Single step electrolytic method of filling through-holes in printed circuit boards and other substrates

A method of metallizing an electronic substrate comprising one or more high aspect ratio through-holes, the method comprising the steps of:

• a) preparing the electronic substrate to receive metal plating thereon;
• b) bringing the electronic substrate and at least one counter electrode into contact with an acid copper electroplating bath comprising a source of copper ions to be plated;
• c) electrically polarizing first and second sides of the electronic substrate to initiate metal plating thereon, wherein the acid copper electroplating bath plates the one or more high aspect ratio through-holes using a plating cycle until metallization is complete;
• wherein the plating cycle comprising the steps of, in order:
• 1) Asynchronous pulse plating for a first time period on a first side and a second side of the electronic substrate to cause copper to preferentially plate in the center of the one or more high aspect ratio through-holes, wherein the copper merges together in the center of the one or more high aspect ratio through-holes to form two opposing blind vias;
• 2) Synchronous pulse plating for a second time period to shape the two opposing blind vias formed in the center of the through-holes;
• and
• 3) Direct plating for a third time period to fill the two opposing blind vias;
• wherein the asynchronous pulse plating step comprises applying an electrical current to electrodeposit metal from the acid copper electroplating bath to the first side and second side of the electronic substrate, wherein the electrical current is applied as a pulse plating cycle comprising a repeatable sequence, the repeatable sequence comprising a set of pulse plating periods, each set of pulse plating periods including, in any order:
• (i) at least a first pulse of a first forward duration and first forward intensity;
• (ii) at least a second pulse of a reverse duration and reverse intensity;
• (iii) at least a third pulse of a second forward duration and second forward intensity;
• and
• (iv) at least a rest period.

A method of plating a metal on an electronic substrate, wherein the electronic substrate comprises one or more features, wherein the one or more features comprise one of one or more through-holes and/or one or more micro-vias in the electronic substrate, the method comprising the steps of:

• a) preparing the electronic substrate to receive metal plating thereon;
• b) bringing the electronic substrate and at least one counter electrode into contact with a copper electroplating bath comprising a source of copper ions to be plated;
• c) electrically polarizing first and second sides of the electronic substrate to initiate metal plating thereon, wherein the copper electroplating bath plates the one or more through-holes and/or the one or more micro-vias using a plating cycle until metallization is complete;
• wherein the plating cycle comprises the steps of, in order:
• 1) Pulse plating for a first time period on a first side and second side of the electronic substrate to cause copper to preferentially plate in the center of the one or more through-holes, wherein the copper merges together in the center of the one or more through-holes to form two opposing blind vias;
• 2) Pulse plating for a second time period using synchronous waveforms to shape the thus formed two opposing blind vias;
• and
• 3) Direct plating for a third time period to fill the two opposing blind vias;
• wherein the pulse plating step comprises applying an electrical current to electrodeposit metal from the copper electroplating bath to the first side and second side of the electronic substrate, wherein the electrical current is applied as a pulse plating cycle comprising a repeatable sequence, wherein the repeatable sequence comprises a set of pulse plating periods, each set of pulse plating periods including, in any order:
• (i) at least a first pulse of a first forward duration and first forward intensity;
• (ii) At least a second pulse of a reverse duration and reverse intensity;
• (iii) at least a third pulse of a second forward duration and second forward intensity;
• and
• (iv) at least a rest period;
• and
• wherein at least one of the pulses of the first forward duration and the first forward intensity or the pulse of the second forward duration and second forward intensity comprises a higher intensity pulse of a shorter duration within the first forward duration or the second forward duration, wherein the higher intensity pulse has an intensity that is about 100% to about 500% of the intensity of the first forward intensity or the second forward intensity.