T-Shaped Bumps for Thin Package Reliability
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Solution Overview
Problem
The reduction in size and pitch of semiconductor chip pads and bumps leads to increased physical stress due to thermal expansion differences, causing reliability issues in electronic device packages as the bumps may peel from the pads, especially in thinner packages.
Innovation Solution
The development of electronic device packages featuring 'T'-shaped bumps with a post and an enlarged portion, surrounded by a locking interconnection portion and encapsulated in a dielectric layer, which increases bonding strength through both physical and chemical means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thicknesses of semiconductor chips, package substrates and mold layers are reduced to achieve thin packages, then the package thickness is reduced, but the physical stress at bump-pad interfaces increases causing bumps to peel from pads
Solution Approach 1:
The bump structure is changed from a simple cylindrical shape to a T-shaped configuration with a laterally protruded enlarged portion. This dimensional change increases the contact area between the bump and pad in the lateral direction, distributing the thermal stress over a larger area and preventing peeling while maintaining thin package thickness.
Solution Approach 2:
The bump is constructed with a composite structure consisting of a post portion made of one metal material and an enlarged portion made of another metal material with different properties. This composite structure allows optimization of each portion for different functions: the post for vertical connection and the enlarged portion for stress distribution and bonding.
2Productivity
If the pitches and sizes of chip pads are reduced to achieve higher integration, then the integration density is improved, but the contact areas between bumps and pads are abruptly reduced increasing physical stress
Solution Approach 1:
By adding the lateral enlarged portion to the bump structure, the contact area is extended in the lateral dimension rather than relying solely on vertical height. This allows adequate contact area even when pad pitches are reduced for higher integration.
Solution Approach 2:
The bump structure is made non-uniform with a localized enlarged portion at the pad interface. This local quality change concentrates the stress-bearing capability exactly where needed at the bump-pad contact area, while the rest of the bump maintains its original function.
3Reliability
If different metal materials are used for bumps and interconnection portions, then chemical bonding is enhanced, but manufacturing complexity increases
Solution Approach 1:
Different metal materials are used for different portions of the bump structure. The post portion uses one metal material optimized for vertical connection, while the enlarged portion uses another metal material optimized for chemical bonding with the pad. This local differentiation of material properties enhances bonding without requiring complete redesign of the entire structure.
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 'T'-shaped bump configuration enhances bonding strength between the bumps and interconnection portions, reducing the likelihood of peeling and improving the reliability of electronic device packages by maximizing contact areas and utilizing different metal materials for enhanced chemical bonding.
Implementation Method 1
utilizing different metal materials for enhanced chemical bonding
Data Source
AI summary
An electronic device package includes a bump having a post disposed on a contact portion of a semiconductor chip and an enlarged portion laterally protruded from an upper portion of the post; an interconnection portion having a locking portion that substantially surrounds the enlarged portion and an upper sidewall of the post; and a dielectric layer substantially surrounding the bump and the locking portion to separate the interconnection portion from the semiconductor chip.