Eutectic Solder Structure for Chip Bonding
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Solution Overview
Problem
Conventional eutectic solder structures face challenges in achieving good bonding interface properties due to the fluidity of metal layers with low melting points, leading to voids and structural collapse during high-temperature processing, which affects the reliability of chip bonding.
Innovation Solution
A eutectic solder structure is designed with alternate lamination of first and second metal layers, where the second metal layers have a higher melting point and include continuous regions and openings, allowing the first metal layers to flow towards the substrate through these openings, reducing the likelihood of external flow and enhancing bonding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If continuous metal layers with low melting points are used in the solder structure, then bonding temperature can be reduced, but the metal layers may flow outward and cause voids or structural collapse
Solution Approach 1:
The solder structure is divided into multiple discrete metal layers (first metal layers and second metal layers) with different melting points arranged in alternating sequence. This segmentation allows the low-melting-point first metal layers to provide low-temperature bonding capability while the high-melting-point second metal layers prevent outward flow and maintain structural integrity.
Solution Approach 2:
The solder structure employs a composite multi-layer configuration combining metals with different melting points (e.g., Sn/Pb eutectic alloy with Cu or Ni layers). This composite structure enables the system to simultaneously achieve low bonding temperature (through the eutectic reaction of the first metal layer) and prevent metal flow (through the high-melting-point second metal layer acting as a barrier).
2Reliability
If heat treatment is performed to form intermetallic compounds, then stable bonding is achieved, but metal flow and void formation increase at high temperatures
Solution Approach 1:
The invention changes the temperature parameter profile by using a multi-layer structure with different melting points. The heat treatment process is optimized to occur at a temperature range where the first metal layer undergoes eutectic reaction and intermetallic compound formation, while the second metal layer remains solid and acts as a constraint, thereby achieving stable bonding without excessive metal flow.
3Ease of manufacture
If the process temperature approaches the melting point of the low melting point metal layer, then eutectic bonding is facilitated, but fluidity increases causing structural collapse
Solution Approach 1:
The second metal layer with higher melting point acts as an intermediary barrier between the low-melting-point first metal layer and the external environment. During heat treatment, this intermediary layer remains solid and prevents the molten first metal layer from flowing outward, thereby maintaining solder structure integrity while still allowing eutectic bonding to occur.
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 enables bonding at relatively low temperatures, preventing voids and structural collapse, while ensuring excellent bonding interface properties and improved heat dissipation, thus enhancing the reliability of chip bonding.
Implementation Method 1
The chip is bonded to the substrate by an eutectic reaction of the solder structure
Data Source
AI summary
The present invention provides a eutectic solder structure for a chip including a substrate and a solder structure on the substrate. The solder structure includes an alternate lamination of a plurality of first metal layers and a plurality of second metal layers, wherein each second metal layer has a continuous region and a plurality of openings and the melting point of the plurality of second metal layers is higher than that of the plurality of first metal layers. The eutectic solder structure for a chip also includes a chip on the solder structure, wherein the chip is bonded to the substrate by a eutectic reaction of the solder structure.