Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – With dam or vent for encapsulant
Reexamination Certificate
2000-08-15
2003-03-11
Paladini, Albert W. (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
With dam or vent for encapsulant
C257S783000, C257S784000, C257S787000, C174S260000, C438S118000, C438S126000, C264S272170
Reexamination Certificate
active
06531763
ABSTRACT:
TECHNICAL FIELD
The present invention relates to apparatus and methods of semiconductor component packaging using interposers having an encapsulant fill control feature.
BACKGROUND OF THE INVENTION
Semiconductor chips (or die) may be mounted to circuit boards or other electronic components in several ways. In a typical ball grid array (BGA) or fine ball grid array (FBGA) assembly
30
as shown in
FIG. 1
, a die
10
is attached to an interposer
22
having a plurality of conductive leads
18
. The die may be attached to the interposer using, for example, strips of adhesive
12
(see FIG.
1
), an adhesive layer (e.g. epoxy), eutectic bonding, or other suitable methods. Typically, the die
10
includes a plurality of conductive terminals
14
(or bond pads) that are electrically coupled to corresponding contact pads
16
on the interposer
22
, thereby coupling the internal circuitry of the die
10
with the conductive leads
18
. The conductive terminals
14
may be attached to the contact pads
16
in a variety of ways, including by bond wires
26
(see FIG.
1
), solder reflow, conductive adhesives, or other suitable methods. The conductive leads
18
of the interposer
22
fan out from the die
10
and may be coupled to other electronic components, such as printed circuit boards, electronics modules, and the like. Solder balls
24
(
FIG. 1
) may be attached to the ends of the conductive leads
18
for attaching the interposer
22
to other electronic components. Electrical signals may then be transmitted from, for example, a circuit board through the conductive leads of the interposer to the die, and vice versa. Typical BGA assemblies are described, for example, in U.S. Pat. No. 5,086,558 to Grube et al, U.S. Pat. No. 5,258,648 to Lin, and U.S. Pat. No. 4,617,730, incorporated herein by reference.
As shown in
FIG. 1
, it is customary to provide one or more encapsulant layers
28
over the die
10
, conductive terminals
14
, contact pads
16
, and other sensitive areas of the FBGA assembly
30
. The encapsulant layer
28
hermetically seals the assembly, insulating and protecting the sensitive portions of the assembly from humidity, oxidation, and other harmful environmental elements. To reduce stresses that may be induced in the FBGA assembly
30
during thermal cycling, the encapsulant layer
28
may be composed of a soft, compliant polymeric material, such as silicone rubber or other castable elastomer having a relatively low modulus of elasticity. Alternate materials for the encapsulant material are described, for example, in U.S. Pat. No. 5,956,605 issued to Akram and Farnworth, incorporated herein by reference.
FIG. 2
is a side elevational cross-sectional view of the FBGA assembly
30
of
FIG. 1
engaged with an encapsulant supplier
40
and a mold
42
. The mold
42
includes a lower portion
46
and an upper portion
48
. The lower and upper portions
46
,
48
have inner surfaces that are spaced apart from the FBGA assembly
30
and are shaped to form the encapsulant layers
28
(FIG.
1
). The encapsulant supplier
40
may be integrally formed with the upper half
48
, as shown in
FIG. 2
, or may be a separate component.
After the FBGA assembly
30
is positioned within the mold
42
, an encapsulant material
50
may be flowed through the encapsulant supplier
40
. As it enters the mold
42
, the flow of encapsulant material
50
may divide into a first stream
52
and a second stream
54
. The first stream
52
may turn and flow over an outer portion of the die
10
between the die
10
and the upper half
48
of the mold
42
. The second stream
54
may flow through an opening between the die
10
and the interposer
22
and into the space between the FBGA assembly
30
and the lower half
46
of the mold
42
, surrounding the bond pads
14
, the bond wires
26
, and the contact pads
16
.
Ideally, the first stream
52
substantially fills the space between the FBGA assembly
30
and the upper half
48
of the mold
42
, and the second stream
54
substantially fills the space between the FBGA assembly
30
and the lower half
46
of the mold
42
. After the fill procedure is complete, the encapsulant material
50
may be cured, such as by heating, cooling, or exposing the encapsulant material to curing agents, and the mold
42
may be removed. These operations are typically performed simultaneously on numerous FBGA assemblies that are joined together as a single unit along lateral edges of the interposers
22
. After curing the encapsulant materials, the FBGA assemblies may be singulated into discrete packages.
One problem with the above-described FBGA assembly
30
is that the encapsulant material may not completely fill the space between the FBGA assembly
30
and the mold
42
, particularly in the space surrounding the bond pads
14
, the contact pads
16
, and the bond wires
26
. To provide good thermal conduction and mechanical strength, the space surrounding the bond pads
14
, the contact pads
16
, and the bond wires
26
should be void-free. Moisture or contaminants may collect in the voids, and may cause the die to come loose from the interposer, or may cause other malfunctions of the microelectronics package.
SUMMARY OF THE INVENTION
The present invention is directed to apparatus and methods of semiconductor component packaging using interposers having an encapsulant fill control feature. In one aspect, an interposer includes a substrate having a first surface proximate a region adapted to be occupied by a semiconductor component, and a fill control feature projecting from the first surface toward the region. The fill control feature is positioned at least partially between the region and the substrate and is sized to at least partially block an opening between a semiconductor component positioned within the region and the first surface. As an encapsulant material is flowed about the semiconductor component, the fill control feature at least partially diverts the encapsulant material from entering the opening. The at least partially diverted encapsulant material may then substantially surround the semiconductor component, after which the encapsulant material may substantially fill a space between the semiconductor component and the interposer. Because the fill control feature diverts a portion of the encapsulant material to cause the space surrounding the semiconductor component to substantially fill before the space between the semiconductor component and the interposer, the fill control feature may reduce the occurrence of voids and may otherwise improve the fill of the encapsulant material about the semiconductor component and the interposer.
In an alternate aspect, the semiconductor component may be attached to the interposer by a pair of adhesive strips, the opening being formed between the semiconductor component, the interposer, and the adhesive strips. Alternately, the semiconductor component may be attached to the interposer by a pair of conductive bumps, the opening being formed between the conductive bumps. In other aspects, the interposer may include a plurality of fill control features.
REFERENCES:
patent: 4617730 (1986-10-01), Geldermans et al.
patent: 4648179 (1987-03-01), Bhattacharyya et al.
patent: 4788767 (1988-12-01), Desai et al.
patent: 5086558 (1992-02-01), Grube et al.
patent: 5258648 (1993-11-01), Lin
patent: 5384955 (1995-01-01), Booth et al.
patent: 5777391 (1998-07-01), Nakamura et al.
patent: 5956605 (1999-09-01), Akram et al.
patent: 6002180 (1999-12-01), Akram et al.
patent: 6157080 (2000-12-01), Tamaki et al.
Bolken Todd O.
Corisis David J.
Dorsey & Whitney LLP
Micro)n Technology, Inc.
Vigushin John B.
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