Advanced Interconnection

Surface Mount PGA Connector Technology Enables Development of Custom Board-to-Board Connector System

West Warwick, RI, USA - May 7, 2003 - When unique PC board electrical connectivity problems arise, Advanced Interconnections (AIC) can devise custom socketing systems to solve them reliably and economically. For example, consider the case of a major automotive-electronics test equipment manufacturer, which needed to overcome several design challenges involving stackable, socketed PC test boards employed by users to field-configure the manufacturerís rear-end and engine test systems.

Initially, the manufacturer specified relatively complex and costly conventional FR-4 multi-layer test boards with plated through holes and high pin counts. Assembly was time-consuming; board rejects were too high; and bad boards had to be scrapped. Especially troublesome was an intermittent electrical ìopenî problem. This was due to solder from the preforms used on an adapter in the upper through hole board running too far down the extended-length male pins used to plug into a socket on a lower PC board.

The solution devised by AIC involves the innovative application of their patented BGA Socket Adapter System in an existing, molded PGA wafer. The result of combining these proven technologies is a surface mount, interstitial pin grid array (PGA) connector. This custom SMT PGA Socket Adapter System:

• Enables the test boards to be produced with fewer layers due to SMT design.
• Eliminates the need for plated through holes.
• Provides a corporate test board solution.
• Allows more efficient, cost-effective production.

For this application, AIC employs a two-piece PGA connector system (an adaptation of a standard AIC design), comprised of a molded liquid crystal polymer (LCP) socket incorporating 3-finger low-force, gold-plated beryllium copper contacts, and an FR-4 adapter incorporating screw-machined, gold-plated brass pins. Both the socket and adapter feature the companyís exclusive eutectic solder ball terminals for superior processing yields.

The socket and adapter are reflow soldered to the circuit boardís surface mount pads using BGA solder balls. This alleviates the need to do wave soldering, eliminates the electrical ìopenî problem previously caused by solder running down the through hole pins, and also permits boards to be reworked if necessary without scrapping them. AICís use of surface mount PGA connectors to facilitate board-to-board connections thus enables the test system manufacturer to simplify assembly, reduce manufacturing costs, enhance product reliability, and increase the yield of good boards by as much as 20% compared to the original production method.