Bumpless Flipchip Interconnects Using Aluminum-Wettable Paste
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Solution Overview
Problem
The existing processes for forming flipchip interconnections in semiconductor devices are time-consuming and costly, requiring multiple complex steps that increase the risk of abnormalities and reduce manufacturing efficiency.
Innovation Solution
A method involving the use of aluminum-wettable conductive paste is applied directly to contact pads on a substrate, with a semiconductor die placed on top, and then reflowed to form an interconnect structure, eliminating the need for under bump metallization and bumps, thereby simplifying the process and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional flipchip interconnection processes are used, then reliable electrical connections are achieved, but manufacturing cycle time and cost increase significantly
Solution Approach 1:
The patent merges the interconnection formation process with the die attachment process by applying conductive paste directly to the substrate contact pads before mounting the die. This eliminates the need for separate bump formation and under bump metallization steps, thereby reducing manufacturing cycle time while maintaining reliable electrical connections through the integrated process.
Solution Approach 2:
The conductive paste is applied to the substrate contact pads in advance of die mounting, preparing the interconnection structure beforehand. This preliminary action allows the interconnection and attachment to occur simultaneously during the reflow process, eliminating subsequent processing steps and reducing overall manufacturing time.
2Reliability
If traditional flipchip interconnection processes with multiple steps are used, then robust interconnect structures are formed, but manufacturing complexity and cost increase
Solution Approach 1:
The patent combines multiple traditional steps (bump formation, under bump metallization, and die attachment) into a single integrated process where conductive paste is applied directly to contact pads and the die is mounted in one sequence. This merging reduces manufacturing process complexity from multiple discrete steps to a streamlined unified process while maintaining robust interconnect structures.
Solution Approach 2:
The patent extracts and eliminates unnecessary intermediate steps from the traditional flipchip process, specifically removing the under bump metallization and separate bump formation steps. By taking out these redundant processes, the manufacturing complexity is reduced while the essential function of creating robust electrical connections is preserved through direct paste application.
3Reliability
If conventional interconnection methods are used, then electrical connections are established, but manufacturing cost and time consumption increase
Solution Approach 1:
The patent employs conductive paste as a disposable, low-cost material that is applied directly to the substrate contact pads. This eliminates the need for expensive and time-consuming bump formation processes and under bump metallization layers. The paste serves its interconnection function and is then removed or integrated, providing a cost-effective solution that maintains electrical connection quality while improving manufacturing efficiency.
Solution Approach 2:
The patent changes the physical and chemical parameters of the interconnection approach by using a conductive paste formulation that can be directly applied and reflowed. This parameter change from traditional metallization processes to paste-based direct bonding reduces manufacturing cost and time while achieving reliable electrical connections through controlled reflow processing.
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 reduces manufacturing cycle time and costs by directly forming interconnects on contact pads, enhancing the efficiency and reliability of the interconnection process while minimizing defects.
Implementation Method 1
reflowing the aluminum-wettable conductive paste to form an interconnect structure over the contact pads of the substrate
Data Source
AI summary
A semiconductor device includes a substrate with contact pads. A mask is disposed over the substrate. Aluminum-wettable conductive paste is printed over the contact pads of the substrate. A semiconductor die is disposed over the aluminum-wettable conductive paste. The aluminum-wettable conductive paste is reflowed to form an interconnect structure over the contact pads of the substrate. The contact pads include aluminum. Contact pads of the semiconductor die are disposed over the aluminum-wettable conductive paste. The aluminum-wettable conductive paste is reflowed to form an interconnect structure between the contact pads of the semiconductor die and the contact pads of the substrate. The interconnect structure is formed directly on the contact pads of the substrate and semiconductor die. The contact pads of the semiconductor die are etched prior to reflowing the aluminum-wettable conductive paste. An epoxy pre-dot to maintain a separation between the semiconductor die and substrate.