Calmark Retainers Protect PCBs In Defence Apps

Aimed at cold-plate heat-transfer applications within the defence and aerospace sector, Schroff's Calmark retainers are designed to prevent damage to the PCB or the Card-Lok due to over-tightening. The five-wedge Series 223 and 224 Card-Lok PCB retainers incorporate a torque-limiting feature that enables a PCB assembly to be fixed into a chassis at a prescribed clamping force without the need for a torque wrench.

By turning the centre screw clockwise, the outer wedges are drawn together, forcing the centre wedge sections to expand outwards. When the turning force exerted on the screw reaches the preset torque, the built-in ratchet clutch disengages with an audible click to prevent further tightening. The Series 223 and 224 retainers generate a minimum clamping force of 1,200N when torqued.

As well as providing maximum resistance to shock and vibration, the Card-Loks also play a role in dissipating heat from the PCB. The devices feature a lightweight aluminium construction and can be specified with various finishes, including black anodised, electroless nickel and chemical film. They are available with profiles of 5.72 x 6.6mm (Series 223) or 5.33 x 6.99mm (Series 224) in a range of standard lengths from 121.9 to 329.9mm.

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