By Larry Boulden, Staff Editor
Return with us now to those glorious days of yesteryear, when most equipment companies like yours had a “Component Engineer” who could steer you to the right connectors and the best vendor for your application. Today, for the most part, those specialists are gone with the memories of a simpler era.
The bad news is that you’re likely to be more on your own than in those sunny old days. The good news is that the vendors are stepping up, bolstering their value-added capabilities, to make sure that the connectors you choose will meet spec and offer durable, reliable service.
When you set out to specify a connector, the vendor will ask you about ten different classes of operating parameters. These include reliability, contacts, voltage/current, space, number of connector mating cycles, ease of operation, termination method, cleaning/sterilization, disposability, and cost. These factors are summarized in the check-off box, Ten Factors in Connector Specification.
Most of these factors are straightforward. But some have an unsuspected complexity to them, according to Tom Kannally, Industry Manager —Medical at Hypertronics. He points out that a connector specified for a disposable component may still require a lifetime of many mating cycles, for example, so that the disposable component can be mated repeatedly to ensure proper functioning, alignment, and testing prior to its one use before it is discarded.
And even though one of the two mating contacts is disposable, with only a limited number of mating cycles required, the other side of the connector will remain in use through hundreds or thousands of disposable attachments to it, so it may have a cycle life of tens of thousands of matings.
Beyond these basic aspects of connector specification comes the world of “Value-Added,” in which the connector vendor seeks to add value to their service to your company. According to Kannally, one of the most frequently requested value-added benefits is a cable assembly added to a connector. In years past, equipment makers would often make their own cable assemblies.
Today, they are more likely to ask the connector vendor to handle that task.
Kannally notes that some users comment that they just want to buy a connector, and say, “we’ll handle the rest.” When he encounters this, Kannally asks, “Do they really want to get involved with all the complexities of cabling connectors?” Labor is costly, and it might be easier and less expensive to let the vendor do it and provide the complete interconnect solution.
Another common request is for electronic components to be incorporated with the connector, often included on a printed circuit board inside it. Again, these are tasks that could be done in-house, but it often makes sense to have the connector vendor supply the whole assembly.
Examples of connectors with components attached are often those in which the connector cable must identify itself to the medical equipment into which it is plugged. So, for example, if you plug Connector A into a socket, it identifies the connector and treats it differently than if you plugged Connector B into the same socket. When the contact is plugged in, the electronic components inside it tell the assembly, “I’m A, I’m not B.”
An alternative to this form of electronic identification is more traditional mechanical keying that allows connector A to plug into socket A but not socket B. This type of mechanical keying has been used for decades, but the electronic keying mentioned above is a more recent development.
Another development: when mechanical or electronic keying is specified, an increasing percentage of buyers may opt for a plan that keeps competitors from plugging in. They may say, “I don’t want to use a standard key. I want a proprietary interface so that my competitor can’t come up with a cable assembly that will plug into my connector, without talking to me first.”
Another area of sensitivity arises in connection with how the connector is cleaned. When specs are originally set, the equipment designer and connector vendor will agree on whether the connector environment is damp or dry, and if dampened, by what? Saline solution? Body fluids, or solvents? (Or perhaps all of the above?) They will understand the cleaning and sterilization arrangements as planned. But often the prescribed methods are not followed in practice. So when a connector fails in service, it’s important to see how it is really being cleaned in field conditions. An inexpensive connector can be damaged or destroyed by powerful solvents or sterilizing solutions in practice. And if this is happening, it may be easier to change a connector to a more resistant unit than to persuade onsite medical personnel not to use familiar, available cleaners or sterilizing solutions.
A similar situation can arise when equipment is used in ambulances or other emergency care solutions. Equipment and connectors that are adequate for normal service may be damaged or broken during emergency care, where space is limited and medical staff are working under trying and difficult conditions. If this happens, it may be easier to substitute more rugged components than to persuade users to operate the equipment gently.
10 factors in connector specification
Tom Kannally, Industry Manager-Medical, Hypertronics, has identified
these 10 basic points to consider when specifying connectors for Medical applications:
• Reliability of the connector system
- Mating cycle life
- Contact resistance
- Current carrying capability
- Insertion force
- Resistance to high shock and vibration
- Contact wiping action
- Number of circuits to be connected
- Current rating
- Mixed contact types (signals, power, fluids, fiber, etc)
- Between the contacts
- Between the contacts and the outside world
• Real Estate in the system for the connector
- How much volume is allotted for the connector in the system?
- Where the connector will be mounted? (back, front, inside, and so on.)
- Is the receptacle hard mounted to a panel, or on a cable?
• How often the connector must be mated?
- Per use
- Per day
- Over the lifetime of the product
• How easy is the connector to operate?
- Simplicity of mechanism (is it readily apparent?)
- Does the connector latch?
- Is a tool required?
- Amount of force needed
- Size (too large or too small to easily operate?)
• Connector termination method
- Board mount (pc board, flex circuit)
- Wire termination (crimp, solder, insulation displacement)
• Cleaning & Sterilization
- Wipe down (with what chemicals?)
- One time sterilization (EtO gas, Gamma irradiation, and so on.)
- Autoclaving (what autoclave cycle, how many times?)
- Will the connector be reused? (one side or both sides?)
- How many times will it be reused?
- If it’s a one-use product, what happens if the product is reused?
- Is a “use-limiter” necessary, or a good idea?
- Connector cost
- Interconnect system cost (connector, cable, integrated electronics, an so on.)
- Applied costs (initial cost, service costs over the lifetime of the system, plus warranty costs … cost of reliability?)
Vendor design & manufacturing capabilities
Most connector vendors are happy to discuss their design and manufacturing capabilities. The next few paragraphs provide that information for Hypertronics, which offers precision design and manufacturing of electronic interconnect systems. This firm offers a combination of engineering talent and in-house manufacturing capabilities, such as 3D solid modeling, rapid prototyping, high precision assembly and injection molding, and provides customers with quality product in quick turnaround.
Hypertronics uses a fully associative CAD/CAM 3D solid modeling software package that allows engineers to design quickly and spot any potential design issues immediately.
CNC Milling centers can configure and machine engineered plastics as well as all metals to complicated designs. They can supply custom connectors to full specification within days from design to application. Quantities range from one of a kind to complete systems.
Capabilities include the production of screw machine components using multi-axis CNC screw machines. This allows for short runs and quick prototyping, from design to production in-house in most cases in less than a week.
Efficient plastic injection molding machines that mold sophisticated engineered plastics such as LCP. Both thermoplastic and thermoset materials can be molded. Tooling capability ranges from prototype to fully hardened single and multicavity tools allowing for higher output to meet customer needs.
Electroforms provide miniature components
Medical product designers are often challenged to create miniature mechanical or structural parts out of metal. Especially for angioplasty, catheterization, and microsurgical equipment, where the required parts are simply too small to machine or form mechanically. One proven solution uses metal electroforms. Made of metal formed electrochemically on a sacrificial mandrel, electroforms can be made as small as 0.024 in. long, 0.018 in. in diameter, and walls as thin as 0.0003 in., with absolute control over the internal profile. To some extent, the wall thickness can be varied over the length of the part.
Medical applications have included bellows-type dynamic seals, flexible EMI shields, flexible shaft couplings, “soft” self-centering electrical contacts for micro circuitry, and a host of structural parts.
One recent application is as an autoclaveable flexible seal for pushbutton switches on a surgical hand piece. In such relatively large-scale applications, one-piece electroforms replace stampings, machined parts, complex assemblies, or brazements and weldments. Metal electroforms have also played an important role in prototyping because of their quick availability and relatively low cost in small quantities.
Fischer Connectors S.A.
Filed Under: Connectors (electrical) • crimp technologies