Copper Plate: From Ancient Metal to Multidimensional Carrier of Modern Technology

Copper, as one of the earliest metals used by humans, has always played an important role in the thousands of years of civilization in its plate form. From the exquisite patterns on ancient bronzes to the precise conductive layers in modern chips, copper plates continue to shine in the fields of industry, art, and technology with their unique physical and chemical properties. This plate with copper as the base (the purity is usually above 99%, or a small amount of alloy elements are added) not only retains the natural properties of copper, but also achieves precise control of performance through processing technology, becoming a special existence in the material family with both historical heaviness and modern technology.
1. Classification of copper plates: "Character shaping" of purity and alloys
The performance difference of copper plates first comes from their composition - the purity of pure copper and the diversity of alloys, which give them completely different "characters".

Pure copper plates are the "natural color school" in the copper family, with a purity of usually above 99.5%. According to the purity, they are subdivided into grades such as T1 (99.95%), T2 (99.90%), and T3 (99.70%). Among them, T2 copper plate is the most widely used. It retains the core characteristics of copper: electrical conductivity is as high as 98% IACS (International Annealed Copper Standard), and thermal conductivity is 397W/(m・K), second only to silver among all metals. This extreme conductivity makes it the "nerve veins" of the electronics industry - the commutator of the generator, the connecting terminals of the cable, and the conductive layer of the printed circuit board all rely on the high efficiency and stability of the pure copper plate to transmit current. At the same time, the ductility of pure copper is the best among metals, with an elongation of more than 45%. After cold rolling, the thickness of T2 copper plate can be as thin as 0.01mm (only 1/5 of the diameter of a hair), and it can be stamped into any complex shape, which is why it is indispensable in precision instruments. However, pure copper has low strength (tensile strength of about 200MPa) and is easy to deform, so it is more suitable for scenarios with extremely high requirements for electrical conductivity and thermal conductivity, but not demanding mechanical properties.

Alloy copper plates are a model of "performance customization". By adding elements such as tin, zinc, nickel, and beryllium, copper plates retain the core advantages of copper while gaining additional properties such as strength, wear resistance, and corrosion resistance. Brass plates (copper-zinc alloys) are the most common alloy copper plates. The ratio of 5%-45% zinc content forms a rich performance gradient: low-zinc brass (such as H62, containing 38% zinc) has excellent plasticity and can be rolled into 0.1mm thin plates for making musical instrument resonance chambers and decorative signs; high-zinc brass (such as H80, containing 20% zinc) has a strength of 350MPa and enhanced wear resistance, which is suitable for making valve sealing gaskets and clock gears.

Bronze plates (copper-tin alloys) are known for their "corrosion resistance and wear resistance". The addition of tin allows a dense oxide film to form on the surface of the copper plate, which is much more stable than pure copper in environments such as seawater and steam. Among them, tin bronze (such as QSn6.5-0.1) has a tensile strength of up to 400MPa and a hardness of about 80HB. It is often used for propeller blades of ships and linings of chemical pipelines. Beryllium bronze (such as QBe2) is the "king of strength" among alloy copper plates. After solution aging treatment, the tensile strength exceeds 1200MPa, while maintaining an elongation of more than 20%. It has high conductivity and fatigue resistance, and has become the core material for sensors and relays in the aerospace field.

Nickel-nickel plate (copper-nickel alloy) is characterized by "anti-magnetic and weather resistance". Alloys containing 10%-30% nickel can still maintain good toughness at low temperatures and are completely non-magnetic. It is an ideal choice for manufacturing precision instruments and deep-sea detection equipment. For example, B30 nickel-nickel plate (containing 30% nickel) is still not brittle in a liquid nitrogen environment of -196℃, and has excellent seawater corrosion resistance. It is widely used in low-temperature pipelines of LNG carriers.
2. Processing technology: the "transformation journey" from copper ingots to plates
The performance of copper plates depends largely on the precise control of the processing technology. From hot copper ingots to flat plates, each process reshapes the microstructure of copper and ultimately gives it specific functional properties.

The hot rolling process is the basic link in the forming of copper plates and is suitable for the production of medium and thick plates with a thickness of more than 5mm. The copper ingot is fed into the rolling mill at a high temperature of 700-800℃ (the melting point of copper is 1083℃, and this temperature range allows copper to maintain good plasticity). After multiple rolling passes, the thickness gradually decreases, and the internal grains are broken and reorganized to form a uniform structure. The hot-rolled copper plate retains the original toughness of copper, and the elongation can reach more than 35%. It is suitable as a "blank" for subsequent processing, such as copper plates for large sculptures, lining plates for chemical equipment, and other scenes with high requirements for thickness and toughness. However, high-temperature rolling will also form oxide scale on the surface, with a high roughness (Ra value of about 5-20μm), which needs to be removed by pickling before entering the next process.

The cold rolling process is the key to the precision of copper plates. It can further process hot-rolled plates to a thickness range of 0.01-5mm, and the dimensional accuracy is controlled within ±0.001mm. At room temperature, the copper plate is repeatedly rolled by a multi-roll mill (the deformation rate can reach 90%), the grains are significantly refined and elongated, and the strength is increased by more than 50% (for example, the tensile strength of pure copper after cold rolling increases from 200MPa to 300MPa), while the surface roughness is reduced to Ra0.1-0.8μm, showing a mirror-like finish. The "electrolytic copper foil" (thickness of only 3-18μm) used in the electronics industry is the ultimate embodiment of the cold rolling process. It can be evenly covered on the insulating substrate to form the conductive circuit of the integrated circuit. For scenes that require complex forming (such as the heat sink of a car radiator), cold-rolled copper sheets can also restore ductility through "annealing" treatment (keeping warm at 300-500℃), making the sheet less likely to crack during stamping and achieving one-time forming of complex curved surfaces.

Special forming processes have further expanded the morphological boundaries of copper sheets. The continuous casting and rolling process directly feeds the smelted copper liquid into the rolling mill, eliminating the ingot casting process, and can efficiently produce ultra-thin copper sheets (thickness 0.5-2mm), which are suitable for packaging, decoration and other fields; while the explosive composite process can combine copper sheets with materials such as steel and aluminum to form "copper-steel composite sheets", which not only retain the conductivity of copper, but also reduce costs with the strength of steel, and are often used in grounding devices in the power industry.
3. Core performance: natural advantages of copper and process enhancement
The wide application of copper sheets stems from their unique combination of properties - these properties come from the metallic nature of copper and are precisely optimized through processing and alloying.

Electrical conductivity and thermal conductivity are the core advantages of copper sheets. The conductivity of pure copper plates is close to that of silver (only about 5% lower), and the cost is much lower than that of silver, making it the "standard configuration" for power transmission and electronic equipment. In motor manufacturing, copper plates are processed into commutator plates to ensure the stability of current transmission through precise size control; in 5G base stations, waveguides made of high-purity copper plates can efficiently conduct high-frequency signals and reduce energy loss. In terms of thermal conductivity, the thermal conductivity of copper plates is 5 times that of steel and 1.5 times that of aluminum alloys. It is irreplaceable in the field of heat dissipation - the heat dissipation substrate of LED lights and the heat sink of computer CPUs all rely on copper plates to quickly conduct heat to ensure stable operation of equipment.

Corrosion resistance and antibacterial properties allow copper plates to stand out in special environments. Copper forms a dense oxide film (basic copper carbonate, i.e. "patina") in the air. This film can prevent further corrosion of the internal metal, so the copper roofs of ancient buildings (such as the Hall of Supreme Harmony in the Forbidden City in Beijing) can survive hundreds of years of wind and rain and remain intact. In the medical field, the antibacterial properties of copper plates (which can kill 99% of bacteria within 2 hours) are fully utilized. Hospital door handles and operating tables in operating rooms are made of copper alloy plates to reduce the risk of cross-infection. Experimental data show that the bacterial survival rate on the copper surface is only 1/1000 of that of stainless steel. This feature allows copper plates to gain new application space in the field of public health.

Ductility and formability give copper plates a dual expressive power of art and industry. The elongation of pure copper plates can reach 45%, and they can be made into any form through forging, stamping, etching and other processes - from the hollow patterns on bronze ware to the curved copper plate curtain walls on the exterior walls of modern buildings, they all show their "hard and soft" characteristics. In sculpture art, artists often use 0.5-2mm thick cold-rolled copper plates for hammering and forming, using their plasticity to create smooth lines; in the automotive industry, the water tank heat dissipation belt made of copper plates by stamping can expand the heat dissipation area through complex corrugated structures while maintaining structural strength.

Color and texture make copper plates an "evergreen" in the field of decoration. The rose gold color of pure copper is warm and elegant. Over time, it will form a natural oxidation color, presenting a unique retro texture; and through surface treatment (such as gold plating, antique aging), copper plates can simulate the appearance of precious metals such as gold and silver, and are used for metal trims of high-end furniture and the repair and decoration of ancient buildings. In modern buildings, copper curtain walls can present a gradient effect from bright copper to dark brown at different stages by controlling the oxidation rate, allowing the building facade to "grow" over time and giving the building dynamic vitality.
4. Application scenarios: Leap from traditional fields to the forefront of science and technology
The application map of copper plates not only continues the ancient tradition, but also continues to expand in the progress of science and technology, forming a multi-level and cross-field application ecology.

The power and electronics industry is the "main battlefield" of copper plates. In the field of power generation, the stator coils of large generators are made of high-purity copper plates (T2 or TU1 oxygen-free copper), and the uniformity of the conductive cross-section is ensured by cold drawing; in the field of power transmission, copper bars (thickness 5-100mm) processed from copper plates are used as busbars to transmit large currents in substations, and their current carrying capacity can reach thousands of amperes. The electronics industry places extreme demands on the precision of copper plates - in chip manufacturing, copper plates are sputtered into nano-scale conductive films as electrodes of transistors; in flexible displays, the lines made of ultra-thin copper foil (thickness 3μm) can bend with the screen without breaking, realizing the "foldable" feature.

The aesthetic value of copper plates is demonstrated in the fields of architecture and decoration. In modern buildings, copper curtain walls (thickness 0.8-1.2mm) not only meet the functional requirements of waterproof and weather resistance, but also become the "face" of the building with its unique metallic texture - the top decoration of the Dubai Burj Al Arab and part of the facade of the Shanghai Tower are all made of titanium-zinc composite copper plates, and the color is kept stable by controlling the thickness of the oxide layer. In interior decoration, etched copper plates can be made into hollow screens, and the laser-engraved patterns present delicate light and shadow effects under the light; while copper alloy plates (such as brass and nickel silver) are used for handles of high-end doors and windows and metal edging of furniture, which are both functional and decorative.

The special properties of copper plates have been explored in the medical and environmental protection fields. In addition to the antibacterial function mentioned above, copper plates have more applications in medical devices: the electrodes of electrocardiographs are made of high-purity copper plates to ensure the accurate transmission of bioelectric signals; the lining materials of artificial joints are made of copper alloy plates, which use their wear resistance and biocompatibility to reduce friction damage. In the field of environmental protection, catalyst carriers made of copper plates (such as copper-based catalysts in automobile exhaust purifiers) can promote the decomposition of harmful gases; and in seawater desalination equipment, copper-nickel alloy plates (nickel silver) are used to make pipes for heat exchangers because they are resistant to seawater corrosion, extending the service life of the equipment.

The cultural genes of copper plates have been continued in the fields of art and cultural creation. In printmaking, artists use 1-3mm thick copper plates for corrosion and engraving. The resulting copperplate prints can be repeatedly rubbed to retain delicate brushstrokes; in coin manufacturing, copper alloy plates (such as brass) are embossed and formed, and the weight of the coins is uniform through precise thickness control. In modern cultural and creative products, copper plates are made into bookmarks, badges, etc., and the oxidation and aging process gives them a retro texture, becoming a cultural carrier connecting tradition and modernity.
V. Future trends: performance upgrades and scene innovations
With the development of science and technology and industrial upgrading, copper plates are evolving towards high performance, functional complexity, and application scene innovation, constantly breaking through the boundaries of traditional cognition.
The research and development of high-performance alloy copper plates continues to advance. By adding trace alloying elements (such as niobium, zirconium, and chromium), scientists have successfully developed a "high-strength and high-conductivity copper alloy plate" with a tensile strength of up to 600MPa (3 times that of pure copper), while maintaining a conductivity of more than 85%, solving the problem of "strength improvement must reduce conductivity" in traditional copper alloys. This type of copper plate has been used in traction motors for high-speed railways and cable connectors for spacecraft, and has achieved remarkable results in weight reduction and energy saving. In addition, the research and development of shape memory copper alloy plates (such as copper-zinc-aluminum alloys) has made breakthroughs, which can restore the preset shape under temperature changes and are expected to be used in self-repairing valves for smart pipelines.

Functional composite copper plates have expanded the application dimension. Through coating technology, the surface of the copper plate can be covered with a graphene layer, which increases the conductivity by more than 10% and enhances wear resistance; and nano-titanium dioxide film is deposited on the surface of the copper plate to give it photocatalytic function for use in air purification equipment. In the field of new energy, copper-carbon composite plates are developed for bipolar plates of fuel cells, which not only ensures conductivity but also reduces weight; while copper-aluminum composite plates are used in electrode current collectors of power batteries, taking into account both conductivity and lightweight requirements.

Green manufacturing and recycling have become an industry consensus. The recovery rate of copper plates is as high as more than 95%, far exceeding other metal materials. Waste copper plates can be remade into high-purity plates after smelting and rolling, and their performance is almost unaffected. At present, the proportion of recycled copper in copper plate production in Europe and the United States has reached more than 60%. my country is also promoting the "short process" recycled copper process to reduce carbon emissions in the smelting process. In the processing link, the application of technologies such as laser cutting and water jet cutting has increased the material utilization rate of copper plates from 70% of traditional processes to more than 90%, further reducing resource consumption.

From ancient bronzes to modern chips, the application history of copper plates is almost synchronized with the history of human civilization. It does not have the toughness of steel or the lightness of aluminum, but it occupies an irreplaceable position in the competition of materials with its perfect performance balance, rich processing possibilities and unique aesthetic texture. In the future, with the advancement of science and technology, this ancient and young material will write new chapters in more unknown fields.