These days, USB connectors are a standard means of sharing both data and providing power to a wide range of devices. Therefore, the connectors are required to be extremely robust and last for long periods while maintaining high-functionality.
Some connectors may be afflicted by wear due to repeated insertion and extraction, so it is vital to know how many cycles of insertion and withdrawal a USB connector design can withstand before degradation in its electrical or mechanical performance. Cyclic loading not only imparts useful information on connector lifetime but is also a method of testing design changes such as spring force, pin shape, coating, and lubrication. Complete connectors or individual pins can be tested, and electrical resistance measurements can be used to analyze any damage inflicted by small repeated movements (fretting) see figure 1.
Figure 1: Test for fretting or test individual pins.
There are numerous methods to test connectors:
- Insertion Force – the maximum push force needed to push the two halves of the connector together
- Fretting – small rubbing movement between surfaces that are forced together.
- Withdrawal Force – the maximum pull force needed to pull the connector apart
- Contact Resistance – the electrical resistance associated with the point of contact, typically around 10-30 mΩ
- Spring Constant – stiffness of the contact. Stiff contacts lead to high friction forces, which can reduce fretting and contact resistance but result in higher insertion and withdrawal forces
- Fretting Corrosion – oxidation of contacts due to fretting
The optimum test method depends on the attributes of the materials being used.
Working with the Manufacturing Technology Centre (MTC), Nordson DAGE have to develop a bespoke tooling and testing methodology to characterize connector integrity and degradation through cyclic insertion and withdrawal testing. The Nordson DAGE USB connector wear jig comes equipped with a self-aligning function that vastly reduces the loads in the X and Y direction while the USB connector is being moved in the Z direction. The withdrawal processes can be simulated by locking this jig in place after the initial alignment where the connector is held rigidly.
||Low cost, few mating cycles, susceptible to fretting corrosion
||High resistance to corrosion, low insertion force, high number of mating cycles
||Mainly used for high current contacts
|Hard gold flashed palladium-nickel
||Particularly suitable for low signal levels, low wear, high number of mating cycles
Two Ways of Testing
The Nordson DAGE 4000Plus supplies a dynamic testing platform, with ParagonTM Materials Software, but a specialist or custom jig may be needed to support samples such as USB connectors.
To measure the repeated and cyclic performance of a USB design, the connector must be inserted and withdrawn from the mating connector over and over, while the force of insertion and withdrawal is measured to understand its mechanical performance, as well as recording its electrical performance, such as pin resistance – all of this must be carried out during the same experiment. The instrument is compatible with any 0-10 V external measuring device, so during the experiment, a resistance meter can be used to generate a resistance versus time graph in real-time. Paragon Materials Software can trigger the data capture in external devices as well, for multi-channel data capture devices.
Figure 2: USB self-aligning connector jig.
Figure 3: X, Y and Z axis control to < 1 micron for connector alignment.
Figure 4: Paragon Materials software interface showing multiple test cycles.
Testing is performed to the following standards:
||3.4 Durability, connectors
||3.18 Mating and unmating force, connectors
||Durability test procedure for electrical connectors and contacts
||2012.1 Contact insertion and removal forces
2013.1 Mating and unmating forces
2014 Contact engagement and separation
Nordson DAGE, The Partner of Choice for Advanced Testing
The Nordson DAGE micro-mechanical tester can be used to carry out this experiment rather than enduring the process of designing and constructing a bespoke testing frame. It is a highly flexible, easy-to-use platform with a wide scope for mechanical testing. With different cartridge and software options available, the experiment can be altered very easily, and quickly.
The Manufacturing Technology Centre (MTC)
The MTC develops and proves state-of-the-art manufacturing processes and technologies in a low-risk and agile environment, in collaboration with industry, academia, and other institutions. The MTC has a direct focus on delivering customized manufacturing system solutions for its customers. Operating some of the most advanced manufacturing equipment in the world, the MTC employs a team of highly skilled engineers, many of whom are experts that lead in their field. This allows for an environment of the highest quality for the research, development, and demonstration of new processes and technologies on an industrial scale.
The MTC is part of the High Value Manufacturing Catapult, supported by Innovate UK.
This information has been sourced, reviewed and adapted from materials provided by Nordson DAGE.
For more information on this source, please visit Nordson DAGE.