Method for preparing substrate surfaces for electroless deposition

A method for conditioning the surfaces of a dielectric base material for the electroless plating of a conductive metal thereon, comprising the steps of:

• contacting the surfaces of the dielectric base material with an aqueous stannous chloride sensitizing solution comprising between 53 and 57 grams per liter of SnCl.sub.2 .multidot. 2H.sub.2 O with 37% HCl at a ratio of 50 milliliters per liter;
• rinsing the excess stannous chloride solution from the surfaces with hot water;
• contacting the surfaces of the dielectric base material with an aqueous palladium chloride activator solution, said aqueous palladium chloride activator solution formed by mixing about 50 grams of palladium chloride having a concentration of 0.13 to 0.17 grams per liter with approximately 3780 milliliters of 37% hydrochloric acid having a concentration of 10 milliliters per liter;
• contacting the surfaces of the base material with an aqueous palladium chloride/stannous chloride/hydrochloric acid seeder bath, said palladium chloride/stannous chloride/hydrochloric acid seeder bath comprising from 1.2 to 2.5 grams per liter of PdCl.sub.2, from 80 to 150 grams per liter of SnCl.sub.2 .multidot. 2H.sub.2 O, and from 290 to 360 milliliters per liter of 37% HCl;
• and,
• baking the base material at a temperature of at least 105.degree. C.