Browse Prior Art Database

Molded Flip-Chip or Wire-Bond Electronic Package

IP.com Disclosure Number: IPCOM000119021D
Original Publication Date: 1997-Oct-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 107K

Publishing Venue

IBM

Related People

Johnson, EA: AUTHOR

Abstract

Disclosed is a molded plastic, ball-grid array, electronic package that leaves a portion of the chip unencapsulated for improved cooling. Both wire-bonded and flip-chip packages can be produced in this manner. A wire-bonded package is shown in the upper portion of Fig. 1, excluding solder balls that are typically located on the substrate's bottom surface in a defined pattern.

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Molded Flip-Chip or Wire-Bond Electronic Package

      Disclosed is a molded plastic, ball-grid array, electronic
package that leaves a portion of the chip unencapsulated for improved
cooling.  Both wire-bonded and flip-chip packages can be produced in
this manner.  A wire-bonded package is shown in the upper portion of
Fig. 1, excluding solder balls that are typically located on the
substrate's bottom surface in a defined pattern.

      Molded plastic ball-grid array packages are usually built with
a transfer mold process that totally encapsulates the chip.  For
wire-bond applications, this plastic encapsulant is relatively thick
so that the loops of the wires, which attach the chip to the
substrate, are  protected.  The encapsulant typically has a
conductivity of .1 to .5 W/m/degrees K and prevents effective cooling
through the body of the package; heat flows through the balls
instead.  By molding the encapsulant so that the active surface of
the chip is left free, cooling  is improved.  Further improvement can
be made by attaching a heat-sink  directly to the chip as illustrated
in Fig. 2.

      Flip-chip packages do not require such thick layers of
encapsulant but typically dissipate much more power.  In this case,
it is the back, or inactive, side that is exposed.  The conductivity
of silicon is, however, relatively high and a significant amount of
heat can be conducted out of the package if a heat-sink is attached
as already described.