Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/0277—Bendability or stretchability details
  • H05K1/028—Bending or folding regions of flexible printed circuits
  • H05K1/0281—Reinforcement details thereof
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
  • G11B5/4806—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed specially adapted for disk drive assemblies, e.g. assembly prior to operation, hard or flexible disk drives
  • G11B5/484—Integrated arm assemblies, e.g. formed by material deposition or by etching from single piece of metal or by lamination of materials forming a single arm/suspension/head unit
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
  • G11B5/4806—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed specially adapted for disk drive assemblies, e.g. assembly prior to operation, hard or flexible disk drives
  • G11B5/4826—Mounting, aligning or attachment of the transducer head relative to the arm assembly, e.g. slider holding members, gimbals, adhesive
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/03—Use of materials for the substrate
  • H05K1/05—Insulated conductive substrates, e.g. insulated metal substrate
  • H05K1/056—Insulated conductive substrates, e.g. insulated metal substrate the metal substrate being covered by an organic insulating layer
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/03—Conductive materials
  • H05K2201/0332—Structure of the conductor
  • H05K2201/0335—Layered conductors or foils
  • H05K2201/0338—Layered conductor, e.g. layered metal substrate, layered finish layer or layered thin film adhesion layer
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/03—Conductive materials
  • H05K2201/0332—Structure of the conductor
  • H05K2201/0335—Layered conductors or foils
  • H05K2201/0352—Differences between the conductors of different layers of a multilayer
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/09—Shape and layout
  • H05K2201/09209—Shape and layout details of conductors
  • H05K2201/09654—Shape and layout details of conductors covering at least two types of conductors provided for in H05K2201/09218 - H05K2201/095
  • H05K2201/09736—Varying thickness of a single conductor; Conductors in the same plane having different thicknesses
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/20—Details of printed circuits not provided for in H05K2201/01 - H05K2201/10
  • H05K2201/2009—Reinforced areas, e.g. for a specific part of a flexible printed circuit
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
  • H05K3/108—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern by semi-additive methods; masks therefor
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/22—Secondary treatment of printed circuits
  • H05K3/24—Reinforcing the conductive pattern
  • H05K3/243—Reinforcing the conductive pattern characterised by selective plating, e.g. for finish plating of pads

Definitions

• the invention disclosed herein relates generally to hard disk drive suspensions. More specifically, the invention relates to hard disk drive suspension assemblies and circuit assemblies with an integral flexible circuit and integral support member.
• Suspension assemblies in hard disk drives include a head gimbal assembly (HGA).
• the HGA includes a gimbal assembly, a head assembly, and an interconnect assembly.
• the head assembly includes a highly sensitive read/write transducer, commonly referred to as a head, attached to an air bearing slider.
• the head assembly also includes electrical terminals configured for interconnection to the interconnect assembly for receiving and relaying data signals.
• the head assembly facilitates reading and writing of information on a surface of a rotating magnetic disk.
• the interconnect assembly includes a plurality of transmission elements, such as wires or traces, for transmitting data to and from the head assembly.
• the suspension assembly positions the head assembly at a generally constant distance away from the moving surface of the rotating disk.
• the suspension assembly permits the head assembly to "fly" at a height above the surface of the disk, including surface irregularities.
• Most conventional suspension assemblies also referred to herein as a support member, include a load beam and a gimbal portion.
• the load beam is a resilient spring plate designed to provide lateral stiffness.
• the load beam is calibrated to apply a force on the head assembly that counteracts a lift force on the head that is provided by the air stream generated by the rotating disk. Accordingly, the head assembly flies above the surface of the disk at a height established by the equilibrium of the load beam force and the lift force.
• the gimbal portion is positioned adjacent to an end of the load beam and has the head assembly attached thereto.
• the gimbal portion permits roll and pitch deflections of the head assembly in response to flying over surface imperfections and warping of the rotating disk. By permitting these deflections, the gimbal portion aids in maintaining the proper orientation and distance of the head assembly relative to the rotating disk, even when the load beam exhibits a slight amount of flexing and twisting.
• the suspension assembly can be attached at its proximal end to a rigid arm or directly to a linear or rotary motion actuator.
• the actuator rapidly moves and then abruptly stops the HGA over any position on a radius of the disk.
• the radial HGA movement and the rotation of the disk allow the head to quickly reach every location above the disk.
• the rapid stop and go movement causes very high stresses on the HGA.
• An ideal HGA comprises components low in mass. Excessive inertial momentum caused by excessive mass can cause overshoot errors. Overshoot errors occur when momentum carries the whole HGA past the intended stopping point during positioning movement. Low-in-mass HGA's are easier to move, resulting in power savings in multiple platter disk drives. Furthermore, lighter weight HGA's permit the head to be flown closer to the surface of the disk. The closer the head assembly can fly to the surface of the disk, the more densely information can be stored on the disk. Accordingly, a lightweight HGA is desirable in high performance disk drives.
• a suspension assembly has signal traces that are etched from a stainless steel based material and an insulating layer is subsequently formed over the signal traces.
• the stainless steel base material is also etched to form the load beam portion and head gimbal portion of the suspension.
• a key limitation of this type of construction is excessive yield rates due to the integrated fabrication process and poor conductivity of stainless steel.
• a conventional flex circuit is attached to a separately fabricated suspension assembly using an adhesive. A key drawback with this type of construction is the cost associated with the precision required for assembling the flexible circuit to the suspension assembly.
• the suspension assembly should be free of unpredictable loads and biases which alter the exact positioning of the head assembly.
• the suspension assembly should respond instantaneously to variations in the surface topology of a disk. Alterations to the flying height of the head can significantly affect data density and accuracy and even destroy data stored on the disk if the head collides with the surface of the disk.
• the rigidity and stiffness of a load beam increase in relation to the cross- sectional thickness by the third power.
• suspension assemblies are very thin and flexible, especially around a sensitive spring portion of the load beam.
• Interconnect assembly conductors have a large effect on the performance of the suspension assembly.
• Conductor stiffness alone greatly affects the rigidity of the spring regions and flight performance.
• a standard wire conductor attached atop the suspension can more than double the stiffness of a load beam and significantly limit the ability of the load beam to adjust to variations in the surface of the disk, vibrations, and movement. The effect of the conductors on a gimbal region, the thinnest and most delicate spring in the suspension assembly, is even more pronounced.
• flexible circuit interconnect assemblies may inadvertently impart unbalanced or excessive forces on the suspension.
• Many common flexible circuit case substrates are also hydroscopic, resulting in flexural characteristics that are dependent on moisture content and humidity. Because the flexible circuits are formed separately from the suspension and subsequently attached, precision manufacturing tolerances are difficult and costly to maintain.
• a circuit assembly includes a base member and a plurality of traces formed directly on a first surface of the base member.
• the traces extend between a first end and a second end of the base member.
• a reference voltage member is formed directly on a second surface of the base member.
• the plurality of traces is positioned to overlay at least a portion of the reference voltage member.
• a support member is formed directly on at least a portion of the reference voltage member.
• the support member is formed from a material exhibiting a tensile strength substantially greater than the tensile strength exhibited by the reference voltage member and the traces.
• a preferred material for the support member is a nickel alloy such as, nickel boron or nickel-phosphorus or any suitable plateable material.
• a preferred material for the traces is copper, gold, palladium, tin, or any suitable plateable.
• the traces and the reference voltage member are formed of the same material.
• the support member is preferably formed directly on the reference voltage member using an electroless plating process.
• the electroless plating process is preferably an autocatalytic electroless plating process.
• the use of an electroless plating process contributes to providing a support member with uniform thickness and allows the support member to be made from a preferred selection of materials.
• the support member may be formed to have regions of different thickness as well as regions that are completely isolated from adjacent regions thereof.
• a load beam portion of the support member preferably has a thickness substantially greater than a gimbal portion thereof.
• the load beam portion of the support member may include spaced-apart flange portions having a main portion extending therebetween.
• the flange portion of the support member has a thickness substantially greater than the main portion of the support member.
• Circuit assemblies and suspension assemblies according to the present invention exhibit an impedance value of less than about 200 ohms between any two traces.
• a process for making a circuit assembly includes the steps of forming a plurality of traces directly on a first surface of a base member, wherein the traces extend between a first end and a second end of the base member; forming a reference voltage layer directly on a second surface of the base member, wherein the plurality of traces overlay at least a portion of the reference voltage layer; and forming a support member directly on at least a portion of the reference voltage layer.
• a disk drive suspension assembly includes an elongated polymeric base member having a plurality of traces formed directly on a first surface thereof and a reference voltage member formed on a second surface thereof.
• a support member is formed directly on at least a portion of the reference voltage member.
• the plurality of traces overlay at least a portion of the reference voltage member.
• the reference voltage member is formed from a first electrically conductive material and the support member is formed from a second electrically conductive material.
• the first electrically conductive material provides substantially greater electrical conductivity and substantially lower tensile strength than the second electrically conductive material.
• the support member includes a head gimbal portion having a first thickness and a load beam portion having a second thickness. The second thickness is substantially greater than the first thickness.
• electroless deposition refers to processes in which a layer of material is deposited onto a non-conductive substrate.
• electroless plating refers to processes in which conductive features on a substrate are plated without being subjected to an externally applied current or voltage.
• HGA head suspension assembly
• suspension assembly refers to a structure including a load beam portion and a head gimbal portion.
• load beam refers to a portion of the suspension assembly that provides a flexural-induced loading relative to a longitudinal axis thereof and that exhibits negligible torsional deflection relative to the longitudinal axis.
• the term “gimbal portion” refers to a portion of the suspension assembly that permits pitch and roll movement of the slider.
• support member refers to a structural member including the load beam and optionally including a gimbal portion.
• sliding and “head” are used interchangeably herein and refer to a unit for reading and writing information in a magnetic format, optical format or other type of data storage format.
• reference voltage layer refers to a layer of electrically conductive material that is spaced away from an adjacent electrical feature by a uniform distance.
• Figure 1 is a perspective view illustrating an embodiment of a disk drive suspension assembly.
• Figure 2 is a perspective view illustrating a head gimbal portion of the disk drive suspension assembly of Figure 1.
• Figure 3 is a different perspective view of the head gimbal portion of Figure 2.
• Figure 4A is a cross-sectional view taken along the line 4A-4A in Figure 1.
• Figure 4B is a cross-sectional view taken along the line 4B-4B in Figure 1.
• Figure 5 is a perspective view illustrating a disk drive circuit assembly for use with a conventional disk drive load beam.
• Figure 6 is a cross-sectional view taken along the line 6-6 in Figure 5.
• Figures 7 A-7N and 7P are serial views illustrating an embodiment of a step- by-step process for fabricating a suspension assembly and a circuit assembly according to the present invention.
• the ' suspension assembly 10 includes a load beam portion 12 having a first end 12a and a second end 12b.
• a gimbal portion 14 is attached to the first end 12a of the load beam portion 12.
• the gimbal portion 14 has a head assembly 16 mounted thereon.
• a plurality of traces 18 is attached to the load beam portion 12.
• the traces 18 extend between the first end 12a and the second end 12b of the load beam portion 12.
• a first end 18a, Figure 2, of each one of the traces 18 is electrically connected to corresponding terminals (not shown) of the head assembly 16.
• each one of the traces 18 extends from the second end 12b of the load beam portion 12.
• Each one of the traces 18 includes a corresponding lead 22 for being electrically connected to a related component of a hard disk drive.
• a portion of each one of the traces 18 is covered with a protective layer 20, Figures 1, 2, 4 A and 4B, such as a non-conductive photoimageable covercoat material.
• a protective layer 20 such as a non-conductive photoimageable covercoat material.
• suitable photoimageable covercoat materials include epoxy acrylate formulations offered by Taiyo under the PSR4000 series and by Nippon Polytech under the NPR80 series; and polyimide formulations offered by Arch Chemicals under the Probimide series and by DuPont under the Pyralin Series.
• An example of a suitable screen printable covercoat material for the protective layer 20 includes an epoxy formulation offered by Ashai Chemicals under the part number CCR232.
• the protective layer 20 reduces the potential for corrosion of the underlying portions of the traces 18. As is commonly practiced in art of circuit- making, the portions of the traces 18 that are not covered by the protective layer 20 typically have a coverplate layer (not shown) of corrosion-resistant material such as gold or palladium formed thereon.
• the load beam portion 12 includes a base member 24.
• the traces 18 are mounted directly on a first side of the base member 24.
• the traces 18 as well as other types of conductive features are formed from a conductive feature layer formed on the base member 24.
• a reference voltage member 26 is mounted directly on a second side of the base member 24.
• the traces 18 and the reference voltage member 26 are preferably mounted directly on the respective first and second sides of the base member 24.
• an attachment layer such as a layer of adhesive is not used between the base member 24 and the traces 18 or the reference voltage member 26.
• a support member 28 is mounted on a surface of the reference voltage member 26 opposite the second side of the base member 24.
• the support member 28 includes a main portion 28a having spaced apart flange members 28b extending therefrom.
• the flange members have a thickness 28b' that is substantially greater than a thickness 28a' of the main portion 28a.
• the base member 24 is typically a flexible polymeric substrate having a thickness of from about 0.25 mils (6-7 microns) to about 3.0 mils (75 micons). The specific application and design of the suspension assembly 10 will dictate the required thickness of the base member 24.
• Suitable materials for the base member 24 include a polyimide film such as that sold by DuPont under the tradename KAPTON E.
• Other types of commercially available flexible polymeric films, such as, for example, films made of polyester and polypropylene, may also be useful as materials for the base member 24.
• the conductive traces 18 and the reference voltage member 26 are preferably made of a conductive material such as copper. Preferred materials for the conductive traces 18 and the reference voltage member 26 have a tensile strength of less than about 4218 kg/cm and a resistance of less than about 1.7 ⁇ /cm at room temperature.
• the conductive traces 18 and the reference voltage member 26 may include a plurality of layers of the conductive material. For example, a first layer of copper may be formed on the base member 24 using a deposition method, such as sputtering, and a second layer of copper may be formed on the first layer of copper using a plating process, such as electroplating or electroless plating.
• the overall thickness of the conductive traces 18 and the reference voltage member 26 is typically from about 50 micro inches to about 1000 micro inches.
• the specific application and design of the suspension assembly 10 will dictate the required thickness of the conductive traces 18 and the reference voltage member 26.
• the support member 28 is preferably made of a material having mechanical properties superior to the material of the traces 18 and reference voltage member 26.
• the mechanical properties of the support member 28 dominate the resulting overall stiffness of the load beam portion 12 of the suspension assembly 10.
• the typical thickness of main portion 28a of the support member 28 is from about 0.1 mils to about 1.5 mils.
• the support member 28 may include one or more flanged portions that are substantially thicker than the main portion thereof.
• Preferred materials for the support member 28 include nickel-based alloys, such as nickel-phosphorus alloys and nickel-boron alloys. Preferred nickel-based alloys have a tensile strength of greater than about 6327 kg/cm 2 .
• support members 28 according to the present invention are made of plateable materials such as nickel based alloys. In addition to being plateable, nickel-based alloys have material characteristics very similar to stainless steel.
• the configuration and construction of the reference voltage member 26 relative to the traces 18 provide a highly controlled impedance level.
• the material that the reference voltage member 26 is made from has significantly higher electrical conductivity than that of the materials from which the support member 12 and conventional load beams are made.
• the traces 18 and the reference voltage member 26 are formed directly on the respective first and second surfaces of the base member 24, the distance between the reference voltage member 26 and the traces 18 is more uniform when compared to previous types of constructions.
• the second end 18b of the traces 18 that extend from the second end 12b of the load beam 12 are carried on the first side of the base member 24.
• the reference voltage member 26 is carried on the second side of the base member 24.
• the protective layer 20 is formed over the traces 18. It is desirable that the traces 18 extending from the second end 12b of the load beam 12 exhibit a minimal degree of stiffness. Accordingly, the support member 28 does not extend past the second end 12b of the load beam 12.
• circuit assembly 110 is made according to processes of the present invention.
• the circuit assembly 110 is mounted on a conventional load beam (not shown) for providing electrical interconnection between a head assembly 116 and the associated electrical components of a hard disk drive (not shown).
• the circuit assembly 110 includes a gimbal portion 114 for providing gimballing functional.
• the circuit assembly 110 may optionally include a support member 128 for providing a suitable degree of stiffness.
• the circuit assembly 110 includes a base member 124.
• a plurality of traces 118 are formed directly on a first side of the base member 124 and a reference voltage member 126 is formed directly on a second side of the base member 124.
• a protective layer 120 is formed over the traces 118.
• the support member 128 is formed directly on the reference voltage member 126.
• a process for making suspension assemblies and circuit assemblies according to the present invention is illustrated in Figures 7A-7N and IV.
• a first side 200a and a second side 200b of a base substrate 200 are metallized using a known deposition process, such as electroless, sputtering or chemical vapor deposition, with a first conductive layer 202, commonly referred to as a seed layer, Figure 7A.
• the base substrate 200 is preferably a flexible polymeric film such as polyimide.
• the first conductive layer 202 has a thickness of between about 200 angstroms and about 2000 angstroms and is made from a highly conductive material such as copper.
• the first conductive layer 202 provides a continuous conductive layer to facilitate deposition of a second conductive 204, Figure 7B.
• the second conductive layer 204 commonly referred to as a flash plated layer, is also made of a highly conductive material such as copper.
• the first and second conductive layers 202, 204 on the first side 200a of the base substrate 200 jointly define a conductive feature base layer 207, Figure 7B.
• the first and second conductive layers 202, 204 on the second side 200b of the base substrate 200 jointly define a reference voltage layer 209.
• the second conductive layer 204 is deposited using a known plating process, including processes such as electroless plating or electroplating techniques.
• a preferred method is electroplating and a typical plated thickness of the second conductive layer 204 is between about 50 micro inches and about 1000 micro inches.
• copper is electroplated from a copper sulfate & sulfuric acid plating solution.
• the plating current density is maintained between about 10 and about 60 amps per square foot.
• an etching process is performed thereon to prepare the surfaces thereof for application of a photoresist.
• Typical etching solutions for copper include, but are not limited to, ammonium, sodium persulfate and hydrogen peroxide sulfuric.
• a photoresist layer 206 is then applied to the conductive feature base layer 207 and to the reference voltage layer 209, Figure 7C.
• the photoresist layer 206 is an aqueous processible, dry-film, positive-acting photoresist applied using heat and pressure.
• the thickness of the photoresist 206 is typically between about 15 micrometers and about 50 micrometers.
• Suitable photoresists for the photoresist layer 206 include, for example, photoresists offered by MacDermid Incorporated under the series designations SF, CF, and MP. Specific examples include MacDermid SF310 and MP413 photoresists.
• suitable photomasks 208 are engaged against the photoresist layers 206 and the photoresist layers 206 are then exposed to energy from a suitable source for exposing a desired image in the photoresist layer 206, Figure 7D.
• An ultraviolet light source is commonly used for exposing images in photoimageable photoresists, such as those photoresist materials identified above.
• the photomasks 208 include patterned chrome or emulsion coated portions for preventing the transmission of energy to specific areas of the photoresist layer 206, allowing energy to pass through and react with the photoresist layer 206 in unblocked areas. Photomasks of various constructions are commercially available.
• the developing step includes applying a dilute aqueous solution, such as a 0.5% - 1.5% sodium or potassium carbonate solution, to the photoresist until the desired patterns are obtained in the layers of photoresist layers 206.
• the developing step is typically performed using commercially available equipment and solutions.
• a protective layer 210 is applied over the developed photoresist layer 206 on the reference voltage layer 209.
• a suitable protective layer 210 is a polymeric sheet held in place by a layer of commercially available, releasable adhesive. The polymeric sheet and adhesive are selected from materials that are resistant to the plating chemistry.
• exposed portions of the conductive feature base layer 207 are plated, Figure 7F, to produce a plurality of conductive features 211 such as traces, bonding pads, capture pads, test pads, etc.
• Suitable plating methods include the same method used to plate the second conductive layer 204.
• a preferred method for plating is electroplating and a preferred material is copper.
• the thickness of the conductive features 211 is typically between about 0.2 mils and about 2.0 mils.
• Typical etching solutions for copper include, but are not limited to, ammonium, sodium persulfate and hydrogen peroxide sulfuric.
• a support member layer 220 is formed on the reference voltage layer 209.
• the support member layer 220 is formed on the reference voltage layer 209 using a suitable plating process.
• a preferred plating process is an electroless, preferably autocatalytic, plating process. Specific information relating to electroless autocatalytic plating is provided in ASTM B374.
• Preferred plating materials include nickel-based alloys such as a nickel-phosphorus alloy having a phosphorus content of from about 5% to about 15% and a nickel-boron alloy having a boron content of from about 0.3% to about 10%.
• a typical electroless autocatalytic plating process includes exposing the reference voltage layer 209 to a plating bath comprising a nickel-phosphorus alloy solution maintained at a temperature of between about 76.7°C and 93.3°C and having a pH level of between about 4.2 and about 6.2.
• the nickel concentration is maintained between .05 and 1 oz/gal of nickel concentration.
• the phosphorous is include with a reducing agent and deposits in the plated metal at a rate of 5.0 to 7.0 wgt%.
• the photoresist layers 206 and 213 are removed using the previously mentioned photoresist stripping method. Then, the portions of the conductive feature base layer 207 and reference voltage layer 209 that were concealed under the corresponding photoresist layer are removed using a suitable etching process, such as the etching processes described above. By etching previously concealed portions of the conductive feature base layer 207 and reference voltage layer 209, the conductive features become electrically isolated from each other.
• a suspension assembly or a circuit assembly may require additional torsional rigidity or apertures extending through the base substrate 200.
• Figures 7J-7N & 7P illustrate suitable process steps for adding additional thickness to selected portion of the support member layer 220 and for forming apertures through the base substrate 200.
• a photoresist layer 222 is formed over the conductive features 211 and the support member layer 220.
• the photoresist layer 222 is made from the same material as the photoresist layer 206, described above in reference to Figure 7C.
• the photoresist layer 222 is exposed and developed using the same exposure and develop methods described above in reference to Figures 7D and 7E.
• the photoresist layer 222 adjacent to the conductive features 211 is flood exposed such that it remains in its entirety after the developing step.
• the photoresist layer 222 adjacent to the support member layer 220 is exposed through a photomask 224 that includes energy blocking portions 224a that are aligned with the support members 220.
• the energy blocking portions 224a are configured such that after exposure and developing of the corresponding photoresist layer 222, the remaining exposed portions of the photoresist layer 222 cover only a portion of the support member layer 220, Figure 7L.
• the support member layer 220 is subjected to an additional plating process.
• the additional plating process produces raised portions 220a formed on the previously plated portions of the support member layer 220.
• the plating process of Figure 7M is preferably the same plating process as described above in reference to Figure 7H.
• Figure 7N the photoresist layers 222 are removed.
• apertures 226 through the base substrate 200, Figure 7N, are formed therein using a variety of different methods. Suitable methods for forming include mechanical punching, laser ablation, laser drilling, and chemical milling.
• the base substrate 200 is a polyimide film and the apertures 226 are formed using a suitable chemical milling process.
• the chemical milling process includes exposing the polyimide base substrate 200 to a concentrated base solution such as potassium hydroxide (KOH) at a temperature of from about 50°C to about 120°C. In doing so, portions of the base substrate 200 exposed to the base solution are etched, producing the apertures 226.
• KOH potassium hydroxide
• a coverplate layer 228 is formed on the conductive features 211 to provide enhanced performance characteristics such as corrosion resistance and bond strength.
• Suitable materials for the coverplate layer 228 include gold, palladium, tin and nickel.
• a hard disk drive suspension assembly according to the present invention improves control of the suspension stiffness in three ways.
• First, the thickness of a plated suspension is much less than current suspensions. Conventional suspensions having a stainless steel support member start to reach a minimum thickness limit at approximately 1 mil to about 0.5 mil using current rolling and stamping techniques.
• the thickness of support members according to the present invention can be tailored to achieve a number of specific design requirements, such as by controlling the dwell time of the assembly in the plating bath.
• Third, regional stiffness of the support member can be tailored through the specific plating process.
• Improved head fly characteristics are achieved through greater design freedom in attaining precise regional stiffness and torsion characteristics.
• Conventional load beams are formed from a continuous piece of stainless steel material. This type of construction does not permit isolated islands or multiple material thickness.
• the base member allows the support member to include islands.
• This additional design characteristic allows the overall and regional stiffness and torsional characteristics of the suspension assemblies to be tailored.
• the ability to precisely control the torsion and stiffness characteristics of a suspension assembly is essential. Such control allows the head to respond faster and in a more controlled manner to changes in the surface profile of the disk. By improving this control, the head assembly can be positioned closer to the disk without increasing the potential of the head contacting the disk.
• suspension assemblies By flying the head assembly closer to the disk, the quantity of information stored on a disk can be increased.
• Many conventional suspension assemblies include a separately fabricated flexible circuit that is attached to a load beam using an adhesive such as an epoxy. This type of fabrication technique is currently done by hand. Accordingly, it is labor intensive and susceptible to significant process variations. Suspension assemblies according to the present invention significantly reduce fabrication time and process variation.
• Suspension assemblies and circuit assemblies according to the present invention also exhibit improved manufacturability.
• the reference voltage layer and conductive feature layer increase the stability of the web during processing, making the web easier to process.
• the thickness of the support member can be reduced over conventional suspension assemblies, the thickness of the polymeric base substrate can be optimized for processing.
• Suspension assemblies according to the present invention have a construction that counteracts coefficient of thermal expansion (CTE) mismatches, reducing stress-induced curling. As the data transmission rates in hard drives increase, suspension assemblies and related circuit assemblies will need to provide highly controlled impedance characteristics. Current suspension assemblies provide only limited impedance control due to significant variability in the distance between the traces and reference voltage member.
• CTE coefficient of thermal expansion
• the reference voltage layer and the traces directly on the base substrate By forming the reference voltage layer and the traces directly on the base substrate in the present invention, the spacing between the traces and the reference voltage layer is precisely controlled. Also, in preferred embodiments according to the present invention, the reference voltage layer is made from a highly conductive material and the support member is made from a material providing essential mechanical properties. These design characteristics significantly improve the impedance performance of suspension assemblies and circuit assemblies according to the present invention. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the embodiments and descriptions disclosed herein.

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• 2000
  • 2000-05-09 US US09/567,783 patent/US6480359B1/en not_active Expired - Fee Related
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• 2002
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