Conductive Ball With Patterned Nickel And Tin-Based Solder
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electronic devices with conductive balls formed by covering solder on copper balls experience thermal instability and electromigration issues due to the formation of brittle Ni3Sn4 layers, leading to cracks and voids when heat is applied, which compromises connection reliability.
Innovation Solution
A conductive ball with a copper core, a patterned nickel layer, and a tin-based solder is used, where the copper is diffused into the solder to form a thermally stable (Cu, Ni)6Sn5 layer, preventing crystal growth and electromigration-induced voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ni layer and Sn/Ag solder are sequentially covered on a Cu ball to form a conductive ball, then the conductive ball can connect connection pads, but a brittle Ni3Sn4 layer forms during reflow heating causing cracks and voids
Solution Approach 1:
The patent changes the chemical composition parameters of the solder from Sn/Ag to a specific tin-based solder containing 95-99.9 wt% Sn and 0.1-5 wt% Cu. This compositional parameter change prevents the formation of brittle Ni3Sn4 and promotes formation of the more stable (Cu, Ni)6Sn5 intermetallic compound during reflow heating, thereby improving thermal stability while maintaining connection reliability
Solution Approach 2:
The patent creates a composite intermetallic compound layer (Cu, Ni)6Sn5 by combining Cu from the core ball, Ni from the intermediate layer, and Sn from the solder. This composite material approach results in a thermally stable intermetallic compound that resistors crack formation and void generation, resolving the contradiction between connection reliability and thermal stability
2Reliability
If reflow heating is applied to connect the conductive ball to connection pads, then electrical connection is achieved, but electromigration causes Ni movement and void formation
Solution Approach 1:
The patent converts the potential harm of Ni migration during electromigration into a beneficial outcome. By including Cu in the solder, the patent ensures that when Ni tends to migrate under electromigration stress, the presence of Cu atoms in the intermetallic compound structure stabilizes the lattice and reduces void formation. The (Cu, Ni)6Sn5 intermetallic compound formed is more resistant to electromigration-induced damage than pure Ni3Sn4, thus converting the harmful electromigration effect into a more stable connection
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 (Cu, Ni)6Sn5 layer provides high reliability and stability, preventing cracks and voids, thus enhancing the connection between electronic members even under thermal stress.
Implementation Method 1
copper in the copper ball is diffused from opening regions of the nickel layer to the tin-based solder. Thereby, the (Cu, Ni)6Sn5 layer, which is an intermetallic compound, is formed between the nickel layer and the tin-based solder of the conductive ball
Data Source
AI summary
A conductive ball includes a copper ball, a nickel layer formed with being patterned on an outer surface of the copper ball, and a tin-based solder covering each outer surface of the copper ball and the nickel layer.