Browse Prior Art Database

Process to Terminate Co-Ax Cables to 1 mm/0.050" Pitch Grid Array Pads

IP.com Disclosure Number: IPCOM000118797D
Original Publication Date: 1997-Jul-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 100K

Publishing Venue

IBM

Related People

Choudhury, A: AUTHOR [+2]

Abstract

Disclosed is a reliable method of terminating small co-axial cables to a large array of pads arranged at 1.0 mm or 0.050 in pitch. The pads are isolated from a surface ground plane. The center conductor of the co-axis soldered to the pad whereas the ground shield of the cable is easily terminated to the ground plane. The ground plane can either be wired to logic ground or the frame ground, as the case may be.

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Process to Terminate Co-Ax Cables to 1 mm/0.050" Pitch Grid Array Pads

      Disclosed is a reliable method of terminating small co-axial
cables to a large array of pads arranged at 1.0 mm or 0.050 in
pitch.  The pads are isolated from a surface ground plane.  The
center conductor of the co-axis soldered to the pad whereas the
ground shield  of the cable is easily terminated to the ground plane.
The ground plane  can either be wired to logic ground or the frame
ground, as the case may be.

      As use of Ball Grid Array/Column Grid Array/Land Grid Array
(BGA/CGA/LGA) packages increases, the need to probe the functionality
of these modules during system bring-up will require reliable
interconnect schemes that allow simultaneous access to all critical
nets.  Most packages designed today are either at 0.050 in or at 1 mm
pitch.  Such tight pitch coupled with dense packaging techniques
utilized in most sophisticated designs makes it imperative to use
small co-axial connections.  Reliable termination of small co-axial
cables to a board with large array of high density pads is neither
simple nor easy.  Further, laying out individual ground pads for
ground shield termination, in addition to the pads for center
conductor termination, is quite difficult and unreliable.

      A Printed Circuit (PC) board design with a reliable method to
terminate small co-axial cables to highly dense pads that match the
footprint of a given BGA/LGA/CGA package is being disclosed.  Fig. 1
describes the PC board design.  One side of the PC board (1a) is laid
out with pads (2) that maps the footprint of the module (BGA/CGA/LGA)
t...