Interposer Package Corner Dams to Prevent Underfill Delamination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor packages face issues with cracking or delamination of the underfill at the corners of the package structure due to mismatched coefficients of thermal expansion, which affects the long-term reliability of the package.
Innovation Solution
Incorporating dam structures with a thermal expansion coefficient that closely matches the package structure, positioned adjacent to the corners, to minimize the thickness of the underfill layers and prevent cracking or delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the underfill is applied without dam structures, then the package structure is simpler and easier to manufacture, but the underfill cracks or delaminates at the corners due to thermal expansion mismatch
Solution Approach 1:
The package structure is segmented by introducing dam structures that divide the underfill region into distinct zones. These dam structures create a segmented configuration where the underfill is contained between the dam structures and the package component, preventing uncontrolled thermal stress propagation and corner delamination.
Solution Approach 2:
The dam structures serve as intermediary elements between the package component and the substrate. These intermediate structures absorb and distribute thermal expansion stresses, acting as a buffer that prevents direct stress transmission to the underfill corners, thereby preventing cracking and delamination.
2Duration of action of stationary object
If dam structures are added to prevent underfill cracking, then the long-term reliability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The dam structures are formed in advance before the underfill is applied. This preliminary action allows the dam structures to be properly positioned and integrated into the package architecture before the underfill is dispensed and cured, ensuring optimal stress distribution from the beginning of thermal cycling.
Solution Approach 2:
The dam structures are strategically placed at specific locations (corners and edges) where thermal stress concentration occurs. This localized approach applies the complexity only where needed to prevent failure, rather than requiring complex modifications throughout the entire package structure.
3Reliability
If the underfill layer thickness is reduced near the package corners, then the thermal expansion stress is minimized, but the underfill may become insufficient for proper bonding
Solution Approach 1:
The underfill layer thickness is varied locally across the package structure. Near the corners and edges, the underfill thickness is reduced to minimize thermal stress concentration, while in the central regions, the underfill maintains sufficient thickness for proper bonding and stress distribution. The dam structures define these local thickness variations.
Solution Approach 2:
The underfill region is segmented into different thickness zones by the dam structures. This segmentation allows the underfill to have optimal thickness in different locations - thinner near corners for stress reduction and thicker in central areas for bonding strength - thereby simultaneously achieving both corner stress resistance and adequate bonding.
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 dam structures effectively reduce or prevent underfill cracking and delamination, enhancing the long-term reliability of the semiconductor package by aligning thermal expansion properties.
Implementation Method 1
the coefficient of thermal expansion of the package structure matches more closely to that of the dam structures than to that of the underfill
Data Source
AI summary
A semiconductor package including one or more dam structures and the method of forming are provided. A semiconductor package may include an interposer, a semiconductor die bonded to a first side of the interposer, an encapsulant on the first side of the interposer encircling the semiconductor die, a substrate bonded to the a second side of the interposer, an underfill between the interposer and the substrate, and one or more of dam structures on the substrate. The one or more dam structures may be disposed adjacent respective corners of the interposer and may be in direct contact with the underfill. The coefficient of thermal expansion of the one or more of dam structures may be smaller than the coefficient of thermal expansion of the underfill.