Abstract:
The subtraction process is prevailing in manufacturing printed circuit board although it causes problems such as high cost, serious environment pollution and long production cycle. These problems could be solved through the usage of the addition process. Through screen printing or inkjet printing, the prevalent addition process prints the conductive paste or ink directly on the insulating media to form the circuit. However, this process is limited by the shortage of the conductivity of the circuit, which could be improved significantly by applying electroless plating on the printed circuit. Unfortunately, it is impossible to apply electorless plate on the circuit pattern using current conductive paste or ink. A new addition process for manufacturing printed circuits was focused on. A novel ink was prepared by dispersing silver powders into the solution of acrylic resin with epoxy resin in ethanol, and then coated on the PET substrate to form an activating layer after thermal curing. This paper investigated the electroless copper plating on the activating layer and its binding force with substrate, the ratio of two kinds of resins and its effect on the crosslinking degree, bond strength and plating ability of the activating coating, relationships between the permeability and the plating ability of the coating in plating baths, and how the properties of the coating were affected by the amount, dispersion and dispersion stability of the silver powder during drying and curing. The results showed that the plating ability (on PET substrate) and the peeling strength of the activating adhesive increased by adjusting the curing crosslinking degree and the amount of the silver powder in the coating layer, respectively. When the crosslinking degree of the coating was 59.8% and the mass ratio of silver powder to resin was 2:1, a uniform and continuous plating layer could be obtained. The peeling strength of the layer reached 16 N/cm, a value exceeded the current industrial level. It was found that the plating ability was determined by the plating bath permeability. Furthermore, the dispersion and stability of silver powder determined the stacking structure of silver particles on the substrate, thus affecting the plating ability and peeling strength of the coating.