Abstract: A method of applying a coating to the inner layers of multilayer boards made of copper. The cured coating is capable of maintaining adhesion without outgassing for at least 10 seconds at 250.degree. C. It can be adhesion promoted for adherent electroless metal deposition with a chromic acid adhesion promotion solution. The coating composition comprises the product of reacting between 20 to 60% of a poly(vinyl acetal) resin with 80 to 40% of a phenolic resin in the presence of an acidic catalyst and a coupling agent having at least two amino substituted aromatic groups covalently bonded to a titanium or zirconium central atom via an oxygen containing linkage. The coating composition is applied to a metallic oxide film on the surface of the copper substrate.

Abstract: A method of manufacturing heat-exchanger excellent in the pitting corrosion resistance is disclosed, wherein, in the manufacture of aluminum heat-exchanger to be brazed under heat in the furnace of inert gas atmosphere using fluoride flux, Zn is disposed at a position of 430.degree. to 620.degree. C. in the furnace to melt and vaporize it and the vapor of Zn is allowed to contact with the fin material and the tube material coated with said flux simultaneously with the brazing under heat of these aluminum components, or the fin material coated with said flux and dried and the tube material without flux are assembled and retained for not less than 1 minute in the vapor of Zn of a temperature lower than the melting point of said flux and higher than the temperature, at which these components are heated, in the inert gas and thereafter brazing is performed at a temperature higher than the melting point of said flux.

Abstract: Adhesion of copper to a resin layer is improved by reducing a copper oxide layer with an aqueous aldehyde solution (a) while applying a potential of -1000 mV to -400 mV to the copper oxide layer, (b) after contacting with a metal piece made of copper or a metal nobler than copper, or (c) after contacting with an aqueous solution of alkali borohydride.