U.S. patent application number 10/231718 was filed with the patent office on 2004-03-04 for heat sink for automatic assembling.
Invention is credited to Erez, Shmuel, Geva, Ehood.
Application Number | 20040042177 10/231718 |
Document ID | / |
Family ID | 31946355 |
Filed Date | 2004-03-04 |
United States Patent
Application |
20040042177 |
Kind Code |
A1 |
Geva, Ehood ; et
al. |
March 4, 2004 |
HEAT SINK FOR AUTOMATIC ASSEMBLING
Abstract
The heat-sink assembly of the invention is attached to the PC
board with the use of surface mount technology. The assembly
comprises a base part or a base member soldered to the PC board and
a top part or a heat-sink member snapped-on through the central
opening of the base member by irreversibly deforming bendable lugs
which may have a radial or any other suitable shape. The bottom of
the heat-sink member may be pushed down to physical contact with
the top of the chip or to a position that leaves a space between
the bottom of the heat-sink member and the top of the chip, so that
the aforementioned space may be filled with a heat-conducting
medium. It is an option to use the base part only. If necessary, a
second heat-sink member of the same type, which could have
different dimensions, can be soldered to the PC board side opposite
to the chip. The heat sinks could be used with or without a fan. In
the case of the assembly with a fan, the deice may have an air-flow
guiding funnel formed on side portion of the base member.
Inventors: |
Geva, Ehood; (Palo Alto,
CA) ; Erez, Shmuel; (San Jose, CA) |
Correspondence
Address: |
Ehood Geva
4190 Maybell Way
Palo Alto
CA
94306
US
|
Family ID: |
31946355 |
Appl. No.: |
10/231718 |
Filed: |
August 30, 2002 |
Current U.S.
Class: |
361/705 ;
165/80.3; 257/E23.086; 257/E23.099; 361/719 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 23/467 20130101; H01L 23/4093 20130101; H01L 2924/0002
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
361/705 ;
165/080.3; 361/719 |
International
Class: |
H05K 007/20 |
Claims
1. A heat-sink assembly for removal of heat from a heat source with
which said heat-sink assembly is maintained in a heat-exchanging
contact, comprising: a support member for supporting, at least on
one side thereof, said heat source and said heat-sink assembly;
said heat-sink assembly comprising: a base member having
heat-dissipating means and means for attaching said heat-sink
assembly to said at least one side of said support member with use
of surface mount technique, said base member and said means for
attaching said heat-sink assembly being made from a single
workpiece and comprise an integral part.
2. The heat-sink assembly of claim 1, wherein said means for
attaching said heat-sink assembly is a solder connection of said
heat-sink assembly to said support member.
3. The heat-sink assembly of claim 2, wherein said base member has
a through opening with a periphery in the area above said heat
source and between said means for attaching said heat-sink
assembly, said opening having bendable members arranged on said
periphery, said heat-dissipating means comprising at least a main
heat sink insertable into said opening by deforming said bendable
members to a bended position and installing said heat-dissipating
means to a heat-exchanging position which provides said heat
exchanging contact between said heat-sink assembly and heat source,
said bendable members comprising locking means for locking said
heat-dissipating means in said a heat-exchanging position.
4. The heat-sink assembly of claim 3, wherein said main heat sink
has heat-dissipating fins selected from the group consisting of
heat dissipating fins arranged parallel to said support member and
heat dissipating fins arranged perpendicular to said support
member.
5. The heat-sink assembly of claim 4, wherein said heat-dissipating
fins arranged parallel to said support member comprise a plurality
of parallel disks and wherein said heat-dissipating fins
perpendicular to said support member comprise a plurality of radial
outward projections.
6. The heat-sink assembly of claim 5, further comprising auxiliary
heat-dissipating means formed on said base member.
7. The heat-sink assembly of claim 4, wherein said auxiliary
heat-dissipating means comprise heat-dissipating fins formed on
said base member.
8. The heat-sink assembly of claim 5, further comprising air-flow
guiding means attached to said base member.
9. The heat-sink assembly of claim 8, wherein said air-flow guiding
means comprises a funnel for directing air flow to said main heat
sink.
10. The heat-sink assembly of claim 3, wherein a gap is formed
between said heat-dissipating means and said heat source in said
heat-exchanging position and wherein said gap is filled with a
heat-conducting medium through which said heat exchanging contact
between said heat-sink assembly and heat source is carried out.
11. The heat-sink assembly of claim 10, wherein said
heat-conducting medium is selected from a group consisting of a
heat-conducting adhesive, heat-conducting epoxy, and
heat-conducting tape.
12. The heat-sink assembly of claim 5, wherein a gap is formed
between said heat-dissipating means and said heat source in said
heat-exchanging position and wherein said gap is filled with a
heat-conducting medium through which said heat exchanging contact
between said heat-sink assembly and heat source is carried out.
13. The heat-sink assembly of claim 12, wherein said
heat-conducting medium is selected from a group consisting of a
heat-conducting adhesive, heat-conducting epoxy, and
heat-conducting tape.
14. The heat-sink assembly of claim 6, wherein a gap is formed
between said heat-dissipating means and said heat source in said
heat-exchanging position and wherein said gap is filled with a
heat-conducting medium through which said heat exchanging contact
between said heat-sink assembly and heat source is carried out.
15. The heat-sink assembly of claim 14, wherein said
heat-conducting medium is selected from a group consisting of a
heat-conducting adhesive, heat-conducting epoxy, and
heat-conducting tape.
15. The heat-sink assembly of claim 7, wherein a gap is formed
between said heat-dissipating means and said heat source in said
heat-exchanging position and wherein said gap is filled with a
heat-conducting medium through which said heat exchanging contact
between said heat-sink assembly and heat source is carried out.
16. The heat-sink assembly of claim 15, wherein said
heat-conducting medium is selected from a group consisting of a
heat-conducting adhesive, heat-conducting epoxy, and
heat-conducting tape.
16. The heat-sink assembly of claim 8, wherein a gap is formed
between said heat-dissipating means and said heat source in said
heat-exchanging position and wherein said gap is filled with a
heat-conducting medium through which said heat exchanging contact
between said heat-sink assembly and heat source is carried out.
17. The heat-sink assembly of claim 16, wherein said
heat-conducting medium is selected from a group consisting of a
heat-conducting adhesive, heat-conducting epoxy, and
heat-conducting tape.
18. A heat-sink assembly for removal of heat from an IC chip source
with which said heat-sink assembly is maintained in a
heat-exchanging contact, comprising: a PC board for supporting, at
least on one side thereof, said IC chip and said heat-sink
assembly, said IC chip having a height; said heat-sink assembly
comprising: a U-shaped base member made of a metal with good
heat-conducting properties and having a central part parallel to
said IC chip and side members perpendicular to said central part,
said central part being raised above said PC board, said side
members having lower ends which are located below said central part
and being soldered to said PC board so that a space a having a
height greater than said height of said IC chip and sufficient to
accommodate said IC chip is formed between said PC board and said
central part; and a main heat sink for removal of heat from said IC
chip through said heat-exchanging contact.
19. The heat-sink assembly of claim 18, wherein in said U-shape
base member said central part and said side members including said
lower ends are made from a single sheet-metal workpiece.
20. The heat-sink assembly of claim 19, wherein said base member
has a through opening with a periphery in the area above said IC
chip and between said side members, said opening having bendable
lugs arranged on said periphery, said main heat sink being
insertable into said opening by deforming said bendable lug to a
bended position and installing said main heat sink to a
heat-exchanging position which provides said heat exchanging
contact between said heat-sink assembly and said IC chip, said
bendable lugs comprising locking means for locking said main heat
sink in said a heat-exchanging position.
21. The heat-sink assembly of claim 20, wherein said main heat sink
has heat-dissipating fins selected from the group consisting of
heat dissipating fins arranged parallel to said PC board and heat
dissipating fins arranged perpendicular to said PC board.
22. The heat-sink assembly of claim 21, wherein said
heat-dissipating fins arranged parallel to PC board comprise a
plurality of parallel disks and wherein said heat-dissipating fins
perpendicular to said PC board comprise a plurality of radial
outward projections.
23. The heat-sink assembly of claim 22, further comprising
auxiliary heat-dissipating means formed on said base member.
24. The heat-sink assembly of claim 23, wherein said auxiliary
heat-dissipating means comprise heat-dissipating fins formed on
said side members.
25. The heat-sink assembly of claim 22, further comprising air-flow
guiding means attached to said base member.
26. The heat-sink assembly of claim 25, wherein said air-flow
guiding means comprises a funnel for directing air flow to said
main heat sink.
27. The heat-sink assembly of claim 3, wherein a gap is formed
between said heat-dissipating means and said heat source in said
heat-exchanging position and wherein said gap is filled with a
heat-conducting medium through which said heat exchanging contact
between said heat-sink assembly and heat source is carried out.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to heat a sink for removal of
heat from a heat source, in particular, from a semiconductor chip
or a similar electronic or electric devices which are heated during
the operation and are located in confined spaces.
BACKGROUND OF THE INVENTION
[0002] Semi-conductor chip packages, which may contain a plurality
of integrated circuits combined into a compact unit, become more
complex and operate at higher frequencies. As a result, during
operation they generate more heat. As a rule such devices are
located in confined spaces from which the heat has to be removed.
However, electronic devices can normally be heated to a
predetermined limit. Heating above this limit may impair
performance characteristics of the device and even lead to its
damage. Moreover, long-term operation in a heated state, even at
temperatures below the threshold, may drastically reduce the
service life of the device.
[0003] Thus, in general, the component package configuration and
construction are specifically designed to allow for maximized heat
dissipation. Heat spreaders and heat sinks are employed in such
electronic component packages to transfer heat to a moving air
stream or on to another surface.
[0004] It should also be noted that a part of the heat flows from
the chip to the ground plane of the PC board through the pins and
the bottom side of the case, and will be partly carried away by
convection to the entire PC board. As result, the temperature of
the PC board increases for the following four reasons: 1) the PC
board thin copper ground plane has high heat resistance; 2) the
available ground plane size of copper is limited in dense PC
boards; 3) the narrow and thin traces have high heat resistance; 4)
other devices on same board might generate heat too, which can heat
the device to higher temperatures.
[0005] In some IC devices, small part of the heat will be
dissipated to the top side of the IC, as the heat resistance
between the internal die and the top case is fairly large. In this
case the base part will be the dominant one for heat
dissipation.
[0006] In order to enhance the heat-dissipation effect through a
heat sink, some heat sinks are provided with an air funnel for
directing the flow of air through the heat sink and between the
heat-dissipating fins.
[0007] In modern heat-sink assemblies, the problems associated with
limitations in connection with holes in the chip support members
are solved with the so-called surface-mount technique, while the
problems associated with automatic assembling are solved by the use
of various snapping connections.
[0008] The surface-mount technique is based on the use of
soldering. Pads on the circuit board are provided with a solder
mount for the heat sink or a clip holding the heat sink. A circuit
component is mounted to the heat sink and the component and heat
sink are mounted to the board, the heat sink being mounted to the
pads to dissipate heat from the circuit component attached thereto.
In some cases, the heat sink or pads are connected to a ground
plane in the circuit board to additionally dissipate heat from the
circuit board. Heat-exchanging contact between the heat sink and
the chip can be carried out through mechanical contact or through a
heat-conductive medium that fills the space between the bottom of
the heat sink and the facing surface of the chip. Furthermore, the
heat is dissipated from all heated surfaces through a natural
convection.
[0009] An example of a heat-sink assembly based on the use of a
surface mounting technique is a device described in U.S. Pat. No.
4,625,260 issued in 1986 to W. Jordan, et al. The device comprises
a heat-sink support, which is soldered to a PC board and has
spring-loaded clips for detachably securing a heat sink. Although
this device is suitable for automatic assembling in combination
with the surface-mount technique, it has spring-loaded attachment
of the heat sink, which is unreliable for use under conditions of
shakes and vibrations.
[0010] Heat-sink devices are not necessarily surface mounted. For
example, U.S. Pat. No. 5,386,144 issued in 1995 to P. Variot et al.
discloses an electronic component assembly which comprises an
electronic component package, a heat sink having an outwardly
projecting latching members, and spring arms on the component
package for resiliently clamping the latching members to the
component package. The heat sink has a body configured and arranged
to bear on the electronic component and mounts a latching member
extending from the body and including a shank extending from the
heat sink body having a latching flange at the distal end of the
shank. A disadvantage of the invention disclosed in U.S. Pat. No.
5,386,144 is that it is applicable to component packages having a
very specific configuration and therefore is not universal in its
use. Another disadvantage is a complicated construction of the
heat-sink attachment that requires the use of springing and
latching members.
[0011] U.S. Pat. No. 6,075,699 issued in 2000 to W. Rife discloses
a heat sink assembly installed above an electronic component for
removing heat therefrom. The assembly includes a base member with
downwardly directed legs, which have snapping ends for insertion
into mounting holes formed on a support that mounts the electronic
component. The base member has a central threaded opening for
threadably receiving a heat sink to position in which the end of
the heat sink is in flush thermal communication with the electronic
component while the legs are secured within their respective holes
in the electronic component. The device of U.S. Pat. No. 6,075,699
is designed for removal of heat only from the chip itself and
cannot be used for cooling the surrounding lead wires and other
electrical connections. This is because the heat is transferred to
the heat exchanger only from the chip and cannot be efficiently
transferred through the snapping ends of the attachment legs.
Another serious disadvantage of the aforementioned construction is
that it has a limited application and is suitable only to those
designs, which allow holes in a chip-supporting member, which is
not always the possible. Furthermore, in case of automatic
assembling, threaded connection of the heat sink with the base
member will slow down the assembling operation and will make it
more complicated and expensive.
[0012] An example of a heat-sink assembly which can be used only
with PC boards that allow holes in their structures is a device of
U.S. Pat. No. 5,917,701 issued in 1999 to T. Solberg, which
discloses a vertically-arranged heat-sink support structure that
consists of a lower member and an upper member. The circuit board
has a plurality of openings in a mounting surface thereof. The
fastener includes a body having a main portion. A spring clip
extends in a first direction from the main portion into the groove
and is biased to engage the first and second surfaces of the heat
sink. A plurality of latches on the spring clip engages the lock
recesses when the spring clip engages the first and second surfaces
of the heat sink. A plurality of anchor lugs extends in a second
direction from the main portion, opposite the first direction, to
be received in respective openings in the board to rigidly attach
the fastener to the circuit board. Preferably, the anchor lugs are
of differing lengths and configurations to permit assembly of the
clip to differently sized circuit boards. Also preferably,
engagement protrusions on the clip engage a concave surface on the
heat sink.
[0013] An advantage of the assembly of U.S. Pat. No. 5,917,701 is
that it is suitable for automatic assembling. However, this
assembly requires a provision of holes in the PC board. A second
disadvantage is a provision of spring-loaded clips, since with the
lapse of time the clips may loose their resiliency, so that
conditions of heat-conducting contact can be lost. Moreover, if the
entire device operates under conditions of vibrations or shocks,
the upper and lower parts of the heat-sink attachment can get loose
and be completely disconnected.
OBJECTS AND SUMMARY OF THE INVENTION
[0014] It is an object of the present invention to provide a heat
sink device which is suitable for automatic assembling, is simple
and universal in construction, inexpensive to manufacture, does not
use screws, ridge other threaded connections, or clips, removes
heat not only from the chip but from the chip-supporting areas of
the PC board, can be installed on a PC board without the use of
holes in the PC board, allows to minimize the amount of parts in a
heat-sink assembly by combining the base and the funnel into an
integral unit made from a single workpiece, simplifies attachment
of the heat sink to the base with the use of an automatic assembly
machine such as a "pick and place" machine, and improves
reliability of heat-transfer contacts in a heat-transfer chain of
the assembly.
[0015] The heat-sink assembly of the invention is attached to the
PC board with the use of surface mount technology. The assembly
comprises a base part or a base member soldered to the PC board and
a top part or a heat-sink member snapped-on through the central
opening of the base member by irreversibly deforming bendable lugs
which may have a radial or any other suitable shape. The bottom of
the heat-sink member may be pushed down to physical contact with
the top of the chip or to a position that leaves a space between
the bottom of the heat-sink member and the top of the chip, so that
the aforementioned space may be filled with a heat-conducting
medium. It is an option to use the base part only. If necessary, a
second heat-sink member of the same type, which could have
different dimensions, can be soldered to the PC board side opposite
to the chip. The heat sinks could be used with or without a
fan.
BRIEF DESRIPTION O THE DRAWINGS
[0016] FIG. 1 is a three-dimensional view of a heat-sink assembly
of the invention with vertically arranged fins of the heat
sink.
[0017] FIG. 2 is a view similar to FIG. 1 with the heat-sink member
removed for illustration of a central opening with bendable lugs
for attachment of the heat-sink member to the base member.
[0018] FIG. 3 is a partially-sectional side view of the heat-sink
assembly along line III-III of FIG. 1.
[0019] FIG. 4 is a three-dimensional view of a heat-sink assembly
made in accordance with another embodiment of the invention,
wherein the heat sink member is combined with an air-flow
funnel.
DETAILED DESCRIPTION OF THE INVENTION
[0020] FIG. 1 is a three-dimensional view of a heat-sink assembly
of the invention with vertically arranged fins of the heat
sink.
[0021] The entire unit, which in FIG. 1 is designated by reference
numeral 20, consists of a base member 22, a main heat-sink member
24, with vertically arranged radial fins 25a, 25b, . . . 25n,
attached to the base member 22, and a heat source, e.g., an IC chip
26 installed on a PC board 28 under the base member 22.
[0022] The base member 22 is made out of metal capable of being
soldered to the ground plane of the PC board 28 without glue, clip
or screw. If additional mechanical strength is required, it could
have one or more pins (not shown) to be inserted into holes (not
shown) in the PC board 28. The base member 22 has a U-shaped
configuration with a central part 30 which is raised and arranged
parallel to the PC board 28 and two side portions 32a and 32b
arranged perpendicular to the central part 30. The side portions
32a and 32b are made integrally with the central part 30, i.e.,
from a single piece of a sheet metal.
[0023] FIG. 2 is a view similar to FIG. 1 with the heat-sink member
removed for illustration of a central opening with bendable lugs
for attachment of the heat-sink member to the base member.
[0024] As shown in FIG. 2, in order to provide room for the IC chip
26, the central part is raised to a height H above the lower ends
of the folded portions 34a and 34b of the base member 22, so that
the height H from the lowest point of the bendable lugs 42a, 42b, .
. . 42n is greater than the thickness of the IC chip 26.
[0025] The aforementioned the lower ends of the folded portions 34a
and 34b rest on soldering pads 36a and 36b, which are known in the
art and are used for soldering the heat-sink member to the PC board
in manner known in the art.
[0026] It can be seen from FIG. 2 that the sided portions 32a and
32b of the heat-sink member 22 are provided with additional
heat-dissipating fins 38a and 38b formed on the upper or free ends
of the side portions 32a and 32b. As shown in the same FIG. 2, the
central part 30 of the heat-sink member 22 has an opening 40. The
periphery of the opening 40 is defined by a plurality of bendable
lugs 42a, 42b, . . . 42n directed radially inwardly.
[0027] FIG. 3 is a partially-sectional side view of the heat-sink
assembly along line III-III of FIG. 1. As can be seen from FIG. 3,
the heat sink member 24 has at it lower end a cylindrical
projection 41 with a diameter D1 greater than the inner diameter D2
of the opening 40 (FIG. 2). In other words, diameter D1 is greater
than the distance between the tips of the diametrically-opposite
bendable lugs (42a and 42n shown in FIGS. 2 and 3). As a result,
when in automatic assembling operation, the heat-sink member is
attached to the base member 22, it is pushed towards the IC chip 26
so that the cylindrical portion 41 passes through the opening 40
and bends the radial lugs to positions shown in FIG. 3 by reference
numerals 42a and 42n. The force applied from the deformed lugs to
the surface of the cylindrical projection 41 will be sufficient to
firmly hold the heat sink member 24 in place.
[0028] In order to provide a uniform reliable heat-exchanging
contact between the lower end face 44 of the cylindrical projection
41 and the top surface 46 of the IC chip 26, the cylindrical
projection 41 does not reach the top surface 46 and forms a gap G
therewith. This gap is filled with a heat conductive medium 48,
such as a heat-conductive glue, paste, tape, or resin, e.g., an
epoxy resin. Furthermore, a provision of gap G solves does not
require accurate tolerances in positioning the lower end of the
heat sink relative to the IC chip 26.
[0029] FIG. 4 is a three-dimensional view of a heat-sink assembly
made in accordance with another embodiment of the invention,
wherein the heat sink member is combined with an air-flow
funnel.
[0030] In general, the heat sink assembly 120 of this embodiment is
similar to the one described above and differs from it by the use
of a heat-sink member 124 with heat-dissipating fins 125a, 125b, .
. . 125n arrange parallel to the PC board 128 and by a provision of
an air-flow funnel 127, formed by two baffles 129a and 129b which
form an air duct for directing the flow of cooling medium shown by
arrows A and B (FIG. 4) to the heat-sink member 120 in order to
pass the cooling medium between the heat-dissipating fins 125a,
125b, . . . 125n. The cooling medium may be a cooling air supplied
by a fan (not shown).
[0031] Other parts and elements of the assembly of FIG. 4, i.e.,
the base member, the PC board, etc., are the same as in the
previous embodiment and therefore their description is omitted.
[0032] Thus it has been shown that the invention provides a heat
sink device which is suitable for automatic assembling, is simple
and universal in construction, inexpensive to manufacture, does not
use screws, other threaded connections, or clips, removes heat not
only from the chip but from the chip-supporting areas of the PC
board, can be installed on a PC board without the use of holes in
the PC board, allows to minimize the amount of parts in a heat-sink
assembly by combining the base and the funnel into an integral unit
made from a single workpiece, simplifies attachment of the heat
sink to the base with the use of an automatic assembling machines
such as a "pick and place" machine, and improves reliability of
heat-transfer contacts in a heat-transfer chain of the
assembly.
[0033] Although the invention has been described with reference to
a specific embodiment, it is understood that this embodiment should
not be construed as limiting the application of the invention.
Therefore any changes in the shapes, materials, and constructions
are possible, provided these changes do not depart from the scope
of the patent claims. For example, the heat-sink assembly of the
first embodiment with vertically arranged fins of the heat sink
also can be provided with a funnel of the type shown in FIG. 4. The
heat-sink members may be of any other shape and construction that
those shown in the drawings. The end of the heat sink member may be
brought into direct physical contact with the top of the chip. The
parts of the assembly can be made from various materials such as
metals or can be molded from heat-conductive plastics. Soldering
attachment can be combined with locking pins. Bendable lugs may
have springing properties. The heat-sink member can be additionally
soldered to the base. The heat-sink assembly can be used in
combination with a cooling fan or without the fan.
* * * * *