Title: Retention module, heat sink and electronic device
Abstract: It is an object of the present invention to provide a retention module, a heat sink and electronic apparatus for effectively the heat from a chip set. The retention module for a CPU is provided with a heat sink for the chip set.
Patent Number: 6,992,889 Issued on 01/31/2006 to Kashiwagi, et al.
| Inventors:
|
Kashiwagi; Toshiyuki (Kawasaki, JP);
Katou; Hirokatsu (Kawasaki, JP)
|
| Assignee:
|
Fujitsu Limited (Kawasaki, JP)
|
| Appl. No.:
|
181425 |
| Filed:
|
January 25, 2000 |
| PCT Filed:
|
January 25, 2000
|
| PCT NO:
|
PCT/JP00/00347
|
| 371 Date:
|
November 5, 2002
|
| 102(e) Date:
|
November 5, 2002
|
| PCT PUB.NO.:
|
WO01/56346 |
| PCT PUB. Date:
|
August 2, 2001 |
| Current U.S. Class: |
361/700; 165/104.33; 165/185; 257/719; 361/704; 361/710; 361/719 |
| Current Intern'l Class: |
H05K 7/20 (20060101) |
| Field of Search: |
174/163
165/802,803,121,122,185,104.33
257/718-719,726-727,714-716
361/697,694-695,700,801-802
439/485
|
References Cited [Referenced By]
U.S. Patent Documents
| 5548090 | Aug., 1996 | Harris.
| |
| 5734550 | Mar., 1998 | Penniman et al.
| |
| 5969940 | Oct., 1999 | Sano et al.
| |
| 5991152 | Nov., 1999 | Chiou.
| |
| 6046906 | Apr., 2000 | Tseng.
| |
| 6243265 | Jun., 2001 | Wong et al.
| |
| 6269863 | Aug., 2001 | Wyler.
| |
| 6327147 | Dec., 2001 | Llapitan et al.
| |
| 6449163 | Sep., 2002 | Stark et al.
| |
| Foreign Patent Documents |
| 834795 | Apr., 1998 | EP.
| |
| 07-283351 | Oct., 1995 | JP.
| |
| 10-224060 | Aug., 1998 | JP.
| |
| JUM 3054/346 | Sep., 1998 | JP.
| |
| 10-340138 | Dec., 1998 | JP.
| |
| JUM 3057/411 | Feb., 1999 | JP.
| |
| 11-143585 | May., 1999 | JP.
| |
| 11-312883 | Nov., 1999 | JP.
| |
| WO96/42044 | Dec., 1996 | WO.
| |
Primary Examiner: Thompson; Gregory
Attorney, Agent or Firm: Westerman, Hattori, Daniels & Adrian LLP
Claims
What is claimed is:
1. A retention module comprising:
a holding part for holding a CPU;
a first connecting part connectible thermally to a chip set that is connectible
electrically to the CPU; and
a heat conduction part, connected to said first connecting part, for transmitting
heat from the chip set to the outside, through the holding part.
2. A retention module according to claim 1, further comprising a heat radiating
part, connected to the heat conduction part, for radiating heat from the chip set
and the CPU.
3. A retention module according to claim 1, wherein the heat conduction part
is thermally connected to a heat radiating part for radiating heat from the CPU.
4. A retention module according to claim 1, wherein the heat conduction part
radiates the heat from the CPU.
5. A retention module according to claim 1, wherein the heat conduction part
includes a heat pipe.
6. A retention module according to claim 1, further comprising a second connecting
part, arranged approximately parallel to a substrate, for electrically connecting
the CPU to the substrate.
7. A retention module according to claim 1, further comprising a second connecting
part, arranged approximately perpendicular to a substrate, for electrically connecting
the CPU to the substrate.
8. A circuit structure comprising:
a substrate;
first and second exoergic circuit elements connectible electrically to each other
through said substrate;
a holding mechanism for fixing said first circuit element onto said substrate
and for electrically connecting said first circuit element to said substrate;
a first heat radiating part, connected to said holding mechanism, for radiating
heat from said first circuit element; and
a second heat radiating part, connected to the holding mechanism, for radiating
heat from said second circuit element.
9. A heat sink comprising:
a connecting part connected to a chip set; and
a heat conduction part, connected to said connecting part, for transmitting heat
from the chip set to the outside.
10. An electronic apparatus comprising:
a housing;
a substrate housed in said housing;
a CPU provided on the substrate;
a memory for communicating with said CPU;
a chip set, provided on the substrate between said CPU and memory, for controlling
operations of said CPU and memory;
a retention module for fixing said CPU onto said substrate and for electrically
connecting said CPU to said substrate,
wherein said retention module includes:
a first connecting part connected to the chip set; and
a heat conduction part, connected to said first connecting part, for transmitting
heat from the chip set to the outside.
11. An electronic apparatus according to claim 10, further comprising a sheet
metal provided in said housing and connecting thermally to said heat conduction
part, said sheet metal supporting said housing.
12. An electronic apparatus comprising:
a housing;
a substrate housed in said housing;
first and second exoergic circuit elements connectible electrically to each other
through said substrate;
a holding mechanism for fixing said first circuit element onto said substrate
and for electrically connecting said first circuit element to said substrate;
a first heat radiating part, connected to said holding mechanism, for radiating
heat from said first circuit element; and
a second heat radiating part, connected to the holding mechanism, for radiating
heat from said second circuit element.
Description
FIELD OF THE ART
The present invention relates generally to heat radiator mechanisms, and more
particularly to a heat radiator mechanism for radiating the heat from a circuit
element mounted in an electronic apparatus. The present invention is suitable for
a retention module (also referred to as a CPU socket, a retention kit or a retention
tool) for electrically connecting a CPU to a motherboard and for fixing the CPU
onto the motherboard, and the inventive electronic apparatus broadly covers personal
computers (PCs) of desktop type including a tower type, measurement devices, control
devices, and the like.
BACKGROUND OF THE INVENTION
A CPU (Central Processing Unit) in a computer handles data inputs/outputs, executes
commands, controls each component, and thus directly affects computer performance.
A current CPU uses a laterally long and wide cartridge called Slot 1 Type as seen
in U.S. Intel Pentium II.
A computer exhibits higher performance as it mounts a higher CPU; the heating
value
increases as the CPU performance improves. Accordingly, a heat sink as one cooling
device is provided near the CPU to thermally protect the CPU. The heat sink has
cooling fins near the CPU and radiates the heat from it through natural cooling.
For example, the CPU in the desktop type computer is typically fixed onto and connected
electrically to a motherboard.
The retention module typically includes a holding part for mechanically fixing
the CPU onto a motherboard, and a slot that may be engaged with a card edge connector
as a CPU terminal and electrically connected to the motherboard. Therefore, when
the CPU is held by the holding part and the card edge connector is inserted into
the slot, the CPU is electrically connected to the motherboard through the retention module.
The motherboard is provided with various circuit elements including a memory
(socket), chip set, extension slot, and BIOS ROM, as well as the CPU. The chip
set is a circuit element group for controlling data transmissions and receptions
among the CPU, memory, such as a RAM, and extension card in the computer. The performance
of the chip set has been improved as the CPU. Intel 440BX, 440ZX, 810 chip sets
are currently known, and there are various chip sets for CPUs, videos, and peripherals.
Among them, the CPU chip set, which is typically provided between the CPU and the
memory, serves to connect the CPU and memory, and control a data flow between the
CPU and memory.
SUMMARY OF THE INVENTION
However, as the chip set has more improved performance, influence of the
heating value from the chip set, which was conventionally negligible, has become
non-negligible. As the heating value of the CPU increases, the heat from the CPU
greatly affects the chip set near the CPU. Therefore, the protection of the chip
set from thermal malfunctions and damages has needed a heat radiator means for
the chip set, which was not required conventionally. In particular, the chip set
for the CPU should be located near the CPU and memory in a congested space for
controls over communications between them, and this congested space sterilizes
the natural cooling effect: There has been needed an effective heat radiator means.
Circuit elements are expected to be closer and closer in the future along with
the progress of the high integration of the motherboard.
Accordingly, it is a general object of the present invention to provide
a novel and useful retention module, heat sink and electronic device in which the
above disadvantages are eliminated.
More specifically, the present invention has an exemplary object to provide
a retention module, heat sink and electronic device which radiates the heat from
the chip set effectively, easily and cost-efficiently.
In order to achieve the above objects, a retention module of one aspect of the
present invention includes a holding part for holding a CPU, a first connecting
part connectible thermally to a chip set that is connectible electrically to the
CPU, and a heat conduction part, connected to the first connecting part, for transmitting
heat from the chip set to the outside. This retention module serves to radiate
the heat from the chip set.
A circuit structure of another aspect of the present invention includes a substrate,
first and second exoergic circuit elements connectible electrically to each other
through the substrate, a holding mechanism for fixing the first circuit element
onto the substrate and for electrically connecting the first circuit element to
the substrate, a first heat radiating part, connected to the holding mechanism,
for radiating heat from the first circuit element, and a second heat radiating
part, connected to the holding mechanism, for radiating heat from the second circuit
element. This circuit structure radiates heat from the first and second circuit
elements using the first and second heat radiating parts.
A heat sink of one aspect of the present invention includes a connecting part
connected
to a chip set, and a heat conduction part, connected to the connecting part, for
transmitting heat from the chip set to the outside. This heat sink serves to radiate
the heat from the chip set.
An electronic apparatus of another aspect of the present invention includes a
housing, a substrate housed in the housing, a CPU provided on the substrate, a
memory for communicating with the CPU, a chip set, provided on the substrate between
the CPU and memory, for controlling operations of the CPU and memory, a retention
module for fixing the CPU onto the substrate and for electrically connecting the
CPU to the substrate, wherein the retention module includes a first connecting
part connected to a chip set, and a heat conduction part, connected to the first
connecting part, for transmitting heat from the chip set to the outside. This electronic
device exhibits similar operations as those of the above retention module.
An electronic apparatus of another aspect of the present invention includes a
housing, a substrate housed in the housing, first and second exoergic circuit elements
connectible electrically to each other through the substrate, a holding mechanism
for fixing the first circuit element onto the substrate and for electrically connecting
the first circuit element to the substrate, a first heat radiating part, connected
to the holding mechanism, for radiating heat from the first circuit element, and
a second heat radiating part, connected to the holding mechanism, for radiating
heat from the second circuit element. This electronic apparatus uses the first
and second radiating parts to radiate heat from the first and second circuit elements.
Other objects and further features of the present invention will become readily
apparent from the following description of the embodiments with reference to accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic plane view of a retention module before a CPU and a fan
heat sink are mounted.
FIG. 2 is a schematic sectional view of the retention module shown in FIG. 1.
FIG. 3 is a schematic plane view of a retention module after the CPU and fan
heat sink are mounted.
FIG. 4 is a schematic sectional view of the retention module shown in FIG. 3.
FIG. 5 is an exploded view for explaining an engagement between the CPU and
retention module.
FIG. 6 is another exploded view viewing FIG. 5 at a different angle.
FIG. 7 is an exploded view of the retention module and its peripheral on a motherboard.
FIG. 8 is a schematic perspective view of the retention module before the CPU
and fan heat sink are mounted.
FIG. 9 is a schematic perspective view of the retention module after the CPU
and fan heat sink are mounted.
FIG. 10 is a schematic and partial section for explaining a method for radiating
the heat from the chip set using the retention module provided in the desktop type
personal computer.
FIG. 11 is a schematic perspective view of the desktop type personal computer
shown in FIG. 10.
FIG. 12 is a partially enlarged perspective view of the retention module shown
in FIG. 9 for explaining thermal connection between the chip-set heat sink and
CPU heat sink.
FIG. 13 is a schematic perspective view of the retention module as a modification
shown in FIG. 1 having a straight type slot 120
a.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
A detailed description will now be given of an embodiment according to the present
invention with reference to FIGS. 1-4. FIG. 1 is a schematic plane view of a retention
module
100 before a CPU
40 and a fan heat sink
50 are mounted.
FIG. 2 is a schematic sectional view of the retention module
100 shown in
FIG. 1. FIG. 3 is a schematic plane view of the retention module
100 after
the CPU
40 and fan heat sink
50 are mounted. FIG. 4 is a schematic
sectional view of the retention module
100 shown in FIG. 3. FIGS. 5 and
6 are exploded views for explaining an engagement among the CPU
40, cooling
fins
52 (without a fan) and retention module
400, viewed from different angles.
The retention module
100 electrically connects the CPU
40 to the
motherboard
30, and includes a pair of standing holding parts
110,
slot
120, heat sink
0.
130, and connecting part
136.
This embodiment mounts the retention module
100 onto the motherboard
30
in a desktop type PC
200 as one example of an electronic apparatus. The
holding part
110 includes a stand
112 onto which the CPU
40
may be placed, as shown in FIG. 2. The stand
112 is not necessarily provided
because the CPU
40 may be placed on the heat sink
130 as described
later. The holding part
110 is connected to the slot
120 and heat
sink
130, and made of plastic. The connecting part
136 is provided
in the holding part
110 and thermally connected to the heat sinks
130
and
50.
Although the connecting part
110 has an approximately exemplary L
shape in FIGS. 1 and 3, a projection
114 is omitted in FIGS. 5 and 6. The
holding part
110 accommodates the CPU
40 to fix it laterally, and
protects it from impacts. The holding part
110 guides an engagement between
the card edge connector
42 and the slot
120, which will be described
later, and prevents the connector
42 from deteriorating due to load (or
stress). Optionally, the holding part
110 may be engaged with the attachment
156 and may fix the CPU
40 and fan heat sink
50 in the height
direction, as will be described with reference to FIGS. 7 and 8.
The slot
120 has an opening
122 that is engageable with the card
edge connector
42 of the CPU
40. The opening
122 is provided
with a terminal (not shown) that is connectible to the connector
42, and
electrically connected to the motherboard
30. The CPU
40 is thus
electrically connected to the motherboard
30 through an engagement between
the card edge connector
42 and the slot
120. As the CPU
40
has a laterally long and wide Single Edge Connector Cartridge ("SECC") shape universally
used for Intel Pentium II and III, the slot
120 exemplarily has a Slot 1
shape corresponding to it. The Slot 1 arranges the terminal in the opening
122
parallel to the motherboard
30 (such a slot is sometimes called "right angle
type"), but may arrange the terminal perpendicular to the motherboard
30
as will be described with reference to FIG. 13 (such a slot is sometimes called
"straight type").
In FIGS. 1-4, the chip set
20 is exemplarily located between the CPU
40
and motherboard
30. In general, the chip set is a circuit group for controlling
data transmissions and receptions among a CPU, a memory such as a RAM, and an extension
card in a computer, and there are various chip sets for CPUs, videos, and other
peripherals. Exemplarily, the chip set
20 is a CPU chip set in this embodiment,
and controls data flows between the CPU
40 and memory which will be described
and referenced later. The recent chip set has improved performance as seen in 440BX,
and thus considerable heating value. The inventive retention module
100
is not limited to that for the CPU, but may have a heat radiating mechanism for
the chip set
20 having the retention module
60 (or memory socket
60) for a memory, which will be described with reference to FIG. 7, etc.
The heat sink
130 contacts the chip set
20, transmits the heat
from the chip set
20 through the holding part
110 to the heat sink
50, and radiates the heat by enlarging the surface area of the chip set
20. Specifically, the heat sink
130 is thermally connected to the
connecting part
136 provided in the holding part
110, and transmits
the heat from the chip set
20 to the heat sink
50 through the connecting
part
136. The heat sink
50 is equipped with a fan
54 that
may compulsorily cool the cooling fins
52.
Referring to FIGS. 3 and 4, the heat sink
50 as a cooling device
for the CPU
40 is provided on the CPU
40 as the CPU
40 has
increased performance and thus increased heating value. The heat sink
50
has the cooling fins
52 and cooling fan
54, and projects from the
retention module
100. This embodiment uses a so-called PGA package that
arranges a plurality of pins for the CPU
40. Alternatively, the CPU
40
may use a shape (for example, Pentium II) wholly housed in a resin case. The inventive
retention module
100 is applicable both shapes of CPU
40.
The cooling fins
52 includes, as shown in FIG. 12, a multiplicity of heat
radiating fins arranged like a frog, enlarging the surface area of metal fins and
enhancing radiating performance. Here, FIG. 12 is a partially enlarged perspective
view of the retention module
100 for explaining thermal connections between
the heat sink
130 and cooling fins
52. As a result, the cooling fins
52 effectively radiate the heat from the CPU
40 and chip set
20
through natural cooling. The cooling fan
54 is also called a CPU cooler,
and uses a fan to compulsorily radiate the heat so as to thermally protect the
CPU
40. It is understood that the compulsory cooling by the cooling fan
54 has the highest radiating effect.
The heat sink
130 includes the connecting part
132 that contacts
the chip set
20, the heat conduction part
134 that transmits the
heat from the chip set
20, the connecting part
136 connected to the
heat conduction part
134 and the heat sink
50. In FIGS. 1-4 and
7,
the connecting part
132 and the heat conduction part
134 exemplarily
has a plate shape, but the connecting part
132 is configured to be concave
(or convex), as shown in FIGS. 5 and 6, relative to the heat conduction part
134
so that it may surely contact the top surface of the chip set
20 with predetermined
pressure. The convex connecting part
132 preferably has a size enough to
accommodate the chip set
20. Here, FIG. 7 is an exploded view of the retention
module
100 and its peripheral circuit elements.
As the heat conduction part
132 contacts or is located near the CPU
40,
it also serves to transmit the heat from the CPU
40 to the heat sink
50
via the connecting part
132. At this time, as needed, a heat insulating
material may be provided between the CPU
40 and the connecting part
132
so as to prevent the heat from the CPU
40 to be transmitted to the chip
set
20 through the heat conduction part
134. Understandably, the
heat conduction part
132 serves to stably hold the CPU
40. The heat
sink
130 is made of materials having high thermal conductivity such as aluminum.
This embodiment integrates, as shown in FIG. 7, the connecting part
136
and the heat conduction part
134 into one member, but may produce them as
independent members. The connecting part
136 of this embodiment is formed
by bending a metal plate shape of heat sink
130. Specifically, as shown
in FIG. 12, the connecting part
136 has a contact part
137 connected
to the cooling fins
52. In other words, the connecting part
136 is
thermally coupled with the cooling fins
52 through the contact part
137.
The contact part
137 has a plate spring shape so that it may surely contacts
the cooling fins
52. Unlike the instant embodiment, the heat sinks
50
and
130 and the connecting part
136 may be formed as one member.
Referring now to FIGS. 7-9, a description will be given of a mounting method
of the retention module
100 and the CPU
40. Here, FIG. 8 is a schematic
perspective view of the retention module
100 and its peripherals on the
motherboard
30 before the CPU
40 and fan heat sink
50 are
mounted. FIG. 9 is a schematic perspective view of the retention module
100
and its peripherals on the motherboard
30 after the CPU
40 and fan
heat sink
50 are mounted. In FIGS. 7-9, the retention module
100
places the CPU
40 on the heat sink
130, not the stand
112
shown in FIG. 2, etc.
Referring to FIG. 7, the heat sink
130 is fixed onto the holding
part
110 through screws
150, springs
152, and screw fixtures
154. The spring
152 serves to absorb an assembly error between the
heat sink
130, chip set
20 and holding part
110. The heat
sink
130 and holding part
10 are attached before or after the heat
sink
130 is positioned and fixed onto the chip set
20. The screw
150 and spring
152 fix the heat sink
130 and the holding part
110 onto the motherboard
30 from the rear side of the motherboard
30. FIG. 8 shows this state. As understood from FIG. 8, the holding part
110 is engaged with the attachment
156. The holding part
110
fixes the CPU
40 and the fan heat sink
50 in the height direction
through an engagement with the attachment
156. Then, the CPU
40 and
fan heat sink
50 are mounted onto the retention module
100 (although
FIG. 7 omits the cooling fan
54). FIG. 9 shows this state.
FIGS. 7-9 show the retention module
60 (or memory socket
60)
for use with a memory. The memory socket
60 is a socket to be coupled with
the memory module (not shown), enabling a user to exchange or expand a secondary
cash or main memory (or master storage) as a module. The module for the main memory
includes, for example, 72-pin SIMM and 168-pin DIMM, but its type is different
according to computer types. The memory stores various kinds of information for
the computer including programs and data and, in general, the main memory is often
called a memory simply. The memory that the CPU
40 directly accesses is
usually the main memory, and the computer processes by reading data and program(s)
from the external storage to the main memory. The chip set
20 controls data
flows between the CPU
40 and the memory to be inserted into the memory socket
60.
The inventive heat radiating means for the chip set
20 is not limited
to the heat sink
50. For example, the heat sink
50 may be thermally
connected to the external radiating means other than the heat sink
130.
Alternatively, heat radiating/heat conduction means, whether it is a heat pipe,
another cooling or water-cooling system, may be provided instead of or in addition
to the heat sink
50. The heat pipe has a pipe shape having a difference
of elevation for accommodating liquid, such as water. The heat pipe cools the exoergic
member by repeating a cycle in which the water vaporizes and moves to a high position
when receiving the heat from the exoergic member at a low position, and returns
to the low position after cooled by naturally or compulsorily and liquidized.
When the motherboard
30 with the retention module
100 that holds
the CPU
40 is installed in the desktop type PC
200, part of the heat
from the chip set
20 is transmitted to the sheet metal
90 in the
PC
200 for heat radiation purposes, as shown in FIGS. 10 and 11. Here, FIG.
10 is a schematic and partially section for explaining a method for radiating the
heat from the chip set
20 using the retention module
100 installed
in the desktop type PC
200. FIG. 11 is a schematic perspective view of the
desktop type PC
200 shown in FIG. 10. The sheet metal may be provided as
an independent member in the housing.
As shown in FIG. 11, the desktop type PC
200 includes a tower type body
210, a display
220, a keyboard
230, and a mouse
240.
The body
210 is made of sheet metal housing
90.
Referring to FIG. 10, the heat from the chip set
20 is radiated
after transmitted to the heat sink
50 through the connecting part
136
in the heat sink
130. Part of the heat from the chip set
20 is dissipated
in the air from the surface of the heat conduction part
134. The motherboard
30 is housed in the sheet metal housing
90 as a body case of the
PC
200. Here, when the screw
150 and spring
152 are formed
as a heat conduction member, the heat sink
130 is (thermally) connected
to the sheet metal housing
90 through a contact
92. As a result,
part of the heat from the chip set
20 is transmitted to and radiated by
the sheet metal housing
90 at the contact
92 through the screw
150
and spring
152. Thus, the heat from the chip set
20 may be effectively
radiated using multiple radiating means.
The above right angle type slot
120 may be replaced with the straight
type slot
120a as shown in FIG. 13. Here, FIG. 13 is a schematic
perspective view of the retention module
100a having the straight
type slot
120a. Characteristically, the retention module
100a
has the slot
120a and heat sink
130a, and the slot
120a arranges its connection part (opening
122a) with
the card edge connector
42a of the CPU
40a (not shown),
perpendicular to the motherboard
30a. The heat sink
130a
has the connecting part
134a connected to the top surface of
the chip set
20a, and is connected to the cooling fins
52a
at the connecting part
136a. The chip set
20a is
not covered with the CPU
40a and thus appears to be naturally cooled.
However, it is located in a packed space between the retention module
100a
and memory socket
60a (not shown), and thus the heat sink
130
is still effective when there is no smooth air convection. Moreover, as discussed,
the memory socket
60a (not shown) may have a cooling mechanism for
the chip set
20a instead of or in addition to the heat sink
130a.
The reference numeral with no alphabetical character generalizes reference numerals
with alphabetical characters unless otherwise specified.
A description will now be given of the operation of the desktop type PC
200.
When the user executes a program stored in a hard disc (not shown) accommodated
in the body
210 by manipulating the keyboard
230 or mouse
240,
the CPU
40 downloads necessary data from the hard disk to the memory (not
shown). At this time, the chip set
20 controls communications between the
CPU
40 and the memory. The heat at the time of control is radiated by the
natural cooled system by the heat conduction part
134, cooling systems by
the heat sink
50 and the sheet metal
90, etc., and the chip set
20
may provide stable and high speed operations.
Further, the present invention is not limited to these preferred embodiments,
and various variations and modifications may be made without departing from the
scope of the present invention. For example, the chip set is not limited to that
located between the CPU and the memory, and the present invention is broadly applicable
to exoergic circuit elements.
INDUSTRIAL APPLICABILITY
The retention module, heat sink, and electronic apparatus as one aspect of the
present invention serve to radiate the heat from a chip set, and thermally protect
the chip set for stable operations. The circuit structure and electronic apparatus
of another aspect of the present invention use the first and second radiating parts
to radiate the heat from the first and second circuit elements and protect these
circuit elements for stable operations.
*
