Cleanliness is not only for devices used in medicine. In fact, avoiding things like ionic contamination during the manufacture and assembly of circuit boards for medical electronic devices is a major issue. This issue runs deep across many parts of medical device manufacture and use. That shows how important it is. Rules from agencies such as the FDA and standards from groups like ISO 13485 and IEC 60601 touch many parts of PCBA design and manufacture. Here we focus on those rules and on the PCB cleanliness standards that matter for medical electronic products.
Standards to make sure medical electronic devices are clean
Medical electronic devices are special. Many devices do more than read the body. Some connect to or touch the body. Simple tools like swabs and tongue depressors do touch people but they have low risk. Those tools are class 1 devices. Electronic medical devices are often class 2 or class 3 because they pose higher risk to the patient.
No matter the class, every medical device maker must meet the quality rules in the medical device laws. The rule ISO 13485 covers design, manufacture, test, and monitoring for medical devices. It lists steps and checks that help make devices work well and last. Many of those steps depend on cleanliness. Another rule, ISO 14971, looks at the stages and steps in development that can cause risk. For example, the choice of PCB surface finish can raise the chance of adding contaminants to the board. Those contaminants can stay on the board during make and hurt board performance or reliability after the device ships.
The PCB rule that deals directly with board cleanliness is IPC-5704. It covers cleanliness for unfilled printed circuit boards and steps to prevent or remove ionic contamination and other debris. Another rule, IPC-6012D, extends to PCBA and covers cleanliness and many other making steps. For many PCBA uses, these rules are enough. For medical boards the needs are higher. For those boards, cleanliness is critical. You must also show by tests that you removed enough contamination.
Standards and norms for PCB cleanliness in medical electronics
Two points have wide agreement in the field:
Post-assembly cleaning of boards is “essential” to make medical electronics work well and meet rules.
There is no single, direct, full standard that covers PCBA cleanliness for medical electronics.
PCBA tech moves fast. Boards are more complex and have more features. That makes it hard for regulators to write or update specific rules fast. So many rule updates focus on process and administration, not technical details. That leaves a gap: no single, targeted PCB cleanliness rule. Instead, people use other standards and tests as guides. Examples are ISO 10993, which covers biological tests and risk checks for biocompatibility, and IEC 60601, which gives test sets to check patient safety when using certain medical electronic devices. Many groups also list suggested cleaning methods. Below are common methods.
Ways to clean medical electronic PCBA
• Ultrasonic cleaners
So far, ultrasonic cleaning is the most recommended way to clean PCBA. The method uses controlled temperature and set time. Any method’s success depends on the cleaning solution used.
• Automated cleaners
Automated cleaning is usually a water-based process. Boards go into a basket, then into the solution, then dry. This works well. Be careful. Some solutions can harm some board materials.
• Manual cleaning
You can also use careful hand cleaning. For small boards with hard-to-reach areas this can be poor. But some parts must be cleaned by hand, for example microphones.
Choosing the best cleaning method is one of the most important steps in a good cleaning plan.
Steps for a PCB cleaning plan
Whether you or your contract manufacturer sets the plan, follow these steps for best results:
Identify likely soils or contaminants.
Check surface compatibility studies.
Choose the cleaning method.
Set temperature limits.
Set cleaning cycle times.
Choose rinse fluids.
Choose proper verification methods.
