Solder Ball Bridge Metallization for Low-Stress Wafer Interconnects
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Solution Overview
Problem
Current methods for forming electrical interconnections between mounted devices and substrates in photonic integrated circuits face challenges such as excessive stress leading to device fracturing, high inductance, high resistance, and limitations in wafer level processing.
Innovation Solution
The use of solder ball bridges formed between bond pads on mounted devices and substrates, which are deposited using solder ball jetting apparatuses, providing low inductance and low resistance electrical connections while enabling thermal coupling and suitable for wafer level processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is used to form electrical interconnections, then electrical connections can be formed between mounted devices and substrates, but excessive stress is introduced leading to device fracturing and loss of contact integrity
Solution Approach 1:
The patent replaces the mechanical wire bonding process with a solder ball jetting process that deposits molten solder balls onto bond pads. This substitution eliminates the mechanical stress and fracturing associated with wire bonding while achieving reliable electrical connections through controlled solder deposition and reflow
Solution Approach 2:
The patent changes the physical state of the interconnection material from solid wire (wire bonding) to molten solder balls that are deposited and then reflowed. This parameter change allows for stress-free connection formation while maintaining electrical conductivity and mechanical reliability
2Reliability
If thin wire diameters are used in wire bonding, then connections can be formed, but the connections have high inductance and high resistance
Solution Approach 1:
The patent changes the geometry and material state of the interconnection from thin solid wire to larger-volume molten solder balls that spread into low-inductance, low-resistance connections. The solder balls are deposited with controlled size and then reflowed to form optimized connection geometries that minimize electrical losses
Solution Approach 2:
The patent utilizes spherical solder balls as the interconnection medium. The spherical geometry provides optimal surface area to volume ratio for bonding while the molten state allows the spheres to spread and form low-inductance pathways that reduce electrical resistance compared to thin wire configurations
3Reliability
If conventional interconnection methods are used, then electrical connections can be formed, but thermal coupling between mounted devices and substrates is insufficient
Solution Approach 1:
The patent creates interconnections that simultaneously provide both electrical conductivity and thermal coupling functions. The solder ball interconnections serve dual purposes: establishing electrical pathways between bond pads while also providing thermally conductive pathways for heat dissipation from mounted devices to the substrate
Solution Approach 2:
The patent employs solder material that combines both excellent electrical conductivity and thermal conductivity properties. The solder balls form composite interconnection structures that integrate electrical and thermal transport functions, improving overall heat management while maintaining electrical connectivity
4Reliability
If wire bonding techniques are used, then electrical interconnections can be formed, but the process is not suitable for wafer level processing
Solution Approach 1:
The patent replaces the manual or semi-automated wire bonding process with an automated solder ball jetting system that can process entire wafers simultaneously. This substitution enables wafer-level integration by depositing solder balls precisely onto multiple bond pads across the wafer surface in a single processing step
Solution Approach 2:
The patent employs a reflow heating process that accelerates the bonding of solder balls to bond pads through controlled thermal processing. This accelerated bonding process enables rapid, high-volume wafer-level manufacturing while ensuring reliable electrical connections are formed across all interconnection points
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 enhances electrical and thermal conductivity between mounted devices and substrates, reduces the risk of device damage, and facilitates more practical and widespread adoption of photonic and non-photonic device integration.
Implementation Method 1
deposited using solder ball jetting apparatuses
Implementation Method 2
providing low inductance and low resistance electrical connections while enabling thermal coupling
Implementation Method 3
providing low inductance and low resistance electrical connections
Implementation Method 4
enabling thermal coupling
Data Source
AI summary
Wafer level solder ball bridge formation is used to provide electrical and thermal coupling between bond pads formed on substrates and bond pads formed on devices mounted on substrates. Solder balls anchored to solder-wettable bond pads enable sequential linking of laterally coupled solder balls over non-solder-wettable surface in the formation of solder ball bridge assemblies. Solder ball bridges formed between a device disposed on a substrate and a substrate enables thermal energy transfer and electrical interconnection between the device and the substrate.