ELIMINATING LONG TERM VIBRATION PROBLEMS

A critical concern when applying connectors to printed circuit boards is the long-term durability as it relates to temperature cycling and vibration. Initial success has proven in some cases to mask problems that will tend to plague the application over time. Many times the specific problems seen are not the root cause of the failure.

A typical heavy-duty applicatio n uses either a straight  extended pin connector or a connector with pins that are bent 90 ° to the axis of the connector. Where the connector mates with the board, there is a feature which is a mechanical attachment for the connector to the pc board independent of the solder. The engaging end of the connector normally goes through an opening in the box that houses the PC board. The connector is then attached to the box during which time a seal of some type is used to prevent moisture intrusion into the box.

The design of the box, the PC board, the connector and the seal must account for the forces that will be generated by temperature cycling and vibration. The main concern is  that it is undesirable to have the PC board flexed in service. It is equally undesirable to have the soldered terminal on the connector under stress in service and an allowance must be made to assure that stress between the PC board and connector does not prevent the seal from performing. There are a variety of methods that can be used to provide a successful design. These methods include having the PC  board loose in the box and then pot the box with a flexible sealant after the sealing flange is attached to the box. Another possibility would be to reflow the solder after the board and connector are mounted in the box. There are several other good approaches to solving these problems and providing a trouble free installation. Consult Deutsch application engineers.

IPD Technical Papers

ENGINEERED CONNECTING DEVICES