A packaging method of an RFID chip

Abstract

The present application relates to the technical field of chip packaging, and particularly relates to a packaging method of RFID chip. The present application combines the conductor layer on the pad of the RFID chip, so that the packaging size of the RFID chip is larger than its physical size, that is, the RFID chip with ultra-small size is changed into the RFID chip with regular size or even larger size, thereby reducing the packaging difficulty, getting rid of the dependence on high-precision and expensive equipment, without increasing the equipment procurement cost, depreciation cost and consumable cost, and meanwhile, the packaging speed and labor efficiency are significantly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chip packaging, and in particular to a packaging method for an RFID chip. Background Art

[0002] RFID (Radio Frequency Identification, commonly known as electronic tags) chips generally require only two pads (also known as binding connection points), namely RF + and RF - (like Figure 1 Traditionally, packages are picked up one by one by a nozzle and placed on the empty antenna pads by precise visual positioning (as shown in the figure). Figure 2 The newer DDA (Direct Die Attach) technology uses pins to lift the chip directly from the back of the blue film, allowing it to protrude and simultaneously bond to the antenna while being removed from the film. While this improves efficiency, it still requires a one-by-one approach and the same high precision required for positioning.

[0003] With the continuous advancement of RFID chip technology, chip size is becoming smaller and smaller. Currently, the smallest chip size in the industry has reached approximately 0.26mm×0.26mm. This places higher demands on the positioning accuracy of the packaging and also causes the price of related equipment to continue to rise.

[0004] Existing packaging equipment, whether using a suction head or DDA, generally relies on a serial assembly process for single-chip removal and packaging. This approach presents a significant challenge in today's wafer trays, which can hold 600,000 to 800,000 chips. Even the industry's fastest packaging machines have a theoretical speed of only 100k / h, meaning it still takes approximately six hours to complete the packaging of a single wafer tray.

[0005] While the continued impact of Moore's Law has led to smaller chips and lower manufacturing costs per chip, this has been accompanied by higher costs for packaging equipment and more precise antenna processing, which has offset some of the savings. Given the logistics industry's demand for hundreds of billions of tags, current packaging speeds are clearly insufficient to meet practical application requirements. Summary of the Invention

[0006] In view of this, the present invention aims to provide a packaging method for RFID chips. The packaging method provided by the present invention eliminates the reliance on higher-precision equipment, does not increase equipment procurement costs, depreciation costs, and consumables costs, and significantly improves packaging speed and labor efficiency.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a packaging method for an RFID chip, comprising the following steps:

[0009] A conductive medium is applied to the surface of the RFID chips of the whole wafer with a transfer film and arranged in close contact, and then the film is expanded to form gaps between adjacent RFID chips to obtain a spacer chip assembly;

[0010] Laminating a conductor layer on the surface of the conductive medium of the spacer chip assembly, performing a heat pressing process to solidify the conductive medium and combine the RFID chip and the conductor layer;

[0011] Cutting off the conductor layer between the two pads of the RFID chip, and then dividing the conductor layer along the gap between adjacent chips to form independent improved RFID chips, each of which carries two conductor layers;

[0012] The two conductor layers in each improved RFID chip are used as binding link points for packaging.

[0013] Preferably, the spacing distance between adjacent RFID chips in the spacer chip assembly is 50-100 μm.

[0014] Preferably, the conductive medium includes solder paste or anisotropic conductive adhesive.

[0015] Preferably, the size of the RFID chip is (100-300) μm×(100-300) μm.

[0016] Preferably, the thickness of the conductor layer is 50-80 μm.

[0017] Preferably, the conductor layer comprises metal foil or a multi-layer composite conductive material.

[0018] Preferably, the method of cutting off the conductor layer between the two pads of the RFID chip includes: laser cutting or etching.

[0019] Preferably, dividing the conductor layer along the gaps between adjacent chips comprises dividing the conductor layer along fixed horizontal and vertical paths or along a center line between the gaps between adjacent chips.

[0020] Preferably, the coating thickness of the conductive medium is 10-50 μm.

[0021] The application provides a packaging method of an RFID chip, which combines a conductor layer on the pad of the RFID chip, packages the improved RFID chip, makes the packaging size of the RFID chip larger than the physical size of the RFID chip, that is, changes the RFID chip with an ultra-small size into an RFID chip with a regular size or even a larger size, thereby reducing the packaging difficulty, getting rid of the dependence on high-precision and expensive equipment, and avoiding the increase of equipment procurement cost, depreciation cost and consumable cost.

[0022] At present, the packaging of the RFID chip industry is carried out one by one, and when the packaging is carried out one by one, the size of the RFID chip is smaller and smaller, and the precision requirement of the picking is higher and higher, thereby leading to low packaging efficiency. The application changes the chip with an ultra-small size into a chip with a regular size or even a larger size, thereby significantly improving the packaging speed, greatly shortening the wafer packaging time compared with the existing serial flow operation mode, and better meeting the large-scale label demand.

[0023] The application uses the innovative packaging method to make the ordinary RFID packaging equipment or even the compound machine be used for the packaging of the chip with an ultra-small size, and provides strong support for the large-scale application of the RFID industry.

[0024] The application reduces the operation difficulty of the packaging and improves the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Fig. 1 is a structural schematic diagram of an RFID chip;

[0026] Figure 2 Fig. 2 is a schematic diagram of the RFID chip placed at the air antenna pad;

[0027] Figure 3 Fig. 3 is a structural schematic diagram of a whole wafer with a transfer film and in a close contact arrangement, wherein a is a top view schematic diagram, and b is a sectional view schematic diagram along the wafer diameter;

[0028] Figure 4 Fig. 4 is a structural schematic diagram of a spaced chip assembly, wherein a is a top view schematic diagram, and b is a sectional view schematic diagram along the wafer diameter;

[0029] Figure 5 Fig. 5 is a schematic diagram of the conductive medium surface of the spaced chip assembly pasting a conductor layer, wherein a is a top view schematic diagram, and b is a sectional view schematic diagram along the wafer diameter;

[0030] Figure 6 Fig. 6 is a schematic diagram of cutting the conductor layer between the two pads of the RFID chip, wherein a is a top view schematic diagram, and b is a sectional view schematic diagram after the cutting;

[0031] Figure 7Fig. 2 is a schematic view of the conductor layer being segmented along the gap between adjacent chips, wherein a is a top view and b is a sectional view;

[0032] Figure 8 Fig. 3 is a schematic view of the conductor layer being segmented using fixed horizontal and vertical paths;

[0033] Figure 9 Fig. 4 is a schematic view of the conductor layer being segmented along the centerline between the gap between adjacent chips;

[0034] Figure 10 Fig. 5 is a schematic view of the improved RFID chip after encapsulation, wherein a is a top view and b is a sectional view. DETAILED DESCRIPTION

[0035] The present application provides a method for encapsulating an RFID chip, comprising the following steps:

[0036] After the surface of the RFID chips of the wafer with transfer film and in close contact arrangement is coated with conductive medium, the film is expanded to generate a gap between adjacent RFID chips, thereby obtaining a spaced chip assembly;

[0037] A conductor layer is attached to the surface of the conductive medium of the spaced chip assembly, and heat pressing is performed to solidify the conductive medium and combine the RFID chip with the conductor layer;

[0038] The conductor layer between the two pads of the RFID chip is cut, and the conductor layer is segmented along the gap between adjacent chips, thereby forming an independent improved RFID chip, and each improved RFID chip carries two conductor layers;

[0039] The two conductor layers in each improved RFID chip are used as binding link points for encapsulation.

[0040] In the present application, after the surface of the wafer with transfer film and in close contact arrangement is coated with conductive medium, the film is expanded to generate a gap between adjacent RFID chips, thereby obtaining a spaced chip assembly.

[0041] In the present application, the structure of the wafer with transfer film and in close contact arrangement is shown in Fig. 1, wherein the RFID chips are arranged in close order in the wafer. Figure 3 In the present application, the transfer film is preferably a blue film or a UV film.

[0042] The present invention has no special requirements for the RFID chip; any RFID chip known in the art can be used. In the present invention, the RFID chip has two solder pads, which are used to connect to the air antenna. In the present invention, the dimensions of the RFID chip are preferably (100-300) μm × (100-300) μm. In specific embodiments, the dimensions can be 100 μm × 100 μm, 150 μm × 150 μm, 200 μm × 200 μm, 260 μm × 260 μm, or 300 μm × 300 μm.

[0043] In the present invention, the conductive medium preferably comprises solder paste or anisotropic conductive adhesive. The use of anisotropic conductive adhesive ensures that the conductive medium conducts electricity vertically but does not conduct electricity laterally. In the present invention, the conductive medium is preferably applied with a thickness of 10 to 50 μm, and in specific embodiments, it may be 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm. In the present invention, the conductive medium is applied over an area sufficient to cover all RFID chips.

[0044] The present invention has no special requirements for the specific implementation of the film expansion, and the film expansion method well known in the art can be used. After the film expansion, the RFID chips that were originally closely arranged are separated by a gap, such as Figure 4 In the present invention, the spacing distance between adjacent RFID chips in the spacer chip assembly is preferably 50-100 μm, and in specific embodiments can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm.

[0045] After obtaining the spacer chip assembly, Figure 5 As shown, the present invention adheres a conductor layer to the surface of the conductive medium of the spacer chip assembly, performs a heat pressing process, and solidifies the conductive medium to combine the RFID chip and the conductor layer.

[0046] In the present invention, the conductor layer preferably comprises metal foil or a multilayer composite conductive material. The present invention does not impose any particular restrictions on the specific composition of the conductor layer; any conductive material may be used. In an embodiment of the present invention, it is specifically an Al film on a PET (polyethylene terephthalate) carrier. In the present invention, the thickness of the conductor layer is preferably 50-80 μm, and in specific embodiments, it can be 50 μm, 60 μm, 70 μm, or 80 μm. By controlling the thickness of the conductor layer within this range, the present invention achieves a secure bond with the RFID chip and the air antenna.

[0047] In the present invention, the area of ​​the conductor layer is preferably greater than or equal to the area of ​​the transfer film after expansion. This is because expansion may not be ideal, resulting in uneven placement of chips. The present invention first uses a single, large conductor layer to allow all RFID chips to fit together without regard to accuracy. Machine vision is then used to cut and segment the conductor layer based on chip deviations, improving packaging efficiency.

[0048] The present invention does not impose any particular restrictions on the conditions for the hot pressing treatment, as long as the conductive medium solidifies and a firm bond between the RFID chip and the conductor layer is achieved. In the art, commonly used hot pressing treatment conditions are preferably: a hot pressing temperature of 160-190°C, a pressure of 1-2N, and a time of 6-10 seconds.

[0049] After the RFID chip is combined with the conductor layer, the present invention cuts off the conductor layer between the two pads of the RFID chip (such as Figure 6 shown).

[0050] The present invention preferably uses laser cutting or etching to sever the conductive layer between the two pads of the RFID chip. The purpose of severing the conductive layer between the two pads of the RFID chip is to eliminate the short circuit. The present invention has no specific requirements for the specific implementation conditions of the laser cutting and etching methods, as long as only the conductive layer is cut without damaging the height of the chip itself. For example, the etching method can achieve the purpose of severing the conductive layer between the two pads of the RFID chip by applying a photoresist or photosensitive ink and optical scanning exposure. In the present invention, the etching method has lower costs and higher precision.

[0051] During cutting, the present invention preferably uses machine vision and / or lasers to cut the conductive layer between the two pads of each chip based on the chip's deviation. Because these alignment errors are generally regular and the differences are not too large, the laser basically cuts along a relatively straight path, which is more efficient than completely random alignment.

[0052] After cutting off the conductor layer between the two pads of the RFID chip, the present invention further divides the conductor layer along the gap between adjacent chips to form independent improved RFID chips. Each improved RFID chip carries two conductor layers (such as Figure 7 shown).

[0053] The present invention preferably adopts a fixed horizontal and vertical path or along the center line between adjacent chip gaps to split the conductor layer. In the present invention, the splitting method is the same as the above-mentioned cutting method, and will not be repeated here. When the present invention adopts a fixed horizontal and vertical path for splitting, since the chip position deviation is not too large, the fixed horizontal and vertical path does not affect the cutting path (such as Figure 8 If the conductor layer is divided along the center line between the gaps between adjacent chips, a better effect can be achieved by taking into account the correction of the offset of each chip (as shown inFigure 9 shown).

[0054] In the present invention, the improved RFID chip is larger than the RFID chip. As a preferred embodiment, the improved RFID chip is 50-100 μm larger than the RFID chip, meaning that the side length of the improved RFID chip is 50-100 μm larger than the side length of the RFID chip. In specific embodiments, the improved RFID chip can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm larger than the RFID chip.

[0055] In the present invention, the improved RFID chip is still adhered to the flexible transfer film, and the present invention packages the chip directly or packages the chip after weaving the film.

[0056] During packaging, the present invention uses the two conductor layers in each improved RFID chip as binding connection points for packaging (e.g. Figure 10 shown).

[0057] In the present invention, since the size of the improved RFID chip is larger than that of the original RFID chip, the present invention can use ordinary RFID packaging without purchasing expensive high-precision packaging equipment. When the size of the improved RFID chip is large enough, it can even be packaged using only a compound machine.

[0058] The improved RFID chip and the packaging method of the RFID chip provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0059] Example 1

[0060] A packaging method for an RFID chip, comprising the following steps:

[0061] Solder paste was applied to the surface of a whole wafer of RFID chips (300 μm × 300 μm) with a blue film and arranged in close contact. The coating thickness was 19 μm, and the film was expanded to create gaps between adjacent RFID chips. The spacing between adjacent chips was 60-70 μm, thus obtaining a spaced chip assembly.

[0062] A conductor layer (specifically, an Al film on a PET carrier, 50 μm thick) is laminated on the surface of the conductive medium of the spacer chip assembly, with one side of the Al film in contact with the conductive medium, and then subjected to a hot pressing treatment. The hot pressing treatment conditions are a top and bottom temperature of 185°C, a time of 8 seconds, and a pressure of 1.2N, so that the conductive medium solidifies and bonds the RFID chip to the conductor layer.

[0063] Laser is used to cut the conductor layer between the two pads of the RFID chip, and then the conductor layer is divided along the center line between adjacent chips to form independent improved RFID chips. Each improved RFID chip carries two conductor layers.

[0064] The two conductor layers in each improved RFID chip are used as binding links for packaging. The packaging equipment used is Mühlbauer DDA, which greatly improves the packaging efficiency.

[0065] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A packaging method for an RFID chip, characterized in that: The following steps are involved: A conductive medium is applied to the surface of a whole wafer of RFID chips arranged in close contact with a transfer film, and then the film is expanded to create gaps between adjacent RFID chips to obtain a spacer chip assembly; the conductive medium is an anisotropic conductive adhesive, which ensures that the conductive medium conducts electricity in the vertical direction but does not conduct electricity in the horizontal direction; A conductor layer is attached to the surface of the conductive medium of the spacer chip assembly, and a heat pressing process is performed to solidify the conductive medium and combine the RFID chip and the conductor layer; the area of ​​the conductor layer is greater than or equal to the area of ​​the transfer film after film expansion; Use machine vision to cut the conductor layer between the two pads of the RFID chip, and then use machine vision to split the conductor layer along the gap between adjacent chips to form independent improved RFID chips. Each improved RFID chip carries two conductor layers. The two conductor layers in each improved RFID chip are used as binding connection points for packaging; the packaging is connected to the empty antenna; The spacing distance between adjacent RFID chips in the spacer chip assembly is 50 to 100 μm; The thickness of the conductor layer is 50 to 80 μm; The method of dividing the conductor layer along the gaps between adjacent chips includes dividing the conductor layer using fixed horizontal and vertical paths.

2. The packaging method according to claim 1, wherein: The size of the RFID chip is (100-300) μm×(100-300) μm.

3. The packaging method according to claim 1, wherein: The conductor layer includes metal foil or multi-layer composite conductive material.

4. The packaging method according to claim 1, wherein: The method of cutting off the conductor layer between the two pads of the RFID chip includes: laser cutting or etching.

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