Method and apparatus for implementing very high density probing (VHDP) of printed circuit board signals

Abstract

A method and apparatus are provided for implementing very high density signal probing of a printed circuit board having a pad pattern connected to signals of interest. A metal plate includes a plurality of through holes arranged in a predefined pattern that corresponds to the pad pattern on the printed circuit board. At least one signal module is inserted within a selected one of the through holes of the metal plate. Each signal module defines a coaxial connector for electrical mating engagement with a coaxial cable connector and has an embedded resistor. At least one power / ground module is inserted within a selected one of the through holes. Each power / ground module contains a high dielectric constant material between an outer conductor and a center conductor defining a capacitor. The capacitor provides a low impedance path between the metal plate and a power or ground pad of the printed circuit board.

Description

FIELD OF THE INVENTION [0001] The present invention relates generally to the data processing field, and more particularly, relates to a method and apparatus for implementing very high density signal probing of a printed circuit board. DESCRIPTION OF THE RELATED ART [0002] Many high performance computer systems and server systems rely on large-scale packaging of multiple high density interconnect modules and printed circuit boards to accommodate efficient interconnection of increasingly complex, high signal speed, integrated circuit devices within a spatial footprint. Land grid array (LGA) board, module, and connector configurations are commonly used to provide high density, mechanically loaded interconnects in the electronic packaging of a multitude of high performance board and module assemblies used in computer electronics. In the testing of a printed circuit board, for example, during the initial bring up and debugging of system hardware, access to an area of interest on the prin...

AI Technical Summary

Benefits of technology

The present invention provides a method and apparatus for very high density signal probing of a printed circuit board. The apparatus includes a metal plate with a pattern of through holes that correspond to the pad pattern on the printed circuit board. Each through hole contains a signal module with a coaxial connector for mating with a coaxial cable connector and an embedded resistor. Additionally, each through hole contains a power / ground module with a high dielectric constant material between an outer conductor and a center conductor, which creates a low impedance path between the metal plate and a power or ground pad of the printed circuit board. The method and apparatus provide a way to probe signals on printed circuit boards with high density and without negative effects on the circuit board.

Problems solved by technology

In the testing of a printed circuit board, for example, during the initial bring up and debugging of system hardware, access to an area of interest on the printed circuit board for probing or connecting to signals often presents a problem.

Probing complex computer systems for logic debug or signal integrity becomes more and more difficult because of growing bus width, higher bus speed, and very limited probe access of highly compact packaging.

Because custom flex cable designs are expensive, they represent a significant additional expense in addition to the procurement of the system PCB hardware.

The flex circuit probe is sandwiched between chip carriers and the PCB using additional and costly interposers.

However, the loading of the flex circuit probe can cause bus failure when bus speeds are above 1 GHz and when flex circuit probe lengths become large.

Another drawback of the solution is the flex circuit probe must be built in advance and specific signals being probed must be defined at the moment.

The disclosed probing method and apparatus if applied for multiple signals would consume significant wiring channels in the PCB that typically would be needed for functional wiring.

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