Editor's Choice

What makes good connector design?

25 November 2020 Editor's Choice Interconnection

Whether they’re used in a commercial aircraft, on a military vehicle or a medical ventilator, very few components are subjected to extreme conditions in the same way as connectors. Here, Ammar Lokhandwalla, customer application engineer at connector specialist PEI-Genesis, explains what makes a good connector design.

According to a 1986 essay by Dr Fred E.H. Schroeder, “The electrical appliance plug is something that Thomas Edison did not invent. It was a curious oversight, because Edison anticipated almost everything that might relate to the incandescent light bulb and its applications.”

You see, the concept of an ‘appliance’ or something that could be readily plugged into a wall outlet didn’t come around until the twentieth century, around two decades after the popularisation of the light bulb. The initial popularity of electric lighting was based on the assumption that these devices would be permanently wired into the house.

Today, engineers across the world consider the complete lifecycle of every component from cradle to grave. A modern A380 aircraft, for example, is made up of some four million individual parts produced by 1500 companies from 30 countries around the world.

Connectors, and more specifically those used in aviation and military applications, must endure extreme conditions. Whether it’s the rapid temperature fluctuations and changes in humidity, to persistent vibration, impacts and signal interference, these cables must operate reliably to ensure their users can get the job done.

Take the industry-standard D38999, for example. This is a military-specification connector that was originally designed in the 1970s and is now on its third-generation design. Like other connectors of its kind, it’s made up of a few basic components: a hard outer shell, a neoprene rubber insert with holes to house the pins, or contacts, and sometimes a backshell on the outer housing that provides additional shielding and durability.

Material choice

When selecting a connector, engineers must consider a wide variety of properties depending on their application. One of the primary considerations is the choice of materials, for both the electrical terminations and shell housing. For example, although copper offers better electrical and thermal conductivity, aluminium is cheaper and easier to form and plate.

So, while copper may be chosen for high-voltage industrial applications where heat dissipation and conductivity are vital, aluminium may better serve aerospace and military applications where weight and corrosion resistance are more important.

Water barrier

Ingress protection is another consideration. Connectors designed for industrial food and beverage manufacturing must be sealed against water jets to allow equipment and machinery to be washed down between shifts.

This protection extends to marine applications such as those in the oil and gas sector, where equipment may need to be fully submersible for prolonged periods of time. In these applications, it may be necessary to select a polycarbonate connector, with the right O-rings and grommets to provide a moisture seal.


While aluminium is the preferred choice of connector material for many construction, rail, industrial and military applications, it may still need to undergo plating to improve its corrosion resistance, to provide further electromagnetic shielding, and to meet camouflage and colour needs.

For example, some military applications use olive-drab green, a colour that was historically achieved with a toxic cadmium coating. In recent years, this has been replaced with a black zinc nickel plating that meets RoHS and REACH regulations. If engineered correctly, this black plating can deliver the same performance as cadmium coatings and withstand over 500 hours of salt spray.

Soldering vs crimping

Many people may not be aware, but not all connector contacts can be solder-terminated. Under certain extreme conditions, the operating temperature of the application can exceed the melting point of the solder, causing connection failure. For applications where this is a risk, engineers may prefer to specify a crimped connector.

With crimping, contacts are joined to the wire by mechanically squeezing them together to ensure that they remain in contact no matter the temperature. Instead of a soldered connection where the wire is fed through an eyelet or hook and then soldered, crimping involves material being deformed to lock the termination together using a special crimping tool.

Design early, design once

One of the biggest mistakes I see manufacturers make is considering connector design too late in the design process of their product. This often means that a product’s time to market is delayed while the design is reworked.

It’s important to remember that your connector may have physical design constraints like a minimum wire gauge or number of contacts, so it’s vital to consult with your connector supplier early in the process. At PEI-Genesis, we’ve made this problem easy for our customers by offering them a 3D wire model of the connector that customers can drop into their design to see if it fits.

If it doesn’t, our engineering team can help refine or redesign the existing design, or propose a different connector entirely, that meets the specification. This includes changing features like threaded, bayonet and friction fittings, or accessories like backshells, or something simple like a dust cap.

So, while Edison might have made a curious oversight by not inventing the electrical plug, luckily manufacturers don’t have to make the same oversight today by considering the factors that make good connector design.


Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

What is device management and why should you care?
25 November 2020, Trinity IoT , Editor's Choice, Telecoms, Datacoms, Wireless, IoT
When device management is implemented alongside a centralised interface, companies can update firmware or software, without the need to manually perform each update in the field.

The A to Z of A2B applications
25 November 2020, Altron Arrow , Editor's Choice, Telecoms, Datacoms, Wireless, IoT
An A2B device’s support for up to 32 channels of downstream audio and upstream audio on the network facilitate the distribution of multiple channels of different audio content within a single system.

Personality profile: Dereck Styane
25 November 2020, Phoenix Contact , Editor's Choice, News
“We do try and develop people and promote them from within the company, so I savour people’s personal growth that I’ve overseen.”

Products of the Year 2020
25 November 2020 , Editor's Choice, News
A selection of some of the best products to hit the South African electronic engineering market this year.

Why you don’t take ‘touch’ for granted
30 September 2020 , Editor's Choice
The key criteria for choosing the right sensor control IC          Touch has become an incredibly intuitive way for people to interact with high-tech devices. In just a few short years after the first ...

Ask your PCB supplier about reliability, not just capability
28 October 2020, Elmatica , Editor's Choice, Manufacturing / Production Technology, Hardware & Services
Make sure to discuss combinations and how your solution affects risk of failure with the multiple heat cycles required to assemble the product, and the risk of failure in the final application.

How you can help your EMS partner
28 October 2020, Jemstech , Editor's Choice, Manufacturing / Production Technology, Hardware & Services
If you want a good quality, reasonably priced product in a quick turnaround time, always communicate your assembly requirements effectively with your EMS partner.

Practical experience with PCB robotic soldering processes
28 October 2020 , Editor's Choice, Manufacturing / Production Technology, Hardware & Services
Over the past few years there has been a lot of discussion over the need for higher temperature materials and expanding the use and knowledge of high temperature assembly techniques.

TRX welcomes Hannes Taute as new MD
28 October 2020, TRX Electronics , Editor's Choice, News
We delve into his background, what his plans for TRX Electronics are, and how he envisions what the future of the local electronics industry will look like.

Personality profile: Hosia Matlou
28 October 2020 , Editor's Choice
“To make a success in the very niche electronics manufacturing market, I believe it’s important to have experience in both engineering and business management.”