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52 SMT007 MAGAZINE I NOVEMBER 2018 Another main difference between these two parts was the introduction of the contamina- tion. With the glucose meter, it was an issue at the component manufacturer, but in the case of the external defibrillator, it was an issue with residual water-soluble flux remain - ing under the filter after an ineffective deion- ized water (DI) water-only wash process. The condition that made recovery of this even more difficult is there were already battery packs soldered onto the boards. This means the cleaning process had to be localized so moisture did not get on the rest of the board in areas that would be detrimental to the parts on the battery line. You can see in Table 1 that the level of chlo- ride and weak organic acid (WOA) was so high that cleaning was needed. The cleaning pro- cess required a specialized steam nozzle to be used at the filter location that was fortuitously located on the edge of the PCBA, so the likeli- hood of the steam condensate being deposited on moisture intolerant areas was very low. After the con- centrated steam cleaning process, the PCBAs were placed in an elevated heat and humidity chamber for 500 hours to ensure that the removal of the residues was fully effective and the product was no lon- ger at risk of field failure. Conclusion The point of this month's column was that when you are manufacturing high-reliabili- ty assemblies related to medical industry, it is critical to take a very close look at the assem- bly process and all other processes that can influence the end-use reliability—even seem- ingly unrelated processes, such as post-instal- lation cleaning. It really could be a matter of life or death. Now, back to "The Bachelor…" I mean "Nova." SMT007 Eric Camden is a lead investigator at Foresite Inc. To read past columns or contact Camden, click here. Researchers Elizabeth Vargis, a Utah State University (USU) assistant professor of biological engineering and Farhad Farjood, a Ph.D. student in Vargis' Lab, wanted to better understand the triggers of age-related macular degeneration (AMD), a degenerative eye disease and the leading cause of adult blindness in developed countries. Physical changes within the retina are an important factor in the development of AMD. However, the effect of physical changes during the disease is not clearly understood. Currently, there are no devices to realistically model varying levels of physical disruption available on the market. Therefore, the researchers created two new devices: one that mimics slow and continuous stress levels and one for mimicking high levels of stress. Using these devices to replicate stress on retinal cells, the researchers found that mechanical stress results in the expression of vascular endothelial growth factor, a protein that can cause disease initiation and progression. "There are many clinical studies taking place to discover the causes of disease," said Farjood. "Our work is an example of how engineering techniques can help us better understand the disease mechanisms." The study was published in Lab on a Chip. (Source: Utah State University) New Devices Test Retinal Cells all values in ug/in2 SAMPLE DESCRIPTION Filter 1 Filter 2 Filter 3 ID 1 2 CHLORIDE WOA SODIUM AMMONIUM 4.05 39.65 5.32 3.00 5.05 41.54 6.11 4.74 5.44 57.98 5.98 4.40 Sample Descrip on Filter 1 Filter 2 Table 1: Ion chromatography results of ferrite filter. USU Engineering Ph.D. student Farhad Farjood.

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