Cu-Ni-Sn Alloy Foil Gloss Control for Autofocus Camera Modules
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Solution Overview
Problem
Thinner Cu—Ni—Sn based copper alloy foils with a thickness of 0.1 mm or less face challenges in mechanical polishing due to breakage risks from buffing and uneven thickness control, leading to poor solderability and adhesion, especially when used in autofocus camera modules.
Innovation Solution
Adjusting the 60-degree glossiness (G60RD) of the Cu—Ni—Sn based copper alloy foil to a range of 200 to 600 on the surface, measured parallel to the rolling direction, combined with increased passes in final cold rolling to maintain surface gloss and improve tensile strength, ensures enhanced solder wettability and adhesion strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical polishing is performed to remove the oxide film on Cu—Ni—Sn based copper alloy, then solderability is improved, but the surface develops uneven irregularities and discoloration requiring additional mechanical polishing
Solution Approach 1:
The patent replaces the mechanical polishing process with a controlled rolling process that achieves surface gloss through metallurgical mechanisms. The repeated rolling passes work harden the surface and create a uniform glossy appearance without the irregularities caused by mechanical buffing, thereby eliminating the need for mechanical polishing while maintaining solderability.
Solution Approach 2:
The patent changes the surface treatment approach from chemical-mechanical removal of oxide to controlled metallurgical processing through rolling. By adjusting rolling parameters (number of passes, rolling force, temperature), the surface achieves the desired glossiness (G60RD of 200-600) and uniformity without requiring subsequent mechanical polishing.
2Manufacturing precision
If mechanical polishing is performed on thinner Cu—Ni—Sn based copper alloy foils with thickness of 0.1 mm or less, then surface uniformity is improved, but the foil may break due to buffing and thickness control becomes uneven
Solution Approach 1:
The patent replaces the mechanical polishing system with a controlled rolling system that is gentler on thin foils. The rolling process distributes force uniformly across the foil surface through multiple light passes, avoiding the concentrated stress and buffing action that causes breakage in foils 0.1 mm or thinner, while still achieving the required surface uniformity and glossiness.
3Strength
If multiple passes in final cold rolling are performed to maintain surface gloss and improve tensile strength, then adhesion strength is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent makes the cold rolling process multi-functional by having it simultaneously achieve: (1) thickness reduction, (2) surface gloss development through work hardening, (3) tensile strength improvement through strain hardening, and (4) adhesion strength enhancement through surface activation. This eliminates the need for separate surface treatment processes, reducing overall manufacturing complexity despite multiple rolling passes.
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 approach results in improved solderability and adhesion strength for thinner Cu—Ni—Sn based copper alloy foils, making them suitable for use in electronic device parts like autofocus camera modules by ensuring consistent and high-quality surface finish and mechanical properties.
Implementation Method 1
the aging treatment that is a final step
Implementation Method 2
The Cu—Ni—Sn based copper alloy contains Ni and Sn which are extremely active and easily oxidizable, thereby forming a strong oxide film in an aging treatment
Implementation Method 3
the chemical polishing has to use a chemical polishing solution having extremely high corrosive power
Implementation Method 4
mechanical polishing is carried out using, for example, a buff, after the above chemical polishing
Implementation Method 5
In the rust prevention treatment, an aqueous solution of benzotriazole (BTA) is generally used
Implementation Method 6
increased passes in final cold rolling to maintain surface gloss and improve tensile strength
Data Source
AI summary
Provided is a thinner Cu—Ni—Sn based copper alloy foil that has a foil thickness of 0.1 mm or less, has improved solder wettability and improved solder adhesion strength, and can be suitably used as a conductive spring material for use in electronic device parts such as autofocus camera modules; a copper rolled product; an electronic device part; and an autofocus camera module. The Cu—Ni—Sn based copper alloy foil according to one embodiment of the present invention has a foil thickness of 0.1 mm or less; and contains from 14% by mass to 22% by mass of Ni, from 4% by mass to 10% by mass of Sn, the balance being copper and inevitable impurities; and has a 60-degrees glossiness G60RD of from 200 to 600 on a surface as measured in a direction parallel to a rolling direction.