US20200402546A1

US20200402546A1 - Reducing base deck porosity

Info

Publication number: US20200402546A1
Application number: US16/891,397
Authority: US
Inventors: Jerome Thomas Coffey
Original assignee: Seagate Technology LLC
Current assignee: Seagate Technology LLC
Priority date: 2019-06-24
Filing date: 2020-06-03
Publication date: 2020-12-24
Also published as: US20220070443A1; US11665339B2; US11202064B2; US20200404253A1

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.

Description

RELATED APPLICATIONS

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

Certain embodiments of the present disclosure relate to systems and methods for reducing base deck porosity using hot isostatic pressing.

SUMMARY

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.
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%.
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.
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

FIG. 1 shows a cut-away side view of a hard drive, in accordance with certain embodiments of the present disclosure.

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.

FIG. 3 shows an apparatus for subjecting a base deck to hot isostatic pressing, in accordance with certain embodiments of the present disclosure.

FIG. 4 shows an illustrative method for making a hard disk drive, in accordance with certain embodiments of the present disclosure.

FIG. 5 shows an illustrative process for subjecting a base deck to hot isostatic pressing, in accordance with certain embodiments of the present disclosure.

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

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.
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.
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.
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
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° 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° C. and held to that temperature for a few hours.
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.
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.
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%.
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.
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.

Claims

I claim:

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.