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One-Step Brazing Assembly for Multi-Layer Ceramic Modules

IP.com Disclosure Number: IPCOM000112875D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 112K

Publishing Venue

IBM

Related People

Miersch, E: AUTHOR

Abstract

A technique is described whereby power distribution limitations are reduced through the use of a one-step brazing assembly for use in multilayer ceramic modules.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 51% of the total text.

One-Step Brazing Assembly for Multi-Layer Ceramic Modules

      A technique is described whereby power distribution limitations
are reduced through the use of a one-step brazing assembly for use in
multilayer ceramic modules.

      Typically, power distribution in integrated circuit packages
has become more difficult as the current requirements increase with a
minimal voltage drop.  For example, if 1,000 amperes must be
distributed with a DC drop of less than 25 mV, the resulting
integrated resistance of the power distribution system must be less
than 2.5*10&&sup<-5>.  ohms.  In general, the amount of
power-distributing metal has to be increased, thereby requiring a
metal carrier.  However, the metal carrier is generally packaged
using thin film lines as chip interconnections.  In thick film
technologies, such as MultiLayer Ceramic (MLC) devices, the power
distribution limitations are due to high power bipolar chips, with a
DC power of up to 100 watts.

      .sp To increase the power distribution capability, the concept
described herein provides a sequence of pressing steps to provide
additional metal at the module itself.  So as to not block the chip
area with power busses on the module, power distribution planes are
used in the pin area.  These power planes have to be supplied from
the side of the module by thick power copper bars, connected to the
power supply.  Potentials like V sub R and V sub EE [*], with less
current flow, can but must not) be supplied by the board as compared
with the conventional pin-in-hole technology.

      However, four power planes for the four potentials are
conceivable.  The power pins and the signal pins have to be elongated
since they have to read through the additional power supply planes
down to the connectors of the board, as shown in the Figure.  One of
the problems, which requires solving, is in conjunction with the
additional power planes.  It is that these planes must be brazed to
the ceramic module so that the thermal expansion coefficients to the
ceramic and the power planes can be matched.  This can be achieved by
using, e.g., appropriate Copper-Invar-Copper (CuICu) sheets or other
expansion matched metal structures.  Also, the entire concept must be
compatible with the manufacturing requirements of the MLC module.

      The following fabrication process sequence is designed to
satisfy the boundaries, as discussed above:

1.  The CuICu planes have to be punched or drilled so that each
    module pin fits into its hole in the CuICu planes without
    touching the sheets.  A hole clearance has to be provided.

2.  There are two types of pins (thru-pins and power-plane pins), but
    every pin head side facing the power planes has to be separated
    from the power planes by a dielectric of equal size, either a
    coating, e.g., polyerathane, glass, or ceramic, of the top
    surface of the last power plane, a coating of the lower pin head
   ...