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August 2014 • The PCB Magazine 53 CONTROLLING THE ENIG PROCESS FOR OPTIMUM EFFICIENCy AND PERFORMANCE continues Some Interesting Interactions The phosphorous content of most commer- cially available EN processes tends to increase with bath age; this is due to the incremental re- duction in plating rate from by-product build- up. Typically, the phosphorus level will increase by up to 0.5% per MTO. In addition to this or- dinary change in deposit phosphorous content, the level can also be altered through the use of specific additives as well as through modifica- tion of certain operating parameters. This is pre- cisely why it is important to understand the EN system one is using and be provided the proper control procedures to maintain the phos con- tent within a tight operating window. Phosphorous and Solderability There are some who believe that the key to eliminating black pad or hyper-corrosion rests with operating an EN solution that allows for higher phos content in the nickel deposit. Some advocate a phos content of upwards 11–12%. I disagree for reasons stated in previous columns. Again, the higher the phos content, the lower the immersion gold thickness. In addition, the solderability of the nickel surface is reduced as evidenced by previously published solder spread and wetting balance tests. Summary Manage the phosphorous content in the EN deposit. Higher phosphorous content will reduce immersion gold thickness. And, poor control of the phos content will cause higher-than-normal gold consumption as well. In addition, too low of a phosphorous content will lead to possibility of corrosion spikes in the nickel deposit. PCB Michael carano is with oMg electronic chemicals, a devel- oper and provider of processes and materials for the electron- ics industry supply chain. to read past columns, or to con- tact the author, click here. Printed Electronics Discussion Sponsored by: Taiyo America Publisher ray rasmussen moderates a discussion on the state of printed electronics today, with John andresakis, VP of strategic technology, oak-Mitsui; scott gordon, busi- ness development manager, duPont teijen films; and Josh goldberg marketing specialist, taiyo america. CliCk To View I-COnnECT007 FEATuRE PAnEl DISCuSSIOn