A manufacturing process for thick aluminum foil for PCBs

Abstract

A production process for thick aluminum foil for PCBs involves controlling the casting and rolling zone thickness to 40-55mm, the thickness of the casting nozzle lip tip to 0.5-3mm, and the casting and rolling production speed to 680-850mm / min. Cold rolling: a 7mm thick billet is rolled to a finished product thickness of 0.125 / 0.15 / 0.17mm. The finished product undergoes straightening and bending to correct its shape, ensuring a 10-15I profile. When laid flat, the edge wave height does not exceed 3mm, ultimately yielding an aluminum foil with a tensile strength of 220-230MPa and an elongation of 4-7%. This process replaces the traditional 1100 alloy (0.4-0.6% iron content) with a 1060 alloy (0.2-0.35% iron content), reducing the viscosity of the molten aluminum. The reasonable Fe / Si ratio ensures that the tensile strength of the aluminum foil remains above 220MPa. By adjusting the appropriate liquid level, casting zone, and lip thickness of the casting nozzle, the horizontal lines generated during casting were resolved. By controlling the arrangement of processing passes and the roughness and convexity requirements of the production work rolls in the cold rolling process, the shape control was improved, and the product quality was greatly enhanced.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal processing, and more particularly to a production process for thick aluminum foil for PCBs. Background Technology

[0002] PCB stands for Printed Circuit Board, a crucial electronic component and support structure for electronic devices, primarily manufactured using electronic printing techniques. Printed circuit boards have undoubtedly secured a dominant position in the electronics industry. The use of PCBs in electronic devices eliminates errors from manual wiring due to the consistency of similar boards, and enables automated component insertion or mounting, automatic soldering, and automated testing, ensuring the quality of electronic equipment, improving labor productivity, reducing costs, and facilitating maintenance. Printed circuit boards have evolved from single-layer to double-sided, multi-layer, and flexible designs, each maintaining its own development trend. Future trends in PCB manufacturing technology focus on performance improvements such as high density, high precision, fine aperture, fine wires, small pitch, high reliability, multi-layering, high-speed transmission, lightweight design, and thinness, ensuring the continued vitality of PCBs in the development of future electronic devices.

[0003] Applications of Auxiliary Materials for PCB Drilling: Suitable for drilling ordinary circuit boards using aluminum sheet backing plates. Functions: 1. Effectively prevents drill bits from creating indentations and scratches on the circuit board surface during processing; 2. Provides positioning and guidance during drill bit descent, improving drilling positioning accuracy; 3. Excellent thermal conductivity rapidly dissipates heat generated by friction during high-speed drill bit descent, effectively preventing drill bit overheating, thus improving drill bit life and hole wall condition; 4. Prevents burrs from forming on the circuit board surface during high-speed drilling. Product Quality Requirements: Flat board shape, free from scratches, aluminum powder, and oil stains; surface should be free of streaks.

[0004] Currently, the main alloy used for thick aluminum foil in PCB manufacturing is 1100 alloy, with thicknesses typically ranging from 0.125 / 0.15 / 0.17mm. It can be produced using either casting or hot rolling processes. Due to the high surface finish requirements, the mainstream process in the market is hot rolling of raw materials to produce the corresponding products. Casting has a significant cost advantage over hot rolling due to its shorter processing time, and is gradually expanding its market share. However, the casting process has a unique characteristic: molten aluminum passes through a casting nozzle under the static pressure of the front chamber, forming a cast plate. Because there is a gap (0.3-0.5mm) between the nozzle and the casting rolls, the liquid metal is surrounded by a thin, arc-shaped oxide film. As the static pressure of the front chamber drives the film and the rolling rolls rotate, the oxide film is gradually stretched, eventually cracking and producing horizontal lines. As the final product thickness is achieved through cold rolling, these lines become more pronounced, forming water ripples (or mountain-and-water patterns). Because the iron content in 1100 alloy is generally between 0.4% and 0.6%, and the silicon content is relatively low, the increased iron content in the molten aluminum leads to the formation of more needle-like FeAl3 phases, increasing the viscosity of the molten aluminum. This makes it easier for the molten aluminum to adhere to the casting cavity of the casting and rolling mill, and as the production cycle lengthens, it is more prone to oxide film formation, increasing the frequency of casting and rolling striations. Currently, there is no mature casting and rolling process or cold working process available in the industry.

[0005] For the reasons mentioned above, a production process for thick aluminum foil for PCBs has been developed. Summary of the Invention

[0006] The purpose of this invention is to provide a production process for thick aluminum foil for PCBs to solve the above-mentioned problems. This process solves the problem of horizontal lines generated during casting by adjusting the liquid level height, the casting zone and the lip thickness of the casting nozzle. By adjusting the arrangement of processing passes and the requirements for the roughness and convexity of the production work rolls in the cold rolling process, the shape control is improved and the product quality is greatly improved.

[0007] To achieve the above objectives, this invention provides a production process for thick aluminum foil for PCBs, including casting and rolling: the casting and rolling zone is controlled at 40-55mm, the thickness of the lip leading edge of the casting nozzle is controlled at 0.5-3mm, the casting and rolling production speed is controlled at 680-850mm / min, the inlet cooling water temperature of the casting roll is 25-35℃, the outlet water temperature is 25-37℃, the water pressure is 0.4-0.6Mpa, the roughness of the casting roll is 0.8-1.2μm, and the medium-high roughness is 0.15-0.25mm, resulting in a 7mm thick blank.

[0008] Cold rolling: The 7mm thick billet is rolled to 1.2mm in two passes and cooled for 24 hours to prevent the material from sticking and scratching during continuous rolling, while controlling the material shape. At the same time, the appropriate oil index is adjusted to reduce the generation of aluminum powder and scratches during the rolling process. It is then rolled to 0.65-0.7mm, trimmed, and the roughness of the work roll is 0.4-0.6μm, with the middle and high of the work roll controlled at 0.02-0.1mm.

[0009] The material with a thickness of 0.65-0.7mm is rolled to 0.24-0.3mm in two passes, the roughness of the work roll is 0.2-0.4μm, and the middle and high of the work roll are controlled at 0.08-0.2mm.

[0010] Material with a thickness of 0.24-0.3mm is rolled into finished products with a thickness of 0.125 / 0.15 / 0.17mm. The roughness of the work rolls used is 0.1-0.3μm, and the height of the work rolls is controlled at 0.08-0.2mm. The finished products are then straightened by a tension bending and straightening equipment to ensure that the shape meets 10-15I. When laid flat, the edge wave height does not exceed 3mm. Finally, aluminum foil with a tensile strength of 220-230MPa and an elongation of 4-7% is obtained.

[0011] Preferably, the composition of the thick aluminum foil for PCB is as follows: Si: 0.04-0.15%, Fe: 0.2-0.35%, Cu: 0.01-0.05%, Mn: 0.005-0.01%, Mg: 0.005-0.01%, Zn: 0.005-0.01%, Ti: 0.01-0.03%, with the balance being aluminum; the sum of the above components is 100%.

[0012] The beneficial effects are as follows: Compared to hot-rolled billets, cast-rolled billets are more prone to surface scratches due to the lack of milling, making them more susceptible to aluminum powder detachment during cold working. Furthermore, due to the shorter rolling process and lower rolling force, cast-rolled billets generally have a less desirable shape than hot-rolled billets, placing stricter demands on subsequent cold working processes. Therefore, the arrangement of processing passes and the requirements for the roughness and convexity of the production rolls are crucial for shape control in the cold working process. This invention uses a 1060 alloy with an iron content of 0.2-0.35% instead of the traditional 1100 alloy with an iron content of 0.4-0.6%, reducing the viscosity of the molten aluminum. A reasonable Fe / Si ratio ensures that the tensile strength of the aluminum foil remains above 220MPa. By adjusting the liquid level, the casting zone, and the lip thickness of the casting nozzle, the transverse striations generated during casting are resolved. The improved shape control and significantly enhanced product quality are achieved through stricter requirements for the arrangement of processing passes and the roughness and convexity of the production rolls during the cold rolling process. Areas not detailed in this invention are existing commonly used technologies. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0014] Example 1

[0015] The alloy composition is: Si: 0.12%, Fe: 0.35%, Cu: 0.05%, Mn: 0.01%, Mg: 0.005%, Zn: 0.005%, Ti: 0.02%, with the balance being aluminum; the sum of all the above components is 100%.

[0016] Casting and rolling: The casting and rolling zone thickness is controlled at 48-55mm, the thickness of the lip leading edge of the casting nozzle is controlled at 0.5-3mm, the liquid level height at the front box flow channel is 7-9mm, the casting and rolling production speed is controlled at 680-850mm / min, the inlet cooling water temperature of the casting roll is 25-35℃, the outlet water temperature is 25-37℃, the water pressure is 0.4-0.6Mpa, the roughness of the casting roll is 0.8-1.2μm, the medium and high roughness is 0.15-0.25mm, and a billet with a thickness of 7mm is cast and rolled out.

[0017] Cold rolling: The 7mm thick billet is rolled to 1.2mm in two passes and cooled for 24 hours to prevent the material from sticking and scratching during continuous rolling, while controlling the material shape. At the same time, the appropriate oil index is adjusted to reduce the generation of aluminum powder and scratches during the rolling process. It is then rolled to 0.65-0.7mm, trimmed, and the roughness of the work roll is 0.4-0.6μm, with the middle and high of the work roll controlled at 0.02-0.1mm.

[0018] The material with a thickness of 0.65-0.7mm is rolled to 0.24-0.3mm in two passes, the roughness of the work roll is 0.2-0.4μm, and the middle and high of the work roll are controlled at 0.08-0.2mm.

[0019] Material with a thickness of 0.24-0.3mm is rolled into a finished product with a thickness of 0.17mm. The roughness of the working rolls is 0.1-0.3μm, and the height of the working rolls is controlled at 0.08-0.2mm. The finished product is then straightened by a bending and straightening equipment to ensure that the shape meets 10-15I. When laid flat, the edge wave height does not exceed 3mm. Finally, aluminum foil with a tensile strength of 220-230MPa and an elongation of 4-7% is obtained.

[0020] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A production process of thick aluminum foil for PCB, characterized by: Casting: the thickness of the casting area is controlled at 40-55mm, the thickness of the front lip of the casting nozzle is controlled at 0.5-3mm, the casting production speed is controlled at 680-850mm / min, the inlet cooling water temperature of the casting roller is 25-35℃, the outlet water temperature is 25-37℃, the water pressure is 0.4-0.6Mpa, the roughness of the casting roller is 0.8-1.2μm, the medium height is 0.15-0.25mm, and the casting thickness is 7mm; Cold rolling: the 7mm thick blank is rolled to 1.2mm through 2 passes, and is cooled for 24 hours to prevent material sticking and damage during continuous rolling, and to control the material shape and adjust the appropriate oil index to reduce the generation of aluminum powder and scratches during rolling; then rolled to 0.65-0.7mm, and the edge is cut, the working roller roughness is 0.4-0.6μm, and the working roller medium height is controlled at 0.02-0.1mm; The 0.65-0.7mm material is rolled to 0.24-0.3mm through 2 passes, the working roller roughness is 0.2-0.4μm, and the working roller medium height is controlled at 0.08-0.2mm; The 0.24-0.3mm material is rolled to the corresponding 0.125 / 0.15 / 0.17mm finished product, the working roller roughness is 0.1-0.3μm, the working roller medium height is controlled at 0.08-0.2mm, the finished product is corrected by the stretch bending straightening equipment to make the plate shape meet 10-15I, the edge wave height is not more than 3mm when laid flat, and finally the aluminum foil plate with tensile strength of 220-230MPa and elongation of 4-7% is obtained; The components of the thick aluminum foil for PCB are: Si 0.04-0.15%, Fe: 0.2-0.35%, Cu: 0.01-0.05%, Mn: 0.005-0.01%, Mg: 0.005-0.01%, Zn: 0.005-0.01%, Ti: 0.01-0.03%, and the balance is aluminum; the sum of the above components is 100%.