Missile launcher

Providing a coupling between a flexible PCB and a military standard circular connector has helped with the design of a missile launching mechanism

When designing a launching mechanism for the Starstreak missile, engineers at Shorts Missile Systems of Belfast were faced with the problem of how to effect a coupling between a flexible PCB and a military standard circular connector while maintaining high levels of electrical and environmental protection.

Solder spill contacts were adopted as the termination method between the connector and the PCB. The problem to be overcome was how to secure the metal shell of the connector to the grounding plane of the flexible PCB. The overall profile of the PCB assembly was severely restricted and the solution had to cope with this and the fact that the construction of the board itself was extremely delicate.

Design engineers at KEC were commissioned to solve this problem and the resultant design has now become a standard method of solving similar problems.

The solution adopted was a specially machined assembly consisting of an interface plate that fits between the connector and the PCB and a low profile closing cap, complete with a conductive seal, that fits on the other side of the PCB. Rather than using clamps or jackscrew type connection, the closing cap is secured to the connector via a central screw in order to save space.

The inside of the interface was chamfered to work on and compress a sealing grommet on the rear of the connector. The use of fine machining tolerances ensured a close fit between the interface plate and the closing gap. The conductive seal, which was impregnated with silver, encloses the point of entry between the flexible PCB and the backshell to provide both electrical and environmental protection. This seal also provides good electrical connection to the grounding plane of the PCB without extensive pressure being extended and damage being caused to the PCB.

Designated KA 023, the complete assembly can be modified to suit similar connector/PCB interfaces.

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