Study On The Stability Of Low Temperature And Low Stress Electroless Copper Plating Solution

Printed Circuit Board (PCB) is the core component of almost all electronic devices, due to it has many advantages such as light weight, small size, easy to standardize, etc.. Electroless copper plating process is the key technology for metallizationof of the printed circuit. Currently, copper plating factory and workshop almost throughout the world. While the computer industry and the rapid development of aviation industry, the electronic component signal interference shielding function put forward higher requirements, and also puts forward new requirements to the chemical copper plating: (1) The development of new additives, reduce costs and improve the rate of PTH. Choose good performance additives to improve electroless copper deposition rate and increase economic efficiency. (2) Extend the life of electroless copper plating solution. Electroless copper plating solution in a thermodynamically unstable state, therefore, to improve its stability and prolong life, improve the quality of the copper layer, reduce raw material consumption, reduce environmental pollution, are of great significance. Usefulness of electroless copper plating solution depends primarily on its stability. And one of important means to improve the stability of the plating solution is to add various additives in chemical plating solution.The thesis focused on the life issues of electroless copper plating solution. In order to improve the stability of the bath, added suitable stabilizers to the bath, while stabilizers would reduce the deposition rate. Therefore, This paper first studied the accelerator of chemical copper plating solution, on the basis of adding accelerator, chose the suitable stabilizers. By measuring the deposition rate and observing SEM images, found:L-malic acid,2,6-diaminopyridine, adenine and guanine have a better acceleration; sodium sulfite, sodium silicate, polyvinyl pyrrolidone, FC-80, ferron, sodium hexafluoride, FC-134 could be used as stabilizers of the system. Meanwhile sodium sulfite and adenine, guanine and ferron, L-malic acid and sodium silicate, L-malic acid and sodium hexafluoride reached synergistic effect. Added to the above-described stabilizer in the copper plating system that has studied by our laboratory, copper film obtain excellent surface morphology. And than by X-ray diffraction determined the stress of copper film. Also in the system have been obtained, adding appropriate amount of the above-mentioned stabilizers, the study found that only sodium hexafluorosilicate, FC-80, FC-134 could reduce the stress of the copper film, wherein the FC-134 showed the better result. Finally, analyzed the loss of the main component of plating bath by redox titration and acid-base titration, to determine the optimum amount of each component of complement. In the case of continuous supply of the respective components, the life of the bath was measured. In the original system, then added the stabilizer sodium sulfite, sodium silicate, polyvinyl pyrrolidone, sodium hexafluorosilicate, FC-80, FC-134, ferron, the number of cycles, respectively, the electroless copper plating solution extended to 4.68,4.91,5.72,5.61,5.79,6.03,4.41. FC-134 showed the best stability, period maximum of 6.03. That is to say copper plating solution can be used continuously for 54 hours, which greatly reduces the cost of copper plating industry, reduce environmental pollution, and plays a significant role in the rapid development of PCB industry.This paper finally got the copper plating solution which it is very stable, low temperature, low stress and can be continuously used, its composition is:copper sulfate pentahydrate 10g·L-1, sodium tartrate 28.25g·L-1, formaldehyde (37%) 5mL·L-1,L-malic acid 1.0mg·L-1,2,2’-bipyridine 2.0mg·L-1, sodium dodecyl benzene sulfonate (SDBS) 5.0mg·L-1, FC-80 or FC-134 3.0mg·L-1. In this system, it has high deposition rate, good morphology, low-stress and long life cycle. When adding 3.0mg·L-1 FC-80, minimum stress achievable is -5.80MPa, cycle is 5.79; when adding the same amount of FC-134 replaced, the minimum stress achievable is 4.42MPa, cycle is 6.03.