A method for preparing a four-sided luminous white light CSP and the prepared CSP

Abstract

The present invention discloses a method for preparing a four-sided emitting white light CSP, comprising the following steps: S1 flip-chip LED chip; S2 fluorescent film is placed on the light-emitting side surface of the LED chip; S3 pressing to make the fluorescent film and the LED chip completely attached; S4 filling transparent glue into the gap of the fluorescent film; S5 encapsulating the reflective adhesive film on the fluorescent film and the transparent glue upper surface; S6 cutting to obtain an independent four-sided emitting white light CSP. The present invention heat presses the fluorescent film on the surface of the LED chip, and then fills the transparent glue into the gap of the fluorescent film to the same height as the fluorescent film. The prepared four-sided emitting white light CSP has a small tolerance and high light color consistency. It has good operability for ultra-thin fluorescent films. Compared with the conventional four-sided emitting white light CSP side fluorescent layer thickness tolerance of ±30um, the fluorescent layer thickness tolerance of the present invention is only ±5um, which greatly improves the light color consistency.

Description

Technical Field

[0001] The invention relates to a preparation method of a four-sided luminous white light CSP and the prepared CSP, and in particular to the field of semiconductor devices. Background Art

[0002] CSP (chip-scale packaging) is the latest generation of memory chip packaging technology, which can reduce the size of the package and increase the packaging capacity. With the widespread application of electronic integrated equipment, the size of electronic technology products is getting smaller and smaller, and the application of CSP packaging is becoming more and more extensive. In the existing CSP packaging technology, after the LED chips are arranged, the LED light source is wrapped with a fluorescent film in the traditional process, so that a soft and uniform surface light source can be output. However, when cutting into independent light sources, due to the chip itself and the cutting error, the thickness of the cut fluorescent film will be inconsistent, resulting in inconsistent color difference of the surface light source, which will affect the luminous state of the product in subsequent use, especially for chips with increasingly thin thickness. The impact of the error is very large. Therefore, it is crucial to reduce the difficulty of processing and reduce the impact of errors.

[0003] Chinese invention patent CN202223149984.9 discloses an LED four-sided light-emitting device, which uses the inclined fluorescent glue layer coated on the four sides of the LED chip as a fluorescent light source that diverges on the four sides, and the white glue layer above blocks the light output upward. Under the joint action of the four-sided light-emitting structure, a soft and uniform surface light source is obtained, and a similar optical effect can be achieved without using a QD quantum film, which effectively reduces the manufacturing cost of CSP TV module products. However, the operation difficulty of cutting into independent CSP light sources is high, and the light color is prone to inconsistency. Chinese invention patent CN202310827680.3 discloses a white light CSP suitable for high-power single-sided light emission and its packaging method, which uses a fluorescent film and a diffusion film made of a specific semi-solid hot-melt silicone film. After the crystal solidification process, the LED chip is heated and fixed on the fluorescent film, and no transparent glue for bonding is needed, which effectively improves the heat dissipation efficiency and alleviates the heat congestion effect, thereby improving the reliability of the LED integrated circuit chip. However, the light-emitting chip formed can only emit light on one side. Summary of the invention

[0004] In order to optimize the light color consistency of a four-sided white light CSP, a first aspect of the present invention provides a method for preparing a four-sided white light CSP, comprising the following steps:

[0005] S1: Arrange the flip-chip LED chips in an array on the substrate, with the electrode side of the LED chips facing the substrate and the light-emitting side surface facing upward;

[0006] S2 prepares a fluorescent film and places the fluorescent film on the light-emitting side surface of the LED chip;

[0007] S3: placing the substrate, LED chip and fluorescent film in a high-temperature vacuum pressing machine in sequence, and after pressing, the fluorescent film and the LED chip are completely attached;

[0008] S4 prepares transparent glue, and fills the transparent glue into the gap of the fluorescent film, and the transparent glue is at the same height as the fluorescent film;

[0009] S5 prepares the reflective adhesive film, and seals it on the surface of the fluorescent film and the transparent adhesive through a high-temperature vacuum pressing machine;

[0010] S6 cuts the transparent adhesive, removes the substrate, and obtains an independent four-sided white light CSP.

[0011] As a preferred implementation, the fluorescent film in step S2 is a semi-solid hot-melt silicone film, and the viscosity of the semi-solid hot-melt silicone film is 2000-8000 mPa·s at 70-100°C.

[0012] The fluorescent film has no stickiness on the surface at room temperature, but becomes slightly sticky at a controllable temperature. After vacuum pressing, the fluorescent film becomes deformed and sticky due to heat and pressure, and is completely attached to the wafer.

[0013] As a preferred implementation, the thickness of the fluorescent film in step S2 is 50-200 μm, and the thickness tolerance is ±5 μm.

[0014] As a preferred implementation, the thickness of the fluorescent film in step S2 is 95-105 μm, and the thickness tolerance is ±5 μm.

[0015] As a preferred embodiment, the raw materials for preparing the fluorescent film in step S2 include 10-90 parts by weight of silica gel and 10-90 parts of fluorescent powder.

[0016] As a preferred embodiment, the phosphor is selected from one or a combination of YAG phosphor, nitride phosphor, and silicate phosphor.

[0017] As a preferred implementation, the fluorescent film is prepared by mixing fluorescent powder and silica gel evenly, coating and curing, thereby obtaining the fluorescent film.

[0018] As a preferred embodiment, the transparent adhesive is a two-component silicone rubber. The preparation method of the transparent adhesive is to mix the two components evenly and then apply them to obtain the transparent adhesive.

[0019] As a preferred implementation, the transparent adhesive is filled by dispensing or film pressing.

[0020] As a preferred implementation, the transparent adhesive is filled by film pressing.

[0021] As a preferred implementation, the thickness of the reflective adhesive film in step S5 is 100-200 μm.

[0022] As a preferred implementation, the thickness of the reflective adhesive film in step S5 is 80-120 μm.

[0023] As a preferred embodiment, the raw materials for preparing the reflective adhesive film in step S5 include 50-80 parts by weight of silica gel and 20-50 parts of titanium dioxide.

[0024] As a preferred implementation, the preparation method of the reflective adhesive film is: mixing silica gel and titanium dioxide evenly, coating and curing, to obtain the reflective adhesive film.

[0025] During the experiment, the applicant found that by hot-pressing a fluorescent film on the surface of the LED chip and then filling transparent glue into the gap of the fluorescent film to the same height as the fluorescent film, the four-sided white light CSP prepared had a smaller tolerance and high light color consistency. The possible reason is that transparent glue is set on the periphery of the fluorescent film to fill the gap. When the wafer is cut, the cutting part of the present application is the transparent glue part, and the fluorescent film will not be cut, and the light color consistency will not be affected. Compared with the prior art, during the cutting process, both solid crystal and cutting will cause deviations. During cutting, the fluorescent film may be cut, reducing the light color consistency of the four-sided white light CSP. The process operability of the present application for processing luminous LED chips is higher, especially for ultra-thin fluorescent films, and it is more applicable.

[0026] As a preferred implementation, in step S1, the substrate comprises a tape layer and a hard substrate, and the tape layer is a double-sided tape.

[0027] As a preferred embodiment, the double-sided tape is selected from one or a combination of UV tape, pyrolytic tape, and heat-resistant tape.

[0028] As a preferred embodiment, the hard substrate is selected from one or a combination of glass, ceramic, FR4 grade resin composite material, BT resin-based copper clad laminate.

[0029] The second aspect of the present invention provides a CSP light source, which is prepared by using the method for preparing the four-sided emitting white light CSP.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The method for preparing the four-sided white light CSP of the present invention uses a semi-solid hot-melt silicone film with a viscosity of 2000-8000 mPa·s at 70-100°C to prepare a fluorescent film. After high-temperature vacuum pressing, the fluorescent film is deformed and becomes sticky due to heat and pressure, and is completely attached to the chip to achieve tight packaging.

[0032] (2) The method for preparing the four-sided white light CSP of the present invention comprises hot pressing a fluorescent film on the surface of an LED chip, and then filling transparent glue into the gap of the fluorescent film to the same height as the fluorescent film. The prepared four-sided white light CSP has a small tolerance and high light color consistency.

[0033] (3) The preparation method of the four-sided white light CSP of the present invention has good operability for ultra-thin fluorescent films. Compared with the thickness tolerance of the fluorescent layer on the side of the conventional four-sided white light CSP of ±30um, the thickness tolerance of the fluorescent layer of the present invention is only ±5um, which greatly improves the consistency of light color. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The preparation flow chart of the four-sided white light CSP;

[0035] Figure 2 The schematic diagram of the structure of step S1 of the method for preparing a four-sided white light CSP;

[0036] Figure 3 The schematic diagram of the structure of step S2 of the method for preparing a four-sided white light CSP;

[0037] Figure 4 The structure diagram of step S3 of the method for preparing a four-sided white light CSP;

[0038] Figure 5 The structure diagram of step S4 of the method for preparing a four-sided white light CSP;

[0039] Figure 6 The schematic diagram of the structure of step S5 of the method for preparing a four-sided white light CSP;

[0040] Figure 7 It is a structural schematic diagram of step S6 of the method for preparing a four-sided emitting white light CSP.

[0041] Figure 8 The figure is a schematic diagram of the process structure of the preparation method of the white light CSP using the traditional technology.

[0042] In the figure:

[0043] 1. LED chip; 2. Double-sided tape; 3. Hard substrate; 4. Fluorescent film; 5. Transparent tape; 6. Reflective film. DETAILED DESCRIPTION

[0044] Example 1

[0045] A method for preparing a four-sided luminous white light CSP comprises the following steps:

[0046] S1: Arrange the flip-chip LED chips 1 in an array on the substrate, with the electrode side of the LED chip 1 facing the substrate and the light-emitting side surface facing upward;

[0047] S2 prepares the fluorescent film 4 and places the fluorescent film 4 on the light-emitting side surface of the LED chip 1;

[0048] S3: placing the substrate, the LED chip 1, and the fluorescent film 4 in a high-temperature vacuum pressing machine in sequence, and pressing the fluorescent film 4 to completely adhere to the LED chip 1;

[0049] S4: preparing a transparent adhesive 5, and filling the transparent adhesive 5 into the gap of the fluorescent film 4, so that the transparent adhesive 5 is at the same height as the fluorescent film 4;

[0050] S5 prepares a reflective adhesive film 6 and seals it on the surface of the fluorescent film 4 and the transparent adhesive 5 through a high-temperature vacuum press;

[0051] S6 cuts the transparent adhesive 5 and removes the substrate to obtain an independent four-sided white light CSP.

[0052] In the step S2, the fluorescent film 4 is a semi-solid hot-melt silicone film, and the viscosity of the semi-solid hot-melt silicone film is 2000-8000 mpa·s under the condition of 70-100°C.

[0053] In the step S2 , the thickness of the fluorescent film 4 is 100 μm, and the thickness tolerance is ±5 μm.

[0054] In the step S2, the raw materials for preparing the fluorescent film 4 include 50 parts by weight of silica gel and 50 parts of fluorescent powder.

[0055] The phosphor is Interma YAG-05, purchased from Shenzhen Geliang Optoelectronics Co., Ltd.

[0056] The silica gel is CL-1000, purchased from Coposi Electronic Materials Zhangjiagang Co., Ltd.

[0057] The preparation method of the fluorescent film 4 is: mixing fluorescent powder and silica gel evenly, coating and curing, and then obtaining the fluorescent film.

[0058] The transparent adhesive 5 is a two-component silicone rubber, model Dow Corning OE-6550, purchased from Cobosi Electronic Materials Zhangjiagang Co., Ltd. The preparation method of the transparent adhesive 5 is to mix the two components evenly and then apply them to obtain the transparent adhesive.

[0059] The transparent adhesive 5 is filled by film pressing.

[0060] In the step S5 , the thickness of the reflective adhesive film 6 is 100 μm.

[0061] In step S5, the raw materials for preparing the reflective adhesive film 6 include 70 parts by weight of silica gel and 30 parts by weight of titanium dioxide.

[0062] The silica gel is Dow Corning OE-6550, purchased from Coposi Electronic Materials Zhangjiagang Co., Ltd.

[0063] The titanium dioxide is titanium dioxide, which was purchased from Wuhu Xinda New Material Technology Co., Ltd.

[0064] The preparation method of the reflective adhesive film 6 is: uniformly mix silica gel and titanium dioxide, apply and solidify, and then obtain the reflective adhesive film 6.

[0065] In the step S1, the substrate includes a tape layer and a hard substrate 3, wherein the tape layer is a heat-resistant double-sided tape 2 purchased from Shenzhen Kehongjian Technology Co., Ltd.

[0066] The hard substrate 3 is glass, purchased from Dongguan Jiamite Glass Co., Ltd.

[0067] Example 2

[0068] A method for preparing a four-sided white light CSP, the specific implementation method is the same as that of Example 1, except that the thickness of the fluorescent film in step S2 is 95 μm.

[0069] Example 3

[0070] A method for preparing a four-sided white light CSP, the specific implementation method is the same as that of Example 1, except that the thickness of the fluorescent film in step S2 is 105 μm.

[0071] Comparative Example 1

[0072] A method for preparing a four-sided luminous white light CSP, the specific implementation method is the same as that of Example 1, except that the thickness of the fluorescent film in step S2 is 70 μm.

[0073] Comparative Example 2

[0074] A method for preparing a four-sided luminous white light CSP, the specific implementation method is the same as that of Example 1, except that the thickness of the fluorescent film in step S2 is 130 μm.

[0075] Performance Testing

[0076] CIE test: 20 samples were tested for each embodiment and comparative example, and the average value of the measured values ​​was recorded in Table 1.

[0077] Test method: Weld CSP on a hexagonal plate, place it in a remote integrating sphere HAAS-2000, and test CIE. In the CIE-1931 coordinate system, with the target CIE as the center, the color tolerance SDCM ≤ 3 is qualified.

[0078] Table 1

[0079]

Claims

1. A method for preparing a four-sided luminous white light CSP, characterized in that: The following steps are involved: S1: Arrange the flip-chip LED chips in an array on the substrate, with the electrode side of the LED chips facing the substrate and the light-emitting side surface facing upward; S2 prepares a fluorescent film and places the fluorescent film on the light-emitting side surface of the LED chip; S3: placing the substrate, LED chip and fluorescent film in a high-temperature vacuum pressing machine in sequence, and after pressing, the fluorescent film and the LED chip are completely attached; S4 prepares transparent glue, and fills the transparent glue into the gap of the fluorescent film, and the transparent glue is at the same height as the fluorescent film; S5 prepares the reflective adhesive film, and seals it on the surface of the fluorescent film and the transparent adhesive through a high-temperature vacuum pressing machine; S6 cuts the transparent adhesive and removes the substrate to obtain an independent four-sided white light CSP; In step S2, the fluorescent film is a semi-solid hot-melt silicone film, and the viscosity of the semi-solid hot-melt silicone film is 2000-8000 mpa·s under the condition of 70-100° C.; The thickness of the fluorescent film in step S2 is 100 μm; The raw materials for preparing the fluorescent film in step S2 include 50 parts of silica gel and 50 parts of fluorescent powder in parts by weight; The transparent glue is a two-component silica gel; The thickness of the reflective film in step S5 is 100 μm; The raw materials for preparing the reflective adhesive film in step S5 include 70 parts by weight of silica gel and 30 parts of titanium dioxide.

2. The method for preparing the four-sided emitting white light CSP according to claim 1, characterized in that: In step S1, the substrate includes a tape layer and a hard substrate, and the tape layer is a double-sided tape.

3. The method for preparing the four-sided emitting white light CSP according to claim 2, characterized in that: The double-sided tape is selected from one or a combination of UV tape, pyrolytic tape, and heat-resistant tape.

4. The method for preparing the four-sided emitting white light CSP according to claim 2, characterized in that: The hard substrate is selected from one or a combination of glass, ceramic, FR4 grade resin composite material, BT resin-based copper clad laminate.

5. A CSP light source, characterized in that: The white light CSP is prepared by the method for preparing the four-sided luminous white light CSP according to any one of claims 1 to 4.

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