Probe assembly with controlled impedance spring pin or resistor tip spring pin contacts

In a probe assembly for probing a plurality of target signals upon a work circuit assembly with a respectively plurality of spring pin contacts electrically connected to a corresponding member of a respective plurality of transmission lines formed upon and carried by a printed circuit assembly that when urged against the work circuit assembly compresses each spring pin contact into electrical contact with a respective target signal in the plurality thereof, the improvement comprising:

• the plurality of spring pin contacts being arranged in a row;
• the plurality of transmission lines being formed by respective signal traces separated from a ground plane by the thickness of an intervening dielectric layer;
• the intervening dielectric layer having a first edge parallel to a plane formed by the work circuit assembly;
• the ground plane having an extended portion that extends beyond the first edge of the intervening dielectric layer in a direction toward the work circuit assembly by a selected first distance bounded by a second edge;
• a housing portion of each spring pin contact being in electrical contact with the signal trace of its associated transmission line and also having an end proximate the first edge of the intervening dielectric layer;
• a plunger portion of each spring pin contact extending out of a respective housing portion, over the extended portion of the ground plane and beyond the second edge by a selected second distance;
• and
• wherein the characteristic impedance of a transmission line respectively formed by each plunger portion and the extended portion of the ground plane is approximately the same as the characteristic impedance of each respective transmission line formed by each signal trace and the ground plane.

In a probe assembly for probing first and second pluralities of target signals upon a work circuit assembly with respective first and second pluralities of spring pin contacts electrically connected to a corresponding members of respective first and second pluralities of transmission lines formed upon and carried by respective first and second sides of a printed circuit assembly that when urged against the work circuit assembly compresses each spring pin contact into electrical contact with a respective target signal in the respective pluralities thereof, the improvement comprising:

• the first plurality of spring pin contacts being arranged in a first row disposed on the first side of the printed circuit assembly;
• the first plurality of transmission lines being formed by respective first signal traces separated from a first ground plane by the thickness of a first intervening dielectric layer;
• the first intervening dielectric layer having a first edge parallel to a plane formed by the work circuit assembly;
• the first ground plane having an extended portion that extends beyond the first edge of the first intervening dielectric layer in a direction toward the work circuit assembly by a selected first distance bounded by a second edge;
• a housing portion of each spring pin contact in the first plurality thereof being in electrical contact with the first signal trace of its respective transmission line in the first plurality thereof and also having an end proximate the first edge of the first intervening dielectric layer;
• a plunger portion of each spring pin contact in the first plurality thereof extending out of a respective housing portion, over the extended portion of the first ground plane and beyond the second edge by a selected second distance;
• wherein the characteristic impedance of a transmission line respectively formed by each plunger portion extending over the extended portion of the first ground plane is approximately the same as the characteristic impedance of each respective transmission line in the first plurality thereof formed by each first signal trace therein and the first ground plane;
• the second plurality of spring pin contacts being arranged in a second row disposed on the second side of the printed circuit assembly;
• the second plurality of transmission lines being formed by respective second signal traces separated from a second ground plane by the thickness of a second intervening dielectric layer;
• the second intervening dielectric layer having a third edge parallel to the plane formed by the work circuit assembly;
• the second ground plane having an extended portion that extends beyond the third edge of the second intervening dielectric layer in a direction toward the work circuit assembly by a selected third distance bounded by a fourth edge;
• a housing portion of each spring pin contact in the second plurality thereof being in electrical contact with the second signal trace of its respective transmission line in the second plurality thereof and also having an end proximate the third edge of the second intervening dielectric layer;
• a plunger portion of each spring pin contact in the second plurality thereof extending out of a respective housing portion, over the extended portion of the second ground plane and beyond the third edge by a selected fourth distance;
• and
• wherein the characteristic impedance of a transmission line respectively formed by each plunger portion extending over extended portion of the second ground plane is approximately the same as the characteristic impedance of each respective transmission line in the second plurality thereof formed by each second signal trace therein and the second ground plane.

In a probe assembly for probing a plurality of target signals upon a work circuit assembly with a respective plurality of resistor tip spring pin contacts, each one of which is electrically connected to a corresponding member of a respective plurality of transmission lines formed upon and carried by a printed circuit assembly that when urged against the work circuit assembly compresses each resistor tip spring pin contact into electrical contact with a respective target signal in the plurality thereof, the improvement comprising:

• the plurality of resistor tip spring pin contacts being arranged in a row;
• the plurality of transmission lines being formed by respective signal traces separated from a ground plane by the thickness of an intervening dielectric layer;
• the intervening dielectric layer having a first edge parallel to a plane formed by the work circuit assembly;
• the ground plane having an extended portion that extends beyond the first edge of the intervening dielectric layer in a direction toward the work circuit assembly by a selected first distance bounded by a second edge;
• a housing portion of each resistor tip spring pin contact being in electrical contact with the signal trace of its associated transmission line and also having an end proximate the first edge of the intervening dielectric layer;
• a plunger portion of each resistor tip spring pin contact extending out of a respective housing portion, over the extended portion of the ground plane and beyond the second edge by a selected second distance;
• and
• wherein the characteristic impedance of a transmission line respectively formed by each plunger portion and the extended portion of the ground plane is approximately the same as the characteristic impedance of each respective transmission line formed by each signal trace and the ground plane.

In a probe assembly for probing first and second pluralities of target signals upon a work circuit assembly with respective first and second pluralities of resistor tip spring pin contacts electrically connected to a corresponding members of respective first and second pluralities of transmission lines formed upon and carried by respective first and second sides of a printed circuit assembly that when urged against the work circuit assembly compresses the resistor tip spring pin contact into electrical contact with a respective target signal in the respective pluralities thereof, the improvement comprising:

• the first plurality of resistor tip spring pin contacts being arranged in a first row upon the first side of the printed circuit assembly;
• the first plurality of transmission lines being formed by respective first signal traces separated from a first ground plane by the thickness of a first intervening dielectric layer;
• the first intervening dielectric layer having a first edge parallel to a plane formed by the work circuit assembly;
• the first ground plane having an extended portion that extends beyond the first edge of the first intervening dielectric layer in a direction toward the work circuit assembly by a selected first distance bounded by a second edge;
• a housing portion of each resistor tip spring pin contact in the first plurality thereof being in electrical contact with the first signal trace of its respective transmission line in the first plurality thereof and also having an end proximate the first edge of the first intervening dielectric layer;
• a plunger portion of each resistor tip spring pin contact in the first plurality thereof extending out of a respective housing portion, over the extended portion of the first ground plane and beyond the second edge by a selected second distance;
• wherein the characteristic impedance of a transmission line respectively formed by each plunger portion extending over the extended portion of the first ground plane is approximately the same as the characteristic impedance of each respective transmission line in the first plurality thereof formed by each first signal trace therein and the first ground plane;
• the second plurality of resistor tip spring pin contacts being arranged in a second row disposed upon the second side of the printed circuit assembly;
• the second plurality of transmission lines being formed by respective second signal traces separated from a second ground plane by the thickness of a second intervening dielectric layer;
• the second intervening dielectric layer having a third edge parallel to the plane formed by the work circuit assembly;
• the second ground plane having an extended portion that extends beyond the third edge of the second intervening dielectric layer in a direction toward the work circuit assembly by a selected third distance bounded by a fourth edge;
• a housing portion of each resistor tip spring pin contact in the second plurality thereof being in electrical contact with the second signal trace of its respective transmission line in the second plurality thereof and also having an end proximate with the third edge of the second intervening dielectric layer;
• a plunger portion of each resistor tip spring pin contact in the second plurality thereof extending out of a respective housing portion, over the extended portion of the second ground plane and beyond the third edge by a selected fourth distance;
• and
• wherein the characteristic impedance of a transmission line respectively formed by each plunger portion extending over extended portion of the second ground plane is approximately the same as the characteristic impedance of each respective transmission line in the second plurality thereof formed by each second signal trace therein and the second ground plane.