Single Step Electrolytic Method of Filling Through-Holes in Printed Circuit Boards and Other Substrates

An apparatus for electroplating a metal on an electronic substrate, wherein the electronic substrate comprises one or more features, wherein the one or more features comprise one or more through-holes and/or one or more blind micro-vias in the electronic substrate, the apparatus comprising:

• (a) means for securing the electronic substrate;
• (b) at least one counter electrode;
• (c) a plating tank for holding a copper electroplating bath;
• (d) an array of nozzles arranged to simultaneously impinge a first side and a second side of the electronic substrate arranged in the plating tank;
• (e) means for electrically polarizing first and second sides of the electronic substrate to initiate metal plating thereon;
• wherein the means for electrically polarizing the first and second sides of the electronic substrate comprises one or more rectifiers, wherein the one or more rectifiers are each capable of direct and pulse reverse plating, wherein the one or more rectifiers are each connected to a microcontroller capable of being programmed with a plating cycle comprising a pulse plating cycle and a second direct current cycle;
• wherein the plating cycle comprising the steps of, in order:
• 1) 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 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 on the first side and second side of the electronic substrate to shape the two opposing blind vias formed in the center of the one or more though-holes;
• and
• 3) direct plating for a second time period to fill the two opposing blind vias formed by pulse plating;
• wherein for the first time period, the one or more rectifiers are programmed with a first repeatable sequence comprising a set of pulse plating periods each set of pulse plating periods being composed of, in any order, (i) at least a first forward pulse period;
• (ii) at least a first reverse pulse period;
• (iii) at least a second forward pulse period;
• and (iv) at least a rest period, that is applied to the first side of the electronic substrate and a second repeatable sequence, the repeatable sequence comprising a set of pulse plating periods each set of pulse plating periods being composed of, in any order, (i) at least a first forward pulse period;
• (ii) at least a first reverse pulse period;
• (iii) at least a second forward pulse period;
• and (iv) at least a rest period, that is applied to the second side of the electronic substrate,
• wherein once the pulse plating for the first time period is completed, the one or more rectifiers are programmed to transition to a regular pulse plating cycle comprising forward plating pulses and reverse plating pulses for the second time period,
• wherein once the pulse plating is completed, the one or more rectifiers are programmed to transition to direct current.

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 printed circuit board, wherein the printed circuit board comprises:

• a metallized panel in which one or more through-holes are formed;
• wherein the printed circuit board comprises a conductive seed layer thereon to initiate electroplating of copper;
• wherein the one or more through-holes comprise:
• a) a first copper plating layer 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;
• b) optionally, a second copper plating layer deposited over the first copper plating layer, wherein the optional second copper plating layer shapes the blind vias formed by the first copper plating layer;
• and
• c) a copper filling layer, wherein the copper filling layer is deposited over the first copper plating layer and the optional second copper plating layer to fill the one or more through-holes;
• wherein the one or more through-holes are completely filled with copper, without any voids, dimples or other defects.

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 aside 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.