Ni Ball Hardness Control for Solder Joint Impact Resistance
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Solution Overview
Problem
The existing methods for manufacturing Ni balls result in high Vickers hardness, leading to low durability and impact resistance, while increasing purity to achieve softness compromises sphericity, affecting self-alignment and joint quality in semiconductor packaging.
Innovation Solution
The Ni balls are optimized by controlling Vickers hardness between 20HV and 90HV through expedited crystal growth, with annealing treatment or slow-cooling processes, and maintaining high purity and sphericity, along with controlled impurity levels and coatings, to enhance impact resistance and self-alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rapid-cooling method is used to manufacture Ni ball, then crystal grain is formed instantly and Vickers hardness becomes high, but durability against external stress becomes low and impact resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by controlling the cooling rate from rapid-cooling to controlled slow-cooling, and by adjusting impurity content parameters. Specifically, the cooling rate is reduced to allow crystal grain growth, and impurity content is optimized to balance hardness and ductility, transforming the material properties to achieve both adequate hardness and improved impact resistance.
Solution Approach 2:
The patent creates a composite structure within the Ni ball by intentionally incorporating controlled amounts of impurity elements that act as crystal grain growth promoters. This internal composite approach, where impurities serve functional roles in facilitating crystal growth during slow-cooling, results in a microstructure that combines hardness with enhanced ductility and impact resistance.
2Strength
If purity of Ni ball is increased to enable crystal grain growth and lower Vickers hardness, then softness improves, but sphericity becomes lower
Solution Approach 1:
The patent applies parameter changes by optimizing the purity level rather than maximizing it, and by controlling the cooling rate parameter. The purity is maintained at a high level (99.99% or more) to ensure adequate softness, while the cooling rate is slowed down to compensate for the reduced crystal growth promotion from impurities, thereby maintaining both sphericity and desired hardness properties.
3Strength
If sphericity of Ni ball is low, then self-aligning property cannot be ensured during mounting, but increasing purity to improve softness causes sphericity to decrease
Solution Approach 1:
The patent applies parameter changes by optimizing the cooling rate parameter to compensate for high purity levels. By using slow-cooling with high purity Ni (99.99% or more), the crystal grains grow adequately despite the lack of impurity-driven nucleation sites, resulting in spherical shapes that ensure proper self-alignment during mounting while maintaining the desired softness and hardness balance.
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 improves impact resistance and maintains appropriate spacing between substrates, ensuring reliable self-alignment and preventing poor joints during semiconductor chip mounting.
Implementation Method 1
liquid molten Ni is sprayed from a nozzle at high speed, and then misty molten Ni is rapidly cooled to a room temperature (25 degrees C, for example)
Implementation Method 2
a crystal grain of Ni is formed instantly, so that the Ni ball is formed by a fine crystal grain
Implementation Method 3
a case of utilizing 'an annealing treatment' will be described as means for expediting the crystal growth of each of the Ni balls
Implementation Method 4
expediting crystal growth in each of the Ni balls
Data Source
Figure 1
Figure 2
AI summary
Provided are a Ni ball, a Ni core ball, a solder joint, solder paste and foamed solder which are superior in the impact resistance to dropping and can inhibit any occurrence of a poor joints. An electronic component 60 is constructed by joining a solder bump 30 of a semiconductor chip 10 to an electrode 41 of a printed circuit board 40 with solder paste 12, 42. The solder bump 30 is formed by joining an electrode 11 of the semiconductor chip 10 to the solder ball 20. The 20 according to the present invention contains purity which is equal to or higher than 99.9% and equal to or lower than 99.995%, sphericity which is equal to or higher than 0.90, and Vickers hardness which is equal to or higher than 20 and equal to or less than 90HV.