Sequential electrodeposition of metals using modulated electric fields for manufacture of circuit boards having features of different sizes

A method for depositing a continuous layer of a metal onto a substrate having both hydrodynamically inaccessible recesses and hydrodynamically accessible recesses on its surface comprising

• immersing as an electrode an electrically conductive substrate having a generally smooth surface having both at least one hydrodynamically inaccessible recess and at least one hydrodynamically accessible recess in said surface in an electroplating bath containing ions of a metal to be deposited onto said surface,
• immersing a counter electrode in said plating bath,
• in a first electroplating step, passing a first modulated reversing electric current between said electrodes, wherein
• said first modulated reversing electric current comprises first cathodic pulses and first anodic pulses,
• said first cathodic pulses have a duty cycle less than about 50% and said first anodic pulses have a duty cycle greater than about 50%,
• the charge transfer ratio of said first cathodic pulses to said first anodic pulses is greater than one, and
• the frequency of said first pulses ranges from about 10 Hertz to about 12000 Hertz;
• and
• in a second electroplating step, passing a second modulated reversing electric current between said electrodes, wherein
• said second modulated reversing electric current comprises second cathodic pulses and second anodic pulses,
• said second cathodic pulses have a duty cycle greater than about 50% and said second anodic pulses have a duty cycle less than about 50%,
• the charge transfer ratio of said second cathodic pulses to said second anodic pulses is greater than one, and
• the frequency of said second pulses ranges from about 10 Hertz to about 5000 Hertz.