Pull force testing checks whether an RF connector can stay mechanically secured to the coaxial cable after termination. For RF cable assemblies, this test is not the same as a general wire terminal pull test. The test needs to look at the connector body, ferrule, cable jacket, braid, center contact. A cable assembly may look acceptable after pulling, yet still show changes in VSWR, insertion loss, return loss, or continuity.
What Pull Force Testing Checks
Pull force testing checks the mechanical retention between the RF connector and the coaxial cable. The main question is simple: when a controlled axial force is applied to the cable assembly, does the connector termination stay stable without slipping, pulling out, or moving internally?
For a crimped RF connector, the test often focuses on the ferrule area. The ferrule needs to hold the cable jacket and shield structure without cutting into the cable or leaving the braid loose. If the ferrule slips during the test, the result usually points to a mismatch between the cable outside diameter, ferrule size, crimp die, strip length, or crimp position.
The test also looks for braid pullout, jacket tearing, center contact movement, and connector body damage. These details matter because mechanical damage can change the electrical path inside the cable assembly. A connector that remains attached is not always electrically stable after loading.
Confirm the Test Type Before Testing
Connector to cable pull force checks whether the terminated connector can hold the coaxial cable under axial tension. This is the main test used when checking crimped or assembled RF cable ends. Shield ferrule retention focuses on how well the ferrule holds the braid and outer cable structure. Center contact retention checks whether the center pin or socket moves after loading.
Mating withdrawal force is a different check. It measures the force needed to separate a mated connector pair. Connector separation force also focuses on the interface, not the cable termination. These tests are useful in their own place, but they cannot replace the pull force test on the connector and cable joint.
Prepare the Cable Assembly Sample
A pull force test starts with a clearly identified sample. The test record needs the cable type, connector series, connector part number, cable length, connector orientation, and sample batch. For example, a small diameter RG174 assembly and a larger RG58 assembly will not respond to the same fixture pressure or the same pull loading condition.
The termination details need to be checked before the sample is pulled. This includes strip length, ferrule size, center contact position, crimp die, tool setting, and the finished connector orientation. If the strip length is inconsistent or the ferrule is not matched to the cable jacket and braid structure, the pull result may show a process problem rather than a connector design problem.
The inspection plan also needs to state whether the test is destructive or non destructive. A destructive test pulls the assembly until failure or until a defined result is reached. A non destructive check applies a controlled force to confirm retention without damaging a shipment sample. The choice depends on the drawing, project requirement, and batch inspection plan.
Set Up the Fixture and Pull Direction
The connector body needs to be held firmly without crushing, tilting, or bending the connector. The cable clamp needs to hold the coaxial cable without cutting into the jacket or deforming the internal coax structure.
The pull direction needs to follow the cable axis as closely as possible. Side loading can create a false failure, especially on small coaxial cables or right angle connectors. If the cable is bent during loading, the test may become a bending test instead of a pull force test.
Right angle RF connectors need special attention. The right angle section cannot become the main stress point during the test. The fixture needs to hold the connector in a way that allows the cable to be pulled along its own exit direction, otherwise the result may reflect connector body leverage rather than termination retention.
Apply the Pull Test
After the sample and fixture are checked, record the sample ID, cable model, connector type, batch information, and test method. The connector body and cable are then fixed into the test setup. Before loading, the assembly needs to be visually checked to confirm that the cable is straight and the connector is not already under bending stress.
The force is applied at a controlled rate. The record normally includes the peak force or the result under a specified holding force. If the inspection plan includes a hold period, the time and any visible movement need to be recorded.
During the test, the operator watches the connector termination area. Any early slip, braid movement, jacket stretching, or contact movement needs to be recorded.
Read the Failure Mode
Ferrule slip means the crimped sleeve has moved on the cable. This can come from ferrule size mismatch, shallow crimping, poor crimp position, or cable outside diameter variation. Braid pullout means the shield structure did not remain captured under the ferrule. This can reduce mechanical retention and may also affect shielding continuity.
Jacket tearing points to stress concentration, fixture damage, or a cable jacket that cannot tolerate the applied loading condition. Center contact movement is more serious for RF performance because the signal path may change even when the outside of the connector still looks acceptable.
Connector body damage usually means the fixture, pull direction, or connector support needs to be reviewed. If there is no visible damage but the RF test result changes, the problem may be inside the connector contact area, shield path, or dielectric position.
FAQ
Conclusion
RF connector pull force testing becomes truly meaningful only when the entire process is clearly documented, including the test object, sample preparation, fixture setup, pull direction, observed failure mode, and any RF verification results. In practice, engineers rarely rely on a single force value to judge quality. A stable connector termination is better understood by looking at how each part behaves under load, such as whether the ferrule holds firmly, the braid stays in place, the cable jacket remains intact, and the center contact and connector body show no unwanted movement or damage.