T
Thukira
It depends on the notified body based on efforts involved; but it will not be as same as the first time; usually it will be considered as service request from you as customer to NB.
Hope it helps
Hope it helps
Determining Critical Components for conformity with IEC 60601-1
- Thread starter DENich
- Start date
In principle, if a Notified Body asks for anything in the context of MDD/CE audit, they should provided a reference for the requirement (e.g regulation, standard, clause etc.). The higher level regulations that apply to any certification body (including Notified Bodies) require them to use only requirements in publicly available standards or regulations. They can't just make up requirements. And, they cannot use guidance documents (guidance documents can help explain a requirement, but they should not effectively introduce a new requirement).
If you are however asking the agency for a formal "type test" (prepare an IEC 60601-1 report for voluntary basis or for a certificate), then the request for a critical component list is reasonable as they need this for the report, as Pads38 has mentioned.
However, even then the Notified Body's definition of a "critical component" is not practical. There are simply too many components to list.
In product safety testing (voluntary reports, CB certificates, NRTL), there has been a fairly long history of listing "critical components" more based on convention rather than a definition. For example, in a switching power supply convention would identify the isolation components (transformer, EMC Y1/Y2 caps over isolation barriers, optocouplers), fuses, the PCB material and that's pretty much it. However, in a switching power supply there are also many critical components associated with overcurrent and overvoltage protection which are not listed. Why? Just historical convention.
The convention varies a bit with different agencies and I guess everyone knows you can't list everything. So, it would be a case of roughly guessing what the agency wants and then waiting for feedback, i.e. they might say a particular cooling fan is critical so please indicate the manufacturer etc.
In some cases flexibility can be introduced by referring to critical characteristics rather than a full list manufacturer type, model etc. That gives the manufacturer the ability to change suppliers without needing to update the list. For example, I used to list mains wiring by stating the rated voltage, AWG, UL type (which infers single or double insulated), but leave the manufacturer/type as "any/any".
If you are however asking the agency for a formal "type test" (prepare an IEC 60601-1 report for voluntary basis or for a certificate), then the request for a critical component list is reasonable as they need this for the report, as Pads38 has mentioned.
However, even then the Notified Body's definition of a "critical component" is not practical. There are simply too many components to list.
In product safety testing (voluntary reports, CB certificates, NRTL), there has been a fairly long history of listing "critical components" more based on convention rather than a definition. For example, in a switching power supply convention would identify the isolation components (transformer, EMC Y1/Y2 caps over isolation barriers, optocouplers), fuses, the PCB material and that's pretty much it. However, in a switching power supply there are also many critical components associated with overcurrent and overvoltage protection which are not listed. Why? Just historical convention.
The convention varies a bit with different agencies and I guess everyone knows you can't list everything. So, it would be a case of roughly guessing what the agency wants and then waiting for feedback, i.e. they might say a particular cooling fan is critical so please indicate the manufacturer etc.
In some cases flexibility can be introduced by referring to critical characteristics rather than a full list manufacturer type, model etc. That gives the manufacturer the ability to change suppliers without needing to update the list. For example, I used to list mains wiring by stating the rated voltage, AWG, UL type (which infers single or double insulated), but leave the manufacturer/type as "any/any".
Hello Peter Selvey,
Thanks a lot for the detailed explanation. It looks very plausible.
So, to sum up, I can distinguish two critical components lists (ССL): "live" CCL and CCL "for a testing agency".
"Live" CCL is based on risk analysis and involves evaluating risks of appearance HAZAROUS SITATIONS i.e. if malfunction of a component can lead to electrical shock, fire, violation of EMI requirements or deviations from ESSENTIAL PERFORMANCE etc., so, this component should be recognized as Critical component. It's important to make your own "live" CCL to ensure your device is really safe and reliable.
CCL "for a testing agency" is a formalized table, which depends on a particular agency and is based rather on an established practice than on genuine risk analysis. It can be reasonable. CB test (at least ours) doesn't involve evaluation of a risk analysis file, therefore it's easier to use forms "to fill in" than try to evaluate reasonability of including each component to CCL and actually to accomplish risk analysis one more time.
So, an algorithm of creating CCL "for a testing agency" can be like this:
1. To accomplish risk analysis and create your own "live" CCL.
2. Basing on information from the Internet (special thanks to the members of this thread) about "typical" critical components create rough CCL "for a testing agency".
3. In cooperation with the particular test agency clarify CCL "for a testing agency"
I think, it's will be correct to use both CCLs for a production process.
Thanks a lot for the detailed explanation. It looks very plausible.
So, to sum up, I can distinguish two critical components lists (ССL): "live" CCL and CCL "for a testing agency".
"Live" CCL is based on risk analysis and involves evaluating risks of appearance HAZAROUS SITATIONS i.e. if malfunction of a component can lead to electrical shock, fire, violation of EMI requirements or deviations from ESSENTIAL PERFORMANCE etc., so, this component should be recognized as Critical component. It's important to make your own "live" CCL to ensure your device is really safe and reliable.
CCL "for a testing agency" is a formalized table, which depends on a particular agency and is based rather on an established practice than on genuine risk analysis. It can be reasonable. CB test (at least ours) doesn't involve evaluation of a risk analysis file, therefore it's easier to use forms "to fill in" than try to evaluate reasonability of including each component to CCL and actually to accomplish risk analysis one more time.
So, an algorithm of creating CCL "for a testing agency" can be like this:
1. To accomplish risk analysis and create your own "live" CCL.
2. Basing on information from the Internet (special thanks to the members of this thread) about "typical" critical components create rough CCL "for a testing agency".
3. In cooperation with the particular test agency clarify CCL "for a testing agency"
I think, it's will be correct to use both CCLs for a production process.
Personally I would be reluctant to make a big list based on risk, for a medical device, just about every component is "critical" in some sense. It needs some other criteria (filter) to figure out what is worth listing. Risk is in there but not the only factor. Otherwise the list would be endless.
If you are keen to make such a list, it's worth to explore a few examples to see why they are in or out of the list to develop some rules to keep the list manageable. For example, a CPU or microcontroller has 0.1uF caps near the power supply pins. If you don't use them (or, use the wrong type), the processor's function could become unreliable which could influence essential performance or software related risks controls. But most engineers would not list them as critical. Try to figure out why and make it a rule.
Personally, I would not make risk based critical components, the BOM works fine for the purpose (i.e. it has everything). Instead I would spend more time explaining the design for critical functions, especially where it is not obvious by inspection. For example how the circuit works, operating points, why certain parts were selected, software algorithm. That's more useful in the long run since it can help designers when the design needs to be updated, including for example, when parts have to be changed due to supply or other issues.
If you are keen to make such a list, it's worth to explore a few examples to see why they are in or out of the list to develop some rules to keep the list manageable. For example, a CPU or microcontroller has 0.1uF caps near the power supply pins. If you don't use them (or, use the wrong type), the processor's function could become unreliable which could influence essential performance or software related risks controls. But most engineers would not list them as critical. Try to figure out why and make it a rule.
Personally, I would not make risk based critical components, the BOM works fine for the purpose (i.e. it has everything). Instead I would spend more time explaining the design for critical functions, especially where it is not obvious by inspection. For example how the circuit works, operating points, why certain parts were selected, software algorithm. That's more useful in the long run since it can help designers when the design needs to be updated, including for example, when parts have to be changed due to supply or other issues.
I am reluctant to make a big list too. I have thought about choosing criteria too. It would be great to explore few examples, but I'm kind of a pioneer (the first explorer) on a field of 60601-1 certification in my firm and I have failed to find any relevant example in the Internet. So, a lot of mistakes are waiting for me before I will find out my own way to deal with 60601-1 certification.
As to 0.1uF capacitor, I think, it really depends on situation. Usually this capacitor has a big voltage overrating, it is mounted on a relatively lightweight PCB and vibrations or other mechanical causes of malfunctions are negligible low. In this case it is no need to list this capacitor in a CCL. But if, for example, capacitor is mounted on a PCB which is situated, let's say, on a vehicle, vibrations can cause a piezoelectric effect on thisc apacitor or even lead to a mechanical demolition of a MLCC structure. In this case, I believe, it will not bad to list this capacitor in a CCL and use here a soft-terminated type of capacitors.
Thanks for your ideas. It's hard to sort it out with standards on your own and that's why I'm here.
As to 0.1uF capacitor, I think, it really depends on situation. Usually this capacitor has a big voltage overrating, it is mounted on a relatively lightweight PCB and vibrations or other mechanical causes of malfunctions are negligible low. In this case it is no need to list this capacitor in a CCL. But if, for example, capacitor is mounted on a PCB which is situated, let's say, on a vehicle, vibrations can cause a piezoelectric effect on thisc apacitor or even lead to a mechanical demolition of a MLCC structure. In this case, I believe, it will not bad to list this capacitor in a CCL and use here a soft-terminated type of capacitors.
Thanks for your ideas. It's hard to sort it out with standards on your own and that's why I'm here.
Hello Al Rosen,
Thanks a lot for posting.
I would say, it is way too wide definition and, strictly speaking, it is not a definition at all. It is just a requirement, all definitions are given in paragraph 3 of the standard.
As was mentioned by Peter Selvey above, any component could be recognized as causing a HAZARDOUS SITUATION and if probability of appearing a malfunction is not taken in account CCL would include a whole BOM. Here RISK ANALYSIS should help, but, as different sources say (and not only from this thread), real CCLs which are demanded by testing houses are rather conventional tables, than based on RISK ANALYSIS.
Thanks a lot for posting.
I would say, it is way too wide definition and, strictly speaking, it is not a definition at all. It is just a requirement, all definitions are given in paragraph 3 of the standard.
As was mentioned by Peter Selvey above, any component could be recognized as causing a HAZARDOUS SITUATION and if probability of appearing a malfunction is not taken in account CCL would include a whole BOM. Here RISK ANALYSIS should help, but, as different sources say (and not only from this thread), real CCLs which are demanded by testing houses are rather conventional tables, than based on RISK ANALYSIS.
Do you want to satisfy the test lab's requirement or reduce your risk? If the latter, perform a FMECA to identify the critical components.
Thanks for the response.
Of course, I do want to satisfy both. We have already implemented a lot of principles of fault free and operator/patient-safe design during an engineering process. Methods like FMECA or traditional risk analysis can help with a methodology and a systematic approach. My point is, is it good or bad, that performing FMECA and receiving of CB test report are a bit different tasks, although they both should be done.
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