Flip-Chip Interconnects With Oxidized Metallic Posts
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Solution Overview
Problem
There is a need to enhance the connection density, stability, thermal performance, and integrity of flip-chip assemblies to accommodate increasing connection points and decreasing die size, while maintaining reliability and flexibility in semiconductor manufacturing.
Innovation Solution
The method involves forming metallic posts on the flip-chip die with a wettable tip layer and oxidizing the sides to reduce wettability, and placing solder bumps on the substrate for reflow bonding, allowing for improved interconnect density and thermal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the die size is decreased to accommodate higher connection density, then the number of connection points increases, but the mechanical stability and thermal performance deteriorate
Solution Approach 1:
The patent changes the physical and chemical parameters of the interconnect structure by using metallic posts with controlled oxidation states. The posts have oxidized sides (reducing wettability) and wettable tips (enhancing bonding), creating a controlled interface that maintains mechanical stability while enabling high connection density on smaller dies.
Solution Approach 2:
The interconnect structure uses composite material composition with metallic posts that have differentiated surface properties. The posts combine oxidized regions (for mechanical stability and controlled wettability) with wettable tip layers (for reliable bonding), creating a composite structure that simultaneously achieves high connection density and mechanical reliability.
2Quantity of substance
If the die size is decreased to accommodate higher connection density, then the number of connection points increases, but the thermal performance deteriorates
Solution Approach 1:
The metallic posts with controlled oxidation provide enhanced thermal conductivity pathways. The oxidized sides maintain structural integrity while the wettable tips ensure reliable thermal and electrical contact, enabling efficient heat dissipation even as die size decreases and connection density increases.
3Ease of manufacture
If conventional wire bonding methods are used, then the assembly process is simpler, but the footprint size increases and inductance increases
Solution Approach 1:
The patent inverts the conventional approach by using direct vertical connections through metallic posts instead of lateral wire bonds. This inversion eliminates the need for wire bonding processes while achieving smaller footprint, as connections are made directly through the die thickness rather than looping across the surface.
4Reliability
If the tip layer is applied to prevent oxidation, then the wettability enhances for better bonding, but the oxidation resistance of the entire post is reduced
Solution Approach 1:
The patent applies local quality differentiation by treating only the tip region of the metallic post with a wettable layer, while the sides remain oxidized. This localized treatment provides enhanced bonding at the critical interface (tip) while maintaining oxidation resistance and structural integrity throughout the bulk of the post 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
This approach increases interconnect density, enhances thermal performance, and improves mechanical reliability by creating a stable and efficient electrical connection between the flip-chip die and substrate, accommodating smaller die sizes and higher connection points.
Implementation Method 1
The tip layer of flash gold, tin, or other wettable electroplated material, is applied to the tips of the metallic posts to prevent oxidation and enhance wettability.
Implementation Method 2
The tip layer of flash gold, tin, or other wettable electroplated material, is applied to the tips of the metallic posts to prevent oxidation and enhance wettability.
Implementation Method 3
The sides of the metallic posts are allowed to oxidize to reduce wettability.
Implementation Method 4
the substrate and the flip-chip are heated to cause the solder bumps to reflow and bond to the tip layers of the metallic posts
Data Source
AI summary
The present invention provides a unique way of connecting a flip-chip die to a substrate. Initially, metallic posts are formed on the flip-chip die and solder bumps are placed on the substrate where the metallic post will ultimately connect to the substrate. The tip layer of flash gold, tin, or other wettable electroplated material is applied to the tips of the metallic posts to prevent oxidation and enhance wettability. The sides of the metallic posts are allowed to oxidize to reduce wettability. To attach the flip-chip die to the substrate, the flip-chip die is initially positioned over the substrate, such that the metallic posts align with and come into contact with the solder bumps. Once the flip-chip die is in place over the substrate, the substrate and the flip-chip are heated to cause the solder bumps to reflow and bond to the tip layers of the metallic posts.