US20090230409A1 - Underfill process for flip-chip leds - Google Patents
Underfill process for flip-chip leds Download PDF

Info

Publication number

US20090230409A1

US20090230409A1 US12/050,082 US5008208A US2009230409A1 US 20090230409 A1 US20090230409 A1 US 20090230409A1 US 5008208 A US5008208 A US 5008208A US 2009230409 A1 US2009230409 A1 US 2009230409A1

Authority

US

United States

Prior art keywords

underfill material

led

led die

submount

underfill

Prior art date

2008-03-17

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.)

Abandoned

Application number

US12/050,082

Other languages

English (en)

Inventor

Grigoriy Basin

Frederic Diana

Paul S. Martin

Dima Simonian

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.)

Koninklijke Philips NV

Lumileds LLC

Original Assignee

Philips Lumileds Lighing Co LLC

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.)

2008-03-17

Filing date

2008-03-17

Publication date

2009-09-17

Family has litigation

First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=40677561&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=US20090230409(A1) "Global patent litigation datasetâ by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.

2008-03-17 Application filed by Philips Lumileds Lighing Co LLC filed Critical Philips Lumileds Lighing Co LLC

2008-03-17 Priority to US12/050,082 priority Critical patent/US20090230409A1/en

2008-03-17 Assigned to PHILIPS LUMILEDS LIGHTING COMPANY, LLC reassignment PHILIPS LUMILEDS LIGHTING COMPANY, LLC ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SIMONIAN, DIMA, MARTIN, PAUL S., DIANA, FREDERIC, BASIN, GRIGORIY

2009-03-13 Priority to RU2010142267/28A priority patent/RU2502157C2/ru

2009-03-13 Priority to KR1020107023171A priority patent/KR101524004B1/ko

2009-03-13 Priority to CN2009801094605A priority patent/CN102084505B/zh

2009-03-13 Priority to BRPI0909788-0A priority patent/BRPI0909788B1/pt

2009-03-13 Priority to EP09722834.0A priority patent/EP2266149B1/en

2009-03-13 Priority to JP2011500333A priority patent/JP5372133B2/ja

2009-03-13 Priority to PCT/IB2009/051055 priority patent/WO2009115968A1/en

2009-03-16 Priority to TW098108499A priority patent/TWI463701B/zh

2009-09-17 Publication of US20090230409A1 publication Critical patent/US20090230409A1/en

2011-05-24 Assigned to KONINKLIJKE PHILIPS ELECTRONICS N.V., LUMILEDS LIGHTING COMPANY LLC reassignment KONINKLIJKE PHILIPS ELECTRONICS N.V. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LUMILEDS LIGHTING COMPANY LLC

2011-05-25 Priority to US13/115,475 priority patent/US8273587B2/en

Status Abandoned legal-status Critical Current

Links

USPTO

USPTO PatentCenter

USPTO Assignment

Espacenet

Global Dossier

Discuss

238000000034 method Methods 0.000 title claims abstract description 62

239000000463 material Substances 0.000 claims abstract description 111

239000000758 substrate Substances 0.000 claims abstract description 37

238000000465 moulding Methods 0.000 claims abstract description 15

239000007788 liquid Substances 0.000 claims abstract description 13

239000011325 microbead Substances 0.000 claims abstract description 10

238000005422 blasting Methods 0.000 claims abstract description 6

239000007787 solid Substances 0.000 claims description 7

229920006336 epoxy molding compound Polymers 0.000 claims description 4

238000010438 heat treatment Methods 0.000 claims description 4

238000005530 etching Methods 0.000 claims description 2

229920000642 polymer Polymers 0.000 claims description 2

238000001816 cooling Methods 0.000 claims 2

238000000748 compression moulding Methods 0.000 abstract description 3

238000004519 manufacturing process Methods 0.000 abstract 1

239000010410 layer Substances 0.000 description 34

239000004593 Epoxy Substances 0.000 description 7

239000004642 Polyimide Substances 0.000 description 6

239000011344 liquid material Substances 0.000 description 6

229920001721 polyimide Polymers 0.000 description 6

238000007906 compression Methods 0.000 description 5

230000009477 glass transition Effects 0.000 description 5

229910052751 metal Inorganic materials 0.000 description 5

239000002184 metal Substances 0.000 description 5

229910052594 sapphire Inorganic materials 0.000 description 5

239000010980 sapphire Substances 0.000 description 5

230000006835 compression Effects 0.000 description 4

238000002347 injection Methods 0.000 description 4

239000007924 injection Substances 0.000 description 4

239000000843 powder Substances 0.000 description 4

239000004065 semiconductor Substances 0.000 description 4

238000005253 cladding Methods 0.000 description 3

238000000605 extraction Methods 0.000 description 3

238000001020 plasma etching Methods 0.000 description 3

229910000679 solder Inorganic materials 0.000 description 3

239000011343 solid material Substances 0.000 description 3

IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2

UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2

229910052782 aluminium Inorganic materials 0.000 description 2

XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2

239000000356 contaminant Substances 0.000 description 2

238000005336 cracking Methods 0.000 description 2

238000001746 injection moulding Methods 0.000 description 2

238000001465 metallisation Methods 0.000 description 2

238000012986 modification Methods 0.000 description 2

230000004048 modification Effects 0.000 description 2

GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1

238000010521 absorption reaction Methods 0.000 description 1

239000000853 adhesive Substances 0.000 description 1

230000001070 adhesive effect Effects 0.000 description 1

239000000919 ceramic Substances 0.000 description 1

238000007796 conventional method Methods 0.000 description 1

229910052733 gallium Inorganic materials 0.000 description 1

239000007789 gas Substances 0.000 description 1

PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1

239000010931 gold Substances 0.000 description 1

229910052737 gold Inorganic materials 0.000 description 1

239000011810 insulating material Substances 0.000 description 1

229910052757 nitrogen Inorganic materials 0.000 description 1

230000006911 nucleation Effects 0.000 description 1

238000010899 nucleation Methods 0.000 description 1

230000002093 peripheral effect Effects 0.000 description 1

229910000030 sodium bicarbonate Inorganic materials 0.000 description 1

238000005476 soldering Methods 0.000 description 1

239000002344 surface layer Substances 0.000 description 1

239000011800 void material Substances 0.000 description 1

Images

Classifications

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10

H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof

H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages

H01L33/52—Encapsulations

H01L33/54—Encapsulations having a particular shape

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10

H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto

H01L24/93—Batch processes

H01L24/95—Batch processes at chip-level, i.e. with connecting carried out on a plurality of singulated devices, i.e. on diced chips

H01L24/97—Batch processes at chip-level, i.e. with connecting carried out on a plurality of singulated devices, i.e. on diced chips the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting

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

H01L2224/10—Bump connectors; Manufacturing methods related thereto

H01L2224/15—Structure, shape, material or disposition of the bump connectors after the connecting process

H01L2224/16—Structure, shape, material or disposition of the bump connectors after the connecting process of an individual bump connector

H01L2224/161—Disposition

H01L2224/16151—Disposition the bump 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

H01L2224/16221—Disposition the bump 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

H01L2224/16225—Disposition the bump 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

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

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

H01L2224/73201—Location after the connecting process on the same surface

H01L2224/73203—Bump and layer connectors

H01L2224/73204—Bump and layer connectors the bump connector being embedded into the layer connector

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10

H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof

H01L33/005—Processes

H01L33/0093—Wafer bonding; Removal of the growth substrate

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10

H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof

H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages

H01L33/52—Encapsulations

H01L33/56—Materials, e.g. epoxy or silicone resin

Definitions

This invention relates to flip-chip light emitting diodes (LEDs) and, in particular, to a process for supplying a dielectric underfill material in the gap between the LED chip and its submount.

LEDs flip-chip light emitting diodes

FIG. 1 illustrates a conventional LED 10 flip chip mounted on a portion of a submount wafer 22 .

both the n and p contacts are formed on the same side of the LED die opposite to the growth substrate 12 side.

the LED 10 is formed of semiconductor epitaxial layers, including an n-layer, an active layer, and a p-layer, grown on a growth substrate 12 , such as a sapphire substrate.

the epitaxial layers are GaN based, and the active layer emits blue light. Any other type of flip chip LED is applicable to the present invention.

Metal electrodes 14 are formed on the LED 10 that electrically contact the p-layer, and metal electrodes 16 are formed on the LED 10 that electrically contact the n-layer.

the electrodes are gold bumps that are ultrasonically welded to anode and cathode metal pads 18 and 20 on a ceramic submount wafer 22 .

the submount wafer 22 has conductive vias 24 leading to bottom metal pads 26 and 28 for bonding to a printed circuit board. Many LEDs are mounted on the submount wafer 22 and will be later singulated to form individual LEDs/submounts.

the underfill material 30 is then injected under and around the LED 10 to fill in air gaps between the LED 10 and submount wafer 22 .

the underfill material 30 is typically liquid epoxy that is then cured to harden.

the hardened underfill provides structural support and protects the chip from contaminants.

the underfill material 30 is injected by a nozzle 32 that is moved around the LED 10 while injecting the underfill material 30 at a relatively high pressure to fill the narrow gap between the LED 10 and submount wafer 22 .

the underfill may extend further laterally than shown in the figures in actual devices.

any excess underfill material 30 e.g., epoxy

any excess underfill material 30 e.g., epoxy

the growth substrate 12 is then removed using a laser lift-off process (not shown).

the photon energy of the laser e.g., an excimer laser

the photon energy of the laser is selected to be above the band gap of the LED material and below the absorption edge of the sapphire substrate (e.g., between 3.44 eV and 6 eV).

Pulses from the laser through the sapphire are converted to thermal energy within the first 100 nm of the LED material.

the generated temperature is in excess of 1000Â° C. and dissociates the gallium and nitrogen.

the resulting high gas pressure pushes the substrate away from the epitaxial layers to release the substrate from the layers, and the loose substrate is then simply removed from the LED structure.

the underfill helps prevent the thin LED layers from cracking under the high pressure.

the growth substrate 12 may instead be removed by etching, such as reactive ion etching (RIE), or grinding.

etching such as reactive ion etching (RIE), or grinding.

RIE reactive ion etching

Other techniques may be used depending on the type of LED and substrate.

the substrate is Si-based and an insulating material between the substrate and the LED layers is etched away by a wet etch technique to remove the substrate.

the submount wafer 22 is then sawed or scribed and broken to singulate the LEDs/submounts.

the submounts may then be soldered to a printed circuit board.

the underfill process is sequentially performed on an array of LEDs mounted on a submount wafer, prior to the LEDs being singulated. There may be 500-4000 LEDs mounted on a single submount wafer, depending on the size of each LED and the density. Injecting the underfill material under each LED in the array using a single moving nozzle may take 10-40 minutes, depending on the number of LEDs.

Another problem is that the properties of the underfill material must be carefully selected for proper viscosity, thermal expansion, reliability over the long lifetime of the LED, dielectric properties, thermal conductivity, contaminant protection, and other factors. If the viscosity is too high, the pressure needed to inject the underfill under the LED to fill all voids may damage the LED. Voids must be eliminated since any air will expand when the LED/submount becomes hot and push the LED off the submount. Further, since a void area does not support the LED during the laser lift-off process, the downward stress on the LED during the laser lift-off process may crack the LED.

Thermal expansion of the underfill is extremely important since the LEDs undergo a solder reflow process when soldering a singulated LED/submount to a printed circuit board. Such temperatures may be 265Â° C.

the solder reflow temperature is above the typical 185Â° C. glass transition temperature for epoxy, which is the typical underfill material.

the glass transition temperature (T g ) is the temperature at which epoxy becomes soft. Above the glass transition temperature, the epoxy thermal expansion rises significantly, causing upward pressure on the LED, resulting in cracking or lifting off of the LED.

An underfill technique for LEDs is described where compression molding is used. The process is performed prior to any substrate lift-off process.

the LEDs, mounted on a submount wafer, are placed in a mold.

the mold is sealed at least around the perimeter of the submount wafer, and a vacuum is created within the mold.

the mold may be aluminum with separate cavities aligned with each LED on the submount wafer.

any suitable underfill material such as a liquid polyimide, is then applied to the inlet of the mold under pressure, and the combination of the vacuum and the liquid material pressure causes the material to completely fill the cavities in the mold where the LEDs are located. There are no voids once the material has filled the mold.

each mold cavity causes the liquid material to completely encapsulate each LED, along with its growth substrate.

the liquid material is then cured by heat or UV light to harden the underfill material, and the mold is released from the submount wafer.

a higher temperature post cure may be performed after the mold is released.

the liquid underfill material may first fill the mold, having a peripheral raised seal, and then the submount wafer is placed over the mold so that the LEDs are immersed in the underfill material. Under compression, the liquid material fills all voids under each LED. Air is pushed out through the seals along with a certain amount of the underfill material. The material is then cured, and the mold released from the submount wafer. Since such a molding process does not rely on the injection of the liquid material under pressure at an inlet of the mold, there is little possibility of damage to the fragile LEDs.

the underfill material used to fill the mold is not a liquid but is a powder or small tablets.

the solid material is then heated in the mold to melt or soften it so that it can conform to the mold and encapsulate the LEDs. Compression is used to mold the softened material and cause it to flow into the voids under each LED. Handling the underfill material as a solid has various benefits. Such compression molding using an initially solid underfill material greatly increases the number of possible underfill materials.

One of the materials which can be used for this process is the powder of an epoxy molding compound.

the entire submount wafer is subjected to a microbead blasting process to etch away the underfill material until all of the growth substrate is exposed.

the substrate is then removed using a laser lift-off process, or other suitable process.

the underfill supports the thin LED during this process.

the LED may be thinned to improve light extraction.

the surface of the LED may then be roughened to further improve light extraction by reducing the number of internal reflections.

Lenses may then be molded over the LEDs and/or other wafer-level processing techniques may be performed.

the LEDs/submounts are then singulated using sawing, scribe and break, or any other technique.

a preferred underfill material that can be used with the present process is a polyimide, which has a glass transition temperature near or above the solder reflow temperature, so that there is very little thermal expansion of the polyimide under worst case conditions.

the underfill processing time can be reduced to only a few minutes.

FIG. 1 is a cross-sectional view of a prior art flip-chip LED, mounted on a submount, where the LED underfill material is dispensed under pressure by a small nozzle at the base of the LED.

FIG. 2 illustrates a simplified portion of a submount wafer populated by an array of LEDs, such as 500-4000 LEDs.

FIG. 3A illustrates a wafer-level injection molding process used to encapsulate all LEDs on the submount wafer with an underfill material.

FIG. 3B illustrates an alternative type of wafer-level molding process, not using injection, used to encapsulate all LEDs on the submount wafer with an underfill material.

FIG. 4 illustrates the LEDs on the wafer after being removed from the mold of FIG. 3A or FIG. 3B .

FIG. 5 illustrates the upper portion of the underfill material of FIG. 4 being removed by microbead blasting.

FIG. 6 illustrates a laser lift-off technique for removing the growth substrates from the LEDs.

FIG. 7 is a cross-sectional view of a single LED mounted on a submount after the LED has been thinned and after the LEDs/submounts have been singulated.

the submount is shown soldered to a printed circuit board.

a conventional LED is formed on a growth substrate.

the LED is a GaN-based LED, such as an AlInGaN or InGaN LED, for producing blue light.

a relatively thick n-type GaN layer is grown on a sapphire growth substrate using conventional techniques.

the relatively thick GaN layer typically includes a low temperature nucleation layer and one or more additional layers so as to provide a low-defect lattice structure for the n-type cladding layer and active layer.

One or more n-type cladding layers are then formed over the thick n-type layer, followed by an active layer, one or more p-type cladding layers, and a p-type contact layer (for metallization).

portions of the p-layers and active layer are etched away to expose an n-layer for metallization.

the p contact and n contact are on the same side of the chip and can be directly electrically attached to the submount contact pads. Current from the n-metal contact initially flows laterally through the n-layer.

the flip-chip LED used as an example in the present invention is the LED structure of FIG. 1 comprising a semiconductor LED 10 , its growth substrate 12 , and its electrodes 14 / 16 , where the LED is mounted on a submount wafer 22 .

FIG. 2 is a simplified illustration of a submount wafer 22 on which is mounted an array of LEDs. There may be 500-4000 LEDs on a single submount wafer 22 . An LED is also referred to herein as an LED die.

FIG. 3A illustrates one type of suitable injection molding process for creating the underfill for each LED.

a mold 36 has cavities 38 that define the shape of the hardened underfill material after the molding process.

the mold 36 may be formed of aluminum.

the mold 36 has a perimeter seal 37 that seals against the submount wafer 22 when the mold 36 is aligned with the wafer 22 and pressed against the wafer 22 .

the mold 36 has at least one inlet 40 , for injecting the liquid underfill material 41 (e.g., a polyimide), and at least one outlet 42 connected to a vacuum source.

the liquid underfill material 41 e.g., a polyimide

the underfill material 41 is injected through inlet 40 .

the underfill material 41 flows into all the cavities 38 via channels 44 between the cavities, assisted by the vacuum and the injection pressure of the material 41 .

the vacuum removes almost all the air in the mold 36 .

the entire mold 36 will be filled with the underfill material 41 , including all voids under the LEDs.

the mold 36 is then heated to cure the liquid underfill material.

the temperature of the mold 36 during curing is about 150Â° C.

a transparent mold may be used and the underfill material may be cured with UV light.

FIG. 3B illustrates an alternative wafer-level molding process that does not use pressure injection of the underfill material.

the mold 48 has cavities 50 that are first filled with the liquid underfill material 41 at atmospheric pressure.

the submount wafer 22 is brought against the mold 48 so that the LEDs are immersed in the underfill material in each cavity 50 .

the wafer 22 and mold 48 are pressed together to force the underfill material to fill all voids.

a perimeter seal 53 allows the pressure to be high while allowing all air to escape as the underfill material fills the voids.

a vacuum may also be pulled between the wafer 22 and the mold 48 using a vacuum source around the seal 53 .

the mold 48 is then heated to cure the liquid underfill material.

a transparent mold may be used and the underfill material may be cured with UV light.

the mold of FIG. 3A or 3 B is then removed from the wafer 22 , resulting in the structure of FIG. 4 , having excess hardened underfill material 54 encapsulating each LED. There may also be a thin layer of hardened underfill material on the wafer 22 surface between each LED depending on the mold.

the wafer 22 may then be subject to a post-cure temperature of about 250Â° C. to additionally harden the underfill material.

a post-cure temperature of about 250Â° C. to additionally harden the underfill material.

its glass transition temperature (Tg) is between 260-300Â° C., so a post cure temperature less than the Tg is preferred to limit any thermal expansion of the underfill.

the underfill material used to fill the mold is not a liquid but is a powder or small tablets.

the solid material is then heated in the mold of FIG. 3A or FIG. 3B to melt or soften it. Compression is used to cause the softened material to take the form of the mold and to fill the voids under the LEDs while encapsulating the LEDs.

the melted or softened material is then cured or cooled, if necessary, to make it solid again. Certain materials hardened automatically after the heating and compression process. Handling the underfill material as a solid has various benefits.

suitable materials that can be used for an underfill are not a liquid at room temperatures prior to curing, so heating up a solid material in the mold followed by compression greatly increases the number of possible materials that can be used as an underfill.

One suitable solid polymer that can be used is an epoxy molding compound in powder form.

the underfill material 54 over the growth substrate 12 must be first removed. If the growth substrate 12 will be removed by grinding or another mechanical etch process, such grinding may be used to simultaneously remove the excess underfill material 54 .

FIG. 5 illustrates the removal of the excess underfill material 54 by blasting the entire surface of the wafer 22 with high-velocity microbeads 58 .

the microbeads 58 have diameters between 1-20 microns and are formed of NaHCO 3 .

the microbeads 58 are accelerated through a nozzle by air at a pressure of about 100 psi or less.

the nozzle may be large to etch the underfill material 54 from all or a large portion of the wafer 22 without the nozzle moving, or a smaller nozzle may be used to etch the underfill material 54 off only a few LEDs at a time followed by the nozzle moving to a next position over the wafer 22 .

Removing excess material of any kind using microbeads is a known process.

the underfill material 54 is etch so that its top surface intersects an edge of the LED semiconductor layers to ensure that the entire LED is supported by the underfill during the substrate laser lift-off process.

FIG. 6 illustrates the laser lift-off process, previously described.

the laser pulses are shown by arrows 60 .

the surface of the GaN absorbs heat, causing the surface layer to decompose into the Ga and N 2 .

the N 2 pressure pushes the sapphire substrate away from the LED.

the growth substrates 12 become detached from the semiconductor LED layers during the lift-off process, they are removed by, for example, an adhesive sheet or some other suitable process.

the exposed LED layers are then thinned by, for example, RIE or a mechanical etch, since the exposed top layer is a relatively thick n-layer, and the surface has been damaged by the laser lift-off process.

the resulting top surface may then be roughened to increase the light extraction efficiency.

wafer-level processes may also be performed on the LED array while mounted on the submount wafer 22 .

One such process may be to overmold a lens on each LED in a single mold process similar to that shown in FIG. 3A or 3 B. Details of a wafer-level lens molding process are described in Patent Publication US 2006/0105485, entitled Overmolded Lens Over LED Die, by Grigoriy Basin et al., assigned to the present assignee and incorporated herein by reference.

FIG. 7 illustrates a single LED/submount soldered to pads on a printed circuit board 64 .

the underfill material may be selected substantially independently of its viscosity.

the dielectric underfill material may be primarily chosen based on its coefficient of thermal expansion, ease of use, and reliability under all temperatures to which the LED is subjected.

a polyimide is the preferred underfill, possessing much better qualities than epoxy.

Landscapes

Engineering & Computer Science (AREA)

Microelectronics & Electronic Packaging (AREA)

Computer Hardware Design (AREA)

Power Engineering (AREA)

Manufacturing & Machinery (AREA)

Led Device Packages (AREA)

Encapsulation Of And Coatings For Semiconductor Or Solid State Devices (AREA)

US12/050,082 2008-03-17 2008-03-17 Underfill process for flip-chip leds Abandoned US20090230409A1 (en)

Priority Applications (10)

Application Number Priority Date Filing Date Title US12/050,082 US20090230409A1 (en) 2008-03-17 2008-03-17 Underfill process for flip-chip leds PCT/IB2009/051055 WO2009115968A1 (en) 2008-03-17 2009-03-13 Underfill process for flip-chip leds JP2011500333A JP5372133B2 (ja) 2008-03-17 2009-03-13 ããªãããããï½ï½ ï½ã«é¢ããã¢ã³ãã¼ãã£ã«å¦ç EP09722834.0A EP2266149B1 (en) 2008-03-17 2009-03-13 Underfill process for flip-chip led KR1020107023171A KR101524004B1 (ko) 2008-03-17 2009-03-13 íë¦½ ì¹© ï½ï½ ï½ë¥¼ ìí ì¸ëí íë¡ì¸ì¤ CN2009801094605A CN102084505B (zh) 2008-03-17 2009-03-13 ç¨äºåè£ è¯çledçåºé¨å¡«å å·¥èº BRPI0909788-0A BRPI0909788B1 (pt) 2008-03-17 2009-03-13 mÃ©todo para fabricar um dispositivo emissor de luz RU2010142267/28A RU2502157C2 (ru) 2008-03-17 2009-03-13 ÐÑÐ¾ÑÐµÑÑ ÑÐ¾ÑÐ¼Ð¸ÑÐ¾Ð²Ð°Ð½Ð¸Ñ Ð¿ÑÐ¾ÐºÐ»Ð°Ð´ÐºÐ¸ Ð´Ð»Ñ Ð¿ÐµÑÐµÐ²ÐµÑÐ½ÑÑÑÑ ÑÐ¸Ð´ TW098108499A TWI463701B (zh) 2008-03-17 2009-03-16 ç¨æ¼è¦æ¶ç¼å äºæ¥µé«çåºé¨å¡«å èç US13/115,475 US8273587B2 (en) 2008-03-17 2011-05-25 Underfill process for flip-chip LEDs

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title US12/050,082 US20090230409A1 (en) 2008-03-17 2008-03-17 Underfill process for flip-chip leds

Related Child Applications (1)

Application Number Title Priority Date Filing Date US13/115,475 Division US8273587B2 (en) 2008-03-17 2011-05-25 Underfill process for flip-chip LEDs

Publications (1)

Publication Number Publication Date US20090230409A1 true US20090230409A1 (en) 2009-09-17

Family

ID=40677561

Family Applications (2)

Application Number Title Priority Date Filing Date US12/050,082 Abandoned US20090230409A1 (en) 2008-03-17 2008-03-17 Underfill process for flip-chip leds US13/115,475 Active 2028-03-25 US8273587B2 (en) 2008-03-17 2011-05-25 Underfill process for flip-chip LEDs

Family Applications After (1)

Application Number Title Priority Date Filing Date US13/115,475 Active 2028-03-25 US8273587B2 (en) 2008-03-17 2011-05-25 Underfill process for flip-chip LEDs

Country Status (9)

Country Link US (2) US20090230409A1 (da) EP (1) EP2266149B1 (da) JP (1) JP5372133B2 (da) KR (1) KR101524004B1 (da) CN (1) CN102084505B (da) BR (1) BRPI0909788B1 (da) RU (1) RU2502157C2 (da) TW (1) TWI463701B (da) WO (1) WO2009115968A1 (da)

Cited By (21)

* Cited by examiner, â Cited by third party Publication number Priority date Publication date Assignee Title US20100244277A1 (en) * 2009-03-25 2010-09-30 Rui Huang Integrated circuit packaging system with package underfill and method of manufacture thereof US20110108865A1 (en) * 2009-11-06 2011-05-12 Koninklijke Philips Electronics N.V. Silicone based reflective underfill and thermal coupler US20120007119A1 (en) * 2010-07-08 2012-01-12 Shin-Etsu Chemical Co., Ltd. Light-emitting semiconductor device, mounted substrate, and fabrication method thereof CN102593317A (zh) * 2011-12-20 2012-07-18 è¥¿å®ç¬å ç§ææéå ¬å¸ ä¸ç§é«åçé«äº®åº¦ledå æºå°è£ ç»æåå ¶å°è£ æ¹æ³ CN102610703A (zh) * 2011-01-20 2012-07-25 éæ ç¾ å çµå ä»¶çå°è£ æ¹æ³ US20130119417A1 (en) * 2011-11-15 2013-05-16 Peter Scott Andrews Light emitting diode (led) packages and related methods US8796075B2 (en) 2011-01-11 2014-08-05 Nordson Corporation Methods for vacuum assisted underfilling US9022607B2 (en) 2012-10-18 2015-05-05 Avago Technologies General Ip (Singapore) Pte. Ltd. Leadframe-based surface mount technology segmented display design and method of manufacture US9412918B2 (en) 2012-07-19 2016-08-09 Nichia Corporation Light emitting device and method of manufacturing the same US9640709B2 (en) * 2013-09-10 2017-05-02 Heptagon Micro Optics Pte. Ltd. Compact opto-electronic modules and fabrication methods for such modules US20170250166A1 (en) * 2014-02-14 2017-08-31 Taiwan Semiconductor Manufacturing Company, Ltd. Thermal performance structure for semiconductor packages and method of forming same US9831104B1 (en) * 2015-11-06 2017-11-28 Xilinx, Inc. Techniques for molded underfill for integrated circuit dies WO2018162470A1 (de) * 2017-03-08 2018-09-13 Osram Opto Semiconductors Gmbh Verfahren zur herstellung von zumindest einem optoelektronischen bauelement und optoelektronisches bauelement US20180261715A1 (en) * 2015-05-13 2018-09-13 Koninklijke Philips N.V. Sapphire collector for reducing mechanical damage during die level laser lift-off US10453827B1 (en) 2018-05-30 2019-10-22 Cree, Inc. LED apparatuses and methods US10672957B2 (en) 2017-07-19 2020-06-02 Cree, Inc. LED apparatuses and methods for high lumen output density US10714359B2 (en) 2014-02-14 2020-07-14 Taiwan Semiconductor Manufacturing Company, Ltd. Substrate design for semiconductor packages and method of forming same CN111630645A (zh) * 2018-01-25 2020-09-04 æµæ¾å å­å­¦æ ªå¼ä¼ç¤¾ åå¯¼ä½è£ ç½®ãååå¯¼ä½è£ ç½®çå¶é æ¹æ³ US11024611B1 (en) * 2017-06-09 2021-06-01 Goertek, Inc. Micro-LED array transfer method, manufacturing method and display device US11101410B2 (en) 2018-05-30 2021-08-24 Creeled, Inc. LED systems, apparatuses, and methods US11311967B2 (en) * 2014-08-19 2022-04-26 Lumileds Llc Sapphire collector for reducing mechanical damage during die level laser lift-off

Families Citing this family (13)

* Cited by examiner, â Cited by third party Publication number Priority date Publication date Assignee Title US8952402B2 (en) * 2011-08-26 2015-02-10 Micron Technology, Inc. Solid-state radiation transducer devices having flip-chip mounted solid-state radiation transducers and associated systems and methods US10020431B2 (en) 2012-03-30 2018-07-10 Lumileds Llc Sealed semiconductor light emitting device JP2014179569A (ja) * 2013-03-15 2014-09-25 Nichia Chem Ind Ltd çºå è£ ç½®ããã³ãã®è£½é æ¹æ³ CN104600186A (zh) * 2013-10-31 2015-05-06 å±æ¶ç§æ(æ·±å³)æéå ¬å¸ åå äºæç®¡å°è£ ä½çå¶é æ¹æ³ JP2015220342A (ja) * 2014-05-19 2015-12-07 ä½åé»æ°å·¥æ¥­æ ªå¼ä¼ç¤¾ å åå°ä½è£ ç½®ã®è£½é æ¹æ³åã³å åå°ä½è£ ç½®ã®è£½é è£ ç½® US10170671B2 (en) * 2016-05-25 2019-01-01 Chen-Fu Chu Methods of filling a flowable material in a gap of an assembly module CN108630645A (zh) * 2017-03-17 2018-10-09 æ°¸éæ çº¿å°é¢æ ç­¾(æ¬å·)æéå ¬å¸ ä¸ç§è¯çåå¤©çº¿åºæçæ¥åç»æåå ¶å¶å¤æ¹æ³ CN107424964A (zh) * 2017-07-27 2017-12-01 æ­¦æ±å¸ä¸éç§ææéå ¬å¸ åºé¨å¡«å ç»æç©åä½¿ç¨å ¶ä¹åºé¨å¡«å æ¹æ³ä¸çµå­ç»è£ ç»ä»¶ JP7266178B2 (ja) * 2017-11-24 2023-04-28 æ¥äºåå­¦å·¥æ¥­æ ªå¼ä¼ç¤¾ åå°ä½è£ ç½®ã®è£½é æ¹æ³ KR20190084807A (ko) * 2018-01-09 2019-07-17 ìì¸ë°ì´ì¤ìì¤ ì£¼ìíì¬ ë°ê´ ì¥ì¹ US20210399041A1 (en) * 2020-06-18 2021-12-23 Seoul Semiconductor Co., Ltd. Light emitting module having a plurality of unit pixels, method of fabricating the same, and displaying apparatus having the same US20220149246A1 (en) * 2020-11-12 2022-05-12 Seoul Semiconductor Co., Ltd. Light emitting module and method of manufacturing the same and display apparatus having the same CN113524473B (zh) * 2021-07-09 2023-10-20 èå·æ¶æ¹åå¯¼ä½ç§æè¡ä»½æéå ¬å¸ å å­¦åºæ¿çåå²æ¹æ³

Citations (7)

* Cited by examiner, â Cited by third party Publication number Priority date Publication date Assignee Title US6274399B1 (en) * 1998-06-05 2001-08-14 Lumileds Lighting, U.S. Llc Method of strain engineering and impurity control in III-V nitride semiconductor films and optoelectronic devices US6649440B1 (en) * 1999-06-08 2003-11-18 Lumileds Lighting U.S., Llc Aluminum indium gallium nitride-based LED having thick epitaxial layer for improved light extraction US20050269582A1 (en) * 2004-06-03 2005-12-08 Lumileds Lighting, U.S., Llc Luminescent ceramic for a light emitting device US20060105485A1 (en) * 2004-11-15 2006-05-18 Lumileds Lighting U.S., Llc Overmolded lens over LED die US20060202223A1 (en) * 2005-03-09 2006-09-14 Gelcore Llc Increased light extraction from a nitride led US20060281203A1 (en) * 2005-06-09 2006-12-14 Lumileds Lighting U.S, Llc Method of removing the growth substrate of a semiconductor light emitting device US20070202623A1 (en) * 2005-10-28 2007-08-30 Gelcore Llc Wafer level package for very small footprint and low profile white LED devices

Family Cites Families (11)

* Cited by examiner, â Cited by third party Publication number Priority date Publication date Assignee Title US6506681B2 (en) * 2000-12-06 2003-01-14 Micron Technology, Inc. Thin flipâchip method JP2003197680A (ja) * 2001-12-25 2003-07-11 Matsushita Electric Works Ltd åå°ä½è£ ç½®ã®è£½é æ¹æ³ US7138293B2 (en) * 2002-10-04 2006-11-21 Dalsa Semiconductor Inc. Wafer level packaging technique for microdevices US6977396B2 (en) * 2003-02-19 2005-12-20 Lumileds Lighting U.S., Llc High-powered light emitting device with improved thermal properties RU2267188C2 (ru) * 2003-06-23 2005-12-27 Ð¤ÐµÐ´Ð¾ÑÐ¾Ð²Ð° ÐÐ°Ð»Ð¸Ð½Ð° ÐÐ»Ð°Ð´Ð¸Ð¼Ð¸ÑÐ¾Ð²Ð½Ð° Ð¡Ð²ÐµÑÐ¾Ð´Ð¸Ð¾Ð´Ð½Ð¾Ðµ Ð¿Ð¾Ð»ÑÐ¿ÑÐ¾Ð²Ð¾Ð´Ð½Ð¸ÐºÐ¾Ð²Ð¾Ðµ ÑÑÑÑÐ¾Ð¹ÑÑÐ²Ð¾ Ð² ÐºÐ¾ÑÐ¿ÑÑÐµ Ð´Ð»Ñ Ð¿Ð¾Ð²ÐµÑÑ Ð½Ð¾ÑÑÐ½Ð¾Ð³Ð¾ Ð¼Ð¾Ð½ÑÐ°Ð¶Ð° JP3876250B2 (ja) * 2003-06-24 2007-01-31 ã¹ã¿ã³ã¬ã¼é»æ°æ ªå¼ä¼ç¤¾ è¡¨é¢å®è£ ååå°ä½é»å­é¨åããã³è£½é æ¹æ³ JP4608966B2 (ja) * 2004-06-29 2011-01-12 æ¥äºåå­¦å·¥æ¥­æ ªå¼ä¼ç¤¾ çºå è£ ç½®ã®è£½é æ¹æ³ CN101138094B (zh) * 2005-03-09 2010-10-13 æ­åæçµå­ææå ä»¶æ ªå¼ä¼ç¤¾ å å­¦å¨ä»¶åå å­¦å¨ä»¶çå¶é æ¹æ³ DE112006001835T5 (de) * 2005-07-11 2008-05-15 GELcore, LLC (n.d.Ges.d. Staates Delaware), Valley View Laserabgehobene LED mit verbesserter Lichtausbeute JP5192646B2 (ja) * 2006-01-16 2013-05-08 ï¼´ï½ï½ï½æ ªå¼ä¼ç¤¾ å ç´ å­ã®æ¨¹èå°æ­¢æ¹æ³ããã®æ¨¹èå°æ­¢è£ ç½®ãããã³ããã®è£½é æ¹æ³ US7867793B2 (en) * 2007-07-09 2011-01-11 Koninklijke Philips Electronics N.V. Substrate removal during LED formation

2008

2008-03-17 US US12/050,082 patent/US20090230409A1/en not_active Abandoned

2009

2009-03-13 JP JP2011500333A patent/JP5372133B2/ja active Active

2009-03-13 EP EP09722834.0A patent/EP2266149B1/en active Active

2009-03-13 RU RU2010142267/28A patent/RU2502157C2/ru active

2009-03-13 CN CN2009801094605A patent/CN102084505B/zh active Active

2009-03-13 KR KR1020107023171A patent/KR101524004B1/ko active IP Right Grant

2009-03-13 BR BRPI0909788-0A patent/BRPI0909788B1/pt active IP Right Grant

2009-03-13 WO PCT/IB2009/051055 patent/WO2009115968A1/en active Application Filing

2009-03-16 TW TW098108499A patent/TWI463701B/zh active

2011

2011-05-25 US US13/115,475 patent/US8273587B2/en active Active

Patent Citations (7)

* Cited by examiner, â Cited by third party Publication number Priority date Publication date Assignee Title US6274399B1 (en) * 1998-06-05 2001-08-14 Lumileds Lighting, U.S. Llc Method of strain engineering and impurity control in III-V nitride semiconductor films and optoelectronic devices US6649440B1 (en) * 1999-06-08 2003-11-18 Lumileds Lighting U.S., Llc Aluminum indium gallium nitride-based LED having thick epitaxial layer for improved light extraction US20050269582A1 (en) * 2004-06-03 2005-12-08 Lumileds Lighting, U.S., Llc Luminescent ceramic for a light emitting device US20060105485A1 (en) * 2004-11-15 2006-05-18 Lumileds Lighting U.S., Llc Overmolded lens over LED die US20060202223A1 (en) * 2005-03-09 2006-09-14 Gelcore Llc Increased light extraction from a nitride led US20060281203A1 (en) * 2005-06-09 2006-12-14 Lumileds Lighting U.S, Llc Method of removing the growth substrate of a semiconductor light emitting device US20070202623A1 (en) * 2005-10-28 2007-08-30 Gelcore Llc Wafer level package for very small footprint and low profile white LED devices

Cited By (36)

* Cited by examiner, â Cited by third party Publication number Priority date Publication date Assignee Title

Also Published As

Publication number Publication date RU2502157C2 (ru) 2013-12-20 BRPI0909788B1 (pt) 2019-11-05 EP2266149B1 (en) 2017-08-23 US8273587B2 (en) 2012-09-25 KR101524004B1 (ko) 2015-05-29 JP5372133B2 (ja) 2013-12-18 KR20100129771A (ko) 2010-12-09 TW200950158A (en) 2009-12-01 CN102084505B (zh) 2013-05-01 BRPI0909788A2 (pt) 2015-10-06 US20110223696A1 (en) 2011-09-15 RU2010142267A (ru) 2012-04-27 WO2009115968A1 (en) 2009-09-24 JP2011514688A (ja) 2011-05-06 EP2266149A1 (en) 2010-12-29 TWI463701B (zh) 2014-12-01 CN102084505A (zh) 2011-06-01

Similar Documents

Publication Publication Date Title US8273587B2 (en) 2012-09-25 Underfill process for flip-chip LEDs US8431423B2 (en) 2013-04-30 Reflective substrate for LEDS US20110049545A1 (en) 2011-03-03 Led package with phosphor plate and reflective substrate EP2812929B1 (en) 2020-03-11 Molded lens forming a chip scale led package and method of manufacturing the same TWI437724B (zh) 2014-05-11 åºæ¿åé¢ä¹å¼·å¥ç¼å äºæ¥µé«çµæ§ EP2168178B1 (en) 2019-03-20 Substrate removal during led formation KR100990635B1 (ko) 2010-10-29 ìì§êµ¬ì¡° ë°ê´ë¤ì´ì¤ë ììì ì ì¡°ë°©ë² JP5816508B2 (ja) 2015-11-18 åå°ä½çºå è£ ç½®ã®è£½é æ¹æ³

Legal Events

Date Code Title Description