MicroAire Surgical Instruments: Fischer Core First Mate Last Break connectors ensure electrical safety, signal integrity and mechanical reliability

The Power-Assisted Liposuction (PAL) System from MicroAire Surgical Instruments uses Fischer Core low-voltage multipole connectors with a mixed configuration of power and data contacts, as well as a 12-feet silicone overmolded cable assembly resisting autoclave sterilization. For an additional layer of safety, the solution includes First Mate Last Break (FMLB) interconnects between the handheld device, console and pedal. How do these Fischer Core connectors ensure signal integrity, electrical safety and mechanical reliability for MicroAire’s surgical device, and for medical applications in general, in compliance with IEC 60601-1? What are the new FMLB connectors used for? And how did the Fischer Connectors team respond to the particular customization needs of the PAL System and other surgical and orthopedic tools designed by MicroAire?


Nick Sklavos, Staff Electrical Product Development Engineer at MicroAire, explains why the connector they were looking for must be, first and foremost, sealed and robust. “The device is used in surgical procedures and needs to be autoclaved. The handpiece must have a fully sealed and potted connector to prevent moisture and steam from penetrating through the PEEK insulating material inside the instrument. It must also have gold-plated contacts and be rust-proof.”


In other words: extremely robust and durable, both mechanically and in terms of design. The Fischer Core connectors in size 104 (15 mm diameter plug) used in the PAL System, as part of a 12-feet silicone overmolded cable assembly, are IP68 sealed and have a potted back, meaning the complete assembly is resistant to autoclave sterilization. Long lasting lifecycle of medical devices implies a high number of mating cycles and high resistance to corrosion. Fischer Core connectors have been designed to withstand 10,000 mating cycles and corrosion by undergoing 1,000 hours of salt mist (5% salt solution, 35 °C).


What also counts in the robustness and mechanical reliability equation is the pin size. Thick pins ensure that contacts can withstand the rigors of medical procedures and robust cleaning and scrubbing with brushes, as this surgical instrument tends to get contaminated with blood and fat during use. The PAL console is not in the area where surgery is happening. Located a few meters away, it does not need to be autoclaved, but people may try to scrub off the dirt. The connector has to be as robust as possible, because when blood or fat gets into it, people try to put instruments in and clean it up, and sometimes break it.


The size of the connector pin is therefore crucial, and thicker pins were preferred over smaller ones for better durability. The PAL System’s handpiece uses Fischer Core 104 A 130 connectors with 14 pins: 3 large 0.9 mm power contacts for a maximum current of 9.5 A, and 11 0.5 mm data contacts (incl. a longer contact for ground, see First Mate Last Break below) for 5 Gbit/s Ethernet. As for the 104 A 131 connectors used for the pedal connected to the console, they feature 12 power and data contacts of 0.5 mm (incl. the ground/FMLB longer contact) for 4.2 A and 5 Gbit/s Ethernet. On the console side, the pin size was enlarged from 0.5 to 0.7 mm for robustness.

Different keying and locking systems


The PAL System uses different robust keying and locking systems. Before MicroAire’s technical team opted for the Fischer Core Series, “users of the PAL System would try to plug the connector in different ways and break the pins,” explains Sklavos. “With the very robust keying provided by Fischer Connectors for our new unit, the plug can’t go inside any other way, only the right way.” The connector features an ultra-robust double keying system with two metal plates or arcs, one up and one down, which prevent users from forcing it in incorrectly and destroying the system.


The PAL System’s secure connections are made through two different locking systems, depending on whether they connect the handpiece or the console. “Our highly customizable Fischer Core product line is well-known for its versatility,” explains Ray Benson, Fischer Connectors Regional Sales Manager in charge of the customer project with MicroAire. “It offers not only a large variety of contact configurations, sizes and materials, but also different types of locking mechanisms: push-pull, tamperproof, quick-release and friction fit. The one chosen to meet MicroAire’s requirements for the PAL System’s handpiece is a push-pull.” The push-pull connector that goes into the handpiece remains securely in place once connected, preventing accidental disconnection or dislodging when the user shakes and holds the handpiece vertically during surgery or set-up. “It is both rugged and locked, and to unlock it, you have to make an effort,” Sklavos confirms.


As for the console, it uses a connector with a different mechanism – there’s in fact no ‘locking’ as such. Sklavos: “If the connector locks, people don’t know how to unlock it. They don’t know you have to pull on the shell and then on the connector. So people try and stress the cable to unplug it, and twist it sometimes hard to unlock it – and they damage it. If the console is locked, when someone pulls on the cable for whatever reason or a cart passes by and pulls it, they will pull the console too, which will fall to the floor.” Benson explains that to avoid this problem, “the connector on the side of the console doesn’t have a locking mechanism as such, it’s what we call a ‘friction fit’. If someone pulls on the cable, it will pop out.”


Smooth insertion and removal of the connectors, ease of use, and fast connection and disconnection were MicroAire’s explicit requirements from the outset. “The connector we got from Fischer Connectors is able to connect and disconnect quickly – especially for the handpiece. The connectors had to be easy to mount on the handpiece to ensure a user-friendly and secure connection. The surgeon or nurse brings the cable and simply plugs it in, then takes the other end and plugs it into the console. The feedback we’ve received so far has been excellent. Surgeons and nurses appreciate the robustness of the connectors, their ease of use, and the smoothness of the friction fit.”

First Mate Last Break


Like any other medical device manufacturer compliant with IEC 60601-1 (the series of technical standards for the safety and essential performance of medical electrical equipment published by the International Electrotechnical Commission), MicroAire had to meet stringent electrical safety requirements with the PAL System, as well as signal integrity reliability.


Hence the need to use Fischer Core First Mate Last Break (FMLB) connectors. “We want the ground of the cable to be always on,” explains Sklavos, “to mate first, so the system is within a ground presence all the time, and to break last, for signal integrity and electrical safety reasons. Without the presence of ground, we have floating signals which, from a signal integrity point of view, might cause numerous electrical artifacts that are impossible to predict (crosstalk, capacitive coupling, EMI problems, etc.), in addition to risky electrical safety conditions”.


With the longer pin of the Fischer Core connectors used in the PAL System (see red dot in image below), the ground path is established before any other power or signal connection. The longer contact of the handpiece cable plug (or pedal cable plug) mates first with the female contact of the console’s receptacles, and breaks last when unmating.

MicroAire’s PAL console positioned on an equipment cart features two receptacles mating first and breaking last with the handpiece cable plug’s longer pin. The console connector was changed with larger pins to accommodate breakage. The FMLB receptacle of the pedal control is installed between the two instrument receptacles.

Customization and responsiveness


Another reason MicroAire chose Fischer Connectors as its preferred connector supplier for its PAL System and other products is customization.


Sklavos: “The connectivity partner for medical device manufacturers must be open to customization, because medical regulations change a lot. And the company has to meet some clauses from the FDA.” One of these clauses is creepage. Creepage is a critical factor in the design of electrical and electronic equipment, as it affects the ability of the insulation to withstand high voltages and prevent arcing. Creepage distance requirements are specified in various safety standards, such as IEC 60950 and UL 60950. “With Fischer Connectors, we agreed to create a plastic border inside the connector,” details Sklavos. “So when the two mate, from either side, from the PAL console side and the handpiece side, this border protects the other shell (which is metal) from ESD zapping. A company must be able to make that, otherwise they won’t sell their connectors.”


Because customization was a crucial aspect of the design project, MicroAire’ technical team appreciated the way the Fischer Connectors team upgraded and sent product drawings in a timely manner. “We needed a custom First Mate Last Break connector with specific mechanical reliability and safety requirements, and the drawings kept coming in on time. That’s why we continue to work with Fischer, their connectors are everywhere in our products.”


MicroAire’s collaboration with Fischer Connectors extends beyond the PAL System and encompasses other products, such as orthopedic tools like drills, wire drivers and burs.

And what about Fischer Connectors’ competitors?

“For the new unit of our PAL System product, we contacted other companies that make connectors very similar to Fischer Connectors. First of all, some of them couldn’t meet our autoclave requirements. One company hadn’t done any autoclave testing, another claimed 100 autoclave cycles, which wasn’t enough. Another good connector manufacturer could meet both the creepage and autoclave requirements, but couldn’t deliver the connectors in time – their lead time was just terrible. What’s more, they couldn’t offer the customization that design engineers need when they’re developing something. Only Fischer Connectors could make the connection with the customization we needed. Fischer also had the assembly line we use anyway, and we had a good relationship with the Fischer technical team and sales manager, so we went with them.” – Nick Sklavos, Staff Electrical Product Development Engineer at MicroAire

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