The basic principle of electroless copper plating
Since the birth of electroless copper plating technology, scientists have continuously explored the dynamic process of their heterogeneous surface catalytic deposition; proposed a variety of chemical deposition mechanism, hypothesis, tried to explain the experimental facts of electroless copper plating, increase the right The understanding of the nature of electroless copper plating. At present, most commercial electroless copper plating solutions use formaldehyde as a reducing agent and there are two basic chemical reactions in the reaction process.
Cu2++2e→Cu
2HCHO+40H→H2↑+2H20+2HC00+2e
Chemical reactions take place on the surface of catalytic heterogeneous phases, and there are no external power sources and electrons. The total reaction of electroless copper plating can be expressed as
Cu2++2HCHO+40H→Cu+H2↑+2H20+2HC00
This reaction formula only shows the relationship between the reactants and the final reaction product. The actual reaction process is much more complicated and may be divided into two or more steps. It is possible that the monovalent copper salt is formed as an intermediate product of the reaction. The reaction is still unknown. The exact process. It is generally believed that the electroless copper plating reaction process occurs through two consecutive reactions, ie, electrons are released in the anode partial reaction and consumed in the cathode partial reaction. The electroless copper plating reaction is controlled by the kinetics of the oxidation process of formaldehyde, that is, it is completely controlled by the partial reaction of the anode. The reaction of the two partial electrodes is not independent of each other; the oxidation reaction of formaldehyde occurs at the same time on the surface of deposited copper. Of course, the discussion of the electroless copper plating reaction mechanism is complicated, and it is also influenced by the concentration ratio of the main reactants; if the reactant concentration in the plating bath is extremely changed toward the direction of low copper ion concentration and high formaldehyde concentration, electroless copper plating The reaction mechanism also changes in the direction controlled by the partial reaction of the cathode