KR100585177B1 - Method for determining grade of hard disk drives - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rating method for a hard disk drive in parallel with a hard disk manufacturing process, and more particularly, to a rating method for a hard disk drive in consideration of head characteristics.

The present invention comprises the steps of receiving a unique value of the parameter of the head component, measuring the parameter value of the hard disk drive assembled with the head component, the correlation between the parameters of the input head component and the parameter measured in the hard disk drive And a grade determining step of determining a reliability grade of recording / reproducing of the hard disk drive by comparing the calculated correlation with a reference value of a predetermined grade.

Description

{Method for determining grade of hard disk drives}

1 is a flowchart illustrating a general manufacturing process of a hard disk drive.

2 is a graph of magnetoresistance characteristics of a head in a hard disk drive.

3A to 3F are graphs showing the relationship between the magnetoresistance of the head and the magnetoresistance measured by the hard disk drive.

4 is a flowchart of a method for determining a hard disk rating according to the present invention.

FIG. 5 is a flowchart illustrating a specific embodiment of the rating step of FIG. 4.

The present invention relates to a test method of a hard disk drive, and in particular, the present invention, in determining the reliability or failure of recording / playback of a hard disk drive, determines the rating of a hard disk drive in consideration of the characteristics of components within a manufacturing process procedure. It is about a method.

Figure 1 shows the main procedure of the general manufacturing process of the hard disk drive for each step. First, the HDA (Head Disk Assembly) assembly process 100, which is a first step of the manufacturing process, is a process of assembling HDA, which is a mechanical part of a hard disk drive. The process takes place in a clean room. The servolite process 110, which is a second stage of the manufacturing process, is a process of recording a servo pattern for servo control of a magnetic head that reads data from a disk, which is a recording medium, or writes the data to a disk. This process is performed by a servo writer. The function test (120), which is the third step of the manufacturing process, is a test performed before combining the HDA made in the HDA assembly process and the PCBA made in the printed circuited board assembly (PCBA) assembly. Connect to the test PCBA and test whether it works properly. HDA, considered normal in this functional test process, is then combined with PCBA. The burn-in test process 130, which is a fourth step of the manufacturing process, is a process requiring the longest time (usually 8 hours to 16 hours) of the HDD manufacturing process. The process is performed on a rack in a high temperature, high humidity burn-in room without a separate test system and then performed according to its own program (firmware). In the burn-in test process, the defect part existing on the disc is found in advance, and the process of pre-determining the defect part is not used when the actual drive is used. The final test process 140 (final test), which is the fifth step of the manufacturing process, is a process for checking whether the HDD set passed in the burn-in test process is normally defected. This process uses a specific test system to test the defect status for each HDD set. After the final test process, the HDD set is released as a finished product through a shipment inspection process, a packaging and a shipment process 150, which are the sixth stages of the manufacturing process.

As the capacity increases, the main recording / reproducing characteristics of the drive are mostly determined by the single head characteristics. In particular, when the GMR head or the head with excellent sensitivity is adopted, the effect of the single part characteristic on the drive is very large. In general, according to the main parameters of the head component, the manufacturer of the head component or the like can properly classify the quality and filter out defects.

However, during assembly and testing of the hard disk drive, there is a possibility that the head parts may be defective or deteriorated. In this case, the characteristics predicted by the manufacturer of the head components are not displayed at the drive level. Therefore, rather than testing at the head component level, it is necessary to test what characteristics of the head component at the level of the assembled hard disk drive cause the performance or failure of the drive.

The above problem will be described with reference to the drawings.

In FIG. 2, the HSA refers to a state in which the head and the actuator arm are coupled, the horizontal axis of the graph shows the MRR value at the HSA stage, and the vertical axis of the graph shows the MRR value after applying the HSA to the drive. In the graph, when the MRR in the HSA stage is 42, the MRR after applying to the drive shows only about 39 values.

3A to 3F are graphs showing the relationship between the magnetoresistance of the head and the magnetoresistance measured by the hard disk drive. Each graph represents the values measured by different measuring devices. The QST on the axis and the number attached to it are marks that distinguish the measuring device. The horizontal axis of the graph is the magnetoresistance value of the head, and the vertical axis is the magnetoresistance value measured by the drive. In FIGS. 3C to 3F, the measurement values of the magnetoresistance are concentrated on the central axis, while in FIG. 3A and FIG. 3B, it can be seen to be scattered. As the measured value of the magnetoresistance deviates from the central axis, the magnetoresistance characteristic of the head means that the characteristic of the head is unstable. This is directly related to the reliability of recording / playback of the drive.

Conventionally, there was a defect detection method that infers the defects of the head parts at the level of the assembled hard disk drive, but it was only to infer the defects of the head or PCBA among the parts of the drive by looking at the distribution of defects on the hard disk. Patent Registration No. 2001-0094680). However, such a method may cause a problem of failing to deduce a defect of a specific component according to the Defect's analysis method, and it is not possible to classify the degree that the component contributes to the performance of the hard disk drive.

The technical problem to be achieved by the present invention is to measure how the characteristics of the head component changes during the manufacturing process of the hard disk drive, to provide a criterion to design the drive in consideration of the characteristics of the head component, the performance of the assembled drive ( Drive Performance) is evaluated and classified by performance, and defects are to be detected.

In order to achieve the above technical problem, the present invention comprises the steps of receiving a unique value of the parameter for the head component, measuring the parameter value of the hard disk drive assembled with the head component for each manufacturing process step, the head component Calculating the correlation between the intrinsic value of the parameter and the parameter value measured in the hard disk drive, and comparing the calculated correlation with a reference value of a predetermined rating to determine the reliability level of the recording / playback of the hard disk drive. Determination is composed of a rating step.

Hereinafter, a configuration of the present invention will be described with reference to the accompanying drawings.

4 is a flowchart illustrating a method of determining a rating of a hard disk according to the present invention.

Referring to FIG. 4, first, a unique value of a parameter for a head component is input (400). This step may be performed through a terminal of a tester or automatically receiving a corresponding value. The intrinsic values of the parameters of the head component are specific values relating to the physical characteristics originally possessed by the head component, and most of the time are related to the recording / reproducing characteristics of the hard disk. These eigenvalues are usually presented from the manufacturer of the head part.

The parameter values of the drive are then measured (411-413). In this step, the parameter values of the drive are measured by various measuring devices from the assembled hard disk drive, and parameters corresponding to the parameters of the head components must be used.

Subsequently, a correlation between the parameters of the head component and the parameters of the drive is calculated through a mathematical operation (420). Correlation should be calculated for each of the parameters of the corresponding physical properties. This step is preferably performed by a variety of computing devices or computers connected to the measuring device for the parameter.

Next, according to the calculated correlation, the reliability level of the hard disk drive is determined (430). This step consists of a process of comparing and calculating the pre-determined reference values related to the calculated correlation and the manufacture of the hard disk and allocating the grades accordingly. This step is preferably performed by a variety of computing devices or computers connected to the parameter measuring device, as in the step of calculating the correlation. The confidence level is displayed on the display device connected to the computer or on the computing device that performed the calculation of the correlation. It is desirable to allow test personnel to recognize the grades judged.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

In FIG. 4, steps 411-413 of receiving the unique values of the parameters of the head components are preferably performed before the parameter measurement of the drive in the functional test process. In addition, it is preferable to input the unique value of the parameter from the head component into the maintenance area MC of the hard disk. Measuring the parameter values of the drive (411 to 413) is a function test process 120 after the assembly of the hard disk using the head component, the functional test process 120, burn-in test process 130, the final test process 140 It is preferable to measure the parameter value of the hard disk drive at each of the s) and store it in the maintenance area MC.

Among the parameters, the parameters of the head components include the magnetic write width (MWW) of the head, the magnetic resistance (MRR) of the head, the track average amplitude (TAA), and the asymmetric average track width (TAAA). : Track Average Amplitude Asymmetry, and the parameters measured by the hard disk drive are the amplitude, asymmetry, and average track width estimated from the gain of the AGC (Auto Gain Control). It is preferably characterized in that it is a measured value of track per inch (TPI) and magnetic resistance (MRR) of the head.

The parameter of the head component means the inherent characteristic of the head, which is expected according to the criteria set by the manufacturer of the head, and the magnetic recording width (MWW) of the head is the expected recordable width on the disc. The magnetic resistance (MRR) of the head is a measure of the strength of the magnetic field formed from the head. The average track width (TAA) is the width of the track that the head is expected to cover average. The asymmetric mean track width (TAAA) is the extent to which the head is off average from the center of the track.

The parameter measured on the hard disk drive is an actual measurement of the characteristic that appears as the actual head operates on the disk. The average track width (Amplitude) is an automatic gain control (AGC) for measuring the magnetic recording width of the head at the drive level. In this case, it is a measure using the characteristic that the gain size becomes small when the actual magnetic recording width is large. Asymmetry is the degree to which the head deviates from the center of the track when it is actually running on the disc. The number of tracks per unit inch (TPI) is theoretically proportional to the average track width (TAA) of the head since the number of tracks per unit inch of the hard disk is determined by how much track width the head can actually cover. The magnetoresistance (MRR) of the head, unlike the inherent parameters of the head, is actually the value of the magnetoresistance measured by a device that measures the magnetoresistance on the drive.

5 illustrates a specific embodiment of the rating step 430.

In the grade determination step 430 of the present invention, the process of determining the grade for each characteristic of the head corresponding to each parameter, in addition to the grade of the entire drive, according to the correlation between the head and the parameter values of the drive ( It is preferable to include the 510 so that the product is classified by characteristics. The overall rating determination 530 of the drive is preferably based on the rating for each characteristic. In addition, in addition to the step 500 of comparing the degree of correlation out of a predetermined allowance with respect to the failure of the drive in the rating step 430 of the present invention, if it is outside the allowable range is determined as a bad hard disk drive Preferably, the process 520 is included. The determination of the grade or the determination of the failure is preferably made to be performed by a computing device or a computer that performs calculation of the correlation.

The following shows an example of assigning grades for each characteristic when using TAA, TAAA, MWW, MRR as parameters of the head components, and AGC, Asymmetry, TPI, MRR as parameters of the drive.

function test Burn-in test 1 Burn-in Test 2 Final test 1 Final test 2 Rating TAA vs AGC 1.2 1.3 1.5 ... ... A TAAA vs Asymmetry 5 7 7 ... ... A MWW vs TPI ... 4 4 ... ... A MRR vs MRR 5 5 5 ... ... A

In the above example, the average track width (TAA), asymmetry (TAAA), magnetic recording width (MWW), and magnetoresistance (MRR) of the head have high correlations in the drive. If it is.

Which grade is given to which correlation may be arbitrarily determined by the manufacturer or the like. In addition, the overall rating of the drive can be determined based on the rating of each characteristic.

In addition, as described above, an expert system for measuring each parameter, calculating a correlation, and performing grade determination and defect detection may be implemented.

On the other hand, in the description of the present invention has been described with respect to specific embodiments, it can be carried out in various ways without departing from the scope of the invention. Even if the manufacturing process of the hard disk is slightly changed, the method for determining the hard disk according to the present invention can be implemented. In particular, the parameters to be measured can be flexibly changed as required by the manufacturer. It is up to the manufacturer's needs to decide what grade to give for a good grade. Accordingly, the scope of the invention should not be defined by the described embodiments, but rather by the claims and their equivalents.

The present invention is effective in examining how each characteristic of a component is deformed at the drive level, and classifying the drive grade and filtering defects based on the characteristics according to the purpose or use of the drive. In particular, if there is a problem with the drive, you can pinpoint which part is causing the problem. This is an effective way for OEMs to deliver products selectively, depending on their use and required reliability.

In addition, the statistical analysis between the head parameter and the drive parameter is effective in designing the process for the head component and the drive.

Claims (5)

In the hard disk drive grading method in parallel with a series of hard disk manufacturing process procedures, (a) receiving an intrinsic value of a parameter for the head component; (b) measuring parameter values of the hard disk drive assembled with the head component for each manufacturing process step; (c) calculating a correlation between the intrinsic value of the parameter for the head component and the parameter value measured in the hard disk drive; and (d) a rating judgment step of determining a reliability rating of recording / reproducing of the hard disk drive by comparing the calculated correlation with the reference value of each rating. The method of claim 1, The step (d) further comprises the step of determining the grade for each characteristic corresponding to each parameter by comparing the correlation between the parameter intrinsic value for the head component and the parameter value of the drive with the reference value of each class How to grade a disk drive. The method of claim 1, The step (d) further includes the step of comparing the predetermined tolerance and the degree of correlation with respect to the failure of the drive, and if it is out of the tolerance range further comprises the step of determining as a bad hard disk drive How to grade a hard disk drive. The method of claim 1, Step (a) is performed in the functional test process, characterized in that the intrinsic value of the parameter for the head component is input to the maintenance area (MC) of the hard disk, The step (b) is performed in each of the functional test process, the burn-in test process, and the final test process, wherein each measured parameter value is stored in the maintenance area MC of the hard disk. Rating method. The method according to any one of claims 1 to 4, Among the parameters, the parameters of the head component are the magnetic recording width (MWW) of the head, the magnetoresistance (MRR) of the head, the average track width (TAA), the asymmetric average track width (TAAA), The parameters measured on the hard disk are the average track width (Amplitude) estimated during the automatic gain control (AGC) process, the degree of head deviation from the track's center (Asymmetry), the number of tracks per unit (TPI), and the magnetoresistance. (MRR) is a measured value, characterized in that the rating method of the hard disk drive.

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