Apparatus and method of stacking die on a substrate

Details Apparatus and method of stacking die on a substrate Apparatus and method of stacking die on a substrate

2000-04-07

2002-01-29

Picard, Leo P. (Department: 2841)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C361S764000, C361S723000, C361S773000, C361S760000, C257S723000, C257S724000, C257S784000, C174S050510, C174S050510, C174S050510

Reexamination Certificate

active

06343019

ABSTRACT:

TECHNICAL FIELD
The present invention relates to the packaging of microelectronic devices. More particularly, the invention relates the single level packaging of silicon wafer die on a substrate, such as a circuit board.
BACKGROUND OF THE INVENTION
Conventional fabrication of a microelectronics package involves two levels of packaging. With reference to
FIG. 1
, at the first level an integrated circuit die
20
is mounted to a lead frame
5
, usually by an adhesive. Bonding pads
26
on the die are connected by bonding wires
28
to respective terminals
30
on the lead frame
5
. The lead frame
5
and die
20
are then encapsulated by cover
7
to protect the die
20
and the bonding wires
28
. The encapsulated lead frame and die thus constitute a first level of packaging. The encapsulated die and lead frame are mounted to a printed circuit board to create the second level of packaging. The lead frame may be mounted to the printed circuit board by way of solder reflow techniques or through the use of a socket mounted to the printed circuit board which is designed to receive the leads of the lead frame.
Recently, die have been mounted directly to the printed circuit board, thus eliminating the lead frame and the first level of packaging. Mounting directly to the circuit board decreases the length of the various electrical conductors such as leads and bonding wires, thus increasing the speed at which the chip can operate.
FIG. 2
shows a conventional die
20
mounted directly to the circuit board
10
and secured thereto by suitable means such as by an adhesive. The die
20
has a set of bonding pads
26
which are located on one surface of the die
20
. As shown in
FIG. 2
, the die
20
may be mounted with the bonding pads
26
of the die facing away from the surface of the circuit board
10
to which the die
20
is mounted. This type of arrangement is commonly referred to as conventional chip-on-board (COB).
FIG. 3
shows a die
20
′ mounted directly to a substrate, such as circuit board
10
. The die
20
′ has a set of bonding pads
26
′ which are located on the bottom surface of the die
20
′. As is shown in
FIG. 3
, the die
20
′ may be mounted with the bonding pads
26
′ of the die
20
′ facing the surface of a substrate such as the printed circuit board
10
′ to which the die
20
′ is being mounted. This type of arrangement is commonly referred to as flip chip. It is customary to provide a layer of material, known as a glob
46
top over the die
20
′ to hermetically seal the die
20
′. The glob top
46
serves as a chemical insulator protecting the die
20
′ from humidity, oxidation and other harmful elements. The glob top
46
also protects the die
20
′ mechanically and relieves mechanical stress in the die
20
′.
While recent changes in the fabrication of microelectronics packages have resulted in a decrease in package size, further decreases are desired. It is also desirable to shorten the bonding wire lengths used to electrically connect the die to the circuit board. Increased assembly yield and operational speed result from using shortened bonding wires. It is also desirable to minimize the thickness of the resulting microelectronics package. Package thickness is important in many space sensitive applications.
SUMMARY OF THE INVENTION
The invention of the present application stacks multiple die on top of one another. The stacked die may or may not be partially or fully recessed into a first recess formed in a first surface of a substrate, such as a circuit board. The first recess may have a stepped cross-section to accommodate die of various sizes.
An aperture may be formed in the first recess, extending through the substrate for allowing wire bonding to a second surface of the substrate. Thus, a first die which is spaced relatively interiorly of a second die may be wire bonded through the aperture to terminals located on the second surface of the substrate. The second die may be wire bonded to terminals located on the first surface of the substrate.
In another exemplary embodiment of the invention, a second recess is formed in the second surface of the substrate. The terminals are located within the recessed portion of the second surface.
Stacking multiple die on a single substrate will greatly increase the space available on the circuit board for the addition of other components. Mounting the die in a recess formed in the substrate will reduce the thickness of the resulting microelectronics package. Fabricating a set of terminals on a surface opposed to the surface on which the die is mounted can shorten the lengths of the bonding wires which connect the die to the substrate. Locating a set of terminals in a second recess formed in the second surface of the substrate will also reduce the thickness of the package and further shorten the length of the bonding wires.


REFERENCES:
patent: 5412538 (1995-05-01), Kikinis et al.
patent: 5528222 (1996-06-01), Moskowitz et al.
patent: 5566441 (1996-10-01), Marsh et al.
patent: 5600175 (1997-02-01), Orthmann
patent: 5652462 (1997-07-01), Matsunaga et al.
patent: 5661339 (1997-08-01), Clayton
patent: 5682143 (1997-10-01), Brady et al.
patent: 5696395 (1997-12-01), Tseng
patent: 5754408 (1998-05-01), Derouiche
patent: 5818698 (1998-10-01), Corisis
patent: 5875100 (1999-02-01), Yamashita
patent: 5998860 (1999-12-01), Chan et al.
patent: 0 231 937 (1987-08-01), None
patent: 0 595 549 (1994-05-01), None

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