CN100466873C - Packaging method of white LED surface light source module - Google Patents

Abstract

The invention discloses a packaging method for a white LED surface light source module, which is composed of process steps such as making a circuit board, solid crystal, bonding, and packaging a basic adhesive layer. The invention adopts multi-particle low-power LED chips dispersedly distributed on the circuit board, and is packaged as a whole to form a high-power LED light source, so that the heat source is dispersed and distributed, the calorific value per unit area is reduced, and the heat dissipation requirement standard is lowered. Using white colloid as the crystal-bonding glue can increase the utilization rate of more than 70% of the light emitted from the back. Through the encapsulation of the basic glue layer, the microscopic light source points are evenly distributed on a larger area, which reduces the luminous intensity per unit area. The luminous flux per unit area of the traditional LED light source is generally above 100lm/cm ² , but the luminous flux per unit area of the light source of the present invention is generally less than 5lm/cm ² , so glare can be overcome.

Description

Packaging method of white LED surface light source module

technical field

The invention relates to an LED packaging method, in particular to a packaging method for a white LED surface light source module.

Background technique

The application potential of LED light source in the field of white light lighting is very huge. The usual manufacturing method of white LEDs is to install blue LED chips in a bowl-shaped reflective cavity, covered with a thin layer of resin mixed with YAG:Ce phosphor powder that can produce yellow light, about 200-500nm. Part of the blue light emitted by the LED chip is absorbed by the phosphor, and the other part of the blue light is mixed with the yellow light emitted by the phosphor to obtain white light.

At present, the packaging of low-power white light LEDs is mainly Φ3, Φ5, Φ10 or straw hat type and piranha. The packaging of high-power white light LEDs is mainly to package single or multiple high-power chips such as 1W and 3W on ceramic shells or aluminum substrate shells. This package has a simple structure and is very suitable for applications such as indicator lights, flashlights, spotlights, and searchlights that require directivity of outgoing light. However, in the field of high-power white light applications, such as environmental lighting for white light work lighting, site lighting, and flood lighting, the current high-power white LED products still have problems such as insufficient light efficiency, heat dissipation, and glare. , price issues and many other difficulties that are difficult to commercialize.

At present, the production methods of high-power white LED products can be divided into two categories according to the chip composition:

One is white LED particles (such as Φ3, Φ5, Φ10 or straw hat type) packaged with low-power chips. Multiple particles are combined to achieve power accumulation. Small ones use dozens of them to form a light source of several watts, and many Use hundreds of pieces to form a light source product with tens of watts. However, since the light source is composed of dozens or even hundreds of bright spots with high light intensity, the emitted light has strong spots (glare spots) on the microscopic scale. Many bright spots or even glare dots make the observation of objects unclear. This phenomenon is especially obvious when observing objects within the field of view of the microscope when the light source composed of point particle LEDs is used for microscope illumination. In addition, the multi-particle packaged LED lights are combined together, the surface shape is complex, it is easy to absorb dust, it is difficult to clean and affects the appearance. Third, when multi-particle packaged LED lamps are combined, it is necessary to select LED single lamps with consistent characteristics, which increases the difficulty of the process in the production process. Fourth, the luminous efficiency is low. The reflective cup of the aluminum bracket has low comprehensive reflection efficiency for white light, and the light loss is relatively large.

Another method is to use single or multiple high-power LEDs, such as 1W and 3W chips, to be packaged on a low thermal resistance shell, and then add a large-area heat sink to release the heat emitted by the high-power chips and reduce the temperature of the LED. The junction temperature of the chip ensures the normal operation of the LED chip. This packaging method is the same as the disadvantage 1 of the previous light source, and even has more serious glare. As a light source used at close range, secondary optical measures must be taken. The heat source is concentrated in a very small area, and the heating power is relatively large, so it is necessary to design a very good heat path and a relatively large heat dissipation surface area. There is also the problem of low light efficiency.

For the problem of glare, the following two methods are usually used to solve it:

One is to cover the light source with a layer of light mixing film (such as ground glass, anisotropic acrylic plate, transparent plate that changes the light emission angle, etc.) to reduce the intensity of the glare point and make the outgoing light more divergent. This method brings The disadvantage is that the total luminous flux of the outgoing light is reduced. Moreover, the structure becomes complicated, the volume becomes complicated, and the cost increases to varying degrees.

The second is to irradiate the light source on the reflective cup and then emit the light from the reflective cup, forming diffuse reflection on the surface of the reflective cup to make the outgoing light more divergent. This method also has the disadvantage of reducing the total luminous flux of the outgoing light, and because of consideration The secondary reflection will also be more complicated in structural design.

In short, in the field of white light high-power applications, the current LED light source products still have problems such as high heat dissipation cost, complex heat dissipation structure, low luminous efficiency, serious glare problem, complex structure for changing glare, and affect luminous efficiency.

Contents of the invention

The technical problem to be solved by the present invention is to provide a packaging method for a high-power white LED surface light source module, which is simple to manufacture and low-cost to solve the heat dissipation problem of the above-mentioned high-power white LED light source products, overcomes glare, and improves luminescence efficiency.

The technical solution adopted in the present invention is: a packaging method for a white LED surface light source module, which consists of the following process steps:

(1) Make a circuit board, calculate the permitted light-emitting area according to the power, select the supporting chip emission peak wavelength, light intensity and phosphor excitation wavelength range according to the color temperature requirements, calculate the required LED chip quantity according to the power requirements, and then input according to the requirements Voltage to design the serial and parallel circuit structure, and then according to the principle of uniform distribution and dispersion of chips, make circuit boards with serial and parallel structures that meet the requirements, and white solder resist outside the pads on the surface of the circuit board;

(2) Solid crystal, use white or transparent glue as the solid crystal glue, apply glue evenly on the back of the chip, bond the chip to the corresponding position of the pad on the circuit board on the solid crystal table, and then put it in the oven at 150°C Bake for 1 hour, the die-bonding glue solidifies, and the chip is firmly fixed on the circuit board;

(3) Bonding wires, bonding the chip electrodes and the corresponding electrodes of the circuit board to the wires on the bonding table to complete the circuit connection;

(4) Encapsulate the basic glue layer, fix the qualified circuit board on the frame, the frame and the circuit board form a cavity, pour transparent glue in the cavity, let it stand for 3-5 hours, wait for it to cure, and then apply the transparent glue A layer of fluorescent powder glue is laid on the layer.

The circuit board described in the present invention adopts a copper-clad board, and the surface of the pad is plated with gold. The use of aluminum substrates can reduce the operating temperature of the system, but the cost will increase. The surface of the pad can be plated with nickel or bare copper, or aluminum. Materials that are not easy to rust, easy to bond, and have high reflectivity are preferred. The frame is made of white PVC or other materials, and the materials that meet the following conditions are preferred: sufficient strength, flame retardant, temperature resistance -60 ° C ~ 100 ° C, anti-aging, good thermal conductivity, easy processing and connection. The color of the inner side is preferably white. The inner surface participates in multiple reflections of light in various wavelength bands in the light source module, and its reflective performance can affect the light mixing effect and the emitted light flux of the entire light source module. White high-temperature ink is used for the white crystal-bonding glue, and transparent epoxy resin is used for the transparent crystal-bonding glue. Organic silica gel or epoxy resin is selected; the phosphor powder glue is prepared by blending epoxy resin and phosphor powder in a ratio of 100:1-100:5 by weight. Phosphor powder glue can also be prepared by blending organic silica gel and phosphor powder at a weight ratio of 100:1-100:5, and then laying a layer of epoxy resin or transparent glass or transparent acrylic on the phosphor powder glue layer.

Compared with the prior art, the present invention has achieved the following beneficial effects:

1. In the present invention, multi-particle low-power LED chips are scattered and distributed on the circuit board, and are packaged together to form a high-power LED light source, so that the heat source is dispersed and distributed, the calorific value per unit area is reduced, and the heat dissipation requirement standard is lowered. The low-power chip generates low heat, and can quickly spread the heat to the entire surface of the circuit board through the copper clad layer of the circuit board. The heat dissipation is realized through the surface of the circuit board hundreds of times larger than the chip area, which can effectively reduce the operating temperature of the system. Generally, the temperature can be controlled below 50°C. In the light source module of the present invention, the LED is directly packaged on the circuit board, and the circuit board serves as a heat dissipation path, thereby avoiding additional heat dissipation costs. Compared with the high-power light source combined with LED single lamp, the bonding of LED chips on the bracket and the series-parallel connection on the circuit board are combined into one process, which reduces the production process and reduces the production cost. Compared with high-power chip LED light sources, it also brings more significant cost reduction because of the low cost of the chip and the omission of the package for packaging.

2. The present invention uses white colloid as the crystal-bonding glue, and uses a transparent substrate LED chip (such as the current sapphire substrate chip). The light emitted from the back of the chip is efficiently emitted through the white crystal-bonding glue. The conductive glue (gray) absorbs almost all the light emitted from the back of the chip, and experiments have proved that the utilization rate of more than 70% of the light emitted from the back can be increased by using the method of the present invention to bond the crystal. In addition, white solder resist is applied to the outside of the pad on the surface of the circuit board, and the inner side of the light source block frame is white, which will reduce the absorption loss during light reflection in the system. When the chip is fixed on the white solder resist of the circuit board, the crystal-bonding adhesive can also be a transparent colloid, and the light emitted from the back of the chip can be emitted by using the white solder resist.

3. The encapsulation of the basic glue layer of the present invention keeps a relatively large distance between the phosphor layer and the chip, and fills the middle with transparent glue. The thickness of the transparent glue layer is generally more than 4mm, so that the light emitted by the chip can reach the fluorescent powder glue layer. Can be dispersed over an area hundreds of times larger than the surface area of the chip. Phosphor powder is evenly dispersed on the surface of the light source which is hundreds of times larger than the area of the chip. The ratio of phosphor powder glue is generally 100:1~100:5 (the weight percentage of transparent glue and phosphor powder), which is higher than that of traditional white LED phosphor powder glue. The concentration is dozens of times lower. The thickness of the fluorescent powder adhesive layer is generally controlled below 2 mm. However, the surface area of the fluorescent powder adhesive layer in traditional LED packaging is only ten to dozens of times the surface area of the chip. Therefore, the microscopic light source points are evenly distributed on a larger area, and the luminous intensity per unit area is reduced. The luminous flux per unit area of the traditional LED light source is generally above 1001m/cm ² , but the luminous flux per unit area of the light source of the present invention is generally less than 51m/cm ² , so glare can be overcome.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the structural representation of unencapsulated basic adhesive layer of the present invention;

Fig. 3 is the circuit board structure schematic diagram among the present invention;

Fig. 4 is a schematic diagram of the chip fixing structure in the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

First select the chip and phosphor and design and make the circuit board. This embodiment uses a 460-465nm band blue light chip, the chip normal light intensity is 160-180mcd, the voltage range is 3.0-3.5V, the chip size is 14×14mil, and phosphor powder that can be excited by 460-465nm light is used, such as Taiwan Hongdae's TMT-00432-6065 phosphor. In this embodiment, the circuit board is designed and produced according to the requirements of power 1W and voltage 12V. As shown in Figure 3, a circuit structure with four groups connected in series and 8 chips connected in parallel in each group is adopted. In the figure, 8 is the copper clad layer of the circuit board, 9 is the substrate of the circuit board, and 10 is the pad. In this embodiment, the circuit board adopts a half-glass fiber copper-clad laminate, the pad 10 is plated with gold, and a white solder resist is applied on the outside of the pad.

Then, as shown in FIG. 4 , the LED chip is fixed on the copper clad layer 8 of the circuit board with white high-temperature ink as the crystal-bonding glue 7 , and the upper lead 4 is bonded to complete the circuit connection.

As shown in Figure 1 and Figure 2, fix the above-mentioned circuit board on the frame 1, the frame 1 is made of white PVC flame-retardant engineering material, and the organic silica gel 5 with a thickness of 4.5 mm is poured into the cavity formed by the frame 1 and the circuit board 2, Phosphor powder glue 6 is laid on the organic silica gel 5, and the thickness of the phosphor powder glue layer is 1.5 mm. The phosphor powder adhesive is prepared by mixing epoxy resin and phosphor powder in a ratio of 100:4 by weight. Of course, the fluorescent powder glue can also be prepared by blending organic silica gel and fluorescent powder, and then laying a layer of epoxy resin or pasting transparent glass, transparent acrylic and other materials on it.

When powered on, the chip 3 emits blue light, most of the blue light is directly emitted to the phosphor adhesive layer through the transparent adhesive layer, and the other part of the blue light reaches the phosphor adhesive layer after being reflected by the circuit board or the frame. A small part of the blue light is reflected on the phosphor layer or emitted directly through it, and most of the blue light is absorbed by the phosphor to excite green, yellow or red light. The excited light is divided into parts and directly emitted to the outside of the light source block, and part of the light is emitted to the inside of the light source block and emitted to the outside of the light source block after reflection and refraction. Therefore, the light emitted by this light source block points to any direction centered on the phosphor layer.

The input power of the light source block in this embodiment is 1W, and the luminous area is up to 21cm ² . If the luminous efficiency is 701m/W, the luminous flux per unit area is about 3.31m/cm ² , so the light is soft and glare-free. The input power of the light source block is 1W, and the heat dissipation area is 25cm ² . The measurement result in actual use shows that when the ambient temperature is 25°C, the surface temperature of the light source block can be stabilized below 40°C.

Claims (5)

1, a kind of packaging method of white light LED surface light source module, is characterized in that it is made up of following processing steps: (1) Make a circuit board, select the chips that meet the requirements, and distribute the multi-particle low-power LED chips on the circuit board according to the principle of uniform distribution of chips, and put a white solder mask on the outside of the pad on the surface of the circuit board; (2) Solid crystal, use white or transparent glue as the solid crystal glue, apply glue evenly on the back of the chip, bond the chip to the corresponding position of the pad on the circuit board on the solid crystal table, and then put it in the oven at 150°C Bake for 1 hour, the die-bonding gel solidifies, and the chip is firmly fixed on the circuit board; (3) Bonding wires, bonding the chip electrodes and the corresponding electrodes of the circuit board to the wires on the bonding table to complete the circuit connection; (4) Encapsulate the basic glue layer, fix the qualified circuit board on the frame, the frame and the circuit board form a cavity, pour transparent glue in the cavity, let it stand for 3-5 hours, wait for it to cure, and then apply the transparent glue A layer of fluorescent powder glue is laid on the layer. 2. The packaging method of the LED surface light source module according to claim 1, wherein the circuit board is made of a copper clad laminate, and the surface of the pad is plated with gold. 3. The packaging method of LED surface light source module according to claim 1, characterized in that: the frame and the circuit board in step (4) form a cavity with a depth of 6-20mm, and transparent glue is poured into the cavity, transparent The thickness of the adhesive layer is not less than 4mm, and the thickness of the fluorescent powder adhesive layer is not greater than 2mm. 4. The packaging method of white LED surface light source module according to claim 1, characterized in that: said fluorescent powder glue is prepared by blending epoxy resin and fluorescent powder in a weight percentage ratio of 100:1-100:5. 5. The packaging method of white LED surface light source module according to claim 1, characterized in that: the fluorescent powder glue is prepared by blending organic silica gel and fluorescent powder in a ratio of 100:1-100:5 by weight, and then A layer of epoxy resin or transparent glass or transparent acrylic is laid on the fluorescent powder adhesive layer.

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