KR100726967B1 - LED packaging without wire bonding - Google Patents

Abstract

 The present invention relates to a specimen bonding method without applying a wire bonding method from a submount when connecting a foot and a diode element mounted in a flip-chip bonding method on a submount with a wiring board. The high temperature heat generated from the high power light emitting diode is transferred to the bonding wire and the sub-mount, and the problem of disconnection due to heat stress can be improved by applying the specimen bonding method, and the flip-chip mounted on the submount Even light emitting diodes can be packaged without the use of wire bonding equipment. A submount with sidewalls plated for the specimen bonding method, a flip chip light emitting diode mounted with solder bumps or studs on the submount, a bonding specimen for electrically connecting the submount and the wiring board, and a bonding formed on the wiring board connected to the bonding specimen Pads, a thermally conductive adhesive for mounting the submount on the wiring substrate, a thermal adhesive cup formed to contain the thermal conductive adhesive in the wiring substrate, and a specimen between the anode and cathode bonding pads of the light emitting diode in the thermal adhesive cup. It is characterized by having a dam preventing a short circuit.

 Specimen Bonding, Light Emitting Diodes, Submount, Wire Bonding, Flip Chip Bonding

Description

Light emitting diode packaging without wire bonding method {Wireless Bonding Method in LED Packaging}

1 is a perspective view of a wire bonding method according to the prior art.

2 to 4 is a cross-sectional view of the package using the wire bonding according to the prior art.

5A to 5C are cross-sectional views of a light emitting diode package not applying a wire bonding method according to an embodiment of the present invention.

6A to 6I are manufacturing process diagrams of a light emitting diode package not applying a wire bonding method according to an embodiment of the present invention.

FIG. 7 is a detailed view of FIG. 6I in accordance with an embodiment of the present invention. FIG.

8A through 8C illustrate various forms of a metal substrate or a high heat radiation dielectric ceramic according to an embodiment of the present invention.

{Description of the symbols for the main parts of the drawing}

501: Fragment Bonding 502: flip chip light emitting diode.

502a: Solder and Stud bumps.

503: sidewall plated submount 504: sidewall to plated submount.

505: Dam to prevent short circuit between anode and cathode.

506: insulation layer.

507: adhesive with improved thermal properties for bonding sub-mounts and wiring boards and thermal adhesive cups containing the adhesive

508: bonding pads to which a bond specimen connected to a submount is connected to a wiring board.

509: insulating layer of the wiring board

510: interlayer via hole with pad for connecting signal to outside of back side of wiring board

511: reflecting cup 512: metal layer on the bottom of the heat adhesive cup

The present invention relates to a specimen bonding method without applying a wire bonding method from a submount when a light emitting diode device mounted in a flip-chip bonding method on a submount is connected to a wiring board.

High power light emission diodes (hereinafter referred to as LEDs) are required to have high brightness, high lifetime, and high reliability, and performance and characteristics are determined by color temperature, brightness, and luminance intensity range. In order to improve the light extraction efficiency, there is a method of increasing the crystal growth of the active layer, the electron injection (N) layer, and the hole injection (P) layer of the light emitting diode device. The performance is determined by the controllable wiring structure and the bonding method for connecting the device and the wiring board. In order to realize high light emission characteristics, the material properties of compound semiconductors are greatly influenced, but various limitations are imposed on fabrication. Accordingly, research on package structure is being actively conducted.

It is most important for the light emitting diode to obtain high life and high reliability while maintaining its characteristics. To this end, high-power LEDs are mounted on submounts by flip-chip bonding to submounts to improve heat dissipation while improving optical properties, and the submounts are electrically connected through wire bonding and adhesives are applied to the wiring board. The mounting method used has been developed in the same manner as in FIG. 1, and in order to improve the heat dissipation characteristics at the packaging level, the surface-mounted device (SMD) has been developed in the same manner as in FIGS. Has been.

1 shows an electrode pad formed on a flip chip light emitting diode 101, and the electrode pad is mounted on a submount 103 on which electrodes are formed using solder bumps and stud bumps 102. The wire is bonded 104 to the bonding pad 106 of the wiring board 107 by mounting. The submount was bonded onto the wiring board using an adhesive 105 having good thermal conductivity. Heat generated from the flip chip light emitting diode is transferred to the electrode pad of the submount through the solder bumps, and is discharged to the wiring board at the bottom of the submount, but the gold in the submount is lower than that of the submount having the crystal structure. The transfer is first made to the plated electrode pads so that the medium is transferred to the bond wire 104 made of gold. If the input periodically turns on / off a large power source to obtain a high output signal of light, the backlash of heat transfer occurs as a stress due to the heat transfer barrier layer present in the package, causing TiW / Au. The bond wire bonded to the interface of the sub-mount electrode pads and the bond wires bonded to the interface of the bond pads of the wiring board of Cu / Ni / Au fall due to thermal stress, or the bond wire is broken by an additional phenomenon, thereby The disconnection phenomenon will occur.

2, 3, and 4 show the LED elements 201a, 301a, and 401a attached to the heat dissipating slugs 201c, 301d, and 401d using the adhesives 201b, 301b, and 401b having improved solder and thermal conductivity. It is attached on the wiring board using adhesives (301d, 401e, 501f) with improved thermal conductivity, and the wiring board is made of aluminum (Al) or copper (Cu), ceramics having high thermal conductivity (SiC, AlN, AlSiC). The insulating layers 202, 303, and 403 were laminated on the heat diffusion substrates 204, 304, and 404 of the same material as the wiring layers 203, 302, and 402 so as not to be conductive. The wiring board and the heat dissipating slugs 201c, 301d, and 401d are attached using adhesives or solders 201d, 301e, and 401f having improved thermal conductivity, and the reflecting cups have a light distribution angle and luminance of the light emitting diode. It is attached to improve the properties. Heat generated from the light emitting diode is simultaneously emitted by three methods such as conduction, convection, and radiation. Since the heat transfer is performed in the order of the high thermal conductivity of the medium connected to the light emitting diode, the thermal conductivity is 0.024 W / mK (@ The amount of conduction delivered into the package consisting of conductors and semiconductors with high thermal conductivity is much greater than the amount of convection and radiation out of the package consisting of air. Therefore, the heat dissipation in the package has priority over conduction. In heat dissipation, the principle of conduction in which heat is transferred to a constant transfer area follows Fourier's law. The thermal conductivity is as follows.

Here, q can be seen that the heat transfer rate is proportional to the thermal conductivity ( k ), area ( A ), and temperature change ( dT / dx ) according to the distance of the conducting medium.

If the material has a low thermal conductivity material and a narrow space on a path through which heat is released, the thermal conductivity decreases, and thermal fatigue accumulates in the LED. When electrons are injected into the N layer in the LED, scattering due to collision occurs on the lattice of the semiconductor, and lattice scattering increases as the temperature increases. Accordingly, the mobility of the electrons and the magnitude of the forward voltage and the current are reduced, and the coupling and recombination of the holes are reduced, which greatly affects the decrease in light output and the operation of the LED. At this time, a layer having a relatively thick thickness and a low thermal conductivity coefficient as a barrier layer acts as a barrier layer in the path of dissipating heat through conduction. The P layer and the N layer located above and below the multi quantum well structure (MQW, Multi Quantum Well) are 0.1 to 4 μm, and the heat conduction coefficient is 130 W / mK, which enables relatively fast heat transfer, but the thickness of the solder bumps And the heat conduction coefficients are 20 to 60㎛ and 50 W / mK, respectively, and the heat dissipation path is relatively long and the heat conduction coefficient is low. The sub-mount is commercially applied to Si the most, the thermal conductivity is different depending on the doping concentration, but generally has a high characteristic of 150 W / mK, while the thickness is 200 ~ 300㎛ of the chip that generates heat The path of spreading and dissipating heat to area is relatively narrow and long. 2, 3, and 4 have three or more barrier layers having low thermal conductivity during the transfer of the heat emission diffusion substrates 204, 304, and 404 from the LEDs. The first barrier layer is the thermally conductive adhesive 201d, 301e, 401f attaching the LED elements 201a, 301a, 401a and the heat dissipating slugs 201c, 301d, 401d of FIGS. ), The thermal conductivity is 0.3 W / mK ~ 1 W / mK range, the bonding thickness is 50 ~ 150㎛. The second barrier layer is solder or adhesive (201d, 301e, 401f) for attaching the heat dissipating slug and the wiring layer (203, 302, 402) of the wiring board. The solder has a thermal conductivity of 37 according to the ratio of tin (Sn) and lead (Pb). The thermal conductivity of the adhesive which was distributed between W / mK to 55 W / mK and increased the thermal conductivity was in the range of 0.3 W / mK to 1 W / mK, and the bonding thickness was 50 to 100 µm. The third barrier layer is an insulating layer 202, 303, 403 of the wiring board, and has a thermal conductivity of 0.35 to 23 W / mK and a thickness of 50 mu m or more. In general, the barrier layer is composed of three to five layers in heat transfer, which greatly influences the junction temperature rise of the LED device depending on the type, thickness, and structure of the heat transfer medium. In particular, there are many bonding layers with low thermal conductivity and The thicker and smaller the area, the narrower and longer the heat transfer path, which acts as a barrier to heat release. Therefore, due to the increase in junction temperature and poor heat transfer by the barrier layer, the wire bonding connecting the electrical wiring signal to the wiring board and the objects interposed between the barrier layer is caused by thermal fatigue. The junction interface and the bond wire intermediate point may cause a break in thermal expansion and contraction at the two interfaces. In high power light emitting diodes, problems with long-term operation and performance and reliability are deteriorated without effective measures for heat dissipation.

The present invention has been made to solve the above problems, the object is to improve the reliability of the package by preventing the disconnection of the bond wire due to the thermal stress by the barrier layer of the heat and emission process to the light emitting diode, It is to provide an LED package that can reduce the manufacturing cost and the process cost by applying a simple bonding method using a specimen without wire bonding equipment.

In order to achieve the above object, a light emitting diode packaging that does not apply the wire bonding method of the present invention may include a submount plated so that sidewalls may have electrical conductivity; A flip chip light emitting diode mounted on the submount in a flip chip manner; A wiring board having a heat diffusion adhesive cup for burying an adhesive having high thermal conductivity and electrical non-conductivity for mounting the submount; A specimen for connecting the sidewall of the submount and the bonding pad of the wiring board; A dam for preventing a short circuit between the positive electrode and the negative electrode formed in the heat spreading adhesive cup; A metal layer formed under the heat spreading adhesive cup; And a via hole for connecting a signal to the outside of the rear surface of the wiring board.

In the present invention, further comprising an insulating layer filling the upper and lower layers of the wiring board and the metal layer of the bottom, the insulating layer is preferably used at least one material selected from ceramic, FR-4, epoxy.

In the present invention, the insulating layer preferably has a thickness of 50㎛ or more.

In the present invention, it is preferable that the wiring board further includes a heat dissipation plate processed in an embossed form in order to increase the heat dissipation characteristics to the back of the wiring board.

In the present invention, the light emitting diode and the submount are preferably bonded using solder and stud bumps.

In the present invention, the heat diffusion adhesive cup is preferably formed by step machining on the wiring board.

In the present invention, the specimen is preferably formed by discharging a conductive adhesive having a high viscosity.

In the present invention, the specimen bonding is preferably formed using a soldering method using solder paste.

In the present invention, it is preferable that the protrusion of the heat dissipation substrate is inserted into the wiring board on which the cavity is formed at the lower end of the heat diffusion adhesive cup in order to improve the heat dissipation characteristics.

In the above, the electrode pad formed in the sub-mount is separated from the anode and the cathode (Cathode), and is not limited in the slope of the side wall to be plated, only the anode and the cathode should not be a short circuit. The plating material has electrical conductivity and is not limited in kind.

In the method of forming the thermal adhesive cup, both the bond pad and the metal layer forming the bottom of the thermal adhesive cup are filled with an insulating medium, and only the form of the thermal adhesive cup is burned using a laser corresponding to an infrared wavelength, and the insulating medium is burned off. As a method, the dam, the bond pads and the bottom metal layer are formed. It is also preferable to apply the method of processing by using a laser after the first boiling by mechanical processing method.

In addition, by mixing a chemical method and a mechanical method, the metal layer at the bottom of the thermal adhesive cup is buried in advance, the photosensitive insulating layer on the bond pad bonded to the specimen is applied, and then exposed to ultraviolet light to expose the bond pad area. And a portion where the thermal adhesive is buried, and the insulating layer formed on the metal layer of the bottom of the thermal adhesive cup may be burned using a laser.

The thermal adhesive is electrically non-conductive and has high thermal conductivity so that a short circuit with the plating layer of the submount sidewall does not occur.

The specimen has a high electrical conductivity so as to be short-circuit with the submount sidewall and the bonding pad of the wiring board, and the forming method is a high viscosity adhesive stock solution using a dispensing machine to bond the sidewall of the submount and the bonding pad of the wiring board. It forms by pouring after pouring in between.

It is also preferable to form a solder paste at a high temperature by pouring or printing a solder paste composed of a solder ball larger than a gap formed in a thermal adhesive cup and a gap of a submount attached to the thermal adhesive.

In addition, a solid solder specimen may be fabricated and placed between the sub-mount sidewall and the bonding pad of the wiring board to be soldered at a high temperature.

The dam formed in the thermal adhesive cup is formed at the same time as the insulating material as the thermal adhesive cup is formed, the distance between the dam formed on both sides is larger than the size of the sub-mount, but smaller than the size of several solder balls constituting the solder paste .

The metal layer formed on the bottom of the thermal adhesive cup is formed in advance before lamination in a multilayer when forming a wiring board, and serves as a resist to prevent the bottom of the metal layer from being processed during laser processing, and applied to the top of the metal layer. Alternatively, the depth of the thermal adhesive cup can be adjusted as the thickness of the insulating material to be bonded.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In adding reference numerals to components of the following drawings, it is determined that the same components have the same reference numerals as much as possible even if displayed on different drawings, and it is determined that they may unnecessarily obscure the subject matter of the present invention. Detailed descriptions of well-known functions and configurations will be omitted.

5A to 5C are a perspective view and a cross-sectional view of the LED package according to an embodiment of the present invention.

In this embodiment, the LED package includes a flip chip light emitting diode 502; Solder and stud bumps 502a for mounting flip chips on the sub-mounts; Fragment Bonding 501 for connection with the bonding pads of the wiring board and the sidewalls of the submount; A submount 503 with sidewalls plated thereon; Sidewalls 504 on the plated submount; A dam 505 for preventing a short circuit between the positive electrode and the negative electrode; An insulating layer 506 for preventing a short circuit between the reflective cup 511 and the bonding pad and wiring of the upper layer; an adhesive having improved thermal properties for bonding the sub mount and the wiring board, and a thermal adhesive cup containing the adhesive ( A bonding pad 508 to which a bond specimen connected to the sub mount is connected to the wiring board; An insulating layer 509 filling the upper and lower layers of the wiring board and the metal layer at the bottom of the heat adhesive cup; An interlayer connection via hole 510 with a pad for connecting a signal to the outside of the back surface of the wiring board; A reflective cup 511 reflects light emitted from the light emitting diode and a metal layer at the bottom of the thermal adhesive cup.

The above embodiment schematically shows a configuration in which the light emitting diodes are bonded without wires.

The insulating layer 509 of the wiring board has a thickness of 50 μm or more as LTCC and HTCC, an interlayer insulating material of PCB, FR-4, and epoxy, and the wiring layer may be formed of both sides and a multilayer board.

The specimen bonding reflows the high viscosity solder paste while dispensing and maintaining the shape using a dispensing machine. Sn / Pb specimens of a certain size are processed and placed between the Si submount and the bonding pads for reflow. It is also preferable to cure the conductive organic paste while discharging and maintaining the shape using a dispensing machine.

The dielectric layer is applied or laminated to a certain thickness. As the organic material, it is preferable to use an organic material as epoxy, which is a main material of epoxy or PCB, and as the inorganic material, a ceramic material which can be applied to LTCC / HTCC is preferable.

The dam is formed using a PCB or LTCC. In the case of using the PCB, a resist metal P / T is formed on the bottom of the dielectric layer to perform laser drilling, or in the case of using SR ink, curing and shape are formed by photo imaging to form a bonding pad.

When the LTCC is used, the green sheet is processed in advance and bonded or laser drilling is used.

Hereinafter, the configuration of the present invention through the manufacturing method of the LED package in more detail.

First, a raw material 601 is prepared by PCB or LTCC (FIG. 6A). A trench is then formed 602 which is a predetermined space underneath the material 601 (FIG. 6B). As the trench forming method, it is preferable to use a punching method using a pin or a drill method.

Thereafter, a predetermined electrode 603 is patterned on the material, and a via hole is formed below the patterned electrode (FIG. 6C). The via hole is preferably formed through drilling or punching.

Next, a thermal paste cup 604 is formed on the material on which the electrode is patterned, and a hole or a trench is formed in the center (FIG. 6D). The paste cup is formed by a laser drilling method, and the central hole or trench is preferably formed by laser or mechanical drill and milling.

Thereafter, the PCB or LTCC material is removed, and a metal substrate 605 is assembled to the center of the hole or trench (FIG. 6E). <Deleted> In order to insert the heat radiating plate processed into the embossed shape on the wiring board to enhance the characteristics of heat dissipation on the back side of the wiring board, it is formed in the same shape as the heat radiating plate and the sidewalls are plated and soldered using solder ( Soldering, brazing, or bonding using an adhesive is applied. At this time, the metal layer of the bottom of the thermal adhesive cup does not need to be formed during the manufacture of the wiring board. By adjusting, the depth of the heat adhesive cup can be adjusted.

Next, a thermal paste 607 is applied to a portion where the hole or trench is formed (FIG. 6F). The thermal paste is preferably an electrically nonconductive material and is made of a material having high thermal conductivity.

Thereafter, a flip chip LED 608 including a submount is mounted in the hole or trench (FIG. 6G). The flip chip LED including the submount and the method of stacking on top of the thermal paste are shown in detail in FIG. 5B. Solder and stud bumps are provided between the flip chip LED bottom and the sub-mount, and are attached without a separate wire.

After the flip chip LED including the submount is mounted, a specimen adhesion 609 is performed for connection with the wiring electrode (FIG. 6H). The specimen is formed for connection with the via hole formed above, and the reflector 610 is laminated after the specimen is bonded (FIG. 6I).

7 is an enlarged view of a reflector according to an embodiment of the present invention. The reflector is for reflecting the light emitted from the LED to be efficiently radiated and is preferably stacked on the thermal paste. When the solder paste is used, the solder paste is embedded between the bonding pad and the sub-mount of the wiring board by high temperature soldering.

8A to 8C are cross-sectional views of a metal substrate or a high temperature dielectric ceramic in FIG. 6E according to an embodiment of the present invention.

8A is the same as the metal substrate formed in FIG. 6F.

Referring to FIGS. 8A and 8C, in order to improve heat dissipation characteristics on the back surface of a wiring board, a buried via hole is processed in the wiring board to fill the via hole with a high thermally conductive filler, and the conductive via hole is plated thereon. The upper and lower layers are coated or laminated with an insulating material, and the upper layer is processed to a heat adhesive cup for attaching a sub-mount, and the lower layer is processed to allow heat to escape to the outside.

As described above, it has been described with reference to the preferred embodiment of the present invention, but those skilled in the art various modifications and changes of the present invention without departing from the spirit and scope of the present invention described in the claims below I can understand that you can.

As described above, according to the present invention, the reliability of the package is improved by preventing the disconnection of the bond wire due to the thermal stress caused by the barrier layer during the heat and emission to the light emitting diode, and the simple bonding method using the specimen without the wire bonding equipment. By applying this, manufacturing cost and process cost can be reduced.

Claims (10)

A submount plated such that the sidewalls are electrically conductive; A flip chip light emitting diode mounted on the submount in a flip chip manner; A wiring board having a heat diffusion adhesive cup for burying an adhesive having electrical non-conductivity for mounting the submount; A specimen formed by discharging a conductive adhesive to connect the sidewall of the submount and the bonding pad of the wiring board; A dam for preventing a short circuit between the positive electrode and the negative electrode formed in the heat spreading adhesive cup; A metal layer formed under the heat spreading adhesive cup; And a via hole for connecting a signal to an outside of a rear surface of the wiring board. The LED package of claim 1, further comprising an insulating layer filling the upper, lower, and bottom metal layers of the wiring board. 3. The LED package of claim 2, wherein the insulating layer uses at least one material selected from ceramic, FR-4, and epoxy. The light emitting diode packaging of claim 2, wherein the insulating layer has a thickness of 50 µm or more. 2. The LED package of claim 1, wherein the wiring board further comprises a heat dissipation plate processed in an embossed form in order to increase heat dissipation characteristics on the back surface of the wiring board. The LED package of claim 1, wherein the wiring board is provided with a buried via hole formed in a lower end portion of a heat spreading adhesive cup to increase heat dissipation. The light emitting diode packaging of claim 1, wherein the heat diffusion adhesive cup is formed on the wiring board through stepwise processing. delete 2. The light emitting diode packaging of claim 1, wherein the specimen bonding is performed using a soldering method using solder paste. The LED package of claim 1, wherein a protrusion of the heat dissipation substrate is inserted into a wiring board having a cavity formed at a lower end portion of the heat spreading adhesive cup to improve heat dissipation characteristics.

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