PCB007 Magazine

PCB-Apr2015

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58 The PCB Magazine • April 2015 Equipment Modifications As the reader has been inundated with chemical process controls, one must also un- derstand proper equipment plays a key role in process performance. I wish to stress that while high-quality OSP chemistry will only re- quire 45–60 seconds to form an organic film on the copper surface, which also implies that the method of chemistry delivery to the circuit boards provides for uniformity in the contact of the chemistry to the circuit board. And the equipment (if using conveyorized mode as is preferred by this author) must be designed with squeezing rollers at both the entry and exit of the actual OSP chamber (Figure 4). The entry roller is necessary to prevent rinse water drag-in to the OSP chemistry which will lead to dilution of the OSP chemistry. This in turn will reduce the thickness and uniformity of the organic film. Thus, the rollers provide several functions with drag-in and drag-out of the OSP chemistry the most critical. On the exit side, the squeezing rollers mini- mize OSP chemistry drag-out furthering im- proving the economy of an already low-cost final finish. The OSP is applied via a set of spray noz- zles both above and below the printed circuit boards as they are transported through the chamber. This ensures that there is uniform so- lution flow across the entire panel and through the vias. Again, as has been the theme throughout these columns, getting to the root cause of any potential defect or defects requires a thorough understanding of the chemical and mechanical aspects of the process. OSP is no exception. PCB realtimewith.com CliCk To View vIDeo IntervIew Inkjet solder mask has for many years been a distant, near-impos- sible goal for the PCB industry. Hopes have been raised on sev- eral occasions, only to fade when the ink either won't jet or pass end-user qualification. now, Taiyo's many years of develop- ment, in cooperation with equip- ment manufacturers, have result- ed in a successful formulation. Inkjet Solder Mask Becomes a Practical Reality by Real Time with... IPC APEX EXPO 2015 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. trouble In your tAnk COPPER DISCOLORATION AND OTHER CONCERNS WITH OSP continues

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