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Automated Fine Wire Termination Simplifies Complex Medical Connector Assembly

Automated Fine Wire Termination Simplifies Complex Medical Connector Assembly

Removing the human element from the process of cable-to-connector assembly for medical devices by the use of robotic automation improves reliability and reduces production cost.

Dennis Johnson

Removing the human element from the process of cable-to-connector assembly for medical devices by the use of robotic automation improves reliability and reduces production cost. Miniature assemblies, previously thought to be impossible to manufacture, can now be introduced into connector designs using wire gauges as small as 56AWG. Robotic automation even solves problems with higher conductor counts and exotic wire alloys.

Hand-assembly of medical connector assemblies introduces many variables into the process, including the need for extra testing, inspections, and frequent rework. Robotic automation virtually eliminates these costs from the manufacturing process. Production of medical cable-to-connector assembly costs can be reduced up to 50% over manual procedures. As an example, a typical 34-pin medical connector taking up to 45 minutes to manually assemble can be assembled in four minutes using robotic automation technology, with greater reliability, improved yields, and enhanced quality control.

Automated Rapid Wire Termination Technology

Automated rapid wire termination technology is an automated process whereby wires from one area of a PCB are soldered to another or to the pins of a connector.

While technicians can manually solder wires as small as 40 gauge to connector pins with the help of microscopes and other precision tools, the need for greater miniaturization, reliability, and reduced production cost has driven the need and refinement of automated rapid fine-wire termination technology. An added benefit is that rapid wire termination can allow for greater sophistication in medical device probes.

Automated rapid fine-wire termination permits wires as fine as 56 AWG to be reliably soldered in a fraction of the time and cost of manual soldering, eliminating cold solder joints, burnt insulation, and greatly reducing overall manufacturing time. It’s a versatile procedure that can connect any size wires from 20 gauge to 50 gauge in any pattern; for example, a bundle of 120 40-gauge wires can be connected to a solder ball array in less than a square centimeter. The manufacturing quality control process is reduced to spot-checking; a skilled operator need only check the process periodically, and the automation engineering staff can address problems immediately should the need arise.

Rapid wire termination is an extension of printed circuit fabrication automation. Many wires are separated and cut to a precise length and stripped so that they meet a solder ball lattice produced on a surface mount board. Alternately, the stripped wires can be pushed through plated-through holes and reflow-soldered. The stripped wires can also be inserted into copper beryllium female contacts and press-fitted into plated-through holes. This method can be done automatically or manually in the field without special tools, and can also be used to make transitions to wires that are dissimilar to copper wires.

Close-up of Onanon 42-AWG wire termination.

Rapid wire termination blocks can be combined with compliant pin technology. Compliant pins insert in plated-through holes with significantly improved characteristics over the usual “eye-of-the needle” pins because compliant pins are designed to fit into plated-through holes and to exert spring-like action in all directions. This evenly applied force eliminates scraping of plating that can create debris, leaving a clean and secure but removable connection.

Combining compliant pin, rapid wire termination technologies, and the ability to add components to the connector substrates can offer many advantages. A board-to-board flexible cable can be implemented, and because the female receptacle is just an array of plated-through-holes, the cable can have embedded components to adapt it to different boards. Modifications can be added to update or fix board functions, eliminating redesign time and the cost of manufacturing new boards. An updated cable can be installed in the field to bring the system up to date.

A simple passive component jumper on a connector can enable power or indicate to another piece of equipment that it is ready to function. For example, automated rapid wire termination technology can be used for the placement of personality resistors on the same platform as the rapid fine-wire termination block so that the interfaced equipment can differentiate between cable assemblies. The resistors indicate to another circuit the characteristics or personality of the equipment it is interfacing. Cable assemblies, differing only in their passive components, can thus be used with different interface equipment, providing increased flexibility, and reducing costs. Active, embedded-on-the-connector components could include op-amps, a/d converters, or even multiplexers so that the digital signals can be fed out to fewer pins.

Using automated rapid wire termination technology, future medical electronics instruments could have intelligence built into their connectors. System upgrades, as one example, could be introduced through drop-in replaceable connectors. The potential combination of different wire sizes, embedded electronic components, and soldered or solderless terminations in a single connector gives medical device OEMs the ability to embed value-added, intelligent, microscale systems into their cable designs, by way of the enhanced capabilities that can be introduced from the connectors themselves.

As a more specific example, consider medical device probes that carry radiofrequency electrical energy at 1000 VAC used to ablate tissue. Assembly of this type of probe can require the welding of beryllium copper wires to tungsten wires, because tungsten wires are needed to withstand the heat generated at the probe’s tip. Making the transition from beryllium copper to tungsten on a rapid wire termination block allows for low-resistance connections to be made by way of beryllium copper pins that are inserted in to plated-through holes. The spring-action and low electrical resistance pins ensures a tight fit and the ability to carry the 5 amps needed for this type of probe.

Perhaps the main benefit of rapid wire termination is the making of connections in probes or cables by reliable procedures that are automatic and repeatable. Because the fabrication procedure is not labor intensive, production costs are greatly reduced. Low-cost probes are disposable; upgrading a system can be done as easily as replacing the probes or cables. Changing the probe can be as simple as changing the processors algorithm stored in its PROM or changing a few components. Often a system can be upgraded in this manner without a complete FDA review. It may only require a letter-to-file documenting the upgrade.

Eliminating the Inconsistencies of Hand-Assembly

Today, 90% of all wire terminations are done manually to a solder cup pin, rigid printed circuit board (PCB), or flex PCB. Terminating wires manually to solder cup pins or pads is very labor intensive, and the manual solder processing creates numerous quality, cost, and delivery variables, not to mention design limitations.

Soldering very-fine-gauge wire to standard pinned receptacles also presents a burn risk to technicians when constructing cable assemblies. An automated rapid fine-wire termination block can be designed to eliminate such safety concerns and increase throughput by greatly cutting soldering time.

37-pin, 44-AWG wires connector terminated in 4 minutes.

Automated rapid fine-wire termination permits smaller wires to be reliably soldered in a fraction of the time and cost of manual soldering. Rapid wire termination can be an automated process, which reduces soldering time, eliminates cold solder joints, and burnt insulation, and greatly reduces process time. Production of medical cable-to-connector assembly costs can be reduced up to 50% over manual procedures. As an example, a typical 34-pin medical connector taking up to 45 minutes to manually assemble can be assembled in as little as four minutes using robotic automation technology.

Many requirements of the soldering process can be eliminated completely. Each automated rapid fine-wire connection is reproducible. A common manual process quality control issue appears in the manual soldering process—the required heating of the pins to a specific temperature so that the solder joint is not left cold. That process can easily damage wire insulation. Rapid fine-wire termination solves this problem because it uses reflow solder technology that applies heat quickly to small point.

Automated Fine Wire Termination Helps Medical Device OEMs Control Costs

The recent reaffirmation of the Affordable Care Act and subsequent reimbursement pushback from healthcare providers and the government are causing medical device OEMs to emphasize the control of manufacturing costs in any way they can. Raw materials cost are the same around the globe, and so the only meaningful way to gain a competitive advantage is by having a way to reduce assembly cost. Some Medical device OEMs are turning to lower-labor countries, such as China and India, for their device manufacturing. However, this strategy introduces uncertainty, variables in quality, and a loss of IP control. In addition, regulations in the Dodd-Frank Act have tightened requirements with respect to the traceability of precious metals; all publicly traded U.S. companies are required to have traceability to the source of the raw materials in their assemblies. The use of robotic, automated fine wire termination in the manufacturing process ensures that OEMs are operating by means of a very cost-effective process, mitigating the need to look overseas for cost savings.

44-AWG wires reliably soldered to IPC CLASS-III assembly.

Removing the human element from the process of cable-to-connector assembly for medical devices by the use of robotic automation improves reliability and reduces production cost. Miniature assemblies, previously thought to be impossible to manufacture, can now be introduced into connector designs. Automated rapid fine-wire termination can even be used to solve problems with higher conductor counts and exotic wire alloys; and perhaps most importantly, the variables introduced by the manual, hand-assembly process are eliminated, resulting in greater reliability, improved yields, and enhanced quality control.

Don't miss the MD&M Philadelphia conference and expo, October 7–8, 2015.

Dennis Johnson is president and CEO of Onanon Inc. (Milpitas, CA). Reach him at dennis@onanon.com.

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