Cu Core Ball Soldering Material Oxidation Control
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Solution Overview
Problem
Conventional Cu core balls used in soldering are prone to oxidation due to residual plating solution residues, leading to wettability defects and mounting failures, even when stored under optimal conditions, as the existing methods for managing oxide film thickness are inadequate.
Innovation Solution
A soldering material with a Cu core coated in a Sn or Sn alloy solder layer, where the material's lightness in the L*a*b* color space is greater than or equal to 62.5 after a heating storage test, indicating reduced plating solution residue and minimized oxidation, and an oxide film thickness of less than 4.9 nm, ensuring reliable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Cu core balls are used with plating treatment, then manufacturing precision and solderability are improved, but plating solution residues remain on the surface causing oxidation and wettability defects
Solution Approach 1:
The patent extracts and removes the harmful plating solution residues from the Cu core ball surface through cleaning treatments before storage. This extraction of contaminants prevents subsequent oxidation while maintaining the beneficial plating layer for solderability.
Solution Approach 2:
The patent applies preliminary cleaning actions immediately after plating to remove residues before they can cause oxidation during storage. This preliminary removal of harmful substances prevents the oxidation problem from developing during long-term storage.
2Productivity
If Cu core balls are stored for long-term, then productivity and inventory management are improved, but oxide film thickness increases causing wettability defects
Solution Approach 1:
The patent performs preliminary cleaning of plating residues immediately after manufacturing, creating a clean surface that resists oxidation during long-term storage. This preliminary action enables long-term inventory management while maintaining wettability.
Solution Approach 2:
The patent changes the surface state parameters by removing organic residues through cleaning, which fundamentally alters the oxidation behavior during storage. This parameter change enables long-term stability while maintaining bonding reliability.
3Object-generated harmful factors
If cleaning is performed to remove plating solution residues, then oxidation is reduced, but productivity decreases due to additional processing steps
Solution Approach 1:
The cleaning operation is performed as a preliminary step immediately after plating while the surface is still accessible and before storage begins. This timing optimization reduces the need for more complex later interventions while enabling long-term stability.
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 oxidation of Cu core balls after long-term storage, ensuring accurate identification and management of oxide film thickness, thereby preventing bonding failures and improving the yield ratio of semiconductor packages.
Implementation Method 1
there is an occasion when an oxide film is formed on a solder surface of the Cu core ball
Implementation Method 2
a heating storage test performed for 72 hours in a temperature-controlled bath at 150° C. set in a room with a temperature of 25° C. and 40% humidity
Data Source
AI summary
The present invention accurately distinguishes a soldering material less likely to oxidize. A Cu core ball has a Cu ball having a predetermined size, and a solder layer coating the Cu ball. The Cu ball provides a space between a semiconductor package and a printed circuit board. The Cu core ball has the soldering material having lightness greater than or equal to 62.5 in L*a*b* color space subsequent to a heating storage test performed for 72 hours in a temperature-controlled bath at 150° C. with a temperature of 25° C. and 40% humidity, and the soldering material, prior to the heating storage test, having lightness greater than or equal to 65 in the L*a*b* color space and yellowness less than or equal to 7.0 in the L*a*b* color space.