Packaging method of RFID chip

Abstract

The invention relates to the technical field of chip packaging, in particular to a packaging method of an RFID chip. According to the invention, the conductor layer is combined on the bonding pad of the RFID chip, so that the packaging size of the RFID chip is larger than the physical size of the RFID chip, i.e., the RFID chip with an ultra-small size is changed into the RFID chip with a conventional size or even a larger size, thereby reducing the packaging difficulty, getting rid of the dependence on high-precision expensive equipment, and improving the packaging efficiency. The equipment purchase cost, depreciation cost and consumable cost do not need to be increased, and meanwhile, the packaging speed and the labor efficiency are remarkably 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 pad by visual precision positioning (such as Figure 2 As shown). The newer DDA (Direct Die Attach) technology uses a pin to lift the chip directly from the back of the blue film, allowing the chip to protrude and bond to the antenna while peeling off the film. Although this improves the efficiency, it is still a one-by-one method, and the high positioning accuracy requirements have not changed.

[0003] With the continuous advancement of RFID chip technology, the chip size is becoming smaller and smaller. Currently, the smallest chip size in the industry has reached about 0.26mm×0.26mm, which puts higher requirements on the positioning accuracy of the package and also makes the price of related equipment continue to rise.

[0004] Whether using suction or DDA, existing packaging equipment generally relies on a serial pipeline operation mode to pick and package a single chip. This method has become a major challenge in the face of the current situation where a single wafer can hold 600,000 to 800,000 chips. Even the fastest packaging machine in the industry has a theoretical speed of only 100k / h, and it still takes about 6 hours to complete the packaging of a wafer.

[0005] Although the continued effect of Moore's Law has reduced chip size and the manufacturing cost of a single chip, it is accompanied by higher-cost packaging equipment and higher-precision antenna processing technology, which to some extent offsets the savings in chip manufacturing costs. Faced with the logistics industry's demand for hundreds of billions of tags, the current packaging speed is obviously difficult to meet actual application requirements. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a packaging method for RFID chips. The packaging method provided by the present invention gets rid of the dependence on higher precision equipment, does not need to 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: The present invention provides a packaging method for an RFID chip, comprising the following steps: After coating the surface of the RFID chips of the whole wafer with the transfer film and arranged in close contact with each other with a conductive medium, the film is expanded to generate gaps between adjacent RFID chips, thereby obtaining a spacer chip assembly; 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 with the conductor layer; 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; The two conductor layers in each improved RFID chip are used as binding link points for packaging.

[0008] Preferably, the spacing distance between adjacent RFID chips in the spacing chip assembly is 50-100 μm.

[0009] Preferably, the conductive medium includes solder paste or anisotropic conductive adhesive.

[0010] Preferably, the size of the RFID chip is (100-300) μm×(100-300) μm.

[0011] Preferably, the conductor layer has a thickness of 50-80 μm.

[0012] Preferably, the conductor layer comprises metal foil or a multi-layer composite conductive material.

[0013] Preferably, the method of cutting off the conductor layer between the two pads of the RFID chip includes: laser cutting or etching.

[0014] Preferably, dividing the conductor layer along the gaps between adjacent chips includes dividing the conductor layer along fixed horizontal and vertical paths or along a center line between the gaps between adjacent chips.

[0015] Preferably, the coating thickness of the conductive medium is 10-50 μm.

[0016] The present invention provides a packaging method for an RFID chip. By combining a conductor layer on a pad of the RFID chip, the obtained improved RFID chip is packaged so that the packaging size of the RFID chip is larger than the physical size of the RFID chip, that is, the ultra-small RFID chip is converted into a regular-sized RFID chip or even a larger-sized RFID chip, thereby reducing the packaging difficulty, getting rid of the dependence on high-precision and expensive equipment, and there is no need to increase equipment procurement costs, depreciation costs and consumables costs.

[0017] At present, the packaging of RFID chips in the industry is done one by one. When packaging one by one, the size of RFID chips is getting smaller and smaller, and the precision requirements for chip retrieval are getting higher and higher, resulting in low packaging efficiency. The present invention significantly improves the packaging speed by converting ultra-small chips into regular or even larger chips. Compared with the existing serial pipeline operation mode, it greatly shortens the wafer packaging time and can better meet the needs of large-scale tags.

[0018] The present invention uses an innovative packaging method to enable ordinary RFID packaging equipment and even a compound machine to be used for ultra-small chip packaging, providing strong support for large-scale applications in the RFID industry.

[0019] The present invention reduces the difficulty of packaging operation and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural diagram of an RFID chip; Figure 2 A schematic diagram showing the placement of an RFID chip at an empty antenna pad; Figure 3 The schematic diagram is a structural diagram of a whole wafer with a transfer film and arranged in close contact, wherein a is a top view, and b is a cross-sectional view cut along the diameter of the wafer; Figure 4 Schematic diagram of the structure of the spacer chip assembly, wherein a is a top view, and b is a cross-sectional view along the diameter of the wafer; Figure 5 Schematic diagram of attaching a conductor layer to the surface of a conductive medium of a spacer chip assembly, wherein a is a top view, and b is a cross-sectional view cut along the diameter of the wafer; Figure 6 Schematic diagram of cutting the conductor layer between the two pads of the RFID chip, where a is a top view and b is a cross-sectional view after cutting; Figure 7 is a schematic diagram of dividing the conductor layer along the gap between adjacent chips, wherein a is a top view and b is a cross-sectional view; Figure 8 A schematic diagram of dividing a conductor layer using fixed horizontal and vertical paths; Fig. 9 A schematic diagram of dividing the conductor layer along the center line between the gaps between adjacent chips; Fig.10 Schematic diagram of improved RFID chip packaging, where a is a top view and b is a cross-sectional view. DETAILED DESCRIPTION

[0021] The present invention provides a packaging method for an RFID chip, comprising the following steps: After coating the surface of the RFID chips of the whole wafer with the transfer film and arranged in close contact with each other with a conductive medium, the film is expanded to generate gaps between adjacent RFID chips, thereby obtaining a spacer chip assembly; 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 with the conductor layer; 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; The two conductor layers in each improved RFID chip are used as binding link points for packaging.

[0022] The present invention coats a conductive medium on the surface of an RFID chip of a whole wafer with a transfer film and arranged in close contact, and then expands the film to generate gaps between adjacent RFID chips to obtain a spacer chip assembly.

[0023] In the present invention, the structural schematic diagram of the whole wafer with the transfer film and arranged in close contact is as follows: Figure 3 As shown, each RFID chip is arranged in a close and regular pattern in the wafer. In the present invention, the transfer film is preferably a blue film or a UV film.

[0024] The present invention has no special requirements for the RFID chip, and any RFID chip known in the art can be used. In the present invention, the RFID chip has two pads, and the connection with the empty antenna is achieved through the pads. In the present invention, the size of the RFID chip is preferably (100~300)μm×(100~300)μm, and in specific embodiments it can be 100μm×100μm, 150μm×150μm, 200μm×200μm, 260μm×260μm or 300μm×300μm.

[0025] In the present invention, the conductive medium preferably includes solder paste or anisotropic conductive adhesive; the present invention uses anisotropic conductive adhesive to ensure that the conductive medium conducts electricity in the vertical direction but does not conduct electricity in the horizontal direction. In the present invention, the coating thickness of the conductive medium is preferably 10 to 50 μm, and in a specific embodiment it can be 10 μm, 20 μm, 30 μm, 40 μm or 50 μm. In the present invention, the coating area of ​​the conductive medium is sufficient to cover all RFID chips.

[0026] The present invention has no special requirements for the specific implementation of the film expansion, and the film expansion method 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 4In the present invention, the spacing distance between adjacent RFID chips in the spacing chip assembly is preferably 50-100 μm, and in a specific embodiment can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm.

[0027] 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 with the conductor layer.

[0028] In the present invention, the conductor layer preferably includes a metal foil or a multilayer composite conductive material. The present invention does not specifically limit the specific composition of the conductor layer, and any conductive material can be used. In an embodiment of the present invention, it is specifically an Al film of a PET (polyethylene terephthalate) carrier. In the present invention, the thickness of the conductor layer is preferably 50 to 80 μm, and in a specific embodiment it can be 50 μm, 60 μm, 70 μm or 80 μm. The present invention can achieve a firm combination with the RFID chip and the empty antenna by controlling the thickness of the conductor layer within the above range.

[0029] In the present invention, the area of ​​the conductor layer is preferably ≥ the area of ​​the transfer film after film expansion. This is because the film expansion may not be ideal, and there may be uneven chips. The present invention first uses a large-area conductor layer to allow all RFID chips to fit as a whole without considering the accuracy, and then uses machine vision to cut and segment the conductor layer according to the deviation of each chip to improve packaging efficiency.

[0030] The present invention does not specifically limit the conditions of the hot pressing treatment, as long as the conductive medium can be solidified and the RFID chip and the conductor layer can be firmly combined. In this field, the general hot pressing treatment conditions are preferably: hot pressing temperature of 160-190°C, pressure of 1-2N, and time of 6-10s.

[0031] 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 as shown).

[0032] The present invention preferably uses laser cutting or etching to cut off the conductor layer between the two pads of the RFID chip. The purpose of the present invention to cut off the conductor layer between the two pads of the RFID chip is to eliminate the short circuit. The present invention has no special requirements for the specific implementation conditions of the laser cutting and etching methods, and only the conductor layer is cut without damaging the height of the chip itself. For example, the etching method can achieve the purpose of cutting off the conductor layer between the two pads of the RFID chip by applying photoresist or photosensitive ink and optical scanning exposure. In the present invention, the etching method has lower cost and higher precision.

[0033] When cutting, the present invention preferably uses machine vision and / or laser to cut the conductor layer between the two pads of the chip according to the deviation of each chip. Because the arrangement error is generally regular and the difference is not too large, the laser basically cuts along a relatively straight path, and the cutting efficiency is higher than that of a completely random arrangement.

[0034] 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 of which carries two conductor layers (such as Figure 7 as shown).

[0035] The present invention preferably uses a fixed horizontal and vertical path or a center line between adjacent chip gaps to segment the conductor layer. In the present invention, the segmentation method is the same as the above-mentioned cutting method, and will not be repeated here. When the present invention uses a fixed horizontal and vertical path for segmentation, the chip position deviation will not be too large, and the use of a 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 in Figure 2). Fig. 9 as shown).

[0036] In the present invention, the size of the improved RFID chip is larger than that of the RFID chip. As a preferred solution, the size of the improved RFID chip is preferably 50-100 μm larger than that of the RFID chip, that is, the side length of the improved RFID chip is 50-100 μm larger than that of the RFID chip. In a specific embodiment, the size of the improved RFID chip can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm larger than that of the RFID chip.

[0037] In the present invention, the improved RFID chip is still adhered to the flexible transfer film, and the present invention packages it directly or packages it after weaving it.

[0038] During packaging, the present invention uses two conductor layers in each improved RFID chip as binding connection points for packaging (such as Fig.10 as shown).

[0039] 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.

[0040] The improved RFID chip and the packaging method of the RFID chip provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0041] Example 1 A packaging method for an RFID chip, the steps are as follows: Solder paste is applied on the surface of the whole wafer RFID chips (size of 300μm×300μm) with blue film and arranged in close contact, with the coating thickness of 19μm, and the film is expanded to form gaps between adjacent RFID chips, with the interval between adjacent chips being 60-70μm, to obtain a spaced chip assembly; A conductor layer (specifically, an Al film of a PET carrier with a thickness of 50 μm) is attached to the surface of the conductive medium of the spacer chip assembly, and one side of the Al film is in contact with the conductive medium, and a hot pressing treatment is performed. The hot pressing treatment conditions are upper and lower temperatures of 185°C, a time of 8s, and a pressure of 1.2N, so that the conductive medium solidifies and combines the RFID chip with the conductor layer; The conductor layer between the two pads of the RFID chip is cut by laser, and then the conductor layer is divided along the center line between adjacent chips to form an independent improved RFID chip, each of which carries two conductor layers; 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.

[0042] 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 principle of the present invention. These improvements and modifications should also be regarded as 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: After coating the surface of the RFID chips of the whole wafer with the transfer film and arranged in close contact with each other with a conductive medium, the film is expanded to generate gaps between adjacent RFID chips, thereby obtaining a spacer chip assembly; 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 with the conductor layer; 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; The two conductor layers in each improved RFID chip are used as binding link points for packaging.

2. The packaging method according to claim 1, characterized in that: The spacing distance between adjacent RFID chips in the spacing chip assembly is 50-100 μm.

3. The packaging method according to claim 1, characterized in that: The conductive medium includes solder paste or anisotropic conductive adhesive.

4. The packaging method according to claim 1, characterized in that: The size of the RFID chip is (100-300) μm×(100-300) μm.

5. The packaging method according to claim 1, characterized in that: The conductor layer has a thickness of 50-80 μm.

6. The packaging method according to claim 1 or 5, characterized in that: The conductor layer includes metal foil or multi-layer composite conductive material.

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

8. The packaging method according to claim 1, characterized in that: The method of dividing the conductor layer along the gaps between adjacent chips includes dividing the conductor layer using fixed horizontal and vertical paths or along the center line between the gaps between adjacent chips.

9. The packaging method according to claim 1 or 3, characterized in that: The coating thickness of the conductive medium is 10-50 μm.

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