Circuit boards are typically rather thin and, therefore, flimsy. While this low profile is an advantage for meeting special limitations, it can be the source of problems arising from lack of to, structural stability. The thinness of the panel can make the board and its circuit connections vulnerable to shock and vibration that will damage or break the soldered connections. Further, the soldering process itself with its input of heat can result in board warpage that can make creation of proper connections difficult, if not impossible.
Various devices have been offered to stiffen a board. Many of these stiffeners are simply bolted to the board. Such fastening means requires access to both sides of the circuit board which is not always available. Even where such access is available, such attachment requires hole alignment and fastener insertion which can add time and, hence, expense to the assembly process. Many of the stiffeners are metallic so they are both electrically and thermally conductive. For certain applications, this can be undesirable. Some assembly techniques require deflection of some portion of an integral stiffener portion to create a fastener. Such mangling of the stiffener makes removal and replacement thereof, should such become desirable, extremely difficult and labor intensive and could result in damage to the board and/or its circuitry.
The present invention overcomes the difficulties with the prior art devices. A stiffener block of rigid material, preferably a high modulus plastic such as liquid crystal polymer, is fastened to one side of a circuit board using a plurality of integral flexible fasteners. Each flexible fastener includes a set of fingers which have arcuate protrusions formed thereon which can underlie a surface of the board and thereby attach the stiffener block thereto. Each of the sets of the fingers surround a cylindrical opening that provides a relief area into which the fingers can flex as they pass through the throughbores in the circuit board. Each of the flexible fingers preferably has a plurality of arcuate protrusions thereon so the stiffener can be used with a plurality of thicknesses of circuit boards. Once the flexible fingers have been inserted into the throughbores in the board, a rigid pin is inserted into the opening thereby maintaining the flexible fingers in an outwardly extended position where said arcuate protrusion underlies the circuit board. It is preferred that the pin be inserted into the opening in the same direction that the flexible fingers are inserted into the circuit board so that assembly can be effected from a single side of the board with access to the opposing side being unnecessary. Further, it is preferred that the pin be metallic and the integral fasteners of the stiffener of the present invention allow the pin to remain thermally and electrically isolated from the circuit board to which the stiffener is attached.
In one preferred embodiment, the stiffener has an I-beam cross section and arches are formed between pairs of flexible fingers. This structure significantly enhances the resistance to bending for the stiffener and the circuit board to which it is attached. An annular compression bump is formed on the flexible fingers which enhances the connection between the board and the stiffener and improves the stiffness imparted to the board.
Both the stiffener itself and the installation technique are inexpensive. Furthermore, the stiffener is very effective at minimizing deflection of the board at all temperatures the board is likely to experience. Lastly, the stiffener can be easily removed and replaced should, for some reason, the stiffener become damaged or otherwise need replacement.
Other features, advantages and characteristics of the present invention will become apparent after a reading of the following detailed description,