A high-efficiency, low-residue semiconductor packaging mold cleaning material and its preparation method

Abstract

This invention relates to a high-efficiency, low-residue semiconductor packaging mold cleaning material and its preparation method, belonging to the technical field of semiconductor packaging materials. The cleaning material comprises a rubber matrix, polyamic acid salt, modified nanodiamond, and a surfactant. The polyamic acid salt decomposes at the cleaning temperature to release triethylamine, achieving latent-controlled release of the cleaning agent. The modified nanodiamond surface reversibly adsorbs triethylamine and, driven by the mold closing pressure, carries the cleaning agent into the microstructure of the mold, such as microcracks, achieving targeted deep cleaning. The synergistic effect of the polyamic acid salt and modified nanodiamond significantly improves the removal rate of residues within microcracks, while preventing premature volatilization of small molecule amines and exhibiting excellent storage stability. The cleaning material prepared by this invention combines high-efficiency cleaning, low residue, long lifespan, and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor packaging materials technology, and relates to a high-efficiency, low-residue semiconductor packaging mold cleaning material and its preparation method. Background Technology

[0002] In semiconductor packaging, epoxy molding compounds easily form residual contaminants on the mold surface and in microstructures such as microcracks and venting grooves, severely affecting packaging yield and mold life. Existing semiconductor packaging mold cleaning technologies are mainly divided into two categories: physical cleaning and chemical cleaning. Physical cleaning methods mainly include manual polishing, sandblasting, dry ice blasting, laser cleaning, and ultrasonic cleaning. While these methods can remove some surface contaminants, they often require stopping the machine to disassemble the mold, which is cumbersome, inefficient, and carries the risk of damaging the mold's delicate surface, making continuous online cleaning difficult. Laser cleaning technology, although able to remove contaminants from the mold surface through high-energy beam irradiation, requires precise control of light pulse parameters, involves high equipment investment, and also has cleaning blind spots for complex mold cavities.

[0003] In recent years, rubber-based chemical mold cleaning materials have gradually become the mainstream in the industry due to their advantages such as online in-mold cleaning and ease of operation. These materials typically use uncrosslinked or partially crosslinked synthetic rubber as a matrix, with detergents, reinforcing agents, and other additives added through a mixing process. During mold cleaning, the rubber material undergoes a crosslinking reaction upon heating, while the detergent migrates from the rubber matrix to the mold surface, softening, swelling, or chemically decomposing epoxy resin residues. However, the detergent, in the form of small-molecule amines, is directly dispersed in the rubber matrix. During mixing and storage, these small-molecule amines are prone to premature volatilization or migration to the surface, leading to decreased storage stability of the rubber compound and uneven cleaning performance in actual use. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high-efficiency, low-residue semiconductor packaging mold cleaning material and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions: A high-efficiency, low-residue semiconductor packaging mold cleaning material, comprising, by weight: 65-75 parts rubber material, 10-15 parts polyamic acid salt, 10-20 parts modified nanodiamond, and 5-10 parts surfactant. The polyamic acid salt decomposes and releases triethylamine as a cleaning agent when heated to the mold clearing temperature; the modified nanodiamond also serves as a reinforcing agent and cleaning agent carrier, with its surface amino groups reversibly adsorbing triethylamine and directionally transporting the triethylamine into the mold microcracks.

[0006] As a preferred embodiment of the present invention, the modified nanodiamond is prepared by the following method: S2-1: Carboxylated nanodiamonds are dispersed in thionyl chloride and refluxed at 60-80℃ for 12-24h. After centrifugation, washing and drying, acyl chloride nanodiamonds are obtained. S2-2: Disperse acyl chloride nanodiamonds in a diamine or polyamine solution, reflux at 40-80°C for 12-24 hours, and obtain the modified nanodiamonds after centrifugation, washing, and drying.

[0007] As a preferred embodiment of the present invention, the diamine includes one or more of ethylenediamine, hexamethylenediamine, butanediamine, 1,10-diaminodecane, and 1,12-diaminododecane; the polyamine is one or more of diethylenetriamine, triethylenetetramine, and polyethyleneimine.

[0008] As a preferred embodiment of the present invention, the carboxylated nanodiamond is prepared by stirring nanodiamond in a mixed acid at 70-90°C for 2-6 hours; wherein the mixed acid is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1.

[0009] As a preferred embodiment of the present invention, the rubber material is one of uncured silicone rubber, fluororubber, or EPDM rubber.

[0010] As a preferred embodiment of the present invention, the polyamic acid salt is prepared by polycondensation of diamine and diacid to form polyamic acid, followed by reaction with triethylamine.

[0011] As a preferred embodiment of the present invention, the diamine includes one or more of 4,4'-diaminodiphenyl ether, m-phenylenediamine, and p-phenylenediamine; the dianhydride includes one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and 4,4'-oxobisphthalic anhydride.

[0012] As a preferred embodiment of the present invention, the surfactant includes one or more of fluorinated surfactants, organosilicon surfactants, and nonionic surfactants.

[0013] A method for preparing a high-efficiency, low-residue semiconductor packaging mold cleaning material, the method comprising the following steps. S9-1: The rubber material and modified nanodiamond are mixed in the first stage to obtain the masterbatch; S9-2: The masterbatch is mixed with polyamic acid salt and surfactant in a second stage of low-temperature mixing to obtain a uniform rubber compound; S9-3: The rubber material is molded and sliced ​​to obtain the mold clearing material.

[0014] As a preferred embodiment of the present invention, the first mixing condition is 80~100℃ for 10~20 min, and the second mixing condition is 60~80℃ for 5~15 min.

[0015] In this invention, polyamate is used as a cleaning agent precursor. It remains chemically inert at room temperature and mixing temperatures, preventing premature decomposition and release of triethylamine. When the mold-cleaning material is heated to the mold-cleaning temperature, the polyamate undergoes thermal decomposition, generating triethylamine in situ. Compared to existing mold-cleaning materials that directly add small-molecule amines, the latent-release mechanism of this invention has the following advantages: First, triethylamine is "locked" within the polyamate structure and will not volatilize or migrate during rubber compound mixing, storage, and transportation, thus significantly improving the storage stability and service life of the mold-cleaning material and avoiding the reduction in cleaning effect due to premature loss of the cleaning agent; second, triethylamine is released instantaneously at the mold-cleaning temperature, forming a high local concentration at the contaminant interface, thereby quickly and effectively softening, swelling, or chemically destroying the cured cross-linked network of the epoxy molding compound, achieving efficient cleaning; third, the polyamic acid residue generated after the thermal decomposition of polyamate itself has a certain degree of viscoelasticity, which can adsorb the softened contaminants and assist in peeling during cooling, reducing secondary adhesion of residues to the mold surface.

[0016] This invention employs surface-functionalized nanodiamonds as both a reinforcing agent and a cleaning agent carrier. Compared to conventional reinforcing agents (such as silica), modified nanodiamonds offer multiple beneficial effects: First, nanodiamonds possess excellent mechanical properties, significantly improving the modulus, tear strength, and abrasion resistance of the rubber matrix, thereby enhancing the structural integrity and friction cleaning ability of the mold cleaning material under high-pressure mold closing conditions. Second, the amino functional groups introduced through covalent grafting on their surface can reversibly adsorb triethylamine released from the decomposition of polyamic acid salts. This adsorption further inhibits the rapid escape of triethylamine in the initial stage of high-temperature release, achieving a sustained-release effect and extending the effective action time of the cleaning agent. Furthermore, as rigid nanoparticles at the nanoscale, driven by the mold closing pressure, nanodiamonds can penetrate into microstructures on the mold surface—such as microcracks, venting groove gaps, and ejector pin hole walls—that are difficult to reach using traditional cleaning methods, following the flow of the rubber matrix. Triethylamine carried by nanodiamonds is then directionally transported to these cleaning blind spots and released, thereby achieving root removal of deep-seated hidden contaminants and extending the cleaning dimension from macroscopic surfaces to interfaces at the micrometer or even nanometer scale.

[0017] In this invention, polyamic acid salts and modified nanodiamonds do not act independently, but rather form a synergistic cleaning effect of generation-adsorption-transport-release. Polyamic acid salts continuously generate triethylamine at the mold-cleaning temperature. Part of the free triethylamine acts directly on the mold surface, while the rest is instantly captured by the amino groups on the nanodiamond surface. The adsorbed triethylamine, along with the nanodiamonds, is pressed deep into the microcracks, where it desorbs and releases again under the high-temperature environment inside the cracks, achieving a secondary targeted supply of the cleaning agent. This synergistic mechanism allows the cleaning agent to act not only on the macroscopic surface but also to be precisely delivered to the root of contaminant adhesion, thus significantly improving the cleaning efficiency in deep cavities, narrow crevices, and microcrack areas. Compared to traditional mold-cleaning materials, the mold-cleaning material of this invention significantly improves the removal rate of epoxy residues in microcracks. Simultaneously, due to the spherical morphology and nanoscale of nanodiamonds, their wear on the mold surface is actually lower than that of angular silica particles, ensuring efficient cleaning while extending the mold's service life. In addition, the volatilization loss of triethylamine during the mold cleaning process is significantly reduced, improving the working environment and reducing the risk of environmental pollution.

[0018] The beneficial effects of this invention are: This invention uses polyamic acid salts as a cleaning agent precursor, which are stable at room temperature and mixing temperature, but decompose to release triethylamine at the mold cleaning temperature. This avoids premature volatilization and migration of small molecule amines, significantly improving the storage stability and cleaning uniformity of the material. Simultaneously, surface-modified nanodiamonds serve as both reinforcement and carriers. Their excellent mechanical properties enhance the rubber matrix, while the reversible adsorption of triethylamine by surface amino groups enables slow release. Driven by mold closing pressure, they carry the cleaning agent into the microstructure of the mold, such as microcracks, achieving root-oriented cleaning. These two components form a synergistic chain of generation-adsorption-transport-release, allowing the cleaning agent to act on the macroscopic surface and be precisely delivered to hidden contaminant attachment points. Compared to traditional mold cleaning materials, this invention significantly improves the removal rate of epoxy residues in microcracks, and the spherical morphology of nanodiamonds causes less mold wear than silica, extending mold life and improving the working environment while ensuring efficient cleaning. Detailed Implementation

[0019] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0020] It should be noted that, unless otherwise specified, the present invention does not specifically limit the source of the raw materials used in the following embodiments. Commercially available products or products prepared by conventional preparation methods that are well known to those skilled in the art can be used. Experimental methods that do not specify specific conditions are all conventional methods and conventional conditions well known in the art.

[0021] Example 1

[0022] This embodiment provides a high-efficiency, low-residue semiconductor packaging mold cleaning material, which includes the following components by weight: 70 parts of methyl vinyl silicone rubber (grade 110-2, vinyl content 0.15%), 12 parts of polyamic acid salt, 15 parts of modified nanodiamond, and 8 parts of potassium perfluorooctyl sulfonate.

[0023] The preparation method of the polyamic acid salt is as follows: In a three-necked flask equipped with nitrogen protection and mechanical stirring, 200 mL of N,N-dimethylacetamide and 10.01 g of 4,4'-diaminodiphenyl ether are added and stirred for 1 h. Then, 10.91 g of pyromellitic dianhydride is added in three batches at 30 min intervals under ice-water bath conditions. After the addition is complete, stirring is continued for 6 h. Then, 5.06 g of triethylamine is added and stirring is continued for 2 h. The reaction solution is poured into 5 times its volume of deionized water to precipitate the precipitate. The precipitate is filtered, washed with deionized water and ethanol, dried under vacuum at 50°C for 24 h, and pulverized through a 200-mesh sieve to obtain the polyamic acid salt.

[0024] The method for preparing the modified nanodiamond is as follows: S2-1: Take 10 g of nanodiamond powder (average particle size 5~10 nm), add it to 150 mL of a mixed acid of concentrated sulfuric acid (98%) and concentrated nitric acid (68%) in a volume ratio of 3:1, sonicate for 30 min, stir at 80 °C for 4 h, cool and centrifuge, wash with deionized water and ethanol respectively, and vacuum dry at 60 °C to obtain carboxylated nanodiamond; S2-2: Take 8 g of carboxylated nanodiamonds, add 80 mL of thionyl chloride, reflux at 70 °C for 20 h under nitrogen protection, distill under reduced pressure, wash with tetrahydrofuran, centrifuge, and dry under vacuum at 40 °C to obtain acyl chloride nanodiamonds. S2-3: Take 6 g of acyl chloride nanodiamonds, add 60 mL of ethylenediamine, reflux at 60 °C for 20 h under nitrogen protection, centrifuge after cooling, wash with anhydrous ethanol and deionized water, and vacuum dry at 50 °C to obtain modified nanodiamonds with an amino density of 3.0 mmol / g.

[0025] The preparation method of the mold clearing material is as follows: methyl vinyl silicone rubber and modified nanodiamond are mixed in the first stage at a roller temperature of 90°C for 15 minutes and passed through a thin tube 5 times to obtain a masterbatch; the masterbatch is mixed with polyamic acid salt and potassium perfluorooctyl sulfonate in the second stage at a low temperature of 70°C for 10 minutes and passed through a thin tube 3 times to obtain a rubber compound; the rubber compound is calendered into a sheet with a thickness of 1.5 mm on a sheet press and cut into 50 mm × 50 mm square pieces to obtain the mold clearing material.

[0026] Example 2

[0027] The only difference between this embodiment and Embodiment 1 is that this embodiment provides a high-efficiency, low-residue semiconductor packaging mold cleaning material, which comprises the following components by weight: 65 parts methyl vinyl silicone rubber, 10 parts polyamic acid salt, 10 parts modified nanodiamond, and 5 parts potassium perfluorooctyl sulfonate. All other components are the same as in Embodiment 1.

[0028] Example 3

[0029] The only difference between this embodiment and Embodiment 1 is that this embodiment provides a high-efficiency, low-residue semiconductor packaging mold cleaning material, which comprises the following components by weight: 75 parts methyl vinyl silicone rubber, 15 parts polyamic acid salt, 20 parts modified nanodiamond, and 10 parts potassium perfluorooctyl sulfonate. All other components are the same as in Embodiment 1.

[0030] Example 4

[0031] The only difference between this embodiment and Embodiment 1 is that the rubber material used is EPDM 4045 (ethylene content 53.9%), and the surfactant used is BYK-307. All other aspects are the same as in Embodiment 1.

[0032] Example 5

[0033] The only difference between this embodiment and Embodiment 1 is that the first mixing condition in the preparation method of the mold clearing material is 80°C for 20 min and the second mixing condition is 60°C for 15 min. All other conditions are the same as in Embodiment 1.

[0034] Example 6

[0035] The only difference between this embodiment and Embodiment 1 is that the first mixing condition in the preparation method of the mold clearing material is 100°C for 10 min and the second mixing condition is 80°C for 5 min. All other conditions are the same as in Embodiment 1.

[0036] Example 7

[0037] The only difference between this embodiment and Example 1 is that ethylenediamine is replaced with hexamethylenediamine in the preparation of modified nanodiamonds; all other aspects are the same as in Example 1.

[0038] Comparative Example 1 The only difference between this comparative example and Example 1 is that unmodified nanodiamonds are used instead of modified nanodiamonds; all other aspects are the same as in Example 1.

[0039] Comparative Example 2 The only difference between this comparative example and Example 1 is that triethylamine is used instead of polyamic acid salt; otherwise, they are the same as in Example 1.

[0040] Comparative Example 3 The only difference between this comparative example and Example 1 is that silica is used instead of modified nanodiamond; otherwise, they are the same as in Example 1.

[0041] Performance testing Mold cleaning efficiency test: The mold cleaning materials of Examples 1-8 and Comparative Examples 1-9 were used to clean the packaging mold. The mold was closed and a pressure of 10 MPa was applied. The temperature was raised to 190°C and held for 10 min. The mold was then cooled to below 60°C and the mold was opened. The test piece was taken out and the mold cleaning efficiency was calculated. The mold cleaning efficiency (%) = (initial residual area ratio - residual area ratio after cleaning) / initial residual area ratio × 100%.

[0042] Microcrack cleaning effect test: H13 steel specimens were used, and V-shaped microcracks (2 μm width, 20 μm depth, 500 μm length, 1 mm interval between each crack) were pre-formed by laser etching. Epoxy molding compound was uniformly coated on the specimen surface, vacuum degassed, and then cured, allowing EMC to fill the cracks and cover the surface, resulting in a mold specimen with microcracks. After cleaning, the specimen was cut open along a line perpendicular to the crack direction, and the thickness of residual EMC at the bottom of the crack was observed using a field emission scanning electron microscope. Cleaning rate (%) = (1 - thickness of residual EMC in the crack after cleaning / original crack depth) × 100%.

[0043] Storage stability test: The mold-clearing material sheet was sealed in an aluminum-plastic composite bag (with built-in desiccant) and placed in a constant temperature and humidity chamber under the conditions of 40℃ and 75% relative humidity. After 60 days of aging, the sample was taken out and the mold-clearing efficiency was tested. The relative mold-clearing efficiency retention rate (%) was calculated as follows: (mold-clearing efficiency after aging / new initial mold-clearing efficiency) × 100%. The specific experimental results are summarized in the table below.

[0044]

[0045] The data in the table above shows that the mold-cleaning efficiency of Examples 1-7 all reached over 96.5%. In Comparative Example 1, the unmodified nanodiamond lacked surface amino adsorption capacity, resulting in a mold-cleaning efficiency of 88.5%. In Comparative Example 2, the efficiency decreased to 80.2% due to the volatilization of triethylamine during mixing and storage. In Comparative Example 3, using silica instead of modified nanodiamond for cleaning, the efficiency relied mainly on rubber friction and a small amount of free amine, resulting in only 84.6%. Examples 1-7 achieved a microcrack cleaning rate of 80-88%, while Comparative Examples 1-3 showed a significant decrease in microcrack cleaning rates, indicating that the amino groups on the modified nanodiamond surface adsorbing and carrying triethylamine into the microcracks is key to root cleaning. Examples 1-7 maintained an efficiency of ≥90% after 60 days of aging. Comparative Example 1 maintained an efficiency of 76.2%, mainly because the nanodiamond surface lacked adsorption capacity, and some triethylamine still migrated and was lost. Comparative Example 2, with direct addition of triethylamine, only achieved 60.4%, as free triethylamine is highly volatile. The retention rate of Comparative Example 3 was 89.1%, which is attributed to the adsorption effect of silica on amines.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention are still within the scope of the present invention.

Claims

1. A high-efficiency, low-residue semiconductor packaging mold cleaning material, characterized in that, The mold-clearing material comprises, by weight, the following components: 65-75 parts rubber material, 10-15 parts polyamic acid salt, 10-20 parts modified nanodiamond, and 5-10 parts surfactant. The polyamic acid salt decomposes and releases triethylamine as a cleaning agent when heated to the mold clearing temperature; the modified nanodiamond also serves as a reinforcing agent and cleaning agent carrier, with its surface amino groups reversibly adsorbing triethylamine and directionally transporting the triethylamine into the mold microcracks.

2. The high-efficiency, low-residue semiconductor packaging mold cleaning material according to claim 1, characterized in that, The modified nanodiamond was prepared by the following method: S2-1: Carboxylated nanodiamonds are dispersed in thionyl chloride and refluxed at 60-80℃ for 12-24h. After centrifugation, washing and drying, acyl chloride nanodiamonds are obtained. S2-2: Disperse acyl chloride nanodiamonds in a diamine or polyamine solution, reflux at 40-80°C for 12-24 hours, and obtain the modified nanodiamonds after centrifugation, washing, and drying.

3. The high-efficiency, low-residue semiconductor packaging mold cleaning material according to claim 2, characterized in that, The diamine includes one or more of ethylenediamine, hexamethylenediamine, butanediamine, 1,10-diaminodecane, and 1,12-diaminododecane; the polyamine is one or more of diethylenetriamine, triethylenetetramine, and polyethyleneimine.

4. The high-efficiency, low-residue semiconductor packaging mold cleaning material according to claim 2, characterized in that, The carboxylated nanodiamonds are prepared by stirring nanodiamonds in a mixed acid at 70-90°C for 2-6 hours; wherein the mixed acid is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:

1.

5. The high-efficiency, low-residue semiconductor packaging mold cleaning material according to claim 1, characterized in that, The rubber material is one of uncured silicone rubber, fluororubber, or EPDM rubber.

6. The high-efficiency, low-residue semiconductor packaging mold cleaning material according to claim 1, characterized in that, The polyamic acid salt is prepared by polycondensation of diamine and diacid to form polyamic acid, followed by reaction with triethylamine.

7. The high-efficiency, low-residue semiconductor packaging mold cleaning material according to claim 6, characterized in that, The diamine includes one or more of 4,4'-diaminodiphenyl ether, m-phenylenediamine, and p-phenylenediamine; the dianhydride includes one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and 4,4'-oxobisphthalic anhydride.

8. The high-efficiency, low-residue semiconductor packaging mold cleaning material according to claim 1, characterized in that, The surfactant includes one or more of fluorinated surfactants, organosilicon surfactants, and nonionic surfactants.

9. A method for preparing a high-efficiency, low-residue semiconductor packaging mold cleaning material as described in any one of claims 1 to 8, characterized in that, The preparation method includes the following steps. S9-1: The rubber material and modified nanodiamond are mixed in the first stage to obtain the masterbatch; S9-2: The masterbatch is mixed with polyamic acid salt and surfactant in a second stage of low-temperature mixing to obtain a uniform rubber compound; S9-3: The rubber material is molded and sliced ​​to obtain the mold clearing material.

10. The method for preparing a high-efficiency, low-residue semiconductor packaging mold cleaning material according to claim 9, characterized in that, The first stage of mixing conditions is 80~100℃ for 10~20 min, and the second stage of mixing conditions is 60~80℃ for 5~15 min.

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