“Naked” IDCs as Workaround Solutions in Extreme Environments
End products intended for use in harsh applications are often potted or overmolded to make them impact-resistant and/or waterproof. Although beneficial for the end consumer, this final encapsulation process can negatively affect the electrical and mechanical integrity of the product’s connections.
With so many connector options available, it can be difficult to filter through the technical attributes of each and select the best solution for a particular application. Steady market demand for expanded connectivity (e.g., the IoT) has resulted in the smartening of an exponential array of products. As such, connectors – along with other advanced electronics – are now designed into outdoor, mobile, transportation, and other harsh environment applications with increasing frequency, to provide these products with the ability to consistently and reliably gather, manage, monitor, and transmit data. The more severe the environment in which a connector must survive, the more impact connector selection will have on system performance.
End products intended for use in harsh outdoor, mobile, and transportation applications are often potted or overmolded to make them impact-resistant and/or waterproof. Although beneficial for the end consumer, this final encapsulation process can negatively affect the electrical and mechanical integrity of the product’s connections. Most of the components on a PCB are immune to potting and overmolding since they tend to be soldered directly onto the board, but that is not the case for connectors.
Connectors are different because they function under the principle of applying and maintaining compression force between two surfaces to make an electrical connection. For example, a compression contact will survive severe temperatures, shocks, and vibrations in even the harshest environmental conditions with no issues. However, if we add in an encapsulation process that is foreign to both standard PCBs and interconnect products and processes, new concerns arise. The first and foremost of these is material intrusion. Potting and overmolding materials can leech into the contact area, insulate the contacts, and cause an immediate electrical failure or — worse yet — prevent the contacts from maintaining sufficient force over time and temperature, producing an unanticipated field failure at a later date.
The simplest solution to this problem would be to solder the wires to the PCB like all of the other components. However, unlike the controlled SMT processes all of the other board-level components underwent, soldering is a time-consuming and costly manual process that is frequently riddled with process variations.
The most reliable solution to the problems that often arise when potting or overmolding connectors for harsh environment applications is insulation-displacement contact (IDC) technology. It has roots dating back more than 50 years and has evolved into a proven wire-to-board connection solution for harsh environment applications, as well as one of the most trusted contact technologies employed in automotive and other transportation applications. But be careful; not all IDC designs are the same.
Generally speaking, most IDC connectors were developed to accommodate a variety of wire gauges, which makes them inherently versatile and easy to implement in standard environment applications and has also made them very popular. However, not just any IDC offering will suffice in harsh environment applications. Harsh, potting-type applications require an especially robust contact design that will effectively prohibit potting material ingress and protect the electrical integrity of the connection.
To achieve this level of protection, you’ll need to match a specific wire size (AWG) to a specific contact slot dimension in order to create a cold-welded metal-on-metal bond between the two surfaces during the wire insertion process (Figure 1). The quality of an IDC connector’s base contact material and beam or tine design are critical for successfully achieving this cold-welded bond, as those two features are responsible for providing sufficient contact deflection during the wire-insertion process. This prevents the cutting of strands and provides the IDC with the capabilities it needs to survive long-term temperature cycling and thermal expansion cycles while simultaneously maintaining a continuous high-force, gas-tight connection for electrical and mechanical stability onto the wire. Proven to survive in even the harshest transportation applications for more than 30 years now, robust IDC connectors far outperform the broader, more flexible, multi-AWG-range products that were developed for the computer and telecommunications market.
This enhanced IDC design also provides additional wire termination benefits that effectively surmount what has long been considered a significant barrier to the broader adoption of IDC technology in demanding applications beyond communications and consumer electronics. When first developed, IDC technology was based solely on insulated stranded-wire applications, but has since evolved to accommodate solid-wire and single-conductor applications as well. Figure #2 shows the basic anatomy of an automotive-grade electrolytic capacitor holder that terminates single, bare conductor wires – or, in this case, leads – into the matched IDC contact slots to provide the high-reliability, gas-tight level of protection required by critical automotive safety systems.
Another myth surrounding IDC technology – and, in reality, the entire connector industry – is the belief that a connector must always have an insulator. Although insulators can certainly play key roles in connector adaptation, in truth, they only add cost to optimally designed contact systems. This is evidenced by the fact that so many naked or uninsulated board-to-board and wire-to-board connectors have been developed, qualified, and released to market over the past decade.
Throughout this span, the technology has both matured and expanded. The first naked IDC connectors were introduced to the market in 2010. These connectors, when soldered to a PCB and threaded with a wire, provide all of the same cold-welded wire termination properties described above – even after potting and encapsulation – and can also offer lower profiles, individual placements, and more cost-effective alternatives without jeopardizing electrical or mechanical performance.
Although innovative and still relatively new – within the context of the connector industry at least – naked connector technology has been proven in an array of industries and applications including automotive, transportation, mobile, and outdoor applications.
Tom Anderson is the connector product manager at AVX.