TWI459601B - Method of distributing phosphor - Google Patents

Description

Fluorescent powder coating method

The invention relates to a phosphor powder coating method, in particular to a light-emitting diode phosphor powder coating method.

Light-emitting diodes have been used in more and more occasions due to their high luminous efficiency, low energy consumption, and no pollution. They have a tendency to replace traditional light sources.

The light-emitting diode system emits light by exciting its light-emitting chip with a current. Since a single light-emitting diode chip often cannot produce the desired color (especially white for daily illumination), the phosphor powder is usually coated on the light-emitting diode wafer, and the wavelength conversion function of the phosphor powder is used to emit light. The color of the polar body wafer is adjusted. A commonly used phosphor powder coating method uses a spray method to spread the phosphor powder on the surface of the light-emitting diode wafer. However, since a mask is required to shield the periphery of the light-emitting diode wafer in advance to prevent contamination, When spraying, a considerable portion of the phosphor powder adheres to the mask, causing waste of the phosphor powder.

There is also another way in which the industry uses a dispensing method to coat the phosphor powder, that is, a gel-doped colloid on the surface of the light-emitting diode wafer by means of a tool point. Although the method of dispensing can avoid the waste of the phosphor powder, since the phosphor powder is disorderly distributed in the gel body, it is difficult to uniformly cover the light-emitting diode wafer. Therefore, this method is likely to cause color cast of the LED, which affects the yield of the product.

Therefore, it is necessary to provide a method capable of uniformly coating the phosphor powder.

A phosphor powder coating method comprising the steps of: 1) providing a substrate having a light-emitting diode wafer; 2) covering the light-emitting diode wafer with a dielectric layer doped with phosphor powder, and the phosphor powder may be in the dielectric layer Moving, the fluorescent powder carries a charge; 3) applying an electric field to the dielectric layer, causing the charged fluorescent powder in the dielectric layer to move to the surface of the light emitting diode wafer under the action of the electric field to uniformly cover the light emitting diode wafer .

This phosphor coating method moves to the surface of the light-emitting diode wafer by applying an electric field to the charged phosphor powder. Thereby, the phosphor powder can be uniformly distributed on the surface of the light-emitting diode wafer without being disorderly distributed throughout the dielectric layer, thereby avoiding occurrence of color cast due to uneven distribution.

10‧‧‧Substrate

20‧‧‧Light Diode Wafer

30‧‧‧Media layer

40‧‧‧Fluorescent powder

50‧‧‧positive electric mould

52‧‧‧ positive charge

60‧‧‧Negative electric mould

62‧‧‧Negative charge

70‧‧‧ electric field

500‧‧‧ Groove

Fig. 1 shows the first step of the phosphor coating method of the first embodiment of the present invention.

Fig. 2 shows the second step of the phosphor coating method of the first embodiment of the present invention.

Fig. 3 shows a third step of the phosphor coating method of the first embodiment of the present invention.

Fig. 4 shows a fourth step of the phosphor coating method of the first embodiment of the present invention.

Fig. 5 shows the fifth step of the phosphor coating method of the first embodiment of the present invention.

Fig. 6 shows a third step of the phosphor coating method of the second embodiment of the present invention.

Fig. 7 shows a fourth step of the phosphor coating method of the second embodiment of the present invention.

Fig. 8 shows a fifth step of the phosphor coating method of the second embodiment of the present invention.

Referring to Figures 1-5, a method of coating a phosphor powder coating for a light-emitting diode according to a first embodiment of the present invention is shown.

First, a substrate 10 having a light emitting diode wafer 20 is provided as shown in FIG. The substrate 10 may be made of a material having good thermal conductivity, such as metal or ceramic, to facilitate heat dissipation of the LED wafer 20. The material of the LED wafer 20 may be selected from semiconductor luminescent materials such as gallium nitride, indium gallium nitride, gallium phosphide, etc., depending on the actual luminescence requirements. Preferably, in this embodiment, the light-emitting diode wafer 20 is fabricated using a blue light-emitting semiconductor material to finally output desired white light.

Then, as shown in FIG. 2, the dielectric layer 30 of the phosphor powder 40 is doped on the surface of the light-emitting diode wafer 20. The dielectric layer 30 may be made of a transparent material such as epoxy resin, polycarbonate or polymethyl methacrylate. The dielectric layer 30 is fluid and the phosphor powder 40 can move inside. The phosphor powder 40 is disorderly distributed in the dielectric layer 30, and has a particle diameter of between 50 nm and 100 μm. The phosphor powder 40 may be made of a material such as a niobate compound, yttrium aluminum garnet, a nitride, and an oxynitride. Preferably, in this embodiment, a yttrium aluminum garnet doped with trivalent europium (Y ₃ Al) is used. ₅ O ₁₂ :Ce ³⁺ ) is formed to excite yellow light after absorbing the blue light emitted from the light-emitting diode wafer 20, thereby mixing with the remaining blue light to form white light. The phosphor powder 40 is previously treated to have a positive charge before being doped into the dielectric layer 30. Specifically, the phosphor powder 40 is immersed in a solution of isopropyl alcohol and magnesium nitrate so that magnesium ions in the magnesium nitrate adhere to the phosphor powder 40 to be positively charged. The phosphor powder 40 is then separated from the solution, dried and then incorporated into the dielectric layer 30. Of course, the phosphor powder 40 can also be positively or negatively charged by other methods, and only one of the treatment methods is listed above.

Then, as shown in FIG. 3, a first charging mold is suspended on the LED chip 20. And a second charged mold is placed under the substrate 10. In this embodiment, the first charging mold is a positively charged positive mold 50, and the second charged mold is a negatively charged negative mold 60. Of course, the first charging mold may be negatively charged according to different charging conditions of the fluorescent powder 40, and the second charging mold may be negatively charged. The positive electric mold 50 has a flat shape which is spaced apart from the dielectric layer 30 on the light-emitting diode wafer 20. The positive electrode mold 50 may be filled with a positive charge 52 on its bottom surface after being energized. The negative electrode mold 60 also has a flat shape and is placed under the substrate 10. An insulating layer (not shown) may be interposed between the substrate 10 and the negative electrode mold 60 to prevent the electric charge from affecting the circuit structure on the substrate 10. Negative electric mold 60 produces a negative charge 62 only in its central region after energization. The positive electric mold 50 and the negative electric mold 60 cooperate to generate an electric field 70 perpendicular to the surface of the light-emitting diode wafer 20 in a direction opposite to the light-emitting direction of the light-emitting diode wafer 20. The positively charged phosphor powder 40 is moved by the electric field 70 to be concentrated on the surface of the light emitting diode wafer 20, thereby uniformly covering the light emitting diode wafer 20. In order to ensure that the phosphor powder 40 can be spread over the entire surface of the LED substrate 20, the area of the negative electric region of the negative electric mold 60 in this embodiment is larger than the area of the photodiode wafer 20.

Thereafter, as shown in FIG. 4, the positive electric mold 50 is moved toward the negative electric mold 60, and the positive electric mold 50 is brought into contact with the dielectric layer 30 and pressed until the dielectric layer 30 is compressed to a predetermined thickness. As shown in FIG. 4, at the extrusion of the positive electric mold 50, both ends of the dielectric layer 30 overflow outward and cover the respective sides of the light-emitting diode wafer 20. In addition, since the dielectric layer 30 partially extends to the surface of the substrate 10, part of the phosphor powder 40 will move to the surface of the substrate 10 under the action of an electric field.

Finally, as shown in FIG. 5, the positive electric mold 50 and the negative electric mold 60 are removed, and then the dielectric layer 30 is cured by heating, ultraviolet irradiation or the like to fix the position of the fluorescent powder 40. Of course, it is also possible to first cure the dielectric layer 30 and then remove the positive mold 50 and negative The electric mold 60 has no effect on the order of the two.

By applying an electric field 70, the positively charged phosphor powder 40 can be collected on the surface of the light emitting diode wafer 20 to achieve uniform coverage of the light emitting diode wafer 20. Therefore, the light emitted from the LED wafer 20 can be converted into uniform yellow light by the phosphor powder 40, and then mixed into white light, thereby substantially avoiding the color cast phenomenon caused by uneven light mixing in the prior art.

The phosphor powder 40 in this embodiment is distributed only on the top surface of the LED substrate 20 and the surface of the substrate 10. Since the light-emitting diode wafer 20 emits light in addition to the top surface, the light is emitted in the above embodiment. The diode wafer 20 still has a portion of the light that is not sufficiently converted by the phosphor 40.

In order to improve the above problems, the present invention still further provides another method of coating a phosphor powder, which differs from the first embodiment in that the charged regions of the positive electrode mold 50 and the negative electrode mold 60 are different.

The first two steps of the other phosphor coating method are the same as the first and second steps of the foregoing embodiment, and are not described herein.

Referring to FIG. 6, the positive electrode mold 50 of the present embodiment is a plate-like structure having a groove 500 formed on the bottom surface thereof, and a positive electric charge 52 is distributed over the edge of the groove 500. The shape of the negative electric mold 60 is the same as that of the negative electric mold 60 of the foregoing embodiment, but its negative electric charge 62 is concentrated only in a region immediately in the middle of the negative electric mold 60. The area of the negatively charged region is smaller than the area of the light-emitting diode wafer 20, so that when the positive electric mold 50 and the negative electric mold 60 are energized, the electric field 70 will contract toward a smaller negative electric area to exhibit an upper width and a lower width. distributed.

Referring to FIG. 7, when the positive electric mold 50 is moved toward the negative electric mold 60, it overflows the extruded dielectric layer 30 to both sides to cover the respective sides of the light-emitting diode wafer 20. due to The electric field 70 is contracted, and in addition to being driven by the electric field 70 to a portion of the phosphor powder 40 distributed on the top surface of the LED substrate 20 and the surface of the substrate 10, a portion of the phosphor powder 40 is driven by the lateral component of the electric field 70. It is attached to each side of the light-emitting diode wafer 20. Thereby, all of the light-emitting surfaces of the light-emitting diode wafer 20 are covered with the phosphor powder 40, thereby further improving the problem of uneven light mixing.

Moreover, due to the pressing of the recess 500 of the positive electric mold 50, the dielectric layer 30 will form a regular rectangle having the same shape as the recess 500 as shown in FIG. 8 after being cured, thereby facilitating the subsequent process flow.

It can be understood that the negative electric mold 60 in the two embodiments can also be replaced by the substrate 10, that is, the corresponding negative electric region can be directly formed on the substrate 10, and the same effect can be achieved.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims.

10‧‧‧Substrate

20‧‧‧Light Diode Wafer

30‧‧‧Media layer

40‧‧‧Fluorescent powder

50‧‧‧positive electric mould

52‧‧‧ positive charge

60‧‧‧Negative electric mould

62‧‧‧Negative charge

70‧‧‧ electric field

Claims (11)

A method for coating a phosphor powder, comprising the steps of: 1) providing a substrate having a light-emitting diode wafer; 2) providing a dielectric layer doped with phosphor powder on the surface of the light-emitting diode wafer, and the phosphor powder may be in the dielectric layer Internal movement, the fluorescent powder carries a charge; 3) an electric field is applied to the dielectric layer, and the fluorescent powder in the driving medium layer is concentrated on the surface of the light-emitting diode wafer to uniformly cover the light-emitting diode wafer, wherein the electric field is set in the light-emitting diode The first electrified region above the diode wafer and the second charged region disposed under the LED wafer, the first electrode region is spaced apart from the phosphor in the dielectric layer, and the second charged region is disposed An insulating arrangement is provided between the light emitting diode and the second charged region, and the polarity of the second charged region is opposite to the polarity of the first charged region. The method of coating a phosphor according to claim 1, wherein the first charging mold is used in the step 3), and the first charged region is located on the first charging mold. The method of coating a phosphor according to claim 2, wherein the first electrification mold has a recess opposite to the LED wafer. The method of coating a phosphor according to claim 1, wherein the second charging mold is used in the step 3), and the second charged region is located on the second charging mold. The method of coating a phosphor according to claim 4, wherein the second charged mold is attached to the bottom surface of the substrate by an insulating layer. The method of coating a phosphor according to claim 1, wherein the second charged region is located on the substrate. The method of coating a phosphor according to any one of claims 1 to 6, wherein the area of the second charged region is smaller than the area of the LED, and the electric field is from the first charged region toward the second strip. The electrical area shrinks. The phosphor coating method according to any one of claims 1 to 6, wherein the area of the second charged region is larger than the area of the light-emitting diode wafer, and the electric field is perpendicular to the top surface of the light-emitting diode wafer. The phosphor coating method according to any one of claims 2 to 6, wherein the step 3) further comprises a process of moving the first charging mold toward the second charging region, the first charging mold being squeezed during the moving process. The dielectric layer causes the dielectric layer to flow along the sides of the light emitting diode wafer. The method of coating a phosphor powder according to claim 9, wherein the step 3) comprises a process of curing the dielectric layer. The phosphor powder coating method according to any one of claims 1 to 6, wherein the phosphor powder in the step 2) is first immersed in the solution to adhere the charged particles, and then doped in the dielectric layer.