A method for preparing a glass substrate for a mechanical hard disk

Abstract

The application provides a preparation method of a glass substrate for a mechanical hard disk, which cuts a glass mother substrate into a substrate small piece, forms an outer circular surface, an inner circular surface and an inverted edge surface through numerical control forming, and then sequentially performs rough polishing, scanning polishing and fine polishing. The scanning polishing is performed between the rough polishing and the fine polishing to perform lateral trimming. The fine polishing gradually converges surface roughness, microscopic waviness and nanometer waviness. The glass substrate is prepared through ultrasonic dust-free cleaning. The application adopts glass, reduces the migration pollution risk of alkali metal ions, controls the edge geometry of the junction between the outer circular surface and the end surface, and prepares the glass substrate with a flat end surface, and the outer circular surface and the end surface are gently connected through the inverted edge surface.

Description

Technical Field

[0001] This application relates to the field of precision glass component manufacturing technology for hard disk drives, and specifically to a method for preparing a glass substrate for hard disk drives. Background Technology

[0002] In hard disk drives and other mechanical hard disk drives, the magnetic recording medium is supported by a substrate. The material properties, surface forming accuracy, and edge geometry of the substrate directly determine the storage density, long-term signal stability, and device service reliability.

[0003] Existing substrates mostly use alkali metal-containing materials or aluminum alloys. When using alkali metal-containing materials, they contain alkali metal oxides. Under the high temperature and electric field coupling environment of long-term service, alkali metal ions are prone to migrate and precipitate to the surface, causing ion contamination of adjacent magnetic recording layers and control devices, leading to signal degradation and device failure. Aluminum alloys, on the other hand, have insufficient rigidity and large deformation at high temperatures, making it difficult to support the operating requirements of high-speed and high-density storage.

[0004] In the precision fabrication of substrates, existing methods often employ single or two-stage polishing processes, which make it difficult to balance fabrication efficiency and surface precision. If large-particle abrasives are used to quickly remove the damaged layer, the surface roughness, micro-ripples, and nano-ripples are difficult to converge to the requirements of high-density storage. If fine-particle abrasives are used for fine polishing, the fabrication cycle is long, the material removal efficiency is low, and the deviation in surface shape and total thickness is difficult to control.

[0005] In addition, the existing process directly performs fine polishing after rough polishing, lacking the intermediate lateral finishing steps for the outer circular surface, inner circular surface and chamfered surface. Defects such as side lines and chipped edges are easy to flow into subsequent processes, and geometric abrupt changes in the edge area can also affect the stability of the magnetic head flight and reduce the yield of finished products. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention reduces the risk of alkali metal ion migration and contamination by multi-stage glass polishing and edge geometry control, balancing polishing efficiency and surface precision while controlling edge geometry.

[0007] To achieve the above objectives, the present invention provides a method for preparing a glass substrate for a hard disk drive: providing a glass mother plate, cutting the glass mother plate into substrate pieces; performing CNC forming on the substrate pieces to form an outer circular surface, an inner circular surface, and chamfered surfaces that connect with two end faces respectively; sequentially performing rough polishing, sweep polishing, and fine polishing on the CNC-formed substrate pieces, wherein the sweep polishing trims the outer and inner circular surfaces of the substrate pieces; and performing ultrasonic dust-free cleaning on the polished substrate pieces to obtain the glass substrate.

[0008] Furthermore, the glass motherboard is made of high-temperature resistant glass, which is suitable for the high-temperature process in the assembly of mechanical hard drives, reducing the risk of alkali metal ion migration causing contamination to the magnetic recording layer and control devices.

[0009] Furthermore, the rough polishing adopts a double-sided polishing method, which is used to remove material from the two opposite end faces of the substrate piece at the same time, ensuring the basic surface accuracy with a high material removal rate.

[0010] Furthermore, the polishing process laterally trims the outer and inner circular surfaces of the substrate piece, as well as the chamfered surfaces where the outer and inner circular surfaces connect to the two end faces, to remove chipped edges, lines, and pits on the outer, inner, and chamfered surfaces.

[0011] When performing lateral trimming on the edge area, the sweeping and polishing process trims the outer circular surface, inner circular surface, and chamfered surface of the substrate piece, and reduces the surface roughness of the outer circular surface, the inner circular surface, and the chamfered surface.

[0012] Furthermore, the fine polishing includes a first fine polishing and a second fine polishing performed sequentially. The second fine polishing is performed after the first fine polishing, and the end face of the substrate piece is finely polished again to gradually improve the surface quality of the end face.

[0013] Furthermore, the CNC forming includes a first precision carving and a second precision carving performed sequentially. The second precision carving ensures the shape accuracy and positional accuracy of the outer circle and the inner circle, and performs chamfering on the outer circle surface and the inner circle surface respectively.

[0014] In one embodiment, after the fine polishing and before the ultrasonic dust-free cleaning, the substrate piece is re-scanned to perform secondary edge finishing on any remaining edge defects after the polishing.

[0015] After polishing and cleaning, the resulting glass substrate has a flat end face, and the outer circular surface and the end face are smoothly connected by a chamfered surface.

[0016] Compared with the prior art, the present invention has the following advantages: First, it reduces the risk of alkali metal ion migration. Using glass as the carrier substrate reduces the risk of alkali metal ion migration and contamination of the magnetic recording layer and control devices under high temperature and electric field coupling environments. Furthermore, this glass is high-temperature resistant, making it compatible with the high-temperature assembly process of mechanical hard drives.

[0017] Second, multi-stage progressive polishing balances preparation efficiency and surface precision. Rough polishing removes forming damage, sweeping polishing trims the sides, and fine polishing refines surface quality. Rough polishing ensures material removal efficiency and basic surface shape, sweeping polishing fills in the gaps in the side forming process, and fine polishing progressively tightens the control limits of surface roughness, micro-ripples, and nano-ripples, achieving high thickness consistency and surface smoothness simultaneously within a reasonable preparation cycle.

[0018] Third, quantitative control of edge geometry reduces the risk of head flight. By controlling the edge geometry through sweeping and polishing, abrupt changes and microcracks in edge geometry are reduced, which not only reduces the risk of head flight instability but also reduces the accumulation of particulate contaminants. Attached Figure Description

[0019] The accompanying drawings exemplify embodiments and form part of the specification, working together with the textual description to explain exemplary implementations of the embodiments. The drawings shown are for illustrative purposes only and do not limit the scope of the claims. Throughout the drawings, the same reference numerals refer to similar but not necessarily identical elements.

[0020] Figure 1 is a flowchart of a method for preparing a glass substrate for a hard disk drive according to the present invention. Detailed Implementation

[0021] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] In the description of the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. The term "multiple" means two or more, unless otherwise explicitly specified. The term "comprising" indicates the presence of the described feature, whole, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or sets thereof. The term "and / or" describes the relationship between related objects, indicating that three relationships may exist. For example, A and / or B may include three cases: A existing alone, A and B existing simultaneously, and B existing alone. The character " / " generally indicates that the related objects before and after are in an "or" relationship.

[0024] Unless otherwise defined, all technical terms used in the embodiments of this application have the same meaning as commonly understood by one of ordinary skill in the art; the terms used in the embodiments of this application are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "comprising" and "having" and any variations thereof in the specification, claims and foregoing description of the drawings of this application are intended to cover non-exclusive inclusion.

[0025] Furthermore, terms such as "exemplary," "for example," and "optional" are used to indicate illustrative purposes. Any technical solution described by the above terms in the embodiments of this application should not be construed as being more preferred or advantageous than other technical solutions. Specifically, these terms are intended to present the relevant technical concepts in terms of specific implementation methods.

[0026] Figure 1 shows a flowchart of a method for preparing a glass substrate for a hard disk drive according to the present invention; it includes the following steps: S1: Provide a glass mother plate, and cut the glass mother plate into small substrate pieces; S2: The substrate piece is CNC shaped to form the outer circular surface, inner circular surface, and chamfered surfaces that connect with the two end faces respectively. S3: The substrate piece after CNC forming is subjected to rough polishing, sweep polishing and fine polishing in sequence. The sweep polishing trims the outer and inner circular surfaces of the substrate piece. S4: The polished substrate piece is subjected to ultrasonic dust-free cleaning to obtain the glass substrate.

[0027] The specific implementation is as follows: First, the glass mother plate is diced and cut into small substrate pieces, and the cutting size tolerance is controlled within ±0.1mm.

[0028] The substrate piece is CNC shaped by performing a first fine carving and a second fine carving to complete the rough and fine shaping of the shape, forming the outer circular surface, inner circular surface, and chamfered surfaces that connect with the two end faces of the substrate piece; wherein the second fine carving controls the roundness of the outer and inner circular surfaces to be less than 6μm and the concentricity to be less than 7.5μm, and chamfers are formed on the outer and inner circular surfaces respectively.

[0029] The substrate pieces are then subjected to multi-stage polishing processes.

[0030] Rough polishing uses a double-sided polishing device to remove the forming damage layer on the surface of the substrate piece, and controls the thickness tolerance of the substrate piece to be ±0.0005mm, the total thickness deviation TTV to be no greater than 0.5μm, the surface roughness to be no greater than 8μm, the surface roughness Ra to be no greater than 0.8nm, the micro-ripple to be no greater than 0.4nm, and the nano-ripple to be no greater than 0.25nm.

[0031] The sweeping and polishing process laterally trims the outer and inner circular surfaces of the substrate piece, as well as the chamfered surfaces where the outer and inner circular surfaces connect to the two end faces, to remove chipping, line marks, and pits on the aforementioned surfaces. This ensures that the edge collapse of the substrate piece is between -15nm and 40nm, and that the collapse radius at the junction of the outer circular surface and the end face is greater than 47.77mm. Simultaneously, it ensures that the outer circular surface, the inner circular surface, and the chamfered surfaces have smooth surfaces.

[0032] The fine polishing process is divided into two stages of convergence: the first fine polishing controls the end face Ra to be no greater than 0.25nm, the micro-ripple to be no greater than 0.2nm, and the nano-ripple to be no greater than 0.09nm; the second fine polishing controls the end face Ra to be no greater than 0.15nm, the micro-ripple to be no greater than 0.15nm, and the nano-ripple to be no greater than 0.07nm; both the first and second fine polishing processes maintain a thickness tolerance of ±0.0005mm, a total thickness deviation (TTV) of no greater than 0.5μm, and a surface profile of no greater than 8μm.

[0033] After fine polishing, a second edge finishing process is performed to address any minor edge imperfections remaining after the first polishing.

[0034] The glass substrate was then cleaned using ultrasonic dust-free cleaning to remove polishing residue, oil, and micro-dust, resulting in the substrate. Atomic force microscopy was used to measure the surface roughness Ra of the end face to be less than 0.2 nm, the micro-waviness to be less than 0.15 nm, and the nano-waviness to be less than 0.07 nm. The surface roughness Ra of the outer circular surface, inner circular surface, and chamfered surface was all less than 80 nm. The collapse radius at the junction of the outer circular surface and the end face was greater than 47.77 mm, the surface profile to be less than 9.9 μm, and the total thickness deviation (TTV) to be less than 1 μm. In this invention, both micro-waviness and nano-waviness are parameters characterizing the surface undulation of the substrate end face: nano-waviness corresponds to the high-frequency component with a shorter spatial wavelength, while micro-waviness corresponds to the low-frequency component with a longer spatial wavelength. The surface profile characterizes the overall surface accuracy of the substrate end face.

[0035] The glass substrate of this embodiment has two opposing end faces. The two end faces are respectively connected to the outer circular surface surrounding its outer periphery and the inner circular surface forming the central hole via chamfered surfaces, and the connection between the outer circular surface and the end face is smoothly transitioned by the chamfered surfaces.

[0036] This glass substrate is assembled in a hard disk drive (HDD) as the carrier of the magnetic recording medium. The central hole fits into the spindle, and the magnetic recording medium is formed on the end face. Because the substrate is made of high-temperature resistant glass, it has a low risk of ion migration and good thermal stability in high-temperature environments, ensuring stable magnetic head flight and supporting higher storage density and higher rotational speed operation.

[0037] The above embodiments are only used to illustrate the present application and are not intended to limit it. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included within the protection scope of the present application.

Claims

1. A method for preparing a glass substrate for a hard disk drive, characterized in that, The process includes the following steps: providing a glass mother plate and cutting the glass mother plate into substrate pieces; performing CNC forming on the substrate pieces to form an outer circular surface, an inner circular surface, and chamfered surfaces that connect with the two end faces; sequentially performing rough polishing, sweep polishing, and fine polishing on the CNC-formed substrate pieces, wherein the sweep polishing trims the outer and inner circular surfaces of the substrate pieces; and performing ultrasonic dust-free cleaning on the polished substrate pieces to obtain the glass substrate.

2. The preparation method according to claim 1, characterized in that, The sweeping and polishing process involves lateral trimming of the outer and inner circular surfaces of the substrate piece, as well as the chamfered surfaces where the outer and inner circular surfaces connect to the two end faces.

3. The preparation method according to claim 2, characterized in that, The sweeping and polishing process laterally trims the edge area of ​​the substrate piece and reduces the surface roughness of the outer circular surface, the inner circular surface, and the chamfered surface.

4. The preparation method according to claim 1, characterized in that, The CNC forming process includes a first precision carving and a second precision carving performed sequentially. The second precision carving ensures the shape and positional accuracy of the outer and inner circles, and performs chamfering on the outer and inner circular surfaces respectively.

5. The preparation method according to claim 1, characterized in that, After the fine polishing and before the ultrasonic dust-free cleaning, the substrate piece is also re-scanned to perform secondary edge finishing on any remaining edge defects after the polishing.

6. The preparation method according to claim 1, characterized in that, After ultrasonic dust-free cleaning, the resulting glass substrate has a flat end face, and the connection between the outer circular surface and the end face is smoothly connected by a chamfered surface.

Images