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Page 76 of 109

June 2016 • The PCB Magazine 77 A helpful trouble shooting guide for the development process operation is shown in Table 1. Summary With today's high-density circuit designs with increasingly finer lines and spaces, tighter control of the developing process is critical to provide circuit features that meet these specifi- cations. To ensure straight sidewalls and a cop- per surface free of unexposed resist, the process engineer must control the pH of the developing process within a more narrow range than was perhaps required when wider lines and spaces were the norm. Also, fresh developer solution must be continuously transported into these finer lines and spaces. Thus uniform developer solution movement is provided by high im- pingement fan nozzles. In addition, developing is aided by use of sufficient rinse water volume and pressure to re- move remaining developer-resist residues from the sidewalls and copper surfaces. PRIMARY IMAGING FOR PATTERN PLATING, PART 2: DEVELOPMENT It stands to reason that processes in printed circuit board fabrication are as much depen- dent on the equipment as the chemistry. By all means, follow a strict preventative maintenance schedule on your equipment. This includes re- placement of worn nozzles, changing of filters and cleaning additional debris and resist mate- rials that may remain in the sumps of the chem- ical and rinse chambers. PCB References 1. Private communication with Dr. Karl Di- etz, DuPont. Michael Carano is VP of technol- ogy and business development for RBP Chemical Technology. He can be reached by clicking here. Table 1.

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