Process method for taking out and recycling chip in flip chip packaging structure

Abstract

The invention provides a process method for taking out and recycling chips in flip chip packaging structures, which comprises the following steps of: (1) coating a stripping layer on a carrier, and mounting a plurality of flip chip packaging structures on the stripping layer in the direction that solder balls face upwards; (2) carrying out plastic packaging on all flip chip packaging structures on the stripping layer; (3) grinding or cutting the repackaging structure from top to bottom; and (4) stripping the re-packaging structure from the carrier, cutting the re-packaging structure into single packaging units, and wrapping a single chip in each packaging unit. According to the invention, the integrity of the chip and the exposure of welding spots are ensured through the processes of plastic packaging again, grinding or cutting, stripping and cutting, and the chip is protected by using the residual plastic packaging material, so that the waste of the material is reduced, and the yield is improved; harmful waste liquid generated by acid pickling and harmful gas generated by laser are avoided, and the device is more environmentally friendly and safer; and the process is simple and suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor packaging, and in particular to a process method for taking out and reusing a chip in a flip chip packaging structure. Background Art

[0002] Nowadays, flip chip packaging structure (FCCSP) is widely used in the semiconductor industry. Flip chip packaging is to form electrical interconnection between the chip die and the substrate through the connection method of area array solder joints. Its process mainly includes patch, underfill filling, epoxy molding, etc. The chip is the core component of the flip chip packaging structure. How to remove and reuse the chip of the FCCSP product that has been mounted on SMT (surface mount technology) has become the focus of the industry.

[0003] At present, the removal of chips mainly relies on two methods: pickling and laser. The epoxy plastic seal on the upper surface of the chip can be removed by pickling and laser, and the bottom filling glue on the lower surface of the chip can only be removed by pickling. However, both methods will cause irreversible damage to the chip and the solder joints on the chip; and the process parameters of pickling and laser are difficult to control accurately, which can easily lead to excessive removal or incomplete removal, affecting the yield, resulting in high chip removal costs, and also environmental and safety risks.

[0004] Therefore, how to optimize the chip removal and recycling process in FCCSP, ensure that the chips are not damaged during the stripping and recycling process, and increase the chip reuse rate has become an urgent problem to be solved in the industry. Summary of the invention

[0005] In view of the shortcomings of the prior art mentioned above, the purpose of the present invention is to provide a process method for removing and reusing chips in a flip chip packaging structure, so as to solve the problem that the packaging structure in the prior art can only rely on acid pickling and laser to remove other parts outside the chip, which can easily damage the chip, and has high cost and low yield.

[0006] To achieve the above-mentioned and other related purposes, the present invention provides a process for taking out and reusing a chip in a flip chip packaging structure, comprising the following steps: (1) Coat a peeling layer on the carrier, and mount several flip-chip packaging structures on the peeling layer with the solder balls facing upward, such as Figure 1 As shown, the flip chip packaging structure includes a substrate, a chip, a first plastic sealing layer and solder balls. The chip is flipped on the back of the substrate, bottom filling glue is filled between the chip and the substrate, the first plastic sealing layer covers the chip, and the solder balls are arranged on the front of the substrate; (2) performing plastic encapsulation on all flip chip packaging structures on the peeling layer to obtain a re-encapsulated structure; (3) Grinding or cutting the repackaged structure from top to bottom to remove the solder balls, substrate and bottom filler in the flip chip package structure until the solder joints of the chip are exposed; (4) The repackaged structure is peeled off from the carrier and then cut into individual package units, each of which contains a single chip.

[0007] The present invention ensures the integrity of the chip and the exposure of the solder joints through re-molding, grinding (or cutting) and stripping processes, and uses the residual plastic packaging material to protect the chip, thereby reducing material waste and improving the yield rate; it avoids harmful waste liquid generated by pickling and harmful gases generated by lasers, and is more environmentally friendly and safe; and the process is simple and suitable for large-scale production.

[0008] In one embodiment of the present invention, in step (1), a plurality of flip chip packaging structures are rearranged in an array on a peeling layer, so that a plurality of packaging structures can be mounted at one time and a plurality of chips can be processed and removed at the same time, thereby effectively improving the efficiency of chip removal.

[0009] In one embodiment of the present invention, in order to ensure that each packaging structure maintains a consistent horizontal height on the peeling layer, ensure synchronous removal during the grinding (or cutting) process, and avoid the problem of excessive removal or incomplete removal, the present invention adjusts the peeling layer formula, and the peeling layer includes the following components in parts by weight: 60-70 parts of silicone resin, 10-15 parts of nano-silica filler, 10-15 parts of organic solvent, 2-3 parts of silicone modifier, 1-2 parts of silane coupling agent, and 1-2 parts of silicone leveling agent.

[0010] Among them, nano-silica fillers can play a certain supporting and filling role. Together with the silicone leveling agent, the peeling layer material can be evenly distributed during the coating process to form a flat surface, so that the packaging structure mounted on the peeling layer can maintain a consistent level height, and improve the synchronization and accuracy during grinding (or cutting). At the same time, nano-silica fillers can improve the mechanical strength and thermal stability of the peeling layer, and can improve the high temperature resistance of the peeling layer material, ensuring that the release layer can withstand the high temperature during the re-packaging process and is not prone to warping or deformation.

[0011] Further, the organic solvent includes at least one of xylene, toluene, acetone, and ethyl acetate; The organosilicon modifier includes at least one of polydimethylsiloxane modifier, organosilicon acrylate and organosilicon epoxy resin; The organic silicon leveling agent includes at least one of polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane and fluorine-modified organic silicon leveling agent.

[0012] In one embodiment of the present invention, in step (2), all flip chip packaging structures on the peeling layer are re-molded with a molding material to form a second molding layer.

[0013] Furthermore, the second plastic encapsulation layer completely covers the flip chip packaging structure, or exposes all or part of the solder balls of the flip chip packaging structure. The solder balls of the recycled flip chip packaging structure are usually damaged, and the second plastic encapsulation layer does not need to completely cover the solder balls, which further simplifies the grinding or cutting operation and saves processing time; when all solder balls are completely covered, the flatness and structural strength of the re-packaged structure can be guaranteed, and the flip chip packaging structure can be prevented from deformation or displacement during the grinding or cutting process.

[0014] Furthermore, firstly, in order to avoid the molding material from filling incompletely every corner during the secondary plastic encapsulation process, bubbles are generated to affect the integrity of the second plastic encapsulation layer; secondly, in order to avoid the molding material from shrinking and generating internal stress during the plastic encapsulation process, causing the flip chip packaging structure to warp or shift in position, affecting the accuracy of subsequent grinding (or cutting), the present invention further improves the formula of the molding material. The molding material includes the following components in parts by weight: 30-40 parts of bisphenol F epoxy resin, 10-15 parts of curing agent, 40-50 parts of spherical or flaky fillers, 1-2 parts of silane coupling agent, 3-5 parts of toughening agent, 2-3 parts of organosilicon-modified epoxy resin, 1-2 parts of active diluent, 0.5-1 parts of defoaming agent, 0.5-1 parts of degassing agent, and 0.5-1 parts of rheological agent.

[0015] Further, the spherical filler includes at least one of a spherical silica filler and a spherical alumina filler; the flake filler includes a flake boron nitride filler; The curing agent includes methyl hexahydrophthalic anhydride curing agent; The toughening agent includes acrylic rubber or polyethersulfone toughening agent; The defoamer comprises an organosilicon defoamer; The degassing agent includes a high molecular weight polysiloxane degassing agent.

[0016] The present invention selects bisphenol F epoxy resin with low shrinkage rate and combines it with inorganic filler with high filling amount, so as to significantly reduce the shrinkage rate of molding material and reduce the risk of chip deviation or warping during the curing process of molding material; preferably, spherical and flaky compound fillers are used. On the one hand, compounding of the two can improve the filling density, reduce the shrinkage rate of the molding material matrix, reduce internal stress, and ensure the dimensional stability of the second plastic sealing layer; on the other hand, the spherical filler has good fluidity and the flaky filler has poor fluidity. Compounding of the two can balance the fluidity of the material and regulate various anisotropies. When the number of flip chip packaging structures arranged is large and dense, the proportion of spherical fillers is increased, and when the flip chip packaging structures are sparsely arranged, the proportion of spherical fillers can be appropriately reduced.

[0017] Among them, the rheological agent can improve the fluidity of the material, ensure the filling of every corner, and reduce the generation of bubbles; the defoaming agent promotes the bursting of bubbles and the degassing agent helps the bubbles escape before the material solidifies, effectively reducing the bubbles in the molding material and improving the quality and reliability of the second plastic sealing layer.

[0018] In one embodiment of the present invention, the transparency of the second plastic encapsulation layer is higher than the transparency of the first plastic encapsulation layer; in step (4), an optical alignment system and / or an automatic visual inspection system is used to identify the individual packaging units before cutting, so as to ensure high precision and chip integrity during the cutting process.

[0019] As described above, the process method for taking out and reusing the chip in the flip chip packaging structure of the present invention has the following beneficial effects: 1. The present invention ensures the integrity of the chip and the exposure of the solder joints through re-plastic packaging, grinding or cutting, peeling and cutting processes, and uses the residual plastic packaging material to protect the chip, thereby reducing material waste and improving the yield; avoiding harmful waste liquid generated by pickling and harmful gases generated by laser, being more environmentally friendly and safe; and having a simple process, suitable for large-scale production.

[0020] 2. The present invention improves the peeling layer formula. The nano-silica filler can improve the mechanical strength and thermal stability of the peeling layer while maintaining its flatness, so that the packaging structure mounted on the peeling layer can maintain a consistent horizontal height, improve the accuracy during grinding or cutting, ensure the integrity of the removed chip, and improve the yield.

[0021] 3. The present invention improves the formulation of the molding material, selects low-shrinkage epoxy resin, and combines it with a high-filling amount of inorganic filler to significantly reduce the shrinkage of the molding material and reduce the risk of chip deviation or warping during the curing process of the molding material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the flip chip packaging structure in Example 1 of the present invention.

[0023] Figure 2 This is a schematic diagram of the structure of step S1 in Example 1 of the present invention.

[0024] Figure 3 This is a schematic diagram of the structure of step S2 in Example 1 of the present invention.

[0025] Figure 4 This is a schematic diagram of the structure of step S3 in Example 1 of the present invention.

[0026] Figure 5 This is a schematic diagram of the structure of step S4 in Example 1 of the present invention.

[0027] Figure 6 This is a schematic diagram of the structure of step S5 in Example 1 of the present invention.

[0028] Figure 7 This is a schematic diagram of the structure of step S6 in Example 1 of the present invention.

[0029] Component number description 100, carrier; 200, peeling layer; 300, flip chip packaging structure; 301, first plastic packaging layer; 302, chip; 303, solder joint; 304, substrate; 305, solder ball; 400, repackaging structure; 401, second plastic packaging layer. DETAILED DESCRIPTION

[0030] The following specific embodiments illustrate the implementation of the present invention, and those familiar with the technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0031] Example 1 This embodiment provides a process for taking out and reusing a chip in a flip chip packaging structure, referring to Figure 1 The flip chip packaging structure 300 includes a substrate 304, a chip 302, a first plastic packaging layer 301 and solder balls 305. The chip 302 is flipped on the back of the substrate 304. The solder joints 303 on the chip are electrically connected to the rewiring layer in the substrate. The chip and the substrate are filled with bottom filling glue. The first plastic packaging layer covers the chip and the bottom filling glue from the back of the substrate. The solder balls 305 are arranged on the front of the substrate and are electrically connected to the rewiring layer. The specific steps include: S1. References Figure 2 , coating a release layer 200 on the carrier 100; S2. Reference Figure 3 , multiple Figure 1 The flip chip package structure 300 is shown mounted on the peeling layer 200 in an array arrangement with the solder balls 305 facing upward; S3. Reference Figure 4 , using a molding material to plastic-encapsulate all flip-chip packaging structures on the peeling layer to form a second plastic-encapsulation layer 401, the second plastic-encapsulation layer completely covers all solder balls, and the entire structure after plastic-encapsulation is a re-encapsulation structure 400; S4. References Figure 5 , grinding the repackaging structure 400 from top to bottom, removing the solder balls, substrate and bottom filling glue in the flip chip packaging structure 300, until the solder joints of the chip are exposed; S5. Reference Figure 6, peeling the repackage structure 400 from the carrier 100; S6. Reference Figure 7 The repackaged structure is cut into individual package units, each package unit contains a single chip 302, and there are a first plastic package layer 301 and a second plastic package layer 401 outside the package unit, and the two layers of plastic package can protect the chip.

[0032] Example 2 This embodiment provides a process method for taking out and reusing a chip in a flip chip packaging structure. Compared with the embodiment 1, the only difference is that: The molding material includes the following components in parts by weight: 35 parts of bisphenol F epoxy resin, 10 parts of curing agent, 30 parts of spherical silica filler, 10 parts of boron nitride filler in sheets, 2 parts of silane coupling agent, 3 parts of acrylic rubber, 3 parts of organosilicon-modified epoxy resin, 1 part of reactive diluent, 1 part of organosilicon defoaming agent, 1 part of high molecular weight polysiloxane degassing agent, and 0.5 parts of rheological agent.

[0033] In step S3, the molding materials are mixed evenly and then slowly added into the mold to plastic-encapsulate all flip-chip packaging structures. They are first cured at 80-100° C. and then heated to 150-180° C. for complete curing.

[0034] Example 3 This embodiment provides a process method for taking out and reusing a chip in a flip chip packaging structure. Compared with Embodiment 2, the only difference is that: The molding material includes the following components in parts by weight: 35 parts of bisphenol F epoxy resin, 10 parts of curing agent, 40 parts of spherical silica filler, 2 parts of silane coupling agent, 5 parts of polyethersulfone toughening agent, 3 parts of silicone modified epoxy resin, 1 part of active diluent, 1 part of silicone defoaming agent, 1 part of high molecular weight polysiloxane degassing agent, and 0.5 part of rheological agent.

[0035] Example 4 This embodiment provides a process method for taking out and reusing a chip in a flip chip packaging structure. Compared with the embodiment 1, the only difference is that: The material formula of the peeling layer includes the following components in parts by weight: 65 parts of silicone resin, 12 parts of nano-silica filler, 10 parts of xylene, 3 parts of polydimethylsiloxane modifier, 2 parts of silane coupling agent, and 2 parts of polyether-modified polydimethylsiloxane.

[0036] In step S1, after the above-mentioned peeling layer materials are mixed evenly, they are evenly coated on the carrier by spin coating, blade coating or spray coating to ensure that the thickness is uniform, and then cured at 120-150°C.

[0037] In step S2, after the flip chip packaging structure 300 is mounted on the peeling layer 200 in an array arrangement with the solder balls 305 facing upward, the entire peeling layer 200 is blown vertically from top to bottom, thereby applying a slight pressure on the packaging structure 300 to ensure uniform contact between it and the peeling layer to avoid warping or tilting.

[0038] In summary, the present invention ensures the integrity of the chip and the exposure of the solder joints through re-plastic sealing, grinding or cutting and stripping processes, and uses the residual plastic sealing material to protect the chip, reducing material waste and improving the yield rate; avoiding harmful waste liquid generated by pickling and harmful gases generated by laser, being more environmentally friendly and safe; and the process is simple and suitable for large-scale production. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0039] Among them, the terms such as "upper", "lower", "left", "right", "front", "back", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0040] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. All equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A process for taking out and reusing a chip in a flip chip packaging structure, characterized in that: The following steps are involved: (1) coating a peeling layer on the carrier, and mounting a plurality of flip chip packaging structures on the peeling layer with the solder balls facing upward; (2) performing plastic encapsulation on all flip chip packaging structures on the peeling layer to obtain a re-encapsulated structure; (3) Grinding or cutting the repackage structure from top to bottom until the solder joints of the chip are exposed; (4) Peeling the repackaged structure off the carrier and cutting it into individual package units, each of which contains a single chip.

2. The process according to claim 1, characterized in that: The flip chip packaging structure includes a substrate, a chip, a first plastic packaging layer and solder balls. The chip is flipped on the back side of the substrate, bottom filling glue is filled between the chip and the substrate, the first plastic packaging layer covers the chip, and the solder balls are arranged on the front side of the substrate.

3. The process according to claim 1, characterized in that: In step (1), a plurality of flip chip packaging structures are rearranged on a peeling layer in the form of an array.

4. The process according to claim 1, characterized in that: In step (1), the release layer comprises the following components in parts by weight: 60-70 parts of organic silicone resin, 10-15 parts of nano-silica filler, 10-15 parts of organic solvent, 2-3 parts of organic silicone modifier, 1-2 parts of silane coupling agent, and 1-2 parts of organic silicone leveling agent.

5. The process according to claim 4, characterized in that: The organic solvent includes at least one of xylene, toluene, acetone, and ethyl acetate; the organosilicon modifier includes at least one of polydimethylsiloxane modifier, silicone acrylate, and silicone epoxy resin; the organosilicon leveling agent includes at least one of polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, and fluorine-modified organosilicon leveling agent.

6. The process according to claim 2, characterized in that: In step (2), all flip chip packaging structures on the peeling layer are re-molded with molding material to form a second molding layer.

7. The process according to claim 6, characterized in that: The second plastic packaging layer completely covers the flip chip packaging structure, or exposes all or part of the solder balls of the flip chip packaging structure.

8. The process according to claim 6, characterized in that: The molding material comprises the following components in parts by weight: 30-40 parts of bisphenol F epoxy resin, 10-15 parts of curing agent, 40-50 parts of spherical or flaky fillers, 1-2 parts of silane coupling agent, 3-5 parts of toughening agent, 2-3 parts of organosilicon-modified epoxy resin, 1-2 parts of active diluent, 0.5-1 part of defoaming agent, 0.5-1 part of deaerator and 0.5-1 part of rheological agent.

9. The process according to claim 8, characterized in that: The spherical filler includes at least one of a spherical silica filler and a spherical alumina filler; the flaky filler includes a flaky boron nitride filler; the curing agent includes a methyl hexahydrophthalic anhydride curing agent; the toughening agent includes an acrylic rubber or a polyethersulfone toughening agent; the defoaming agent includes a silicone defoaming agent; and the degassing agent includes a high molecular weight polysiloxane degassing agent.

10. The process according to claim 6, characterized in that: The transparency of the second plastic encapsulation layer is higher than that of the first plastic encapsulation layer. In step (4), an optical alignment system and / or an automatic visual inspection system are used to identify the individual packaging units and then cut them.

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