Printed circuit cards are subject to warpage and linear distortion due to the weight of electronic components and stress applied during the soldering process. A result of the distortion and warpage may be a physically weakened substrate. It is a problem to maintain the integrity of the solder joints during card insertion and extraction of such weakened substrates.
Another problem arises when using printed circuit cards which employ the so called "low wipe" connectors. Wipe refers to the action that occurs when a circuit card is inserted in an electronic structure. The "wiping" action occurs when the contact of the circuit card with the connector contact element wipes away any oxide or other contaminant on the circuit card contact terminal so as to reliably engage the base metal. Low wipe means that the amount of surface area available for the contacting elements is significantly smaller than a normal wipe environment. Low wipe environments are the product of increasingly compact designs required by the need to more densely pack electronic machinery.
An inherent problem within low wipe environments is that very tight tolerances must be obtained in order to effectuate electrical contact. Significantly, the amount of contact length that may be available on a low wipe connector may be in the neighborhood of 0.040 of an inch (1 millimeter). When all the worst case dimensional tolerances are added together for each component required in the electronic packaging of the circuit card it can be seen that obtaining the proper dimensional relationship would require extremely strict control of the dimensions of each component.
Maintaining tight tolerances requires quality testing of components during manufacturing and frequent rejection of parts. Such testing and subsequent rejection requires time and added cost due to time and the scrapped parts.
The limited contact in low wipe connectors presents another problem. Due to the small amount of contact area available in low wipe connectors, a skewed angle of approach of a low wipe connector to a mating connector could result in lack of electrical contact.
The size and shape of a strengthening and stiffening device must be such that it can overcome problems inherent in electronic packaging. Dense packaging of electronic circuit cards limits the amount of space available for such a stiffening and strengthening device. Also, the shape and size of the device must allow cooling air to flow unimpeded over the electronic components.
In prior designs, card stiffeners had to be mechanically fastened to the card assembly to ensure proper operation and stiffness. This resulted in an expensive installation by requiring special tools and an increased assembly time to attach the hardware.
Rework results in damage to cards and scraping hardware. It also increases cost by requiring fixtures for use during component removal.
Low wipe connector systems require the use of a tool actuated mechanical fastener to provide a reliable card retention mechanism during shock and vibration testing. This requirement results in expensive installation due to the cost of special tools and increased assembly time.
Accordingly, an apparatus that overcomes the above disadvantages while strengthening and supporting printed circuit cards would constitute a significant advancement in the art.