Browse Prior Art Database

Heatsinking Device for Wirebonded Direct Chip Attach of Integrated Circuit

IP.com Disclosure Number: IPCOM000108339D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 5 page(s) / 191K

Publishing Venue

IBM

Related People

Costello, TJ: AUTHOR [+6]

Abstract

Disclosed is a method for the improvement of heat sinking wirebonded direct chip attached (DCA) integrated circuits (ICs) to a printed circuit board (PCB or card). The example shown is based on the use of industry standard 'FR-4' PCB technology.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 42% of the total text.

Heatsinking Device for Wirebonded Direct Chip Attach of Integrated Circuit

       Disclosed is a method for the improvement of heat sinking
wirebonded direct chip attached (DCA) integrated circuits (ICs) to a
printed circuit board (PCB or card).  The example shown is based on
the use of industry standard 'FR-4' PCB technology.

      The use of a metal or ceramic 'core' provides a mounting
surface for the IC as well as an efficient thermal conduction path to
the heat spreading plane(s) within the card.

      Thermal performance of this method is compared to an
alternative method.

      This invention involves the fabrication of a PCB and the
assembly of heat sinking cores and DCA ICs.  The intent is to apply
current standard PCB processes to a new application at minimal cost.

      The unique part of this assembly is called the 'core', which
provides a surface on which to mount the IC die and an enhanced
thermal conduction path to the card's heat spreading plane(s).  The
value of using this card and core assembly is to retain industry
standard wiring and process techniques and adapt them to an
alternative package type (DCA) for increased density and enhanced
thermal performance.

      The heat path discussed here is the one from the IC die through
the core to the through-plated hole and to the spreading plane within
the card.  To maintain a low junction temperature within the IC, an
efficient heat path must be provided having the characteristic of low
thermal resistance and large heat dissipation.

      The following is a list of the components and the assembly
steps:
1.   The Core
      This invention involves the use of a metal or ceramic core as
pictured in Fig. 1.  This core could be a shell or a solid.
      The shape of the core is generally a plate on top of a
cylindrical section.  The plate is sized for the dimensions of the IC
die (generally in the range of 5 to 13 mm on a side).  The cylinder
is sized for insertion into the card.  The length of the cylinder may
be such that it is flush with, or extends beyond, the back surface of
the card.
2.   The Card
      Refer to Fig. 2.
      The preparation of the card involves current industry standard
processes and is outlined below for completeness.
      The preparation of the card involves a design with multiple
planes, where at least one plane is available as a heatsink plane.
This plane may be shared as a voltage plane or it may be allowed to
be electrically isolated from the remainder of the card.  The plane
should be solid or a grid structure perforated only as necessary for
wiring via holes.
      For low wattage applications, the thickness of the plane can be
in the standard range of 1 to 3 ounce copper, with the weight
ultimately determined by thermal analysis of the card and its
intended environment.  Thinner copper is preferable for card assembly
because it is easier to solder.
      A round hole...