CN107833947B

CN107833947B - LED packaging method

Info

Publication number: CN107833947B
Application number: CN201711213405.3A
Authority: CN
Inventors: 张亮
Original assignee: Institute of Flexible Electronics Technology of THU Zhejiang
Current assignee: Institute of Flexible Electronics Technology of THU Zhejiang
Priority date: 2017-11-28
Filing date: 2017-11-28
Publication date: 2020-12-18
Anticipated expiration: 2037-11-28
Also published as: CN107833947A

Abstract

The invention relates to an LED packaging method, which comprises the steps of preparing a substrate (21); fixing an LED chip on the substrate (21); arranging a first packaging layer (22) on the upper surface of the LED chip; forming a plurality of ball lenses (23) on the first encapsulation layer (22); a second packaging layer is arranged above the spherical lens (23) and the first packaging layer (22), and the second packaging layer (24) contains yellow fluorescent powder; and carrying out long-time baking on the LED chip provided with the first packaging layer (22), the plurality of spherical lenses (23) and the second packaging layer (24) so as to finish the packaging of the LED. According to the embodiment of the invention, the spherical lenses are arranged between the first packaging layer and the second packaging layer, and the spherical lenses and the arc-shaped second packaging layer carry out secondary shaping on the fluorescent light irradiated by the LED chip, so that light beams are more concentrated, the addition of extra lenses is avoided, and the production cost is reduced.

Description

LED packaging method

Technical Field

The invention belongs to the technical field of photoelectric devices, and particularly relates to an LED packaging method.

Background

The LED has the characteristics of long service life, high luminous efficiency, good color rendering property, safety, reliability, rich colors and easy maintenance. Under the background of today's increasingly serious environmental pollution, climate warming and energy source tension, the semiconductor lighting technology developed based on high-power LEDs has been recognized as one of the most promising high-technology fields in the 21 st century, which is a great leap in the history of human lighting since behind gas lighting, incandescent lamps and fluorescent lamps, and rapidly improves the lighting quality of human life.

At present, there are three main methods for realizing white light LEDs: blue light LED + yellow phosphor powder, RGB three-colour LED, ultraviolet LED + polychrome phosphor powder, when adopting blue light LED + yellow phosphor powder's mode, the phosphor powder generally is direct coating on the chip surface, and because the light scattering characteristic of phosphor powder makes a considerable part of normal incidence light can be by the backscattering, consequently, the chip has the absorption to the light of backscattering, so, the efficiency of getting light of encapsulation will be reduced to this kind of direct coating's mode. In addition, the fluorescent powder is directly coated on the chip, and the quantum efficiency of the fluorescent powder is obviously reduced due to the high temperature generated by the chip, so that the luminous efficiency of the package is seriously influenced.

On the other hand, because the light emitted by the LED light source is generally distributed in a divergent manner, the illumination brightness of the light source is not concentrated enough, and the light is generally shaped by an external lens, which increases the production cost.

Therefore, the development of a high lumen efficiency, low cost packaging technology has become a problem to be solved.

Disclosure of Invention

In view of the above problems, the present invention provides a new LED packaging method, and the specific embodiments are as follows.

Specifically, one embodiment of the present invention provides a method for packaging an LED, which includes,

step 1, preparing a substrate 21;

step 2, fixing the LED chip on the substrate 21;

step 3, arranging a first packaging layer 22 on the upper surface of the LED chip;

step 4, forming a plurality of spherical lenses 23 on the first packaging layer 22;

step 5, arranging a second packaging layer 24 above the spherical lens 23 and the first packaging layer 22, wherein the second packaging layer 24 contains yellow fluorescent powder;

and 6, performing long baking on the LED chip provided with the first packaging layer 22, the plurality of spherical lenses 23 and the second packaging layer 24 to complete the packaging of the LED.

In one embodiment of the present invention, step 3 comprises:

step 31, coating a first silica gel layer on the upper surface of the LED chip;

step 32, forming a hemispherical groove on the first silica gel layer by adopting a first hemispherical mold;

and step 33, removing the first hemispherical mold after the first silica gel layer is subjected to first primary baking to form the first packaging layer 22, wherein the first primary baking temperature is 90-125 ℃, and the time is 15-60 minutes.

In one embodiment of the present invention, step 4 comprises:

step 41, preparing a plurality of silica gel balls by utilizing the upper hemisphere die and the lower hemisphere die, wherein the silica gel balls contain yellow fluorescent powder;

42, removing the lower hemispherical mold, and placing the silica gel ball in the hemispherical groove;

and 43, performing second primary baking on the silica gel ball, and removing the upper hemisphere die to form the spherical lens 23, wherein the second primary baking temperature is 90-125 ℃, and the time is 15-60 minutes.

In one embodiment of the present invention, step 5 comprises:

step 51, coating a second silica gel layer above the spherical lens 23;

step 52, forming an arc shape on the upper surface of the second silica gel layer by using a second hemispherical mold;

and 53, carrying out third primary baking, demolding and polishing on the second silica gel layer to form the second packaging layer 24, wherein the third primary baking temperature is 90-125 ℃, and the time is 15-60 minutes.

In an embodiment of the present invention, step 4 is preceded by:

step 34, respectively configuring a silica gel material containing yellow phosphor powder for manufacturing the ball lens 23 and the second encapsulation layer 24, so that after light passes through the ball lens 23 and the second encapsulation layer 24, the wavelength range of the emitted fluorescence is 570nm-620 nm.

In one embodiment of the present invention, step 1 comprises:

step 11, selecting an aluminum material as a substrate 21, wherein the thickness of the substrate 21 is more than 0.5 mm and less than 10 mm;

step 12, cleaning the substrate 21;

and step 13, drying the substrate 21.

In one embodiment of the present invention, step 2 comprises:

step 21, preparing the LED chip, wherein the LED chip is a gallium nitride-based blue light chip;

step 22, arranging an anode electrode lead and a cathode electrode lead on the LED chip;

and step 23, welding the anode electrode lead and the cathode electrode lead on the substrate 21.

In one embodiment of the present invention, the refractive index of the first encapsulation layer 22 is smaller than the refractive index of the second encapsulation layer 24, and the refractive index of the spherical lens 23 is larger than the refractive index of the second encapsulation layer 24.

In one embodiment of the present invention, the diameter of the ball lens 23 is 10-200 microns, and a plurality of the ball lenses 23 are uniformly spaced and have a pitch of 10-200 microns.

In one embodiment of the present invention, a plurality of the spherical lenses 23 are arranged in a rectangular uniform manner, or in a diamond shape.

The invention has the beneficial effects that:

1. through set up spherical lens between first encapsulated layer and second encapsulated layer to set up yellow phosphor powder on second silica gel layer, make illumination concentrate more, avoided increasing extra lens moreover, reduced manufacturing cost.

2. By adopting the silica gel containing the yellow fluorescent powder to manufacture the spherical lens and the second packaging layer, the direct contact between the fluorescent powder and the LED chip is avoided, and the light extraction efficiency of LED packaging is improved.

Drawings

FIG. 1 is a flow chart of a method for packaging an LED according to an embodiment of the present invention;

fig. 2 is a process flow diagram for preparing a substrate in a method for packaging an LED according to an embodiment of the present invention;

fig. 3 is a process flow diagram for preparing an LED chip in an LED packaging method according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a blue LED chip in an LED packaging method according to an embodiment of the present invention;

FIG. 5 is a detailed flowchart of a method for packaging an LED according to an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of an LED package structure manufactured by the LED packaging method provided by the embodiment of the invention;

FIGS. 7A and 7B are schematic diagrams illustrating an arrangement of a plurality of spherical lenses according to an embodiment of the present invention;

fig. 8 is a flow chart of a package inspection process in the LED packaging method according to the embodiment of the present invention.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Referring to fig. 1, fig. 1 is a flowchart of a method for packaging an LED according to an embodiment of the present invention; the LED packaging method provided by the embodiment of the invention comprises the following specific steps:

step 1: preparing a substrate 21; as shown in fig. 2, fig. 2 is a process flow diagram for preparing a substrate in a method for packaging an LED according to an embodiment of the present invention; specifically, the substrate 21 is a solid aluminum plate, when the substrate 21 is prepared, the substrate 21 is cut into a required size, then the substrate is cleaned, stains, especially oil stains on the substrate are cleaned, and the substrate 21 is dried to keep the substrate 21 dry, in the embodiment, the thickness D of the substrate 21 is greater than 0.5 mm and less than 10 mm, and the width W of the substrate 21 can be cut according to actual requirements without limitation; because the base plate 21 is thick and not easy to be deformed by heat, when an additional heat dissipation device is added, the base plate can be well attached to the heat dissipation device, and the heat dissipation effect is better.

Step 2: fixing an LED chip on the substrate 21; fig. 3 is a process flow diagram for preparing an LED chip in an LED packaging method according to an embodiment of the present invention; in particular, the method comprises the following steps of,

step 21: preparing the LED chip, wherein the LED chip is a gallium nitride-based blue light chip; as shown in fig. 4, fig. 4 is a schematic structural diagram of a blue LED chip in an LED packaging method according to an embodiment of the present invention; the LED chip comprises a substrate layer 1, a GaN buffer layer 2, an N-type GaN layer 3, a P-type GaN quantum well wide band gap material 4 and a P-type GaN quantum well wide band gap material 6, an INGaN light emitting layer 5, an AlGaN barrier layer 7 and a P-type GaN layer 8, and is characterized in that the thickness of the LED chip is between 90 and 140 micrometers.

Step 22: an anode electrode lead and a cathode electrode lead are arranged on the LED chip, and the method specifically comprises the following steps: and a cathode electrode is arranged on the N-type GaN layer and provided with an external lead, and an anode electrode is arranged on the P-type GaN layer and provided with an external lead.

Step 23: welding the anode electrode lead and the cathode electrode lead to the substrate 21; the method specifically comprises the steps of welding a lead on the LED chip on the substrate 21 and fixing the LED chip body on the substrate 21.

It should be noted that, after the above steps are completed, the embodiment of the present invention further needs to check the bonding wire, and when the bonding wire is correct, step 3 is performed, and if there is a problem in the wire bonding detection, steps 21 to 23 are repeated.

And step 3: arranging a first packaging layer 22 on the upper surface of the LED chip; as shown in fig. 5, fig. 5 is a detailed flowchart of a method for packaging an LED according to an embodiment of the present invention; in particular, the method comprises the following steps of,

step 31: coating a first silica gel layer on the upper surface of the LED chip; it should be noted that the first silica gel layer does not contain the fluorescent powder, so that the fluorescent powder can be prevented from being in direct contact with the LED chip, and the problem of the quantum efficiency reduction of the fluorescent powder caused by high temperature is solved. On the other hand, because the first silica gel layer is directly coated on the LED chip and needs to be capable of tolerating a large amount of heat emitted by the LED chip, the silica gel in contact with the LED chip is high-temperature-resistant silica gel, so that the problem that the transmittance is reduced because the silica gel is easy to age and yellow due to heating can be avoided.

Step 32: forming a hemispherical groove on the first silica gel layer by adopting a first hemispherical mold; when first silica gel layer has not solidified, use first hemisphere mould, extrude the hemisphere recess in the embedding first silica gel layer on first silica gel layer.

It should be noted that, a plurality of hemispherical recesses are arranged on the first silica gel layer, and in addition, when the hemispherical recesses are arranged on the first silica gel layer, the distance from the bottom surfaces of the hemispherical recesses to the upper surface of the LED chip is L, and L is greater than 3 micrometers in order to ensure the light extraction efficiency.

Step 33: and after the first silica gel layer is subjected to first primary baking, removing the first hemispherical mold to form the first packaging layer 22, specifically, performing first primary baking on the first silica gel layer together with the first hemispherical mold, and after the first silica gel layer is cured, removing the first hemispherical mold to form the first packaging layer 22 with a plurality of uniformly arranged hemispherical grooves, wherein the first primary baking temperature is 90-125 ℃, and the baking time is 15-60 minutes.

In this embodiment, referring to fig. 5, before step 4 is executed, the silica gel containing the yellow phosphor needs to be prepared, that is, step 34 is executed: the preparation method comprises the steps of respectively preparing silica gel materials containing yellow fluorescent powder for manufacturing the spherical lens 23 and the second packaging layer 24, specifically, mixing the yellow fluorescent powder with the silica gel for manufacturing the spherical lens 23 and the silica gel for manufacturing the second packaging layer 24, and performing color test after mixing, so that the wavelength of the emitted fluorescent light is between 570nm and 620nm after the light of the GaN-based blue light chip is irradiated on the silica gel mixed with the yellow fluorescent powder. Step 4 is then performed.

And 4, step 4: forming a plurality of ball lenses 23 on the first encapsulation layer 22; as shown in fig. 5, the method specifically includes:

specifically, a spherical cavity is formed by using an upper hemispherical mold and a lower hemispherical mold, and then lens silica gel for preparing the spherical lens 23 is injected into the spherical cavity to form a silica gel ball, wherein the lens silica gel contains and is prepared with yellow fluorescent powder.

specifically, the lower hemispherical mold of the silicone ball is removed, and then the silicone ball is placed in the hemispherical groove on the first encapsulation layer 22, it should be noted that the size of the hemispherical groove is matched with the size of the silicone ball, and the size can be determined when the sizes of the first hemispherical mold, the upper hemispherical mold and the lower hemispherical mold are selected.

Step 43: carrying out second primary baking on the silica gel ball, and removing the upper hemisphere die to form the spherical lens 23, wherein the second primary baking temperature is 90-125 ℃, and the baking time is 15-60 minutes; specifically, the silica gel ball is subjected to second primary baking so that the silica gel ball can be fixed on the first packaging layer 22, and the upper hemispherical mold is removed after the second primary baking, which is beneficial to shaping the spherical lenses 23, and it should be noted that two adjacent spherical lenses 23 are connected through the silica gel strip.

By arranging the spherical lens 23, the propagation direction of light can be changed, the total reflection effect can be effectively inhibited, more light can be emitted to the outside of the LED, and the luminous efficiency of the LED is improved.

It should be noted that, in the embodiment of the present invention, the spherical lens 23 shapes the light irradiated by the GaN-based blue chip, so as to make the light beam more concentrated, and as shown in fig. 7A and 7B, the plurality of spherical lenses 23 formed on the first encapsulation layer 22 may be uniformly arranged in a rectangular shape, or may be uniformly arranged in a diamond shape, and the arrangement manner of the plurality of spherical lenses 23 may also be in a circular shape, an elliptical shape, or an irregular shape, so as to ensure that the light of the light source is uniformly distributed in the concentrated region to the maximum extent, which is not limited in the embodiment of the present invention.

In addition, the size of the ball lens 23 is also limited in this embodiment, if the size of the ball lens 23 is too small, the ball lens 23 cannot focus the light beam, and when the size of the ball lens 23 is too large, the light beam is easily uneven, so in this embodiment, the diameter 2R of the ball lens 23 is between 10 and 200 micrometers, and the plurality of ball lenses 23 are uniformly spaced, that is, the distance is equal, in this embodiment, the distance a between two adjacent ball lenses 23 is 10 to 200 micrometers, it should be noted that in this embodiment of the present invention, the distance between two adjacent ball lenses 23 may be different, and the smaller the distance a between two adjacent ball lenses 23, the better.

Optionally, in the embodiment of the present invention, the distance a between two adjacent spherical lenses 23 and the distance L from the bottom end of the spherical lens 23 to the LED chip may be equal.

And 5: a second encapsulating layer 24 is arranged above the ball lens 23 and the first encapsulating layer 22, and the second encapsulating layer 24 contains yellow fluorescent powder; referring to fig. 5, specifically including,

step 51, coating a second silica gel layer above the spherical lens (23); the upper surfaces of the spherical lenses 23 and the positions between two adjacent spherical lenses 23 are coated with second silica gel layers made of silica gel containing yellow fluorescent powder.

Step 52: forming an arc on the upper surface of the second silica gel layer by using a second hemispherical die; the arc can be hemispherical, parabolic or flat, wherein the hemispherical light-emitting angle is the largest, and the arc is suitable for common lighting application; the parabolic light-exit angle is minimal and suitable for local lighting applications; and a flat shape between the two, suitable for indicating illumination. Therefore, the specific shape can be selected according to the application place of the product so as to achieve the best use effect.

Step 53: and carrying out third primary baking, demolding and polishing on the second silica gel layer to form a second packaging layer 24, wherein the third primary baking temperature is 90-125 ℃, and the baking time is 15-60 minutes. After the third is baked once, the second silica gel layer solidifies, forms second encapsulated layer 24, removes the second hemisphere mould of second encapsulated layer 24 upper surface, then polishes the second silica gel layer of solidification, makes the upper surface on second silica gel layer form a big lens, just so can make the light of the formula of dispersing that the LED light source sent concentrate more, has improved light source luminance, need not additionally set up external lens moreover and carry out the secondary plastic, has reduced manufacturing cost.

It should be noted that, in the embodiment of the present invention, the plurality of spherical lenses 23 are "convex mirrors", and the focal length f = R/(2(n2-n1)) of the convex mirrors ", where n2 is the refractive index of the spherical lens 23, n1 is the average of the refractive indexes of the first encapsulant layer 22 and the second encapsulant layer 24 (the refractive indexes of the upper layer and the lower layer of the silica gel of the spherical lens 23 in the embodiment of the present invention are close), and R is the radius of the spherical lens 23.

In order to ensure that the light is not converged after exiting from the lens, and does not diverge, in the embodiment of the present invention, the height of the second encapsulation layer 24 above the top surface of the ball lens 23 should be within 2 times of the focal length, that is, the thickness of the second encapsulation layer 24 should be above the top surface R/(n 2-n1) of the ball lens 23, and in practical applications, the thickness of the second encapsulation layer 24 is generally 50 to 500 micrometers higher than the top surface of the ball lens 23.

In this embodiment, the refractive index of the first encapsulation layer 22 is smaller than the refractive index of the second encapsulation layer 24, and the refractive index of the spherical lens 23 is larger than the refractive index of the second encapsulation layer 24. Specifically, in the embodiment of the present invention, the arrangement mode in which the refractive index of the silica gel layer increases from bottom to top in sequence can better suppress the total reflection phenomenon, and the smaller the refractive index of the second encapsulation layer 24, the better the refractive index is, so as to avoid the formation of a refractive index difference between the second encapsulation layer 24 and the outside air, which leads to total reflection.

In addition, in the embodiment of the present invention, the light color of the light emitted from the LED light source can be adjusted by changing the content of the yellow phosphor in the spherical lens 23 and the second encapsulation layer 24, and the light color can be changed into white and then yellow, and the color temperature of the light source can also be adjusted. The LED light source is adjusted based on the actual requirement of the LED light source in the embodiment of the present invention, which is not limited in the embodiment of the present invention.

Step 6: and performing long-time baking on the LED chip provided with the first packaging layer 22, the plurality of spherical lenses 23 and the second packaging layer 24 to finish the packaging of the LED, wherein the long-time baking temperature is within the range of 100 ℃ and 150 ℃, and the baking time is 4-12 hours. In this embodiment, through long baking, the internal stress of the first package layer 22, the second package layer 24 and the plurality of spherical lenses 23 is eliminated, so that the package structure is firmer, the performance is more stable, and finally, a finished LED package product is formed.

As shown in fig. 6, fig. 6 is a schematic structural diagram of an LED package structure manufactured by the LED packaging method provided in the embodiment of the present invention; wherein 21 is a substrate; 22 is a first encapsulating layer, 23 is a

ball lens

23, and 24 is a second encapsulating layer.

It should be noted that, after the LED package is completed, as shown in fig. 8, fig. 8 is a flowchart of a detection packaging process in the LED packaging method provided in the embodiment of the present invention; including test sorting and packaging of the package structure to form a finished product for subsequent use.

In summary, the specific examples are applied herein to illustrate the implementation of the LED packaging method provided in the embodiments of the present invention, and the above description of the embodiments is only used to help understanding the method of the present invention and its core idea; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention, and the scope of the present invention should be subject to the appended claims.

Claims

1. An LED packaging method is characterized by comprising the following steps,

step 1, preparing a substrate (21);

step 2, fixing the LED chip on the substrate (21);

step 3, arranging a first packaging layer (22) on the upper surface of the LED chip; a plurality of hemispherical grooves are formed on the first packaging layer (22);

step 4, forming a plurality of spherical lenses (23) on the first packaging layer (22); the spherical lens (23) is formed in the hemispherical groove;

step 5, arranging a second packaging layer (24) above the spherical lens (23) and the first packaging layer (22), wherein the second packaging layer (24) contains yellow fluorescent powder;

step 6, carrying out long baking on the LED chip provided with the first packaging layer (22), the plurality of spherical lenses (23) and the second packaging layer (24) to complete the packaging of the LED;

the diameter of the spherical lens (23) is 10-200 microns, and a plurality of spherical lenses (23) are uniformly arranged at intervals, and the distance between the spherical lenses (23) is 10-200 microns; the spherical lenses (23) are uniformly arranged in a rectangular shape or arranged in a rhombic shape;

the refractive index of the first encapsulation layer (22) is smaller than the refractive index of the second encapsulation layer (24), and the refractive index of the spherical lens (23) is larger than the refractive index of the second encapsulation layer (24);

the focal length f = R/(2(n2-n1)) of the ball lens (23), wherein n2 is the refractive index of the ball lens (23), n1 is the average of the refractive indices of the first encapsulation layer (22) and the second encapsulation layer (24), and R is the radius of the ball lens (23); the second packaging layer (24) is higher than the top surface of the spherical lens (23) by a distance which is not more than R/(n 2-n 1).

2. The LED packaging method according to claim 1, wherein step 3 comprises:

step 31, coating a first silica gel layer on the upper surface of the LED chip;

and step 33, removing the first hemispherical mold after the first silica gel layer is subjected to first primary baking to form the first packaging layer (22), wherein the first primary baking temperature is 90-125 ℃, and the time is 15-60 minutes.

3. The LED packaging method according to claim 2, wherein step 4 comprises:

and 43, carrying out second primary baking on the silica gel ball, and removing the upper hemisphere die to form the spherical lens (23), wherein the second primary baking temperature is 90-125 ℃, and the time is 15-60 minutes.

4. The LED packaging method according to claim 3, wherein step 5 comprises:

step 51, coating a second silica gel layer above the spherical lens (23);

and 53, carrying out third primary baking, demolding and polishing on the second silica gel layer to form a second packaging layer (24), wherein the third primary baking temperature is 90-125 ℃, and the time is 15-60 minutes.

5. The LED packaging method according to claim 1, wherein step 4 is preceded by:

and step 34, respectively configuring silica gel materials containing yellow fluorescent powder for manufacturing the spherical lens (23) and the second packaging layer (24), so that the wavelength range of the emitted fluorescent light is 570nm-620nm after the light penetrates through the spherical lens (23) and the second packaging layer (24).

6. The LED packaging method according to claim 1, wherein step 1 comprises:

step 11, selecting an aluminum material as a substrate (21), wherein the thickness of the substrate (21) is more than 0.5 mm and less than 10 mm;

step 12, cleaning the substrate (21);

and step 13, drying the substrate (21).

7. The LED packaging method according to claim 1, wherein step 2 comprises:

and 23, welding the anode electrode lead and the cathode electrode lead on the substrate (21).