Pyramid Bump Structure for Flip-Chip Yield
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Solution Overview
Problem
Conventional flip-chip package technologies experience yield rate reductions due to short phenomena caused by conductive particles gathering between adjacent bumps during the lamination process, which affects the flow rate and efficiency of anisotropic conductive paste.
Innovation Solution
A pyramid bump structure with a conductive block and an oblique pyramid insulating layer is used, where the lateral surface of the conductive block is covered by the insulating layer, allowing the bumps to rapidly embed into the anisotropic conductive paste and preventing conductive particles from gathering between adjacent bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bumps are used in flip-chip package technology, then the bonding process can be completed, but conductive particles gather between adjacent bumps causing short phenomena and reduced yield rate
Solution Approach 1:
The bump structure is segmented into distinct functional zones: a conductive block for electrical connection and an insulating layer with tapered outer surface for particle control. This segmentation allows the conductive particles to be confined to specific regions rather than gathering between adjacent bumps, eliminating short phenomena and improving yield rate.
Solution Approach 2:
The insulating layer is applied selectively on the lateral surface of the conductive block with a tapered outer surface, creating local quality differentiation. This localized insulating structure with varying thickness controls the distribution of conductive particles in specific areas, preventing them from migrating to regions between adjacent bumps while maintaining electrical connectivity where needed.
2Productivity
If anisotropic conductive paste is used for lamination, then electrical and mechanical connections can be established, but the flow rate is insufficient and conductive particles do not distribute properly
Solution Approach 1:
The insulating layer features a tapered outer surface with curved geometry that gradually increases in diameter from bottom to top. This curved surface guides the flow of anisotropic conductive paste and directs conductive particles along the taper toward the top region, improving both flow rate and particle distribution precision by preventing particle accumulation in unwanted areas.
Solution Approach 2:
The insulating layer acts as an intermediary structure between the conductive block and the surrounding environment. It mediates the interaction between the anisotropic conductive paste and the bump structure, controlling paste flow rate and directing particle distribution through its tapered geometry, thereby achieving proper particle confinement without direct contact between adjacent conductive blocks.
3Reliability
If the lateral surface of the conductive block is exposed, then electrical connection is maximized, but conductive particles can cause short circuits between adjacent bumps
Solution Approach 1:
The insulating layer is applied selectively on the lateral surface of the conductive block, creating local quality differentiation. This localized insulating structure with varying thickness controls the distribution of conductive particles in specific areas, preventing them from migrating to regions between adjacent bumps while maintaining electrical connectivity where needed.
Solution Approach 2:
The insulating layer exhibits asymmetric distribution with a tapered outer surface that is thicker at the top and thinner at the bottom. This asymmetric geometry allows the structure to maintain electrical connection reliability at the base while preventing particle-induced short circuits at the upper regions where particles tend to accumulate during lamination.
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 pyramid bump structure enhances the flow rate of the anisotropic conductive paste and prevents short phenomena, thereby increasing the yield rate of the package process by ensuring effective electrical and mechanical connections.
Implementation Method 1
the pyramid bump structure may rapidly embed into the anisotropic conductive paste to increase the flow rate of the anisotropic conductive paste
Implementation Method 2
a plurality of conductive particles of the anisotropic conductive paste is extruded by the pyramid bump structure to force mentioned conductive particles to gather between adjacent pyramid bumps
Data Source
AI summary
A pyramid bump structure for electrically coupling to a bond pad on a carrier comprises a conductive block disposed at the bond pad and an oblique pyramid insulation layer covered at one side of the conductive block. The oblique pyramid insulation layer comprises a bottom portion and a top portion, and outer diameter of the oblique pyramid insulation layer is tapered from the bottom portion to the top portion. When the carrier is connected with a substrate and an anisotropic conductive film disposed at the substrate, the pyramid bump structure may rapidly embed into the anisotropic conductive film to raise the flow rate of the anisotropic conductive film. Further, a short phenomenon between adjacent bumps can be avoided to raise the yield rate of package process.