This section describes a contact and connector fabrication technique for board-to-bard interconnections that combine high-production metal stamping and forming with thermal plastic-to-metal bonding. The number of interconnection elements is significantly reduced as are the assembly operations required. The result is a highly reliable, versatile connector of minimal size, weight, cost and complexity.
The Contacts
Tin-plated contacts are stamped from a strip of 0.010" phosphor bronze. The strips are then formed into shape. Since the contact engages both sides of the board, connector terminal pads can be located on either or both sides of the board. This offers the packaging engineer the versatility of using any combination of the four inside and outside board edges.
Adding to the versatility of this contact is the residual spring force designed into both the clip portion into which the board is inserted, and the bend at the center of the contact. This assures a reliable connection between warped or bowed printed circuit boards.
The Connector
Production of a board-to-board connector is greatly simplified by laminating the blank strips of contacts between two layers of thermal plastic. Labor and material costs normally associated with the loading of individual contacts into plastic connector bodies is wholly eliminated. In addition, circuit complexity is greatly reduced. This unique fabrication technique also eliminates the high cost of tooling required for each different size of molded connector housing. One set of tooling is used to form what amounts to a very long connector of common contact and board spacing. Any number of contacts can then be cut off offering the packaging engineer a very large variety of connector sizes.
Connector Housings
In those applications where the connector must undergo repeated extractions and insertions, a more rugged version of the connector may be more appropriate. For these situations, a simplified body has been designed that can be inexpensively extruded or molded in long lengths and then cut to fit any required number of contacts.
Reliability The spring system of any contact must, of course, provide sufficient normal force to sustain a reliable circuit. The normal force depends on many factors including (l) the plating used, (2) the acceptable insertion/extraction forces, and (3) the number of wear cycles, or times the connector will be inserted and extracted, To meet the design objectives of a reliable connector, a nominal normal force requirement of 200 grams was established. Under the worst conditions, a force of no less than 100 grams would be tolerable. Once the general shape of the contact and normal force criteria were set, a computer study was implemented to optimize the contact geometry.
Summary
The board-to-board interconnect system is designed to provide reliable, low cost interconnections between two parallel mounted printed circuit boards. By
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