How do you determine critical components?
Authors:
Erica Sundgren, QA/RA Consultant MedTech, Orderly People
Alfred Samuelsson, Co-founder and CEO, Certainli
In our first article, we established what a critical component is from a compliance point of view and why the critical component list (CCL) matters for your Technical File. But knowing what a critical component is and knowing how to determine criticality are two different things.
This is where many electronics teams run into trouble. The process gets delegated to one person, handled too late in the design phase, or treated as a checkbox exercise rather than a structured risk activity.
Determining criticality isn’t guesswork. It requires the right competencies in the room, a shared starting point in your BOM or block diagram, and a structured line of questioning – not unlike the risk management techniques you already apply elsewhere in your development process.
Faktaruta/segement: This article series is relevant to anyone involved in development or lifecycle maintenance of electronics – from circuit designers and test engineers to product owners, sourcing professionals, quality managers and persons responsible for regulatory compliance.
How to determine criticality in electronic components
If you’re bringing an electronic product to market, it’s crucial to determine the right criticalcomponents early in the design phase. However, many still treat it as an afterthought.
Determining critical components requires the same structured thinking you apply in other risk management activities. That means bringing the right competencies into the discussion:
Design engineers who understand the system architecture
Electronics specialists who know component behaviour
Someone responsible for risk management who keeps focus on hazardous outcomes
Use the current version of your BOM, and/or at least a block diagram of your product to have a common starting point for your discussions. The following recommended steps are very similar to the risk management technique FMEA, and the group should work together to answer these three key questions:
In what ways can this component fail?
For each failure mode, what effects/consequences can that have for the product?
For each effect on the product, what hazards or hazardous situations can that lead to?
Since we are only focused on one component at a time and not multiple potential hazardous situations, these questions help the discussion become less abstract and more factual for the participants. To go from effects on the product to hazards and hazardous situations affecting users or patients can still be difficult. This step can be made easier by asking:
“If this component fails, could it lead to…”
An electrical hazard?
A mechanical hazard?
A thermal or fire risk?
A software-related safety issue?
Incorrect or misleading information to the user?
These questions help shift the discussion from “important for performance” to “important for safety.” The above list is only some examples of hazards, other types of hazards may be relevant for your product.
Common examples of components that often become critical include:
Power supplies
Power cords
Fuses
Wiring
Insulation systems
Fire enclosures
But these are patterns – not rules. Your design determines what is critical.
Start early, iterate as your design evolves
As mentioned in our first article, it is of great importance to start early. Although you may only have a first incomplete version of your BOM, it is still helpful to start identifying criticalcomponents within your design to make sure those components fulfil applicable requirements, are tested and have the required certificates.
If it turns out they don’t and you’ve started early, you may still have time to replace them or make sure that the required testing is performed. As your design and BOM develop, the identification of critical components will be iterated. In many cases, you will only need to review the new components that have been introduced, or revisit existing ones if their role or impact within the design has changed.
Let’s clarify with some examples.
Take a standard ceramic capacitor. Whether it belongs on your CCL depends entirely on what it does in the circuit.
Scenario 1: Y-cap across the isolation barrier (Class II mains product) Bridges primary and secondary to suppress common-mode noise. A short across this cap bridges mains to the user-accessible side. Hazard: electric shock. Critical: yes. Must be a safety-approved Y1/Y2 cap per IEC 60384-14, with a certificate from a recognised body.
Scenario 2: MCU decoupling cap (battery-powered SELV device) Sits on the 3.3 V rail next to a microcontroller. A short loads the rail and the device resets. Hazard: none. Critical: no. Ordinary BOM line.
Same component family, two different roles. Criticality follows function, not the part number. Scenario 1 is critical because energy can reach the user. Even a standard capacitor can thus become a critical component. Inversely, a typically critical component such as a safety relay might not be critical if not used as a safety function, but rather as a switch for something harmless. Document the reasoning behind the decision, not just the conclusion: when an auditor pushes back, that is what you defend. It can be equally important to document your reasoning for internal purposes, so that the CCL can be updated at a later stage in the product life cycle, especially if the people involved in the project have changed.
Thank you for reading the second article in our critical components series – we hope it provided useful clarity and insights. In the next article, we’ll take a closer look at documentation. Besides documenting the determination work, which helps you argue for your reasoning and conclusion when an auditor or test house thinks differently, what else needs to be documented for each critical component in the CCL? After summer, we will answer that question for you.
Until then, do you have any questions about what you read today? Or suggestions for future topics? We’d be happy to hear from you. Feel free to reach out at hello@certainli.se and info@orderlypeople.se or connect with us on LinkedIn.
This article was co-authored with Certainli, an AI-powered platform that transforms manual component compliance processes into automated workflows, delivering auditable proof for complete regulatory confidence – whilst securing a faster time to market.
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Keywords: Critical components, critical component list, CCL, BOM compliance, component compliance, electronics compliance, IEC 60384-14, FMEA, risk management, safety-approved components, medical device compliance, product certification, design engineers, hazard analysis, failure mode