New PCB Retainer Design Eliminates the Need for a Torque Wrench
22 June 2010
New from Schroff are the Calmark Series 223 and 224 Card-Lok PCB retainers, which incorporate a patent-pending 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.
Primarily aimed at cold-plate heat-transfer applications within the defence and aerospace sector, these new five-wedge devices are designed to prevent damage to the PCB or to the Card-Lok itself due to over-tightening.
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 1200N when torqued. As well as providing maximum resistance to shock and vibration, the Card-Loks also play a major role in dissipating heat from the PCB. The devices feature a light-weight aluminium construction and can be specified with various finishes, including black anodised, electroless nickel and chemical film. They are available with profiles of either 5.72mm x 6.60mm (Series 223) or 5.33mm x 6.99mm (Series 224) in a wide range of standard lengths from 121.9mm to 329.9mm.
The new Card-Loks are manufactured by Calmark, one of Schroff's sister companies within the Pentair Technical Products Group.
