| To enhance and improve binding force between interlayers has always been an important research content in manufacturing printed circuit board. The substrates of PCB(Printed Circuit Board) have been developed from the ordinary materials to the materials which have lead-free compatibility. The adhesion strength between interlayers is relatively low as lead-free substrates resins mostly have aromatic structure. As an interlayer processing technology in manufacturing process of PCB, brown oxidation process has a short processing time and the operation is easy to control. Brown oxidation treatment solution mainly takes organic additives which contains N, O, S atoms in organic heterocyclic compounds such as benzotriazole as corrosion inhibitors, with the system consisting of sulfuric acid, hydrogen peroxide and benzenesulfonic acid to react corrosion on copper, covering with a layer of corrosion film and forming a microscopic rough structure on the copper surface. Peel adhesion strength is an important indicator to measure the binding force between the copper foil and resin, after the treatment of brown oxidation, the copper interlayer gets better adhesion strength with resin under reaction conditions at high temperature.This paper mainly introduces the formulation of design and applied research of brown oxidation solution, the process of brown oxidation. Experimental section mainly discusses the influence of different brown oxidation treatment time and different concentration of complex inhibitors H4(with laboratory synthesized and part of the purchased inhibitors) on adhesion strength between the copper foil and resin, to verify the performance of the brown oxidation solution in the subsequent reliability tests. To guarantee the quality of the lamination can satisfy the requirements of peel strength, the parameters of lamination process are also been optimized. The experimental results were as follows:After the treatment of a new type of brown oxide solution developed by this paper, forming a uniform dense honeycomb structure on copper surface, and there is a certain depth gully between particles and holes. In the micro-etching depth of 1.5 ± 0.3 μm conditions, the peel strength between the copper foil after the brown oxide treatment and polyimide can be improved more than 25%, in the meanwhile, they can pass immersion tin tests and do not delaminate after six cycle tests in thermal performance, exhibiting good reliability.With the increase of oxidation time and the use of mixed inhibitors, the etching is more visible range and the depth etching is also been increased. The highest peel strength 16 N/cm was measured from electrolytic copper foil and 14 N/cm from rolled copper foil when the concentration of complex inhibitor H4 is 10 g/L and brown oxidation time is controlled about 60 s.Experimental studies on the lamination process parameters including preheating temperature, pressing temperature and main pressing time have been optimized. It is concluded that the factors influencing the binding force between copper foil and polyimide interface, namely, the effects on peel strength are in the order: preheating temperature, pressing temperature and the main pressing time. The optimum technological parameter: the preheating temperature is 250℃, pressing temperature is 180℃ and the main pressing time is 40 minutes, which are obtained by analyzing the test results with Minitab software. It is easier to formulate appropriate control range and to guide the production better. The delamination is occurred between organic copper oxide film and polyimide layer, rather than between copper foil and the substrate judging by XPS spectra. |
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