The process of electroplating copper, tin, and nickel on ultra-thin aluminum foil

Perform plasma cleaning on the surface of aluminum foil andMagnetron Sputtering Nickel Copper AlloyAfter the intermediate layer is electroplated, a dense and well bonded copper and tin electroplating layer is obtained The effects of voltage during plasma cleaning, negative bias during magnetron sputtering, and alloy composition of the intermediate layer on the adhesion of subsequent coatings were discussed The influence of power waveform during copper electroplating and temperature during tin electroplating on the performance of the coating was pointed out The cost of copper-clad aluminum foil prepared by this process is only 1/4 of ordinary copper foil, and the weldability of the weakly acidic tin plated coating is good

Aluminum foil has a series of advantages such as light weight, airtightness, and good encapsulation, and has been widely used in fields such as electronics, packaging, and construction, especially in the innovation of emerging biotechnology, energy, and environmental protection technologies. The use and urgent development of aluminum foil and related technological expansion are becoming increasingly broad. Aluminum is a highly reactive amphoteric metal with high oxygen affinity. It is easy to form an oxide film on its surface, which poses great difficulties for aluminum foil electroplating. To obtain a good electroplating layer on aluminum foil, pre-treatment before electroplating is a key process.

In the field of electronic applications, in order to increase the conductivity and weldability of aluminum, it is necessary to electroplate metals such as copper and tin on its surface. Currently, many studies at home and abroad mostly use chemical methods, combining pre immersion and chemical plating, with complex treatment processes. After extensive experiments, the author used the pre-treatment method of surface plasma cleaning and magnetron sputtering intermediate layer plus electroplating process to obtain copper and tin coatings with fine crystallization, brightness, good weldability, and strong adhesion on the aluminum surface. Electroplating a certain thickness of copper on the surface of aluminum foil can replace copper foil and is widely usedElectromagnetic ShieldingIn terms of fields, printed circuit boards, and lithium-ion battery current collectors, a large amount of copper materials can be saved; It can also be used separately for electroplating tin layers or copper tin coatings, and applied in some emerging electronic fields.

2. Process Introduction

2.1 Materials

Using hard glossy foil with a thickness of 0.033mm, rolled with high-purity aluminum of LG3. Cut 10cm x 10cm test pieces from the rolled aluminum foil for future use.

2.2 Process flow

Plasma cleaning - biased sputtering intermediate layer (nickel copper alloy) - electroplated copper/or tin coating.

2.3 Process Description

2.3.1 Surface Cleaning

Hard glossy foil without softening treatment has residual oil on the surface and must be degreased. The degreasing process adopts plasma cleaning, which belongs to the dry process. After treatment, there is no residue on the surface, which is suitable for environmental protection needs. This treatment does not affect the inherent properties of the substrate, and the action time is short, the efficiency is high, and the process is easy to control. The process parameters are: discharge vacuum degree of 33Pa, loading gas of Ar, O2, etc., processing power of 150W, time of 1-3 minutes.

2.3.2 The operating conditions for magnetron sputtering intermediate layer are: basic vacuum degree<5.5 × 10-3Pa, sputtering pressure 0.12~0.20Pa, distance between target and substrate 60~100mm, sputtering power 100W, target diameter 60mm, DC negative bias 60V.

2.3.3 Electroplated Copper

The composition and operating conditions of the plating solution are: copper sulfate 180-220g/L, concentrated sulfuric acid 40-90g/L, chloride ions 40-90mg/L, opening agent 4-8mL/L, brightener A0.3-0.8mL/L, brightener B0.2-0.5mL/L, temperature 20-40 ° C, cathode current density 1-6A/dm2, air stirring, phosphorus copper anode (phosphorus content 0.03%~0.06%). The opening agent and brightener are imported products from Germany. The coating obtained by this process is not prone to pinholes, has high glossiness, low internal stress, good ductility, and uniform thickness; Fast deposition rate, stable plating solution, and high tolerance for impurities.

2.3.4 Weak acid tin plating [1]

The plating solution formula and process conditions are: stannous methanesulfonate (tin content 300g/L) 50mL/L (equivalent to Sn2 12-18g/L), opening agent 500mL/L, pure water 450mL/L, pH2.3~3.5， Bomei degree is 13-17 ° B é, temperature is 20-30 ° C, cathode current density is 0.1-1.0A/dm2, cathode and anode area ratio is 1:1, and the plating solution is forcibly circulated and stirred. The opening agent contains coordinating agents, conductive salts, dispersants, and Sn2 stabilizers. Its function is to conduct electricity, coordinate tin ions, increase anodic polarization, and refine the crystallization of the coating; Stabilize Sn2 to prevent oxidation and subsequent hydrolysis: stabilize the density of the solution.