Process for improving the solderability of electric circuit boards

A process for improving the solderability of a circuit board with conductor paths composed of copper, or copper alloy comprising the steps of

• A. first contacting conductor paths on a circuit board at least at areas to be soldered with a first solution for a time of from about 1 to 50 minutes, said first solution comprising on a 100 weight percent total weight basis.
• from about 2 to 20 weight percent of at least one dissolved non-ionic surfactant,
• from about 1 to 20 weight percent of at least one dissolved organic acid capable of producing a pH of not larger than 2 in water solution at a concentration of less than 50 grams per lite, and
• the balance up to 100 weight percent of any given such solution being water,
• B. first flushing the so first contacted areas with water for a period of time of at least about 12 seconds,
• C. secondly contacting the so first flushed areas with a second solution for a time of from about 2 to 10 minutes, said second solution comprising on a 100 weight percent total weight bases;
• from about 0.5 weight percent up to solution saturation of dissolved potassium persulfate
• sufficient added sulfuric acid to produce therein a pH of from about 1 to 4,
• from and including 0 up to about 0.5 weight percent dissolved phosphoric acid, and
• the balance up to 100 weight percent of any given such solution being water,
• D. secondly flushing the so secondly contacted areas with water for a period of time of at least about 10 seconds,
• E. thirdly contacting the so secondly flushed areas with a said first solution for a time of from about 1 to 5 minutes,
• F. thirdly flushing the so thirdly contacted areas with water for a period of time of at least about 10 seconds, and
• G. drying the so thirdly flushed areas in air.