Underfill material with a low coefficient of thermal expansion, method for preparing the same, and chip package structure

Abstract

The present invention provides an underfill material with a low coefficient of thermal expansion, a method for preparing the same, and a chip package structure. The underfill material contains, by mass%, 24% to 33% epoxy resin, 58% to 69% silica, 8% to 19% curing agent, 0.1% to 0.3% dyeing agent, and 0.2% to 0.4% adhesion promoter. The epoxy resin is a composite formulation of a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin. By curing the three composite resins—the trifunctional epoxy resin, the polyether-modified epoxy resin, and the naphthalene-type epoxy resin—with a curing agent, the underfill material is given basic performance. The performance of the underfill material is enhanced by using silica as a filler, and the adhesion promoter increases the adhesion between the underfill material and the substrate, thereby improving the reliability and service life of the chip package.

Description

Technical Field

[0001] The present invention belongs to the technical field of packaging of underfill materials, and particularly relates to an underfill material with a low coefficient of thermal expansion, a method for preparing the same, and a chip packaging structure.

Background Art

[0002] An underfill material is an important material in the packaging technology of electronic devices. It is mainly used to fill the narrow gap between a chip and a substrate, disperse the stress applied to the chip surface, relieve the internal stress caused by the mismatch of the coefficients of thermal expansion among the chip, solder, and substrate, reduce the stress impact between the chip and the substrate due to the difference in the coefficients of thermal expansion, improve the structural strength and reliability of the electronic device, and enhance the drop resistance performance between the chip and the substrate.

[0003] Whether an underfill material is effective is related to the difference in the coefficients of thermal expansion between the chip and the substrate. The lower the coefficient of thermal expansion of the underfill material, the better the adhesion degree to the chip surface, and the longer the service life of the chip. Furthermore, during actual application, the chip often faces various temperature and humidity conditions, and these conditions also affect the reliability and service life of the chip. Therefore, the underfill material not only needs to have a low coefficient of thermal expansion but also needs to have high moisture and heat resistance performance.

[0004] As can be seen from this, how to provide an underfill material with a low coefficient of thermal expansion, which has high moisture and heat resistance performance and excellent silicon adhesion, and improves the reliability and service life of the chip packaging, is an issue that those skilled in the art need to quickly solve.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention aims to provide an underfill material with a low coefficient of thermal expansion, a method for preparing the same, and a chip package structure, in order to solve at least the above-mentioned problems. [Means for solving the problem]

[0006] To achieve the above objectives, a first aspect of the present invention provides an underfill material with a low coefficient of thermal expansion, wherein the underfill material comprises, by mass%, 24% to 33% epoxy resin, 58% to 69% silica, 8% to 19% curing agent, 0.1% to 0.3% dyeing agent, and 0.2% to 0.4% adhesion promoter, and the epoxy resin is a composite formulation of a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin.

[0007] In the first embodiment, the mass percentage of the trifunctional epoxy resin is 4% to 20%, the mass percentage of the polyether-modified epoxy resin is 4% to 20%, and the mass percentage of the naphthalene-type epoxy resin is 4% to 20%.

[0008] In the first embodiment, the curing agent is Ancamine 2264.

[0009] In the first embodiment, the structural formula of the polyether-modified epoxy resin is as follows: [ka]

[0010] In the first embodiment, the trifunctional epoxy resin comprises at least one of MF-3285 and TPNE5501.

[0011] In the first embodiment, the naphthalene-type epoxy resin comprises at least one of SE-165 and EBA-65.

[0012] In the first embodiment, the dyeing agent includes carbon black.

[0013] In a second aspect of the present invention, a method for preparing an underfill material with a low coefficient of thermal expansion, as described in the first aspect, is provided, and the preparation method is A first slurry S1 is obtained by stirring and mixing each component according to its respective mass percentage, wherein the mass percentages of each component are specifically 24% to 33% epoxy resin, 58% to 69% silica, 8% to 19% curing agent, 0.1% to 0.3% dyeing agent, and 0.2% to 0.4% adhesion promoter. S2 involves transferring the first slurry to a three-roll mill and performing a dispersion process to obtain a second slurry that is uniformly dispersed. The method includes S3, which involves vacuum degassing the second slurry to obtain an underfill material.

[0014] In the second embodiment, the epoxy resin is a composite compound of a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin, wherein the mass percentage of the trifunctional epoxy resin is 4% to 20%, the mass percentage of the polyether-modified epoxy resin is 4% to 20%, and the mass percentage of the naphthalene-type epoxy resin is 4% to 20%.

[0015] A third aspect of the present invention provides a chip package structure comprising a base material, a chip provided on the base material, and a plurality of spaced solder bumps provided between the base material and the chip and electrically connected to the base and the chip, wherein a gap is formed between the base material and the chip, and the liquid underfill material with a low coefficient of thermal expansion described in the first aspect is provided on the edge of the base material, the liquid underfill material flows from one end of the gap to the other by capillary action to fill the gap, the liquid underfill material is hardened, and when hardening is complete, a chip package structure is obtained. [Effects of the Invention]

[0016] The beneficial effects are as follows: The underfill material with a low coefficient of thermal expansion provided by the present invention contains, by mass%, 24% to 33% epoxy resin, 58% to 69% silica, 8% to 19% curing agent, 0.1% to 0.3% dyeing agent, and 0.2% to 0.4% adhesion promoter. The epoxy resin is a composite formulation of a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin. The trifunctional epoxy resin combines the dual properties of alicyclic epoxy resin and glycidyl ester, possessing high reaction activity and high adhesion. The polyether-modified epoxy resin has low viscosity and a large number of flexible groups, thereby increasing the fluidity of the underfill material, reducing hardness, and improving curing shrinkage and flexibility. The naphthalene-type epoxy resin contains a naphthalene ring structure with high hydrophobicity and rigidity, maintaining good performance even in high-temperature environments, and exhibiting high Young's modulus, in-plane orientation, and The underfill material has a packing coefficient and a small free volume in which molecular chains can move, resulting in small expansion in the direction of the molecular chains. Furthermore, as the temperature rises, thermal expansion perpendicular to the direction of the molecular chains is suppressed, thus effectively reducing the coefficient of thermal expansion of the underfill material. Three types of resins, a composite trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin, are integrated by curing with a curing agent to impart basic performance to the underfill material. The performance of the underfill material is enhanced by using silica as a filler, the adhesion between the underfill material and the substrate is increased by using an adhesion promoter, and dyeing labeling is performed using a coloring agent. The underfill material prepared with the specific blending ratio of this application has excellent fluidity, a low coefficient of thermal expansion, and resistance to humid and heat, as well as excellent adhesion to silicon wafers, improving the reliability and service life of the chip package. [Brief explanation of the drawing]

[0017] To more clearly illustrate the examples of this specification or the technical concepts in the prior art, the following briefly introduces the drawings that may be used in the examples. Clearly, the drawings described below represent only a portion of the examples of the present invention, and those skilled in the art can obtain other drawings based on these without requiring any creative effort. [Figure 1] This is a flowchart of a method for preparing an underfill material with a low coefficient of thermal expansion according to the present application.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the present invention will be specifically described with reference to specific embodiments and examples, whereby the advantages and various effects of the present invention will be more clearly shown. Those skilled in the art should understand that these specific embodiments and examples are for explaining the present invention and do not limit the present invention.

[0019] Throughout this specification, unless otherwise specified, the terms used in this specification should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical terms and scientific terms used in this specification have the same meanings as those generally understood by those skilled in the art. In case of contradiction, the content of this specification shall prevail.

[0020] Unless otherwise specified, all kinds of raw materials, reagents, equipment, devices, etc. used in the present invention can be purchased from the market or manufactured by existing methods.

[0021] The present application provides an underfill material with a low coefficient of thermal expansion. The underfill material contains, by mass%, 24% - 33% of an epoxy resin, 58% - 69% of silica, 8% - 19% of a curing agent, 0.1% - 0.3% of a coloring agent, and 0.2% - 0.4% of an adhesion promoter. The epoxy resin is composed of a composite blend of a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin.

[0022] Specifically, the underfill material with a low coefficient of thermal expansion provided by the present invention contains, by mass percentage, 24% - 33% epoxy resin, 58% - 69% silica, 8% - 19% curing agent, 0.1% - 0.3% dyeing agent, and 0.2% - 0.4% adhesion promoter. The epoxy resin is composed of a composite blend of a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin. The trifunctional epoxy resin has the dual characteristics of an alicyclic epoxy resin and a glycidyl ester, and has high reaction activity and high adhesiveness. The polyether-modified epoxy resin has a low viscosity and a large number of flexible groups, so it can enhance the fluidity of the underfill material, reduce the hardness, and improve the curing shrinkage rate and flexibility. The naphthalene-type epoxy resin contains a naphthalene ring structure with high hydrophobicity and rigidity, and can still maintain good performance even under high-temperature environments. It has a high Young's modulus, in-plane orientation, and filling factor. Since the free volume in which the molecular chain can move is small, the expansion in the molecular chain direction is small, and with the increase in temperature, the thermal expansion perpendicular to the molecular chain direction is suppressed, so the coefficient of thermal expansion of the underfill material can be effectively reduced. The three types of resins, namely the trifunctional epoxy resin, the polyether-modified epoxy resin, and the naphthalene-type epoxy resin, which are compositely blended, are cured by a curing agent to be integrated, imparting basic performance to the underfill material. Using silica as a filler strengthens the performance of the underfill material, and an adhesion promoter is used to increase the adhesion between the underfill material and the substrate. In addition, a coloring agent is used for dyeing and labeling. The underfill material prepared according to the specific mixing ratio of the present application has excellent fluidity, a low coefficient of thermal expansion, and moisture and heat resistance performance, and has excellent adhesion to a silicon wafer, improving the reliability and service life of the chip package.

[0023] In some possible embodiments, the mass percentage of the trifunctional epoxy resin is 4% - 20%, the mass percentage of the polyether-modified epoxy resin is 4% - 20%, and the mass percentage of the naphthalene-type epoxy resin is 4% - 20%.

[0024] As those skilled in the art will understand, the epoxy resin of this application is a composite formulation of a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin. Each epoxy resin has specific properties and functions, and by compounding these three and adjusting their proportions, the thermal expansion coefficient, fluidity, and heat and moisture resistance of the underfill material can be controlled.

[0025] In some possible embodiments, the curing agent is Ancamine 2264.

[0026] This is because Ancamine 2264 is an epoxy curing agent that combines the characteristics of both alicyclic and aromatic compounds, has a high glass transition temperature, and can react with epoxy resins at a constant temperature to produce a thermosetting compound with a three-dimensional network structure. In this application, the performance of the underfill material is further enhanced by using this curing agent to bond a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin into a single integrated structure.

[0027] In some possible embodiments, the structural formula of the polyether-modified epoxy resin is as follows: [ka]

[0028] Polyether-modified epoxy resin can provide adhesive and mechanical properties to underfill materials as a material substrate, and can also improve the fluidity of the underfill material. The polyether-modified epoxy resin may be SE-4125P.

[0029] In some possible embodiments, the trifunctional epoxy resin comprises at least one of MF-3285 and TPNE5501.

[0030] Because trifunctional epoxy resins contain a large amount of highly reactive groups, they can provide crosslinking fulcrums for the curing reaction in the underfill, further improving the compatibility between polyether epoxy resins and naphthalene-type epoxy resins.

[0031] In some possible embodiments, the naphthalene-type epoxy resin comprises at least one of SE-165 and EBA-65.

[0032] Naphthalene-type epoxy resins can maintain good performance even in high-temperature environments of 150°C, and because their molecular structure includes a rigid molecular structure, the thermal expansion coefficient of the underfill material can be reduced. Furthermore, by adding silica, the thermal expansion coefficient of the underfill material can be further reduced, and the compatibility between silica and the underfill material can be improved.

[0033] In some possible embodiments, the dyeing agent comprises carbon black.

[0034] As those skilled in the art will understand, the dye is used to color the underfill material so that the chips are easily identifiable, and in this application, the dye may be carbon black.

[0035] Based on the overall concept of the invention, referring to Figure 1, the present application further provides a method for preparing an underfill material with a low coefficient of thermal expansion as described in the first embodiment, the preparation method is as follows: S1 is a method for obtaining a first slurry by stirring and mixing each component according to its respective mass percentage, wherein the mass percentages of each component are specifically 24% to 33% epoxy resin, 58% to 69% silica, 8% to 19% curing agent, 0.1% to 0.3% dyeing agent, and 0.2% to 0.4% adhesion promoter, and the stirring and mixing is performed using a centrifugal stirrer, with the stirring and mixing time of the centrifugal stirrer set to 115 to 155 s, the rotation speed to 1050 r / min, and the revolution speed to 1320 r / min. S2 is a process in which the first slurry is transferred to a three-roll mill and dispersed to obtain a second slurry that is uniformly dispersed, wherein the feeding interval of the three-roll mill is 10 to 40 μm and the discharge interval is 10 to 20 μm, S3 is a method for obtaining an underfill material by vacuum degassing the second slurry, wherein vacuum degassing is performed in a centrifugal stirrer, and the vacuum degassing time of the centrifugal stirrer is set to 65 to 95 s, the rotation speed to 1050 r / min, and the revolution speed to 1320 r / min.

[0036] In another selectable embodiment, the epoxy resin comprises a composite formulation of a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin, wherein the mass percentage of the trifunctional epoxy resin is 4% to 20%, the mass percentage of the polyether-modified epoxy resin is 4% to 20%, and the mass percentage of the naphthalene-type epoxy resin is 4% to 20%.

[0037] Based on the overall concept of the invention, this application further provides a chip package structure comprising a substrate, a chip provided on the substrate, and a plurality of spaced solder bumps provided between the substrate and the chip and electrically connected to the base and the chip, wherein a gap is formed between the substrate and the chip. The liquid underfill material with a low coefficient of thermal expansion described in the first embodiment is provided at the edge of the substrate, and the liquid underfill material flows from one end of the gap to the other by capillary action, filling the gap. The liquid of the underfill material is cured, Once curing is complete, a chip package structure is obtained.

[0038] The present application will be further described below, along with specific examples. It should be understood that these examples are for illustrative purposes only and do not limit the scope of protection provided for this application. In the examples below, experimental methods for which specific conditions are not described are generally measured according to national standards. If no applicable national standard exists, the procedure will be carried out according to general international standards, general conditions, or conditions recommended by the manufacturer.

[0039] The components of the underfill material in Comparative Examples 1-5 and Examples 1-4 are as shown in Table 1 below, in terms of mass percent.

[0040] [Table 1] Table 1. Mass percentage of raw material components JPEG2026521977000004.jpg93155

[0041] The underfill materials provided in Examples 1-4 and Comparative Examples 1-5 were subjected to measurements of storage modulus, glass transition temperature, thermal expansion coefficient, elongation / stretch strength, and fluidity. The specific measurement process is as follows.

[0042] 1. Fluidity measurement method: A rectangular Si wafer measuring 20 mm x 40 mm with a thickness of 0.5 mm was attached to a substrate at all four corners using 50 μm thick double-sided tape. Using a dispenser, the underfill material to be measured was applied horizontally along one side of the rectangular Si wafer (30-35 mg). The wafer was then placed on an electric heating plate at 90°C, and timing was started simultaneously. Due to the action of capillary force, the underfill material flowed along the bottom of the Si wafer. The time it took for the material to flow to half the Si wafer and the time it took to fill the entire surface were recorded.

[0043] 2. Coefficient of thermal expansion: Reference standards: ASTM E831~2019. Samples that had fully cured under conditions of 165°C for 2 hours were taken, and measurement samples measuring 5mm × 5mm × 10mm were prepared. The thermal expansion coefficient of the samples was measured using TMA (compression mode). The TMA parameters were set to preload load: 0.2N, first scan: room temperature - 260°C (heating rate 20°C / min), second scan: 40-260°C (heating rate 5°C / min). The curve data from the second heating stage was adopted, and the values ​​for the expansion coefficient CTE1 / 2 were taken at temperatures of 50°C~90°C and 160°C~200°C, respectively.

[0044] 3. Glass transition temperature Tg: The reference standard was ASTM E2254-2018. A fully cured sample was taken at 165°C for 2 hours, and a measurement sample of size 55 mm × 10 mm × 3 mm was prepared. Measurement was performed using DMA, with measurement mode: dual cantilever mode, vibration frequency: 1 Hz, amplitude: 10 μm, and heating rate: 5°C / min.

[0045] 4. Storage modulus: The reference standard was ASTM E2254-2018. A fully cured sample was taken at 165°C for 2 hours and prepared as a measurement sample of size 55mm × 10mm × 3mm. Measurement was performed using DMA with the following settings: measurement mode: dual cantilever mode, vibration frequency: 1Hz, amplitude: 10μm, heating rate: 5°C / min. The storage modulus was calculated using the value obtained between 25°C and 245°C.

[0046] 5. Reliability measurement: A sample was injected into a pudding mold with a diameter of 3 mm and a height of 2 mm. One end of the injected sample was brought into contact with a silicon wafer. The silicon wafer and the pudding mold were then fixed together and cured at 165°C for 2 hours. After removing the pudding mold and taking out the sample, it was measured using a push tester. The sample was then processed using a high-temperature, high-pressure steam tester (PCT) at 120°C and 100% humidity for 48 hours, taken out, and measured again with a push tester. The measurement speed of the push tester was 50 μm / s, and the contact height was 20 μm.

[0047] The measurement results are shown in Table 2.

[0048] [Table 2] Table 2 Measurement results JPEG2026521977000005.jpg165149

[0049] From the table above, the following can be seen:

[0050] (1) In Comparative Example 1, no trifunctional epoxy resin was added, and only polyether-modified epoxy resin and naphthalene-type epoxy resin were added. Although it had excellent fluidity, it had a high coefficient of thermal expansion, and during the curing reaction, the number of crosslinking points decreased, the proportion of flexible chain segments in the molecule increased, and as a result the material's Tg was small and its adhesive strength was small.

[0051] (2) In Comparative Example 2, polyether-modified epoxy resin was not added, and only naphthalene-type resin and trifunctional epoxy resin were added, resulting in reduced fluidity and a tendency to shrink after curing.

[0052] (3) In Comparative Example 3, naphthalene-type resin was not added, and only polyether-modified epoxy resin and trifunctional epoxy resin were added. This resulted in a decrease in the glass transition temperature of the underfill material, an increase in the coefficient of thermal expansion, and a significant decrease in the adhesive strength of Si after PCT treatment.

[0053] (4) In Comparative Examples 4 and 5, three types of resin were added in combination, but the amount added was outside the percentage range specified in the present application. As a result, the performance of the resulting underfill material was general, and the low adhesive strength of Si was unfavorable for chip packages.

[0054] (5) In Examples 1 to 4, the amount of silica added was the same. In Example 1, a trifunctional epoxy resin was used as the main resin, and a polyether-modified epoxy resin and a naphthalene-type resin were compounded to produce an underfill material with high Si adhesion and a high Tg. In Example 2, a polyether-modified epoxy resin was used as the main resin, and a trifunctional epoxy resin and a naphthalene-type resin were compounded to produce an underfill material with good fluidity. In Example 3, a naphthalene-type resin was used as the main resin, and a trifunctional epoxy resin and a polyether-modified epoxy resin were compounded to produce an underfill material with a low coefficient of thermal expansion and high Si adhesion after PCT treatment. In Example 4, a trifunctional epoxy resin was used as the main resin, and the percentages of polyether-modified epoxy resin and naphthalene-type resin were the same. The underfill material had excellent fluidity, a high Tg, and a low coefficient of thermal expansion. Even after PCT measurement, the underfill material still had strong Si adhesion, improving the reliability and service life of the chip packaging.

[0055] In summary, by adjusting the blending ratio of polyether-modified epoxy resin, naphthalene-type resin, and trifunctional epoxy resin within a fixed range for an underfill material constructed using raw material components within the range defined in this application, an underfill material with excellent fluidity, a low coefficient of thermal expansion, and excellent resistance to humid and heat can be obtained. In other words, this application provides an underfill material with a low coefficient of thermal expansion that has high resistance to humid and heat and excellent silicon adhesion, thereby improving the reliability and service life of chip packages. Furthermore, because the underfill material of this application has a relatively high glass transition temperature, it can be applied to a wider range of fields.

[0056] Finally, the terms “include,” “contain,” or any other variation thereof are intended to include non-exclusive inclusion, thereby including not only those elements but also other elements not explicitly listed, or elements specific to such process, method, article, or equipment.

[0057] While preferred embodiments of the present invention have been described, those skilled in the art, knowing the basic creative concept, can make further changes and modifications to these embodiments. Therefore, the appended claims are intended to be construed as encompassing the preferred embodiments and all changes and modifications that fall within the scope of the invention.

[0058] As will be apparent, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the invention. Thus, the present invention is also intended to include such modifications and variations if they fall within the scope of the claims of the present invention and the equivalent art.

Claims

1. An underfill material having a low coefficient of thermal expansion, wherein the underfill material consists of, by mass%, 24% to 33% epoxy resin, 62% silica, 8% to 19% curing agent, 0.2% dyeing agent, and 0.3% adhesion promoter, and the epoxy resin is a composite formulation of a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin. The mass percentage of the trifunctional epoxy resin is 4% to 20%, the mass percentage of the polyether-modified epoxy resin is 4% to 20%, and the mass percentage of the naphthalene-type epoxy resin is 4% to 20%. The curing agent is Ancamine 2264. The structural formula of the aforementioned polyether-modified epoxy resin is as follows: 【Chemistry 1】 The aforementioned trifunctional epoxy resin comprises at least one of MF-3285 and TPNE5501. The naphthalene-type epoxy resin comprises at least one of SE-165 and EBA-65. The aforementioned dye contains carbon black, An underfill material with a low coefficient of thermal expansion, characterized in that the adhesion promoter is NXH-635.

2. A method for preparing an underfill material with a low coefficient of thermal expansion according to claim 1, A first slurry is obtained by stirring and mixing each component according to its respective mass percentage, wherein the mass percentages of each component are specifically 24% to 33% epoxy resin, 62% silica, 8% to 19% curing agent, 0.2% dyeing agent, and 0.3% adhesion promoter. S2 involves transferring the first slurry to a three-roll mill and performing a dispersion process to obtain a second slurry that is uniformly dispersed. The process includes S3, which involves vacuum degassing the second slurry to obtain an underfill material, The epoxy resin is a composite compound of a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin, wherein the mass percentage of the trifunctional epoxy resin is 4% to 20%, the mass percentage of the polyether-modified epoxy resin is 4% to 20%, and the mass percentage of the naphthalene-type epoxy resin is 4% to 20%, characterized in that the preparation method is characterized in that the epoxy resin is a composite compound of a trifunctional epoxy resin, a polyether-modified epoxy resin, and a naphthalene-type epoxy resin is a composite compound of a trifunctional epoxy resin, the mass percentage of the trifunctional epoxy resin is 4% to 20%, and the mass percentage of the naphthalene-type epoxy resin is 4% to 20%.

3. A chip package structure comprising a substrate, a chip provided on the substrate, and a plurality of spaced solder bumps provided between the substrate and the chip and electrically connected to the base and the chip, wherein a gap is formed between the substrate and the chip, The liquid underfill material with a low coefficient of thermal expansion described in claim 1 is provided at the edge of the base material, and the liquid underfill material flows from one end of the gap to the other by capillary action to fill the gap. The liquid of the underfill material is cured, A chip package structure characterized in that a chip package structure is obtained when curing is complete.

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