| As the use of electronic products and communication instruments increases, electromagnetic interference(EMI)has been a problem for the lifetime and efficiency of the instruments. Electromagnetism shield fabrics have been extensive researched because ti is possess the function of metallic gloss, electric, as well as flexility and bending resistance etc.. At present, Electroless plating is the main method for the p preparation of electromagnetism shield fabrics. The copper plating fabrics with its low cost be favored by people, it can be used for shielding electromagnetic radiation and interference. However, the oxidation resistance of copper coated fabrics is rather poor. Surface activation process always has been taken before the electroless copper plating on the fabrics. In the conventional activation processes, noble metal palladium is usually employed as the catalyst sites to initiate the electroless plating. The cost of the palladium has increased in recent years, which makes the electroless plating method rise in price. Thus, it is very important to develop a cost effective activation techniques. This paper aims to study a novel palladium-free and environmentally friendly surface activation process for the electroless copper plating. It is a cost effective activation method since Cu nanoparticles were successfully used as catalyst. A flexible electromagnetic shielding fabrics made from PET fabris plated with tin-copper combination were prepared. The weight percentage gain and surface resistance were discussed, technical condition was optimized as well, all of these were great meaningful to the practice production. At the same time,1,10-phenanthroline, phenolphthalein and polyethylene glycol as additives were applied in the solution, focused on the influences of the additives on the deposition rate, as well as on structures and surface morphology of the copper deposit. The properties of the tin- copper coated PET fabrics such as surface resistance, shielding effectiveness, oxidation resistance and adhesion of metal deposit to PET fabrics were investigated deeply, and anticipative research achievement was obtained. The primary achievements and conclusions are as follow:(1) The polymer-copper colloid was prepared, The polymer-copper colloid activation was carried out by immobilizing Cu nanoparticles on the PET fabrics surface as catalyst site by polymer for copper electroless plating. The polymer-copper colloid activation in one step substituted the activation and sensitization in two steps in traditional electroless copper plating. It is a novel palladium-free and environmentally friendly surface activation process. The experimental results showed that the polymer-copper colloid had perfect dispersivity and could be applied to electroless copper plating successfully, reduce the amount of noble metals and obtaining the copper plated fabrics with excellent electrical conductivity and electromagnetic shielding performance. Preliminary investigation of the process was performed. The surface resistance is reached to10mΩ/sq when plated copper for 60 min and the deposit weight percentage gain between 55%～65%. The deposition rate on the copper-coated PET fabrics increased from 5.6μm/h to 10.1μm/h when adding 2mg/L 1,10-phenanthroline to the electroless copper plating bath. At the same time, the surface resistance decreased from 13 to 9mΩ/sq, the copper deposit became compact and the color became copper-bright. Smaller crystallite size and preferred orientation of (220) and (311) plane were obtained by the addition of 1,10-phenanthroline to the bath. The deposition rate and conductivity were improved with the use of phenolphthalein, the influences of phenolphthalein is similar with1,10-phenanthroline. The H2 was easily released by adding polyethylene glycol. However, the influences were different as different molecular weight. As the molecular weight increased, the deposition rate decreased obviously, which resulted in higher surface resistance of copper-coated fabrics, the deposit morphology also changed significantly.(2) A flexible electromagnetic shielding fabrics made from PET fabrics plated with copper-tin combination were prepared. The thin layer of tin, which was non-hazard to skin, was coated by the way of electroplating on the copper surface. Tin is unharmful to person, thereby it can overcome the allergy poisoning and other side effects of the current common nickel-plated fabrics. After tin be plated on the copper-coated fabrics, the surface resistance decreased to 4.5 mQ/sq under the potential of 1 V for 6 min.(3) The copper plating PET fabrics existed weak antioxidant performance and poor corrosion resistance. Thus, a layer of tin was plated by the way of electroplating on the copper-coated PET fabrics, obtaining tin-copper coated PET fabrics with excellent electrical conductivity and electromagnetic shielding performance. The oxidation resistance and corrosion resistance were improved as well, and the adhesion of metal deposit to fabric is most strong. The shielding effectiveness reached the highest up to 77.76 dB in the range from 2000 MHz to 3000 MHz, and the attenuation rate was all above 99.99999%. In general, the outcome above all showed that the tin-copper coated PET fabrics of electromagnetic shield fabric was promising, and the research about Cu nanoparticles as catalyst site of a novel palladium-free surface activation process was great meaningful to its practical application. |
PDF Full Text Request