Heterogeneous Solder Joint Coating for Creep Prevention

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Solution Overview

Problem

Semiconductor devices with traditional solder joints are prone to failures such as solder creep and solder bleed out, which can lead to increased electrical resistance or short circuits, especially in high-current and high-voltage applications, necessitating improved solder joint technologies.

Innovation Solution

A heterogeneous solder joint is fabricated using a solder material with a first metal composition coated by a second metal composition that has greater stiffness and/or a higher melting point, where the coating is applied to at least partially cover the solder material, enhancing the joint's mechanical and thermal stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional solder joint is used, then the manufacturing process is simple, but the solder joint is prone to failures such as solder creep and solder bleed out, leading to increased electrical resistance or short circuits

Engineering Contradiction:

Improvesolder joint reliabilityVSAvoidsolder joint structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The solder joint uses a composite structure consisting of a solder material (first metal composition) and a coating material (second metal composition) with different properties. The coating material has greater stiffness and/or higher melting point than the solder material, creating a heterogeneous solder joint that combines the advantages of both materials to prevent solder creep and bleed out while maintaining electrical conductivity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The coating material is applied to at least partially cover the solder material, providing localized protection where it is most needed. This allows the solder joint to have different properties in different regions: the solder material provides electrical conductivity and bonding, while the coating material provides mechanical strength and prevents solder migration in critical areas.

Inventive Principle:

Principle #3Local quality

2Strength

If a coating with greater stiffness and higher melting point is applied to the solder material, then mechanical strength and thermal resistance are improved, but the manufacturing process becomes more complex

Engineering Contradiction:

Improvesolder joint mechanical strengthVSAvoidsolder joint fabrication

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The coating material is applied to the solder material before the final soldering process. This preliminary coating step ensures that the protective layer is in place before the solder material is molten, preventing solder creep and bleed out during the soldering process itself and eliminating the need for additional post-soldering protection steps.

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If a heterogeneous solder joint with coating is used, then solder creep and bleed out are prevented, but the manufacturing process requires additional coating steps

Engineering Contradiction:

Improvesolder joint compositional stabilityVSAvoidfabrication process

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The coating application and soldering processes are merged into a single integrated process flow. The coating is applied to the solder material, and then both the coated solder material and the semiconductor die are soldered together in one step, eliminating the need for separate coating and soldering operations and reducing overall process complexity.

Inventive Principle:

Principle #5Merging (Combining)

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 heterogeneous solder joint effectively prevents solder creep and bleed out, maintaining electrical integrity and reliability in high-stress semiconductor devices by providing improved mechanical strength and thermal resistance.

Implementation Method 1

a coating comprising a second metal composition, different from the first metal composition, the coating at least partially covering the solder material, wherein the second metal composition has a greater stiffness and/or a higher melting point than the first metal composition

Methodology Applied

Scientific EffectMechanical constraint:

Implementation Method 2

the second metal composition has a greater stiffness and/or a higher melting point than the first metal composition

Methodology Applied

Scientific EffectThermal barrier:

Data Source

PatentUS11682644B2Semiconductor device with a heterogeneous solder joint and method for fabricating the same

Publication Date: 2023.06.20 INFINEON TECHNOLOGIES AG

AI summary

A method for fabricating a semiconductor device with a heterogeneous solder joint includes: providing a semiconductor die; providing a coupled element; and soldering the semiconductor die to the coupled element with a first solder joint. The first solder joint includes: a solder material including a first metal composition; and a coating including a second metal composition, different from the first metal composition, the coating at least partially covering the solder material. The second metal composition has a greater stiffness and/or a higher melting point than the first metal composition.