Conductive Pillar Trenches for Solder Control and Oxidation Prevention
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Solution Overview
Problem
The formation of conductive pillars on semiconductor substrates for connecting external devices is prone to issues such as short-circuits due to excessive conductive material and cold joints from insufficient material, and is vulnerable to oxidation and delamination, especially when the sidewalls are exposed.
Innovation Solution
The conductive pillars are designed with trenches around their circumference to passively guide and control the conductive material, storing excess material and ensuring sufficient connection, while reducing oxidation risks by encapsulating the sidewalls, thereby preventing bridging and ensuring reliable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive material is placed onto circular conductive pillars, then electrical connection is provided, but excessive material causes short-circuits and insufficient material causes cold joints
Solution Approach 1:
The conductive pillar is segmented by introducing trenches that divide the pillar structure into distinct regions. These trenches create separate zones for conductive material placement, allowing precise control over material distribution and preventing both excessive material (short-circuits) and insufficient material (cold joints).
Solution Approach 2:
The trenches create local variations in the pillar structure, with different regions serving different functions: the central region accommodates the conductive material while the trench regions provide containment and control. This local differentiation enables precise control of conductive material quantity and placement without affecting the entire pillar structure.
2Ease of operation
If sidewalls of conductive pillar are exposed to ambient atmosphere, then access for bonding is provided, but oxidation occurs leading to delamination
Solution Approach 1:
The trenches create protected regions that shield the conductive material and pillar interfaces from ambient atmosphere. By confining the conductive material within trench structures, the sidewalls are effectively isolated from oxygen exposure, preventing oxidation while still allowing bonding operations to proceed on the exposed top surfaces.
3Adaptability or versatility
If conductive pillars are formed in cylindrical shape, then accommodation of spherical bumps is enabled, but interface vulnerability to cracks increases
Solution Approach 1:
The cylindrical pillar is segmented by trenches into distinct regions, creating a structured interface that distributes mechanical stresses more effectively. The trenches act as stress relief features that prevent crack propagation along the pillar-bump interface, while the overall cylindrical shape remains intact for bump accommodation.
Solution Approach 2:
The introduction of trenches transforms the symmetric cylindrical shape into an asymmetric structure with differentiated regions. This asymmetry creates specific zones for stress distribution and crack prevention, while maintaining the essential cylindrical form factor for bump compatibility.
Data Source
AI summary
A system and method for conductive pillars is provided. An embodiment comprises a conductive pillar having trenches located around its outer edge. The trenches are used to channel conductive material such as solder when a conductive bump is formed onto the conductive pillar. The conductive pillar may then be electrically connected to another contact through the conductive material.