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WO2002067017A2 - Module de dispositifs optiques et procede de fabrication - Google Patents

Module de dispositifs optiques et procede de fabrication Download PDF

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Publication number
WO2002067017A2
WO2002067017A2 PCT/US2002/001822 US0201822W WO02067017A2 WO 2002067017 A2 WO2002067017 A2 WO 2002067017A2 US 0201822 W US0201822 W US 0201822W WO 02067017 A2 WO02067017 A2 WO 02067017A2
Authority
WO
WIPO (PCT)
Prior art keywords
optical device
adhesive
cover
contact
hard particles
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2002/001822
Other languages
English (en)
Other versions
WO2002067017A3 (fr
Inventor
Michael Kober
Michael E. Wernle
Herbert J. Neuhaus
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NanoPierce Technologies Inc
Original Assignee
NanoPierce Technologies Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by NanoPierce Technologies Inc filed Critical NanoPierce Technologies Inc
Priority to AU2002253875A priority Critical patent/AU2002253875A1/en
Publication of WO2002067017A2 publication Critical patent/WO2002067017A2/fr
Publication of WO2002067017A3 publication Critical patent/WO2002067017A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/93—Interconnections
    • H10F77/933—Interconnections for devices having potential barriers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
    • G02B6/4228—Passive alignment, i.e. without a detection of the degree of coupling or the position of the elements
    • G02B6/4232—Passive alignment, i.e. without a detection of the degree of coupling or the position of the elements using the surface tension of fluid solder to align the elements, e.g. solder bump techniques
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
    • G02B6/4236—Fixing or mounting methods of the aligned elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4249—Packages, e.g. shape, construction, internal or external details comprising arrays of active devices and fibres
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/26—Layer connectors, e.g. plate connectors, solder or adhesive layers; Manufacturing methods related thereto
    • H01L2224/31—Structure, shape, material or disposition of the layer connectors after the connecting process
    • H01L2224/32—Structure, shape, material or disposition of the layer connectors after the connecting process of an individual layer connector
    • H01L2224/321—Disposition
    • H01L2224/32151—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/32221—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/32225—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation
    • H—ELECTRICITY
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    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
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    • H01L2224/4805—Shape
    • H01L2224/4809—Loop shape
    • H01L2224/48091—Arched
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    • H01—ELECTRIC ELEMENTS
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    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/481—Disposition
    • H01L2224/48151—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/48221—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/48225—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation
    • H01L2224/48227—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation connecting the wire to a bond pad of the item
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/484—Connecting portions
    • H01L2224/48463—Connecting portions the connecting portion on the bonding area of the semiconductor or solid-state body being a ball bond
    • H01L2224/48465—Connecting portions the connecting portion on the bonding area of the semiconductor or solid-state body being a ball bond the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/73—Means for bonding being of different types provided for in two or more of groups H01L2224/10, H01L2224/18, H01L2224/26, H01L2224/34, H01L2224/42, H01L2224/50, H01L2224/63, H01L2224/71
    • H01L2224/732—Location after the connecting process
    • H01L2224/73251—Location after the connecting process on different surfaces
    • H01L2224/73265—Layer and wire connectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/91—Methods for connecting semiconductor or solid state bodies including different methods provided for in two or more of groups H01L2224/80 - H01L2224/90
    • H01L2224/92—Specific sequence of method steps
    • H01L2224/922—Connecting different surfaces of the semiconductor or solid-state body with connectors of different types
    • H01L2224/9222—Sequential connecting processes
    • H01L2224/92242—Sequential connecting processes the first connecting process involving a layer connector
    • H01L2224/92247—Sequential connecting processes the first connecting process involving a layer connector the second connecting process involving a wire connector
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01004—Beryllium [Be]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
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    • H01L2924/01—Chemical elements
    • H01L2924/01012—Magnesium [Mg]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01019—Potassium [K]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/0102—Calcium [Ca]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01037—Rubidium [Rb]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H01L2924/01046—Palladium [Pd]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H01L2924/01055—Cesium [Cs]
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    • H01L2924/01078—Platinum [Pt]
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    • H01L2924/01079—Gold [Au]
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    • H01L2924/013—Alloys
    • H01L2924/0132—Binary Alloys
    • H01L2924/01322—Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/013—Alloys
    • H01L2924/0132—Binary Alloys
    • H01L2924/01327—Intermediate phases, i.e. intermetallics compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/10—Details of semiconductor or other solid state devices to be connected
    • H01L2924/11—Device type
    • H01L2924/12—Passive devices, e.g. 2 terminal devices
    • H01L2924/1204—Optical Diode
    • H01L2924/12041—LED
    • 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
    • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
    • H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
    • H05K3/321—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by conductive adhesives

Definitions

  • This invention relates, generally, to optical device modules and, more particularly, to illuminating device array modules, such as light-emitting-diode (LED) array modules and optical sensor modules, such as photosensor modules, and to methods for fabricating optical device modules.
  • illuminating device array modules such as light-emitting-diode (LED) array modules
  • optical sensor modules such as photosensor modules
  • incandescent bulbs Because of the relatively short lifetime of incandescent bulbs, these bulbs must be frequently replaced in illuminating devices and displays in continuous operation. In addition to cost considerations, frequent replacement of incandescent bulbs and optical sensors can be difficult where the device module is located in a remote location, for example, at ceiling level in large rooms and in elevated display panels.
  • LEDs light-emitting diodes
  • LEDs can be used as a replacement for incandescent lightbulbs. Because the LEDs do not "burn out," these devices offer significant advantages in improved reliability and reduced maintenance cost. In addition, LED arrays use less power, which reduces operating costs in comparison to illuminating devices containing incandescent lightbulbs.
  • a typical LED array can range in size from about 300 microns x 300 microns up to about 30 mm x 30 mm. Because of their relatively small size, a large number of individual LEDs are required in an array to provide sufficient light intensity.
  • one array may contain as many as about 8,000 LEDs.
  • the modules can also include other optical devices, for example, optical sensors and photosensors.
  • the individual LEDs are packed tightly in the array, such that the separation distance between individual LEDs may be on the order of about 30 microns to about 350 microns, and the pitch spacing may vary from about 50 microns to about 500 microns.
  • the large number of LEDs required for sufficient illumination, coupled with the need to tightly pack the individual LEDs together in an array makes the fabrication of LED array modules difficult.
  • each individual LED is bonded to a substrate with a conductive adhesive or solder and then, in a separate operation, each LED is wire-bonded to make an electrical connection between the LED and the substrate.
  • the necessity of making an electrical contact at the upper and lower surfaces of each LED works to increase the amount of substrate surface area necessary for mounting an LED array. Accordingly, the spatial illumination intensity is not optimum because of the relatively large spacing between each individual LED.
  • the use of conductive adhesives to bond each LED to the substrate can cause electrical shorts between adjacent LEDs.
  • the conductive adhesive can run between adjacent bond pads creating an electrical pathway.
  • the need to prevent shorting between adjacent LEDs is typically addressed by increasing the spacing between the LEDs, thus further limiting the density of the array.
  • the poor thermal conductivity of most commonly used electrically conductive adhesives can result in excessive heat build-up within an LED module.
  • the most common means of addressing the problem of excessive heat build-up is to increase the spacing between adjacent LEDs, again limiting the effective array density.
  • the present invention provides an optical device module and a process for fabricating the module that do not require the use of conductive adhesives, and in some embodiments, do not require the use of wire-bond technology.
  • a mounting substrate is provided having an electrical contact land on a surface of the mounting substrate.
  • An optical device such as an LED or photosensor, is provided that has an electrically conductive base surface opposite a face surface, wherein the face surface includes an electrical contact, referred to herein as a bond pad.
  • the optical device is bonded to the electrical contact land on the mounting substrate by attaching a plurality of electrically conductive hard particles to the base surface of the optical device or to the electrical contact land and applying an adhesive, which may be a non-electrically-conductive adhesive, to either the base surface or the contact land.
  • an adhesive which may be a non-electrically-conductive adhesive
  • the base surface of the optical device is then brought into contact with the contact land of the mounting substrate to create an electrical connection and the adhesive is cured.
  • a flip-chip bonding process includes electrically connecting an optical device with multiple bond pads on its face surface to corresponding multiple electrical contact lands on the subtrate.
  • the optical device is electrically connected to the electrical contact lands on the mounting substrate by attaching a plurality of electrically conductive hard particles to either the bond pads on the face surface of the optical device or to the electrical contact lands.
  • Mechanical attachment is facilitated by positioning an adhesive, which may be a non-electrically-conductive adhesive, between the face surface of the optical device and the substrate.
  • the electrically conductive hard particles may be metal particles, for example, of copper, aluminum, nickel, tin, bismuth, silver, gold, platinum, palladium, lithium, beryllium, boron, sodium, magnesium, potassium, calcium, gallium, germanium, rubidium, strontium, indium, antimony, cesium, and barium, and alloys and intermetallics of these metals.
  • the electrically conductive hard particles of the present invention may have a hard, non- conductive core surrounded by any of the metals set forth above.
  • the hard, non-conductive cores may be composed of, for example, diamond, garnet, ceramic, oxides, suicides, silicates, carbides, carbonates, borides, boron fibers, and nitrides.
  • the hard particles provide several advantages for connection of the optical devices over prior techniques. Because the hard particles provide the electrical connection between the optical devices and the substrate, an electrically conductive adhesive is not required to bond the optical devices to the substrate. Therefore, the optical devices may be arranged in closer proximity without concern for electrical shorting from electrically conductive adhesive running together.
  • the hard particles may be chosen to provide increased heat transfer capacity for the optical devices, thereby allowing the optical devices to be placed closer together.
  • hard particles with a diamond core provide exceptional heat transfer capabilities, as diamond has one of the highest coefficients of heat transfer of any substance. Closer spacing of the optical devices, without increasing heat retention, provides for higher intensity light output by the optical device modules.
  • the use of electrically conductive hard particles to form the attachment permits the use of a non-electrically-conductive adhesive, for example, a non-electrically-conductive adhesive having a low thermal resistance to physically attach the optical device to the contact land on the mounting substrate.
  • Suitable non-electrically- conductive adhesives may include, but are not limited to, for example, cyanoacrylate, epoxy- based adhesives, polyurethane-based adhesives, and UV-curable adhesives.
  • the non-electrically-conductive adhesives for use with the present invention may be chosen to provide significantly higher heat dissipation and transfer of the heat generated by the optical devices.
  • the optical devices may be placed substantially closer together, thus increasing the concentration of light output that may be provide by a module.
  • the process of the invention also enables copper or aluminum metallization, for example, to be used on the electrical contact lands, rather than a precious metal, for example, gold that does not oxidize.
  • copper or aluminum metallization for example, to be used on the electrical contact lands, rather than a precious metal, for example, gold that does not oxidize.
  • metals may be used because the electrically conductive hard particles pierce through the adhesive and any surface oxidation or other interfering residues (e.g., dirt, oil) on the electrical contacts of either or both the mounting substrate and the optical device, to ensure a robust electrical connection.
  • the electrically conductive hard particles are attached to the base surface of the optical device by placing the electrically conductive base surface in contact with the hard particles and applying a compressive force, such that the hard particles adhere to the base surface.
  • a compressive force such that the hard particles adhere to the base surface.
  • the term "adhere" as used herein, is meant in its broad sense of holding or sticking by any means, for example, gluing, suction, fusing, embedding, electrostatic forces, and van der Walls forces, and is not to be limited to the use of adhesive.
  • the adhesive is applied to the contact land, the base surface of the optical device is placed on the contact land, and the adhesive is cured.
  • the electrically conductive hard particles are applied to one of the contact land and the optical device. The optical device is then pressed on to the contact land to form an electrical connection between the device and substrate.
  • a process for fabricating an optical device module includes providing a substrate having a plurality of optical devices mounted on the substrate.
  • the optical devices may be mounted on the substrate using the process of the invention described above. Further, the optical devices may be an array of undiced optical devices on a portion of a wafer, where the entire wafer portion is mounted on the substrate.
  • Each optical device has at least one bond pad on the face surface of the device.
  • a cover is provided that has electrically conductive contact pads on an inner surface of the cover. The cover is constructed of a material that is transparent to light emitted or detected by the optical device.
  • a plurality of electrically conductive hard particles are positioned on either the contact pads or the bond pad on the optical device.
  • an LED array may include a plurality of closely packed optical devices, resulting in LED arrays requiring a small surface area and that provide high-intensity illumination.
  • an optical device module fabricated in accordance with the invention can be sealed in a single step. Since package leads, for example, wire bonds, are not necessary, all the connections to the bond pads of . each device can be made at the time the cover is attached to the module. Further, as a non- electrically-conductive adhesive may be used, an adhesive can be chosen to act not only as the mechanical bond between the optical device and the cover and substrate, but also to act as the sealing material for the entire covered module. Accordingly, an optical device module fabricated in accordance with the invention benefits from reduced product costs compared with optical device modules of the prior art.
  • the electrically conductive contact pads on the cover can be interconnected by metal traces positioned on the cover such that, when the contact pads are bonded to the bond pads, the cover is free of traces directly overlying each of the plurality of optical devices. In this way, the metal traces do not block the light emitted or detected by the devices during the operation of the module.
  • the cover is provided having an electrically conductive layer overlying an inner surface of the cover.
  • the electrically conductive layer is substantially transparent to the light emitted or detected by the optical devices.
  • the cover can further include a plurality of lenses positioned on a side opposite the electrically conductive contact pads.
  • Each of a plurality of lenses is positioned on the cover, such that each lens is in a spaced relationship with one or more of a plurality of LEDs.
  • the lenses serve to magnify the light emitted by the LEDs, thus increasing the output intensity of the LED array module.
  • Figures 2-5 illustrate, in cross-section, processing steps in accordance with the invention for bonding an illuminating device to a substrate.
  • Figure 6 illustrates an exploded cross-sectional view of a flip-chip bonding process in accordance with the invention.
  • Figure 7 illustrates, in cross-section, a portion of an illuminating device array module arranged in accordance with the invention.
  • Figure 8 illustrates a perspective view of an illuminating device array module assembly in accordance with the invention.
  • FIG. 1 Shown in Figure 1 is a cross-sectional view of an optical device 10 bonded to a substrate 12 in accordance with one embodiment of the invention.
  • the illuminating device 10 may be any of a number of different kinds of optical devices, for example, an LED, an optical sensor, and a photosensor.
  • the substrate 12 can be one of a number of electrical component mounting substrates, for example, a flexible chip carrier, a printed circuit board, a flexible lead frame tape, and a ceramic substrate.
  • the optical device 10 is bonded to an electrical contact land 14 residing on a surface 16 of the substrate 12.
  • An electrical contact between a base surface 18 of the optical device 10 and the electrical contact land 14 is made by a plurality of electrically conductive hard particles 20 and an adhesive layer 22.
  • the adhesive layer 22 serves to aid in the mechanical attachment of the illuminating device 10 to the substrate 12.
  • the adhesive layer 22 is a non-electrically conductive adhesive, for example, cyanoacrylate, an epoxy-based adhesive, a polyurethane-based adhesive, or a UN-curable adhesive.
  • the use of electrically conductive hard particles 20 to form an electrical connection between the optical device 10 and the electrical contact land 14 enables the use of a non-electrically conductive adhesive in the present invention.
  • the electrically conductive hard particles 20 can be hard particles formed from a metal or hard intermetallic material.
  • the electrically conductive hard particles may be metal particles, for example, of copper, aluminum, nickel, tin, bismuth, silver, gold, platinum, palladium, lithium, beryllium, boron, sodium, magnesium, potassium, calcium, gallium, germanium, rubidium, strontium, indium, antimony, cesium, and barium, and alloys and intermetallics of these metals.
  • the electrically conductive hard particles of the present invention may have a hard, non-conductive core surrounded by any of the metals set forth above.
  • the hard, non-conductive cores may be composed of, for example, diamond, garnet, ceramic, oxides, suicides, silicates, carbides, carbonates, borides, boron fibers, and nitrides.
  • electrically conductive hard particles 20 are composed of a diamond core plated with a layer of nickel.
  • a face surface 24 of the optical device 10 resides opposite the base surface 18 and includes a bond pad 26.
  • a wire bond 28 is attached to the bond pad 26 on the face surface 24 and to a metal lead 29 overlying the surface 16 of the substrate 12.
  • the optical device 10 may be activated by an electrical impulse, a constant electrical current, or both transmitted to the optical device 10 through the wire bond 28.
  • the optical device 10 is an LED
  • the optical device 10 will emit light when activated from a p-n junction 30 within the illuminating device 10.
  • an array of optical devices such as an LED array, will include numerous devices, typically arranged in a regular array on substrate 12.
  • Figures 2-5 illustrate processing steps in accordance with the invention for the bonding of the optical device 10 to the substrate 12.
  • a typical optical device array will include numerous optical devices 10 that may be arranged in a variety of geometric configurations on the surface of a substrate 12.
  • the process of the invention may be used to populate any of the substrates 12 described above with numerous optical devices 10.
  • the optical device 10 includes a metal layer 32 overlying the base surface 18.
  • the metal layer 32 is preferably a soft, deformable metal, for example, gold.
  • Electrically conductive hard particles 20 are disposed on a support surface 34. Although the electrically conductive hard particles 20 are illustrated as singularly spread across the support surface 34, the electrically conductive hard particles 20 can also be arranged within a containment vessel or reservoir and be randomly disposed within the containment vessel to a depth of several millimeters or more.
  • a compressive force is applied in a direction normal to the support surface 34 so that the hard particles 20 adhere to the base surface 18.
  • the hard particles 20 may at least partially penetrate the metal layer 32.
  • the magnitude of the compressive force will depend upon the nature of the adhesive attachment force. Further, the magnitude of the adhesion force may depend upon the hardness and surface texture of the metal layer 32 and the particular structure of the electrically conductive hard particles 20. For example, the amount of compressive force will increase where the metal layer 32 is a relatively hard metal.
  • the hard particles 20 should be chosen to have a hardness at least as great as the contact surfaces on the optical device 10 and substrate 12 (as well as on the cover 42 as described herein with reference to Figure 7), whereby the hard particles 20 can pierce through any surface oxidation or residue to create a sound electrical contact with the various contact surfaces.
  • a plurality of electrically conductive hard particles 20 is attached to the optical device 10 by adhering to the base surface 18 or by being at least partially embedded in the metal layer 32.
  • the optical device 10 may be maneuvered and positioned while the electrically conductive hard particles 20 remain securely attached to the base surface 18.
  • the method of the invention is particularly adaptable to pick-and- place mounting technology.
  • a control arm can maneuver the optical device 10 to an appropriate position on the substrate 12 for attachment of the optical device 10.
  • a layer of adhesive 22 is applied over the metal layer 32, as illustrated in Figure 4.
  • This material is preferably composed of any of the same adhesives as described earlier with reference to Figure 1.
  • the optical device 10 may simply be brought into contact with a viscous liquid adhesive, such that a layer of adhesive adheres to the metal layer 32 and the electrically conductive hard particles 20.
  • the adhesive layer 22 may be applied to the metal layer 32 by spreading a viscous adhesive material onto the metal layer 32.
  • the adhesive layer 22 may be an adhesive tape that is applied to the metal layer 32. Further, the adhesive layer 22 may be applied to either the metal layer 32, an electrical contact on the substrate, or both.
  • the optical device 10 is positioned on an electrical contact land 14 overlying the substrate 12, such that the adhesive material 22, with suspended electrically conductive hard particles 20 therein, is positioned between the optical device 10 and the electrical contact land 14.
  • a compressive force in a direction generally normal to the surface 16 of the substrate 12 is applied.
  • the electrically conductive hard particles 20 are at least partially embedded into the metal surface of the electrical contact land 14 and, if they have not already done so, into the metal layer 32 on the base surface 18 of the optical device 10.
  • an electrical contact is formed between the optical device 10 and the contact land 14.
  • the adhesive layer 22 is hardened by either a self-hardening mechanism or by thermal or UV curing of the adhesive 22.
  • the curing process drives off solvents and moisture from the adhesive material 22 and forms a hard, mechanical bond between the base surface 18 and the electrical contact land 14.
  • the adhesive layer 22 is a non-electrically conductive adhesive material, for example, cyano acrylate, that sets very rapidly with or without the application of heat or other treatments.
  • the adhesive layer 22 may be an ultraviolet-light (UV) curable polymer composition.
  • permanently hardenable adhesives for example, a hot melt adhesive, or a polymerizable adhesive, may be used.
  • the adhesive layer 22 may be a pressure-sensitive adhesive.
  • the adhesive 22 employed should have reduced levels of impurities that may adversely affect the component or the interconnection.
  • sodium and chlorine ions are known to cause electrical devices, such as the optical device 10 to fail, and sodium ions, in particular, promote corrosion of electrical interconnections under humid conditions.
  • the adhesive layer 22 may be applied to the electrical contact land 14 before positioning the optical device 10 in bonding position.
  • the adhesive layer 22 may be applied to the substrate 12 as either a liquid or an adhesive tape.
  • the adhesive material 22 is uniformly spread across the substrate 12 and over the contact lands 14. Where a filler is used, it is preferred that the filler not contain particles larger than the electrically conductive hard particles 20.
  • the adhesive layer 22 may also include an underfill material to enhance the integrity of the electrical contact. The underfill material may be dispensed around two adjacent sides of the optical device 10 and will flow by capillary action to fill any gaps between the base surface 18 and the contact land 14.
  • the electrically conductive hard particles 20 may be embedded in or attached to the contact land 14.
  • a soft metal layer is applied to the substrate 12. The soft metal is either applied over an existing metal contact land 14, or is used to form the contact land 14 itself. Compressive force is applied to adhere the conductive hard particles 20 to the soft metal layer.
  • the electrically conductive hard particles 20 may also be provided in conjunction with a conventional solder bonding process to enhance the electrical contact between the optical device 10 and the substrate 12.
  • an adhesive film containing electrically conductive hard particles 20 may be applied to contact lands 14.
  • Other methods for bonding optical devices 10 to the substrate 12 using hard particles 20 and adhesives 22 are further disclosed in U.S. patent application serial number 09/812,140 entitled “Electrical Component Assembly and method of Fabrication,” filed 19 March 2001, which is hereby incorporated herein by reference. This application further discloses methods for plating hard particles 20 onto substrates 12 using an electrolytic plating process, which process may also be used in conjunction with the present invention.
  • the electrically conductive hard particles 20 are deposited on the contact lands 14 using a two-step electroless plating process.
  • metal and hard particle cores are co-deposited on the support surface 34.
  • the metal is preferably nickel, although other metals can also be used.
  • a catalytic zinc solution is applied to activate the surfaces of the hard particle cores.
  • a second metal layer is then plated over the hard particle cores. The second metal layer strongly adheres to the activated surfaces of the hard particle cores.
  • the preferred metal is nickel, although other metals can be used.
  • the electrically conductive hard particles 20 may be applied using a stencil or screen printing process in which the hard particles 20 are entrained in a viscous liquid, for example, by the methods disclosed in PCT patent application serial number entitled “Method and Material for Printing Particle-Enhanced Electrical Contacts,” filed 24 October 2001, which is hereby incorporated herein by reference.
  • the stencil or screen is placed on the substrate 12 and the viscous liquid is applied to the surface 16 in surface regions exposed by the stencil or screen.
  • the electrically conductive hard particles 20 can be attached to either the base surface 18 of the optical device 10, or to both the optical device 10 and to the contact land 14.
  • the incorporation of the electrically conductive hard particles 20 in the present invention advantageously enables the use of non-electrically conductive adhesives to form an electrical contact. Because the adhesive is not electrically conductive, there is no danger of shorting adjacent illuminating devices located on substrate 12. Further, to improve the thermal conductivity of the electrical contact, an adhesive with low heat resistance may be used.
  • a wire bond 28 may be bonded to the bond pad 26 on the face surface 24 and to the metal lead 29, as shown in Figure 1.
  • the substrate 12, when populated with a plurality of optical devices 10, may be incorporated into an optical device module, for example, LED array module, for use as an illumination source.
  • an array module will benefit from the bonding process of the invention.
  • the individual LEDs may be tightly packed together, since the use of a non-electrically conductive adhesive removes the possibility of electrical shorts developing between adjacent illuminating devices.
  • Figure 6 illustrates an exploded cross-sectional view of a flip-chip bonding process carried out in accordance with the invention. Bond pads 26 on the face surface 24 of the optical device 10 are aligned to a pair of electrical contact lands 14 on the substrate 12.
  • the bond pads 26 may be formed by any of a number of conventional flip-chip connection metalization structures, for example, ball bonding metals, solder bump metals, and controlled-collapsible-chip-connection (C4) metals. Further, using a standard metal deposition process, a soft metal may be applied to the surface of the bond pads 26 or to the contact lands 14, or both, to aid the adherence of the hard particles 20 to the contact metallization. An electrical connection may be formed between the bond pads 26 and the contact lands 14 using any of the particle-enhanced bonding processes described above. Similar to the bonding processes described above, the adhesive layer 22 is applied to aid in the mechanical attachment of the optical device 10 to the substrate 12. In the case of flip-chip attachment, the adhesive layer 22 is one of the non-electrically conductive adhesive materials described above.
  • the bonding process previously described may be applied to the face surface 24 of an optical device 10 and a transparent cover 42 positioned over an array of optical devices.
  • Figure 7 illustrates, in cross- section, an optical device module 36 arranged in accordance with the invention.
  • the module 36 includes a substrate 38 with a plurality of optical devices 40 positioned thereon.
  • the plurality of optical devices 40 may be individual optical devices 40 bonded to the contact lands 44 and contact pads 46 using the bonding process previously described.
  • the optical devices 40 may be an array of undiced optical devices 40 on a portion of a wafer.
  • the entire wafer-portion is bonded to the substrate 38 as a single unit by non-electrically-conductive adhesive 48 and each of the electrical contacts on the base surfaces 52 of the optical devices 40 (or face surfaces 24 if the optical devices 40 are flip-chips) is electrically connected to corresponding contact lands 44 on the substrate 38 by hard particles 20.
  • a transparent cover 42 is positioned opposite the substrate 38 and overlies the optical devices 40.
  • the optical devices 40 are bonded to the contact lands 44 on the substrate 38 and to the contact pads 46 on the transparent cover 42.
  • the cover 42 in such an embodiment need not have contact pads 46 for connection with the optical devices 40.
  • An adhesive material 48 is positioned between the substrate 38 and the transparent cover 42, and may fill the regions not occupied by the optical devices 40 to seal the optical device module 36 between the substrate 38 and the cover 42.
  • the adhesive material 48 may be transparent to light emitted or detected by the optical devices 40.
  • the adhesive material 48 may also include an underfill material.
  • the contact pads 46 are electrically attached to bond pads (not shown) on a face surface 50 of each optical device 40 and the contact lands 44 are bonded to a base surface 52 of each optical device 40.
  • the device module 36 is illustrated in Figure 7 as including an adhesive layer 48 generally distributed between the substrate 38 and the transparent cover 42, the adhesive material 48 may be limited to an area between the face surface 50 of the optical devices 40 and the transparent cover 42 and an area between the contact lands 44 on the substrate 38 and the base surface 52 of each optical device 40.
  • the contact pads 46 are formed of a material that is substantially transparent to the light emitted by the optical devices 40.
  • the contact pads 46 may be indium-tin-oxide or another electrically conductive material that is substantially transparent to the emitted light.
  • lenses such as lens 54
  • the lens 54 may be positioned in spaced relationship with each optical device 40. Accordingly, the light emitted by the optical device 40 is focused by the lens 54.
  • a single lens 54 may be positioned to focus the light of multiple optical devices 40. In such an embodiment, either the lens 54, the substrate 38, or both may be curved to augment the focal ability of the lens 54.
  • the lens 54 is shown overlying a surface of the transparent cover 42, the lens 54 can also be positioned within an opening in the transparent cover 42.
  • the positioning of the lens 54 in an opening in the transparent cover 42 may take place during a molding operation, in which the transparent cover 42 is molded, for example, from a polycarbonate material. In such a process, the lens 54 is firmly affixed to or within the transparent cover 42 during the molding process.
  • metal traces 56 may be positioned on an inner surface 58 of the transparent cover 42, as illustrated in Figure 8.
  • the metal traces 56 are positioned on the surface 58, such that when the transparent cover 42 is bonded to the optical devices 40, the metal traces 56 do not overlie substantial portions of the optical devices 40.
  • the metal traces 56 may be any of a number of commonly used interconnect metals, for example, copper and aluminum.
  • a plurality of hard particles are positioned on either the bond pads 26 on the face surface 24, or on the contact pads 46, such that each contact pad or bond pad has at least one hard particle associated therewith.
  • An adhesive is applied to either the face surface 24 of the optical devices 40 or the contact pads 46, and the contact pads 46 are brought into compressive contact with the bond pads 26. In this manner, electrical contacts between the contact pads 46 on the cover 42 and the optical devices 40, as well as the sealing of the module 36, may be made in a single step of pressing the cover 42 and the substrate 38 together, rather than the multiple steps of wire boding each of the bond pads 50 to a contact surface.
  • the bond pads 26 can be any of a number of different contact structures for making electrical contact with the optical devices 40.
  • the bond pads 26 may be stud-bumped contacts as commonly used in surface mount devices.
  • the bond pads 26 may be, for example, C4 contacts or ball grid array contacts.
  • the transparent cover 42 may be fabricated from any material that is substantially transparent to the light emitted or detected by the optical devices 40.
  • the transparent cover 42 may be, for example, a glass material, a plastic, or a ceramic. In accordance with the invention, the selection of the particular material for the transparent cover 42 is dependent upon the particular wavelength of light emitted or detected by the optical devices 40.
  • some optical devices 40 are designed to emit or receive visible light, infrared light, or ultra-violet light.
  • the transparent cover 42 is fabricated from molded polycarbonate.
  • optical device module and fabrication method that fully provides the advantages set forth above.
  • the invention has been described and illustrated with reference to specific illustrative embodiments thereof, it is not intended that the invention be limited to those illustrative embodiments.
  • Those skilled in the art will recognize that variations and modifications can be made without departing from the spirit of the invention.
  • optical sensors can be combined with LEDs within the same module.
  • numerous additional materials can be included to fabricate additional components of a device module, for example, side moldings and electrical interconnections. It is therefore intended that all such variations and modifications be included within the invention as fall within the scope of the appended claims and equivalents thereof.

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Abstract

Un module (36) de dispositifs optiques, par exemple, un module de réseaux de DEL ou un module de photocapteurs, comprend des dispositifs optiques (40) fixés électriquement à des surfaces de contact (44) sur un substrat (38) par des particules électroconductrices dures et fixés par un adhésif non électroconducteur (48). Le module (36) peut comprendre un couvercle (42) transparent à la lumière émise ou détectée par les dispositifs optiques (40) et présentant des plages de contact électroconductrices (46), lesquelles sont liées à des plages de connexion (50) sur les dispositifs optiques (40). Un procédé de fabrication d'un module (36) de dispositifs optiques consiste à connecter électriquement le dispositif optique (40) à la surface de contact électrique (44) sur le substrat, par fixation de particules dures électroconductrices soit à la surface de base (52) du dispositif optique (40), soit aux surfaces de contact électrique (44). Un adhésif (48) est appliqué au substrat (38) ou à une surface de contact (44), et le dispositif optique (40) est placé sur la surface de contact (44) et l'adhésif (48) est durci.
PCT/US2002/001822 2001-01-22 2002-01-18 Module de dispositifs optiques et procede de fabrication Ceased WO2002067017A2 (fr)

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Application Number Priority Date Filing Date Title
AU2002253875A AU2002253875A1 (en) 2001-01-22 2002-01-18 Optical device module and method of fabrication

Applications Claiming Priority (2)

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US26323401P 2001-01-22 2001-01-22
US60/263,324 2001-01-22

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US3899826A (en) * 1971-12-20 1975-08-19 Motorola Inc Scannable light emitting diode array and method
JPS59195837A (ja) * 1983-04-21 1984-11-07 Sharp Corp Ｌｓｉチツプボンデイング方法
US5616206A (en) * 1993-06-15 1997-04-01 Ricoh Company, Ltd. Method for arranging conductive particles on electrodes of substrate
JP3337405B2 (ja) * 1996-12-27 2002-10-21 シャープ株式会社 発光表示素子およびその電気配線基板への接続方法ならびに製造方法
US5990498A (en) * 1997-09-16 1999-11-23 Polaroid Corporation Light-emitting diode having uniform irradiance distribution

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