Wearable healthcare is on the rise. In fact, the wearable medical devices market size was valued at over USD 9.0 billion in 2018 and is expected to witness 39.4 percent CAGR from 2019 to 2025. The demand for digital wellness, remote monitoring, and diagnostics means an increasing requirement to produce complex miniature electronic components with ever-tighter tolerances. This brings with it printed circuit board assembly (PCBA) cleaning challenges that must be addressed at the design stage in order to ensure reliability. This article discusses how PCBA cleaning can be incorporated into the planning and production of wearables and the essential methods to be used.

Wearables — Helping to Improve Health

Trends in wearables like smartwatches to monitor health at home accelerate as more consumers take control of their own fitness and well-being. The same is true for patient monitoring. New tools are paving the way for a more connected healthcare system. Technology allows remote patient monitoring (RPM) to become an integral part of modern healthcare. As the capability of RPM advances, wearables that were once mainly used for consumer health, are now being widely adopted by health practitioners. Wearable monitoring devices allow patients with long-term and chronic illnesses to incorporate convenient health monitoring into their daily lives without the need to attend regular office visits.

Healthcare providers monitor patients outside of the clinical setting and receive real-time results. This means improved care by turning it from clinic-centered analysis into home-centered monitoring. Making it both more affordable and accessible.

Facilitating Cleaning for Reliability

These highly advanced wearables are packed with intricate and complex electronic components and PCBAs. Building these miniature, multifaceted devices can be challenging for manufacturers as it is critical that they are 100 percent reliable. Designers must facilitate effective approaches at the earliest stage to ensure the device works, and continues to work, as it should. It is important to consider cleaning processes in the initial planning stages as this directly impacts the reliability of the device. If the correct cleaning method is not investigated and determined early in the design process, device malfunctions with catastrophic results to the patient can result.

Functionality and reliability are important qualities for all medical devices. Improving the accuracy of a component such as a PCBA can result in higher capability and consistency for these systems. Wearable medical devices need to be flawlessly manufactured to meet the validation requirements, customer quality standards, and regulations set by governing bodies to ensure reliability; cleaning is a critical part of this.

Thanks to technological advancements in electronics, wearables are smaller, lighter, and less invasive but introduce their own problems when cleaning. The transition to smaller, condensed PCBAs is making circuit board cleaning more difficult. Contamination is one of the primary causes of PCBA malfunctions, so it is vital to implement tried and tested cleaning processes during production.

Contaminated PCBAs are vulnerable to a number of problems including parasitic leakage, electrochemical migration, delamination, dendrite growth, and shorting. PCBAs used within wearable medical devices like RPM are small, densely packed, and multi-layered. They often have bottom termination components that are low clearance or zero clearance, making it difficult to clean and rinse away contaminants under them. This presents a cleaning challenge to manufacturers as they look for ways to ensure that contamination is removed under and around these tightly spaced components.

The low stand-off between conductors collects and traps manufacturing contaminants like solder balls and flux residue. In many instances, active fluxes or flux residue may stay on the PCBA after reflow in wave machines or after hand soldering. Other contaminants, like ink and fingerprints, require removal for optimal circuit board reliability, and the task to clean escalates.

Understanding the Contaminant

Selecting the right cleaning fluid and method is important as it ultimately contributes to the functionality and reliability of the PCBA. It needs to be a process that can successfully clean intricate and complicated miniature components. It is also important that the cleaning process is validated and is proven to be consistently effective and repeatable.

To clean successfully, it is crucial to first identify the contaminant that needs to be removed and then select the best combination of cleaning fluid and method to effectively remove it. Balancing these factors acceptably enhances PCBA reliability.

PCBAs can be exposed to a variety of different contaminants during the production process. Thorough investigation of the contaminant to be removed before selecting a cleaning fluid helps to guarantee cleanliness. Contaminants are categorized into four main groups: insoluble particulate, organics, inorganics, and water.

Insoluble particulate is classified as a polar contaminant and is commonly found on PCBAs. It includes soils like dust, cloth fibers, and metal chips. Removing this type of contaminant often requires agitation in addition to the cleaning fluid itself.

Organic, or nonpolar contaminants like solder pastes and fluxes, sometimes stay on the PCBA after assembly. These are dissolved and removed with a mild to medium strength flux remover.

Inorganic, polar contaminants are the residue left by lead-free and no-clean fluxes and solder pastes. This is an extremely challenging contaminant that requires more intensive cleaning with stronger cleaning fluids and flux removers. It is important in these instances that material compatibility of the fluid is investigated before use. If a cleaning fluid is too strong, it may damage sensitive PCBA materials such as polycarbonate and acrylic.

Water, which comes in to contact with PCBAs through the use of aqueous cleaning systems, for example, can remain trapped in more densely populated circuit boards. This leaves water spots once dried. Or if moisture is left behind, problems including corrosion, delamination, electrochemical migration, and dendrite growth can occur, all of which impact the function and reliability of the PCBA.

Miniature PCBA: The transition to smaller, condensed PCBs is making circuit board cleaning more difficult. (Credit: MircoCare Medical)

Vapor Degreasing: The Key to More Reliable Wearables

Vapor degreasing is a cleaning process with all the essential qualities to ensure the cleanliness of the device. It also satisfies the economic, validation, and regulatory requirements needed within medical device manufacturing industry. Vapor degreasers use a closed-loop system containing two chambers: the boil sump and the rinse sump. The boil sump contains a specially designed low-boiling nonflammable cleaning fluid. This is heated and the parts are immersed and cleaned in the fluid. Once cleaned, the parts mechanically transfer to the rinse sump for final cleaning in a pure, uncontaminated fluid. The parts come out clean, dry, and spot-free. The process is simple, repeatable, and easy to validate.

Modern vapor degreasing fluids used within the system include exceptional materials compatibility, making them suitable for cleaning delicate plastic parts or mixed-material devices. They also have low surface tensions and high liquid densities. This allows the cleaning fluid to easily flow around tight-fitting and low-mounted components to clean under them thoroughly. Because the cleaning fluid used within a vapor degreaser also dries quickly, no moisture is left behind to cause problems like corrosion or dendrite growth.

Importantly, vapor degreasing fluids are hostile to bacteria. So, by using this cleaning process, it ensures a pyrogenfree cleaning environment. Vapor degreasing simplifies process control requirements for eliminating bioburden and offers an easy way to validate the manufacturing process.

Improve Cleaning to Enhance Reliability

Wearable technology is changing the way health-related data are collected and analyzed. The future for its use within the medical sector is not set to slow down. In fact, with the ongoing coronavirus crisis, it is becoming even more essential as healthcare providers look for additional contactless monitoring methods.

Medical wearables significantly improve patient service by providing accurate and timely health data to physicians. The upward trend in this technology requires manufacturers to make smart decisions in how they produce these innovative products. In order to guarantee reliability, this must encompass everything from carefully constructed designs, to exacting production methods. An important and step that must be addressed from the earliest stage is consistent and precise cleaning during manufacture. For wearables like RPM to perform their crucial functions, they must be critically clean before further processing or packaging.

It is recommended that medical device manufacturers work with a critical cleaning partner that specializes in cleaning fluids designed specifically for the medical sector. They can help choose the best cleaning process and cleaning fluids to deliver quality cleaning results along with the performance, reliability, and longevity required for this innovative and complex technology.

This article was written by Jay Tourigny, Senior Vice President at MicroCare Medical, New Britain, CT. For more information, visit here .