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34 PCB007 MAGAZINE I OCTOBER 2022 your etchant. Depending on the etching solu- tion you utilize, the factors you need to con- trol will vary. If you are unsure how to monitor or maintain your etch process, it is best to seek experienced help and consult your etch equip- ment manufacturer. 3. Clean your nozzles regularly. As I mentioned, etching panels will introduce contaminants into your etching bath. With this, your nozzles can become clogged with debris. Frequently cleaning your nozzles is an easy measure you can take to prevent debris from affecting etch quality. Doing this will ensure that your panels receive a consistent spray pat- tern throughout the etch chamber. 4. Choose the correct resist. Different photoresists are compatible with different etching chemistries. To maintain your etch quality, it is necessary to ensure your resist and etchant are compatible. If they are not compatible, the resist can li off the sur- face of the panel during etching and fail to pro- duce the circuitry pattern you desired. Avoid- ing this problem can be done by researching your resist film and running a few test boards through your etcher to see if there are any signs of liing. 5. Start with a micro-etch. Although resist liing can be related to etchant compatibility, it can also be caused by contaminants on the surface before apply- ing the resist film. To make sure these contam- inants don't get in the way of adhesion, it is a good practice to have your panels go through a micro-etch cleaning process to remove these contaminants and restructure the surface to promote adhesion of your photoresist. It should be noted, however, that different pho- toresists will work better with different micro- etch solutions. If you take these measures, your etching pro- cess will be working at its fullest capacity to provide you with the high-quality features on your PCBs. PCB007 Christopher Bonsell is a chemical process engineer at Chemcut and an I-Connect007 columnist. To read past columns, click here. The multi-award-winning pioneer of nanosen- sors, Nanusens, has had its first patent granted in the US, with filings in other countries underway, and has more patents in the process of being applied for. These all protect its innovative technology of building nanoscale structures within a standard CMOS metal layers to create novel NEMS (Nano Electro Mechanical Systems) sensors. This first patent is for a round device with a diameter of less than 150 microns with three evenly distrib- uted springs that are spiral so that they can be long to give high sen- sitivity. This design can be used by Nanusens in a number of its sensor designs such as a bone conduction sensor, motion detector and accelerometer, among others. "You can't simply shrink a MEMS sensor design and build it with the CMOS metal layers," explained Dr Josep Montanyà, founder and CEO of Nanusens. "We have had to invent completely new sensor structures that will work reliably when made in a standard CMOS fab line, which means that they need to work with large residual stress and large process tolerances. These have taken years to perfect but now we have working NEMS in silicon so we are filing ten patent families that between them protect more than 100 inventions." (Source: Nanusens) Nanusens Granted First Patent with More in the Pipeline

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