Narrowed Pillar Interconnects Mitigate Thermomechanical Stress
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Solution Overview
Problem
Semiconductor packages face mechanical stress and potential cracking due to thermal expansion mismatches between the semiconductor die and the substrate during bonding and thermal cycling, leading to reliability issues and yield loss.
Innovation Solution
The implementation of interconnect structures with pillar structures featuring narrowed portions to increase flexibility and dissipate stress, reducing the transmission of thermomechanical stress to the semiconductor die, thereby enhancing package reliability and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the semiconductor package is heated and cooled during bonding and thermal cycling, 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 interconnect structure is divided into multiple segments including a pillar portion, a narrowed portion, and a pad portion. This segmentation allows each segment to have different mechanical properties, with the narrowed portion acting as a stress-absorbing element that accommodates thermal expansion differences between the semiconductor die and substrate during heating and cooling cycles.
Solution Approach 2:
The cross-sectional area of the interconnect structure is changed along its length, with the narrowed portion having a smaller cross-sectional area than the pillar and pad portions. This parameter change creates a gradient in stiffness that allows the structure to flex and absorb stress while maintaining electrical connectivity, reducing the transmission of thermomechanical stress to the bond pads.
2Reliability
If the semiconductor package undergoes thermal cycling, then the bond material attaches to the substrate, but cracking occurs at the interface between the interconnect structures and the semiconductor die
Solution Approach 1:
The narrowed portion is designed in advance as a stress-absorbing feature that acts as a cushion before stress can propagate to the bond pads. This pre-engineered weak point accommodates thermal expansion differences and mechanical stresses during thermal cycling, preventing stress concentration at the vulnerable interface between the interconnect structures and the semiconductor die.
Solution Approach 2:
The interconnect structure incorporates a flexible narrowed portion that can bend and deform to accommodate thermal expansion differences between components. This flexible section acts as a compliant element that absorbs stress during thermal cycling, preventing the rigid stress transmission that would otherwise cause cracking at the bond pad interface.
3Ease of manufacture
If uniform pillar structures are used for interconnect, then manufacturing is simplified, but stress concentration occurs at the interface with the semiconductor die
Solution Approach 1:
Instead of using a uniform pillar structure throughout, the interconnect is designed with local quality variations: the narrowed portion has a different cross-sectional area than the pillar and pad portions. This local variation in geometry is strategically placed at the stress-prone interface region to provide stress absorption, while the rest of the structure maintains simpler dimensions for manufacturing.
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 narrowed pillar structures effectively absorb and dissipate stress, reducing the likelihood of cracking and mechanical failure at the interface between the interconnect structures and the semiconductor die, thereby improving the reliability and yield of semiconductor packages.
Implementation Method 1
The narrowed pillar structures effectively absorb and dissipate stress
Implementation Method 2
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
Data Source
AI summary
Semiconductor devices having interconnect structures with narrowed portions 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 an end portion away from the semiconductor die, the end portion having a first cross-sectional area. The pillar structure can further include a narrowed portion between the end portion and the semiconductor die, the narrowed portion having a second cross-sectional area less than the first-cross-sectional area of the end portion. A bond material can be coupled to the end portion of the pillar structure.