Mass Customization in Electrical Connector Design

By: Dennis Johnson

However, through mass customization connector production techniques, designers can meet stringent cost, reliability, and time-to-market requirements common to medical device OEMs. Because these connectors are custom built, they are never out of stock nor discontinued. And as designs are upgraded, the components, ICs, and pin-outs can be quickly added or reconfigured as needed. Custom on-demand medical connectors can be built to exact feature specifications. They are easily modified and often cost less than off-the-shelf alternatives.

 

The worst feature of mass production is its resistance to innovation. Large capitalization in tooling and training make changes prohibitively expensive. The assembly line must be shut down. The large inventories of parts from suppliers become waste, and these suppliers must also shut down, retool, and validate for manufacturability.

 

Mass customization is a direct result of information technology and robotic advances. It enables the production of goods to individual demands with mass-production efficiency. Mass customization as a manufacturing model has the advantages of cost reduction over conventional methods, but it also promotes design flexibility and enables limited inventories.

 

A primary goal of mass customization is to eliminate waste by inventory control techniques such as just-in-time (JIT) production and Six Sigma quality assurance feedback. JIT production attempts to maintain the smallest inventory possible: parts arrive just in time to be assembled in-product.

 

JIT relies on the capability of the OEM to describe the fabrication of a part by solid modeling and other digital file platforms. Because these parts are custom and stored in software, they are never out of stock or discontinued. Innovation can happen as quickly as information can reach the part manufacturer. This provides more flexibility to the market, and it reduces waste, defects, and obsolescence.

 

Mass customization in medical connector manufacturing enables flexibility and responsiveness, which can eliminate defects and shorten time to market. Waste is limited by fully leveraging lean inventory control procedures.

 

The manufacture of personal computers (PC) provides an example of mass customization that can be extrapolated to medical device electronics. This is particularly true for connector manufacturing in facilitating rapid PC advances.

 

PC customization is accomplished by the modularity of firmware and hardware. Connectors on the motherboard accommodate hardware modules such as processors, random access memory (RAM), expansion cards, and peripheral devices. Firmware resides in flash memory and can be modified or updated to enable new hardware module installations.

 

The total permutation of custom PCs is enormous. Each PC satisfies the demands selected from a multitude of options. PCs accomplish mass customization using standard connectors with fixed pin-outs.

 

Customized connectors can be used similarly in medical devices to provide mass customization for medical electronics. Custom connectors can be built with as high a pin count as is required, at any pitch (distance between pins). Platforms can be made from any engineered plastics, ceramics, or ferrite. They can accommodate almost any shape or size and can be reconfigured quickly as design changes and requirements mandate.

 

Using compliant pin connector technology can increase the ­reconfiguration flexibility of medical devices. Compliant pin connectors can plug directly into the plated through-holes of any printed circuit board (PCB). This greatly simplifies socketing, which becomes part of the PCB and can be added at minimal cost. The engineer of the medical device board can bring any trace signal that might be used in a future connector over to an array of plated through-holes. When a modification is needed, a connector can be built to this trace. All customized connectors are reliable and delivered with zero defects, which is an essential requirement for medical electronic devices.

 

Connectors are a critical component of any medical electrical system. Often they are attached to flexible cables—some are fixed during the life of the product, but many must provide portability and interchangeability by allowing removal and reconnection.

Adding components to a custom connector can expand the function of a medical device. Adding these components is certainly a less expensive option than redesigning the main board. In addition, connectors for medical devices often require modification. High reliability can best be maintained if the original connector manufacturer accomplishes the modification and quality assurance.

 

Designers of medical devices need to anticipate modifications of their own systems and often those of any third-party embedded components. Engineering a medical device to work with a variety of connectors can extend its useful life by leveraging mass customization techniques.

 

A medical device board can be engineered to accommodate mass customization connector flexibility. The engineer needs to examine the medical device’s system requirements and determine any area that might require future updating. By running a trace from an appropriate pin or trace signal in that area, the medical device board is engineered for mass customization.

For example, the OEM may want a flashing light and audible alarm to alert a technician when a particular signal is not presented to a certain medical device. If this signal is brought out to a plated through-hole on the medical device’s main PCB, then the audible alarm, LED, and any driving circuit can be built into a custom connector. Using mass customization, this becomes an incremental change to the original main PCB that does not alter the price or the time-to-market schedule.

 

Medical electronic devices are becoming smaller, more sophisticated, and portable as they move into doctors' offices, medical centers, and patients' homes. Many devices are attached to or implanted in patients, and as such, demand high reliability.

But as these devices shrink, they also become more complex, and connectors must do the same. Often, ICs, capacitors, or personality resistors are designed into the connector itself to accomplish signal interfacing and other functions. Such active connectors are rapidly becoming common, but they are often an afterthought to the design.

 

The development of capable and low-power microcontrollers, as well as analog and digital ICs with small footprints, have enabled the design and fabrication of complex active circuits close to connector pins, right on the connector. There are many possibilities for using these active connectors for mass customization. Microcontrollers are used for function control, safety, use limiting, and data collection on surgical hand pieces and devices.

 

Connector pin-outs can be reconfigured, signals can be modified and monitored, and firmware can be modified or expanded. For example, a low-end surgical device microcontroller will have 1000 bytes of ROM and 20 bytes of RAM on one chip and cost pennies. In comparison, Microsoft Word requires more than 30 MB of RAM and a processor that can run millions of instructions per second.

 

After a device is manufactured and an improvement or function change is required, units can be reworked simply by reprogramming the microprocessor and reading new code onto designated connector pins. The medical device’s functions can be modified or others can be added without rebuilding the medical device’s main board. 

 

Active connectors are particularly suited for engineering medical devices. Original biomedical signals are often low level and low frequency. For example, EKG signals are measured in millivolts and EEG in microvolts. Such signals are subject to interference—­especially from 60-Hz power. Active connectors can ensure the integrity of these signals.

 

Active connectors can be fabricated with a ground trace around low-level pins to protect against cross talk. Placing operational amps near these pins can boost the signal level to compete with interference. The boosted signal is passed on as single-ended or balanced analog, or it can be digitized with an onboard AD convertor. Microcontrollers among the pins can direct analog signals to convertors or multiplex them in any manner. The same controller, under software control, can reconfigure the active connector’s pin-out.

 

An active medical connector can accomplish a small fix or become a major player in a system. Small modifications built into a connector can alleviate the need to redesign and remanufacture the main PCB. Connectors can be designed and mass customization manufactured with terminating resistors or with decoupling capacitors embedded.

 

By bringing a signal trace to a plated through-hole in a connector area, the engineering designer can prepare for many contingencies. For example, a third-party device may introduce unexpected transients to the board’s power. A fix could be a connector with decoupling capacitors added. If the third-party device does not terminate the signals, terminating resistors can be added to the connector.

 

Suppose that a third-party device has termination resistors but another’s does not. To solve this problem, two types of connectors are built—one with and the other without termination resistors. Neither connector is considered a special part. In mass customization no part is considered special and lot sizes do not matter. Either connector can be ordered at any time and will never become obsolete because the designs are stored in software. 

 

Rapid advances in technology can often leave a trail of obsolescence. Redesigning and testing a new design to stay on the cutting edge can be expensive. Active connectors can be plug-in modules that modify or update a connector function. Designing a PCB around modular functions that can be implemented by plug-ins gives the PCB a range of options.

 

A plug-in is essentially a PCB connector that also has compliant pins. It can be press-fit into the medical device’s main PCB anywhere plated through-holes are available to socket its pins. Therefore, customizing the plug-ins also customizes the main PCB. Plug-ins are just extensions of the PCB, electrically speaking. Plug-ins can accommodate signals from 0 dc to 10 GHz. The low resistance (<10 mΩ) and inductance (<1 nH) of the pins, as well as the adjacent pin capacitance (<1 pF), are negligible in most PCB designs.

 

If the board and plug-ins have passed quality assurance checks, there is no need to retest the final assembled board. Because soldering is not used, there are no possibilities of bridges or cold solder joints. For the same reason, plug-ins can be swapped in the field to repair, modify, or update boards without special tools.

 

Once SPICE (i.e., simulation program with integrated circuit emphasis) is run on a plug-in, it becomes a hierarchical SPICE block and can be quickly integrated into the simulation of any medical device PCB. SPICE is a general-purpose, open-source analog electronic circuit simulator program that is used in IC and board-level design to check the integrity of circuit design and to predict the circuit behavior. Software circuit design tools can capture the schematic of the plug-in, apply SPICE to its circuits, and produce a bill of materials (BOMs). BOMs can be checked against the assembly supplier, connector manufacturer, and component inventories. Availability, cost, and lead time can be immediately reported to the design engineer. Any necessary substitutes can quickly be evaluated.

 

As soon as a design is accepted, a purchase order for parts can be issued electronically. PCB layout and other CAD files are shared with the custom connector manufacturer and other component and assembly suppliers. This is the essence of mass customization.

 

By using custom plug-ins and other custom connector technology, the design life of the PCB is extended. It can be updated by designing new plug-ins. Inventory can be reduced because the OEM only has to manufacture and store basic boards. Functionality can be added or updated by connecting plug-ins or other custom connectors before shipping.

 

Mass customization and JIT are business models for lean supply-chain management, which emphasizes limiting time, material, and capital waste. Using custom connector and plug-ins offers possibilities to implement this model.

 

Used within the proper model, mass customization can also be environmentally friendly. Because parts are made only when they are needed, it eliminates the amount of hazardous materials used. The parts are able to demonstrate a low carbon footprint because a part that is not made equals energy that is not used and carbon that is not burned. The process can help products achieve RoHS compliance for global distribution.

 

Not only is the connector the most critical electronic component, it is often the last opportunity to introduce a modification, to modify an interface, to alter the signals, or to introduce visual or audio devices. All such customizations are critical in medical instruments, but traditionally have been fraught with production barriers and high cost. Mass customization techniques enable the quick and effective creation of medical connectors.

 

Time to market, device features, and cost requirements can be efficiently met by implementing mass customization techniques whenever possible in manufacturing procedures. Costs are comparable to mass production, and design flexibility is unmatched by other manufacturing methods.

 

Mass customization for medical connectors provides a useful alternative to achieving the necessary quality and design flexibility. This ultimately helps device OEMs to stay competitive and ­profitable.