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EP-4582506-B1 - UNDERFILL ADHESIVE FOR ELIMINATING FLOW MARKS AND PREPARATION METHOD THEREFOR, AND FLIP CHIP

EP4582506B1EP 4582506 B1EP4582506 B1EP 4582506B1EP-4582506-B1

Inventors

  • WU, DE
  • WANG, Shengquan
  • LIAO, Shuhang
  • SU, Junxing

Dates

Publication Date
20260513
Application Date
20240614

Claims (7)

  1. An underfill adhesive for eliminating flow marks, characterized in that the underfill adhesive consists of the following components in mass percent: 16%-24% of polyurethane modified epoxy resin, 52%-64% of a filler, 19%-23% of a curing agent, 0.2%-0.6% of an accelerator, and 0.1%-0.2% of a colorant; the filler is silicon dioxide, and an average particle diameter of the silicon dioxide is 0.6-5 µm; and the polyurethane modified epoxy resin is EPU300A.
  2. The underfill adhesive for eliminating flow marks according to claim 1, characterized in that the curing agent comprises an amine curing agent.
  3. The underfill adhesive for eliminating flow marks according to claim 2, characterized in that the accelerator comprises an imidazole accelerator.
  4. The underfill adhesive for eliminating flow marks according to claim 3, characterized in that the colorant comprises carbon black.
  5. A preparation method of the underfill adhesive for eliminating bottom flow marks according to any one of claims 1 to 4, characterized in that the preparation method comprises: stirring and mixing components according to a certain proportion to obtain preliminary mixed slurry, wherein the components comprise the following components in mass percent: 16%-24% of polyurethane modified epoxy resin, 52%-64% of a filler, 19%-23% of a curing agent, 0.2%-0.6% of an accelerator, and 0.1%-0.2% of a colorant; transferring the preliminary mixed slurry to a three-roller grinder for dispersion treatment to obtain uniformly dispersed slurry; and carrying out vacuum defoaming on the uniformly dispersed slurry to obtain the underfill adhesive.
  6. A flip chip, comprising a substrate, a chip disposed on a surface of the substrate, and a plurality of solder bumps which are disposed at intervals between the substrate and the chip and are electrically connected to the substrate and the chip, wherein a gap between the substrate and the chip is filled with an underfill material, characterized in that the underfill material is formed by curing the underfill adhesive for eliminating bottom flow marks according to any one of claims 1 to 4, the chip has a size of greater than 10 mm×25 mm, and the gap between the chip and the substrate is less than 30 µm.
  7. A preparation method of a flip chip, characterized by comprising: obtaining a flip chip body, wherein the flip chip body comprises a substrate, a chip disposed on a surface of the substrate, and a plurality of solder bumps which are disposed at intervals between the substrate and the chip and are electrically connected to the substrate and the chip, and a gap is formed between the substrate and the chip; disposing the underfill adhesive for eliminating bottom flow marks according to any one of claims 1 to 4 on an edge of the flip chip such that the underfill adhesive flows from one end of the gap to the other end of the gap by a capillary action, so as to fill the gap; and heating, allowing the underfill adhesive to be cured in the gap to obtain the flip chip.

Description

TECHNICAL FIELD The present invention belongs to the technical field of underfill adhesives for chips, and particularly relates to an underfill adhesive for eliminating flow marks, a preparation method thereof, and a flip chip. BACKGROUND To meet the reliability requirements of electronic devices, flip chips generally adopt an underfill technology. An underfill adhesive is a material suitable for the underfill technology of the flip chips, is generally permeated into a gap between a chip and a substrate by using the principle of a capillary action, and is then gradually solidified by thermal curing and filled in the gap between the chip and the substrate, so as to protect high-density solder bumps between the chip and the substrate as well as the chip. As shown in FIG. 1, a plurality of contact pads 3 are disposed at intervals at an upper end of a substrate 1, bottom-touching metals 4 having a number matched with that of the contact pads are correspondingly disposed at a lower end of a chip 2, a solder bump 5 is disposed between each contact pad and the corresponding bottom-touching metal, a solder mask 6 is disposed between two adjacent contact pads, a passivation layer 7 is disposed between two adjacent bottom-touching metals, and a gap formed among the chip, the substrate, and the solder bumps is filled with an underfill material 8, so that the chip, the substrate, and the solder bumps are protected, a stress loaded on a surface of the chip can be dispersed, and meanwhile, an internal stress caused by mismatch among coefficients of thermal expansion of the chip, the substrate, and the solder bumps is alleviated, the chip can be prevented from damages caused by physical, chemical, and other environmental factors, and the processability, reliability, and service life of the chip and packaging devices can be improved. However, an existing underfill material formed after curing of an underfill adhesive often cracks and cannot continue to protect the chip; and at the same time, when the underfill adhesive flows in the gap formed among the chip, the substrate, and the solder bumps, flow marks are also produced, which is not conducive to the protection of the chip. Therefore, how to provide an underfill adhesive to inhibit the production of the flow marks and enhance the protection effect of the chip is a technical problem that needs to be solved urgently by those skilled in the art. US 2023/260948 A1 discloses an underfill for chip packaging comprising epoxy resin, silica particles as filler, curing agent, accelerator and colorant. SUMMARY The present invention aims to provide an underfill adhesive for eliminating flow marks, a preparation method thereof, and a flip chip, so as to solve at least one of the above-mentioned technical problems. To achieve the above object, a first aspect of the present invention provides an underfill adhesive for eliminating flow marks, where the underfill adhesive includes the following components in mass percent: 16%-24% of polyurethane modified epoxy resin, 52%-64% of a filler, 19%-23% of a curing agent, 0.2%-0.6% of an accelerator, and 0.1%-0.2% of a colorant. In the first aspect, the filler includes silicon dioxide, and an average particle diameter of the silicon dioxide is 0.6-5 µm. In the first aspect, the curing agent includes an amine curing agent. In the first aspect, the accelerator includes an imidazole accelerator. In the first aspect, the colorant includes carbon black. A second aspect of the present invention provides an underfill adhesive, where the underfill adhesive consists of epoxy resin, a filler, a curing agent, an accelerator, and a colorant; and the epoxy resin includes polyurethane modified epoxy resin. In the second aspect, the filler includes silicon dioxide, and an average particle diameter of the silicon dioxide is 0.6-5 µm; and/or, the curing agent includes an amine curing agent; and/or, the accelerator includes an imidazole accelerator; and/or, the colorant includes carbon black. A third aspect of the present invention provides a preparation method of an underfill adhesive for eliminating bottom flow marks as described in the first aspect, where the preparation method includes: stirring and mixing components according to a certain proportion to obtain preliminary mixed slurry, where the components include the following components in mass percent: 16%-24% of polyurethane modified epoxy resin, 52%-64% of a filler, 19%-23% of a curing agent, 0.2%-0.6% of an accelerator, and 0.1%-0.2% of a colorant; transferring the preliminary mixed slurry to a three-roller grinder for dispersion treatment to obtain uniformly dispersed slurry; and carrying out vacuum defoaming on the uniformly dispersed slurry to obtain the underfill adhesive. A fourth aspect of the present invention provides a flip chip, including a substrate, a chip disposed on a surface of the substrate, and a plurality of solder bumps which are disposed at intervals between the substrate and the ch