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MEDICAL ELECTRONICS FEATURE


Critical cleaning of complex medical assemblies


Jay Tourigny, senior vice president at Microcare explores next-generation cleaning and how this is increasing the reliability of medical electronic assemblies


E


lectronic medical device technology is continually advancing and is helping to


shape the future of healthcare. Product design and development is an integral part of this innovation. Today’s designers are faced with the complexities of increasing capability and reducing the size of components to work with increasingly multifaceted devices. PCBAs (printed circuit board assemblies) found inside devices like wearable insulin pumps and external ECG monitors are now smaller and more complex than ever before, making it more challenging for electronic device manufacturers to ensure production is completed efficiently and without error. Regulations imposed on the medical


sector to ensure superior quality of medical devices is putting further pressure on manufacturers to produce reliable assemblies. If a PCBA within a medical device were to fail it could be catastrophic. Devices must therefore contain components that will stand the test of time and function consistently without fault.


CONTAMINATION: A KEY CAUSE FOR DEVICE FAILURE IS One of the main causes of electronic device failure is contamination on the PCBA. The smallest contaminant can form a barrier between electrical contacts. Dirty PCBAs are susceptible to a whole host of problems ranging from electrochemical migration and delamination to parasitic leakage, dendrite growth and shorting. This is why cleaning is so crucial to ensuring the reliability of a device. Almost all medical devices require


cleaning during manufacture to remove particulate, flux, oils or inorganic contamination resulting from the manufacturing process. The challenge is to identify a process that is suitable for the critical cleaning of complex assemblies, intricate shapes and delicate parts. It must also stand up to strict regulations such as the IEC 60601-1 standard specifically designed for medical electrical equipment and systems. It necessitates that the basic safety and essential performance of the medical device be maintained. Cleaning is one of the central practices to help to meet this requirement.


Vapour degreasers offer a simple,


repeatable process that is effective at removing contaminants. The low viscosity and surface tension ratings of modern cleaning fluids used within a vapour degreaser, combined with their volatility, allow them to clean very effectively, particularly around complex parts. Vapour degreasing ensures all surfaces of the PCBA are effectively cleaned and free of contamination. Modern, non-flammable,


EFFECTIVE CLEANING EQUALS BETTER RELIABILITY In the medical electronics industry, the process of cleaning compact PCBA configurations can be difficult. Removing contaminant under and around tightly- spaced components is a challenge. The reduction in pitch between conductors collects and traps contaminants making cleaning even more complicated. Consideration has to be given to the


solder joints found within these devices. If defective, they can cause a large percentage of PCB failures, so removing any harmful contaminant and residue is key to their success. Advanced modern cleaning methods enable engineers to specify stronger, more active fluxes, which results in better solder joints, eliminating problems with cold joints, insufficient wetting, bridging, and shorts. However, these more robust fluxes can be problematic to remove. It is predominantly because of this challenge that vapour degreasing is a favoured method when it comes to cleaning PCBAs. Vapour degreasing not only ensures the


cleanliness of the device but also satisfies the economic and regulatory requirements needed within medical electronics.


Figure. 1:


Medical Vital signs monitor


environmentally-progressive cleaning fluids, specifically designed for a vapour degreasing system, can make a substantial enhancement to performance, reliability and longevity of PCBAs. It also has the benefit of reducing the risk of bioburden both on the manufacturing floor and on the finished product – critical when it comes to the validation of medical devices and the manufacturing process. For designers, more effective cleaning


means fewer limits in product design. Therefore, advancements in medical electronics can flourish in the knowledge that devices can be cleaned reliably, reducing the risk of malfunction. Device performance has to be the most


fundamental concern for manufacturers. As the trend in circuit board miniaturisation continues to satisfy design potential, the complexity and high-density design of intricate PCBAs causes a greater likelihood for cleaning challenges and consistency problems. Within the medical industry this could mean life or death, so reliability is of paramount importance. Vapour degreasing used with modern


Figure 2:


Miniature PCBA: Printed circuit boards continue to shrink in size and grow in complexity


cleaning fluids offers a sound answer. It enables a critical cleaning process that ensures contaminated PCBAs are not the cause of any failure. Advances in cleaning fluid technology means vapour degreasing sustains an easily validated cleaning process. Pus, it reduces the risk of bioburden, with in a cost-effective and sustainable way. Progressive next- generation cleaning fluids allow for better PCBAs to be built and deployed, therefore creating new capabilities for the future of medical electronics.


MicroCare Medical www.microcare.com


/ ELECTRONICS ELECTRONICS | NOVEMBER 2020 35


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