Double-ended sockets or termination pins allow construction of fixtures with shorter signal path lengths compared to conventional wire-wrapped designs. The shorter path length allows for improved signal integrity from the tester circuits to the Unit Under Test (UUT). Fixtures built in this manner are referred to as “wireless”. The impedance characteristics are improved, allowing greater bandwidths for analog test signals and higher vector rates for digital testing. For three probes on .100 [2.54] centers (signal between two grounds), excellent performance to more than 2 Ghz was achieved.
A double-ended socket or termination pin has a non-replaceable interface probe as its termination. This interface probe typically contacts a dedicated PCB/Interface/Translator Board on the fixture. Basic tip styles such as spherical and chisel, are offered on the bottom side probe due to the flat contact surface. Because the bottom probe is used in non-cycling applications, it will last the life of the socket. In the event that the socket is damaged or worn, the complete double-ended assembly is replaced. The top of the socket or termination pin accepts standard probes from the appropriate sized series and is replaceable, as routine maintenance requires.
When mix mounting QA’s 39mil wireless double ended sockets with 50mil, 75mil and 100mil wireless sockets, the fixture designer must take into account that the full plunger stroke of the 39mil doubled ended socket is only .125 [3.18] stroke versus the .150 [3.81] stroke for the others. The illustration to the right shows a typical fixture layout where the interface/translator board is designed to stroke the interface plunger at the recommended .100 [2.54] stroke across all probe series. The distance from the top of the interface/translator board to the interface tube will be .025 [.64] on the 39mil and .050 [1.27] for the other sizes. Ultimately, the set height and board layout is dependent upon the specific fixture design and application. QA recommends a guide plate to help maintain alignment between the interface probe and the contacts on the dedicate PCB/Interface/Translator board. Below shows the advantage of using a chamfered guide hole on the top of this plate.