Ni-Sn Intermetallic Solder Layer for High-Temperature PCB Mounting
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Solution Overview
Problem
Current solder materials for power applications and second-level mounting on printed circuit boards face challenges such as re-melting, fatigue, and non-Pb-free compositions, especially with the impending EU-wide ban on lead.
Innovation Solution
A solder material comprising nickel and tin with a bimodal distribution of nickel particles, where the first amount of particles ranges from 5 at % to 60 at % and the second amount of particles ranges from 10 at % to 95 at %, allowing for a high melting temperature and formation of high-temperature intermetallic phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If eutectic PbSn solder or SAC solder is used for second level mounting, then the soldering process can be completed at lower temperatures (180°C or 220°C), but the board level interconnects may re-melt during application and are prone to fatigue at elevated temperatures
Solution Approach 1:
The patent changes the compositional parameters of the solder material by incorporating intermetallic phases with specific melting points above 270°C, thereby raising the operational temperature threshold and preventing re-melting during application while maintaining soldering feasibility
Solution Approach 2:
The patent creates a composite solder material system combining multiple intermetallic phases (such as Ni3Sn4, Ni3Sn2, or CoSn5) with controlled particle size distributions, achieving both high-temperature stability and reliable mechanical properties that single-phase materials cannot provide
2Reliability
If high lead content solder is used, then good soldering performance is achieved, but the solder is not Pb-free and violates RoHS regulations
Solution Approach 1:
The patent extracts and eliminates lead from the solder composition entirely, replacing it with intermetallic phases based on nickel, cobalt, and tin that provide equivalent or superior soldering performance while complying with RoHS regulations
Solution Approach 2:
The patent fundamentally changes the chemical composition parameters of the solder material, transitioning from lead-based alloys to intermetallic phase compositions with controlled stoichiometry, achieving both Pb-free status and reliable soldering performance
3Object-generated harmful factors
If AuSn is used as a replacement for Pb-soldering, then Pb-free soldering is achieved, but costs significantly increase and design rules become more restrictive
Solution Approach 1:
The patent employs cost-effective intermetallic phases based on abundant materials like nickel and tin instead of expensive gold-based systems, achieving Pb-free soldering without the high material costs and stringent design rules associated with AuSn
Solution Approach 2:
The patent modifies the compositional parameters to use economically viable intermetallic systems (Ni-Sn, Co-Sn) with relaxed geometric design rules compared to AuSn, maintaining Pb-free compliance while reducing both cost and design complexity
4Adaptability or versatility
If adhesive with high silver content filling is used, then alternative to solder is provided, but thermal and electrical performance deteriorates compared to high lead content solder
Solution Approach 1:
The patent creates a composite material system where intermetallic phases are integrated within a solder matrix, achieving both mechanical bonding and superior thermal/electrical conductivity that homogeneous adhesive materials cannot provide
Solution Approach 2:
The patent fundamentally changes the material class from organic adhesive to inorganic intermetallic-based solder, achieving both alternative functionality to traditional solder and superior thermal/electrical performance through controlled composition and phase 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
The solder material achieves a melting temperature above 270°C, providing reliability and stability for second-level soldering, while being Pb-free and cost-effective, thus addressing the limitations of existing solutions.
Implementation Method 1
The solder material may have a melting temperature above 270° C.
Implementation Method 2
heating the layer structure to a melting temperature of the solder material until an intermetallic phase forms
Data Source
AI summary
A layer structure includes a first layer including at least one material selected from a first group consisting of nickel, copper, gold, silver, palladium, tin, zinc, platinum, and an alloy of any of these materials; a third layer including at least one material selected from a second group consisting of nickel, copper, gold, palladium, tin, silver, zinc, platinum, and an alloy of any of these materials; and a second layer between the first layer and the third layer. The second layer consists of or essentially consists of nickel and tin. The second layer includes an intermetallic phase of nickel and tin. Methods of forming the layer structure, a chip package and a chip arrangement are also described.