JP2007310968A - Solder joining method of magnetic head assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solder joining method of a magnetic head assembly in which re-work operation is easy and solder joining can be performed accurately. <P>SOLUTION: This is the method in which solder joining is performed for an electrode pad and a junction pad corresponding to a suspension, first, a solder ball is fixed temporarily to respective pads of the magnetic head slider in a state in which at least one part is projected to the lower side than the slider lower plane. Next, the solder ball on the junction pad is melted in a state in which the temporarily fixed solder ball is abutted to respective pads of the suspension, the magnetic head and the suspension are adhered and fixed. Successively, the temporarily fixed solder ball is melted abutting it to the electrode pad of the suspension, and the magnetic head slider and the electrode pad of the suspension are joined. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of soldering a magnetic head assembly in which a magnetic head slider and a suspension are soldered and the electrode pad of the magnetic head slider and the electrode pad of the suspension are soldered.

  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 in which the magnetic head slider is bonded and fixed with a thermosetting adhesive. 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 magnetic head slider and the electrode pads of the suspension (flexible wiring board) are solder balls that can be formed with a sphere diameter smaller than that of the gold balls so that the bonding area (electrode pad size and electrode pad spacing) can be reduced. Bonded by the used solder ball bonding.

  This type of magnetic head assembly is subjected to dynamic characteristic inspection before shipment. The dynamic characteristic inspection is performed with the magnetic head slider attached to the suspension and mounted on a spin stand or the like and the hard disk is rotated. This dynamic characteristic inspection is generally a final characteristic inspection, and if the dynamic characteristic that is the inspection result does not satisfy the standard, it is determined as defective. At this time, the magnetic head slider determined to have poor characteristics is peeled off from the suspension and discarded, and the suspension is reused. This rework work requires great care because the flexure that is part of the suspension is very fragile and easily deforms.

  Conventionally, the solder joint is remelted to eliminate the solder joint between the magnetic head slider and the suspension, and the adhesive strength of the thermosetting adhesive between the magnetic head slider and the suspension is weakened in advance by heating or the like before the magnetism. Although the head slider is forcibly removed, the thermosetting adhesive often remains on the suspension after the slider is peeled off, and the suspension cannot be reused unless the remaining thermosetting adhesive is removed. The removal of the thermosetting adhesive is forcibly performed using a solvent or the like, which may cause a secondary harmful effect, which is not preferable.

Therefore, in recent years, a method has been proposed in which a magnetic head slider and a suspension are bonded only by solder bonding without using a thermosetting adhesive.
JP-A-63-113917 JP 2002-367132 A JP 2004-283911 A

  However, if the magnetic head slider and the suspension are to be bonded and fixed only by soldering, the attitude of the magnetic head slider may be shifted due to shrinkage distortion or the like that occurs when the solder is solidified, or the supply position of the solder balls may vary. It is difficult to ensure the joining accuracy. The problem is how to solder joints accurately without using a thermosetting adhesive.

  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 method for soldering a magnetic head assembly that allows easy reworking and enables accurate soldering.

  According to the present invention, if the solder balls are temporarily fixed to the magnetic head slider in advance, it is possible to suppress variations in the supply position of the solder balls. If the solder balls are temporarily fixed so that a part of the solder balls protrude below the lower surface of the slider, It was completed by focusing on the fact that a solder fillet can be reliably formed between the slider and the suspension, and that the change in the slider posture after soldering can be suppressed if the electrode pads are soldered together after the magnetic head slider and the suspension are bonded and fixed. It is a thing.

  That is, according to the present invention, the electrode pad for energizing the magnetic head and the bonding pad for solder bonding exposed on the trailing surface and the leading surface of the magnetic head slider are respectively solder-bonded to the corresponding electrode pad and bonding pad of the suspension. A method of temporarily fixing a solder ball to each of an electrode pad and a solder bonding pad of a magnetic head slider with at least a part protruding below the lower surface of the slider, and a magnetic field after the temporary fixing The process of moving the head slider onto the suspension and the solder ball on the bonding pad completely melted by laser irradiation with the temporarily fixed magnetic head slider solder ball in contact with the electrode pad and bonding pad of the suspension And wait until the melted solder balls are solidified, The step of bonding and fixing the air head slider and the suspension, and the solder ball on the electrode pad being completely melted by laser irradiation while the solder ball of the magnetic head slider after the bonding and fixing is in contact with the electrode pad of the suspension And a process.

  In the solder ball temporary fixing step, a pedestal having a convex cross-section having a slider installation surface on which the magnetic head slider is placed and a ball supply surface located on both sides of the slider installation surface and one step lower than the slider installation surface is prepared. A step of placing the magnetic head slider on the slider mounting surface with the trailing surface and the leading surface facing the ball supply surface, and supplying a solder ball to the ball supply surface. And preferably temporarily fixing the solder balls to the electrode pads and the bonding pads of the magnetic head slider.

  In the cradle, at least the ball supply surface is preferably formed of any one of WC, Mo, Cr, and stainless steel. Since the above material has a property that the molten solder is difficult to adhere, the solder melted on the ball supply surface is bonded to the electrode pad and the bonding pad of the magnetic head slider without adhering to the ball supply surface.

  It is practical to temporarily fix the solder balls by locally heating the solder balls by laser irradiation or ultrasonic vibration.

  In the step of moving the magnetic head slider after temporary fixing, it is preferable that the side surface of the magnetic head slider on which the electrode pad and the bonding pad are not formed is sandwiched by a clamper and slid to the suspension. The clamper is preferably retracted after the molten solder on the bonding pad is solidified.

  When the solder ball is completely melted, it is preferable to set the laser irradiation position based on the position of the solder ball detected by image processing. Thereby, the solder ball can be reliably melted, and a solder fillet can be formed between the magnetic head slider and the suspension.

  When the solder balls on the bonding pads are completely melted, it is preferable to perform laser irradiation from the side of the magnetic head slider where the electrode pads and bonding pads are not formed. On the other hand, when the solder balls on the electrode pads are completely melted, it is preferable to perform laser irradiation from a position inclined at a predetermined angle with respect to the electrode pads of the magnetic head slider and the electrode pads of the suspension.

  According to the present invention, it is possible to obtain a soldering method for a magnetic head assembly that allows easy reworking and enables accurate soldering.

  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 in which the magnetic head slider 11 is bonded and fixed with solder. 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.

  2 and 3 are plan views showing the magnetic head slider 11 and the suspension 21 (slider installation surface) as a single unit. The magnetic head slider 11 is provided with a plurality of electrode pads 13 exposed on the trailing surface 11a and a plurality of bonding pads 14 exposed on the leading surface 11b opposite to the trailing surface 11a. The plurality of electrode pads 13 are electrically connected to the magnetic head 12 and are arranged at predetermined intervals on the trailing surface 11a. The plurality of bonding pads 14 are electrically non-connected dummy pads and are provided for soldering the magnetic head slider 11 to the suspension 21. In the present embodiment, four electrode pads 13 and two bonding pads 14 are provided. On the other hand, an electrode pad 23 and a bonding pad 24 corresponding to each electrode pad 13 and each bonding pad 14 of the magnetic head slider 11 are formed on the suspension 21 on a one-to-one basis. The electrode pads 13 and 23 and the bonding pads 14 and 24 are made of, for example, an electrode material such as Cu or Cu / Ni, and the surfaces (solder contact surfaces) thereof are covered with an Au plating film that improves solder wettability. The electrode pad 13 and the bonding pad 14 of the magnetic head slider 11 and the electrode pad 23 and the bonding pad 24 of the suspension 21 are arranged in a positional relationship orthogonal to each other, and contain Sn solder (solder fillet 43T, 43R). FIGS. 4A and 4B are a plan view and a cross-sectional view showing a solder joint between the magnetic head slider 11 and the suspension 21.

  With reference to FIGS. 5 to 9, an embodiment of a soldering method according to the present invention will be described. 5 to 9 are cross-sectional views or plan views showing respective steps of the solder bonding method.

  First, the cradle 40 and the capillary 41 shown in FIG. 5 are prepared.

  The cradle 40 has a convex cross section having a slider installation surface 40a on which the magnetic head slider 11 is placed and a pair of ball supply surfaces 40b that are located on both sides of the slider installation surface 40a and are one step lower than the slider installation surface 40a. There is no. The slider installation surface 40a is a flat surface, and is formed corresponding to the slider dimension (the dimension from the trailing surface 11a to the leading surface 11b of the magnetic head slider 11) in the horizontal direction in the figure. The pair of ball supply surfaces 40b are surfaces for setting (supplying, positioning and temporarily fixing) solder balls to the electrode pads 13 and the bonding pads 14 of the magnetic head slider 11, and are made of, for example, WC, Mo, C, or stainless steel. Thus, it consists of material which a solder material does not adhere easily. The ball supply surface 40b is also formed as a flat surface like the slider installation surface 40a. The step d between the slider installation surface 40a and the ball supply surface 40b is set according to the diameter of the solder ball to be used, and is at least smaller than the diameter of the solder ball.

The capillary 41 is a single-use capillary that bonds the solder balls one by one, and has a circular delivery port 41a that sends out the solder balls, and extends along the axial direction of the capillary 41 to reach the delivery port 41a. and a transport path 41b for conveying the flow N _2. A laser heat source is prepared around the capillary 41, and laser light from the laser heat source is irradiated from a direction different from the capillary 41. Although not shown, the capillary 41 also has an introduction port for introducing the solder ball and the nitrogen gas flow N ₂ into the transport path 41b. Specifically, in the present embodiment, a solder ball 42 having a diameter of 100 μm or less made of a solder material that does not contain lead and contains tin as a main component is used, and the effective spot diameter of the laser beam to be used is 50 μm.

  Next, as shown in FIG. 5, the magnetic head slider 11 is placed on the slider installation surface 40a of the cradle 40 with the trailing surface 11a and the leading surface 11b facing the ball supply surface 40b. Thereby, each electrode pad 13 and each bonding pad 14 of the magnetic head slider 11 are held in a state of projecting from the slider installation surface 40a to the ball supply surface 40b side.

Subsequently, as shown in FIG. 5, the solder balls 42 are supplied to the electrode pads 13 and the bonding pads 14 of the magnetic head slider 11 and temporarily fixed using the capillary 41. Specifically, first, after the capillary 41 is installed between the electrode pad 13 (or the bonding pad 14) of the magnetic head slider 11 and the ball supply surface 40b, the solder ball 42 and nitrogen gas are placed in the transfer path 41b of the capillary 41. A flow N ₂ is introduced, and a solder ball 42 is supplied between the electrode pad 13 (or the bonding pad 14) of the magnetic head slider 11 and the ball supply surface 40 b from the outlet 41 a by the nitrogen gas flow N ₂ flowing through the transfer path 41 b. Do (drop naturally). Next, the solder ball 42 is moved to an optimal joining position by pressing the nitrogen gas flow N ₂ ejected from the delivery port 41a. Then, a part of the solder ball 42 is melted by heating while holding the solder ball 42 by pressing the nitrogen gas flow. In the present embodiment, a part of the solder ball 42 is melted by laser light irradiated from a direction different from the axis of the capillary 41 while the cradle 40 is heated at about 100 ° C. The heating temperature of the solder ball 42 is preferably such that the solder ball 42 is locally melted but no solder fillet is formed, and specifically, about 227 (200 to 240) ° C. is preferable. When the solder ball 42 is melted on the ball supply surface 40b, the ball supply surface 40b is formed of a material that is difficult to adhere to solder as described above, so that the melted portion of the solder ball 42 is attached to the ball supply surface 40b. The magnetic head slider 11 adheres to and solidifies only on the electrode pad 13 (or bonding pad 14) side. Thereby, the solder ball 42 is temporarily fixed to the electrode pad 13 (or the bonding pad 14) of the magnetic head slider 11. The supply, positioning, and temporary fixing of the solder balls 42 are performed one by one with respect to the electrode pads 13 and the bonding pads 14 of the magnetic head slider 11, and the solder balls 42 are temporarily fixed to all the pads 13, 14. The solder ball 42 temporarily fixed on the ball supply surface 40b is at least partially below the lower surface 11c of the magnetic head slider 11 because the ball supply surface 40b is formed one step lower than the slider installation surface 40a. Protrudes. In other words, by using the cradle 40, the solder ball 42 can be easily moved in a state where at least a part of the solder ball 42 protrudes below the lower surface 11c of the magnetic head slider 11. And can be temporarily fixed with high accuracy.

  After temporarily fixing the solder balls 42, as shown in FIGS. 6 and 7, the clamper 44 sandwiches both side surfaces 11 d of the magnetic head slider 11 on which the solder balls 42 are not temporarily fixed, and slides them onto the suspension 21. Let By using the clamper 44, the temporarily fixed magnetic head slider 11 can be moved without damaging or removing the solder balls 42 temporarily fixed to the magnetic head slider 11.

  Subsequently, as shown in FIG. 7, the temporarily fixed magnetic head slider 11 moved onto the suspension 21 is soldered to the magnetic head slider 11, the electrode pads 23 of the suspension 21, and the bonding pads. 24 is held by the clamper 44 in a state of being in contact with each other. In this holding state, the lower surface 11 c of the magnetic head slider 11 is not in contact with the suspension 21.

  Subsequently, as shown in FIG. 7, the leading surface 11b of the magnetic head slider 11 is maintained with the solder ball 42 temporarily fixed to the magnetic head slider 11, the electrode pad 23 and the bonding pad 24 of the suspension 21 being in contact with each other. Each solder ball 42R is completely melted by laser irradiation. Here, the laser irradiation position is set based on the position of the solder ball 42R detected by the image processing, and the both side surfaces 11d side of the magnetic head slider 11 where the solder ball 42 is not fixed (the side orthogonal to the paper surface of FIG. 7). Irradiate with laser light. In FIG. 7, the laser irradiation positions are indicated by black circles. For example, when the solder ball 42R is completely melted at about 250 ° C. to 300 ° C., the molten solder spreads and solidifies between the bonding pad 14 of the magnetic head slider 11 and the bonding pad 24 of the suspension 21, and the solder fillet 43R. (FIG. 8) is formed. The magnetic head slider 11 and the suspension 21 are bonded via the solder fillet 43R and the bonding pads 14 and 24. The magnetic head slider 11 held by the clamper 44 receives a contraction strain due to the solidification of the solder ball 42 </ b> R and is attracted to the suspension 21 side, whereby the lower surface 11 c comes into contact with the suspension 21. In this embodiment, since the solder balls 42R are reflowed in a state where they are in contact with both the bonding pads 14 of the magnetic head slider 11 and the bonding pads 24 of the suspension 21, the solder fillet 43R can be formed reliably and high bonding can be achieved. Strength can be secured. The clamper 44 is retracted after joining the magnetic head slider 11 and the suspension 21.

  Subsequently, as shown in FIG. 8, the solder balls 42T are completely irradiated by laser irradiation while the solder balls 42T on the trailing surface 11a side of the magnetic head slider 11 and the electrode pads 13 of the suspension 21 are in contact with each other. Melt. Here, the laser irradiation position is set based on the position of the solder ball 42T detected by image processing, as in the case where the solder ball 42R on the leading surface 11b side is completely melted. The electrode pad 13 of the eleventh electrode and the electrode pad 23 of the suspension 21 are irradiated from a predetermined angle, in this embodiment, from a direction inclined by about 45 ° from both the electrode pads 13 and 23 (arrow direction in FIG. 8). When the solder ball 42T is completely melted, the melted solder spreads between the electrode pad 13 of the magnetic head slider 11 and the electrode pad 23 of the suspension 21 and solidifies to form a solder fillet 43T. Since the solder ball 42T is positioned at the time of temporary fixing and reflowed in contact with both electrode pads 13 and 23, variation in the solder joint position is suppressed and the solder fillet between the electrode pads 13 and 23 is surely provided. 43T can be formed and poor conduction can be prevented. Since the magnetic head slider 11 is already joined to the suspension 21 via the solder fillet 43R on the leading surface 11b side, the magnetic head slider 11 is not displaced even when contraction stress is generated due to solidification of the solder ball 42T.

  Through the above steps, the magnetic head assembly 1 (FIGS. 1 and 4) in which the magnetic head slider 11 and the suspension 21 are bonded and fixed by soldering is obtained. The magnetic head assembly 1 becomes a product if it is determined to be a non-defective product in a dynamic characteristic inspection performed with the hard disk actually rotated, but if the slider is determined to be defective, the suspension 21 is reused as a rework product. Therefore, a rework operation for removing the magnetic head slider 11 from the suspension 21 is performed. In the rework operation, the solder fillets 43R and 43T may be remelted, and the magnetic head slider 11 may be removed from the suspension 21. Since no thermosetting adhesive is used to join the magnetic head slider 11 and the suspension 21, the magnetic head slider 11 can be removed without damaging or deforming the suspension 21, and the suspension 21 can be easily reused.

  As described above, in the present embodiment, the solder balls 42 temporarily fixed to the electrode pads 13 and the bonding pads 14 of the magnetic head slider 11 are bonded in contact with the electrode pads 23 and the bonding pads 24 of the suspension 21, respectively. The magnetic head slider 11 and the suspension 21 are bonded and fixed by melting the solder balls 42 on the pads 14, 24, and the magnetic ball slider is further melted by melting the solder balls 42 in contact with the electrode pads 23 of the suspension 21. 11 and electrode pads 13 and 23 of the suspension 21 are joined. If the magnetic head slider 11 and the suspension 21 are soldered in this manner, the magnetic head slider 11 and the suspension 21 can be bonded and fixed without using a thermosetting adhesive, and the rework work is facilitated.

  In this embodiment, since the solder ball 42 is temporarily fixed to the magnetic head slider 11 in advance as described above, the solder ball 42 can be easily and accurately defined, and between the electrode pads 13 and 23 or the bonding pads 14 and 24. As compared with the case where the solder balls 42 are directly supplied and melted during this time, the variation in the solder joint position is suppressed, and the solder joint accuracy is improved.

  Further, in this embodiment, since the electrode pads 13 and 23 are soldered after the magnetic head slider 11 and the suspension 21 are bonded and fixed, the magnetic head slider 11 is not displaced even if contraction stress occurs due to the solidification of the solder balls 42. The bonding accuracy of the electrode pads 13 and 23 is also improved.

  Further, in the present embodiment, the solder balls 42 are melted while being in contact with the electrode pads 23 and the bonding pads 24 of the suspension 21, so that the soldering between the electrode pads 13 and 23 and between the bonding pads 14 and 24 is ensured. Fillets 43T and 43R are formed to prevent poor conduction between the electrode pads 13 and 23, and the bonding strength between the magnetic head slider 11 and the suspension 21 is improved.

  In this embodiment, since the solder ball 42 is temporarily fixed in a state of protruding below the lower surface 11c of the magnetic head slider 11, it is inevitable when the magnetic head slider 11 after temporary fixing is placed on the suspension 21. In addition, the solder balls 42 can be brought into contact with the pads 23 and 24 of the suspension 21. The temporary fixing can be easily performed by using a cradle 40 having a ball supply surface 40b that is one step lower than the slider installation surface 40a. In the temporary fixing step of the present embodiment, the solder ball 42 is partially melted by irradiating laser light from a direction different from the axial direction of the capillary 41, but by laser irradiation from the axial direction and the axial direction of the capillary 41. The solder ball 42 may be temporarily fixed, or the solder ball 42 may be temporarily fixed by ultrasonic vibration instead of laser irradiation.

It is a top view which shows the whole structure of the magnetic head assembly (completed state) which is an application object of this invention method. It is a top view which shows the magnetic head slider of FIG. 1 alone. It is a top view which shows the suspension (slider installation surface) of FIG. 2A is a plan view and FIG. 2B is a cross-sectional view showing a solder joint portion between the magnetic head slider and the suspension of FIG. 1. It is sectional drawing explaining 1 process of the soldering method of this invention. It is a top view explaining the next process of the process shown in FIG. It is sectional drawing explaining the next process of the process shown in FIG. It is sectional drawing explaining the next process of the process shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic head assembly 11 Magnetic head slider 11a Trailing surface 11b Leading surface 11c Lower surface 11d Side surface 12 Magnetic head 13, 23 Electrode pad 14, 24 Bonding pad 21 Suspension 40 Receiving base 40a Slider installation surface 40b Ball supply surface 41 Capillary 42 Solder ball 43T, 43R Solder fillet 44 Clamper

Claims (9)

A method of soldering a magnetic head energizing electrode pad and a solder bonding bonding pad exposed on a trailing surface and a leading surface of a magnetic head slider to a corresponding electrode pad and bonding pad of a suspension, respectively,
Temporarily fixing a solder ball to each of the electrode pad and the solder bonding pad of the magnetic head slider in a state in which at least a part of the solder ball protrudes below the lower surface of the slider;
The solder ball temporarily fixed to the magnetic head slider is in contact with the electrode pad and the bonding pad of the suspension, and the solder ball on the bonding pad is completely melted to bond and fix the magnetic head slider and the suspension. And a process of
Solder balls temporarily fixed to the magnetic head slider after being fixed by adhesion are completely melted while being in contact with the electrode pads of the suspension, and the electrode pads of the magnetic head slider and the electrode pads of the suspension are joined. And a process of
A method of soldering a magnetic head assembly, comprising: The method of soldering a magnetic head assembly according to claim 1, wherein in the temporary fixing step of the solder ball,
Preparing a pedestal having a convex cross section having a slider installation surface on which the magnetic head slider is placed and a ball supply surface located on both sides of the slider installation surface and one step lower than the slider installation surface;
Placing the magnetic head slider on the slider installation surface with the trailing surface and the leading surface facing the ball supply surface,
Supplying a solder ball to the ball supply surface, and temporarily fixing the solder ball to the electrode pad and the bonding pad of the magnetic head slider on the ball supply surface,
A method of soldering a magnetic head assembly comprising: 3. The method of soldering a magnetic head assembly according to claim 2, wherein at least the ball supply surface of the cradle is formed of any one of WC, Mo, Cr, and stainless steel. 4. The magnetic head assembly solder bonding method according to claim 1, wherein the solder ball is temporarily fixed by locally heating the solder ball by laser irradiation or ultrasonic vibration. Assembly soldering method. 5. The method of soldering a magnetic head assembly according to claim 1, wherein the side surface of the magnetic head slider on which the electrode pad and the bonding pad are not formed is clamped by a clamper after the solder ball is temporarily fixed. 6. Then, a method of soldering a magnetic head assembly, comprising a step of sliding the suspension onto the suspension. 6. The method of soldering a magnetic head assembly according to claim 5, wherein the clamper is retracted after the molten solder on the bonding pad is solidified. 7. The method of soldering a magnetic head assembly according to claim 1, wherein the solder ball is completely melted by laser irradiation, and the laser irradiation position is determined based on the position of the solder ball detected by image processing. The soldering method of the magnetic head assembly to be set. 8. The method of solder bonding of a magnetic head assembly according to claim 7, wherein the solder balls on the bonding pads are completely melted by laser irradiation from the side of the magnetic head slider where the electrode pads and bonding pads are not formed. Solder joining method for magnetic head assembly. 9. The method of soldering a magnetic head assembly according to claim 7, wherein the solder balls on the electrode pads are irradiated with a laser beam from a position inclined at a predetermined angle with respect to the electrode pads of the magnetic head slider and the electrode pads of the suspension. To solder the magnetic head assembly completely.

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