High Bandwidth Memory Bump Crack Detection via Dummy Signal Lines
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Solution Overview
Problem
High bandwidth memories are prone to cracks in bumps during assembly or delivery due to external forces, which can lead to failures in connectivity and data transmission.
Innovation Solution
Incorporation of dummy bump groups with spaced-apart dummy bumps and signal lines for sequential transmission of signals to detect cracks, allowing for the identification of bump cracks through a bump crack test operation, enhancing the reliability of the memory system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bumps are arranged at edge regions of stacked dies for connectivity, then device functionality is achieved, but cracks occur due to high stress from external forces
Solution Approach 1:
The patent segments the bump structure by introducing dummy bumps that are spatially separated from real bumps by a predetermined distance. This segmentation allows the dummy bumps to serve as stress-absorbing elements while real bumps maintain connectivity function, resolving the contradiction between connectivity reliability and bump strength.
Solution Approach 2:
The patent applies beforehand cushioning by placing dummy bumps adjacent to real bumps at edge regions. These dummy bumps act as cushioning elements that absorb external stresses before they can damage the real bumps, thereby protecting the connectivity function while withstanding mechanical forces.
2Difficulty of detecting and measuring
If dummy bumps are added for crack detection, then bump crack detectability is improved, but device complexity increases
Solution Approach 1:
The patent uses dummy bumps as intermediary elements between external stress sources and real bumps. These intermediaries facilitate crack detection by serving as test structures that can be monitored for stress-induced changes, improving detectability without significantly complicating the overall device architecture.
Solution Approach 2:
The patent creates simplified copies of real bumps in the form of dummy bumps. These copies replicate the stress-response characteristics of real bumps but can be easily monitored for crack detection purposes, thereby improving detectability while adding minimal structural complexity.
Data Source
AI summary
High bandwidth memories and systems including the same may include a buffer die, a plurality of memory dies stacked on the buffer die, a plurality of dummy bump groups in edge regions of the buffer die and the plurality of memory dies, and a plurality of signal line groups. Each of the plurality of dummy bump groups includes dummy bumps spaced apart from each other between each pair of adjacent dies and configured to connect the two adjacent dies to each other. Each of the signal line groups includes a plurality of signal lines configured to transmit a corresponding signal among an input signal and a plurality of bump crack detection signals applied to an input dummy bump of each of the plurality of dummy bump groups via sequential transmission through the plurality of dummy bumps to an output dummy bump during a bump crack test operation.