Patent Publication Number: US-2007097549-A1

Title: MAGNETIC HEAD ASSEMBLY HAVING AuSn DISPERSION LAYER AND METHOD OF SOLDER BONDING

Description:
This patent document claims the benefit of Japanese Patent Application No. 2005-318708 filed on Nov. 1, 2005, which is hereby incorporated by reference.  
     BACKGROUND  
      1. Field  
      The present embodiments relate to a magnetic head assembly having AuSn dispersion layer and method of solder bonding.  
      2. Related Art  
      Generally, a magnetic head assembly, which is used in a hard disc drive (HDD), includes a slider that has a magnetoresistive element installed therein, a flexure that is formed of a thin flexible sheet metal so as to elastically support the slider, and a flexible printed circuit that is attached to the surface of the flexure and electrically connects the magnetoresistive element of the slider and a circuit system of a device on which the magnetic head assembly is mounted. The flexure is fixed to a load beam by, for example, spot welding. In general, in this type of magnetic head assembly, electrode pads for the magnetoresistive element of the slider and electrode pads of the flexible printed circuit are bonded to each other by a gold ball bonding method according to orthogonal positional relationships between the electrode pads. Recently, in order to cope with reduction in a bonding area (sizes of the electrode pads and intervals between the electrode pads), a solder ball bonding method using a solder ball, which has a smaller spherical diameter than the gold ball, has been proposed (for example, see JP-A-2004-283911 (US 2004228036A1)).  
      The solder ball bonding method can be performed by using, for example, a mounter of an SJB method that sprays a molten solder ball on a joint surface. As the molten solder supplied from the mounter onto the joint surface is solidified, the electrode pads of the slider and the electrode pads of the flexible printed circuit are bonded to each other. A surface protective layer, which is made of Au, is formed on the surfaces (joint surfaces) between the electrode pads of the slider and the flexible printed circuit so as to increase solder wettability.  
      As described above, when the solder ball in a melted state is supplied, the solder ball rapidly cools as soon as the solder ball is supplied to the joint surface, and Au is solidified before being sufficiently diffused into the solder. For this reason, an Au—Sn compound layer is formed at the boundary between the solidified solder and the electrode pads, and peeling of solder junctions is generated due to the Au—Sn compound layer. In addition, posture of the slider (pitch angle) greatly changes after the solder bonding because of shrinkage distortion that is generated when the solder ball is solidified. This change in posture reduces (worsens) a floating characteristic of the magnetic head slider, for example, an output characteristic.  
     SUMMARY  
      The present embodiments may obviate one or more of the limitations of the related art. For example, in one embodiment, a magnetic head assembly and a solder bonding method thereof are capable of increasing bond reliability and preventing a change in posture of a slider.  
      The present embodiments have been finalized in view of the fact that under the recognition that an Au—Sn compound layer formed along the boundary between solidified solder and electrode pads causes peeling, the Au—Sn compound layer formed on the solder joint surface of the electrode pads can be dispersed into the molten solder by supplying a solder ball in a melted state to the joint surface and applying sufficient heat energy to the joint surface, and bending of a slider can be reduced by relieving shrinkage distortion of the solidified solder.  
      In one embodiment, a magnetic head assembly has electrode pads of a slider that have a magnetoresistive element installed therein. Electrode pads of a flexible printed circuit connect the magnetoresistive element to an external circuit and are bonded by solder. An Au layer is formed on solder contact surfaces of the electrode pads of the slider and the flexible printed circuit. An AuSn dispersion layer where Au atoms of the Au layer are dispersed is formed at least on the boundary between the solder contact surfaces of the electrode pads and the solder.  
      In one embodiment, the AuSn dispersion layer is equal to or greater than 50 μm in thickness. Since an adhesive layer (a NiSn or CuSn compound) is formed between the electrode pads and the solder, it is possible to increase solder bond strength.  
      In one embodiment, the AuSn dispersion layer has a higher Au atomic content toward the electrode pads from the solder.  
      An Sn compound layer made of materials of the electrode pads and Sn may be interposed between the electrode pads and the AuSn dispersion layer. The electrode pad may be formed of a single layer structure of Ni or Cu, or a laminated structure of Ni and Cu.  
      In one embodiment, a solder bonding method of a magnetic head assembly that bonds electrode pads of a slider has a magnetoresistive element installed therein and electrode pads of a flexible printed circuit that connect the magnetoresistive element and an external circuit by solder. The method includes preparing a capillary that has a carrier path that carries a solder ball by an inert gas stream and melts the solder ball by a laser beam that passes through the carrier path, disposing the capillary on bonding surfaces between the electrode pads of the slider and the electrode pads of the flexible printed circuit, introducing the solder ball and an inert gas stream into the carrier path of the capillary and causing the solder ball to drop on the bonding surfaces of the electrode pads with the solder ball melted by the laser beam that passes through the same carrier path, waiting until the solder ball dropped is solidified, and remelting the solidified solder ball by laser beam irradiation to resolidify the remelted solder ball and bonding the electrode pads of the slider to the electrode pads of the flexible printed circuit.  
      For the second laser irradiation, a laser beam in the same axial direction as the capillary that passes through the carrier path of the capillary may be used, or a laser beam in an axial direction different from the capillary that is irradiated outside of the capillary may be used. For example, the laser irradiation onto the solidified solder ball may be performed by approaching the capillary to the solder ball and remelting the solder ball by the laser beam that passes through the carrier path of the capillary. Also, the laser irradiation onto the solder ball may be performed by remelting the solder ball by the laser beam irradiated from the direction different from the capillary.  
      In one embodiment of the solder bonding method, the laser beam is irradiated by using a semiconductor laser, an ultraviolet laser, or a YAG laser.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic diagram that illustrates the construction of a magnetic head assembly (finished state) according to one embodiment;  
       FIG. 2  is an enlarged schematic diagram that illustrates a joint portion of electrode pads of a slider and electrode pads of a flexible printed circuit that are shown in  FIG. 1 ;  
       FIG. 3  is an enlarged sectional view that illustrates a solder fillet in  FIG. 2 ;  
       FIG. 4  is a schematic plan view that illustrates a capillary that is used for a solder bonding method according to one embodiment;  
       FIG. 5  is a schematic plan view that illustrates a process of the solder bonding method according to one embodiment;  
       FIG. 6  is a schematic sectional diagram that illustrates a process next to the process in  FIG. 5 ;  
       FIG. 7  is a schematic sectional diagram that illustrates a process next to the process in  FIG. 6 ;  
       FIG. 8A  is a schematic sectional diagram that illustrates posture of a slider after first laser irradiation;  
       FIG. 8B  is a schematic sectional diagram that illustrates posture of a slider after second laser irradiation;  
       FIG. 9A  is a scatter diagram that shows a change in posture of a slider before and after solder bonding by one laser irradiation;  
       FIG. 9B  is a scatter diagram that shows a change in posture of a slider before and after solder bonding by two laser irradiations;  
       FIG. 10  is a schematic plan view that illustrates a capillary that is used for a solder bonding method according to another embodiment;  
       FIG. 11  is a cross-sectional view that illustrates a delivery end portion of a capillary in  FIG. 10  by partially fracturing the delivery end portion;  
       FIG. 12  is a side surface diagram that illustrates the delivery end portion of the capillary in  FIG. 10 ;  
       FIG. 13  is a plan view that illustrates the delivery end portion of the capillary in  FIG. 12 ;  
       FIG. 14  is a schematic sectional view that illustrates a process of a solder bonding method according to another embodiment;  
       FIG. 15  is a schematic sectional view that illustrates a process next to the process in  FIG. 14 ;  
       FIG. 16  is a schematic sectional view that illustrates a process next to the process in  FIG. 15 ;  
       FIG. 17  is a schematic sectional view that illustrates a process next to the process in  FIG. 16 ; and  
       FIG. 18  is a schematic sectional view that illustrates a process next to the process in  FIG. 17 . 
    
    
     DETAILED DESCRIPTION  
       FIG. 1  is a diagram that illustrates a magnetic head assembly (a finished state) for a hard disc drive according to one embodiment. A magnetic head assembly  1  includes a slider  11  that has a magnetoresistive element  12  (a magnetic head) installed therein, and a flexure  21  bonded to a rear surface of the slider  11  with, for example, a thermosetting adhesive, a UV curable adhesive, a conductive adhesive, or the like.  
      The flexure  21  is a thin flexible sheet metal that has a plate spring shape. The flexure  21  is mounted on a front end of a load beam in a state where the flexure  21  floatingly supports the slider  11  elastically relative to the load beam. A flexible printed circuit (FPC)  22  is fixed to the surface of the flexure  21  by adhesion that uses an adhesive. The flexible printed circuit  22  electrically connects the magnetoresistive element of the slider  11  to a circuit system of a hard disc device on which the magnetic head assembly is mounted.  
      As shown in  FIG. 2 , the flexible printed circuits  22  are divided into two edge portions from a plurality of electrode pads  23  disposed at front ends of the flexures  21  and are further extended from both edge portions. The flexible printed circuits  22  are further extracted from edge portions of rear ends of the flexures  21 , and collected as one flexible printed circuit through a relay flexible printed circuit  24 . The relay flexible printed circuit  24  is connected to the circuit system of the hard disc device on which the magnetic head assembly  1  is mounted. The slider  11  has a plurality of electrode pads  13  that are connected to the magnetoresistive element  12  in a slider section  11   a . The electrode pads  13  and the electrode pads  23  of the flexible printed circuit  22  are mounted on the flexure  21  in a perpendicular position in relation to each other.  
      In one embodiment of the magnetic head assembly  1  the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22 , which are provided according to orthogonal positional relationships, are solder-ball bonded using tin-based Sn solder that does not contain lead.  
      As shown in  FIG. 3 , a solder fillet  41  (a solder joint) bonds the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22 . Au plating layers  13   a  and  23   a  are formed on surfaces (solder contact layers) of the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22  so as to improve solder wettability.  
      In one embodiment, even though most of the solder fillet  41  is formed of solidified Sn solder  42 , an AuSn dispersion layer  43  exists at least along the boundary of the electrode pads  13  and  23  and the Sn solder  42 . The AuSn dispersion layer  43  is generated as follows. An AuSn compound is formed on the surfaces of the electrode pads  13  and  23 , when the Sn solder  42  is melted and solidified for the first time. When the Sn solder  42  is melted for the second time, the AuSn compound is dispersed into the Sn solder  42 . The Sn solder  42  is solidified again in a state where the AuSn compound is dispersed into the Sn solder  42 . An Au atomic concentration of the AuSn dispersion layer  43  at the electrode pads  13  and  23  is higher than that at the Sn solder  42 . The Au plating layers  13   a  and  23   a  are in a range of about 0.5 to 2.6 μm in thickness. The AuSn dispersion layer  43  has the thickness equal to or more than about 50 μm.  
      Referring to FIGS.  4  to  8 , a solder bonding method according to a first embodiment will be described.  
      As shown in  FIG. 4 , a capillary  30  is prepared. The capillary  30  is a single-capillary that bonds spherical solder balls  40  one by one. The capillary  30  has an elongated cylindrical shape and includes a delivery end portion  30   a  whose tip is narrow.  
      The capillary  30  includes a circular delivery hole  31  that is formed at the center of a front end surface of the delivery end portion  30   a  so as to deliver the spherical solder ball  40 . A carrier path  32  that extends along an axial direction of the capillary  30  carries the spherical solder ball  40  and a nitrogen gas stream N 2  to the circular delivery hole  31 . The capillary  30  is connected to a laser heat source. A YAG laser is used as the laser heat source. The laser beam outputted from the laser heat source has the center of the light beam in parallel with the axial direction of the capillary  30 .  
      The laser beam passes through the carrier path  32  and then it is emitted from the delivery hole  31  to the outside. The laser beam is irradiated onto the solder ball  40  when the solder ball  40  is carried along the carrier path  32  by the nitrogen gas stream N 2 .  
      The solder ball  40  in the melted state is discharged from the delivery hole  31  to the outside. Though not shown, the capillary  30  includes an introduction hole through which the spherical solder ball  40  and the nitrogen gas stream N 2  are inserted into the carrier path  32 . In the present embodiment, the solder ball  40  is not more than about φ100 μm in diameter, and an effective spot diameter of the laser beam used is about φ100 μm.  
      As shown in  FIG. 5 , the slider  11  and the flexible printed circuit  22  are provided on a mount with the electrode pads  13  and  23  thereof meeting each other at about 90 degrees. The mount is fixed and tilted 45 degrees counterclockwise from a horizontal direction (a right and left direction in  FIG. 5 ). The capillary  30  is tilted about 45 degrees from both of the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22 , for example, the capillary  30  is provided along a vertical direction (an up and down direction in  FIG. 5 ). The delivery end portion  30   a  of the capillary  30  is spaced by about 50 μm from a joint surface of the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22 .  
      As shown in  FIG. 6 , the solder ball  40  and the nitrogen gas stream N 2  are introduced into the carrier path  32  of the capillary  30 , and the laser heat source is operated to output a laser beam to the carrier path  32 . The solder ball  40  is formed of tin-based solder that does not include lead, and is not more than about Ø100 μm in diameter. The solder ball  40  inserted into the carrier path  32  is melted by the laser beam that proceeds in parallel with the axial direction of the capillary  30 . The molten solder ball  40  is sent to the delivery hole  31  by the nitrogen gas stream N 2  that flows through the same carrier path. The molten solder ball  40  free falls between the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22  from the delivery hole  31 . As soon as the solder ball  40  rapidly cools down by the electrode pads  13  and  23 , which are a falling point, for example, before Au is sufficiently dispersed into the solder, the solder ball  40  is solidified. Since the Au plating layers  13   a  and  23   a  are formed on the surfaces of the electrode pads  13  and  23 , an AuSn compound layer is formed along the boundary of the electrode pads  13  and  23  and the Sn solder  42 .  
      As shown in  FIG. 8A , since the flexure  21  is subjected to shrinkage distortion by the solidification of the solder ball  40 , the flexure  21  is bent counterclockwise from the horizontal direction. Oxidization of the solidified solder ball  40  is prevented by the nitrogen gas stream N 2 . By the above-described process, the first melting and solidification are performed.  
      As shown in  FIG. 7 , as the capillary  30  approaches the solidified solder ball  40 , the laser beam is irradiated onto the solder ball  40  at a close distance. Laser irradiating time is set long enough to completely melt the solder ball  40 , for example, the laser irradiating time is equal to and more than about 10 ms. A laser beam that is irradiated in a different direction from the capillary  30  may be used for the laser irradiation.  
      When the solder ball  40  is completely melted, the AuSn compound layer formed on the surfaces of the electrode pads  13  and  23  is dispersed into the molten solder. The molten solder, which includes the dispersed Au atoms, is solidified, thereby forming the solder fillet  41  (See  FIG. 3 ). In the solder fillet  41  that is formed by this second melting and solidification, the AuSn dispersion layer  43  is generated at least along the boundary between the electrode pads  13  and  23  and the solidified Sn solder  42 . The Au atomic concentration of the AuSn dispersion layer  43  at the electrode pads  13  and  23  is higher than that at the Sn solder  42 . As the AuSn dispersion layer  43  is generated, the AuSn compound layer, which is generated by the first melting and solidification, disappears. Therefore, an SnNi or CnSn compound is formed and bond strength of the solder fillet  41  is increased. Experiments show that when the AuSn dispersion layer  43  is equal to or more than about 50 μm in thickness, sufficient bond strength is given to the solder filet  41 .  
      In one embodiment, when the solder ball  4  is melted twice as described above, the shrinkage distortion that is applied to the flexure  21  is relieved, and the flexure  21  is likely to return to its horizontal state before the solder bonding. Since the second melting and solidification are performed on the electrode pads  13  and  23 , the Sn solder  42  slowly falls in temperature and is solidified after being melted (not rapid cooling). Therefore, the shrinkage distortion caused by the second solidification of the Sn solder  42  is not more than the shrinkage distortion caused by the first solidification thereof.  
      As shown in  FIG. 8B , since the flexure  21  subjected to the solidification performed twice is less bent than the flexure  21  subjected to the solidification performed once (see  FIG. 8B ), such that a change in posture of the slider  11  is controlled and small.  
      The electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22  are bonded to each other by the solder fillet  41 .  
       FIG. 9  is a scatter diagram that shows a change in posture (a change in pitch angle of the slider  11  before and after solder bonding.  FIG. 9A  shows a change in posture of the slider  11  in a case of the solder bonding by one laser irradiation (i.e., the solder ball  40  in a molten state free falls to the joint surface from the capillary  30 ).  FIG. 9B  shows a change in posture of the slider  11  in a case of the solder bonding by two laser irradiations (i.e., second laser irradiation is performed on the joint surface after the first laser irradiation). Measurement conditions for the change in posture of the slider are as follows.  
      Device: SBB (Solder Ball Bumper) manufactured by PacTech  
      Laser irradiation (first time): 40A for 2 ms  
      Laser irradiation (second time): 38A for 15 ms  
      Diameter of solder ball: 100 μm  
      As shown in  FIGS. 9A and 9B , it is clear that a change in pitch angle before and after bonding is smaller in two laser irradiations than that in one laser irradiation. For example, an average value of changes in pitch angle after first laser irradiation is −68′, while and an average value of changes in pitch angle after the second laser irradiation is −26.5°. Therefore, the change of pitch angle after the second laser irradiation is regulated at half or less than the change of pitch angle after the first laser irradiation.  
      As the solder bonding method that forms the solder fillet  41  of  FIG. 3 , the embodiment in which the Sn solder  42  is melted and solidified by performing the two laser irradiations has been described. However, it is possible to form the solder fillet  41  without generating the AuSn compound layer on the surfaces of the electrode pads  13  and  23  by performing one laser irradiation.  
      Hereinafter, a solder bonding method by performing one laser irradiation according to another embodiment of will be described with reference to FIGS.  10  to  18 .  
      A capillary  130  shown in FIGS.  10  to  13  is prepared. The capillary  130  has a thin, long, and cylindrical shape and includes a delivery end portion  130   a  whose tip is narrow. The capillary  130  includes a circular delivery hole  131  that is formed at the center of a front end surface of the delivery end portion  130   a  so as to deliver a spherical solder ball  40 . A carrier path  132  extends along an axial direction of the capillary  130  and carries the solder ball  40  and a nitrogen gas stream N 2 . A plurality of notch portions  134  are formed at a front end wall (a delivery wall) at predetermined intervals in a circumferential direction. The plurality of notch portions  134  serve as both an opening for discharging a nitrogen gas stream N 2 , which passes through the carrier path  132  and reaches the delivery hole  131 , to the outside, and an opening for passing a laser beam irradiated from a different direction from a carrying direction of the solder ball  40 . Each of the notch portions  134  is a trapezoid in section (See  FIG. 12 ) where the notch portion  134  gets wider toward the front end of the delivery end portion  130   a  such that it is easy to directly irradiate a laser beam onto the solder ball  40 .  
      As shown in  FIG. 13 , the plurality of notch portions  134  are four notch portions obtained by cutting the front end wall of the delivery end portion  130   a  at 90-degree intervals, and emit a nitrogen gas stream N 2  in a crosswise direction from the delivery hole  131 . Though not shown, the capillary  130  includes an induction hole through which the solder ball  40  and the nitrogen gas stream N 2  are inserted into the carrier path  132 .  
      In one embodiment, the solder ball  40  is not more than about Ø100 μm in diameter, the delivery hole  131  and the carrier path  132  are more than the solder ball  40  in diameter. Depth of the notch portions  134  is less than that of the solder ball  40 , an effective spot diameter of the laser beam used is in a range of about Ø50 to 100 μm.  
      As shown in  FIG. 14 , the capillary  130  is tilted about 45 degrees from both the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22 . The delivery end portion  130   a  of the capillary  30  is spaced about 20 μm from the joint surface of the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22 . Therefore, a space a for mounting and maintaining the solder ball  40  is formed between the electrode pads  13  of the slider  11 , the electrode pads  23  of the flexible printed circuit  22 , and the delivery end portion  130   a  (the delivery hole  131 ) of the capillary  130 .  
      As shown in  FIG. 15 , the spherical solder ball  40  is inserted into the carrier path  132  of the capillary  130 , and at the same time, the nitrogen gas stream N 2  is introduced into the carrier path  132  of the capillary  130 . The solder ball  40 , which is inserted into the carrier path  132  and is not melted, is sent to the delivery hole  131  by the nitrogen gas stream N 2  that flows within the same carrier path  132 . The solder ball  40  in a state of not being melted free falls between the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22  from the delivery hole  131 . The solder ball  40  is formed of tin-based solder that does not include lead, and oxidization of the solder ball  40  is prevented by the nitrogen gas stream N 2 .  
      As shown in  FIG. 16 , position of the solder ball  40 , which has free fallen, is determined and maintained on the joint surface of the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22  by the nitrogen gas stream N 2  that is radially emitted from the plurality of notch portions  134  formed at the front end wall of the delivery end portion  130   a . In one embodiment, it is ideal that the solder ball  40  free falls right under the central position of the delivery hole  131  from the delivery hole  131 . The solder ball  40  may be separated from the central position of the deliver hole  131 . In the present embodiment, since four notch portions  134  are formed at about 90 degree intervals in the circumferential direction of the front end wall of the delivery end portion  130   a , if the solder ball  40  is separated from the central position of the delivery hole  131 , the nitrogen gas stream N 2  becomes as narrow as the separation of the solder ball  40 , and the solder ball  40  returns to the center by a repulsive force applied from the nitrogen gas stream N 2 . Therefore, the solder ball  40  is always maintained at the central position of the delivery hole  131 .  
      As shown in  FIG. 17 , the solder ball  40  is maintained by the nitrogen gas stream N 2  and the delivery hole  131 , a laser beam passes through the plurality of notch portions of the capillary  130  and is directly irradiated onto the solder ball  40 . In  FIG. 17 , reference mark  2  denotes a laser irradiation position. The laser irradiation is performed by a separate laser heat source from the capillary  130  in a direction different from the direction in which the delivery hole  131  of the capillary  130  faces (i.e., the direction in which the solder ball  40  is carried by the nitrogen gas stream N 2 ).  
      For example, like the capillary  30 , in a state where the capillary  130  is tilted about 45 degrees from both sides of the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22 , the laser beam is irradiated from a direction in which the capillary  30  is rotated clockwise or counterclockwise at a predetermined angle. At this time, since power of the laser beam completely melts the solder ball  40 , the power is set such that an effective spot diameter of the laser beam is slightly smaller than the solder ball  40 .  
      In one embodiment, since the solder ball  40  having a diameter of about 100 μm is used, it is preferable that the effective spot diameter of the laser beam be about 50 μm. As a laser heat source, a semiconductor laser that emits a laser beam of low energy or an ultraviolet laser may be used. Since the plurality of notch portions  134  are formed in a trapezoid section where each of the notch portions  134  gets wider toward the front end of the delivery end portion  130   a  so as to easily pass the laser beam, loss of laser beam is low. Therefore, it is possible to effectively apply the laser beam to the solder ball  40 .  
      As shown in  FIG. 18 , when the laser irradiation starts, the capillary  130  is made separate from the joint surface of the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22 , and the laser irradiation continues for a predetermined time so as to completely melt the solder ball  40 . By the solder fillet  41  that is solidified again after being completely melted, the electrode pads  13  of the slider  11  and the electrode pads  23  of the flexible printed circuit  22  are bonded to each other.  
      According to another embodiment, even though the laser irradiation is performed once, the solder ball  40  is completely melted on the joint surface. Therefore, at the solder fillet  41 , the AuSn dispersion layer  43  in which Au plating layers  13   a  and  23   a  on the surfaces of the electrode pads  13  and  23  are dispersed within the molten solder is formed at least along the boundary of the electrode pads  13  and  23 . For example, since an AuSn compound layer is not formed but a SnNi or CuSn compound is formed, sufficient bond strength can be applied to the solder fillet  41 . In addition, since the solder melted by the laser irradiation does not rapidly cool down, shrinkage distortion caused by solidification of the solder can be reduced. Therefore, it is possible to appropriately prevent a change in posture of the slider  11 .  
      In present exemplary embodiments, the nitrogen gas stream N 2  is used when carrying the solder ball  40 . However, in addition to the nitrogen gas stream N 2 , inert gas streams, such as He, Ne, Ar or the like, may be used. In addition, the Sn solder that does not include lead is used as the solder ball, but lead-based solder or tin-based solder may be used.  
      In at least one embodiment, it is possible to achieve the magnetic head assembly and the solder bonding method thereof that are capable of increasing bond reliability and a change in posture of the slider.  
      Various embodiments described herein can be used alone or in combination with one another. The forgoing detailed description has described only a few of the many possible implementations of the present invention. For this reason, this detailed description is intended by way of illustration, and not by way of limitation. It is only the following claims, including all equivalents that are intended to define the scope of this invention.