Compliant Conductive Interconnect for Flip-Chip Package
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Solution Overview
Problem
Conventional semiconductor devices face reliability issues due to de-wetting of Under Bump Metallization (UBM) layers and weak joints, leading to delamination and cracking, which reduces manufacturing yield and increases costs.
Innovation Solution
A compliant conductive interconnect structure is formed by creating a conductive shell with a hollow core over a semiconductor die, filled with a compliant material, and mounted over a substrate, providing structural support and flexibility to reduce stress-related defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bump interconnect structures are used to connect semiconductor die to substrate, then electrical connection is achieved, but de-wetting of UBM layer and weak joints occur leading to delamination and cracking
Solution Approach 1:
The invention uses a composite interconnect structure consisting of a rigid conductive shell (providing structural support and electrical conductivity) filled with a compliant material (absorbing stress and preventing de-wetting). This composite design combines the advantages of both rigid and compliant materials to eliminate de-wetting issues and prevent cracking while maintaining reliable electrical connection.
Solution Approach 2:
The invention changes the mechanical parameters of the interconnect structure by introducing a compliant material with different elasticity and hardness properties compared to conventional rigid bump materials. This parameter change allows the interconnect to accommodate thermal expansion mismatches and reduce stress concentration, preventing de-wetting and cracking.
2Strength
If rigid conductive structures are used for interconnection, then structural support is provided, but stress concentration occurs causing pre-solder cracking and delamination
Solution Approach 1:
The invention employs a flexible compliant material within the conductive shell that can deform under stress. This flexible component absorbs thermal expansion stresses and prevents stress concentration that would otherwise cause pre-solder cracking and delamination, while the outer conductive shell maintains structural integrity.
3Reliability
If compliant material is used throughout the interconnect structure, then stress absorption is improved, but electrical conductivity and structural support are reduced
Solution Approach 1:
The invention segments the interconnect structure into distinct functional zones: an outer conductive shell providing electrical conductivity and structural support, and an inner compliant material providing stress absorption. This segmentation allows each material to perform its optimal function without compromising the other.
Solution Approach 2:
The compliant material is nested within the conductive shell, creating a nested structure where the inner compliant core provides stress absorption while the outer conductive shell provides electrical conductivity and structural support. This nested design efficiently combines the benefits of both material types.
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 compliant interconnect structure enhances joint reliability, reduces pre-solder cracking and Extremely-Low Dielectric Constant (ELK) delamination, and improves manufacturing yield by allowing the interconnects to conform to stress, thereby increasing the durability and efficiency of semiconductor devices.
Implementation Method 1
depositing a compliant material in the hollow core
Implementation Method 2
forming a conductive shell having a hollow core over the first conductive layer
Data Source
AI summary
A semiconductor device has a semiconductor die. The semiconductor die has a contact pad. A first conductive layer is formed over the contact pad. A conductive shell having a hollow core is formed over the first conductive layer. A compliant material is deposited in the hollow core. The semiconductor die is mounted over a substrate with the conductive shell electrically connected to a conductive trace on the substrate. A second conductive layer is formed over the conductive shell. The compliant material is an insulating material. A bump material is deposited around the conductive shell. A pre-solder material is deposited over the conductive trace. The conductive shell has a cross-sectional width less than 7 micrometers. The second conductive layer is a conductive lip. Mounting the semiconductor die over the substrate further includes mounting the semiconductor die over the substrate in a bump on lead (BOL) configuration.