Composite Interconnect Pillars for Thermomechanical Stress Relief
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Solution Overview
Problem
Semiconductor packages face significant mechanical stress due to thermal expansion mismatches between the semiconductor die and the substrate, leading to potential cracking and rendering the package inoperable.
Innovation Solution
The implementation of a pillar structure with conductive elements made of high-modulus materials, such as copper or nickel, surrounded by a lower-modulus conductive material, such as solder, to create a more flexible interconnect structure that can absorb and dissipate thermomechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the semiconductor package is heated and cooled during bonding operation, then the bond material is reflowed and attached to the substrate, but significant mechanical stress is induced between the semiconductor die and the substrate due to thermal expansion mismatch
Solution Approach 1:
The patent changes the physical state and mechanical properties of the interconnect structure by transitioning from a rigid single-material pillar to a composite structure with a solder joint, altering the stress distribution characteristics during thermal cycling
Solution Approach 2:
The patent employs a composite interconnect structure consisting of a conductive pillar (first material) and a solder joint (second material), where each material contributes different mechanical properties to reduce overall thermomechanical stress while maintaining electrical conductivity
2Reliability
If conventional rigid conductive pillars are used for bonding, then electrical connection is achieved, but the structure is prone to cracking under thermomechanical stress
Solution Approach 1:
The patent uses a composite structure with a rigid conductive pillar for electrical conductivity and a softer solder joint for stress absorption, combining materials with different mechanical properties to achieve both electrical function and stress resistance
Solution Approach 2:
The patent modifies the mechanical parameters of the interconnect by introducing a solder joint with different elastic modulus and ductility, enabling the structure to deform plastically under stress rather than fracturing brittlely
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 configuration reduces the overall stiffness of the interconnect structure, allowing it to bend and deform under stress, thereby reducing the mechanical stress applied to the semiconductor die and increasing the reliability and yield of semiconductor packages.
Implementation Method 1
heating the semiconductor package and/or subsequently cooling the semiconductor package can induce significant mechanical stress between the semiconductor die and the substrate due to a mismatch in the coefficients of thermal expansion of these components
Implementation Method 2
allowing it to bend and deform under stress, thereby reducing the mechanical stress applied to the semiconductor die
Data Source
AI summary
Semiconductor devices having interconnect structures with conductive elements configured to mitigate thermomechanical stresses, and associated systems and methods, are disclosed herein. In one embodiment, a semiconductor package includes a semiconductor die and a pillar structure coupled to the semiconductor die. The pillar structure can include a plurality of conductive elements made of a first conductive material having a first elastic modulus. The pillar structure can further include a continuous region of a second conductive material at least partially surrounding the plurality of conductive elements. The second conductive material can have a second elastic modulus less than the first elastic modulus.