Fine Pitch Traces for Solid State Diffusion Bonding
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Solution Overview
Problem
Current semiconductor packaging technologies face challenges in achieving high-density interconnects with fine pitch interconnection, particularly below 20 μm, due to limitations in traditional semi-additive and subtractive methods, which struggle with maintaining the top and bottom trace ratio and require precise control of temperature and pressure for diffusion bonding, while avoiding damage to semiconductor materials.
Innovation Solution
A semiconductor package is created using a flexible substrate with traces formed from multiple conductive materials (copper, nickel-phosphorus, palladium, and gold) optimized for both diffusion bonding and soldering, employing a thermo-compressive bonding method that allows for reduced bond pitch and improved electrical and thermal performance, enabling bonding of ICs to substrates with gold bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional semi-additive and subtractive methods are used to reduce trace pitch, then manufacturing process is simpler, but trace pitch cannot be reduced below 20 μm and top and bottom trace ratio cannot be maintained as 1
Solution Approach 1:
The patent changes the manufacturing approach from traditional semi-additive/subtractive methods to a novel electroplating process with specific parameters: copper trace width of 10 μm, spacing of 10 μm, and thickness of 15-20 μm, achieving a 1:1 top and bottom trace ratio and reducing pitch below 20 μm while maintaining manufacturability
Solution Approach 2:
The patent uses composite material structure with copper traces plated on flexible substrate, achieving fine pitch interconnection with controlled trace dimensions and ratios that cannot be obtained with traditional single-material methods
2Strength
If bonding temperature and pressure are increased to achieve strong diffusion bonds, then bond strength is improved, but semiconductor materials may be damaged
Solution Approach 1:
The patent optimizes bonding parameters to a specific range: temperature of 200-300°C and pressure of 1-10 atm, which achieves strong diffusion bonds without damaging semiconductor materials, balancing bond strength with material safety
Solution Approach 2:
The patent replaces mechanical bonding with diffusion bonding using atomic diffusion at controlled temperature and pressure, achieving strong bonds without the excessive mechanical force that would damage fine pitch semiconductor structures
3Productivity
If bond pitch is reduced to 10 μm width with 10 μm spacing, then interconnection density is improved, but maintaining uniform pressure and proper surface formation becomes difficult
Solution Approach 1:
The patent ensures each contact interface has proper local properties: copper trace width of 10 μm with 10 μm spacing, thickness of 15-20 μm, and appropriate surface finish, allowing uniform pressure distribution and full contact interface formation even at high density
Solution Approach 2:
The patent adds the thickness dimension (15-20 μm) to the trace structure, providing sufficient top width on the bonding surface to ensure proper surface formation and uniform pressure distribution across the contact interface, enabling fine pitch bonding at 10 μm width and spacing
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 method achieves strong and reliable bonds with a bond pitch reduced to below 16 μm, maintaining a trace aspect ratio greater than 1, and provides superior electrical connections and thermal compression bonding, suitable for advanced packaging applications including flip chip assembly and surface mounting.
Implementation Method 1
a deformable layer so that under pressure the plastic deformation of that layer operates to bring the interface to the bonding temperature more quickly and to enhance diffusion
Implementation Method 2
Diffusion bonding is a method of joining metallic or non-metallic materials. This bonding technique is based on the atomic diffusion of elements at the joining interface
Implementation Method 3
Creep mechanism allows a material flow to produce full intimate contact at the joint interface as required for diffusion bonding
Implementation Method 4
Thermo-compression bonding has a predicted application in flip chip assembly using gold bumps
Data Source
AI summary
A method to produce a semiconductor package or system-on-flex package comprising bonding structures for connecting IC/chips to fine pitch circuitry using a solid state diffusion bonding is disclosed. A plurality of traces is formed on a substrate, each respective trace comprising five different conductive materials having different melting points and plastic deformation properties, which are optimized for both diffusion bonding of chips and soldering of passives components.