Mobile Binding in Electronic Connections via Barrier Material
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Solution Overview
Problem
Solder balls used in flip-chip die attachment undergo phase segregation due to tin ion migration, leading to reduced reliability and current carrying capacity, and existing solutions either fail to address this issue or are cost-prohibitive.
Innovation Solution
A method involving a barrier material with a volume of at least 20% of the total volume of the bonding metal, which attracts and traps mobile atoms, preventing phase segregation, using materials like nickel, chromium, or platinum to maintain connections without significant degradation after 1000 hours at 200°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder ball is used for electrical connection, then cost is reduced and electrical conductivity is improved, but phase segregation occurs leading to reduced reliability and current carrying capacity
Solution Approach 1:
A barrier material layer is introduced between the solder ball and the contact pad as an intermediary element. This barrier material prevents direct interaction between the mobile tin ions and the contact pad, thereby stopping phase segregation while maintaining electrical connectivity and structural integrity throughout the connection
2Quantity of substance
If solder ball is used for electrical connection, then manufacturing cost is reduced, but phase segregation reduces current carrying capacity
Solution Approach 1:
The barrier material acts as a mediating layer that prevents the formation of voids and maintains uniform material distribution. By blocking the migration path of mobile ions, the barrier material preserves the solder ball's original composition and ensures sustained current carrying capacity without degradation
3Reliability
If gold is used instead of solder ball, then phase segregation is avoided, but manufacturing cost significantly increases
Solution Approach 1:
The electrical connection structure is designed as a composite system combining solder ball material with a barrier material layer. This composite structure leverages the low cost and good electrical conductivity of solder while incorporating the phase segregation resistance of the barrier material, achieving both cost-effectiveness and reliability
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
Substantially reduces or eliminates phase segregation, maintaining connection reliability and current carrying capacity over time, while being cost-effective by using a barrier material to trap mobile atoms and prevent clumping.
Implementation Method 1
these tin ions will migrate within the solder... diffusion of atoms can leave voids
Data Source
AI summary
A method of creating an electrical contact involves locating a barrier material at a location for an electrical connection, providing an electrically conductive bonding metal on the barrier material, the electrically conductive bonding metal having a diffusive mobile component, the volume of barrier material and volume of diffusive mobile component being selected such that the barrier material volume is at least 20% of the volume of the combination of the barrier material volume and diffusive mobile component volume. An electrical connection has an electrically conductive bonding metal between two contacts, a barrier material to at least one side of the electrically conductive bonding metal, and an alloy, located at an interface between the barrier material and the electrically conductive bonding metal. The alloy includes at least some of the barrier material, at least some of the bonding metal, and a mobile material.