Package on Package Structure Using Composite Metallic Bumps
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Solution Overview
Problem
The semiconductor industry faces challenges in manufacturing package on package (PoP) structures due to the need for smaller, more integrated electronic components, which requires new packaging technologies that can efficiently bond semiconductor dies with minimal area and height, while maintaining reliability and preventing oxidation of metallic structures.
Innovation Solution
The method involves forming bumps with a metallic structure and minor elements on a substrate, bonding a semiconductor die to the substrate, and then bonding a semiconductor die package to the bumps using a reflow process, with optional passivation layers and bonding layers to enhance bonding and prevent oxidation, and using a molded underfill material to isolate heat and reduce thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If package on package structure is used to increase integration density, then more components can be integrated into smaller area, but manufacturing complexity and difficulty increase
Solution Approach 1:
The PoP structure is divided into separate bottom and top packages that are manufactured independently and then bonded together. This segmentation allows each package to be optimized and manufactured separately using existing processes, reducing overall manufacturing complexity while achieving high integration density.
Solution Approach 2:
The top package is placed and bonded directly onto the bottom package, creating a nested vertical configuration. This nesting approach enables increased integration density by utilizing the vertical dimension rather than expanding horizontally, while maintaining manageable manufacturing steps.
2Area of moving object
If smaller packages are used to reduce area, then less space is required, but bonding reliability becomes more difficult to maintain
Solution Approach 1:
The bonding interface uses a composite structure involving metallic bumps with specific material compositions (including minor elements dispersed in the metallic structure) and optional bonding layers. This composite material approach enhances bonding reliability in small packages by improving mechanical strength, electro-migration resistance, and thermal performance.
Solution Approach 2:
The patent applies different material properties and structures at the bonding interface versus the bulk package materials. The bonding region features specialized bump structures with dispersed minor elements and optional bonding layers to optimize local bonding reliability, while the rest of the package maintains standard construction.
3Quantity of substance
If metallic structures are used for electrical connection, then conductivity is improved, but oxidation resistance becomes a concern
Solution Approach 1:
The metallic bumps are constructed as composite structures with a base metal providing electrical conductivity and dispersed minor elements providing oxidation resistance. This composite metallic structure maintains high conductivity while resisting oxidation, solving the contradiction between conductivity and oxidation resistance.
Solution Approach 2:
Optional bonding layers are introduced as intermediary materials between the metallic bumps and the semiconductor dies. These bonding layers serve as mediators that provide both electrical connectivity and protection against oxidation, allowing the metallic structures to maintain conductivity without direct exposure to oxidizing environments.
4Area of moving object
If multiple semiconductor dies are bonded together, then integration density increases, but thermal stress and heat transfer between dies increase
Solution Approach 1:
The metallic bumps and bonding layers serve as thermal intermediaries between the semiconductor dies. These intermediate structures are designed to manage heat transfer, providing controlled thermal pathways that reduce thermal stress accumulation while maintaining electrical connectivity between the stacked dies.
Solution Approach 2:
The patent modifies thermal parameters by controlling the material composition and structure of the bonding interface. The metallic bumps with dispersed minor elements and optional bonding layers are designed with specific thermal properties that optimize heat dissipation and reduce thermal stress, allowing multiple dies to be bonded together without excessive thermal accumulation.
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 approach allows for increased integration density, improved mechanical and electro-migration resistance, and enhanced reliability of the PoP structure by preventing metal oxidation and reducing thermal transfer between semiconductor dies, while allowing for easier mounting and singulation.
Implementation Method 1
The bump includes a metallic structure and a plurality of minor elements dispersed in the metallic structure
Implementation Method 2
bonding a semiconductor die package to the bumps using a reflow process
Implementation Method 3
using a molded underfill material to isolate heat and reduce thermal stress
Data Source
AI summary
A package on package structure includes a first substrate having a first region and a second region, a bump formed on the first region of the first substrate, a first semiconductor die bonded to the second region of the first substrate, and a semiconductor die package bonded to the first substrate. The bump includes a metallic structure and a plurality of minor elements dispersed in the metallic structure. The semiconductor die package includes a connector bonded to the bump, and the first semiconductor die is between the semiconductor die package and the first substrate.