existing semiconductor devices with a sealed structure using a frame and cap joined by solder face challenges in preventing foreign substances, such as solder oxide films and melted solder, from entering the cavity, which can compromise hermetic sealing and increase manufacturing costs.

Innovation Solution

A semiconductor device design where the joint between the frame and cap is formed outside the contact surface, using a gold-tin alloy joint created by plating and heating, eliminating the need for solder scrubbing and reducing the risk of foreign substances entering the cavity, while also allowing for adjustment of the cavity's capacity to maintain high-frequency characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the frame and cap are joined together by solder to form a hermetically sealed cavity, then hermetic sealing is achieved, but foreign substances generated from the solder may enter the cavity

Engineering Contradiction:

Improvehermetic sealingVSAvoidforeign substance entry

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The joint structure is segmented into two distinct regions: the contact surface between frame and cap that forms the hermetic seal, and the joint formation area where solder is applied outside the contact surface. This segmentation allows the sealing function and joining function to be spatially separated, preventing solder and its byproducts from contaminating the sealed cavity while maintaining hermetic integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The harmful element (solder and its generated foreign substances) is extracted from the cavity interior by positioning the joint formation area outside the contact surface. The solder is applied to the outer peripheral surfaces of the frame and cap rather than on the contact surface, thereby removing the source of contamination from the sealed environment.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If solder is used to join the frame and cap, then hermetic sealing is achieved, but solder oxide films and melted solder may enter the cavity

Engineering Contradiction:

Improvehermetic sealingVSAvoidcavity contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The contact surface acts as an intermediary barrier between the joint formation area and the cavity interior. By positioning the solder joint outside the contact surface, the contact surface serves as a protective mediator that prevents solder oxide films and melted solder from entering the cavity, while still allowing hermetic sealing to occur at the contact interface.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the joint between frame and cap is formed on the contact surface, then hermetic sealing is achieved, but the manufacturing process becomes complex requiring solder scrubbing

Engineering Contradiction:

Improvehermetic sealingVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of forming the solder joint on the contact surface and then removing excess solder through scrubbing, the approach is inverted by forming the joint outside the contact surface from the beginning. This inversion eliminates the need for solder scrubbing and other complex manufacturing steps while ensuring that no solder or oxide films can enter the cavity.

Inventive Principle:

Principle #13The other way round (Inversion)

4Reliability

If solder is used for joining the frame and cap, then hermetic sealing is achieved, but oxygen concentration requirements increase

Engineering Contradiction:

Improvehermetic sealingVSAvoidmanufacturing efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The oxygen-related contamination issue is extracted from the sealing process by positioning the solder joint outside the contact surface. Since the joint formation occurs in a region separate from the hermetic seal, the oxygen concentration in the sealing atmosphere can be reduced or eliminated without affecting the joint quality, thereby improving manufacturing efficiency and reducing process complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

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 design effectively prevents foreign substances from entering the cavity, simplifies the manufacturing process, reduces oxygen concentration requirements, and enhances the reliability and longevity of high-frequency modules by ensuring hermetic sealing without the need for solder scrubbing, thus improving productivity and maintaining high-frequency performance.

Implementation Method 1

a joint that joins the frame and the cap outside a contact surface between the frame and the cap

Methodology Applied

Scientific EffectSoldering: Soldering

Implementation Method 2

using a gold-tin alloy joint created by plating and heating

Methodology Applied

Scientific EffectHeating: Heating

Data Source

PatentUS10211116B2Semiconductor device

Publication Date: 2019.02.19 MITSUBISHI ELECTRIC CORP

AI summary

A semiconductor device according to the present invention includes a mounting section provided with a chip mounting region for mounting a semiconductor chip, a frame provided in the mounting section so as to surround the chip mounting region, a cap disposed in contact with the frame so as to cover a space surrounded by the chip mounting region and the frame and a joint that joins the frame and the cap outside a contact surface between the frame and the cap.