Abstract: An adhesion promoter composition foregoes the use of toxic heavy metals and also features a relatively large add-on window for an adhesion functioning in the assembly. The adhesion promoter composition is an aqueous solution comprising (a) ¼-3 parts by weight of a polymer selected from the maleic acid/polyacrylic acid copolymer, modified polyacrylic acid, or polyacrylic acid groups; (b) 1 part by weight of a phosphate component; and optionally (c) 1/10 to 5/10 parts by weight of a metal-containing component selected from the Zn, Ca, Mg and/or Al group.