A flip-chip SMD packaging method

Abstract

A flip-chip SMD packaging method includes the following steps: (1) fixing a fluorescent sheet in a bowl of a bracket, wherein a limiting groove is provided in the middle of the fluorescent sheet, and a solder pad at the bottom of the bracket is exposed from the limiting groove; (2) applying solder paste or flux on the solder pad; (3) heating the bracket; (4) placing a flip-chip with solid solder paste into the limiting groove; (5) applying downward pressure to the flip-chip to heat and melt the solder paste to achieve welding; (6) applying fluorescent glue in the bowl and curing. The present invention first fixes the fluorescent sheet in the bowl of the bracket. The limiting groove provided on the fluorescent sheet can constrain the position of the flip-chip, improve the accuracy of the die bonding position, and solve the problem of flip-chip offset, thereby ensuring welding quality. The fluorescent sheet, as part of the light distribution structure, can achieve layered glue dispensing, solving the problem of mixed excitation of different phosphors affecting the excitation efficiency.

Description

Technical Field

[0001] The present invention relates to the field of LEDs, in particular to a flip-chip SMD packaging method. Background Art

[0002] SMD LEDs (Surface-Modulated Device LEDs) are primarily used in lighting systems, decoration, electronic device indicators, backlighting, displays, and appliances. Flip-chip LEDs are a mature product, such as the chip LED package structure described in Chinese Patent Publication No. CN206516658U. This structure comprises an LED holder and a flip-chip LED chip. The LED holder includes a holder cup and first and second electrodes at the bottom of the holder cup. The first and second electrodes serve as the positive and negative electrodes of the LED holder, respectively. The surfaces of the first and second electrodes are coated with solder paste. The positive and negative electrodes of the flip-chip LED chip are fixed to two electrodes located on the upper surface of the solder paste, corresponding to the positions of the first and second electrodes. A fluorescent colloid is encapsulated within the holder cup and covers the flip-chip LED chip. The upper end of the fluorescent colloid is cured in a mold to form a transparent colloid with a specific shape. During packaging, the flip-chip is soldered with solder paste. Since the molten solder paste flows, the chip can be easily deflected by the flowing solder paste, resulting in chip shift, which not only affects the appearance but can also lead to leakage in severe cases. In addition, different phosphors in the fluorescent glue are mixed together and excited. The long-wave phosphors (such as red phosphors) absorb the short-wave blue light of the LED chip, and the red-pink phosphors not only absorb blue light, but also absorb the light emitted by short-wave phosphors (such as yellow-green phosphors). When different phosphors are mixed together, the phosphors will absorb each other, resulting in the loss of light energy. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a flip-chip SMD packaging method to avoid the leakage problem caused by the offset of the flip-chip packaging; at the same time, it realizes layered dispensing and improves the product excitation efficiency.

[0004] To solve the above technical problems, the technical solution of the present invention is: a flip-chip SMD packaging method, comprising the following steps:

[0005] (1) Fix the fluorescent sheet in the bowl of the bracket. A limiting groove is provided in the middle of the fluorescent sheet, and the solder pad at the bottom of the bracket is exposed from the limiting groove;

[0006] (2) Apply solder paste or flux to the pad;

[0007] (3) Heating bracket;

[0008] (4) Place the flip chip with solid solder paste into the limiting groove;

[0009] (5) Apply downward pressure to the flip chip to heat and melt the solder paste to achieve welding;

[0010] (6) Apply fluorescent glue inside the bowl and solidify it.

[0011] The present invention first fixes the fluorescent sheet in the bowl of the bracket. The limiting groove opened on the fluorescent sheet can constrain the position of the flip chip, improve the accuracy of the solid crystal position, and solve the problem of flip chip offset, thereby ensuring the welding quality. In addition, as part of the light distribution structure, the fluorescent sheet can realize layered dispensing, solving the problem of mixed excitation of different phosphors affecting the excitation efficiency.

[0012] As an improvement, the bracket includes an electrode plate and a plastic frame injection-molded integrally with the electrode plate, and the electrode plate and the plastic frame form the bowl cup; the electrode plate is separated into a positive plate and a negative plate by an insulating tape, and the top surface of the positive plate is provided with a positive electrode welding pad, and the top surface of the negative plate is provided with a negative electrode welding pad; the inner wall of the bowl cup is a slope.

[0013] As an improvement, the fluorescent sheet is a glass fluorescent sheet or a ceramic fluorescent sheet.

[0014] As an improvement, the fluorescent sheet is a red fluorescent sheet mixed with red fluorescent powder.

[0015] As an improvement, the bowl and cup enclose a functional area, and the shape of the fluorescent sheet is similar to that of the functional area.

[0016] As an improvement, the fluorescent sheet is fixed by glue.

[0017] As an improvement, the shape of the flip chip is similar to that of the limiting groove, and the top surface of the flip chip is higher than the top surface of the fluorescent sheet.

[0018] As an improvement, two positive electrodes and two negative electrodes are respectively provided at the bottom of the flip chip.

[0019] As an improvement, the bracket is placed on a heating plate for heating, and the heating plate moves along with the die-bonding position.

[0020] As an improvement, the flip chip is placed in the limiting groove by a die-bonding robot, and pressure is applied by the die-bonding robot.

[0021] The beneficial effects brought about by the present invention compared with the prior art are:

[0022] The present invention first fixes the fluorescent sheet in the bowl of the bracket. The limiting groove opened on the fluorescent sheet can constrain the position of the flip chip, improve the accuracy of the solid crystal position, and solve the problem of flip chip offset, thereby ensuring the welding quality. In addition, as part of the light distribution structure, the fluorescent sheet can realize layered dispensing, solving the problem of mixed excitation of different phosphors affecting the excitation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a top view of the flip-chip SMD package.

[0024] Figure 2 This is a cross-sectional view of a flip-chip SMD package. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings.

[0026] like Figure 1 、 2 As shown, a flip-chip SMD package includes a bracket 1 and a flip chip 2. The bracket 1 is a patch-type bracket 1, which includes an electrode plate 12 and a plastic frame 11 integrally injection-molded with the electrode plate 12. The electrode plate 12 and the plastic frame 11 form a bowl, and the area enclosed by the bowl is a functional area for die bonding. The electrode plate 12 is separated into a positive plate and a negative plate by an insulating tape 13. The top surface of the positive plate is provided with a positive electrode pad, and the top surface of the negative plate is provided with a negative electrode pad. The positive electrode pad and the negative electrode pad are symmetrically distributed with the insulating tape 13 as the center. In this embodiment, there are two positive electrode pads and two negative electrode pads. The bowl is in the shape of an inverted cone, and the inner wall of the bowl is an inclined surface. A fluorescent sheet 3 is provided in the bowl cup, and the shape of the fluorescent sheet 3 is similar to that of the functional area. When the fluorescent sheet 3 is fixed in the bowl cup, the outer edge of the fluorescent sheet 3 is basically in contact with the inner wall of the bowl cup, which is convenient for positioning the fluorescent sheet 3, and the inclined inner wall of the bowl cup also helps to guide the fluorescent sheet 3; the fluorescent sheet 3 is fixed to the functional area by glue, and the fluorescent sheet 3 can be automatically assembled by a robot; a rectangular limiting groove 31 is provided in the middle of the fluorescent sheet 3, and the shape of the limiting groove 31 is similar to that of the flip chip 2. The limiting groove 31 can not only expose the solder pad position, but also constrain the position of the flip chip 2; the fluorescent sheet 3 is a glass fluorescent sheet or a ceramic fluorescent sheet, which is formed by cutting; the fluorescent sheet 3 is a red fluorescent sheet mixed with red fluorescent powder, and then green fluorescent glue 4 is applied in the bowl cup to realize a layered glue application process, and the LED excites the red fluorescent powder and the green fluorescent powder respectively, thereby improving the excitation efficiency; after the flip chip 2 is installed in the limit, the top surface of the flip chip 2 is higher than the top surface of the fluorescent sheet 3. The flip chip 2 is a blue light chip, and the bottom of the flip chip 2 is respectively provided with two positive electrodes 22 and two negative electrodes 21. The four electrodes are distributed in a rectangular shape. The electrodes are welded to the pads on the electrode plate 12 through solder paste, which can restrain the chip offset to a certain extent. Before packaging, the positive and negative electrodes of the flip chip 2 are provided with solid solder paste, and welding is achieved by heating the solder paste to melt it during packaging.

[0027] The packaging process of the present invention comprises the following steps:

[0028] (1) Fix the fluorescent sheet 3 in the bowl of the bracket 1. A limiting groove 31 is provided in the middle of the fluorescent sheet 3. The solder pad at the bottom of the bracket 1 is exposed from the limiting groove 31.

[0029] (2) Apply solder paste or flux to the pad;

[0030] (3) Place the bracket 1 on the heating plate and heat it. The heating plate moves along with the position of the die bonding. Keep the heating plate heated at all times until the temperature of the bracket 1 reaches the melting point of the tin solder.

[0031] (4) Using a die-bonding robot, place the flip chip 2 with solid solder paste into the limiting groove 31;

[0032] (5) The die-bonding robot applies downward pressure to the flip chip 2 while bonding the die, so that the solder paste is heated and melted to achieve welding;

[0033] (6) Apply green fluorescent glue to the bowl and solidify it;

[0034] (7) Stripping;

[0035] (8) Spectroscopic testing;

[0036] (9) Packaging.

[0037] The present invention first fixes the fluorescent sheet 3 in the bowl of the bracket 1. The limiting groove 31 opened on the fluorescent sheet 3 can constrain the position of the flip chip 2, improve the accuracy of the solid crystal position, and solve the problem of the offset of the flip chip 2, thereby ensuring the welding quality. In addition, the fluorescent sheet 3, as part of the light distribution structure, can realize layered dispensing, with green phosphor on the upper part and red phosphor on the lower part, thereby solving the problem of mixed excitation of different phosphors affecting the excitation efficiency.

Claims

1. A flip-chip SMD packaging method, characterized in that: The following steps are involved: (1) Fix the fluorescent sheet in the bowl of the bracket. A limiting groove is provided in the middle of the fluorescent sheet, and the solder pad at the bottom of the bracket is exposed from the limiting groove; (2) Apply solder paste or flux to the pad; (3) Heating bracket; (4) Place the flip chip with solid solder paste into the limiting groove; (5) Apply downward pressure to the flip chip to heat and melt the solder paste to achieve welding; (6) Apply fluorescent glue to the bowl and solidify it; The bracket includes an electrode plate and a plastic frame integrally injection-molded with the electrode plate, the electrode plate and the plastic frame forming the bowl; the electrode plate is separated into a positive electrode plate and a negative electrode plate by an insulating tape, the top surface of the positive electrode plate is provided with a positive electrode welding pad, and the top surface of the negative electrode plate is provided with a negative electrode welding pad; the inner wall of the bowl is an inclined surface; The fluorescent sheet is a glass fluorescent sheet or a ceramic fluorescent sheet; The fluorescent sheet is a red fluorescent sheet mixed with red fluorescent powder; The bowl and cup form a functional area, and the shape of the fluorescent sheet is similar to that of the functional area; The fluorescent sheet is fixed by glue; The shape of the flip chip is similar to that of the limiting groove, and the top surface of the flip chip is higher than the top surface of the fluorescent sheet; The bottom of the flip chip is provided with two positive electrodes and two negative electrodes respectively; The bracket is placed on a heating plate for heating, and the heating plate moves along with the die bonding position; The flip chip is placed in the limiting groove by a die-bonding robot, and pressure is applied by the die-bonding robot.

Images