Browse Prior Art Database

Holder for Stacked MLC with Good Electrical Performance

IP.com Disclosure Number: IPCOM000113778D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 95K

Publishing Venue

IBM

Related People

Lamarche, P: AUTHOR [+2]

Abstract

Disclosed hereinbelow is a technic to allow a good electrical performance for stacked MLC. The problem to solve is to build stacked MLC (for density) without impacting the electrical fonctionality.

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This is the abbreviated version, containing approximately 53% of the total text.

Holder for Stacked MLC with Good Electrical Performance

      Disclosed hereinbelow is a technic to allow a good electrical
performance for stacked MLC.  The problem to solve is to build
stacked
MLC (for density) without impacting the electrical fonctionality.

      The usual way to increase the overall package density is to
directly stack two MLC is shown in Fig. 1.  The IO's and power go
from MLC to card thru a peripheral connector (lead frame for example)
because due to the bottom module traditional pins or balls from the
top one cannot be used.  The two modules are stuck on an interposer
securely screwed to the card (in Fig. 1 the screws are not shown).
This interposer is used only for mechanical reasons but has no
electrical purpose.  From an electrical point of view the inductance
loop of the supplies circuits is high because the effective
inductance of the package is a combination of:
  o  wire bonding (connector part); and,
  o  long distance inside the substrate (X, Y directions) to go
     out.

      This solution is satisfactory to the extent the application
needs low switching activity.  Otherwise, the high inductance of the
package is a severe limit for the application.

      The new solution shown in Fig. 2 combines a peripheral
connector for the IO's and a supply circuit thru conductive bars.
The bottom surface of the MLC is patterned with metallic lands
connected thru vias to internal planes and chip.  Now, the interposer
actively participates to the electrical path.  Fig. 2 shows three
conductive bars (in copper for example) for each supply (GND, VDD
,VT).  Any combination thereof may be investigated.  Fig. 3 shows a
cross sectional view of the Fig. 2 module.  The manufactur...