In general, medical devices must meet higher safety and reliability standards than most other types of electronics because of their impact on users’ health and safety.
IP ratings (Ingress Protection) are crucial if devices are going to be used in an environment with limited control. Fans and enclosure openings are determining factors for the IP rating of a device. If there are any solid particle protection or liquid ingress requirements, fan selection and establishing opening sizes of your enclosure are critical.
Your thermal solution affects how large your enclosure openings will need to be which directly affects your IP rating. If you find that you need larger openings to enable enough heat transfer, finger guards may need to be designed in to maintain an IP rating of 2X.
For sensitive equipment or devices, a higher IP rating may be required, which would necessitate the use of filters to protect from dust. Filters directly impact flow resistance and pressure drop within an air cooled system and the fan must be chosen appropriately to function in those conditions.
For the even higher IP 6X ratings, which require a vacuum tight seal, the device will need to be fully within an enclosure, which might mean that the external surfaces will need to dissipate the heat. And, if those external surfaces are to exceed touch temperatures, protection should be provided to the end user from accidental contact. This level of rating would be preferred for more rugged applications, especially for devices that are going to be outside a medical facility, whether it be at home, out in the field, in emergency situations, etc.
Depending on the application, full waterproofing may or may not be a key concern, but in any case, liquid ingress due to cleaning and sterilization must be factored in. If a device is simply wiped down for cleaning, lower IP ratings would be acceptable. If there are full and extensive cleaning processes with powerful waterjets, any sort of openings devoted to heat transfer should be heavily scrutinized. If liquid is able to get into the device and the device requires an IP rating or X5 or above, some sort of waterproofed coating should be considered for the electronic devices. Conformal coatings, such as thermally conductive silicones or epoxies, can seal the electronics from liquid, but still enable heat transfer away from the device.
Additionally, take-home medical treatment devices should have a minimum IP rating of X4. Day-to-day activities, at home cleaning, and spills are all legitimate concerns. Material selection in critical in considering USP Class ratings (if the device is used in manufacturing any ingestible products, such as medicines, food ingredients, supplements etc.) or ISO 10993 for physical devices that will be implanted, mounted, or in contact with the patient in any way.
Plastics are a large concern in these two standards due to outgassing and potential chemical leeching. If part of your solution utilizes a thermally conductive plastic, the plastic’s properties in relation to biocompatibility must be determined prior to finalizing the product design.
Metals may also be an issue depending on the level of corrosion resistance as well as potential allergies patients may have to particular metals, especially nickel, which is a common plating for corrosion resistance. Certain types of surface treatments, such as hard anodize for aluminum products, clear coats for copper, or conformal coating for most other components can be potential resolutions that will still work in conjunction with your thermal solution.