Cu Core Ball Solder Material Oxide Film Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The management of oxide film thickness on Cu core balls is inaccurate using yellowness alone, leading to potential mounting failures due to oxidation resistance issues during reflow treatment and storage, which affects the productivity and yield of semiconductor packages.
Innovation Solution
A solder material with a core and a covering layer composed of Sn or a Sn-based alloy, where the lightness is equal to or more than 65 and yellowness is equal to or less than 7.0 in the L*a*b* color space, and the oxide film thickness is maintained at 3.8 nm or less, with Ge added to the covering layer for enhanced oxidation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If yellowness alone is used to manage oxide film thickness, then measurement simplicity is maintained, but measurement precision deteriorates leading to inaccurate oxide film thickness control
Solution Approach 1:
The patent transitions from using a single color parameter (yellowness b*) to a two-dimensional color space evaluation system (lightness L* and yellowness b*). This dimensional expansion enables more precise oxide film thickness measurement by capturing both the brightness and color tone changes that occur during oxidation, thereby resolving the contradiction between measurement precision and system complexity.
2Reliability
If Ge is added to the covering layer to improve oxidation resistance, then reliability during reflow treatment is improved, but manufacturing precision of alloy composition becomes more critical
Solution Approach 1:
The patent specifies precise Ge content parameters (0.003-0.03 mass%) within the Sn-based alloy covering layer to achieve optimal oxidation resistance. By defining specific compositional parameters and their ranges, the patent balances the need for improved reliability through Ge addition while maintaining manufacturability through clear specification limits.
3Reliability
If oxide film thickness is not controlled, then storage and handling are simplified, but mounting reliability deteriorates due to wettability defects
Solution Approach 1:
The patent implements preliminary control of oxide film thickness (maintaining at 3.8 nm or less) through specified lightness (L* ≥ 65) and yellowness (b* ≤ 7.0) parameters before the reflow treatment. This preliminary action ensures that the solder material is in optimal condition for mounting, preventing wettability defects and ensuring reliable connections before the actual joining process occurs.
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 allows for precise management of oxide film thickness and improved oxidation resistance during and after melting, preventing solder bump crushing and ensuring reliable semiconductor package mounting.
Implementation Method 1
there is an occasion when an oxide film is formed on a solder surface of the Cu core ball due to heating at the time of the reflow treatment. By this influence of the oxide film, wettability defects and the like occur between the solder and an electrode pad
Implementation Method 2
The solder bump is formed by joining a solder ball to an electrode of the semiconductor chip. The solder bump is formed by joining a solder ball to an electrode of the semiconductor chip. The semiconductor package to which the BGA is applied is mounted on a printed circuit board by joining the solder bump melted by heating
Data Source
AI summary
Provided is a solder material having oxidation resistance at the time of melting solder or after melting it, as well as managing a thickness of oxide film at a fixed value or less before melting the solder. A Cu core ball 1A is provided with a Cu ball 2A for keeping a space between a semiconductor package and a printed circuit board and a solder layer 3A that covers the Cu ball 2A. The solder layer 3A is composed of Sn or a solder alloy whose main component is Sn. For the Cu core ball 1A, lightness is equal to or more than 65 in the L*a*b* color space and yellowness is equal to or less than 7.0 in the L*a*b* color space, and more preferably, the lightness is equal to or more than 70 and the yellowness thereof is equal to or less than 5.1.