Printed Circuit Design & Fab - July 2008 - (Page 19) POSITIVE PLATING Brightener. The brightener or grain refiner is a member of a class of organic compounds characterized by the designation X-S. The grain refiner contains low molecular weight sulphur (S) and a second atom (X) of high polarity and/or ionic character. Typical brighteners additives are thiourea, disulfides, thiocarbamates, thiocarboxylic acid amides, etc. The “brightener,” by coulombic attraction, forms a layer on the surface where the additive assists in the refinement of the copper grain structure as it is deposited. The structure of the copper deposit is often described as fine grained or amorphous. Suppressors. Another component of the acid copper addition agent system will be high molecular weight polyether compounds, surfactants, polyoxyalkylene glycols, and others of similar structure. This additive acts as a suppressor by converting an unevenly distributed stationary cathode diffusion layer into a more evenly distributed layer. This action reduces the variation in copper deposit thickness across the surface caused by uneven diffusion paths that exist in the absence of a suppressor. In other words, the suppressor acts to prevent overplating in the high current density areas of the printed circuit board. Leveler. A third component of the additive system is referred to as a leveler. The leveler is highly polar, and by its nature adsorbs preferentially near the most negatively charged sites of the cathode (PCB). This action slows down the charge transfer of the copper ions to copper metal, thus slowing down the plating rate in those areas typically considered high current density areas. Basically, if over plating distribution and throwing power is to be improved, this is a necessary action. In the next installment of Positive Plating, we will look further into the electrochemistry of plating using the various mathematical models for determining plating uniformity. PCD&F MICHAEL CARANO is vice president for OM Group, Inc. and can be reached at mike.carano@omgi.com. BOARD SIMPLE Simplify PCB design with PADS libraries for every interconnect in our catalog. www.samtec.com/pads 6587 SAM PADS_PCDM.indd 1 3/23/07 11:12:00 AM JULY 2008 PRINTED CIRCUIT DESIGN & FAB 19 http://www.samtec.com/pads
Table of Contents Feed for the Digital Edition of Printed Circuit Design & Fab - July 2008 Printed Circuit Design & Fab - July 2008 Printed Circuit Design & Fab - July 2008 - (Page Cover1) Printed Circuit Design & Fab - July 2008 - (Page Cover2) Printed Circuit Design & Fab - July 2008 - (Page 1) Printed Circuit Design & Fab - July 2008 - (Page 2) Printed Circuit Design & Fab - July 2008 - (Page 3) Printed Circuit Design & Fab - July 2008 - (Page 4) Printed Circuit Design & Fab - July 2008 - (Page 5) Printed Circuit Design & Fab - July 2008 - (Page 6) Printed Circuit Design & Fab - July 2008 - (Page 7) Printed Circuit Design & Fab - July 2008 - (Page 8) Printed Circuit Design & Fab - July 2008 - (Page 9) Printed Circuit Design & Fab - July 2008 - (Page 10) Printed Circuit Design & Fab - July 2008 - (Page 11) Printed Circuit Design & Fab - July 2008 - (Page 12) Printed Circuit Design & Fab - July 2008 - (Page 13) Printed Circuit Design & Fab - July 2008 - (Page 14) Printed Circuit Design & Fab - July 2008 - (Page 15) Printed Circuit Design & Fab - July 2008 - (Page 16) Printed Circuit Design & Fab - July 2008 - (Page W1) Printed Circuit Design & Fab - July 2008 - (Page W2) Printed Circuit Design & Fab - July 2008 - (Page W3) Printed Circuit Design & Fab - July 2008 - (Page W4) Printed Circuit Design & Fab - July 2008 - (Page W5) Printed Circuit Design & Fab - July 2008 - (Page W6) Printed Circuit Design & Fab - July 2008 - (Page W7) Printed Circuit Design & Fab - July 2008 - (Page W8) Printed Circuit Design & Fab - July 2008 - (Page W9) Printed Circuit Design & Fab - July 2008 - (Page W10) Printed Circuit Design & Fab - July 2008 - (Page W11) Printed Circuit Design & Fab - July 2008 - (Page W12) Printed Circuit Design & Fab - July 2008 - (Page W13) Printed Circuit Design & Fab - July 2008 - (Page W14) Printed Circuit Design & Fab - July 2008 - (Page W15) Printed Circuit Design & Fab - July 2008 - (Page W16) Printed Circuit Design & Fab - July 2008 - (Page 17) Printed Circuit Design & Fab - July 2008 - (Page 18) Printed Circuit Design & Fab - July 2008 - (Page 19) Printed Circuit Design & Fab - July 2008 - (Page 20) Printed Circuit Design & Fab - July 2008 - (Page 21) Printed Circuit Design & Fab - July 2008 - (Page 22) Printed Circuit Design & Fab - July 2008 - (Page 23) Printed Circuit Design & Fab - July 2008 - (Page 24) Printed Circuit Design & Fab - July 2008 - (Page 25) Printed Circuit Design & Fab - July 2008 - (Page 26) Printed Circuit Design & Fab - July 2008 - (Page 27) Printed Circuit Design & Fab - July 2008 - (Page 28) Printed Circuit Design & Fab - July 2008 - (Page 29) Printed Circuit Design & Fab - July 2008 - (Page 30) Printed Circuit Design & Fab - July 2008 - (Page 31) Printed Circuit Design & Fab - July 2008 - (Page 32) Printed Circuit Design & Fab - July 2008 - (Page 33) Printed Circuit Design & Fab - July 2008 - (Page 34) Printed Circuit Design & Fab - July 2008 - (Page 35) Printed Circuit Design & Fab - July 2008 - (Page 36) Printed Circuit Design & Fab - July 2008 - (Page 37) Printed Circuit Design & Fab - July 2008 - (Page 38) Printed Circuit Design & Fab - July 2008 - (Page 39) Printed Circuit Design & Fab - July 2008 - (Page 40) Printed Circuit Design & Fab - July 2008 - (Page 41) Printed Circuit Design & Fab - July 2008 - (Page 42) Printed Circuit Design & Fab - July 2008 - (Page 43) Printed Circuit Design & Fab - July 2008 - (Page 44) Printed Circuit Design & Fab - July 2008 - (Page 45) Printed Circuit Design & Fab - July 2008 - (Page 46) Printed Circuit Design & Fab - July 2008 - (Page 47) Printed Circuit Design & Fab - July 2008 - (Page 48) Printed Circuit Design & Fab - July 2008 - (Page Cover3) Printed Circuit Design & Fab - July 2008 - (Page Cover4)
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