We have all been in the doctor’s exam room and have probably looked at, or even played with equipment available in the room. Fortunately, in the operating room where the really important equipment is, they put you to sleep.
It is easy to see, however, that medical connectors and cables are special because:
- They must be goof-proof. Even the untrained casual user must not be able to damage the connectors or mating cables.
- The strain relief and locking mechanisms must not fail when someone trips over or runs over the cable.
- They must be sealed from exposure to moisture and other fluids.
- Anything in the operating room or similar environment needs to be autoclavable, surviving temperatures above 121°C for 20 minutes or cheap enough to be disposed after a single use.
In addition to these requirements, you will generally find that medical cables want to be very flexible. The key to flexibility is the use of small conductors using stranded wire and dielectric recipes optimized for flexibility. The best way to accomplish all of this is quite often the use of over-molded cables where the molded material provides the moisture seal and cable strain relief. This over-mold and related accessories can also provide for polarizing, positively preventing miss mating, and latching that ensures a water-tight seal where the connectors mate.
Some medical cables require extraordinary numbers of mating cycles. Consider the ultrasound machine where the operator changes the cable many times during the day. Medical connector manufacturers have developed specific mating contact systems designed to accommodate many mating cycles. These contact systems can also be designed to reduce mating forces so that medical personnel need not be Samson to get the connector together.
You will note a trend here. Medical equipment tends to consist of closed, sealed boxes that are only opened and serviced by trained factory technicians, perhaps with special tools. The user generally only plugs-in cables for power and signals. For this reason, a large healthy industry has developed around the capability of making sealed, high cycle life cables and mating connectors. Most designs are quite custom; providing the number of conductors needed for the application, and also providing the appearance and usability features that match the machine. Appearance and resistance to soiling and wear are very important.
Some systems like CAT scanners or operating robots are high-value, low-volume machines where the needed connectors are simply not available in the open market. For this reason, you will find a significant number of application specific, custom, single-source connectors in medical equipment. Typically, extensive testing is required to qualify interconnects like these. It is important to include any necessary qualification testing in your project plan.
Inside the boxes, you will generally find the same types of connectors commonly used in computing, instrumentation, and telecom platforms. You are also likely to find off-the-shelf computers, storage systems, and modems inside these boxes. Flex circuits are used extensively in medical applications, especially for connections to displays and touch pads on the outside of the machine. The flex approach allows the entire system to be sealed from moisture, and cleanable using harsh chemicals. Cooling systems for medical equipment frequently use conductive cooling to avoid having the openings that would be necessary for air to flow through the machine.
So, if your six-year old child can mate and unmate the connectors and you can hose down your equipment, you probably have a good solution for the medical market.