Browse Prior Art Database

Multichip Module/ Engineering Change Scheme Using Programmable Probe Pads

IP.com Disclosure Number: IPCOM000122004D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 93K

Publishing Venue

IBM

Related People

Klink, E: AUTHOR [+2]

Abstract

This article describes a limited EC (engineering change) capability comprising a combination of programmable probe pads on the substrate and metal ECs on the chip. A small number of spare substrate pins and a larger number of spare chip I/O circuits are used to connect the potential.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Multichip Module/ Engineering Change Scheme Using Programmable Probe
Pads

      This article describes a limited EC (engineering change)
capability comprising a combination of programmable probe pads on the
substrate and metal ECs on the chip.  A small number of spare
substrate pins and a larger number of spare chip I/O circuits are
used to connect the potential.

      In some cases, the large number of EC pads for chip I/Os cannot
be supported on the surface of multichip carriers.  To do this
satisfactorily, large and complex substrates would be required.
However, such substrates would not only increase the cost of
multichip carriers but also impair the electrical characteristics.
Signal line capacitances and loop inductances increase, for example,
with size, signal line length, and higher layer count.

      The invention replaces the EC pads by a limited number of probe
pads (40 per chip site) which are implemented on the modules (Fig. 1)
for engineering tests.  Such probe points do not increase the
substrate size.  They are used to test internal bus structures which
are not connected to pins.  The probe pads are programmable and,
therefore, described by EDS (engineering design system) in the
physical substrate design.

      Spare substrate pins and spare chip I/O circuits are used to
connect the potential.  The number of spare substrate pins is
generally much lower than that of the spare chip I/Os.

      Fig. 1 shows the probe pad arrangement of the top surface of
the multichip module.  Approximately forty signal pads are
distributed on each chip site.

      Some prob...