Connectors are used very frequently, and everyone is familiar with connectors. However, during the use of the connector, there may be a connection failure problem. In this article, the editor will introduce the reasons for the failure of the connector connection. In addition, this article will address the considerations for board-to-board connector testing.
1. Discussion on the cause of connector connection failure
Compared with the outer conductor, the inner conductor of the connector is smaller in size, and the inner conductor with poor strength is more likely to cause poor contact and lead to the failure of the connector.
Most of the inner conductors of the connector adopt elastic connection methods, such as spring claw type elastic connection, socket slot type elastic connection, bellows type elastic connection, and so on. Among them, the slotted elastic connection structure of the jack is simple, the processing cost is low, the assembly is more convenient, and the application range is the most extensive.
1. The inner conductor is not fixed firmly
For assembly needs, in the structure of many RF coaxial connectors (such as N-type, 3.5mm), the inner conductor is divided into two parts at the dielectric support and then connected with screws. However, due to the small diameter of the inner conductor, if the glue is not applied to the threaded connection to fix it during assembly, the connection strength of the inner conductor is very poor, especially for some small RF coaxial connectors. Therefore, when the connector is connected and disconnected for many times, under the long-term action of torsion and tension, the inner conductor thread may loosen and fall off, resulting in connection failure.
One of the commonly used structures of RF coaxial connectors is that the inner conductor, the dielectric support, and the outer conductor are fixed together by adhesive. If the amount of glue applied in this structure is not enough or the connection strength of the glue is not enough during assembly, the glued part may break due to the force during use, which will cause the inner conductor to rotate or move axially, and the inner conductors A good electrical contact cannot be formed and the connection fails.
Improvement method: When the coaxial connector is assembled, an appropriate amount of conductive glue or thread locking agent can be applied to the threaded connection to increase its reliability of the threaded connection. Adhesives with higher bonding strength should be selected, and the glue must fill the entire glued hole when gluing; knurling at the glued part of the inner conductor increases the contact area between the inner conductor and the adhesive to prevent the inner conductor from rotating; adjust the inner conductor properly The radial dimensions and tolerances of the conductor, the outer conductor and the dielectric support make the fit between the inner conductor and the dielectric support, between the dielectric support and the outer conductor an interference fit, and can also make the three fit together more firmly.
2. Incorrect size of the jack or pin of the inner conductor
If the hole diameter of the inner conductor of the jack is smaller than the specified size when the pin of the inner conductor of the pin enters the jack, the jack will be over-expanded, the deformation amount will exceed its elastic deformation range, plastic deformation will occur, and the conductor in the jack will be damaged; On the contrary, if the diameter of the pin is too small, when the pin and the jack are matched, the gap between the pin and the wall of the jack is too large, the two inner conductors of the connector cannot be in close contact, the contact resistance becomes large, and the connector's Electrical performance indicators will also be poor.
Improvement method: Whether the matching of the jack and the pin is reasonable, we can use the insertion force and retention force of the standard gauge pin and the conductor in the jack to measure. For N-type connectors, the insertion force when the diameter Φ1.6760+0.005 standard gauge pin is matched with the jack should be ≤9N, and the holding force when the diameter Φ1.6000-0.005 standard gauge pin and the inner conductor of the jack are matched ≥0.56N.
Therefore, we can use the insertion force and retention force as inspection standards. By adjusting the size and tolerance of the socket and the pin, as well as the aging treatment process of the conductor in the socket, the insertion force and retention force between the pin and the socket can be adjusted. in an appropriate range.
