One of the breakthrough connectors of the 20th century was the Berg PV contact. Some of you will know that Quentin Berg started Berg Electronics back in 1950. When Berg left AMP to start his own company, one of his key inventions and the basis of the company was the mini PV contact.
This new contact was unique in several ways:
• The contact was stamped end-to-end on a continuous strip, minimizing scrap. Most contacts at the time were stamped at a right angle to the carrier strip like a comb. The contact pitch on the carrier was N times the contact pitch used in the finished product. The metal between the contacts as well as the carrier strip all ended up in the scrap bin. The Berg end-to-end approach kept the contact cost low.
• This design also facilitated very select plating. Mr. Berg used a narrow stripe down the centerline of the contact. At the time, most contacts were plated with 50 µin. of gold covering the whole contact. Later, this plating process was further improved to have gold in a plated “dot” only in the contact area. It was not necessary to gold plate this spring since the electrical path for the current flowed from the pin through the contact dimples on the receptacle, bypassing the spring. The spring’s only function is to provide normal force.
• The most important innovation was the use of a secondary spring made of beryllium copper that pressed the mating pin against two contact dimples with a very precise normal force. This spring is inserted into tabs on the copper alloy contact and is able to float inside the contact so that the spring action is very consistent. You can imagine the high level of die technology needed to marry two stamped strips of different metals at high speed stamping rates (500-1000 strokes/min).
• Some applications require high pin count connectors. These customers desired lower mating forces to enable assembly technicians to more easily mate and unmate connectors. Other customers used very small connectors with only 1-4 contacts for switch and sensor wires and the like. They preferred high contact retention force to better withstand vibration and handling. By choosing different thicknesses of the beryllium copper springs, Berg was able to offer versions of PV optimized for each of these applications.
• The gentle controlled mating dynamics of this mating system allowed very high cycle life >500 mating cycles, providing a highly reliable mating system. Old timers tell me that the PV name stood for “Perpetual Virgin” because the contact was as good as new after many mating cycles.
Mr. Berg offered bandoliered 0.025 in. square pins on reels to mate with the PV. These pins were superior to the stamped pins offered by most competitors at the time in that they were made from drawn wire. Drawing wire creates a pin that was square, with all sides smooth, allowing the female contact to mate to any side of the pin with equal performance. In contrast, typical stamped pins were blanked out of flat stock so that the top side was a nice smooth domed surface, the bottom side of the pin has a slight burr on each corner from the stamping die and the sheered sides were rougher. Another advantage of the Berg drawn wire approach was that almost no metal was wasted since the pins were stamped end to end from continuous wire. The wire could be pre-plated, a very efficient way to get a precise coating of gold over all four surfaces of the pin.
Berg developed customer application machines to apply these pins into boards at the customer’s plant. The stitching head was positioned over an X-Y table. The operator would move the board under the head, triggering the insertion at each hole location. To facilitate accuracy, the operator had a stylus that was maneuvered over a plate with precisely placed holes. As the stylus pin reached each hole, the machine would insert a pin into the corresponding location on the printed circuit board. Later, the same operator interface was tied to multiple insertion heads, inserting pins in three boards at a time. Each board would have precisely the needed number of pins in exactly the right location on the board. Frequently, no housing was needed around the pins, keeping cost down and the design simple and flexible. Customers with larger board quantities moved to computer controlled systems, further increasing capacity, quality and productivity.
The disadvantage of the machine-applied pins was that it was difficult to populate prototype boards without investing in a machine. Mr. Berg designed a plastic pin carrier for single and dual rows of pins. These 36- and 72-pin carriers could be snapped off between positions to create the precise pin configuration needed for the prototypes. Say a 2×10 or 1×4 array, as examples. Customers and distributors quickly discovered that this is a really handy way to provide pin arrays and the “BergStik” was born. For about three years, Mr. Berg could not build capacity fast enough to satisfy demand for the handy-to-use pin-stick headers. As volume grew, specific configurations of plastic headers were tooled, including side walls that protected the pins, provided orientation for the cables, and later on, latching. This family of cable and board-to-board connectors became known as “Bergcon.”
The PV contact was a huge success for the fledgling new Berg Electronics Co. Mr. Berg proliferated this contact into crimp-to-wire cable assemblies and vertical and horizontal card connectors, all of which mated to 0.025 in. square pins, creating a broad product offering in only a few years. The primary user was IBM who used this contact across many generations of mainframe computers. The Bergcon family of card and cable connectors grew very quickly as it was adopted by many different customers and industries. In 1966, Mr. Berg sold his company to DuPont for $25 million and retired. Not bad for a sole proprietor! DuPont expanded on the concept and developed many other connectors, growing twenty-fold to about $500 million before selling the business off in 1995.
Berg’s genius was not only the invention of the product, but also understanding the needs of the customer so well that he was able to grow the business continuously, implementing process improvements with each capacity addition that yielded a superior product at a competitive price. Berg Electronics was famous for excellence in engineering, tool making and manufacturing.
You can still buy PV-based products today. After several owners, including Hicks-Muse, Framatome, FCI, Bain Capital, and soon Amphenol, Mr. Berg’s legacy is still alive and well and the BergCon and PV names live on.