Printed circuit boards often need a wire harness
or cable assembly for connection to power input or to other parts of the electronic system. One of the things a designer needs to think
about with cable assemblies is the need for strain relief…
how will you make sure that pulling on a cable during normal use will not damage the connection
to the printed circuit board? There are several techniques we can use.
For single wires and simple wire harnesses, it’s common to crimp a connector onto the wire. This is typical for wire harnesses that are
internal to the final system. In addition to having a contact that clamps
onto the conducting wire – the crimp can have a flange that clamps onto the insulation.
This provides strain relief to protect the connection during system installation and use. For more complex cable assemblies, we have
strain relief backshells… commercial off-the-shelf parts that slide onto to the cable and tighten onto the connector. They are great for low-volume production but
can cost from $1 each, to $50 each for military grade parts.
So for higher volumes, overmolded strain relief is usually more economical.
The cable assembly is placed into a mold and then resin is injected into the mold to encase
the cable and connector. This provides a strong and water-resistant strain relief. An up-front investment is needed to design
and build the mold. With this low-temperature, low-pressure injection
molding press we can use an aluminum mold with an initial cost of about $10,000 to design and build. It is good for about 100K shots and can then
be replaced for a little over $3K. Overmolded strain relief can be completely
customized with respect to size, shape and material used. It can also provide superior performance compared to other strain relief techniques.
Contact us to learn more about strain relief and other factors in the design and production
of wire harnesses and cable assemblies for electronic products.