As with all custom membrane switches, medical device design is driven by the specific needs of your application. Because human life is often at stake, these devices tend to have a commonality in stringent regulation and inspection requirements.
The general lighting and electrical function requirements are usually similar to non-medical, simply because feedback whether from the keys, LEDs, or your connected LCD still operates within the same narrow range in which the human hand, eyes, and mind work best with an interface.
Having said that, medical devices are more likely to have unique requirements than any other industry, with the possible exception of aerospace: again, people’s lives hanging in the balance makes successful function even more essential than, say a microwave or an ice cream dispenser.
More considerations
Another common issue is ESD or EMI resistance. Preventing shorts from electro-static discharge can be as simple as adding an extra ground circuit, or as complex as needing a separate ESD layer with a specialized configuration to protect the device.
EMI shielding, on the other hand, is usually a known formula derived from the strength of the power supply, and distance to the membrane switch circuits. This can necessitate specialized designs, but most often with EMI we just need to calculate how much overkill is required to be sure.
As with all membrane switches, because they are custom, we provide the first article for you to test electrical function, NEMA-4 / IP6x rating, ESD, and EMI resistance. As a follow-up, you will learn about UL746C and also UL F1 rating standards for silicone rubber keypad manufacturing in the next article.
