Essential Materials in Crafting High-Quality Custom Cables

In the evolving world of electronics manufacturing, the materials used to build custom cable assemblies have a direct impact on the performance, durability, and overall reliability of the end product. There are numerous types of materials used, from metals to plastics and from finishes to coatings, with each playing a vital role in how the cable functions and enabling it to meet a wide range of requirements.

By understanding how each material is manufactured and how it’s used within the finished wire harness, engineers and designers can choose the most ideal materials for the application.

Example of a custom manufactured cable assembly.

Anatomy of a Cable Assembly

Before delving into the details of the materials used in custom cable manufacturing, it’s important to understand the anatomy of a cable assembly first. Cable assemblies are comprised of an electrically conductive center conductor, usually made of stranded copper wire.

This center conductor is then wrapped in an electrically insulating cable jacket that is made of an extruded thermoplastic material. Formed as a single conductor wire, or as a group of insulated wires called a multiconductor cable, these raw bulk cables are then cut to size and then terminated with some type of connector.

The types of connectors used vary by application and other requirements, but there are thousands of types of connectors to choose from. Furthermore, these connectors can be overmolded, or incorporate a variety of additional features such as locking tabs, thumb screws, and sealing O-rings.

Copper: The Ideal Electrical Conductor

Copper is the primary material for the center conductors of electrical wires due to its excellent electrical conductivity, flexibility, and relatively low cost. This high conductivity characteristic allows copper to transmit signals and power with minimal resistance and loss, making it the industry standard in cable manufacturing.

The flexibility and malleability of copper also contribute to its widespread use, enabling it to be easily shaped into thin wires that are still durable under physical stress. While copper costs have increased in recent years, it remains a cost-effective material to be used for various parts of the custom cable assemblies.

Brass: Cost-Effective Choice for Terminals

Brass is used throughout custom cable assemblies primarily in the form of contacts and terminals. Brass is electrically conductive given that about two-thirds of its composition is copper. Selected for its mechanical strength and corrosion resistance, brass is chosen since it’s an inexpensive material that can be manufactured into a variety of form factors and shapes.

Commonly used as metal in various connector bodies and contacts, brass components such as knurled knobs, thumbscrews, pins, contacts, and even crimp rings help enhance the durability and reliability of cable connections cost-effectively. Brass components are widely used and are an economical material choice for a wide range of environments and applications.

Stainless Steel: Corrosion Resistant Connector Bodies

Stainless steel is employed in electrical cables for its exceptional resistance to corrosion and oxidation. This makes it ideal for specialty outdoor-rated connector bodies and thumb screws, especially in applications where cables are exposed to harsh environmental conditions. Its strength and resilience help maintain the integrity of connections over extended periods, safeguarding the continuity and performance of the cable.

While stainless steel is electrically conductive, it is far less conductive than other materials such as copper and brass making it an inferior material to be used within the circuit. Instead, stainless steel is used as a mechanical member within these assemblies as opposed to being part of the circuit itself.

Gold: High Reliability & Corrosion Protected Terminals

Gold is a noble metal- which means it’s resistant to oxidation and is applied in ultra-thin layers to exposed contacts of connectors improving reliability. Gold is selected as the plating material on pins, sockets, and terminals because of its excellent corrosion resistance and high conductivity. These properties make it an invaluable material for electrical cable manufacturing but with an additional cost.

If solid gold were to be used, the cables would be astronomically expensive. Instead, thin layers of plated gold are applied to brass terminals helping improve corrosion resistance. These thin layers of gold plating are usually defined in µm, microns, or micrometers, and allow for the benefits of gold without the enormous price tag of using solid gold.

Silver: The Best Electrical Conductor Coating

Silver is another noble metal and has the highest electrical conductivity of any metal. It’s the only metal that is more conductive than copper. Silver is wildly more expensive than copper. Today silver is roughly 100 times the cost of copper, making it impractical to use on most products. Still, some designs warrant the use of silver in the form of silver-coated copper wire.

These applications such as mil-aero and RF applications are common for silver where the performance is necessary to meet the various design objectives.

Tin: Economical Oxidation Prevention and Solderability

Tin is commonly used to coat copper wires, known as tinning, to prevent oxidation and enhance solderability. This process facilitates easier and more reliable soldered connections. Strip and tin are some of the most common drawing notes engineers will add to prints. The act of stripping and tinning refers to removing the insulation from the end of a cable and dipping the exposed copper wire in a bath of molten tin, thus preparing the wire for a secure soldered joint.

This is particularly important in preventing stray strands and ensuring a clean, strong connection in terminal blocks and other connectors. Many stranded copper wires are also tinned before the jacket is added- known as tinned copper. The next time you have a silver-looking inexpensive wire, look closely at the cut wires and you should see it’s just a copper wire with a thin silvery tin coating along the length of the wire.

PTFE: High-Performing Insulation Jacket and Dielectric

Polytetrafluoroethylene (PTFE), also known as Teflon, is renowned for its outstanding thermal stability and chemical resistance. This fact makes it an excellent choice for wire jackets in high-temperature cables. But PTFE jacketed wire is typically more expensive and subject to unattractive minimum order quantities making it cost-inhibitive for many low-volume applications.

PTFE's properties allow it to operate effectively in extreme temperature conditions and aggressive chemical environments, thereby extending the life of the cable. PTFE is also used in specialty RF cables as the dielectric insulator helping achieve ultra-low loss in coaxial cables.

PVC: Cost Effective Insulation & Overmold

Polyvinyl chloride (PVC) is widely used as a jacket material for electrical wires due to its flexibility, durability, and cost-effectiveness. PVC not only protects the internal conductors from physical and environmental damage but also comes in various grades and formulations to meet different fire-resistance, oil-resistance, and temperature requirements.

PVC can be extruded and overmolded using standard equipment making it the most common thermoplastic used in everyday cables and wire harnesses.

TPE: Flexible and Durable Cable Jacket

Thermoplastic elastomer (TPE) is an essential material in the cable industry, used for its durability and flexibility. TPE, like PVC, serves as a jacket material and is often used for overmolds providing a rubbery feel to the cable. Many power cables use a TPE jacket for its toughness and its resilience to cyclic bending and flexures. If a tight minimum bend radius or highly flexible overmold is needed, TPE is a cost-effective choice to consider.

Nylon: Flame Retardant Connector Bodies

Nylon is another essential material that is used throughout the cable industry, but not actually used in the raw cables themselves. Nylon is one of the most common injection molded plastics that are used for single and dual-row plastic connectors where the terminals are crimped separately and then installed into a housing.

Sometimes referred to as HSG connectors, and recognizable as white or black-colored rigid plastic housings, these components are inexpensive and made in ultra-high volumes for countless electronics applications. Most nylon carries a UL94V-0 flammability rating allowing it to be used without question.

Polyolefin: Heat Shrinkable Insulating Sleeve

Polyolefin is the raw material used in heat shrink sleeving, a protective cable covering that shrinks upon exposure to heat. This material provides excellent electrical insulation, protects against abrasion, and ensures a sealed environment to prevent the ingress of moisture and other contaminants.

Some options of heat shrink are available with an adhesive liner to better secure the sleeve and further improve ingress protection.

Silicone Elastomer: Low-Cost Waterproofing Material

In the electrical cable sector, silicone elastomers are pivotal for gasketing, sealing plugs, and various types of O-rings. This material's flexibility and thermal resistance over a wide range of temperatures make it ideal for applications requiring tight seals in varying environmental conditions.

Many connector designs are sold with kits of O-rings and sealing plugs to be installed during assembly helping achieve IP ratings such as IP67 or higher.

Conductivity for Materials used within Cable Assemblies

Summary

Understanding the properties and applications of these materials is crucial for engineers and designers in the cable industry. By selecting the appropriate materials based on the environmental conditions and electrical requirements, one can significantly enhance the performance, longevity, and reliability of custom cables.

As technology progresses, the evolution of materials will continue to play a pivotal role in meeting the ever-increasing demands of electronic devices and systems.