US 10,512,174 B2
Method of filling through-holes to reduce voids and other defects
Nagarajan Jayaraju, Framingham, MA (US); and Leon Barstad, Raynham, MA (US)
Assigned to Rohm and Haas Electronic Materials LLC, Marlborough, MA (US)
Filed by Rohm and Haas Electronic Materials LLC, Marlborough, MA (US)
Filed on Dec. 20, 2016, as Appl. No. 15/384,678.
Claims priority of provisional application 62/295,291, filed on Feb. 15, 2016.
Prior Publication US 2017/0238427 A1, Aug. 17, 2017
Int. Cl. C25D 5/02 (2006.01); H05K 3/42 (2006.01); C23C 18/16 (2006.01); C23C 18/38 (2006.01); C25D 3/38 (2006.01); C25D 5/56 (2006.01); C25D 7/12 (2006.01); H05K 1/09 (2006.01); H05K 1/11 (2006.01); H05K 3/00 (2006.01)
CPC H05K 3/429 (2013.01) [C23C 18/1653 (2013.01); C23C 18/38 (2013.01); C25D 3/38 (2013.01); C25D 5/02 (2013.01); C25D 5/56 (2013.01); C25D 7/123 (2013.01); H05K 1/09 (2013.01); H05K 1/115 (2013.01); H05K 3/0094 (2013.01); H05K 3/423 (2013.01); H05K 2201/032 (2013.01); H05K 2203/0723 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A method comprising:
a) providing a printed circuit board with a plurality of through-holes comprising a layer of electroless copper, copper flash or combinations thereof on a surface of the printed circuit board and walls of the plurality of through-holes, wherein the through-holes have diameters of 75-125 μm and the printed circuit board is 100 μm thick or greater;
b) immersing the printed circuit board in a copper electroplating bath comprising an anode; and
c) filling the through-holes with copper by a direct current cycle consisting of applying a current density for a first predetermined period of time followed by applying a lower current density for a second predetermined period of time, wherein the current density for the first predetermined period of time is of a shorter time period than the predetermined time period of the lower current density without repeating the direct current cycle.