[19]
`United States Patent
`[11] Patent Number:
`5,821,494
`Albrecht et al.
`[45] Date of Patent:
`Oct. 13, 1998
`
`U8005821494A
`
`2/ 993 Ibaraki
`....... 360/103
`5,187,623
`3/993 Hayes
`228/180.2
`5,193,738
`
`3/994 Chaleo et a1.
`.
`219/121.64
`5,298,715
`
`4/ 994 Matsushita et a1.
`2287’18022
`5,299,729
`
`7/994 Bischoft et al.
`360/103
`5,327,310
`11/ 994 Ogashiwa
`420/502
`5,360,692
`
`1/ 995 Ogashiwa
`420/555
`5,384,090
`360/104
`Pattanaik
`6/ 996
`5,530,604
`300/104
`Frater et al.
`10/ 997
`5,680,275
`.. 360/104
`
`5,699,212 12/997
`Elpelding et a1.
`FOREIGN PATENT DOCUMENTS
`
`[54]
`
`[75]
`
`73
`
` 56
`
`
`
`METHOD OF ELECTRICAL CONNECTION
`BETWEEN HEAD TRANSDUCER AND
`SUSPENSION BY SOLDER WIRE BUMPING
`AT SLIDER LEVEL AND LASER REFLOW
`
`Inventors: David W. Albrecht, San Jose, Calif;
`Akihiko Aoyagi, Fuiisawa, Japan;
`Surya Pattanaik, San Jose, Calif;
`Yoshin Uematsu, Fujisawa, Japan
`
`Assignee:
`
`International Business Machines
`Corporation, Armonk, NY.
`
`Appl. No.1 722,536
`
`Filed:
`Int. Cl.6
`US. Cl.
`
`Sep. 27, 1996
`B23K 26/00
`
`
`.. 219/121.64; 29/60306;
`228/1 80.22; 228/1115
`29/60304, 603.06;
`Field of Search
`228718022, 1115; 360/104; 219/121.64,
`121.66, 121.85
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`.
`
`3,463,898
`8/1969 Takaoka et a1.
`4,761,699
`8/1988 Ainslie et a1.
`.
`...... 360/103
`4,789,914 12/1988 Ainslie et al.
`360/104 X
`
`.. 228/110
`4,893,742
`1/1990 Bullock
`. 219/12163
`4,970,365
`11/1990 Chaleo
`
`4,996,623
`2/1991 Erpelding et al
`.. 360/104
`5,001,583
`3/1991 Matsuzaki .................... 360/104
`5,124,277
`6/1992 Tsumura .
`
`...... 228/179
`5,172,851
`12/1992 Matsushita et al.
`
`5,177,860
`1/1993 Yura et al.
`.............
`.. 29/60307
`
`
`
`0 671 727 A1
`0 683 491 A2
`62-173074
`WO 95/00279
`
`9/ 995
`11/ 995
`7/ 987
`1/ 995
`
`.
`European Pat. Off.
`European l—‘at. Oll. .
`Japan .
`WIPO .
`
`Primary Examiner—Gregory L. Mills
`Attorney, Agent, or Firm—Gray Cary Ware Frcidenrieh
`
`[5 7]
`
`ABSTRACT
`
`A method of making a solder connection between a slider
`pad and a suspension pad is provided by forming a solder
`bump on the solder pad at the slider level, affixing the slider
`to the suspension so that solder can be reflowed between the
`slider pad and the suspension pad and then employing a laser
`beam to reflow at least the solder bump to form a solder
`connection between the slider pad and the suspension pad,
`Various embodiments of the method are employed for
`forming the solder connection. Geometric features are also
`optionally incorporated in the suspension pad region of the
`integrated suspension that can be employed to bias the
`suspension pads against the solder bumps in the pre—reflow
`state.
`
`56 Claims, 12 Drawing Sheets
`
`
`
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`
`

`

`US. Patent
`
`Oct. 13, 1998
`
`Sheet 1 0f 12
`
`5,821,494
`
`30
`/
`
`
`MOTOR
`CONTROL
`
`
`
`
`
`Egg
`
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`
`

`

`US. Patent
`
`Oct. 13,1998
`
`Sheet 2 0f 12
`
`5,821,494
`
`
`
`FIG. 4
`
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`
`

`

`US. Patent
`
`Oct. 13, 1998
`
`Sheet 3 of 12
`
`5,821,494
`
`
`
`Nitto Ex. 1004
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`
`

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`US. Patent
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`

`

`US. Patent
`
`Oct. 13,1998
`
`Sheet 5 0f 12
`
`5,821,494
`
`
`
`FIG. BB
`
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`
`

`

`US. Patent
`
`Oct. 13,1998
`
`Sheet 6 0f 12
`
`5,821,494
`
`91.
`
`62
`
`[:3
`
`FIG. 9A
`
`93
`
`94
`
`g
`
`50
`
`N 2
`
`Laser
`Beam
`
`94
`
`FIG. QB
`
`I
`100
`
`N2
`
`“118
`4 ———
`
`
`————-—~————-——
`----————_-—-----—.-__
`
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`
`FIG. 1GB
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`
`

`

`US. Patent
`
`Oct. 13,1998
`
`Sheet 7 0f 12
`
`5,821,494
`
`11A
`
`FIG.
`
`120
`
`
`
`4/.
`
`FIG. 11C
`
`6"
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`
`

`

`US. Patent
`
`Oct. 13,1998
`
`Sheet 8 0f 12
`
`5,821,494
`
`
`
`z.4/
`
`FIG. 12A
`
`
`
`1,],
`
`FIG. 12B
`
`
`
`4,,
`
`FIG. 120
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`
`

`

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`
`US. Patent
`
`Oct. 13, 1998
`
`Sheet 9 0f 12
`
`5,821,494
`
`
`
`

`

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`US. Patent
`
`Oct. 13, 1998
`
`Sheet 10 0f 12
`
`5,821,494
`
`
`
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`
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`
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`
`

`

`US. Patent
`
`Oct. 13,1998
`
`Sheet 11 0f 12
`
`5,821,494
`
`
`. 21C
`
`FIG. 21B
`
`42
`
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`

`

`US. Patent
`
`Oct. 13, 1998
`
`Sheet 12 0f 12
`
`5,821,494
`
`FIG. 223
`
`
`
`61.
`
`FIG. 220
`
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`

`

`5,821,494
`
`1
`METHOD OF ELECTRICAL CONNECTION
`BETWEEN HEAD TRANSDUCER AND
`SUSPENSION BY SOLDER WIRE BUMPING
`AT SLIDER LEVEL A\ID LASER REFLOW
`
`m
`
`CROSS REFERENCE TO RELATED PATENTS
`
`1. Commonly assigned L.S. Pat. No. 5,530,604 for
`“Transducer Head Solder Connection”;
`2. Commonly assigned I. .8. Pat. No. 4,996,623 for
`“Laminated Suspension for a Negative Pressure Slider in a
`Data Recording Disk File”;
`3. Commonly assigned LS. Pat. No. 4,761,699 for
`“Slider—Suspension Assembly and Method for Attaching a
`Slider to a Suspension in a Data Recording Disk File”;
`4. Commonly assigned LS. Pat. No. 4,970,365 for
`“Method and Apparatus for Bonding Components Leads to
`Pads Located on a Non—Rigid Substrate”; and
`5. Commonly assigned L.S. Pat. No. 5,298,715 for
`“Lasersonic Soldering of Fine Insulated Wires to Heat—
`Sensitive Substrates”.
`The above patents are incorporated by reference herein,
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The present invention relates to slider-suspension assem—
`blies for data recording information storage systems and to
`a method for making such assemblies.
`In particular the
`invention relates to a method of electrical interconnection
`between the read/write head transducers and the suspension
`leads by solder bumping the pads at the slider level followed
`by a laser reflow.
`2. Description of the Related Art
`A magnetic disk drive rotates a magnetic disk adjacent a
`magnetic head which is mounted on a slider. The slider is
`supported by a suspension connected to an actuator that
`positions the magnetic head over selected information tracks
`on the disk. Such a slider-suspension assembly is also
`known as a head gimbal assembly. The suspension loads the
`slider on the disk with a force which is counterbalanced by
`an air bearing between the disk and an air bearing surface
`(ABS) of the slider. A typical suspension has a metallic
`flexure attached to a metallic load beam. The suspension
`allows the slider to pitch and roll with respect to the disk
`while applying the loading force toward the disk. The slider
`is mounted to the llexure portion of the suspension and has
`exposed electrical pads connected to components of the
`magnetic head. Discrete electrical wires, which extend from —
`he read/write electronics, are connected to the head termi—
`nation pads on the slider for conducting signals to and from
`he magnetic head.
`More recently, suspensions with integrated electrical con-
`ductors in the [lexure member have been built from lami—
`nated structures which are fully described in the aforemen-
`ioned US. Pat. No. 4,996,623. Such suspensions are
`ieneeforth referred to as integrated suspensions. The lami-
`nated structure includes a polyimide layer sandwiched
`)etwee n a steel layer and a copper layer. The copper layer is
`etched to provide leads which terminate at suspension pads
`and the steel layer provides the supporting structure, The
`eads take the place of the aforementioned discrete electrical
`wires. The slider pads are then connected to the suspension
`jads by various methods.
`One method of connecting a slider pad to a suspension
`ead pad is described in the cross-referenced US. Pat. No.
`
`/
`
`mo
`
`L»;m
`
`mm
`
`60
`
`65
`
`
`
`
`
`2
`5,530,604. A solder bump is provided on each slider pad at
`the wafer level, and a solder bump is provided on each
`suspension lead pad. The slider is then attached to the
`suspension by adhesive bonding and the two solder bumps
`are reflowed to form the electrical interconnection by a laser
`beam. Typically there are several thousands of sliders on a
`wafer. Solder is applied to slider pads by screen printing
`solder paste through a mask and reflowing the paste to form
`solder bumps. The wafer is then subjected to a slider
`fabrication process which consists of dicing the wafer into
`rows, creating the air bearing surface (ABS), and then
`further dicing into discrete sliders (slider level). During the
`slider fabrication process the rows are bonded to fixtures for
`processing and after dicing they are debonded by heat and
`solvents. The rows are also lapped with a grinding slurry and
`then subjected to dry etching processes to create the afore—
`mentioned ABS. Cleaning processes which consist of blast-
`ing with abrasive slurry (as used in dental cleaning) are also
`employed to remove adhesives and photoresist. It has been
`observed that all the aforementioned bonding, debonding,
`lapping and cleaning processes seriously damage the solder
`bumps by oxidation and erosion leading to problems in
`forming the interconnection. The present
`invention is an
`improvement of the process in US. Pat. No. 5,530,604 by
`implementing novel and unique solder connections between
`slider pads and suspension pads at the slider level.
`In European Patent application (EPA) No. 941196222,
`published Sep. 13, 1995 under No. 0 671 727 A1, a slider
`pad is connected to a suspension pad by gold ball bonding.
`The EPA does not employ laser reflow. In US. Pat. No,
`4,761,699 a slider pad is connected to a suspension pad by
`solder reflow. Solder bumps are constructed on the slider
`pads at the wafer level and a laser is not employed for reflow.
`In US. Pat. No. 5,298,715 wires are connected between
`slider pads and suspension pads by solder bonding. The
`solder bonding is implemented by simultaneous ultra-sonic
`bonding and laser heating. In US. Pat. No. 4,970,365 leads
`are connected to circuit boards by gold bonding. The gold
`bonding is implemented by simultaneous ultra-sonic bond-
`ing and laser heating. There is a strong felt need for a solder
`connection between a slider pad and a suspension pad which
`can be made at the slider level with the same integrity as the
`connection made in US. Pat. No. 5,530,604.
`SUMMARY OF THE INVENTION
`
`The present invention is an improvement of the cross-
`referenced US. Patent by overcoming degradation of the
`solder bumps created at the wafer level. This is accom-
`plished by various methods of solder wire bumping at the
`slider or row level. However, the first object of the head
`gimbal assembly is very precise alignment of the load
`applying gimble feature to the centroid of the air bearing
`surface. Therefore, specific tolerance conditions within the
`integrated suspension itself, and the manufacturing tooling
`for attaching the slider to the suspension, cause the suspen-
`sion termination pads to have a misalignment tolerance with
`respect to the slider solder bumps. This misalignment is in
`the plane of the suspension. There can be a further mis-
`alignment of the four solder bumps that is normal to the
`suspension. This is because the solder wire bumping pro-
`cesses also have limitations in the degree of accuracy that all
`the solder bumps can be placed with respect to the slider
`surface to which the suspension is attached. The present
`invention teaches both conventional and new solder wire
`bumping processes that have optimal solder geometries for
`overcoming these limitations and effecting a reliable elec—
`trical joint.
`It further teaches to use these solder bump
`
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`

`

`5,821,494
`
`m
`
`mm
`
`
`
`3
`geometries in combination with integrated suspension
`designs that incorporate planar geometric features in the area
`of the termination pads such that all the suspension pads are
`aligned and in contact, or are in very close proximity to the
`slider solder bumps. In the preferred embodiments, the slider
`with solder bumps is first fixed to the suspension, and then
`electrical interconnection is established by reflowing these
`bumps.
`In one method a solder wire bump is formed on a slider
`
`4
`reconfigure by surface tension to contact a solder bump on
`the suspension pad.
`Afurther object is to provide a method of making a solder
`connection between a slider pad and a suspension pad
`where, upon reflow, a solder bump on the slider pad will
`contact and connect with the suspension pad.
`Still a further object is to provide geometric features in the
`termination pad region of the suspension such that all the
`suspension pads want to be biased in contact, or in very close
`pad WhiCh has {1 tail and the SHSPCHSihn Pad has a flattened 10 proximity to all solder bumps on the slider, where upon laser
`soiliderbuntihp. hflectncalRingrmnnectlUH 1:1 $513235th by
`reflow, all bumps will more reliably interconnect With all
`re owmg
`ese umps.
`e ow is accomp s e
`y a aser
`_.
`_. ) 2
`beam which makes a superior connection. The reliability of
`Sllssliillsiihthejsobject is [0 provide a method of making a
`the solder reflow process can be further enhanced by the
`solder connection betweenaslider ad and asus ension ad
`integrated suspension previously described that has the 15
`.
`p j
`p
`.
`p
`required geometric features to bring the respective slider and
`whdere a solctlerkbump IS fofrmed if $6 cpzlnerof the slidiegpad
`suspension solder bumps into closer physical proximity in
`fl?
`a npn-s 115m Iace Oh a too ’
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`rom
`the pre—refiow condition,
`e too and a act
`to t e suspension w11
`the suspension
`In another method, the slider pad is bumped at an angle
`$15: E23523 giaznflslgetfggflj‘gfilggggd the solder bump 15
`with the tail of the solder bump angling away from the ABS Eh
`.
`.
`.
`.
`i
`.
`while the solder bump on the suspension pad is omitted. The
`Still a further object is to proVIde a method of making a
`angled solder pad on the slider pad is then heated by the laser
`solder connection between a Shder pad and asuspens10n pad
`beam which causes reflow. Again, that portion of the sus—
`Where [he finder lb dmxcd 10 [he bushcnbmn and then d
`pension carrying the termination pads can have geometric
`coilnmodn :older bump ls far??? at 31:”) corriier 0f the shder
`features thatenhance the ability ofthe tails on all four solder 25 pa
`an t e suspension pa
`0 owe
`y re _0W’
`‘
`_
`bumps 10 be in contact 01. close proximity to the suspension
`Other objects and advantages of the .invention. will
`pads in the pre—rellow state.
`become apparent upon reading the following description
`In still another method, the slider is affixed to a tool which
`taken together Wflh the accompanying draWings.
`has a surface to which solder will not stick, The slider pad .
`BRIEF DESCRIPTION OF THE DRAWINGS
`and the surfaces of the tool are then solder bumped by a 30
`FIG. 1 is an isometric schematic illustration of an exem-
`common solder Wire ball to effect a solder bump geometry
`plary diSk drive employing a slider 0f the present invention.
`that is more coliiiear with the suspension attach surface of
`FIG. 2 illustrates a pair of integrated suspensions loading
`thC slider, and Where the bumps CXtCHd further beyond thC
`slider head termination pads at this interface. As in the above A; a pair of sliders on a pair of rotating disks.
`methods, when the slider is affixed to the suspension, the l
`FIG. 3 is a side view of the integrated suspension and the
`511513615:th czfin havefaflgeometric featureithat ”0:13:35 31%”
`slider showing a solder connection between a slider pad and
`norma
`ias orce o
`e suspension pa s agains
`e si er
`-
`solder bumps. The solder bump is then heated by the laser
`a suspension pad.
`.
`.
`.
`.
`,
`Jeam for reflow.
`FIG. 4 is an isometric illustration of solder connections
`,
`,
`,
`40 between slider pads and suspens10n pads.
`In all these methods the slider pad 15 preferably bumped
`FIG 5A is an isometric illustration of rows and columns
`at the slider level and reflow is implemented by a laser be am
`.
`'
`0 provide a superior connection between the slider pad and
`0f Sliders at. the wafer leyel.‘
`.
`.
`suspension pad. It should be understood, however, that in
`FIG 5B 15 an isometric illustration 0f sliders at the row
`another embodiment of this invention, the slider pads may 4‘
`level.
`FIGS. 6A—6D show a series of steps for producing a
`3e bumped at the row level after the air bearing surface has
`36611 created and just prior to dicing into sliders. At this stage
`solder bump with a tail on a slider pad using solder wire.
`he solder bumps are not subject to the aforementioned harsh
`FIG. 7A is a side View of a row of sliders with slider pads.
`
`)rocessing steps.
`
`FIG. 7B is the same as FIG. 7Aexce pt that the slider pads
`
`
`A still further method a
`ixcs the slider to the suspension —
`have solder wire bumps.
`FIG. 8A is a side view of an individual slider at the slider
`JCfOI'C any solder wire bumping. The slider pad and the
`suspension pad are then bumped by a common solder wire
`level with slider pads.
`)all. The common solder wire bump is then heated by the
`FIG. 8B is the same as FIG. 8A except the slider pads have
`aser beam for reflow. This process requires a suspension
`solder wire bumps.
`oadbeam with geometric features such that both the slider
`FIG. 9A is a plurality of sliders mounted on a fixture for
`and the integrated suspension area carrying the termination
`solder bumping.
`3ads can have adequate mechanical support by the bumping
`FIG. 9B is one of the sliders of FIG. 9A after separation
`)rocess tooling, whereas in the previous described processes
`from the fixture with solder bumps on the slider pads.
`no such features are required because essentially no external
`orce is required in the process after the slider is attached to
`FIG. 10A shows a laser beam applying heat to reflow the
`solder bumps after the slider is affixed to the suspension.
`he suspension.
`Fig. 10B shows a right angled fillet joint after reflow
`An object is to overcome the problem of degradation of
`making a solder connection between the slider pad and the
`solder bumps applied at the wafer level in U.S. Pat. No.
`5,530,604.
`suspension pad.
`FIG. 11A shows a side view of the slider wherein the
`Another object is to provide a method of making a solder
`connection between a slider pad and a suspension pad
`slider pad is bumped with a solder ball, the solder ball
`where, upon reflow, a solder bump on the slider pad will
`having a tail which is angled away from the ABS.
`
`60
`
`65
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`

`5,821,494
`
`5
`FIG. 11B shows the solder bump being heated by a laser
`or reflow after the slider is attached to the suspension.
`FIG. 11C shows the right angled fillet joint after reflow
`making a connection between the slider pad and the sus-
`wension pad.
`FIG. 12A shows the slider bonded to the suspension in a
`aosition for receiving solder.
`FIG. 1213 shows a common solder wire ball bumped
`against the slider pad and the suspension pad at an angle and
`Jeing heated by a laser beam for reflow.
`FIG. 12C shows the right angled fillet joint after reflow
`making a connection between the slider pad and the sus-
`)ension pad.
`FIG. 13 is a partial side View of the slider and a cut-away
`aortion of a tool, wherein the slider pad and the surface are
`oumped with a solder bump angled at 90° to the slider pad.
`FIG. 14 is a View taken along plane XIV—XIV of FIG.
`13.
`
`FIG. 15 is similar to FIG. 13 except the solder ball is
`311mped at an angle of 45° to the slider pad, and the tool has
`a non—stick surface that extends far beyond the slider trailing
`edge.
`FIG. 16 is a view taken along plane XV17XVI of FIG.
`15.
`FIG. 17 is a side View of the slider with the solder bump
`)umped at 45° as shown in FIG. 15.
`FIG. 18 shows a side view of the integrated suspension
`with copper and polyimide layers removed at selected
`oeations.
`
`
`
`
`FIG. 19 shows the slider affixed to the suspension with the
`slider pad spring biased against
`the solder ball and heat
`Jeing applied by a laser for reflow.
`FIG. 20 shows the connection of the slider pad to sus-
`)ension pad after reflow.
`FIG. 21A shows only two layers of a first embodiment of
`a three layer laminated suspension wherein the two layers
`are a copper layer on a polyimide layer with the copper layer
`‘ormed into leads.
`
`FIG. 21B shows only the stainless steel support layer of
`he first embodiment of the three layer laminated suspen-
`sion.
`
`FIG. 21C shows all three layers of the first embodiment
`of the laminated suspension with a slider affixed to the
`stainless steel layer of the suspension.
`FIG. 22A shows only two layers of a second embodiment
`of a three layer laminated suspension wherein the two layers
`are a copper layer on a polyimide layer with the copper layer
`formed into leads.
`
`FIG. 22B shows only the stainless steel support layer of
`the second embodiment of the three layer laminated suspen-
`sion.
`
`FIG. 22C shows all three layers of the second embodi—
`ment of the laminated suspension with a slider affixed to the
`stainless steel layer of the suspension.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`Referring now to the drawings wherein like reference
`numerals designate like or similar parts throughout
`the
`several views, there is illustrated in FIG. 1 a disk drive 30.
`The disk drive 30 includes a spindle 32 which supports and
`rotates at least one magnetic disk 34. The spindle 32 is
`rotated by a motor 36 which is governed by motor control
`
`
`
`6
`38. A thin film magnetic head 40 of the present invention is
`mounted on a slider 42, the slider being supported by a
`suspension and actuator arm 44. The suspension and actua—
`tor arm 44 positions the slider 42 so that the head 40 is in a
`transducing relationship with a surface of the magnetic disk
`34. When the disk 34 is rotated by the motor 36, air is moved
`by the surface of the disk, causing an air bearing surface
`(ABS) of the slider to ride on an air bearing slightly off the
`surface of the disk. The head 40 is then employed for writing
`information to multiple circular tracks on the surface of the
`dis( 34, as well as reading information therefrom. These
`information signals, as well as servo signals for moving the
`slicer to various tracks, are processed by drive electronics
`46.
`FIG. 2 shows schematically a pair of the sliders 42 on a
`pair of the disks 34 by a pair of the suspensions 44 when the
`dis<s are rotating. It also shows the loading force of the
`slit ers 42 counterbalanced by an air bearing between air
`bearing surfaces 50 and surfaces 52 of the disks. Solder
`connections 60 interconnect slider pads 62 to suspension
`pacs 64. As shown in FIG. 3 the slider pad 62 is connected
`to a component 66 of the magnetic head by a conductive Via
`68. As shown in FIG. 4 the slider 34 may have four slider
`pacs 62 which are connected to four suspension pads 64 by
`the solder connections 60.
`A first pair of the slider pads may be connected to a coil
`(not shown) in a write head and a second pair of the slider
`pacs may be connected to a magnetoresistive (MR) sensor
`(not shown) of a
`read head. As shown in FIG. 3 the
`suspension may be a laminated or integrated suspension
`which includes an insulative layer, such as a polyimide layer
`70, sandwiched between a steel layer 72 and a copper layer
`74. As shown in FIG. 4 the copper layer is selectively etched
`to provide copper leads 76 which terminate at the suspension
`pads 64 (see FIG. 3). As shown in FIG. 3, the slider 42 is
`aflixed to the suspension 44 by bonding a surface 80,
`opposite the ABS 50,
`to a surface 82 of the integrated
`suspension using an adhesive so that the slider has a leading
`edge 84 with respect to rotation of the disk 34 in the drive.
`In the embodiment shown in FIG. 3 this bonding occurs
`wetween the surface 80 and a copper island on the suspen—
`sion. This copper island may be formed by the same etching
`arocess which forms the copper leads 76. Another arrange—
`ment for affixing the slider to the suspension 44 is shown in
`FIGS. 19, 20, 21 C and 22C, wherein the suspension area
`hat is adhesively attached to the slider, the polyimide and
`copper layer has been removed so that the slider adhesive
`wond is directly to the stainless layer. In this type process, the
`suspension is designed to have the electrical path to the
`ermination pads route around the periphery of the slider as
`shown in FIGS. 21C and 22C. The suspension area that
`contains the pads and the regions leading thereto can incor-
`)orate geometric features to enhance the ability of the
`suspension pads to be biased in contact, or in very close
`m)ximity to the slider solder bumps.
`As shown in FIG. 5A rows and columns of sliders 42 are
`fabricated on a substrate 90 at
`the wafer level. In prior
`oracticc solder bumps were formed on the slider pads 62 at
`he wafer level. This was accomplished by screen printing
`solder paste through a mask on solder pads and then refiow-
`ing the solder paste to produce solder bumps on the slider
`Jads 62. Subsequent to forming solder bumps the wafer 90
`was subjected to a slider fabrication process which consists
`of dicing the wafer into rows, creating the air bearing surface
`and then further dicing the rows to discrete sliders. The
`aforementioned processing steps at the wafer and row levels
`caused oxidation and erosion of the solder bumps on the
`
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`Page 16 of 21
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`

`

`5,821,494
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`7
`invention provides methods of
`slider pads. The present
`forming bumps on the slider pads 62 subsequent to the wafer
`level 90.
`FIGS. 6A—6D schematically illustrate various steps in the
`process of solder bump formation using solder wire. A
`commercially available wire bonder (for example, K & S
`model 4124, Shinkawa model SBB—l)
`is used for this
`purpose. The solder wire of diameter 25 [rm to 50 ,um is
`commercially available from Tanaka Dcnshi Kogyo in
`Japan. A solder wire 104 is inserted through a ceramic
`capillary 102 of suitable diameter as shown in FIG. 6A. A
`solder ball 108 is formed at the bottom of the capillary by an
`arc discharge between an electrode 106 and the wire in
`Ar+4710% hydrogen gas, as shown in FIG. 6B. The ball 108
`is then bonded to the slider pad 62 by pressing the ball
`against the pad with the bottom end 110 of capillary 102, and
`employing ultrasonic power while the slider is heated to
`approximately 140°—150° C., as shown in FIG. 6C. After the
`ball is bonded,
`the capillary is raised, while the wire is
`clamped by a clamp 111 above the capillary and pulled. The
`wire breaks above the neck of the ball, leaving a solder bump
`94 with a tail 100, as shown in FIG. 6D. The cycle is
`repeated with ball formation by are discharge. The slider
`pads may or may not extend all the way to the suspension
`attach surface of the slider. Similarly for a very small slider,
`such as the industry describes as 30%, where the width of the
`slider is on the order of 1.0 mm, the pitch between pad pairs
`is on the order of 110 microns. This limits the maximum
`diameter of the ball and there the distance the solder bump
`can extend beyond the slider pad to accommodate misalign-
`ment of the suspension pads in this direction. All these steps
`are carried out automatically in commercial wire bonders
`with bumping capabilities.
`FIGS. 5B and 7A show the sliders 42 at the row level 92
`before the slider pads 62 are solder bumped. FIG. 7B shows
`the sliders 42 after solder bump 94 formation on the slider
`pads 62. The row of sliders 92 can then be diced to provide
`individual sliders at a slider level 96 as shown in FIG. 8B.
`In the preferred embodiment the sliders 42 are diced into
`individual sliders at the slider level 96 as shown in FIG. 8A.
`Solder bumps 94 are then fonned on the slider pads 62 using
`solder wire bumping as shown in FIG. 8B. Alternatively, the
`sliders 42 at the slider level 96 may be affixed to a fixture 98
`where the slider pads 62 may be solder bumped to provide
`bumps 94. The sliders 42 are then released from the fixture
`to provide a released slider as shown in FIG. 9B.
`From FIG. 6D it should be noted that the tail 100 extends
`substantially perpendicular to a flat surface of the slider pad
`62. The solder wire bumping shown in FIG. 6D is at 90° to
`the surface of the slider pad 62 which is considered normal
`practice. If the slider pad is presented at an angle to the
`capillary other than 90° this is called angular bumping which
`is at some angle to the perpendicular. This process can create
`a solder bump tail or solder bump top surface that extends
`further beyond the trailing edge of the slider to better
`accommodate misalignment of the suspension pad to the
`solder bump in this direction which is typically on the order
`of :30 microns to :40 microns.
`A flat solder bump 116 on the suspension pad 64, as
`shoan in FIG. 10A, can be produced easily and economi—
`cally by either screenprinting solder paste through a mask,
`rellowing the solder and flattening by a die, or by a selective
`solder plating process. Such a flat bump can also be pro-
`duced from solder wire bumping and flattening the tail by
`mechanical means.
`In FIG. 10A the slider 42 is affixed to the suspension 44
`as described hereinabove. This affixing positions the tail 100
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`over and adjacent the flattened solder bump 116. Upon
`reflow the flattened solder bump 116 has an expected
`reconfiguration due to surface tension which will form a
`substantially spherical shape as shown by the phantom line
`at 118. The tail 100 projects within this expected expansion
`which will cause the solder bumps 94 and 116 to effectively
`unite and cause an eflicient reflow therebetween. As shown
`in FIG. 10A the solder bumps 94 and 116 are reflowed by the
`laser beam under an inert gas atmosphere like nitrogen gas
`which produces the solder connection 60 between the slider
`pad 62 to the suspension pad 64, as shown in FIG. 10B.
`Another embodiment of the invention is illustrated in
`FIGS. 11A—11C. In FIG. 11Athe slider pad 62 is solder wire
`bumped at an angle to produce a solder bump [20 which has
`a tail 100 which is directed at an angle away from the ABS
`50 instead of being parallel thereto as shown in FIG. 6D. The
`same tool described hereinabove can be employed for pro-
`ducing the solder bump 120. Essentially the steps shown in
`FIG. 6A—6D will be employed except the capillary tube is
`directed at an angle from a normal to the slider pad 62. When
`the slider 42 is affixed to the suspension 44, as shown in FIG.
`11B, the tail 100 is directed downwardly toward the sus-
`pension pad 64. The tail length is controlled so that the tail
`is in contact with slider pad 62 on assembly. Upon heating
`by a laser beam under an inert gas atmosphere, like nitrogen,
`the solder bump 120 is reflowed to produce the solder
`connection 60 between the slider pad 62 and the suspension
`pad 64 as shown in FIG. llC.
`FlGS. 13720 illustrate another embodiment of the present
`invention. As shown in FIGS. 15 and 16 the slider 42 is
`affixed to a tool 124 which has a surface 126 which will not
`stick to solder. The tool 124 may be made of glass or some
`other ceramic.
`In FIGS. 13 and 14 the slider pad 62 is
`bumped at 90° with a solder bump 130. The solder bump 130
`may be constructed with the aforementioned tool. FIGS. 15
`and 16 are similar to FIGS. 13 and 14 except the slider pad
`62 has been bumped with a solder bump 132 which is
`implemented by angled bumping. The angled bumping is
`Jreferred over the 90° bumping shown in FIGS. 13 and 14.
`A preferred angle is in the range of 45° to 60° to either of
`he flat surfaces of the slider pad 62 or the surface 126 of the
`001. It should be noted that in practice the tool 124 with the
`slider 42 in FIGS. 13 and 15 will be angled at the desired
`angle for bumping with the wire bumping being directed
`vertically downward by the aforementioned solder wire
`)umping tool.
`FIG. 17 shows the slider 42 after removal from the tool
`124 leaving the angled solder ball 132 with a flattened
`wortion 134. FIG. 18 shows the suspension 44 with selected
`aortions 0f the copper layer 74 and the polyimide layer
`removed. As shown in FIG. 19 the slider 42 is connected to
`he suspension 44 by bonding the slider surface 82 to a
`aortion of a surface 86 of the steel layer 72 instead of the
`copper island shown in FIG. 4. This is accomplished by
`removing portions of the polyimide layer 70 and the copper
`layer 74 between the suspension pad 64 and a location
`spaced from a leading edge 84 of the slider toward an
`actuator (not shown) to the