Overmolded Cable Connectors [The Minimally Invasive Guide]

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Within the minimally invasive segment, overmolded cable connectors can reduce or eliminate many of the risks and disadvantages associated with off-the-shelf, mechanically assembled connectors.

Transitioning your minimally invasive device from an assembled connector (which was probably designed for an industrial or consumer application) to an overmolded connector requires extensive understanding of the device application and requirements.

This post will explain the basics behind overmolded connectors, the differences between overmolded and mechanically assembled connectors, and how to decide which is right for your application.

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What are overmolded cable connectors?

An overmolded cable connector is simultaneously created and attached to a cable through an injection molding process.

This is different from a mechanically assembled connector that is purchased as an existing component and then attached to a cable through an additive process (e.g., bonding, gluing, etc.).

How are overmolded cable connectors different from mechanically assembled connectors?

Due to the fact that components can be purchased off-the-shelf from online resources and catalogs, mechanically assembled connectors provide an easy way to get started with development builds and prototypes.

However..

These off-the-shelf, mechanically assembled connectors do not guarantee the long-term stability, functionality, or future cost-down considerations required for sustainable mass production of a minimally invasive device.

Overmolded cable connectors provide three major benefits compared to mechanically assembled connectors:

  1. Customization
  2. Lower Costs
  3. Improved Performance

 

Customization

As overmolded cable connectors are injection molded and designed to your exact needs, they must be customized.

This means you are not limited by off-the-shelf offerings that may or may not have been created for your application and purpose-of-use.

The freedom of design provided by customization enables you to incorporate the voice-of-the-customer into your connector design to meet the needs and wants of the people using your minimally invasive device.

Though the word “customization” can be associated with higher costs, this is not necessarily the case for overmolded cable connectors, as you’ll see below.

Lower Costs

To properly secure an off-the-shelf connector to a cable assembly numerous components, pieces, and manufacturing process steps are required.

These additional manufacturing requirements can result in increased labor and material costs, as well as increased inventory costs and headaches, as you must store and guarantee equal quantities of each component required to produce an assembly.

When you design a connector to meet your exact needs, you design out the unnecessary components, materials, and manufacturing steps that are required by an off-the-shelf connector.

This leads to lower material costs and less time spent producing the cable connector and managing the supply chain.

Improved Performance

The overmolding process provides certain inherent benefits that mechanical assembly cannot.

As the plastic encapsulates the wires, it naturally secures the soldered wire to the pin. This provides insulation, strain relief, and a better seal (meaning improved moisture and water protection) than a mechanically assembled connector.

If your device requires one, two, eight, or more conductors, overmolded cable connectors can help you reach a level of performance that off-the-shelf, mechanically assembled connectors cannot.

Process Differences

The diagram below illustrates the number of process steps and the typical process differences between overmolded cable connectors and mechanically assembled connectors.

 

Overmolded Cable Connector Process

Solder individual wires to connector terminals.

Perform electrical test to verify correct pinout, dielectric withstanding voltage compliance, insulation resistance, and connection resistance.

Place terminated connector/cable into molding press and inject inner mold. Inspect for complete fill of the mold.

Align key and slide connector shell over the pin carrier, completing the assembly.

Perform final electrical test to verify correct pinout, dielectric withstanding voltage compliance, insulation resistance and connection resistance.

Pack for shipment.

Off-The-Shelf Mechanically Assembled Connector

Note orientation of bend relief, install over cable, and slide up out of the way.

Note orientation of the collet nut, install over cable, and slide up out of the way.

Select collet option that is properly sized for the cable diameter being used. Note orientation of collet, install over cable, and slide up out of the way.

Solder individual wires to connector terminals.

Perform electrical test to verify correct pinout, dielectric withstanding voltage compliance, insulation resistance, and connection resistance. Slide collet down the cable, align key with the pin carrier, and engage to the pin carrier. Secure collet to the pin carrier using cyanoacrylate adhesive to prevent the collet from becoming misaligned or disengaged from the pin carrier during next step.

Orient the cable, pin carrier, and collet subassembly with the open end of the collet facing up. Mix or otherwise prepare the epoxy potting compound if required. If using a dispensing system, introduce the epoxy potting compound into the dispense receptacle. Exercise care to assure potting does not migrate into an area that will interfere with subsequent assembly steps. Inspect for said condition and clean/rework as required.

Place the sub-assembly from the previous process aside, exercising care to maintain the vertical orientation. Allow epoxy potting compound to cure as specified.

Place the sub-assembly from the previous process aside, exercising care to maintain the vertical orientation. Allow epoxy potting compound to cure as specified.

Optionally, repeat electrical testing to verify sub-assembly integrity before additional processing.

Apply thread locker to the collet nut threads.

Slide the collet nut down the cable and thread onto the connector shell/latch. Tighten with a torque wrench to the manufacturer’s specified value.

Apply glue to the collet nut for additional security of the bend relief attachment. Slide the bend relief down the cable and engage into the groove on the collet nut.

Perform final electrical test to verify correct pinout, dielectric withstanding voltage compliance, insulation resistance, and connection resistance.

Pack for shipment.


How are overmolded cable connectors created?

Overmolding a cable connector typically employs a two-step process.

Step 1: Apply the Inner Mold

The first step is to apply an inner mold, which is used to encapsulate the terminations and the cable wires as well as provide a support structure for the exterior (or “cosmetic”) outer mold.

The inner mold also allows the use of multiple materials to obtain the desired final properties.

For example..

A less expensive material can be used for the inner mold while a thin and consistent layer of higher-grade material is used for the outer mold.

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If an inner mold is not used, wires are not encapsulated which can lead to performance issues.

As the inner mold creates a support structure for the outer mold, omitting an inner mold can cause cosmetic defects such as pits, sinks, and other injection molding problems.

Step 2: Apply the Outer Mold

After the inner mold has been added to the cable assembly, the outer mold must be applied.

The outer mold provides both cosmetic and functional properties to the connector.

Though an inner mold can be applied across different cable assemblies, the outer mold can be altered or customized to enable differentiation between product lines and competing devices.

For example..

A generic cable assembly with an inner mold can have multiple outer mold geometries, colors, or logos applied to it.

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Incorporating PCBAs into overmolded cable connectors.

Within the minimally invasive market, it is common to have a PCB assembly incorporated as a component of the connector.

Whether you’re overmolding flex PCB or rigid PCB, the processes and expertise required differs from what is necessary to overmold connectors.

However..

The basic concept remains: overmolding helps you achieve customization, lower costs, and improved performance (including improved moisture resistance) from your PCB assemblies.

Determining the right connector platform for your needs.

As mentioned above, the ease with which off-the-shelf connectors can be obtained make mechanically assembled connectors a viable option in development scenarios and low volume production.

Due to the easier manufacturability, improved insulation, natural strain relief, and better seal, overmolded cable connectors are a superior option in high-volume applications where performance is critical.

Want to learn more about overmolded cable connectors?

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