Stress-Tolerant Solder Bump Pattern for 2.5D Interposer
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Solution Overview
Problem
The 2.5D packaging approach for integrated circuit (IC) chips experiences mechanical stress due to thermal expansion mismatch between the silicon interposer and organic packaging substrate, leading to solder bump failure and delamination.
Innovation Solution
A microelectronic package design featuring larger diameter solder bumps in the peripheral region and smaller diameter solder bumps in the center region of the interposer, with the larger bumps capable of withstanding higher mechanical stresses and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a large surface area silicon interposer is used to enable multiple IC chips to be incorporated into a single package, then the functionality and integration density are improved, but mechanical stress increases due to thermal expansion mismatch between the silicon interposer and organic packaging substrate
Solution Approach 1:
The patent applies local quality by varying the solder bump diameter based on location: larger diameter solder bumps are used in the peripheral region where thermal expansion stress is highest, while smaller diameter solder bumps are used in the center region where stress is lower. This localized differentiation optimizes stress distribution and prevents solder bump failure without compromising the overall integration density enabled by the large interposer surface area.
2Ease of manufacture
If uniform small diameter solder bumps are used across the entire interposer surface, then manufacturing simplicity is maintained, but reliability decreases due to solder bump cracking and delamination under mechanical stress
Solution Approach 1:
The patent implements local quality by specifying that solder bumps in the peripheral region have a larger diameter than solder bumps in the center region. This location-dependent design directly addresses the reliability issue by providing enhanced mechanical strength where thermal expansion stress is most severe, while maintaining manufacturing feasibility through a relatively simple two-group classification system.
3Reliability
If larger diameter solder bumps are used in the peripheral region, then mechanical stress resistance and reliability are improved, but device complexity increases due to non-uniform solder bump configuration
Solution Approach 1:
The patent resolves the complexity issue by implementing a practical local quality approach: dividing the interposer surface into two distinct regions (peripheral and center) with two corresponding solder bump diameter specifications. This binary classification provides sufficient stress management improvement without requiring complex continuous variations or multiple diameter groups, thus limiting the increase in device complexity while achieving the reliability goal.
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 design significantly enhances the mechanical support and reliability of the microelectronic package by distributing mechanical stresses effectively, preventing solder bump cracking and delamination.
Implementation Method 1
significant mechanical stresses can occur in a 2.5D chip package during operation due to the significant mismatch in coefficient of thermal expansion of the silicon interposer and the organic packaging substrate
Data Source
AI summary
A microelectronic package includes larger diameter solder bumps and smaller diameter solder bumps for coupling an interposer to a packaging substrate. The larger diameter solder bumps are positioned on a peripheral surface of the interposer and the smaller diameter solder bumps are positioned on a center surface of the interposer. The solder bumps positioned in the peripheral region can more reliably withstand the higher mechanical stresses that occur in this peripheral region during operation of the microelectronic package.