Cu Column Hardness and Roughness for Pitch Narrowing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing Cu columns for pitch narrowing mounting and high-density electronic components face issues with low fluidity and adhesion due to high Vickers hardness and arithmetic mean roughness, leading to potential stress and reliability problems during temperature cycling tests.
Innovation Solution
Developing Cu columns with Vickers hardness between 20 HV and 60 HV and arithmetic mean roughness of 0.3 μm or less, optimized through purity levels of 99.9% to 99.995% and alpha dose reduction, with optional coatings such as flux layers and imidazole compounds to enhance adhesion and fluidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Cu ball is used for solder bump, then the solder bump can support semiconductor package weight without melting, but the stand-off height determination makes Cu ball diameter broader and cannot correspond to pitch narrowing mounting
Solution Approach 1:
The patent changes the shape parameter from spherical (Cu ball) to cylindrical (Cu column), which fundamentally alters the relationship between height and diameter. This parameter change allows independent control of stand-off height without proportionally increasing diameter, enabling pitch narrowing mounting while maintaining support capability.
Solution Approach 2:
Instead of using a ball shape where diameter and height are coupled, the patent inverts to a column shape where height can be independently controlled. This inversion of the geometric relationship allows the stand-off height to be determined without making the diameter broader, solving the contradiction between support capability and pitch compatibility.
2Reliability
If different solder materials are used for die-bonding and mounting, then the solder material for die-bonding is protected from melting, but stress (heat stress) is generated at joining part due to coefficient of thermal expansion difference
Solution Approach 1:
The patent uses the same solder material (Sn-3Ag-0.5Cu) for both die-bonding and mounting processes. This homogeneity in material selection eliminates the coefficient of thermal expansion difference between joining materials, thereby preventing heat stress generation while still providing protection from melting through the Cu column's structural support.
Solution Approach 2:
The patent extracts the support function from the solder material and assigns it to the Cu column structure. This allows the solder material to be used uniformly for both processes without needing different materials for protection, as the Cu column bears the mechanical load while the solder provides electrical and thermal connection.
3Strength
If Cu column with high Vickers hardness is used for pitch narrowing mounting, then the column shape provides stable support, but the fluidity and adhesion during mounting deteriorate
Solution Approach 1:
The patent optimizes the Vickers hardness parameter to a specific range (20-60 HV) that balances support stability with mounting performance. This parameter optimization ensures the Cu column is soft enough for good fluidity and adhesion during mounting, yet hard enough to provide stable support, resolving the contradiction between strength and ease of operation.
4Stability of the object's composition
If Cu column with high arithmetic mean roughness is used, then the column provides structural integrity, but the adhesion between Cu column and electrode deteriorates
Solution Approach 1:
The patent optimizes the arithmetic mean roughness parameter to 0.3 μm or less, which balances structural integrity with adhesion performance. This surface finish optimization ensures the Cu column maintains its structural strength while providing sufficient surface area and appropriate texture for strong adhesion to the electrode, resolving the contradiction between stability and ease of operation.
Data Source
AI summary
Provided are a Cu column, a Cu core column, a solder joint, and a through-silicon via, which have the low Vickers hardness and the small arithmetic mean roughness. For the Cu column 1 according to the present invention, its purity is equal to or higher than 99.9% and equal to or lower than 99.995%, its arithmetic mean roughness is equal to or less than 0.3 μm, and its Vickers hardness is equal to or higher than 20 HV and equal to or less than 60 HV. Since the Cu column 1 is not melted at a melting temperature in the soldering and a definite stand-off height (a space between the substrates) can be maintained, it is preferably applied to the three dimensional mounting or the pitch narrowing mounting.