Neutralizing chloride ions in via holes in multilayer printed circuit boards

The process of drilling blind via holes in a printed circuit board composite which consists of a peel-apart-copper layer covering an epoxy substrate which consists of the steps of:

• etching holes through the peel-apart-copper layer with a cupric chloride etchant containing HCl acid;
• subjecting said holes to a circulating solution of Neutra-Clean and water to neutralize chloride ions in the etchant residue in said holes;
• cleaning said holes with de-ionized water to remove said Neutra-Clean solution and any residuals due to chemical reaction;
• and
• utilizing a laser drill to extend said etched holes into the epoxy substrate.

The process of drilling blind via holes in a printed circuit board composite which consists of a peel-apart-copper layer covering an epoxy substrate which consists of the steps of:

• etching holes through the peel-apart-copper layer with a cupric chloride etchant containing HCl acid;
• first and second 5 minute dip operations of said holes in a solution of 50% Neutra-Clean and 50% water at 120.degree. F.;
• subjecting said holes to a 2 minute heated de-ionized cascaded water feed at 100.degree. F.
• subjecting said holes to a 2 minute ambient overflow de-ionized water rinse;
• and
• utilizing a laser drill to extend said etched holes into the epoxy.

A process for neutralizing chloride ions in etched via holes in a multilayer printed circuit board, wherein said via holes are etched by a cupric chloride etchant containing HCl acid, said process comprising the steps of:

• first and second dip operations of said via holes in a solution of Neutra-Clean and water which is continuously re-circulated;
• subjecting said via holes to a heated de-ionized cascaded water feed;
• subjecting said via holes to ambient overflow de-ionized water rinse;
• and
• air drying the board.

A process for neutralizing chloride ions in etched via holes in a multilayer printed circuit board, wherein said via holes are etched by a cupric chloride etchant containing HCl acid, said process comprising the steps of:

• first and second dip operations of said via holes in a solution of Neutra-Clean and water which is continuously re-circulated, said solution containing ammonium chloride and sodium chloride which attract free chloride ions from etchant residue in said via holes;
• subjecting said via holes to a heated de-ionized cascaded water feed;
• subjecting said via holes to an ambient overflow de-ionized water rinse, said water feed and water rinse removing the Neutra-Clean solution and any residuals due to chemical reaction from said via holes;
• and
• air drying the board.

A process for neutralizing chloride ions in etched via holes in a multilayer printed circuit board, wherein said via holes are etched by a cupric chloride etchant containing HCl acid, said process comprising the steps of:

• first and second 5 minute dip operations of said via holes in a solution of 50%
• Neutra-Clean and 50% water which is continuously re-circulated at 120.degree. F.;
• subjecting said via holes to a 2 minute heated de-ionized cascaded water feed at 100.degree. F.;
• subjecting said via holes to a 2 minute ambient overflow de-ionized water rinse;
• and
• conveyorized air drying of the board.