Copper Ball Alpha Dose Reduction via Purity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Cu ball manufacturing processes do not adequately reduce alpha radiation, leading to software errors in high-density semiconductor mounting structures, and result in Cu balls with low sphericity that affect mounting performance.
Innovation Solution
Cu balls with a purity of 99.995% or less, containing impurities like Pb and Bi at 50 ppm or more, are manufactured using a specific heating process to limit alpha dose to 0.0200 cph/cm² or less, ensuring high sphericity and preventing software errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high purity Cu material is used to reduce alpha radiation, then alpha dose is decreased, but manufacturing cost increases
Solution Approach 1:
The invention changes the purity parameter of Cu material from conventional high purity (99.99% or higher) to a specific range (99.97% to 99.99%), and adjusts impurity composition parameters (Pb: 0.003-0.01%, Bi: 0.003-0.01%, U: 0.005 ppb or less, Th: 0.005 ppb or less) to simultaneously achieve low alpha dose and cost-effectiveness
Solution Approach 2:
The invention selectively controls specific impurity elements (Pb, Bi, U, Th) while allowing other impurities to remain within acceptable ranges, optimizing the balance between alpha radiation reduction and manufacturing cost by targeting only the most critical elements
2Object-affected harmful factors
If high purity Cu material is used, then alpha dose is decreased, but sphericity of Cu ball deteriorates
Solution Approach 1:
The invention optimizes the purity parameter to a specific range (99.97%-99.99%) rather than maximizing it, and controls specific impurity levels to achieve the optimal balance between alpha dose reduction and maintaining high sphericity (98% or more)
Solution Approach 2:
The invention accepts certain levels of non-critical impurities that are inexpensive to tolerate, focusing purification efforts only on elements that significantly impact both alpha radiation and sphericity
3Ease of manufacture
If conventional Cu ball manufacturing process is used, then production cost is reduced, but alpha radiation increases causing software errors
Solution Approach 1:
The invention modifies the manufacturing process parameters including purity control (99.97%-99.99%), specific impurity limits (Pb: 0.003-0.01%, Bi: 0.003-0.01%, U: 0.005 ppb or less, Th: 0.005 ppb or less), and heating temperature (100-300°C for 1-48 hours) to reduce alpha radiation while maintaining cost-effectiveness
Solution Approach 2:
The invention performs preliminary purification and impurity control during the Cu ball manufacturing process itself, rather than requiring post-manufacturing treatment, thereby reducing alpha radiation levels before the balls are used in semiconductor assemblies
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 solution effectively reduces alpha radiation-induced software errors and enhances sphericity, maintaining the structural integrity and performance of Cu balls in high-density mounting applications.
Implementation Method 1
α ray radiates by α decay of a radioactive isotope such as U, Th and 210
Implementation Method 2
a Cu ball manufacturing process comprises: melting Cu material
Data Source
Figure 1~2
Figure 3
AI summary
To provide Cu ball that has less α dose and high sphericity even when containing at least a certain amount of impurity elements other than Cu. Even when the purity thereof is 99.995% or less and U and Th contents are 5 ppb or less in order to suppress any software errors and decrease connection failure, α dose is 0.0200 cph/cm2 or less. Further, the sphericity of the Cu ball is unexpectedly improved by making the purity not more than 99.995%.