After plasma cleaning and magnetron sputtering of Ni-Cu alloy intermediate layer on aluminum foil surface, dense copper and tin electroplating with good bonding force was obtained. The influence of voltage during plasma cleaning, negative bias during magnetron sputtering and alloy composition of the intermediate layer on the adhesion of the subsequent coating is discussed. The influence of the power supply waveform and the temperature during electroplating on the properties of copper plating is pointed out. The cost of copper-coated aluminum foil prepared by this process is only 1/4 of that of ordinary copper foil, and the coating has good solderability after weak acid tinning.

Foil has a series of advantages such as light weight, airtight, and good encapsulation, and has been widely used in electronics, packaging, construction and other fields, especially the innovation of emerging bioengineering, energy, and environmental protection and other related technologies, the use of aluminum foil and the application field to be developed and related technologies are expanding more and more broad. Aluminum is a very active amphoteric metal, with a high degree of oxygen philicity, it is easy to form an oxide film on its surface, which brings great difficulties to aluminum foil plating. In order to obtain good electroplating on aluminum foil, the treatment before electroplating is a key process.

In the field of electronic applications, in order to increase the electrical conductivity and weldability of aluminum, it is necessary to electroplate copper and tin and other metals on its surface. At present, many studies at home and abroad mostly use chemical methods, prepreg and electroless plating are combined, and the treatment process is more complex. After a lot of experiments, the author has obtained copper and tin coatings with fine crystal, bright, good weldability and strong bonding force on the surface of aluminum by using the pretreatment method of surface plasma cleaning and magnetron sputtering and electroplating. Plating copper of a certain thickness on the surface of aluminum foil can be used instead of copper foil, which is widely used in electromagnetic shielding fields, printed circuit boards and lithium-ion batteries, so as to save a lot of copper; Can also be used alone for electroplating tin layer or copper tin coating, used in some emerging electronic fields.

Process introduction

1.1 Materials

A hard light foil with a thickness of 0.033mm is rolled with LG3 high purity aluminum. Cut 10cm×10cm test pieces from rolled aluminum foil for use.

1.2 Process flow

Plasma cleaning - Bias sputtering intermediate layer (nickel-copper alloy) - copper/tin plating.

1.3 Procedure specification

1.3.1 Surface cleaning

Hard light foil has not been softened, there is residual oil on the surface, and it must be degreased. Degreasing using plasma cleaning, it belongs to the dry process, no residue on the surface after treatment, suitable for environmental protection needs. The treatment does not affect the inherent properties of the matrix, and the action time is short, the efficiency is high, and the process is easy to control. The process parameters are as follows: discharge vacuum 33Pa, loading gas Ar, O2, etc., processing power 150W, time 1~3min.

1.3.2 The operating conditions of the middle layer of magnetron sputtering are: basic vacuum<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.

1.3.3 electrocoppering

The composition and operating conditions of the bath are: Copper sulfate 180~220g/L, concentrated sulfuric acid 40~90g/L, chloride ion 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%). Cylinder opening agent and brightener are imported from Germany. The coating obtained by this process is not easy to produce pinholes, high gloss, low internal stress, good ductility and uniform thickness. The deposition speed is fast, the plating solution is stable, and the impurity tolerance is high.