JP2001223391A - Forming method of light-emitting diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming method of a flip-chip type light-emitting diode where in the junction between an electrode of an LED chip and a lead electrode of a package is stabilized while thickness as a light-emitting diode is reduced for significantly improved mass-production efficiency as well as lower production cost. SOLUTION: A part of the lead electrode is pressurized to raise other part, thus forming a protrusion for connection between the protrusion and the electrode of LED chip. Related to the junction between the electrode of LED chip and the lead electrode, the LED chip is fixed by melting/coagulation of a solder- plating, a cream solder, or a solder ball applied on the surface of lead electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a light emitting diode in which an LED chip is disposed on a package having a pair of lead electrodes, and more particularly to a method for forming a projection on a part of each of the lead electrodes. And a method for forming a light emitting diode having the same.

[0002]

2. Description of the Related Art Light emitting diodes are small and efficient.
It emits bright colors. In addition to low power consumption,
Since it is a semiconductor element, there is no fear of breaking the ball. It has excellent initial drive characteristics and is resistant to vibration and ON / OFF lighting. For these reasons, light emitting diodes have recently been used as various light sources in various fields in recent years. In particular, a light-emitting diode having a structure (flip chip type) in which an LED chip is mounted so that a surface on an active layer side formed on a semiconductor film-forming substrate and a package on which the LED chip is arranged faces each other is an LE.
Since the surface opposite to the active layer surface formed on the semiconductor film formation substrate of the D chip faces the upper surface of the light emitting diode, the effect of radiating the heat in the chip to the upper side of the light emitting diode is high. Since power consumption is possible, it is widely used. Also, because the LED chip electrode and the lead electrode of the package are directly connected, there is no need to wire bond using gold wire when electrically connecting the chip. It is easily mass-produced and is frequently used in a wide range of fields, for example, because a light emitting diode having a thickness as small as possible can be achieved.

[0003] In recent years, as described above, L
As an ED light emitting device, a package having substantially the same size as an LED chip, a so-called CSP (Chip Sc)
are attracting attention. An example is shown in FIG. Conventionally, as the CSP, there is a method formed by using a flip chip connection method (face down bonding method) as described in detail below.

[0004] First, a projection (bump) is formed by plating or attaching a gold ball (56) to a metal pad of a chip in a wafer state, and then separated into individual chips by dicing. Also, on the package 53 on which the chip 51 is arranged, solder bumps 57 are formed at positions corresponding to the metal pads.

Next, the package is fixed on a flip chip bonder table by suctioning air, and at the same time, the chip is also fixed to a surface (chip) opposite to the active layer surface formed on the semiconductor film forming substrate. (Back side) is suctioned and held by the holder of the flip chip bonder. Then, the holder side is slowly brought close to the table, and the bumps 56 on the chip side are moved.
And the bumps 57 on the package side are opposed to each other, and are closely contacted and pressurized with each other in position, and are passed through a reflow furnace set at a melting temperature of both bumps to actually join the two bumps. Thereafter, the resin 58 is cooled, and a gap formed between the chip and the package, that is, a space having a height corresponding to both bumps is filled with the resin 58 by using a capillary phenomenon. In this way, a CSP having substantially the same size as the chip is formed. Further, thereafter, the entire LED chip may be sealed with the translucent resin 55 for the purpose of protecting the LED chip from the outside, extracting light from the chip evenly to the outside, or the like.

[0006]

However, in the light emitting diode formed by the above-described method, the gap between the chip and the package is filled with resin to reduce the stress applied to the joint between the two bumps. Although it is possible, it takes a very long time to inject the resin into the gap by utilizing the capillary phenomenon or the like, which hinders improvement in mass productivity. When the entire LED chip is further sealed with a translucent resin after filling the gap with a resin,
The resin injection process involved two steps and was not efficient in the mass production process.

In particular, when gold plating is used for the bumps on the LED chip side, the strength of the joint with the solder bump on the package side is liable to decrease, and the wet state deteriorates, so that the bonding becomes unstable. There is a need to inject a resin into the joint to protect and stabilize the joint.

Further, the bumps have a thickness of 15 to 30 μm and are generally formed by electroplating. In this way, the bumps are formed by thin film deposition, photolithography, etching and plating steps. Therefore, a reduction in yield and an increase in bump formation cost were unavoidable. In addition, when bumps are formed on both the chip and the package electrodes, it takes a very long time, and efficient mass production is impossible.

Further, when bumps are formed on both the chip and package electrodes, not only the time required for the bump formation process is increased, but also the gap formed between the chip and the package becomes large, and the thickness of the light emitting diode is reduced. The original purpose of the chip type light emitting diode cannot be sufficiently fulfilled.

Therefore, according to the present invention, a bump-like projection can be easily formed on a lead electrode of a package on which an LED chip is arranged without using the above-described bump formation method. It is an object of the present invention to provide a method for forming a light emitting diode, which can realize a reduction in thickness and can further improve mass productivity remarkably.

[0011]

In order to achieve the above object, the present inventor has proposed a package having a pair of lead electrodes and a flip chip type which is disposed on the pair of lead electrodes and electrically connected thereto. An LED chip and the L
A method of forming a light emitting diode having a light-transmitting resin that covers an ED chip, wherein the LED chip is formed on a protrusion formed by pressing a part of each of the lead electrodes to protrude the other part. And a method for forming a light emitting diode, wherein the electrodes are arranged. The method for forming a light emitting diode includes a package having at least a pair of lead electrodes and an LED chip disposed on and electrically connected to the lead electrode, wherein the LED chip is electrically connected to the LED chip. Forming a projection on the surface of each lead electrode by pressing a part of each of the lead electrodes to be electrically connected to each other to form a protrusion on the surface of each lead electrode;
A method for forming a light emitting diode, comprising: fixing a D chip; and arranging a light-transmitting resin on the LED chip. Further, a pair of lead electrodes formed on a surface of the package are plated with solder. A method of forming a light emitting diode, characterized in that the bonding portion between the lead electrode and the LED chip fixes the LED chip by melting and solidifying the solder plating. Also, a pair of lead electrodes formed on the package surface are plated with gold having a thickness of 1 μm or less, and solder balls are supplied to the surface of the lead electrode using cream solder or flux. Is a method for forming a light emitting diode, wherein the LED chip is fixed by melting and solidifying the solder.

Specifically, according to the present invention, a pair of lead electrodes is formed on a package in which an LED chip is arranged, and then a part of the lead electrode is pressed by using a convex punch (pressing piece) to form another part. This is a method of forming bump-like projections by protruding. This eliminates the need to form bumps through a special process as in the past,
It is possible to easily form bump-like projections,
Mass production efficiency can be significantly improved.

The LED chip is directly connected to the lead electrode of the package, and the joint portion is fixed by melting and solidifying the solder plating applied to the lead electrode, or gold plating having a thickness of 1 μm or less. A solder ball is further applied to the surface of the lead electrode which has been subjected to soldering using cream solder or flux, and the solder is melted and solidified to fix the LED chip, which is different from the conventional case where both bumps are connected to each other. As a result, the area of the joint can be widened, so that the sense of stability of the joint increases, and it is not necessary to inject resin for reinforcing the joint into the gap formed between the LED chip and the package. Therefore, even when the entire LED chip is sealed using a translucent resin, the work process of resin injection does not extend to two steps.

Further, no protrusion is formed on the electrode on the chip side, and a protrusion is formed only on the electrode on the package side to form an LE.
The original purpose of the flip-chip type light-emitting diode is to directly connect with the electrode of the D-chip, not only to improve the efficiency of the work process but also to reduce the gap between the LED chip and the package and to make it thinner as a light-emitting diode. I can fulfill it enough. In today's world where light-emitting diodes are used as various light sources in various fields, their use and range can be further expanded if they are made thinner. ADVANTAGE OF THE INVENTION According to this invention, as a light source incorporated in various small apparatuses, such as a portable printer and a scanner, and a backlight, a light emitting diode thinner than the present can be provided, and they realize further miniaturization of the small apparatus itself. Can be done.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 4, but is not limited thereto.

First, as a light emitting element, the main light emission peak is 47
A GaInN semiconductor of 0 nm was used. LED chip,
TMG (trimethyl gallium) gas, TMI (trimethyl indium) gas,
It was formed by flowing a nitrogen gas and a dopant gas together with a carrier gas and forming a gallium nitride-based compound semiconductor by MOCVD. S as dopant gas
By switching between iH ₄ and Cp ₂ Mg, a gallium nitride-based semiconductor having n-type conductivity and a gallium nitride-based semiconductor having p-type conductivity were formed, and a pn junction was formed. (Note that the p-type semiconductor was annealed at 400 ° C. or higher after film formation.) After exposing the respective pn semiconductor surfaces by etching, each electrode was formed by a sputtering method. After a scribe line was drawn on the semiconductor wafer thus completed, the wafer was divided by an external force to form LED chips 11 of 250 μm square as light emitting elements.

Next, a molding resin is injected into the inside of the mold using a mold, molded, and taken out of the mold after cooling, whereby the package 13 is formed. Then, a pair of lead electrodes 1
4 was formed along the surface of the package 13 using three-dimensional plating, and further, solder plating 25 was applied to the surface of the lead electrode using a solder plating apparatus. The package 23 (FIG. 2) having a pair of lead electrodes thus formed is heated, and as shown in FIG. 2A, a pressing piece (convex punch) 26 is pressed between the formed two electrodes a.
Is lowered from above the package, and is moved several times in the left-right direction (arrow direction) of the package so as to press both lead electrodes 24 before the heat of the lead electrodes cools. By this operation, the pressurized portion of the lead electrode rises, and FIG.
16A which is a part of the lead electrode 14 of FIG.
The projection for directly connecting the electrode of the LED chip and the lead electrode of the package can be formed very easily.

Such a projection may alternatively be provided in FIG.
As shown in FIG. 2, a package 2 having a pair of lead electrodes
3 is heated, and a pressing piece (a convex punch) having a shape like 27 is dropped straight down from above the package onto the lead electrode 24 (arrow) to form a concave portion in the lead electrode. To return the pressing piece 27 straight upward (arrow). By this operation, the lead electrode is pressurized and
(B) By forming a concave portion as seen in 17, the portion of 16 is slightly raised simultaneously (5 to 80).
μm), and that portion can be used as a projection for directly connecting the electrode of the LED chip and the lead electrode of the package.

FIG. 4 is a schematic diagram showing the shapes of the projections of several patterns formed by these methods as viewed from the top of the package (shaded portions indicate the projections). FIG.
The lead electrode of the light emitting diode corresponds to FIG.

Since the projections that replace the conventional bumps are formed only on the package side electrodes by these relatively simple methods, a complicated bump formation process can be eliminated, and a significant cost reduction and efficient mass production can be realized. Become. Also, since the protruding portion is formed only on the package side electrode, the L
A face-down structure that reduces the time required for the formation process compared to the case where bumps are formed on both the electrodes of the ED chip and the package, and reduces the gap between the chip and the package, thereby reducing the thickness of the light emitting diode. Can fulfill its original purpose more fully.

Next, as shown in FIG. 3, the package 33 having the protrusion 36 formed on a part of the lead electrode 34 by the above-described method is mounted on the flip-chip bonder table 39 so that the surface having the protrusion becomes the upper surface. The LED chip 31, which is arranged in such a manner as to be fixed by sucking air and formed at the same time by the above-described method, also has a surface opposite to the surface of the active layer formed on the semiconductor film forming substrate (the surface of the chip). The back surface) is sucked and held by the holder 38 of the flip chip bonder. Then, the holder side is brought close to the table, and the electrode part 32 on the chip side is moved.
The package and the lead electrode protrusions 36 on the package side are opposed to each other, and are closely contacted and pressurized with each other, and passed through a reflow furnace set at the melting temperature of the plating layer previously applied to the surface of the lead electrode of the package. Are joined face down. After cooling, the dissolved plating layer solidifies again, which allows the LED chip to be directly bonded and fixed to the lead electrode of the package,
Moreover, since the area of the joint can be made relatively large, the sense of stability of the joint increases. Alternatively, in the step of applying solder plating to the lead electrode surface described above, gold plating having a thickness of 1 μm or less is applied to the lead electrode surface, and solder balls are supplied to the lead electrode surface using cream solder or flux. By melting and solidifying the solder at the joint between the electrode and the LED chip, the LED
The same effect can be obtained by fixing the chip. The solder balls are fine particles having a particle diameter smaller than the thickness of the bump used in the conventional method as described above.

Further, when the LED chip and the lead electrode are joined, extra plating or solder extruded slightly around the lead electrode projecting portion 16 can absorb stress from the outside, and the two can be joined together. It serves to reinforce the part.

Subsequently, the light-transmissive epoxy resin 15 is used as a sealing member, and is placed on a package on which the LED chip is mounted from a thin tube.
Sealing was performed so that all joints between the ED chip and the package-side electrode could be protected. In the case where the light emitting diode emits mixed light of visible light from the LED chip and fluorescent light from the fluorescent material, the sealing member may be mixed with a fluorescent material. After the arrangement, the sealing member was cured at 150 ° C. for 5 hours to form a light emitting diode as shown in FIG. In some cases, the sealing member may not be used in accordance with the use application and environment of the light emitting diode.

Next, each component of the light emitting diode formed by the method according to the present invention will be described in detail with reference to FIG.

(LED Chip 11) The LED chip 11 used in the present invention includes, for example, a nitride-based compound semiconductor. The LED chip, which is a light emitting element, is an MO chip.
A semiconductor such as InGaN is formed as a light emitting layer on a substrate by a CVD method or the like. Examples of the semiconductor structure include a homo structure, a hetero structure, and a double hetero structure having an MIS junction, a PIN junction, a pn junction, and the like.
Various emission wavelengths can be selected depending on the material of the semiconductor layer and the degree of mixed crystal thereof. Also, a single quantum well structure or a multiple quantum well structure in which the semiconductor active layer is formed as a thin film in which a quantum effect occurs can be used.

When a gallium nitride-based compound semiconductor is used, sapphire, spinel, SiC, S
Materials such as i and ZnO are used. In order to form gallium nitride having good crystallinity, a sapphire substrate is preferably used. GaN, AlN on this sapphire substrate
And the like, and a gallium nitride semiconductor having a pn junction is formed thereon. Gallium nitride-based semiconductors exhibit n-type conductivity without being doped with impurities. When a desired n-type gallium nitride semiconductor is formed, for example, to improve luminous efficiency, Si, G
It is preferable to appropriately introduce e, Se, Te, C, and the like.
On the other hand, when forming a p-type gallium nitride semiconductor,
Type dopants Zn, Mg, Be, Ca, Sr, B
a and the like are doped.

Since the gallium nitride-based compound semiconductor is difficult to become p-type only by doping it with a p-type dopant, it is preferable to reduce the resistance by heating in a furnace, irradiating a low-speed electron beam or irradiating plasma after introducing the p-type dopant. After the exposed surfaces of the p-type semiconductor and the n-type semiconductor are formed by etching or the like, each electrode 12 having a desired shape is formed on the semiconductor layer by using a sputtering method, a vacuum evaporation method, or the like.

Next, the formed semiconductor wafer or the like is directly full-cut by a dicing saw in which a blade having a diamond cutting edge is rotated, or after a groove having a width wider than the cutting edge width is cut (half cut). The semiconductor wafer is broken by external force. Alternatively, an extremely thin scribe line (meridian) is drawn on the semiconductor wafer, for example, in a checkerboard pattern by a scriber in which a diamond needle at the tip reciprocates linearly, and then the wafer is cut by an external force and cut into chips from the semiconductor wafer. Thus, an LED chip that is a gallium nitride-based compound semiconductor can be formed.

In the light emitting diode of the present invention, when white light is emitted by mixing a fluorescent substance with the resin of the sealing member, the main light emitting wavelength of the light emitting element is 400 nm or more in consideration of the complementary color with the fluorescent substance. It is preferably 530 nm or less, more preferably 420 nm or more and 490 nm or less. L
In order to further improve the efficiency of the ED chip and the efficiency of the phosphor, the thickness is more preferably 450 nm or more and 475 nm or less.

(Package 13) The package 13 is formed by injecting a molding resin into a mold using a mold, molding the molded resin, and removing the molded resin from the mold after cooling. An insulating support member such as a PBT resin, a polyamide resin, an ABS resin, and a melamine resin can be used. Alternatively, a laminated board using an epoxy resin or the like, such as a printed board, may be used.

(Lead Electrode 14) As the lead electrode 14, an LED chip arranged on the package is electrically connected to the outside of the package, and therefore, a lead electrode 14 having excellent electric conductivity is preferable. Specific examples of the material include a metallized nickel or the like, or an electric conductor such as phosphor bronze or etched copper foil. In the case of the light emitting diode according to the present invention, the surface of such a material is plated with silver or gold (especially gold plating having a thickness of 1 μm or less) or tin-based smooth plating as an adhesive member to the LED chip. LED as well as electrode member
In order to efficiently emit light from the chip to the outside, the surface can be used as a light reflecting member.

(Sealing Member Resin 15) The sealing member 15 arranged on the LED chip protects the LED chip and the joint between the LED chip and the lead electrode on the package side from the outside according to the application of the light emitting diode. However, there is a case where it is not necessary to use it depending on the application. The sealing member can be formed using various resins, glass, or the like.

As a specific material of the sealing member, a transparent resin excellent in weather resistance, such as an epoxy resin, a urea resin, or silicone, or glass is preferably used. Also,
By including a diffusing agent in the sealing member, the directivity from the LED chip can be reduced and the viewing angle can be increased. Specific materials for the diffusing agent include barium titanate,
Titanium oxide, aluminum oxide, silicon oxide and the like are preferably used.

Hereinafter, in order to confirm the effect of the light emitting diode of FIG. 1 formed by the present invention, a light emitting diode as shown in FIG. 5 was formed, and a comparative experiment with the light emitting diode of the present invention was performed. The light emitting diode shown in FIG. 5 is formed by forming a protruding portion (bump) by plating or attaching a gold ball or the like to a metal pad of a chip in a wafer state as in the conventional method described above, and then separating the chips by dicing. Was formed in the same manner as the light emitting diode according to the present invention, except that solder bumps were also formed at positions corresponding to the metal pads on the package on which was disposed.

The steps of forming protrusions (bumps) on the respective lead electrode portions of the light emitting diode packages of FIGS. 1 and 5 are started simultaneously, and the protrusion portions (bumps) are respectively formed on the 1000 lead electrodes of both light emitting diode packages. Was formed. The time required to form the protruding portions on all the 1000 electrodes of the light emitting diode package of FIG. 1 was about 5 seconds, whereas the light emitting diode of FIG. 5 required about 30 minutes. Further, in the case of the light emitting diode of FIG. 5, bumps were also formed on the electrodes of the LED chip, so that it took about 30 minutes, and about 1 hour in total. Naturally, since the light emitting diode of FIG. 1 has protrusions only on the electrodes of the package, it is only about 75% of the thickness of the light emitting diode of FIG. 5, and the light emitting diode can be further thinned. Was.

[0036]

According to the present invention, the projecting portion for directly connecting the LED chip to the package electrode portion of the light emitting diode is formed by pressing a part of the electrode portion with a convex punch (pressing piece). Thus, the mass production efficiency and the production cost of the light emitting diode can be remarkably improved, and the thickness of the light emitting diode can be reduced. The joint between the LED chip and the lead electrode of the package may be fixed by melting and solidifying the solder plating applied to the lead electrode, or the surface of the gold-plated lead electrode having a film thickness of 1 μm or less. Furthermore, solder balls are applied using cream solder or flux, and the LED chips are fixed by melting and solidifying the solder, so that the area of the joint can be increased, thereby increasing the sense of stability of the joint. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a light emitting diode formed according to the present invention.

FIG. 2 is an enlarged view schematically showing a part of a process of forming a light emitting diode according to the present invention.

FIG. 3 is an enlarged view schematically showing a part of a process of forming a light emitting diode according to the present invention.

FIG. 4 is a schematic view of the shapes of projections of some patterns formed according to the present invention, as viewed from the top of the package (shaded portions indicate the projections).

FIG. 5 is a schematic sectional view of a light emitting diode formed for comparison with a light emitting diode according to the present invention.

[Explanation of symbols]

11, 31, 51 ... LED chip 12, 32, 52 ... electrode part of LED chip 13, 23, 33, 43, 53 ... package 14, 24, 34, 44, 54 ... package Lead electrodes 15, 55: Resin for sealing member 16, 36, 46 ... Protrusion of lead electrode 17: Depression of lead electrode 25, 35 ... Plating layer 26, 27 ... Convex punch (Pressing piece) 38 ... Flip chip bonder holder 39 ... Flip chip bonder base 56 ... Bump attached to LED chip 57 ... Solder bump 58 formed on package having lead electrode 58 ···resin

Claims (4)

[Claims] 1. A package having a pair of lead electrodes, a flip-chip type LED chip disposed on and electrically connected to the pair of lead electrodes,
A method of forming a light emitting diode, comprising: a light-transmitting resin that covers a D chip, wherein a part of each of the lead electrodes is pressed to protrude another part, and the LED chip A method for forming a light emitting diode, comprising: 2. A method for forming a light emitting diode, comprising: a package having at least a pair of lead electrodes; and an LED chip disposed on and electrically connected to the lead electrodes, wherein the LED chip is electrically connected to the LED chip. Forming a projection on the surface of each lead electrode by pressing a part of each of the lead electrodes to be connected to the other to raise another part, and fixing an LED chip on the lead electrode via the projection. And a step of disposing a translucent resin on the LED chip. 3. A pair of lead electrodes formed on the surface of the package are plated with solder, and the joint between the lead electrode and the LED chip is fixed by melting and solidifying the solder plating. The method for forming a light emitting diode according to claim 2, wherein: 4. A pair of lead electrodes formed on the surface of the package are plated with gold having a thickness of 1 μm or less, and a solder ball is supplied to the surface of the lead electrode using cream solder or flux. The joint between the LED chip and the LED chip is formed by melting and solidifying the solder.
3. The method according to claim 2, wherein the D chip is fixed.