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40 The PCB Magazine • May 2015 ELECTrOPLATING THrOUGH-HOLES wITH DIFFErENT GEOMETry continues tion and current density. Based on these results, this system could be utilized for BMV plating for flip chip application. Process reliability and Physical Properties To establish through-hole fill reliability, cross sections were prepared after solder float- ing six times at 288°C per IPC procedure. The holes were then inspected. No cracks in the cop- per deposit or other defects were detected. The Microfill THF bath provides consistent deposit physical properties from a bath cycled up to 100 A.hr/L. Tensile strengths above 35 kpsi and elongations in the range of 20–30% were measured for deposits plated over a range of bath ages. Summary A novel DC through-hole filling process was formulated for high-volume HDI and sub- strate core layer metallization production. The process yields high quality results over a wide current density range. The process has already been commercialized at a number of customers and it is anticipated that there will be substan- tial future growth in adoption of this technol- ogy to fill through-holes. This 'single chemis- try does it all,' in combination with optimized plating conditions and plating equipment, is compatible with all though-hole geometries. The plated copper has excellent physical and mechanical properties, with a bright and lev- eled surface. This formulation is intended to be used with either vertical or horizontal in- line jet impingement equipment in both panel and pattern modes. All organic additives can be monitored and controlled by conventional CVS analysis techniques. Moreover, Dow Elec- tronic Materials is currently working with ECI Technology and AEL to introduce ECI's online chemical monitoring systems. This will provide analysis capabilities for front-end plating ap- plications in high-volume manufacturing fabs. The analytical techniques incorporated in the on-line analysis will provide complete chemi- cal metrology solutions to meet the stringent specifications necessary for such applications. This approach allows for reduction of chemi- cal reagent consumption, drastically decreases maintenance and waste generation, while in- creasing overall operational efficiency and reli- ability. PCB references 1. W.P. Dow, M.Y. Yen, M.J. Lefebvre, Studies of Microvia Filling Mechanism and a Novel Cu Plating Formula, IMPACT 2007. 2. Wei-Ping Dow, et al., Journal of the Elec- trochemical Society, 2008, 155, (12) pp. D750- D757. 3. U. Landau, "Copper Metallization of Semiconductor Interconnects—Issues and Pros- pects," Proceedings, Electrochemical Society (2001), 2000–26 (Chemical Mechanical Pla- narization IV), 231–252. 4. T. P. Moffat, D. Wheeler, and D. Josell, Journal of The Electrochemical Society, 2004, 151(4), C262-C271. 5. J. P. Healy, D. Pletcher, and T.H. Bailey, Journal of Electroanalytical Chemistry, 1998, 338. 6. M. Lefebvre, L. Barstad, L. Gomez, New Copper Electroplating Technology for Through- Hole Filling Hole Plating, IMPACT 2011. 7. M. Lefebvre, E. Najjar, L. Barstad, L. Go- mez, Next Generation Electroplating Process for HDI Microvia Filling and Through-hole Plating, IMPACT 2008. 8. M. Lefebvre, E. Najjar, L. Barstad, High Speed Direct Current Copper Electroplating Technology IMPACT 2011. elie najjar is senior R&D manager at enthone and was formerly a senior electrochemist with Dow Chemical Company. leon Barstad is lead electroplate engineer at Dow Chemical Company. Jayaraju nagarajan is senior electrochemist at Dow Chemical Company. Marc lin is market manager at Dow Chemi- cal Company. Maria Rzeznik and Mark lefebvre are R&D managers at Dow Chemical Company. FEaturE