Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – Insulating material
Reexamination Certificate
2002-08-02
2004-04-13
Mai, Son L. (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
Insulating material
C707S718000, C707S719000, C707S778000, C707S787000, C707S796000
Reexamination Certificate
active
06720649
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to semiconductor packages, and more particularly, to a semiconductor package with a heat dissipating structure.
BACKGROUND OF THE INVENTION
Ball grid array (BGA) semiconductor packages are mainstream package products in the light of providing a sufficient amount of I/O (input/output) connections for use with semiconductor chips that incorporate high density of electronic elements and electronic circuits. As such a highly-integrated chip operates to consequently produce relatively more heat, it is thereby important to promptly remove the heat from the chip; otherwise, heat accumulation in the chip would undesirably damage electrical performances and reliability of package products. Moreover, for protecting internal components of the semiconductor package against external contamination, it usually forms an encapsulant that encapsulates the chip and other conductive elements such as bonding wires. The encapsulant is made of a resin material with poor thermal conductivity (coefficient of thermal conductivity around 0.8 w/m°K); therefore, the chip-generated heat would not be efficiently dissipated to the atmosphere through the encapsulant; this would thereby adversely affect performances and lifetime of the chip by virtue of heat accumulation.
In response to the above heat-dissipation problem, there is adopted a heat dissipating structure in the BGA semiconductor package for facilitating dissipation of heat generated from the chip. However, this heat dissipating structure is embedded in the encapsulant, such that the chip-generated heat still needs to pass through the encapsulant for dissipation. Therefore, this structural arrangement cannot achieve satisfactory improvement in heat dissipating efficiency for the semiconductor package.
Accordingly, U.S. Pat. No. 5,977,626 discloses a semiconductor package with a heat dissipating structure being partly exposed to the atmosphere and also directly contacting with a chip. As shown in
FIGS. 5 and 6
, in this semiconductor package
3
, a heat dissipating structure
33
is provided on a substrate
30
above a chip
31
mounted on the substrate
30
. The heat dissipating structure
33
comprises: a flat portion
330
having a top face
330
a
exposed to outside of an encapsulant
34
that encapsulates the chip
31
and bonding wires
32
that electrically connect the chip
31
to the substrate
30
; and a single encircled support portion
331
peripherally situated at the flat portion
330
and extending downwardly from a bottom surface
330
b
of the flat portion
330
to be attached to the substrate
30
, wherein the flat portion
330
and the encircled support portion
331
integrate to form a receiving space
35
where internal components such as the chip
31
, bonding wires
32
and passive components (not shown) are placed. The encircled support portion
331
is integrally formed with a laterally-extending contact portion
332
at a bottom position thereof, and the contact portion
332
may be provided with a plurality of protruding portions
333
respectively extending downwardly to be attached to the substrate
30
. Moreover, on the bottom surface
330
b
of the flat portion
330
there is formed a protrusion
334
extending to abut against an active surface
310
of the chip
31
. This allows heat generated by the chip
31
during operation to be transmitted through the protrusion
334
to the exposed top face
330
a
of the flat portion
330
by which the heat can be dissipated to the atmosphere, so as to provide excellent heat dissipating efficiency for the semiconductor package
3
.
However, the above semiconductor package
3
has significant drawbacks. In compliance with low profile packaging technology and high integration of chip development, substrates are preferred to be down-sized nearly to chip scale, and incorporated with sufficient conductive elements such as bonding wires required for accommodating highly-integrated chips with densely-arranged electronic elements or circuits. As a result, the above heat dissipating structure
33
is considered to occupy too much space on the substrate
30
in a manner that, the receiving space
35
embraced by the flat portion
330
and the single encircled support portion
331
with integrally-formed contact portion
332
, makes all internal components of the semiconductor package
3
position restrictedly enclosed in the receiving space
35
. Thereby, the bonding wires
32
, passive components or other electronic components (not shown) can only be disposed on the substrate
30
at area within coverage of the heat dissipating structure
33
in the receiving space
35
. This drawback makes the semiconductor package
3
with the heat dissipating structure
33
hardly applied for accommodating highly-integrated chips that require a large amount of active and passive components as well as conductive elements to be comfortable situated on the substrate
30
for achieving desirable operational and electrical performances.
Further due to the heat dissipating structure
33
being located outside area for incorporating electronic components on the substrate
30
, in another aspect, the substrate
30
may need to be increasingly sized in order to dispose a sufficient number of active and passive components as well as conductive elements on the substrate
30
; this would make the substrate
30
considerably larger in size than the chip
31
, thereby unfavorable to profile miniaturization.
SUMMARY OF THE INVENTION
An objective of the present invention is to provide a semiconductor package with a heat dissipating structure, wherein the heat dissipating structure is arranged in a manner not to interfere with layout of a chip, bonding wires or passive components mounted on the substrate, thereby improving flexibility in component arrangement in the semiconductor package.
Another objective of the invention is to provide a, semiconductor package with a heat dissipating structure, so as to reduce surface area of a substrate occupied by the heat dissipating structure, and thus to increase layout area on the substrate for accommodating bonding wires and passive components.
A further objective of the invention is to provide a semiconductor package with a heat dissipating structure, so as to improve heat dissipating efficiency of the semiconductor package.
To achieve the above and other objectives, the present invention proposes a semiconductor package with a heat dissipating structure, comprising: a substrate; at least a chip mounted on the substrate and electrically connected to the substrate via a plurality of bonding wires; a heat dissipating structure comprising a flat portion, and a plurality of support portions formed at edges of the flat portion for supporting the flat portion in position above the chip, wherein the support portions are mounted at predetermined area on the substrate to be free of interference with arrangement of the chip and the bonding wires, and the support portions are arranged to form a space embraced by adjacent support portions and the flat portion, which space is dimensioned to accommodate the bonding wires and to allow the bonding wires to pass through the space to reach area on the substrate outside coverage of the heat dissipating structure; an encapsulant formed on the substrate for encapsulating the chip and the bonding wires; and a plurality of solder balls implanted on the substrate and exposed to outside of the encapsulant.
In the above package structure, the flat portion of the heat dissipating structure is elevated above the chip by the support portions and forms a predetermined height difference with respect to the substrate, wherein the height difference is at least corresponding to height of wire loops of the bonding wires. Therefore, part of bond fingers where the bonding wires are bonded can be formed on the substrate at area outside the coverage of the heat dissipating structure, allowing the corresponding bonding wires to pass through the space embraced by adjacent support portions and the flat portion a
Corless Peter F.
Edwards & Angell LLP
Huynh Andy
Jensen Steven M.
Mai Son L.
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