Browse Prior Art Database

Flip Chip Carrier Assembly for Improved Thermal Performance

IP.com Disclosure Number: IPCOM000113092D
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Sholtes, TA: AUTHOR [+2]

Abstract

As shown in Fig. 1, conventional thin film chip carrier assembly methods attach the backside of a thin film polyimide 2 by means of low melt solder joints 3, which in turn contact a printed circuit card 4 through solder balls 5.

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Flip Chip Carrier Assembly for Improved Thermal Performance

      As shown in Fig. 1, conventional thin film chip carrier
assembly methods attach the backside of a thin film polyimide 2 by
means of low melt solder joints 3, which in turn contact a printed
circuit card 4 through solder balls 5.

      As shown in Fig. 2, a one-sided carrier metallurgy with
polyimide vias 6 are used to obtain the inverted or flipped chip.
Polyimide film 4 is mounted on a circuit card 2 with solder joints 3
extending through vias 6.  The chip 1 is mounted on top of the
polyimide film 4.

      The polyimide film 4 is attached to the card 2 by first placing
an Outer Lead Bond (OLB) pad 7 (Fig. 3) around the vias 6, as shown
in the cross section view.  The pads 7 are bumped with solder, using
solder paste screening or wave solder, to attach the polyimide layer
to the card.

      A heat sink 8 is placed over the chip 1, as shown in Fig. 2,
which makes direct contact with the chip 1.  Thermal grease or
thermally conductive adhesive (not shown) is used between the heat
sink and the chip.  A thin film chip carrier (Fig. 4) is aligned and
placed on the card 2.  The carrier is then held against and reflowed
to the card.

      Another method is to use a double sided chip carrier metallurgy
to obtain a flipped chip, or polyimide etched away from backside, as
shown in Fig. 5.