U.S. patent application number 16/891397 was filed with the patent office on 2020-12-24 for reducing base deck porosity.
The applicant listed for this patent is Seagate Technology LLC. Invention is credited to Jerome Thomas Coffey.
Application Number | 20200402546 16/891397 |
Document ID | / |
Family ID | 1000004917324 |
Filed Date | 2020-12-24 |
United States Patent
Application |
20200402546 |
Kind Code |
A1 |
Coffey; Jerome Thomas |
December 24, 2020 |
REDUCING BASE DECK POROSITY
Abstract
A method for making a hard disk drive is disclosed. The method
includes forming a base deck comprising an aluminum alloy via
vacuum casting. The method further includes subjecting the base
deck to hot isostatic pressing. The method further includes welding
a cover to the base deck.
Inventors: |
Coffey; Jerome Thomas;
(Boulder, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seagate Technology LLC |
Fremont |
CA |
US |
|
|
Family ID: |
1000004917324 |
Appl. No.: |
16/891397 |
Filed: |
June 3, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62865876 |
Jun 24, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11B 33/1406 20130101;
B23P 15/00 20130101; B23K 20/127 20130101; G11B 33/1486 20130101;
B23K 2101/36 20180801 |
International
Class: |
G11B 33/14 20060101
G11B033/14; B23K 20/12 20060101 B23K020/12; B23P 15/00 20060101
B23P015/00 |
Claims
1. A method for making a hard disk drive, the method comprising:
forming a base deck comprising an aluminum alloy via vacuum
casting; subjecting the base deck to hot isostatic pressing; and
welding a cover to the base deck.
2. The method of claim 1, wherein the subjecting the base deck to
hot isostatic pressing includes: placing the base deck in a
chamber; raising a chamber temperature of the chamber to
substantially near a solidus temperature of the base deck; raising
a chamber pressure of the chamber to a target pressure; and holding
the chamber temperature and the chamber pressure for a
predetermined time period.
3. The method of claim 1, wherein the subjecting the base deck to
hot isostatic pressing includes reducing the porosity of the base
deck from a first porosity to a second porosity.
4. The method of claim 3, wherein the second porosity is 50-95%
less porous than the first porosity.
5. The method of claim 3, wherein the first porosity and the second
porosity is measured as a total average porosity of the base
deck.
6. The method of claim 3, wherein the first porosity and the second
porosity is measured as a total average porosity of a volume
including one or more machined sections of the base deck.
7. The method of claim 1, wherein the welding a cover to the base
deck includes friction stir welding the cover to the base deck.
8. The method of claim 1, further includes at least partially
filling the hard disk drive with helium.
9. The method of claim 1, further includes subjecting the base deck
to an impregnation process.
10. The method of claim 9, wherein the subjecting the base deck to
the impregnation process includes introducing an impregnating agent
into surface-connected porosity of the base deck.
11. The method of claim 9, wherein the subjecting the base deck to
the impregnation process is performed after the subjecting the base
deck to hot isostatic pressing.
12. A base deck for a hard disk drive, the base deck comprising: a
base plate and sidewalls extending therefrom and integral with the
base plate, both the base plate and the sidewalls comprising a
vacuum-casted aluminum alloy having a porosity that is reduced by
50-95%.
13. The base deck of claim 12, further including an impregnating
agent at least partially filling the aluminum alloy's
surface-connected porosity.
14. The base deck of claim 12, wherein the aluminum alloy is
selected from a group consisting of ADC12, A380, and A383.
15. The base deck of claim 12, wherein the base plate and the
sidewalls are hot isostatically pressed.
16. The base deck of claim 12, wherein the base deck is coupled to
a cover to create a sealed enclosure.
17. The base deck of claim 16, wherein the cover is welded to the
base deck.
18. The base deck of claim 17, wherein the sealed enclosure is at
least partially filled with helium.
19. The base deck of claim 12, wherein the porosity is measured as
a total average porosity of the base deck.
20. An apparatus for subjecting a base deck to hot isostatic
pressing, the apparatus comprises: a chamber configured to receive
a base deck; a heating module configured to raise a chamber
temperature of the chamber to substantially near a solidus
temperature of the base deck; and a pressurizing module configured
to raise a chamber pressure of the chamber to a target pressure;
wherein the apparatus is configured to hold the chamber temperature
and the chamber pressure for a predetermined time period.
Description
RELATED APPLICATIONS
[0001] This application claims priority to Provisional Application
No. 62/865,876 filed Jun. 4, 2019, which is herein incorporated by
reference in its entirety.
TECHNICAL FIELD
[0002] Certain embodiments of the present disclosure relate to
systems and methods for reducing base deck porosity using hot
isostatic pressing.
SUMMARY
[0003] In certain embodiments, a method for making a hard disk
drive is disclosed. The method includes forming a base deck
comprising an aluminum alloy via vacuum casting, subjecting the
base deck to hot isostatic pressing, and welding a cover to the
base deck.
[0004] In certain embodiments, a base deck for a hard disk drive is
disclosed. The base deck includes a base plate and sidewalls
extending therefrom and that are integral with the base plate. Both
the base plate and the sidewalls comprise a vacuum-casted aluminum
alloy having a porosity that is reduced by 50-95%.
[0005] In certain embodiments, an apparatus for subjecting a base
deck to hot isostatic pressing is disclosed. The apparatus includes
a chamber configured to receive a base deck, a heating module
configured to raise a chamber temperature of the chamber to
substantially near a solidus temperature of the base deck, and a
pressurizing module configured to raise a chamber pressure of the
chamber to a target pressure. The apparatus is configured to hold
the chamber temperature and the chamber pressure for a
predetermined time period.
[0006] While multiple embodiments are disclosed, still other
embodiments of the present invention will become apparent to those
skilled in the art from the following detailed description, which
shows and describes illustrative embodiments of the invention.
Accordingly, the drawings and detailed description are to be
regarded as illustrative in nature and not restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 shows a cut-away side view of a hard drive, in
accordance with certain embodiments of the present disclosure.
[0008] FIG. 2 shows a cut-away side view of an upper portion of the
hard drive of FIG. 1, in accordance with certain embodiments of the
present disclosure.
[0009] FIG. 3 shows an apparatus for subjecting a base deck to hot
isostatic pressing, in accordance with certain embodiments of the
present disclosure.
[0010] FIG. 4 shows an illustrative method for making a hard disk
drive, in accordance with certain embodiments of the present
disclosure.
[0011] FIG. 5 shows an illustrative process for subjecting a base
deck to hot isostatic pressing, in accordance with certain
embodiments of the present disclosure.
[0012] While the disclosure is amenable to various modifications
and alternative forms, specific embodiments have been shown by way
of example in the drawings and are described in detail below. The
intention, however, is not to limit the disclosure to the
particular embodiments described but instead is intended to cover
all modifications, equivalents, and alternatives falling within the
scope of the appended claims.
DETAILED DESCRIPTION
[0013] Data storage devices like hard disc drives can be filled
with air or a lower density gas, such as helium, and sealed to
control and maintain the data storage device's internal
environment. For example, a hard disk drive can include a base deck
and a cover that are coupled together to form a sealed, enclosed
internal cavity. Sealing mitigates or prevents leakage of internal
gases from the storage device. However, one potential source of
leaks in a data storage device is through the walls of the base
deck. If portions of the base deck walls are too porous, helium can
leak through the walls. Certain embodiments of the present
disclosure relate to base decks with reduced porosity and systems
and methods for reducing base deck porosity using hot isostatic
pressing. Hot isostatic pressing involves subjecting an object to
elevated temperatures and isostatic gas pressure in a high pressure
chamber--resulting in pressure being applied to the object from all
directions to reduce the porosity of the object. When pressure is
applied to the object at the elevated temperature, porosity in the
object collapses and diffusion bonding is encouraged within the
collapsed voids.
[0014] FIG. 1 shows a cut away side view of a hard disk drive 100
including a base deck 102, a process cover 104, and a final cover
106. FIG. 2 shows a cut away side view of an upper portion of the
hard drive 100 before the final cover 106 is installed. The base
deck 102 includes side walls (e.g., side wall 108) that, together
with a bottom portion 110 (hereinafter referred to as a base plate)
of the base deck 102 and the process cover 104, creates an internal
cavity 112 that may house data storage components like magnetic
recording media 114, a spindle motor 116, an actuator pivot 118,
suspensions 120, and read/write heads 122. The spindle motor 116
and the actuator pivot 118 are shown in FIG. 1 as being coupled
between the process cover 104 and the base plate 110 of the base
deck 102.
[0015] During assembly, the process cover 104 can be coupled to the
base deck 102 by removable fasteners (not shown) and a gasket 124
(shown in FIG. 2) to seal a target gas (e.g., air with nitrogen and
oxygen and/or a lower-density gas like helium) within the internal
cavity 112. Once the process cover 104 is coupled to the base deck
102, a target gas may be injected into the internal cavity 112
through an aperture 126 (see FIG. 2) in the process cover 104,
which is subsequently sealed. Injecting the target gas, such as a
combination of air and a low-density gas like helium (e.g., with
the target gas including 90 percent or greater helium), may involve
first evacuating existing gas from the internal cavity 112 using a
vacuum 128 and then injecting the target gas from a low-density gas
supply reservoir 130 into the internal cavity 112. For example, to
facilitate the filling of the internal cavity 112, a sealing
assembly 132 (shown in FIG. 2) may be used. The sealing assembly
132 is shown as being coupled to the vacuum 128 and the low-density
gas reservoir 130. In use, the sealing assembly 132 may utilize the
vacuum 122 to evacuate the existing gas from the internal cavity
112 and then utilize the low-density gas reservoir 130 to inject a
target gas into the internal cavity 112. For example, the sealing
assembly 132 is moved towards the aperture 126 in the process cover
104 and be temporarily coupled to the process cover 104. Once
coupled, the sealing assembly 132 may evacuate the existing gas
from the internal cavity 112 via the aperture 126 and then inject
the target gas into the internal cavity 112 via the aperture 126.
The sealing assembly 132 (or another device) can then seal or close
the aperture 126 (by applying a seal, welding, or the like) to keep
the target gas within the hard drive 100 and, in particular, the
internal cavity 112.
[0016] Once the process cover 104 is sealed, the hard disk drive
100 can be subjected to a variety of processes and tests. Example
processes and tests include those that establish performance
parameters of the hard disk drive 100 (e.g., fly-height
parameters), that identify and map flaws on the magnetic recording
media 114, that write servo and data patterns on the magnetic
recording media 114, and that determine whether the hard disk drive
100 is suitable for commercial sale. The base deck 102 and the
final cover 106 can be coupled together to create an internal
cavity 134 between the process cover 104 and the final cover 106.
The base deck 102 and the final cover 106 may be coupled together,
for example, by welding and the like. Once the final cover 106 is
coupled to the base deck 102, the target gas may similarly be
injected through an aperture in the final cover 106 to fill the
internal cavity 134 (shown in FIG. 1) between the process cover 104
and the final cover 106. The aperture can then be sealed (by
applying a seal, welding, or the like).
[0017] After the hard disk drive 100 passes certain tests (which
could take days) and is sealed, the hard disk drive 100 may be
subjected to a leak test. The leak test determines whether the hard
disk drive 100 maintains an adequate level of the target gas under
various conditions. If the hard disk drive 100 fails the leak test,
the hard disk drive 100 must be reworked or scrapped. Because the
leak test occurs only after having spent days processing and
testing the hard disk drive 100, it is expensive to have hard disk
drives fail the leak test. Failing the leak test can be caused by,
among other things, the base deck 102 having too high of a porosity
such that helium leaks out of the hard disk drive 100 through the
base deck 102 (e.g., through the thinner and/or more porous
portions of the sidewalls 108). Certain embodiments of the present
disclosure are accordingly directed to reducing the porosity of
base decks using processes referred to as hot isostatic
pressing.
[0018] FIG. 3 shows an apparatus 200 for subjecting a base deck
(e.g., base deck 102) to hot isostatic pressing, which is sometimes
referred to as HIP. In some embodiments, the apparatus 200 includes
a chamber 202, a heating module 204, and a pressurizing module 206.
In various examples, the chamber 202 is configured to receive the
base deck and/or an object to be hot-isostatic-pressed. For
high-volume manufacturing, the chamber 202 can hold tens or
hundreds of base decks at a time. For example, the base decks may
be processed in the chamber 202 in batches.
[0019] When the chamber 202 is closed, a sealed chamber environment
is formed and the apparatus 200 is configured to adjust the
temperature and/or pressure of the sealed chamber environment as
described in more detail below. For example, the apparatus 200 can
be configured to hold the chamber temperature and/or the chamber
pressure for a predetermined time period. When an object such as a
base deck is placed in the chamber 202 and subjected to the
temperature and pressure, the object is isostatically pressed, thus
reducing porosity.
[0020] The heating module 204 is configured to control the chamber
temperature of the chamber 202. The heating module 204 can include
one or more heating elements 208 such as resistive heating
elements. In some examples, the one or more heating elements 208
lines an interior wall (or multiple interior walls) of the chamber
202. When a current is applied to the heating elements 208, the
heating elements 208 generate heat within the chamber 202. In
certain embodiments, the heating module 204 includes a temperature
sensor 210 configured to provide a chamber temperature measurement
to help adjust the amount of heat being delivered to the chamber
202.
[0021] The pressurizing module 206 is configured to change the
chamber pressure of the chamber 202. For example, the pressurizing
module 206 can control an inlet 212 and outlet 214 to the chamber
202 such that pressure in the chamber reaches and/or maintains a
target pressure. In certain embodiments, the pressurizing module
206 includes a pressure sensor 216 configured to measure the
chamber pressure to help adjust the amount and pressure of gas
being delivered to the chamber 202.
[0022] The apparatus 200 can include various components such as
firmware, integrated circuits, and/or software modules that
interact with each other or are combined together in one or more
controllers (e.g., application-specific integrated circuits,
field-programmable gate arrays, and/or other circuitry) to carry
out the methods and routines described herein. For example, the
apparatus 200 can include a computing device 218 with a controller
220, which has a microprocessor 222 and memory 224 (e.g., a
non-transitory computer-readable medium). The methods and routines
described herein can be carried out via instructions (e.g.,
firmware and/or software) stored on the memory 224 and executed by
the microprocessor 222. For example, the computing device 218 can
be coupled to components of the heating module 204 and the
pressurizing module 206 to control the temperature and pressure
within the chamber 202.
[0023] FIG. 4 shows an illustrative method 300 for making a hard
disk drive. In some examples, the method 300 includes a process 302
of forming a base deck, a process 304 of subjecting the base deck
to hot isostatic pressing, and a process 306 of welding a cover to
the base deck, optionally a process 308 of subjecting the base deck
to an impregnation process, and optionally a process 310 of filling
the hard disk drive with helium.
[0024] The process 302 of forming a base deck can include forming a
base deck comprising an aluminum alloy (e.g., ADC12, A380, and
A383) using vacuum casting. Although less expensive than other
processes for forming base decks, vacuum casting can result in base
decks being more porous than desired or than provided by other
processes. As described above, helium can leak from a base deck
that is too porous at one or more areas. Further, welding a base
deck that is too porous can be challenging. For example, when using
friction stir welding to attach a cover to the base deck, the
welding tool may "dig" too deep into the base deck causing damage
to the base deck or an otherwise unsatisfactory weld because the
porosity of the base deck results in a softer material.
[0025] The process 304 of subjecting the base deck to hot isostatic
pressing can be implemented using an illustrative process 400 shown
in FIG. 5. In some embodiments, the process 400 for subjecting a
base deck to hot isostatic pressing includes a process 402 of
placing the base deck in a chamber, a process 404 of modifying a
chamber temperature of the chamber, a process 406 of modifying a
chamber pressure of the chamber, and a process 408 of holding the
chamber temperature and the chamber pressure.
[0026] The process 404 of modifying a chamber temperature includes
raising the chamber temperature to a target temperature. The target
temperature can be a temperature substantially near a soludus
temperature of the base deck. For example, the aluminum alloy
referred to as "ADC12" has a soludus temperature of approximately
516.degree. C. The temperature in the chamber can be modified by
controlling heat generated by heating elements in the chamber.
Temperature can be measured by one or more temperature sensors
(e.g., thermocouples) and monitored to maintain the desired
temperature in the chamber. As one example, the chamber temperature
can be gradually increased from room temperature to a temperature
within a range of 450 to 550.degree. C. and held to that
temperature for a few hours.
[0027] The process 406 of modifying a chamber pressure includes
raising the chamber pressure to a target pressure. In certain
examples, the process 406 of raising a chamber pressure of the
chamber includes raising the chamber pressure to at least 1,000
psi, 5,000 psi, 10,000 psi, or 15,000 psi. For example, the chamber
pressure can be gradually increased from atmospheric pressure to a
pressure within a range of 10,000 to 15,000 psi and held to that
pressure for a few hours. In some examples, the process 406 of
raising a chamber pressure of the chamber includes introducing a
gas, such as an inert gas (e.g., Ar, He) into the chamber to
pressurize the chamber thereby pressurizing the base deck placed
within the chamber. The chamber pressure can be measured and
monitored using a pressure sensor. For example, the chamber
pressure can be adjusted by adjusting the amount of gas being
delivered to the chamber in response to a pressure measurements
from the pressure sensor.
[0028] In various embodiments, the process 408 of holding the
chamber temperature and the chamber pressure includes holding the
chamber temperature to a target temperature and the chamber
pressure at a target pressure for a predetermined time period. In
certain examples, the apparatus 200, the heating modulus 204,
and/or the pressurizing modulus 206 are configured to receive a
target condition including a target temperature, a target pressure,
one or more ramp rates, and/or one or more hold times.
[0029] Subjecting the base deck to hot isostatic pressing reduces
the porosity of the base deck. Porosity can be measured in terms of
a volume percentage and measured by a computerized tomography (CT)
scanner. Further, porosity of the base deck can be measured in
terms of total average porosity (e.g., the average porosity of the
entire base deck) or by porosity of a particular portion of the
base deck. For example, certain portions of the base deck that are
machined (e.g., external machined areas near a weld zone or
fastener holes; internal machined areas near thinner portions of
the base deck) are more likely to form a leak path or cause welding
problems than other portions of the base deck. Machining the base
deck can open up potential leak paths through which helium could
escape from the base deck. The process of hot isostatic pressing
can reduce the porosity of the base deck or particular portions
thereof by 50-99%.
[0030] Returning to FIG. 4, in various embodiments, the process 306
of welding a cover to the base deck can include using laser welding
or friction stir welding to couple the cover to the base deck. In
some embodiments, the process 308 of subjecting the base deck to an
impregnation process includes introducing an impregnating agent
into surface-connected porosity of the base deck. In certain
embodiments, the process 308 of subjecting the base deck to an
impregnation process is performed after the process 304 of
subjecting the base deck to hot isostatic pressing.
[0031] Various modifications and additions can be made to the
embodiments disclosed without departing from the scope of this
disclosure. For example, while the embodiments described above
refer to particular features, the scope of this disclosure also
includes embodiments having different combinations of features and
embodiments that do not include all of the described features.
Accordingly, the scope of the present disclosure is intended to
include all such alternatives, modifications, and variations as
falling within the scope of the claims, together with all
equivalents thereof.
* * * * *