Flip-Chip Pad and Pillar Cavities for Extreme Fine-Pitch Joints
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The increasing functionality of ICs in electronic devices necessitates more power and signal connections, but the existing connectors between IC dies and substrates in flip chip components face reliability issues due to the large size of conductive pads, which become unreliable when made smaller, leading to solder bridging or failure when attempting to increase or decrease solder volume.
Innovation Solution
The design incorporates a copper pillar and nickel ring/collar structure, where the nickel ring/collar acts as a piston to increase the solder volume within a cavity in the copper pillar, reducing bridging and allowing for smaller conductive pads and pillars, enabling higher signal density by controlling solder distribution and containment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the conductive pads are made smaller to increase signal density, then the number of connections per unit area increases, but the reliability of solder joints deteriorates due to insufficient solder volume
Solution Approach 1:
The patent transitions from two-dimensional pad sizing to three-dimensional solder containment by introducing cavities within the conductive structures. The cavity in the conductive pad and the nickel ring/collar structure create vertical confinement of solder, allowing small footprint pads to accommodate sufficient solder volume through depth rather than surface area.
Solution Approach 2:
The nickel ring/collar is nested within the cavity of the conductive pad, and the solder is contained within the nickel ring/collar structure. This nested arrangement maximizes solder volume within the limited space of small conductive pads, enabling both high signal density and reliable solder joints.
2Reliability
If the solder volume is increased to improve joint reliability, then the reliability of solder joints improves, but solder bridging between adjacent connections occurs
Solution Approach 1:
The conductive pad is segmented into distinct functional zones: the cavity structure, the nickel ring/collar, and the solder region. This segmentation allows precise control over solder placement and volume, enabling sufficient solder for reliable joints while preventing overflow and bridging to adjacent connections.
Solution Approach 2:
The nickel ring/collar provides localized containment for the solder, creating a defined boundary that restricts solder flow to the intended connection area. This local quality control ensures that each solder joint has adequate volume without affecting neighboring joints, even at fine pitch configurations.
3Reliability
If the conductive pads are made larger to ensure reliable solder joints, then the reliability of solder joints improves, but the number of connections per unit area decreases
Solution Approach 1:
The patent utilizes the vertical dimension through cavity depth and nickel ring/collar height to accommodate solder volume, allowing the horizontal footprint of the conductive pads to be minimized. This enables high connection density while maintaining sufficient solder volume for reliable joints.
Solution Approach 2:
The invention changes the geometric parameters of the conductive structures by introducing cavities and nested rings, transforming the solder containment approach from surface-area-dependent to volume-dependent through vertical confinement. This parameter change enables small pad footprints with adequate solder capacity.
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 solution allows for a significantly higher number of connections per unit area without reliability issues, as the controlled solder distribution reduces bridging and enhances the reliability of solder joints, accommodating increased signal density and misalignment tolerances.
Implementation Method 1
the nickel ring/collar acts as a piston to increase the solder volume within a cavity in the copper pillar
Implementation Method 2
Each conductive ring includes a capillary formed along an axis of the conductive ring
Data Source
AI summary
An electronic component includes a device die and a substrate. The device die includes conductive contacts with conductive pillars conductively affixed to conductive contact. The conductive pillars include a cavity formed in an end of the conductive pillar opposite the conductive contact. The substrate includes of conductive pads that are each associated with one of the conductive contacts. The conductive pads include a conductive pad conductively affixed to the substrate, and a conductive ring situated within a cavity in the end conductive rings have a capillary formed along an axis of the conductive ring. A solder material fills the capillary of each of the conductive rings and the cavity formed in the end of the associated conductive pillars to form a conductive joint between the pillars and the conductive pads.