Process for neutralizing chloride ions in via holes in multilayer printed circuit boards.

摘要

@ A neutralization process is provided for neutralizing chloride ions in etched via holes in multilayer printed circuit boards. The process comprises two dip operations of the board in a solution of a neutralizing cleaner and water which is continuously re-circulated. This is followed by subjecting the board to a heated de-ionized cascaded water feed, an ambient overflow de-ionized water rinse, and conveyorized air drying. The solution of the neutralizing cleaner which comprises alkyl aryl sulfonite, ammonium sulfite, ammonium chloride, sodium chloride, and sodium sulfite has the ability to penetrate down to the bottom of the via hole and to attract the free chloride ions from the etchant residue. The de-ionized water feed and rinse steps rinse out and remove the neutralizing cleaner solution and any residuals formed by chemical reaction.