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SEPTEMBER 2020 I PCB007 MAGAZINE 75 individually differentiated. Chloride increases linearly with the consumption of cupric chlo- ride. Carbonate is formed as carbon dioxide from the air reacts with sodium hydroxide in the bath. Assuming air flow is constant, car- bonate will build linearly. Formate also tends to grow linearly at low levels through several reactions: Formate and other by-products contribute to the increase in specific gravity, which reduces plating rates. With this situation, one can find the occurrence of D-sep. Some ways to prevent D-sep include: • If D-sep occurs, raise the caustic level in the electroless copper solution to 9.5 g/L • Lower the operating temperature of the copper plating solution • Reduce the specific gravity of the bath • Increase the ability of the solution to flow through the holes – Increase vibration – Increase solution movement – Ensure proper rack agitation – Open up the spacing between boards Other areas that will help include: • Increase rinsing to clean the holes • Raise the temperature of the rinse water • Increase the pH of the rinse before electroless • Ensure desmear is giving a clean hole and not dragging any chemistry down the line Conclusion As a process engineer, one must be able to discern the difference between a Type 1 ICD and D-sep for the simple reason that the root causes are different. Thus, the troubleshooting exercise will require one looks at different ar- eas of the fabrication process to properly solve the ICD. PCB007 Michael Carano is VP of technology and business development for RBP Chemical Technology. To read past columns or contact Carano, click here. The device, developed by a team from the University of Cambridge, is a significant step toward artificial pho- tosynthesis, based on an advanced photosheet technol- ogy, and converts sunlight, carbon dioxide, and water into oxygen and formic acid—a storable fuel that can be used directly or converted into hydrogen. The results, reported in the journal Nature Energy, are a new method for the conversion of carbon dioxide into clean fuels. The wireless device could be scaled up and used on energy farms similar to solar farms, producing clean fuel using sunlight and water. Harvesting solar energy to convert carbon dioxide into fuel is a promising way to re- duce carbon emissions and transition away from fossil fu- Wireless Device Makes Clean Fuel From Sunlight, CO 2 , and Water els. However, it is challenging to produce these clean fu- els without unwanted by-products. "It has been difficult to achieve artificial photosynthe- sis with a high degree of selectivity so that you're con- verting as much of the sunlight as possible into the fuel you want rather than be left with a lot of waste," said first author Dr. Qian Wang from Cambridge's Department of Chemistry. "We were surprised how well it worked in terms of its selectivity. It produced almost no by-products," said Wang. "Sometimes, things don't work as well as you expected, but this was a rare case where it actually worked better." (Source: University of Cam- bridge)

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