JPH01201816A - Inspection method and inspection device for transducer for thin film magnetic head - Google Patents

Abstract

PURPOSE:To heighten the accuracy of selection by impressing a current and/or a magnetic field on a transducer on a substrate, and selecting a defective head generating a wiggle based on an obtained voltage signal. CONSTITUTION:The output of a high frequency signal source 1 is permitted to flow on the connection terminal of the transducer 4 to be inspected on the substrate via a probe stylus 13. Next, the fluctuation of the impedance of the transducer 4 is taken out at a bridge circuit 5, and its output signal is amplified by an amplifier 7. Following that, after a desired frequency component being taken out at a filter circuit 8, it is compared with the setting level of a normal transducer set in advance, and when it exceeds the level, a signal representing the defect of the head is outputted from a comparator 9. Also, it is possible to provide an initialization signal source 10 to generate the signal which performs the setting of a magnetic state, a magnetic field impression device 11 to impress the magnetic field, and a signal source 12 to generate a signal of low frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and an inspection apparatus for inspecting the performance of a transducer in a thin film magnetic head manufacturing process. A transducer that is inspected according to the present invention and determined to be non-defective is processed into a slider and incorporated into a magnetic disk drive. This magnetic disk device is suitable for use as an external storage device for a computer.

[Conventional technology]

For example, as shown in Japanese Unexamined Patent Publication No. 55-84019, a thin film magnetic head consists of a magnetic film that becomes a magnetic pole when the head is completed, a nonmagnetic film that forms a gap, a conductor film that allows current to flow, on a nonmagnetic substrate. and an insulating film for insulating the conductor film from other parts, which are successively patterned using thin film fabrication technology to form a desired shape, and stacked to form a large number of transducer parts for recording and reproducing. The substrate is then cut to separate individual chips, ie, transducers, and processed into a slider shape suitable for floating above a rotating medium to obtain a magnetic head.

A magnetic thin film such as permalloy used in a transducer of a thin film magnetic head has a magnetic domain structure divided into many regions due to the inherent magnetic properties of the magnetic thin film and the demagnetizing field caused by its shape. The characteristics of a magnetic thin film with this magnetic domain structure are largely influenced by the behavior of the magnetic domains, so it is difficult to understand them in detail using only macroscopic magnetic properties such as coercive force and anisotropic magnetic field. "Wiggle" is known as one of the phenomena peculiar to thin film magnetic heads due to the influence of such magnetic domains. This phenomenon occurs because even when recording is performed under the same conditions, the reproduced output waveform fluctuates each time a write is performed, and a protrusion-like distortion waveform is observed in the reproduced waveform. This phenomenon is a problem in ensuring reliability during reproduction of thin-film magnetic heads. becomes a big problem.

Regarding this “Wiggle” phenomenon, please refer to Japanese Patent Application Laid-Open No. 58-194.
It is described in Publication No. 125.

"Wiggle" occurs when information recorded on a magnetic recording medium is read by a thin-film magnetic head, and the thin-film magnetic head is a defective product.The information recorded on the magnetic recording medium is accurate. However, if the thin film magnetic head used to read this information is defective, a "wiggle" will occur in the reproduced waveform, resulting in an error in the read information.

For this reason, it is necessary to perform inspections at each stage of manufacturing to prevent such defective products from being mixed into the products that are finally shipped. In particular, with thin-film magnetic heads, many transducers are simultaneously formed on one substrate in the pre-manufacturing stage before the transducers for recording and reproduction are formed on the substrate. In the later stage of manufacturing, in which each slider is processed into a slider, each slider is individually processed, so the manufacturing cost in this later stage accounts for a large proportion. Therefore, the removal of defective products before entering the latter stage has a particularly important meaning.

Conventionally, the method of inspecting individual heads that have been processed into a slider state is to levitate the individual heads above a rotating magnetic disk and actually perform recording and playback to sort out good and defective heads. be. In addition, as a method for easily testing this product, we have developed
, a method for selecting wiggle products based on differences in impedance, especially frequency characteristics of inductance, when a transducer is demagnetized, magnetized, or saturated is shown.

[Problem to be solved by the invention]

The method of actually recording and reproducing by setting a head on a rotating magnetic disk not only takes time to set up, but also causes fluctuations in the magnetization state of the recording medium, fluctuations in the flying height of the head, and fluctuations in the rotation of the disk. There are problems in that highly accurate selection cannot be performed due to the presence of various fluctuations, and furthermore, it is difficult to quantify the waveforms of normal and abnormal, requiring an operator to make the determination.

In addition, in order to actually record and play back, it is necessary to attach a spring to the slider that is necessary to levitate the disk, and considering that it has already become a high value-added product at the inspection stage, this situation is difficult to understand. It is not recommended to test with

In the method of sorting based on the variation in inductance due to the magnetization state of the thin-film magnetic head, the inductance of the thin-film magnetic head is extremely small, about 0.2 μH, and furthermore, even after it is saturated, the overall change is small. Since the difference is extremely small, less than one tenth of It merely evaluates the quality of regeneration performance based on the electrical performance.

The purpose of the present invention is to provide an inspection system that can accurately screen out defective heads that cause reproduction waveform distortion, or "wiggle," which is unique to thin-film magnetic heads, at any time after the completion of a transducer for recording and reproduction on a substrate. The present invention provides a method and testing device.

Another object of the present invention is to provide a method for manufacturing a thin film magnetic head that includes a "wiggle" inspection during the manufacturing process of the thin film magnetic head.

[Means to solve the problem]

The present invention is to select defective heads that cause "wiggle" based on a voltage signal obtained by applying at least one of a current and a magnetic field to a transducer on a substrate.

In the present invention, the term "transducer" refers to a device in which a magnetic film, a non-magnetic film, a conductive film, and an insulating film are patterned on a substrate using a thin film fabrication technique, and has a function as an electromagnetic transducer.

The present invention is based on the fact that the "wiggle" phenomenon of thin-film magnetic heads occurs because the magnetic domain structure of a magnetic film such as permalloy or Kkkeru iron alloy changes in response to an externally applied magnetic field, resulting in an undesirable structure for a magnetic head. It has been determined that this undesirable change in magnetic domain structure can affect the voltage signal output observed from the terminals of the transducer.

Inspection of a defective head in the present invention may be performed at any time after the transducer is formed on the substrate by thin film fabrication technology. The most desirable inspection period is between the time when a plurality of transducers are formed on the substrate and the time when the substrate is cut into individual transducers. This is the easiest time to inspect since many transducers are formed on the same substrate.

The next most desirable inspection period is after the substrate is cut into transducers and before it is processed into a slider shape. At this time, the transducers are separated one by one, so compared to the time when many transducers are formed on one board, it is easier to install the transducer to be tested on the inspection equipment. It takes a lot of effort. However, it is possible to eliminate the waste of processing a defective transducer into a slider shape.

The inspection method of the present invention can be carried out by applying a current or a magnetic field to the transducer from the outside. It is also possible to apply a current and a magnetic field in a superimposed manner.

When applying current to the transducer, it is desirable to apply an alternating current constant current. This inspection method that applies current can apply a magnetic field in the direction of the transducer's hard-magnetization axis, and output the transducer's voltage signal to detect the "wiggle" phenomenon caused by changes in the magnetic domain structure in the direction of the hard-magnetization axis. can be inspected based on

The inspection method of applying a magnetic field to the transducer from the outside does not create a high-frequency magnetic field, but it has the effect of being able to apply the magnetic field in both the easy magnetization axis direction and the magnetization Tanabe axis direction.

The method of applying a superimposed alternating current constant current signal and magnetic field signal to a transducer allows the application of a magnetic field in both the easy magnetization axis direction and the hard magnetization axis direction. This has the effect of creating a magnetic field in the axial direction. This is an extremely effective inspection method that combines the advantages of both inspection methods that apply an electric current and those that apply a magnetic field.

The voltage signal obtained by applying one or both of a current and a magnetic field to a transducer can be expressed as an output waveform that shows the relationship between voltage and time, or can be expressed as an output waveform that shows the relationship between power and frequency by frequency decomposing the voltage signal output. It is desirable to represent it in a waveform. If there is a localized sudden change in the output waveform of the relationship between voltage and signal, it can be determined that the product is defective. Further, it is possible to determine as a defective product if there is a portion where the harmonic sideband output obtained by frequency decomposing the voltage signal output is large.

Normal transducers and defective transducers can be sorted visually, or by preparing a model of the output waveform of a normal transducer and comparing it with this model. The selection of defective transducers by comparison with the user's output waveform model may be performed visually or automatically by mechanization.

Inspection method that applies two or more current signals with different frequencies to a transducer 9 Inspection methods that apply magnetic field signals with different frequencies and inspection methods that apply a current signal and a magnetic field signal in a superimposed manner. Among the harmonic components of a voltage signal, in particular, the sum of frequencies that are integral multiples of the original frequency, or the fluctuation in the output of the difference frequency component, is detected to select transducers that have poor recording/reproducing characteristics. is highly desirable. By doing so, the sensitivity for selecting defective transducers can be further increased.

Furthermore, from this point on, it is an extremely desirable determination method to determine that a transducer with a large sideband output adjacent to a harmonic is a defective transducer. We discovered that the voltage signal output caused by the "wiggle" phenomenon appears as fluctuations in sidebands adjacent to the harmonics obtained by frequency decomposition, and that this makes it easier to identify defective transducers. Ta.

Defective transducers may be selected by detecting fluctuations in the output of harmonic components of voltage signals obtained by applying two or more current signals with different frequencies to the transducer. Similarly, defective transducers may be selected by detecting fluctuations in the output of harmonic components of voltage signals obtained by applying two or more magnetic field signals having different frequencies to the transducer.

By doing so, one current signal composition can increase the sensitivity for selecting defective transducers compared to the case where only one magnetic field signal is applied.

When applying a current signal and a magnetic field signal in a superimposed manner to a transducer, two or more signals with different frequencies may be applied from one or both of them to apply a total of three or more signals, This application method is a highly preferred method.

By doing this, in addition to the effect of the method of applying one current signal and one magnetic field signal in a superimposed manner, it is possible to further increase the sensitivity for selecting defective transducers.

Waveform distortion caused by "wiggle" is most likely to appear in the sideband adjacent to the second harmonic, and therefore it is easiest to detect the output fluctuation here to screen out defective transducers. Highly reliable.

One of the inspection apparatuses of the present invention includes a current signal power supply for applying an alternating current constant current signal to a transducer, and means for measuring a connection terminal voltage of the transducer and displaying the measured voltage as a reproduced waveform.

The other one includes a magnetic field signal power source for applying a magnetic field signal to the transducer and means for measuring the voltage at the connecting terminal of the transducer and displaying it as a reproduced waveform.

The other components are a current signal power supply for applying an alternating current constant current to the transducer, a magnetic field signal power supply for applying a magnetic field signal, and measuring the voltage at the connecting terminals of the transducer and displaying it as a reproduced waveform. have means to do so.

In addition to the above-mentioned means for displaying the connection terminal voltage between the signal power source and the transducer as a reproduced waveform, the inspection device of the present invention includes means for amplifying the output voltage from the connection terminal so as to extract a desired frequency component. Other means may also be included. Note that, for example, a high frequency amplifier can be used as the amplifying means.

By incorporating the inspection method of the present invention into the process of manufacturing a thin film magnetic head, the following (a) can be achieved.

(b) The thin film magnetic head manufacturing process becomes possible.

(a) At the stage when a large number of transducers are formed on the board, defective transducers are sorted out, the board is cut to separate the transducers individually, and only the normal transducers are shaped into sliders. Processed to create a thin film magnetic head.

(b) After forming a large number of transducers on a board, the board is cut to separate the transducers individually, and then an inspection is performed to screen out defective transducers, and only normal transducers are shaped into sliders. Processed to create a thin film magnetic head.

When performing a screening inspection for defective transducers after a large number of transducers have been formed on the board, assign an address to each transducer and register the inspection results for each address. is desirable. When testing transducers automatically, it is effective to assign an address to each transducer and to manage defective products by address.

According to the present invention, there is provided a transducer manufacturing system for forming a large number of transducers on a substrate by thin film manufacturing technology, and applying at least one of a current signal and a magnetic field signal to the large number of transducers fabricated in the system. An inspection system that selects defective transducers based on the voltage signal obtained by cutting the board, a cutting system that separates the transducers into individual transducers by cutting the board, and a system that processes the cut board into a slider shape or A thin film magnetic head manufacturing system including a thin film magnetic head finishing system for finishing a final product by separately layering a slider can be obtained.

It goes without saying that the system for cutting the substrate and the inspection system for selecting defective transducers may be replaced, and the inspection system may be positioned after the substrate cutting system to perform inspection after cutting the substrate.

[Function] - The reason why the "wiggle" phenomenon occurs in the reproduced waveform by a thin-film magnetic head is that the magnetic domain structure of the magnetic film of the thin-film magnetic head changes, resulting in a structure that is not desirable for a magnetic head.

N used in transducer of thin film magnetic head
The magnetic domain structure of a magnetic film such as i-Fe exhibits complex behavior in response to an applied magnetic field. This affects the electrical characteristics measured from the terminals. Therefore, it is possible to determine whether the performance of the transducer is good or bad based on the electrical characteristics output from the transducer.

That is, when a magnetic field signal is applied to the transducer, an output is obtained at the terminals of the transducer due to electromagnetic induction of magnetic flux that passes through the magnetic film of the transducer and interlinks with the coil of the transducer. When the magnetic domain structure of the transducer's magnetic film changes discontinuously due to the applied magnetic field, as in the example shown in FIG. By detecting this rapidly changing waveform obtained at the terminal of the transducer, it is possible to determine whether the performance of the transducer is good or bad.

Furthermore, when a current signal is applied to the transducer, a voltage signal output V, which is the product of the impedance Z of the transducer and the current I, is obtained at both terminals of the transducer.

V=ZXI...(1
) Therefore, the output signal will contain a component of the impedance variation of the transducer. By the way, the impedance of the transducer is shown by the following equivalent circuit.

Z=R+jωL (j2=-1)...
(2) Here, R is the real part of the resistance of the coil) and the AC loss of the magnetic film of the transducer, and L is the sum of the inductance of the coil and the inductance of the magnetic film. j is an imaginary unit and j2=1.

ω is the angular frequency. The inductance of a magnetic film is proportional to the average magnetic permeability of the magnetic film, and the magnetic permeability strongly depends on the magnetic domain structure of the magnetic film. Therefore, when the magnetic domain structure of the magnetic film changes discontinuously due to the magnetic field generated by the applied current signal, a suddenly changing waveform is obtained in the output obtained at the terminal. By detecting this rapidly changing waveform obtained at the terminal of the transducer, it is possible to determine whether the performance of the transducer is good or bad.

As is clear from the above description, abnormalities in the magnetic film of the transducer of the thin-film magnetic head can be detected by detecting fluctuations in the voltage signal obtained between the transducer terminals.

〔Example〕

When a defective head exhibiting the reproduction waveform distortion "wiggle" peculiar to thin-film magnetic heads is matched against another normal magnetic head and a vertical wave magnetic field signal is applied from the normal magnetic head, as an example, "wiggle" is detected. A similar protrusion-like waveform distortion was observed. Even when a sine wave was applied instead of a triangular wave to the magnetic field signal, similar waveform distortion was observed, indicating that it did not depend on the waveform of the excitation signal. The waveform distortion thus observed did not depend too strongly on the frequency and amplitude of the excitation signal, and was a high-speed signal of several tens of nanoseconds.

The appearance of this waveform distortion varies each time a current is applied to the thin film magnetic head to set the magnetization state, and the reproducibility is poor. The above waveform distortion was also observed in the voltage signal obtained at the terminal by applying a current signal directly to the head. That is, by applying a current signal of about several MHz to the electrical terminal of the transducer of the thin-film magnetic head, or by directly applying a magnetic field signal to the transducer of the magnetic head, the signal can be obtained at the electrical terminal of the transducer. By observing the voltage signal, it is possible to identify defective transducers that produce the reproduced waveform distortion "wiggle" characteristic of thin-film magnetic heads, without having to levitate the head above a rotating medium. I understand.

Furthermore, in general, if the waveform is distorted from a sine wave, for example by becoming vertically asymmetrical, it will contain many harmonic components in one frequency component, resulting in a defective head that causes "wiggle" as described above. The signal obtained by the transducer contains harmonic signals of the frequency of the original excitation signal, and in response to the fluctuation of "wiggle" from recording to recording, demagnetization or saturation processing is required. The output of this harmonic component changed every time. Therefore,
By repeatedly measuring this harmonic component, we can measure and compare the If of a defective transducer head that exhibits the reproduction waveform distortion "wiggle" peculiar to thin-film magnetic heads using temporally changing reproduction waveforms. It was found that selection can be performed with higher sensitivity.

When a transducer of a thin film magnetic head is completed on a substrate, an electrical connection can be obtained by setting a prober needle on the electrical terminal of the transducer, and harmonics of the terminal voltage obtained by applying a current signal can be obtained. By looking at the fluctuations in the components, it is possible to evaluate and select the heads.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram outlining an embodiment of a transducer inspection method for a thin film magnetic head in a state where a large number of transducers are formed on a substrate.

The output of the first high-frequency signal source 1 is passed through the transducer 4 to be tested by pressing the probe needle 13 against the connection terminal of the transducer on the board.

The mixer circuit 3 mixes the output of the first high frequency signal source 1 and the output of the second high frequency signal source 1.
The outputs of the high frequency signal sources 2 are added to each other so that there is no interference between the sources.

In order to extract the impedance variation of the magnetic transducer 4 to be tested, a bridge circuit 5, which has been widely used in the past to extract such impedance variation, is used. A linear element 6 composed of a resistance and an inductance is inserted into one side of the magnetic head 5 so as to have an impedance equivalent to that of a transducer of a standard thin film magnetic head. The output signal of the bridge is amplified by a high frequency amplifier 7 with less noise. After passing through a filter circuit 8 that extracts a desired frequency component from the amplifier output signal, it is compared with a preset level of a normal transducer, and if it exceeds the set level, a signal indicating a defective head is generated. The signal is output from the comparator 9 and stored in the storage device along with the head identification symbol. Here, instead of the filter circuit 8, a spectrum analyzer that extracts desired frequency components may be used. As shown in FIG. 1, this testing apparatus includes an initialization signal source 10. which generates a signal for setting the magnetization state of the transducer to be tested. a magnetic field application device 11 that applies a magnetic field from an external transducer to the transducer to be inspected;
Additionally, a third signal source 12 that generates a low frequency signal may be included.

Next, the operation of the inspection method will be explained using FIG.

When the impedance of the transducer is Z, the voltage between the transducer terminals is V=ZXI as shown in equation (1). Here, ■ is the voltage between the terminals of the transducer,
is the current flowing through the transducer coil.

By the way, when a current is passed through the coil of a transducer, a magnetic field is obtained that interlinks with the coil, and the magnetic flux accompanying the magnetic field flows through the magnetic film, which allows the magnetic flux to pass through it more easily than in the surrounding space. Due to this magnetic field, the magnetic membrane of the transducer is affected,
Its magnetic domain structure changes. As a result, the magnetic properties of each part of the upper and lower magnetic films, which are connected at the rear end and constitute one magnetic path as a whole, change, and the macroscopic impedance of the entire magnetic path changes accordingly. Here, for example, if the impedance Z of the transducer is a function Z(I) of the current I passed through the transducer, the voltage V between the transducer terminals is expressed as follows: It can be expressed by the electrician's function f(I).

v=zx 工=z(I)xI=f(I)...(3
) Here, when the function Z(I) is expanded into a polynomial of the current I, it can be expressed as the following equation. That is, Z(I)=α
+β engineering+γI2. +δI3+... (4) f(
I) = I (α + β engineering + γ engineering 2 + δ engineering 3 +...) =
czI+I! lIz+YI'+5 I'+・=...(
5) Furthermore, the current flowing through the coil of the transducer is
Assuming that is a sine wave that changes with the angular frequency ω as shown in the following equation, I = Ioe x p (j < L) t)
-(6), and each term of the polynomial is l2=Io"exp(j2ωt). Therefore, the voltage V between the terminals of the transducer includes not only the fundamental frequency ω but also high frequencies such as twice or three times the fundamental frequency ω. The harmonics will be included.At the fundamental frequency ω, most of the output at that frequency is due to a constant, constant portion of the impedance of the transducer, and the impedance due to the application of current On the other hand, for harmonics, it is thought that impedance fluctuations account for a large proportion.

As described above, a defective transducer has more even-order harmonic components than a good transducer, so by measuring the output of these harmonics, the waveform of the terminal voltage of the transducer can be determined. The occurrence of distortion can be detected with higher sensitivity, and a transducer that is a defective head that causes wiggle can be selected.

Furthermore, since the reproduced waveform of the wiggle changes each time it is recorded even if it is recorded under the same conditions, it is considered that the magnetic domain structure of the transducer changes each time it is demagnetized. Using an initialization signal source 10 that sets the magnetization state of the transducer 4 to be tested shown in FIG. 1, a relatively large current is applied to saturate the transducer 4 to be tested, or alternatively When the output of the high-order harmonics was repeatedly measured by alternating current demagnetization in which the amplitude was gradually reduced while reversing the polarity, the output of the defective transducer changed significantly. As a second example, it has been found that by measuring the above-mentioned harmonics while repeating the initial settings of the nuclear transducer and comparing the fluctuations, it is possible to sort out whether the transducer is good or bad.

By the way, it is generally difficult for a signal source to generate a signal with only a single frequency, and it contains some harmonics. For this reason, even in the case of second-order and third-order harmonics, there is an output corresponding to a portion where the impedance of the transducer does not change, and the sensitivity of detecting components due to impedance changes decreases. As a third embodiment, in order to extract the nonlinear output more efficiently, the frequency of the voltage signal obtained by applying signal currents of two different frequencies in a superimposed manner using the nonlinearity of the impedance of the transducer. We found a method to observe the component that is the sum of two frequencies.

That is, if the angular frequency of the first high-frequency signal source 1 shown in FIG. 1 is ωl, and the angular frequency of the second high-frequency signal source 2 is ω2, then I=Izexp(jωxt)+Izexp(jωzt)
For example, in the square term of equation (7), I”=(It
s xp(j ωtt)+Izexp(j ωzt))
”=It”exp(j2c,+tt)+Iz”exp(
j2ω2t)+2ItIzexp(j(ω1+ω2)t
), and the component of the sum of the two frequencies is obtained. Similarly, for higher-order terms, the sum or difference frequency component of frequencies that are integral multiples of the frequency of the original signal can be obtained. This frequency component is not included in the drive signal and is only generated by the nonlinearity of the impedance of the transducer. In FIG. 2(a), 2
Figure 2(b) shows an outline of the voltage signal obtained by superimposing and applying signal currents of two different frequencies, and the appearance of frequency components when this signal is frequency-resolved using a spectrum analyzer. FIG. 3 shows the results of repeatedly measuring this frequency component while changing the magnetization state as shown above.

As shown in Figure 3(a), a transducer with a non-defective head that does not cause wiggle has a diameter of 4.005M.
The output in Hz hardly changed even after repeated measurements. On the other hand, in a transducer that becomes a defective head where wiggle occurs, as shown in FIG.
The output at 0.05 MHz varied dramatically with repeated measurements. Note that FIG. 3 shows the variation in the spectrum analyzer output.

Note that the difference frequency component signal, for example, 4 in FIG.
, 995MHz, similar results were obtained.

Further, one of the two signal sources can be replaced by a high frequency magnetic field signal applied to the transducer 4 to be tested by an external magnetic field application bag @11 shown in FIG.

As described above, among the frequency components of the voltage signal obtained by superimposing and applying current signals or magnetic field signals of two different frequencies, the sum or difference component of integral multiples of the two frequencies is demagnetized. Alternatively, by repeating the observation after each saturation process and observing the fluctuations, it is possible to identify a defective transducer that produces the reproduction waveform distortion "wiggle" peculiar to thin-film magnetic heads. Highly sensitive selection can be performed using the nonlinear characteristics of impedance.

The fourth embodiment superimposes the output of the low-frequency third signal source 12 shown in FIG. By gradually changing the magnitude of the current bias and observing the component of the sum of the two original signal frequencies after each demagnetization or saturation process, we can demonstrate the reproduction fatigue distortion (wiggle) peculiar to thin-film magnetic heads. This is a method for quickly selecting transducers that are defective heads in a wide magnetic field range where wiggles may occur. Fig. 4 shows a third signal source according to this embodiment. 12 output and the change in the output of the frequency component of the sum of the original two signal frequencies obtained at that time.In the case of a defective transducer head, this output fluctuation occurs as shown in Figure 4(a). The variation was remarkable, and the variation was small in the transducer with a good head, as shown in Figure 4(b).Therefore, by observing the variation of this sideband wave with respect to the DC bias, it is possible to select defective transducers. can.

However, the shape of this waveform also changes depending on the setting of the initial magnetization state of the transducer, and it was observed that the maximum value of this output is large for the transducer that produces a head with a severe degree of wiggle. . Therefore, when we examined the distribution of maximum value occurrence when measurements were repeated many times, we found that it follows an extreme value distribution, as shown in FIG. Although this method can be applied to completed heads, many transducers have been completed on the board, and AC demagnetization is performed among the various initial settings on the transducers whose magnetic pole tips are still closed. In this case, as shown in FIG. 6, the distribution of the above-mentioned maximum values is best separated, and it has been found that it is easy to sort out non-defective products and defective products. Note that FIG. 6 shows the test results for six transducers.

That is, in the fifth embodiment, the maximum value of the fluctuation with respect to the DC bias of the high-order harmonic sideband obtained by superimposing current signals of two different frequencies to the transducer is expressed as:
This is a method to highly accurately select defective transducers at the stage of formation on a substrate by repeatedly measuring AC demagnetization and comparing the generation distribution.

In other embodiments, instead of the alternating current magnetic field used in the above embodiments, a magnetic field rotating at a frequency of ω/2π is externally applied and observed, thereby directly driving defective magnetic domains and achieving high sensitivity.
In addition, by simultaneously exciting a large number of transducers, it is possible to select defective transducers that exhibit the reproduced waveform distortion "wiggle" peculiar to thin-film magnetic heads.

〔Effect of the invention〕

According to the present invention, a transducer formed on a substrate is inspected in the thin-film magnetic head manufacturing process without actually recording or reproducing the thin-film magnetic head by floating it above a rotating magnetic disk. can do. Defective products can be removed when the added value of the thin film magnetic head is relatively small.

[Brief explanation of the drawing]

FIG. 1 is a block diagram outlining an embodiment of a method for testing a transducer of a thin-film magnetic head according to the present invention. FIG. 2(a) is a waveform diagram showing an outline of a voltage signal obtained by applying signal currents of two different frequencies in a superimposed manner. Second
FIG. 2(b) is a waveform diagram showing the appearance of frequency components when the signal in FIG. 2(a) is frequency-decomposed using a spectrum analyzer. Figures 3(a) and (b) are similar to Figure 2(b).
) is a graph showing the results of repeated measurements of the frequency component of the sum of two different frequencies while changing the magnetization state of the transducer, where (,) is an example of a good product, and (b) is an example of a defective product. . FIGS. 4(a) and 4(b) show the output of the third signal source 12 when a low-frequency third signal is superimposed on the current signals of two different frequencies, and the output of the two high-frequency signals. It shows the change in the frequency output of the sum of frequencies, and (a
) is an example of a defective product, and (b) is an example of a non-defective product. Figure 5 shows
Maximum variation of sideband waves relative to DC bias. Graphs 6 (a) and (b) illustrating that the generation distribution follows the extreme value distribution when AC demagnetization is repeated and measured.
) is a graph showing the distribution of the maximum variation of sideband waves with respect to DC bias when AC demagnetization is repeated. (a) is an example of a good product, (b) is an example of a defective product. be. DESCRIPTION OF SYMBOLS 1... First high frequency signal source, 2... Second high frequency signal source, 4... Transducer to be tested, 5... Bridge circuit, 6... Standard thin film magnetic head. Linear element equivalent to the impedance of the transducer, 7...
- High frequency amplifier, 9... Comparator, 10... Generates a signal for setting the magnetization state of the transducer to be tested.
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Claims (1)

[Claims] 1. A method for inspecting the performance of a transducer for a thin film magnetic head based on electromagnetic characteristics, in which at least one of a current signal and a magnetic field signal is applied to the transducer, and based on the resulting voltage signal, A method for inspecting a transducer for a thin film magnetic head, characterized by determining whether it is good or bad. 2. A method of testing the performance of a transducer for a thin film magnetic head based on electromagnetic characteristics, in which a plurality of transducers are formed on a substrate by thin film fabrication technology, and each transducer is sequentially exposed to a current signal and a magnetic field. A method for testing a transducer for a thin-film magnetic head, comprising applying at least one of the signals and determining the quality of each transducer based on the voltage signal obtained as a result. 3. A method of inspecting the performance of a transducer for a thin film magnetic head based on electromagnetic characteristics, in which a plurality of transducers formed on a substrate by thin film fabrication technology are separated into individual transducers, and each transducer is 1. A method for testing a transducer of a thin-film magnetic head, comprising applying at least one of a current signal and a magnetic field signal, and determining pass/fail based on a voltage signal obtained as a result. 4. A method for inspecting a transducer for a thin-film magnetic head according to claim 1, characterized in that a product in which there is a sudden change in the voltage signal is determined to be a defective product. 5. A method for testing a transducer for a thin-film magnetic head according to claim 1, characterized in that the voltage signal is compared with a normal voltage signal to select defective products. 6. In claim 1, the voltage signal is displayed as a graph of the relationship between voltage and time, and a product in which there is a portion where the voltage suddenly changes is determined to be a defective product. Characteristic testing method for transducers for thin-film magnetic heads. 7. In a method of inspecting the quality of performance of a transducer for a thin film magnetic head based on electromagnetic characteristics, a voltage signal obtained by applying at least one of a current signal and a magnetic field signal to the transducer is frequency-resolved to vary the harmonic component. 1. A method for inspecting a transducer for a thin-film magnetic head, the method comprising determining pass/fail by detecting. 8. In a method of testing the performance of a transducer for a thin film magnetic head by electromagnetic characteristics, two or more different current signal components are applied to the transducer with a magnetic field signal superimposed, and the resulting voltage signal is frequency-resolved. 1. A method for testing a transducer for a thin-film magnetic head, characterized in that pass/fail is determined based on fluctuations in sideband waves adjacent to harmonics of one of the applied signals. 9. A device for inspecting the performance of a transducer of a thin film magnetic head that is finally processed into a slider shape or a transducer at a stage before being processed into a slider shape, the device providing an alternating current constant current signal to the transducer. 1. A testing device for a transducer for a thin-film magnetic head, comprising a signal power supply for applying a signal and means for measuring a connection terminal voltage of the transducer. 10. An apparatus for inspecting the performance of a transducer of a thin film magnetic head that is finally processed into a slider shape or a transducer at a stage before being processed into a slider shape, and for applying a magnetic field signal to the transducer. 1. An inspection device for a transducer for a thin-film magnetic head, characterized in that it is equipped with excitation means for excitation, and means for measuring connection terminal voltage of the transducer. 11. A device for inspecting the performance of a transducer of a thin film magnetic head that is finally processed into a slider shape or a transducer at a stage before being processed into a slider shape, the device including an alternating current constant current signal and an alternating current constant current signal to the transducer. Inspection of a transducer for a thin film magnetic head, characterized by comprising means for applying at least one of a magnetic field signal, means for outputting a connecting terminal voltage of the transducer, and means for amplifying the connecting terminal voltage and outputting a harmonic component. Device. 12. A method for manufacturing a thin film magnetic head, which includes a step of electromagnetically inspecting the performance of a transducer for a thin film magnetic head, the method comprising applying at least one of a current signal and a magnetic field signal to the transducer before it is processed into a slider shape. A method for manufacturing a thin-film magnetic head, characterized in that defective products are selected based on a voltage signal obtained by application, and only normal products are finally processed into a slider shape. 13. A method for manufacturing a thin-film magnetic head, which includes a step of electromagnetically inspecting the performance of a transducer for a thin-film magnetic head, wherein a current signal is individually sent to a plurality of transducers formed on a substrate by thin-film manufacturing technology. A thin film magnetic head characterized in that defective transducers are selected based on a voltage signal obtained by applying at least one of a magnetic field signal and a magnetic field signal, and after cutting a substrate into each transducer, only normal products are processed into a final product. Production method. 14. The method of manufacturing a thin film magnetic head according to claim 13, wherein the performance of the transducer is inspected after cutting the substrate into individual transducers. 15. The method of manufacturing a thin film magnetic head according to claim 13, characterized in that an address is assigned to each of the plurality of transducers on the substrate, and inspection results are recorded for each address. 16. A method for manufacturing a thin film magnetic head, which includes a step of electromagnetically inspecting the performance of a transducer for a thin film magnetic head, the step of manufacturing a plurality of transducers on a substrate by a thin film manufacturing technique; applying at least one of a current signal and a magnetic field signal to each of the transducers individually, and selecting defective products based on the resulting voltage signal; cutting the substrate into individual transducers; A thin-film magnetic head manufacturing system characterized by having a process of finishing a normal product into a slider shape. 17. The method of manufacturing a thin film magnetic head according to claim 16, further comprising the step of cutting the substrate into individual transducers before the step of selecting defective transducers. 18. The method of inspecting a transducer in a thin film magnetic head manufacturing process according to claim 1, characterized in that an alternating current constant current signal is applied to the transducer. 19. A method for inspecting a transducer in a thin film magnetic head manufacturing process according to claim 1, characterized in that an alternating current constant current signal and a magnetic field signal are applied to the transducer in a superimposed manner. 20. A method of inspecting the quality of the performance of a transducer formed on a substrate during a stage in the manufacturing process of a thin film magnetic head, which voltage is obtained by applying two or more current signals with different frequencies to the transducer. A transducer inspection method in a thin film magnetic head manufacturing process, characterized in that inspection is performed based on fluctuations in the output of harmonic components of a signal. 21. A method for inspecting the quality of the performance of a transducer formed on a substrate during a stage in the manufacturing process of a thin film magnetic head, the voltage being obtained by applying two or more magnetic field signals with different frequencies to the transducer. A transducer inspection method in a thin film magnetic head manufacturing process, characterized in that inspection is performed based on fluctuations in the output of harmonic components of a signal. 22. A method for inspecting the performance of a transducer formed on a substrate at an intermediate stage in the manufacturing process of a thin film magnetic head, which involves applying a current signal and a magnetic field signal in a superimposed manner to the transducer, and applying one of them to the transducer. A thin film characterized in that a total of three or more signals are applied, with at least one signal having two or more different frequencies, and the test is performed based on fluctuations in the output of harmonic components of the voltage signal obtained thereby. A transducer inspection method in the magnetic head manufacturing process. 23. In claim 20, among harmonic components of a voltage signal obtained by applying two or more current signals with different frequencies to the transducer, the sum of frequencies that are integral multiples of the original frequency, or A method for inspecting transducers in a thin film magnetic head manufacturing process, characterized by detecting variations in frequency components of differences and selecting defective transducers. 24. In claim 21, among the harmonic components of the voltage signal obtained by applying two or more magnetic field signals with different frequencies to the transducer, the sum of frequencies that are integral multiples of the original frequency, or A method for inspecting transducers in a thin film magnetic head manufacturing process, characterized by detecting variations in frequency components of differences and selecting defective transducers. 25. Claim 22, wherein among the harmonic components of a voltage signal obtained by applying a superimposed current signal and a magnetic field signal to the transducer, the sum or difference of frequencies that are integral multiples of the original frequency. A method for inspecting transducers in a thin film magnetic head manufacturing process, the method comprising detecting fluctuations in the frequency components of a transducer and selecting defective transducers. 26. A method for inspecting a transducer of a thin-film magnetic head according to claim 1, characterized in that a rotating magnetic field is applied to the transducer. 27. Two or more high-frequency signal sources for conducting current to the transducer to be tested on the substrate, means for adding the outputs of the two or more high-frequency signal sources so as not to interfere with each other, and a method for adjusting the impedance of the transducer to be tested. A bridge circuit for extracting fluctuations, means for amplifying the output signal of the bridge, means for extracting a desired frequency component from the amplified output signal, and comparing the frequency component with a set level indicating a normal transducer frequency component. 1. A testing device for a transducer for a thin film magnetic head, comprising means for outputting a defective signal. 28. The apparatus for testing a transducer for a thin film magnetic head according to claim 27, further comprising an initialization signal source for initializing the magnetization state of the transducer to be tested.