JP2007310970A - Rework method of magnetic head assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rework method of a magnetic head assembly a suspension can be used again with simple work and facility by eliminating burrs becoming hindrance for mounting a slider. <P>SOLUTION: This is the method in which the magnetic head assembly in which the electrode pad of the magnetic head slider and the electrode pad of the suspension are solder-joined in position relation in which they are orthogonal each other, the defective slider is exchanged to a new slider, the method has a process for forming flatted solder on the electrode pad of the suspension by heating solder joining the electrode pad of the defective slider and the electrode pad of the suspension by a hot wind leaving the defective slider on the suspension, a process for eliminating the defective slider from the suspension, a process for mounting the new slider on the suspension, and a process for joining the electrode pad of the new slider and the electrode pad of the suspension utilizing again the flatted solder. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rework method of a magnetic head assembly in which an electrode pad of a magnetic head slider and an electrode pad of a suspension are solder-bonded in a positional relationship orthogonal to each other.

  A magnetic head assembly used in a hard disk drive (HDD) includes a magnetic head slider in which a magnetic head is incorporated, and a suspension to which the magnetic head slider is bonded and fixed. The suspension has a flexure that elastically supports the magnetic head slider, and a flexible wiring board for electrically connecting the magnetic head and an external circuit is bonded to the surface of the flexure. The electrode pad of the magnetic head slider and the electrode pad of the suspension (flexible wiring board) can be formed with a sphere diameter smaller than that of the gold ball so that the bonding area (the size of the electrode pads and the electrode pad spacing) can be reduced. They are joined by solder ball bonding using solder balls.

This type of magnetic head assembly is subjected to dynamic characteristic inspection before shipment. In dynamic characteristic inspection, a magnetic head slider is mounted (adhered) on a suspension and mounted on a spin stand or the like, and an electric characteristic is inspected while a hard disk is actually rotated. This is a final characteristic inspection for determining the quality of the head slider. In this dynamic characteristic inspection, if the dynamic characteristic as the inspection result satisfies the standard, the magnetic head slider is judged as a non-defective product, and the magnetic head assembly becomes a product. On the other hand, if the dynamic characteristics do not satisfy the standard, the magnetic head slider is determined as a defective slider and removed from the suspension, and the suspension after removing the slider is reused. Conventionally, when removing a defective slider from a suspension, solder bonding between the electrode pad of the defective slider and the electrode pad of the suspension is released and the bonding strength between the defective slider and the suspension is weakened, and then the defective slider is forcibly removed. .
JP 2002-367132 A (Patent No. 3634773)

  However, if the defective slider is removed from the suspension by the conventional method, the solder that has joined the electrode pad of the defective slider and the electrode pad of the suspension remains on the electrode pad of the suspension, causing burrs. If this burr is located on the slider mounting surface side of the suspension, when the new slider that replaces the defective slider is mounted, the electrode pad of the new slider and the burr abut and the new slider can be installed in the correct posture. difficult. In this case, the suspension cannot be reused. In order to eliminate burrs on the electrode pads of the suspension, it is sufficient to completely suck out the melted solder when releasing the solder joint with the electrode pads of the defective slider. Necessary and contrary to the desire to reuse the suspension with simple rework operations and equipment.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a magnetic head reworking method that can eliminate the detrimental solder burrs and reuse the suspension with simple work and equipment.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to obtain a rework method of a magnetic head assembly that can eliminate a burr that hinders slider mounting and can reuse a suspension with simple work and equipment. .

  The present invention focuses on flattening the solder that has joined the electrode pad of the defective slider and the electrode pad of the suspension so that it can be reused for reworking so as not to hinder reworking. In particular, in order to protect the slider mounting surface of the suspension from the molten solder scattered during the planarization, it is proposed that the solder planarization is optimal with the defective slider remaining.

  That is, according to the present invention, in the magnetic head assembly in which the electrode pad of the magnetic head slider and the electrode pad of the suspension are solder-bonded in a positional relationship orthogonal to each other, when the magnetic head slider is a defective slider, the defective slider is used as the slider. In this method, the solder that joins the electrode pad of the defective slider and the electrode pad of the suspension is heated with hot air while the defective slider remains on the suspension, and is flattened on the electrode pad of the suspension. A step of forming solder, a step of removing the defective slider from the suspension, a step of mounting a new slider in place of the defective slider on the suspension, and reusing the planarized solder to recycle the electrode pad of the new slider and the electrode pad of the suspension Having a step of bonding It is a symptom.

  When forming the flattened solder, it is preferable that the surface of the suspension opposite to the slider mounting surface is heated at the same time as the hot air at a temperature lower than the hot air temperature.

  Some have an opening between the slider mounting surface of the suspension and the electrode pad of the suspension. In this case, it is preferable to flatten the solder on the electrode pad of the suspension by applying hot air from above the electrode pad of the suspension toward the opening side. The solder flattened on the electrode pad of the suspension by the wind pressure of hot air is easily flattened by part of the solder escaping to the opening.

  It is practical to join the electrode pad of the new slider and the electrode pad of the suspension by supplying a solder ball between the electrode pad of the new slider and the flattening solder and melting the solder ball. The presence of the flattened solder improves the solder wettability and facilitates the solder bonding between the electrode pad of the new slider and the electrode pad of the suspension.

  According to the method of the present invention, the solder bonded to the electrode pad of the defective slider and the electrode pad of the suspension is flattened on the electrode pad of the suspension. Suspension can be reused for work and equipment.

  FIG. 1 is a plan view showing the overall structure of a magnetic head assembly (completed state) for a hard disk drive, to which the present invention is applied. The magnetic head assembly 1 includes a magnetic head slider 11 in which a magnetic head 12 is incorporated, and a suspension 21 to which the magnetic head slider 11 is bonded and fixed. The suspension 21 has a load beam 21a and a flexure 21b attached to the tip of the load beam 21a in a state where the magnetic head slider 11 is elastically supported in a floating manner with respect to the load beam 21a. The flexure 21b is a leaf spring-like flexible thin metal plate for electrically connecting the magnetic head 12 and an external circuit (a circuit system of a hard disk device on which the magnetic head assembly 1 is mounted) on the flexure surface. The flexible wiring board 21c is attached with an adhesive. As shown in FIG. 2, the magnetic head slider 11 has a back surface 11 c bonded and fixed to the slider mounting surface 22 of the suspension 21 with a thermosetting adhesive, and a plurality of electrode pads 13 exposed on the trailing surface are formed in the suspension 21. Are respectively bonded to the corresponding electrode pads 23. FIG. 2 is a cross-sectional view showing a solder joint between the electrode pad 13 of the magnetic head slider 11 and the electrode pad 23 of the suspension 21. Openings 24 are formed between the slider mounting surface 22 of the suspension 21 and the plurality of electrode pads 23, and the plurality of electrode pads 23 are arranged in a row facing the openings 24. Reference numeral 40 in FIG. 2 denotes solder (solder fillet) that joins the electrode pad 13 of the magnetic head slider 11 and the electrode pad 23 of the suspension 21. The electrode pad 13 of the magnetic head slider 11 and the electrode pad 23 of the suspension 21 according to this embodiment are made of Au.

  The magnetic head assembly 1 having the above configuration is a product if it is determined to be a non-defective product in a dynamic characteristic inspection performed in a state where the hard disk is actually rotated. A head slider (hereinafter referred to as a defective slider) 11 ′ is removed from the suspension 21, and a rework operation for reusing the suspension 21 is performed.

  An embodiment of a rework method according to the present invention will be described with reference to FIGS. 3, FIG. 5, FIG. 6 and FIG. 8 are cross-sectional views showing the steps of the rework method according to the present invention, and FIG. 4 is a cross-sectional view showing the flattened solder formed by the steps of FIG. FIG. 3 is a schematic plan view showing a suspension 21 after removing a slider.

  If the magnetic head slider 11 is determined to be a defective slider 11 ′ in the dynamic characteristic inspection described above, first, the defective slider 11 ′ is left on the slider mounting surface 22 of the suspension 21 as shown in FIG. The solder 40 that joins the electrode pad 13 of the magnetic head slider 11 and the electrode pad 23 of the suspension 21 is heated by hot air while the suspension 21 is heated by the heater 31 from the back surface 22 ′ opposite to the slider mounting surface 22. Heat. The reason why the suspension 21 is heated by the heater 31 at the same time as the heating by the hot air is to reduce the surface tension of the solder and improve the wettability of the solder. The heating temperature by the heater 31 is set to be equal to or higher than the melting point of the solder 40, specifically about 250 ° C., for example.

  Hot air is blown from above the electrode pad 23 of the suspension 21 toward the opening 24 (from the upper right to the lower left in the figure). Specifically, in this embodiment, a hot air gun 32 is used as a hot air supply source, and the jet port of the hot air gun 32 is installed at an angle θ (θ = about 45 °) with respect to the surface of the electrode pad 23 of the suspension 21. The hot air of about 250 ° C. is blown at a flow rate of 3 L / min. Upon receiving this hot air, the solder 40 is melted, and the bonding between the electrode pad 13 of the defective slider 11 ′ and the electrode pad 23 of the suspension 21 is released. A part of the melted solder 40 is scattered to the slider mounting surface 22 side of the suspension 21 by the wind pressure of hot air, and the other part is pressed against the surface of the electrode pad 23 of the suspension 21 by the wind pressure of hot air. The electrode pad 23 is flattened. Here, the planarization means a process of making a macroscopic unevenness and a process of making the solder 40 to a thickness of less than 10 μm.

  The solder 40 scattered to the slider mounting surface 22 side adheres to the defective slider 11 ′ on the slider mounting surface 22 and does not adhere to the slider mounting surface 22. The defective slider 11 ′ is used as a protective member that protects the slider mounting surface 22 from molten solder scattered by hot air. On the other hand, the solder flattened on the SUS electrode pad 23 becomes the flattened solder 41 shown in FIG. The planarizing solder 41 becomes a solder contact surface of each electrode pad 23 of the suspension 21 and is reused when the electrode pad of the new slider and the electrode pad 23 of the suspension 21 are joined. The thickness of the planarizing solder 41 is about 0.5 μm.

  When the solder 40 is flattened on the electrode pad 23 of the suspension 21 as described above, the molten solder on the electrode pad 23 of the suspension 21 may be pushed out to the slider mounting surface 22 side by hot air. The solder pushed to the slider mounting surface 22 side becomes burrs, but the defective slider 11 ′ on the slider mounting surface 22 functions as a mechanical stopper to stop the burrs, and even in the worst case, the burrs contact the defective slider 11 ′. It only occurs to the position. The burr is not shown in detail, but is released to the opening 24 of the suspension 21 and faces downward. Therefore, when the new slider is mounted, the solder burrs do not come into contact with the new slider and its electrode pads, and the mounting of the new slider is not hindered.

  Next, as shown in FIG. 5, the suspension 21 is heated by the heater 31 from the back surface 22 'side opposite to the slider mounting surface 22, and the defective slider 11' is removed. The heating temperature by the heater 31 is about 100 ° C. In a state where the bonding strength between the defective slider 11 ′ and the suspension 21 (the bonding strength of the thermosetting adhesive bonding the defective slider 11 ′ and the suspension 21) is weakened by this heating, for example, both side surfaces 11d of the defective slider 11 ′. When lifted with “sandwiched between”, the defective slider 11 ′ is easily peeled off from the suspension 21. At this time, the solder attached to the defective slider 11 'in the previous process (solder flattening process) is also removed together with the defective slider 11'. The removed defective slider 11 'is discarded. The thermosetting adhesive 51 that has bonded the defective slider 11 ′ and the suspension 21 remains on the slider mounting surface 22 after the defective slider 11 ′ is removed.

  Subsequently, as shown in FIG. 6, the thermosetting adhesive 51 remaining on the slider mounting surface 22 is left in a state where the suspension 21 is heated by the heater 31 from the back surface 22 ′ side opposite to the slider mounting surface 22. It removes with the adhesive removal tool 52. FIG. The thermosetting adhesive 51 of this embodiment is a resin, and the adhesive removal tool 52 is made of a Ultem resin rod, a PEEK resin, or a polyimide resin.

  Through the steps so far, the slider mounting surface 22 that is equivalent to the new state is exposed, and the suspension 21 having the planarizing solder 41 on the electrode pads 23 is obtained as shown in FIG. The suspension 21 is reused as a rework product. That is, as shown in FIG. 8, a new magnetic head slider (new slider) 11 is bonded and fixed to the slider mounting surface 22 of the suspension 21 with, for example, a thermosetting adhesive, and further, the electrode pad 13 of the new slider 11 and Solder balls 42 are supplied between the planarizing solder 41 of the suspension 21. Here, since the flattened solder 41 is flattened so as not to have macroscopic unevenness, the solder ball 42 can be easily supplied and adjusted in position. Then, by completely melting the solder ball 42, the electrode pad 13 of the new slider 11 and the electrode pad 23 of the suspension 21 are joined, and the magnetic head assembly 1 is obtained.

  Table 1 shows the results of measuring the surface roughness Ra1 (nm) of the planarizing solder 41 and the surface roughness Ra2 (nm) of the Au electrode pad by AFM (Atomic Force Microscope). The surface roughness measurement by this AFM was performed at an arbitrary 20 points in a minute area (10 μm × 10 μm) corresponding to the area where the solder ball 42 is in point contact with the solder contact surface of the electrode pad 23 of the suspension 21. The electrode pad 13 of the magnetic head slider 11 and the electrode pad 23 of the suspension 21 of this embodiment are Au electrode pads. The surface roughness of the electrode pad 23 in the suspension 21 when new (before assembly) is shown in Table 1. It is equivalent to the surface roughness Ra2 of the pad.

(Table 1)
Surface roughness Ra1 Ra2
Minimum value 35.12 60.81
Maximum value 108.59 104.52
Average value 94.04 86.308
Range 73.47 43.71

  From the measurement results shown in Table 1, it can be seen that the surface roughness Ra1 (average value) in the minute area of the planarizing solder 41 is equivalent to the surface roughness Ra2 (average value) of the Au electrode pad. That is, it can be understood that the surface roughness of the solder contact surface (solder ball supply surface) of the SUS electrode pad 23 does not substantially change between a new product (before assembly) and a reuse product (after rework). Since the surface roughness is the same, it is considered that the heat transfer method on the solder contact surface of the electrode pad 23 of the suspension 21 is also equivalent. Therefore, even in the case of the suspension 21 of the rework product (the planarizing solder 41 is formed on the electrode pad 23), the electrode pad 23 of the suspension 21 and the electrode pad of the magnetic head slider 11 are the same as the new suspension 21. 13 can be soldered satisfactorily.

  As described above, in this embodiment, the solder 40 that has joined the electrode pad 13 of the defective slider 11 ′ and the electrode pad 23 of the suspension 21 while the defective slider 11 ′ remains on the suspension 21 is used as the electrode of the suspension 21. Since flattening is performed on the pad 23, no burrs are formed on the electrode pads 23 of the suspension 21, and solder burrs formed by the solder on the electrode pads 23 of the suspension 21 being pushed toward the slider mounting surface 22 are defective sliders. It stops at the position of 11 '. That is, there is no burr that hinders the mounting of the new slider 11. As a result, the new slider 11 can be mounted on the suspension 21 in a correct posture, and the electrode pad 13 of the new slider 11 and the electrode pad 23 of the suspension 21 can be soldered well. Further, by leaving the defective slider 11 'when the solder 40 is flattened, the defective slider 11' protects the slider mounting surface 22 from the molten solder scattered by hot air. Therefore, it is not necessary to remove the solder 40 by sucking work, and expensive equipment is not necessary. Furthermore, in this embodiment, the flattened solder 41 formed by flattening the solder 40 on the electrode pad 23 of the suspension 21 is reused when the electrode pad 13 of the new slider 11 and the electrode pad 23 of the suspension 21 are joined. As a result, the solder wettability is improved and the electrode pads 13 and 23 are easily soldered together. Thereby, the suspension 21 can be effectively reused, and the yield can be improved.

  In this embodiment, the opening 24 of the suspension 21 is used, and the solder pushed out from the SUS electrode pad 23 to the slider mounting surface 22 side is released into the opening 24 to form a downward solder burr. As described above, since the burr only occurs up to the position of the defective slider 11 ′, the present invention can also be applied to a suspension that does not have an opening between the slider mounting surface and the electrode pad.

It is a top view which shows the whole structure of the magnetic head assembly (completed state) for hard disk drives used as the application object of this invention method. FIG. 2 is a cross-sectional view showing a solder joint between an electrode pad of the magnetic head slider of FIG. 1 and an electrode pad of a suspension. It is sectional drawing which shows 1 process of the rework method by this invention. It is sectional drawing which shows the planarization solder formed by the process shown in FIG. It is sectional drawing which shows the next process of the process shown in FIG. It is sectional drawing which shows the next process of the process shown in FIG. FIG. 7 is a schematic plan view showing the suspension after the step shown in FIG. 6. It is sectional drawing explaining the next process of the process shown in FIG.

Explanation of symbols

1 Magnetic head assembly 11 Magnetic head slider (new slider)
11 'defective slider 12 magnetic head 13 electrode pad 21 suspension 22 slider mounting surface 23 electrode pad 24 opening 31 heater 32 hot air gun 40 solder 41 flattening solder 51 thermosetting adhesive 52 tool

Claims (4)

In a magnetic head assembly in which an electrode pad of a magnetic head slider and an electrode pad of a suspension are solder-bonded in a mutually perpendicular positional relationship, when the magnetic head slider is a defective slider, the defective slider is replaced with a slider. ,
With the defective slider remaining on the suspension, the solder joining the electrode pad of the defective slider and the electrode pad of the suspension is heated with hot air to form flattened solder on the electrode pad of the suspension Process,
Removing the defective slider from the suspension;
Mounting a new slider in place of the defective slider on the suspension;
Reusing the planarized solder to join the electrode pad of the new slider and the electrode pad of the suspension;
A method of reworking a magnetic head assembly, comprising: 2. The reworking method of a magnetic head assembly according to claim 1, wherein when forming the flattened solder, a surface of the suspension opposite to the slider mounting surface at a temperature lower than the hot air temperature simultaneously with the heating by the hot air. Rework method for heating magnetic head assembly. 3. A rework method for a magnetic head assembly according to claim 1, wherein an opening is provided between the slider mounting surface of the suspension and the electrode pad of the suspension, and the electrode of the suspension is directed toward the opening. A method of reworking a magnetic head assembly in which the solder is flattened on the electrode pad of the suspension by applying hot air from above the pad. 4. The magnetic head assembly rework method according to claim 1, wherein a solder ball is supplied between the electrode pad of the new slider and the flattened solder, and the solder ball is melted to provide the magnetic head assembly rework method. A rework method of a magnetic head assembly in which an electrode pad of a new slider and an electrode pad of the suspension are joined.

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