Process method for chip extraction and reuse in flip-chip packaging structure

Abstract

The present invention provides a process method for chip removal and reuse in a flip-chip packaging structure, comprising: (1) coating a release layer on a carrier, and mounting a plurality of flip-chip packaging structures on the release layer with the solder balls facing upward; (2) encapsulating all the flip-chip packaging structures on the release layer; (3) grinding or cutting the re-encapsulated structure from top to bottom; (4) peeling the re-encapsulated structure from the carrier and cutting it into individual packaging units, each of which contains a single chip. By means of the processes of re-encapsulation, grinding or cutting, peeling and cutting, the present invention ensures the integrity of the chip and the exposure of the solder joints, protects the chip with the remaining encapsulation material, reduces material waste and improves the yield; avoids the harmful waste liquid generated by pickling and the harmful gas generated by laser, and is more environmentally friendly and safe; and has a simple process and is suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor packaging, and particularly to a process method for chip removal and reuse in a flip-chip packaging structure. Background Art

[0002] Nowadays, flip-chip chip scale package (FCCSP) structures are widely used in the semiconductor industry. Flip-chip packaging forms electrical interconnections between a chip die and a substrate through an array of solder joints. Its process flow mainly includes chip mounting, underfill (bottom fill adhesive) filling, epoxy encapsulation, etc. As the core component of the flip-chip packaging structure, how to re-remove and reuse the chips of FCCSP products that have been processed by SMT (Surface Mount Technology) has become the focus of attention in the industry.

[0003] Currently, the removal of chips mainly relies on two methods: pickling and laser. The epoxy encapsulation on the upper surface of the chip can be removed by pickling and laser, and the underfill on the lower surface of the chip can only be removed by pickling. However, both of these methods will cause irreversible damage to the chip and the solder joints on the chip; moreover, the process parameters of pickling and laser are difficult to accurately control, which easily leads to over-removal or incomplete removal, affecting the yield rate, resulting in a high cost for chip removal, and there are also environmental protection and safety risks.

[0004] Therefore, how to optimize the chip removal and recycling process in FCCSP, ensure that the chip is not damaged during the peeling and recycling process, and improve the chip reuse rate has become an urgent problem to be solved in the industry. Summary of the Invention

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

[0006] To achieve the above purpose and other related purposes, the present invention provides a process method for removing and reusing chips in a flip-chip packaging structure, including the following steps:

[0007] (1) Coat a release layer on a carrier, and mount a plurality of flip-chip packaging structures on the release layer with the solder balls facing upward, as Figure 1 shown. The flip-chip packaging structure includes a substrate, a chip, a first encapsulation layer, and solder balls. The chip is flip-mounted on the back of the substrate. An underfill is filled between the chip and the substrate. The first encapsulation layer covers the chip. The solder balls are arranged on the front of the substrate;

[0008] (2) Encapsulate all the flip-chip package structures on the release layer to obtain a re-packaged structure;

[0009] (3) Grind or cut the re-packaged structure from top to bottom to remove the solder balls, substrates, and underfill in the flip-chip package structure until the solder joints of the chips are exposed;

[0010] (4) Peel the re-packaged structure from the carrier, and then cut it into individual package units, each of which contains a single chip.

[0011] Through the processes of re-encapsulation, grinding (or cutting), and peeling, the present invention ensures the integrity of the chips and the exposure of the solder joints, protects the chips with the remaining encapsulation material, reduces material waste, and improves the yield rate; avoids the harmful waste liquid generated by pickling and the harmful gases generated by lasers, and is more environmentally friendly and safe; and the process is simple and suitable for large-scale production.

[0012] In an embodiment of the present invention, in step (1), multiple flip-chip package structures are re-arranged on the release layer in an array form, and multiple package structures can be mounted at one time, and multiple chips can be processed and taken out simultaneously, effectively improving the efficiency of chip extraction.

[0013] In an embodiment of the present invention, to ensure that each package structure maintains a consistent horizontal height on the release layer and to avoid the problems of over-removal or incomplete removal during grinding (or cutting), the present invention adjusts the formula of the release layer. The release 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.

[0014] Among them, the nano-silica filler can play a certain role in support and filling. Cooperating with the silicone leveling agent, the release layer material is evenly distributed during the coating process to form a flat surface, so that the package structures mounted on the release layer can maintain a consistent horizontal height, improving the synchronism and accuracy during grinding (or cutting). At the same time, the nano-silica filler can improve the mechanical strength and thermal stability of the release layer, can improve the high-temperature resistance of the release layer material, and ensure that the release layer can withstand the high temperature during the re-encapsulation process and is not prone to warping and deformation.

[0015] Further, the organic solvent includes at least one of xylene, toluene, acetone, and ethyl acetate;

[0016] The silicone modifier includes at least one of polydimethylsiloxane modifier, silicone acrylate, and silicone epoxy resin;

[0017] The silicone leveling agent includes at least one of polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, and fluorine-modified silicone leveling agent.

[0018] In one embodiment of the present invention, in step (2), all flip-chip package structures on the release layer are reshaped with a molding material to form a second encapsulation layer.

[0019] Furthermore, the second encapsulation layer completely covers the flip-chip package structure, or exposes all or part of the solder balls of the flip-chip package structure. The solder balls of the recycled flip-chip package structure are usually damaged, and the second encapsulation layer does not have to completely cover the solder balls, further simplifying the grinding or cutting operation and saving processing time; when completely covering all solder balls, the flatness and structural strength of the repackaged structure can be guaranteed, and the flip-chip package structure can be prevented from deforming or displacing during the grinding or cutting process.

[0020] Furthermore, one is to avoid incomplete filling of the molding material in each corner during the secondary encapsulation process, generating bubbles and affecting the integrity of the second encapsulation layer; the other is to avoid shrinkage and internal stress generation of the molding material during the encapsulation process, resulting in warping or position offset of the flip-chip package structure and affecting the accuracy of subsequent grinding (or cutting). Therefore, 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 type epoxy resin, 10-15 parts of curing agent, 40-50 parts of spherical or flaky filler, 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 reactive diluent, 0.5-1 part of defoaming agent, 0.5-1 part of degassing agent, and 0.5-1 part of rheological agent.

[0021] Furthermore, the spherical filler includes at least one of spherical silica filler and spherical alumina filler; the flaky filler includes flaky boron nitride filler;

[0022] The curing agent includes methylhexahydrophthalic anhydride curing agent;

[0023] The toughening agent includes acrylic rubber or polyethersulfone toughening agent;

[0024] The defoaming agent includes organosilicon defoaming agent;

[0025] The degassing agent includes high molecular weight polysiloxane degassing agent.

[0026] The present invention selects bisphenol F type epoxy resin with a low shrinkage rate and combines it with a high filling amount of inorganic fillers, significantly reducing the shrinkage rate of the molding material and reducing the risk of chip offset or warping during the curing process of the molding material; preferably, a compound filler of spherical and flaky shapes is used. On the one hand, the combination of the two can improve the filling density, reduce the shrinkage rate of the molding material matrix, and reduce internal stress, ensuring the dimensional stability of the second encapsulation layer. On the other hand, the spherical filler has good fluidity and the flaky filler has poor fluidity. The combination of the two can balance the fluidity of the material and regulate anisotropy. When the number of flip-chip package structures arranged is large and dense, the proportion of spherical fillers is increased. When the flip-chip package structures are arranged sparsely, the proportion of spherical fillers can be appropriately reduced.

[0027] Among them, the rheological agent can improve the fluidity of the material, ensure filling in all corners, and reduce the generation of bubbles; the defoaming agent promotes the rupture of bubbles and the degassing agent helps the bubbles escape before the material cures, effectively reducing the bubbles in the molding material and improving the quality and reliability of the second encapsulation layer.

[0028] In an embodiment of the present invention, the transparency of the second encapsulation layer is higher than that of the first encapsulation layer; in step (4), an optical alignment system and / or an automatic vision inspection system are used to identify individual packaging units and then perform cutting to ensure high precision and chip integrity during the cutting process.

[0029] As described above, the process method for reusing chips in the flip-chip package structure of the present invention has the following beneficial effects:

[0030] 1. The present invention ensures the integrity of the chip and the exposure of solder joints through processes such as re-encapsulation, grinding or cutting, peeling, and cutting, protects the chip with the remaining encapsulation material, reduces material waste, and improves the yield; 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.

[0031] 2. Through the improvement of the peeling layer formula, the nano-silica filler can improve the mechanical strength and thermal stability of the peeling layer while maintaining its flatness, enabling the package structures mounted on the peeling layer to maintain a consistent horizontal height, improving the precision during grinding or cutting, ensuring the integrity of the removed chips, and improving the yield.

[0032] 3. Through the improvement of the molding material formula, the present invention selects epoxy resin with a low shrinkage rate and combines it with a high filling amount of inorganic fillers, significantly reducing the shrinkage rate of the molding material and reducing the risk of chip offset or warping during the curing process of the molding material. Description of the Drawings

[0033] Figure 1Schematic diagram of the flip - chip package structure in Embodiment 1 of the present invention.

[0034] Figure 2 Schematic diagram of step S1 in Embodiment 1 of the present invention.

[0035] Figure 3 Schematic diagram of step S2 in Embodiment 1 of the present invention.

[0036] Figure 4 Schematic diagram of step S3 in Embodiment 1 of the present invention.

[0037] Figure 5 Schematic diagram of step S4 in Embodiment 1 of the present invention.

[0038] Figure 6 Schematic diagram of step S5 in Embodiment 1 of the present invention.

[0039] Figure 7 Schematic diagram of step S6 in Embodiment 1 of the present invention.

[0040] Element reference numeral description

[0041] 100, carrier; 200, release layer; 300, flip - chip package structure; 301, first encapsulation layer; 302, chip; 303, solder joint; 304, substrate; 305, solder ball; 400, re - encapsulation structure; 401, second encapsulation layer. Detailed implementation manners

[0042] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0043] Embodiment 1

[0044] This embodiment provides a process method for reusing a chip in a flip - chip package structure. Refer to Figure 1 , the flip - chip package structure 300 includes a substrate 304, a chip 302, a first encapsulation layer 301, and a solder ball 305. The chip 302 is flip - mounted on the back of the substrate 304. The solder joints 303 on the chip are electrically connected to the redistribution layer in the substrate. Underfill is filled between the chip and the substrate. The first encapsulation layer covers the chip and the underfill from the back of the substrate. The solder ball 305 is disposed on the front of the substrate and is electrically connected to the redistribution layer;

[0045] Specifically, it includes the following steps:

[0046] S1, refer to Figure 2 , coat the release layer 200 on the carrier 100;

[0047] S2. Reference Figure 3 , arrange and mount multiple flip-chip package structures 300 as shown in Figure 1 on the release layer 200 in an array layout with the solder balls 305 facing upward;

[0048] S3. Reference Figure 4 , use a molding material to encapsulate all the flip-chip package structures on the release layer to form a second encapsulation layer 401. The second encapsulation layer completely covers all the solder balls, and the entire encapsulated structure is a repackaging structure 400;

[0049] S4. Reference Figure 5 , grind the repackaging structure 400 from top to bottom to remove the solder balls, substrates, and underfill in the flip-chip package structure 300 until the solder joints of the chips are exposed;

[0050] S5. Reference Figure 6 , peel the repackaging structure 400 from the carrier 100;

[0051] S6. Reference Figure 7 , cut the repackaging structure into individual packaging units. Each packaging unit contains a single chip 302, and there is a first encapsulation layer 301 and a second encapsulation layer 401 outside the packaging unit. The two encapsulation layers can protect the chips.

[0052] Example 2

[0053] This example provides a process method for reusing chips in a flip-chip package structure. Compared with Example 1, the only difference is:

[0054] 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 flake boron nitride filler, 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 part of rheological agent.

[0055] In step S3, after mixing the above molding material evenly, slowly add it to the mold to encapsulate all the flip-chip package structures. First, cure at 80 - 100 °C, and then raise the temperature to 150 - 180 °C for complete curing.

[0056] Example 3

[0057] This example provides a process method for reusing chips in a flip-chip package structure. Compared with Example 2, the only difference is:

[0058] The molding material comprises the following components in parts by weight: 35 parts of bisphenol F type 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 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 part of rheological agent.

[0059] Example 4

[0060] This example provides a process method for chip removal and reuse in a flip chip package structure. Compared with Example 1, the only difference is that:

[0061] The material formulation of the release layer comprises the following components in parts by weight: 65 parts of organosilicon 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.

[0062] In step S1, after the above release layer material is mixed evenly, it is uniformly coated on the carrier by spin coating, knife coating or spraying process to ensure its thickness is consistent, and then cured at 120 - 150 °C.

[0063] In step S2, after the flip chip package structure 300 is mounted on the release layer 200 in an array arrangement with the solder balls 305 facing upwards, the entire release layer 200 is blown vertically from top to bottom, thereby applying a slight pressure above the package structure 300 to ensure uniform contact between it and the release layer, and warping or tilting can be avoided.

[0064] In summary, through the processes of re - encapsulation, grinding or cutting, and peeling, the present invention ensures the integrity of the chip and the exposure of the solder joints, protects the chip with the remaining encapsulation material, reduces material waste, and improves the yield; avoids the harmful waste liquid generated by pickling and the 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 disadvantages in the prior art and has high industrial utilization value.

[0065] Among them, the terms such as "upper", "lower", "left", "right", "front", "rear", "middle", and "one" cited in this specification are only for the convenience of clear description and do not limit the scope of implementation of the present invention. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope of implementation of the present invention.

[0066] The above - mentioned embodiments are only illustrative of the principles and effects of the present invention and are not used to limit the present invention. All equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should 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 a carrier, mounting a plurality of flip chip packaging structures on the peeling layer in an array arrangement with solder balls facing upward, and performing a blowing operation vertically from top to bottom on the entire peeling layer; (2) using a molding material to re-encapsulate all flip chip packaging structures on the peeling layer to form a second plastic encapsulation layer to obtain a re-encapsulated structure; 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 fillers and flaky fillers in total, 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 degassing agent, and 0.5-1 part of rheological agent; the spherical filler comprises at least one of spherical silica filler and spherical alumina filler; the flaky filler comprises flaky boron nitride filler; (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) 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), 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.

4. The process according to claim 3, 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.

5. The process according to claim 1, 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.

6. The process according to claim 1, characterized in that: 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 an organic silicon defoaming agent; and the degassing agent includes a high molecular weight polysiloxane degassing agent.

7. The process according to claim 2, 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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