Core-Shell Die-Attach Material for Low-Voiding Electromigration Resistance
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Solution Overview
Problem
Current die-attach materials for semiconductor devices face challenges such as high cost, risk of electromigration, voiding/porosity, thermo-mechanical stresses, and failure to meet lead-free certification standards, particularly in wide band gap semiconductor applications.
Innovation Solution
A die-attach material comprising core-shell particles with a conducting core and an alloy shell, including elements like tungsten, cobalt, or molybdenum, which segregate into grain boundaries during bonding to enhance mechanical, thermal, and electrical properties, and reduce oxidation, forming an intermetallic compound to prevent electro-migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional die-attach materials are used, then cost is reduced, but reliability deteriorates due to electromigration and voiding/porosity
Solution Approach 1:
The patent uses core-shell particles with a conducting core (e.g., copper, silver) and an alloy shell (e.g., silver-tungsten, silver-cobalt) to create a composite material that combines the high conductivity of the core with the grain boundary blocking properties of the shell, thereby improving electromigration resistance while maintaining cost-effectiveness
Solution Approach 2:
The alloy shell is applied locally on the surface of the conducting core, creating a layered structure where the core provides bulk conductivity and the shell provides localized grain boundary protection, allowing the material to achieve high reliability without completely replacing the cost-effective core material
2Reliability
If conventional die-attach materials are used, then manufacturing is simplified, but reliability deteriorates due to thermo-mechanical stresses
Solution Approach 1:
The core-shell composite structure combines materials with different thermal and mechanical properties, where the conducting core provides thermal conductivity and the alloy shell provides mechanical strength and stress resistance, enabling the material to withstand thermo-mechanical stresses better than conventional homogeneous materials
Solution Approach 2:
The patent modifies the material parameters by introducing an alloy shell with specific composition (e.g., tungsten, cobalt, or molybdenum content) to change the thermal expansion coefficient and mechanical strength, allowing the material to better match the substrate and reduce thermo-mechanical stresses
3Reliability
If core-shell particles with alloy shell are used, then reliability is improved, but manufacturing precision is challenged due to shell formation complexity
Solution Approach 1:
The alloy shell is pre-formed on the core particles before the sintering process, ensuring that the protective shell structure is already in place to prevent oxidation and block grain boundary diffusion during subsequent high-temperature processing, thereby improving aging stability
Solution Approach 2:
The patent controls the shell formation by adjusting parameters such as shell thickness, alloy composition, and deposition method, allowing precise control over the shell properties to achieve the desired reliability without excessive manufacturing complexity
4Reliability
If lead-free materials are used, then certification compliance is improved, but manufacturing precision is worsened due to difficulty in achieving low voiding/porosity
Solution Approach 1:
The core-shell composite structure with its dual-material composition facilitates better packing density and reduced void formation during sintering, as the shell material fills gaps between particles more effectively, achieving low porosity in lead-free formulations
Solution Approach 2:
The patent optimizes sintering parameters such as temperature, pressure, and atmosphere based on the specific core-shell composition to achieve dense consolidation and minimize voiding/porosity in lead-free die-attach materials, ensuring compliance with certification standards
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 die-attach material provides improved aging stability, reduced defects and voids, lower risk of electromigration, and higher thermal, mechanical, and electrical properties, while being lead-free and compliant with certain certification standards.
Implementation Method 1
The second element may segregate into one or more grain boundaries in the die-attach material during bonding of the die-attach material
Implementation Method 2
The shell may include an alloy that reduces oxidation of the core
Implementation Method 3
forming an intermetallic compound to prevent electro-migration
Data Source
AI summary
Die-attach materials are provided. In one example, the die-attach material may include a plurality of core-shell particles. Each core-shell particle may include a core and a shell on the core. The core may include a conducting material. The shell may include an alloy. The alloy may include a first element and a second element. The second element may segregate into one or more grain boundaries in the die-attach material during bonding of the die-attach material.