Electro-deposited Copper Foil Strength and Heat Stability
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Solution Overview
Problem
Existing electro-deposited copper foils for printed wiring boards lack sufficient mechanical strength, particularly for fine-pitch wiring applications, and exhibit significant tensile strength loss when heated, making them unsuitable for high-performance substrates like TAB substrates.
Innovation Solution
An electro-deposited copper foil with fine crystal grains and a glossy surface is developed, featuring a tensile strength of 70 kgf/mm2 to 100 kgf/mm2 and minimal time-dependent mechanical property changes, achieved through a sulfuric acid base copper electrolytic solution containing specific additives like benzene ring compounds, sulfonates, and quaternary ammonium salts, which enhances mechanical strength and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional electro-deposited copper foil is used for fine-pitch wiring, then the wiring can be formed, but the mechanical strength is insufficient and tensile strength is lost when heated
Solution Approach 1:
The patent applies parameter changes by carefully controlling the electrolytic solution composition (adding specific additives like benzene ring-containing mercapto-functional compounds, sulfonates, and quaternary ammonium salts), current density (20-100 A/dm²), and temperature (10-50°C) to produce copper foil with fine crystal grains (3-10 μm) that maintains both high mechanical strength (70-100 kgf/mm²) and stability after heating (85% retention at 180°C for 60 minutes)
Solution Approach 2:
The patent creates a composite structure at the micro level by incorporating multiple types of additives into the electrolytic solution that work synergistically: benzene ring-containing mercapto-functional compounds for grain boundary control, sulfonates for surface treatment, and quaternary ammonium salts for crystal grain refinement. This composite approach produces copper foil with optimized crystal grain structure that simultaneously achieves high strength and heat stability
2Manufacturing precision
If copper foil thickness is reduced to enable fine-pitch wiring, then over-etching time is reduced, but mechanical strength and handling ease deteriorate
Solution Approach 1:
The patent uses parameter changes to decouple thickness from strength by controlling crystal grain size (3-10 μm) through electrolytic deposition parameters. This allows production of thin copper foil (12 μm or less) with fine crystal grains that maintain high mechanical strength (70-100 kgf/mm²), enabling fine-pitch wiring formation while preserving handling ease and mechanical integrity
3Manufacturing precision
If copper foil with low surface roughness is used, then fine-pitch wiring can be formed with reduced over-etching, but mechanical strength is compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the electrolytic solution composition and deposition conditions to produce copper foil with controlled surface roughness (Rz ≤ 2.0 μm) and fine crystal grain structure (3-10 μm). The addition of specific additives (benzene ring-containing mercapto-functional compounds, sulfonates, quaternary ammonium salts) enables simultaneous achievement of low surface roughness for fine-pitch wiring and high mechanical strength (70-100 kgf/mm²)
Solution Approach 2:
The patent applies local quality by creating a specific crystal grain structure (3-10 μm) throughout the copper foil that provides uniform mechanical properties. The fine, uniform crystal grains distributed throughout the material enable both low surface roughness on the bonding side and high mechanical strength, resolving the contradiction between surface quality and bulk strength
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 resulting copper foil maintains 85% or more of its tensile strength after heating and has improved handling characteristics, enabling the production of high-quality fine-pitch wiring and flexible printed wiring boards with reduced substrate weight and warp distortion.
Implementation Method 1
electrolysis of a copper electrolytic solution
Data Source
AI summary
Present invention provides an electro-deposited copper foil having the equivalent low-profile surface as in a conventional low-profile electro-deposited copper foil and extremely large mechanical strength and a method for manufacturing the same. The electro-deposited copper foil is formed by depositing fine copper crystal grains having a small deviation of grain-diameter. The electro-deposited copper foil has a low-profile and glossy surface and has extremely large mechanical strength expressed by a tensile strength as received of 70 kgf/mm2 to 100 kgf/mm2 and has a tensile strength after heating (180° C. for 60 minutes) corresponding to 85% or more of the tensile strength as received. The electro-deposited copper foil is manufactured by electrolysis using a sulfuric acid base copper electrolytic solution containing a compound composed of a benzene ring having a sulfo group bonded thereto, a sulfonate of an active sulfur compound and a polymer of a quaternary ammonium salt having a cyclic structure.