A mold cleaning material containing a microencapsulated polyamic acid salt and a method for preparing the same

Abstract

The present application relates to a kind of containing microencapsulated polyamide acid salt and its preparation method, belong to semiconductor packaging material technical field.The mold cleaning material includes rubber matrix material and the microencapsulated polyamide acid salt dispersed therein;The core material of the microencapsulated polyamide acid salt is polyamide acid salt, and wall material is hot melt material;When heating to mold cleaning temperature, the wall material melts and releases the polyamide acid salt in core material, and the polyamide acid salt thermal decomposition produces triethylamine as cleaning agent.The mold cleaning material of the present application is convenient to process, no damage to mold, high cleaning efficiency, and no secondary pollution, suitable for semiconductor packaging mold, precision injection mold and other fields.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor packaging materials technology, and relates to a mold clearing material containing microencapsulated polyamic acid salt and its preparation method. Background Technology

[0002] In semiconductor packaging processes, especially in transfer molding, molds are repeatedly used under high temperature and pressure. Resin components, release agents, and other additives in the epoxy molding compound gradually form stubborn residues on the mold surface. If these residues are not removed in time, they can reduce the dimensional accuracy of the mold cavity, leading to defects such as flash, missing material, and mold sticking in the packaged products, severely impacting packaging yield and production efficiency. Therefore, regular mold cleaning is a necessary step in semiconductor packaging production.

[0003] Currently, the mold cleaning methods widely used in industry are mainly divided into two categories: one is physical abrasive mold cleaning materials, represented by melamine resin, which remove contaminants by mechanical action through the melting and flow of resin at high temperature and friction on the mold surface; the other is chemical bonding or decomposition mold cleaning materials, which usually complete the bonding of dirt and rubber through dirt-loving functional groups (or mold cleaning groups), or soften or decompose resin residues through chemical action.

[0004] Invention patent CN120757928A discloses a mold cleaning material for semiconductor packaging molds. This cleaning material uses a mixture of C5-C15 n-alkanes and isoalkanes as a cleaning agent, or uses isododecane as a cleaning agent. Invention patent CN112898687A utilizes the peeling and softening effect of the base adhesive to weaken the interaction between dirt and the mold, and then uses the adhesiveness of rubber, the scraping effect of filler, and the adsorption effect of molecular sieves to thoroughly remove dirt from the mold surface.

[0005] However, existing chemical cleaning mold cleaning materials still have the following technical defects: First, the release behavior of the cleaning agent is uncontrollable, and the cleaning agent is exhausted too early, making it impossible to completely remove deep residues; Second, the cleaning effect is limited to the macroscopic surface of the mold, and deep contaminants in the microscopic interface cannot be effectively removed, and long-term accumulation will accelerate mold damage; Third, the low utilization rate of the cleaning agent leads to high mold cleaning frequency and large material consumption, which increases production costs and process time. Summary of the Invention

[0006] The purpose of this invention is to provide a mold cleaning material containing microencapsulated polyamic acid salt and its preparation method. The prepared mold cleaning material is easy to process, does not damage the mold, has high cleaning efficiency, and does not cause secondary pollution.

[0007] The objective of this invention can be achieved through the following technical solutions: A mold-clearing material containing microencapsulated polyamic acid salt, the mold-clearing material comprising a rubber matrix material and microencapsulated polyamic acid salt dispersed therein; The core material of the microencapsulated polyamic acid salt is polyamic acid salt, and the wall material is a hot-melt material. When heated to the mold clearing temperature, the wall material melts and releases the polyamic acid salt in the core material. The polyamic acid salt decomposes to produce triethylamine as a cleaning agent.

[0008] As a preferred embodiment of the present invention, the mold-clearing material comprises, by weight, 65-75 parts of rubber matrix material, 10-15 parts of microencapsulated polyamic acid salt, 10-20 parts of reinforcing agent and 5-10 parts of surfactant.

[0009] As a preferred embodiment of the present invention, the rubber matrix material is one of uncured silicone rubber, fluororubber, and 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 microencapsulated polyamic acid salt comprises a first microcapsule and a second microcapsule in a ratio of 1:(2~3), and the melting point of the wall material of the first microcapsule is lower than that of the wall material of the second microcapsule.

[0012] As a preferred embodiment of the present invention, the wall material of the first microcapsule is polyethylene wax, and the wall material of the second microcapsule is polylactic acid.

[0013] As a preferred embodiment of the present invention, the diamine is one or more of 4,4'-diaminodiphenyl ether, m-phenylenediamine, and p-phenylenediamine; the diacid is one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and 4,4'-oxobisphthalic anhydride.

[0014] In a preferred embodiment of the present invention, the reinforcing agent is silica.

[0015] As a preferred embodiment of the present invention, the surfactant is one or more of fluorinated surfactants, organosilicon surfactants, and nonionic surfactants.

[0016] A method for preparing a mold-clearing material containing microencapsulated polyamic acid salt includes the following steps: S1. According to the weight parts, the rubber matrix material and the reinforcing agent are mixed in the first stage to obtain the masterbatch. The first stage mixing conditions are 80~100℃ for 10~20min. S2. The masterbatch is mixed with microencapsulated polyamic acid salt and surfactant in a second stage of low-temperature mixing to obtain a uniform rubber compound. The second stage mixing conditions are 60~80℃ for 5~15min. S3. The rubber material is shaped and sliced ​​to obtain the mold clearing material.

[0017] This invention achieves the staged release of the cleaning component, polyamic acid salt, by encapsulating it within microcapsules with wall materials of different melting points. Utilizing the melting properties of the microcapsule wall materials at specific temperatures, the invention encapsulates polyamic acid salt within microcapsules. In the 120-150°C stage, the low-melting-point microcapsules rupture first, releasing a small amount of triethylamine, which softens and swells the resin residue on the mold surface. In the 170-190°C stage, the high-melting-point microcapsules rupture further, releasing a large amount of triethylamine, which thoroughly decomposes the deep-seated residue that has already undergone the softening treatment in the previous stages. This avoids the premature volatilization loss caused by the one-time release of the cleaning agent in existing technologies, thereby effectively improving the utilization rate of triethylamine, increasing cleaning efficiency, significantly reducing cleaning agent waste, and lowering the consumption of mold cleaning materials.

[0018] Furthermore, the lower-temperature pre-softening stage creates microcracks and swelling channels on the surface of resin residues, providing a penetration path for the triethylamine released at higher temperatures. This allows the cleaning agent to penetrate the micro-defects formed during mold use, achieving thorough removal of contaminants at their source and reducing mold precision degradation and product defects caused by the accumulation of micro-residues.

[0019] This invention has good tolerance for temperature fluctuations and temperature deviations during the mold clearing process, reducing the requirements for equipment precision and operator proficiency in the mold clearing process, and is more suitable for industrial continuous production.

[0020] Microcapsule wall materials isolate polyamic acid salts from the external environment, preventing them from coming into contact with moisture, air, or acidic substances in the rubber matrix during room temperature storage, thus significantly extending the shelf life of the mold-clearing material.

[0021] The beneficial effects of this invention are: The mold-cleaning material prepared in this invention comprises a rubber matrix and microencapsulated polyamic acid salts. When heated to the mold-cleaning temperature, the polyamic acid salts thermally decompose and release triethylamine, which acts on resin residues on the mold surface, achieving chemical cleaning. This invention encapsulates the polyamic acid salts within microcapsules formed by a thermoplastic wall material. At room temperature and during the initial heating phase of mold cleaning, the wall material remains intact, preventing premature decomposition or volatilization of the polyamic acid salts. Only when the temperature reaches the set melting temperature of the wall material do the microcapsules rupture and release the polyamic acid salts from the core material, which then thermally decomposes to produce triethylamine. This invention, by introducing polyamic acid salts into the rubber matrix and utilizing their characteristic of releasing triethylamine in situ at high temperatures, achieves efficient softening and decomposition of cured resin residues on the mold surface. Simultaneously, the rubber matrix vulcanizes during the mold-cleaning process, allowing it to be peeled off along with the softened residues upon cooling, achieving a dual synergistic effect of "chemical cleaning + physical peeling." Detailed Implementation

[0022] 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.

[0023] It should be noted that in the following examples and comparative examples, the uncured silicone rubber is methyl vinyl silicone rubber (type 110-2), the silica is AEROSIL R972, and the surfactant is fluorinated surfactant FC-4430. Unless otherwise specified, the present invention does not specifically limit the source of other raw materials used. Commercially available products or products prepared by conventional preparation methods well known to those skilled in the art can be used. Experimental methods without specific conditions are all conventional methods and conditions well known in the art.

[0024] In the following examples and comparative examples, the preparation methods of the first microcapsule and the second microcapsule are as follows: Under nitrogen protection and at 0°C, 4,4'-diaminodiphenyl ether was dissolved in anhydrous DMF, then pyromellitic dianhydride was added, and the mixture was stirred for 20 h. Triethylamine was then added, and the mixture was stirred again to obtain a polyamic acid salt solution. The molar ratio of 4,4'-diaminodiphenyl ether, pyromellitic dianhydride, and triethylamine was 1:1.02:2. The solution was poured into 500 mL of deionized water to precipitate, filtered, freeze-dried for 48 h, and ground until the particle size was ≤10 μm to obtain polyamic acid salt powder. 5 g of polyethylene wax (PEW-0278) was heated and melted, and 5 g of polyamic acid salt powder (core / wall material mass ratio 1:1) was added. The mixture was stirred at 1000 rpm for 15 min to form a suspension. The suspension was then subjected to a 5000... Pre-cooled deionized water (containing 1 wt% polyvinyl alcohol) was added dropwise at rpm and stirred continuously for 30 min. After centrifugation at 5000 rpm for 10 min, the mixture was washed three times with deionized water, dried under vacuum at 40℃ for 24 h, and passed through a 200-mesh sieve to obtain polyethylene wax microcapsule powder (first microcapsule).

[0025] 2g of PLA (Luminy® D070) was dissolved in 40mL of dichloromethane, and 1.5g of polyamic acid salt powder (core / wall ratio 0.75:1) was added. The mixture was ultrasonically dispersed to obtain an oil phase. The oil phase was injected into 200mL of an aqueous solution containing 1.5wt% polyvinyl alcohol and emulsified at 8000rpm for 6min to form an O / W emulsion with an oil-to-water ratio of 1:5 (v / v). The mixture was stirred at 30℃ for 12h, then centrifuged at 5000rpm for 10min, washed three times with deionized water, freeze-dried for 24h, and passed through a 200-mesh sieve to obtain the second microcapsule.

[0026] Example 1

[0027] Preparation of mold cleaning material: S1. According to the weight, 70 parts of uncured silicone rubber and 15 parts of silica are mixed in the first stage to obtain masterbatch. The first stage mixing conditions are 90℃ for 15 minutes. S2. The masterbatch is mixed with 12 parts of the first and second microcapsules in a ratio of 1:2.5 and 8 parts of surfactant in a second stage of low-temperature mixing to obtain a uniform rubber compound. The second stage mixing conditions are 70℃ for 10 minutes. S3. Mold and slice the rubber material to obtain the mold clearing material.

[0028] Example 2

[0029] Preparation of mold cleaning material: S1. According to the weight, 65 parts of uncured silicone rubber and 10 parts of silica are mixed in the first stage to obtain masterbatch. The first stage mixing conditions are 80℃ for 10 minutes. S2. The masterbatch is mixed with 10 parts of the first and second microcapsules in a ratio of 1:2 and 5 parts of surfactant in a second stage of low-temperature mixing to obtain a uniform rubber compound. The second stage mixing conditions are 60℃ for 5 minutes. S3. Mold and slice the rubber material to obtain the mold clearing material.

[0030] Example 3

[0031] Preparation of mold cleaning material: S1. According to the weight, 75 parts of uncured silicone rubber and 20 parts of silica are mixed in the first stage to obtain masterbatch. The first stage mixing conditions are 100℃ for 20 minutes. S2. The masterbatch is mixed with 10-15 parts of the first and second microcapsules in a ratio of 1:3 and 10 parts of surfactant in a second stage of low-temperature mixing to obtain a uniform rubber compound. The second stage mixing conditions are 80℃ for 15 minutes. S3. Mold and slice the rubber material to obtain the mold clearing material.

[0032] Example 4

[0033] It is basically the same as Example 1, except that the ratio of the first microcapsule to the second microcapsule in this example is 1:5.

[0034] Example 5

[0035] It is basically the same as Example 1, except that the rubber matrix material in this example is EPDM rubber.

[0036] Comparative Example 1 This is essentially the same as Example 1, except that only the first microcapsule is used in this comparative example.

[0037] Comparative Example 2 This is essentially the same as Example 1, except that only the second microcapsule is used in this comparative example.

[0038] Comparative Example 3 This is basically the same as Example 1, except that the polyamic acid salt in this comparative example was not microencapsulated.

[0039] Performance testing: 1. Mold clearing effect: The cleaning materials used in the above embodiments and comparative examples were used to clean semiconductor packaging molds. The cleaning conditions were: first, the temperature was raised to 120°C and held for 3 minutes (1.0 MPa), then the temperature was raised to 180°C and held for 8 minutes. The dirt residue rate after cleaning was calculated, and the cleaning effect was determined. The criteria for determining the cleaning effect were as follows: A dirt residue rate of ≤5% is considered excellent; A dirt residue rate of 5-20% is considered good; A dirt residue rate >20% is considered poor.

[0040] 2. Integrity of mold cleaning material peeling: Visually inspect whether the material has been completely peeled off after mold cleaning, and whether there are any broken or remaining pieces.

[0041] The test results are shown in the table below:

[0042] Based on the above data, Example 1 showed the best residual rate in mold cleaning, at only 1.5%, and all examples were superior to the comparative examples. Comparative Examples 1 and 2, which used only a single type of microcapsule, had residual rates as high as 7.1% and 4.3%, respectively, due to the lack of segmented synergistic effect. In Comparative Example 3, the unencapsulated polyamic acid salt had an even higher dirt residue rate of 8.95% due to premature evaporation of the cleaning agent, and it broke apart during peeling. This indicates that the mold cleaning material prepared in this invention can release material segmentally through microcapsules, and that the polyamic acid salt, when heated to the mold cleaning temperature, can thermally decompose and release triethylamine, thereby acting on the resin residue on the mold surface to achieve efficient and deep mold cleaning.

[0043] 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 shall still fall within the scope of the present invention.

Claims

1. A mold-clearing material containing microencapsulated polyamic acid salt, characterized in that, The mold-clearing material includes a rubber matrix material and microencapsulated polyamic acid salts dispersed therein; The core material of the microencapsulated polyamic acid salt is polyamic acid salt, and the wall material is a hot-melt material. When heated to the mold clearing temperature, the wall material melts and releases the polyamic acid salt in the core material. The polyamic acid salt decomposes to produce triethylamine as a cleaning agent.

2. The mold-clearing material containing microencapsulated polyamic acid salt according to claim 1, characterized in that, The mold-clearing material, by weight, comprises 65-75 parts of rubber matrix material, 10-15 parts of microencapsulated polyamic acid salt, 10-20 parts of reinforcing agent and 5-10 parts of surfactant.

3. The mold-clearing material containing microencapsulated polyamic acid salt according to claim 1, characterized in that, The rubber matrix material is one of uncured silicone rubber, fluororubber, and EPDM rubber.

4. The mold-clearing material containing microencapsulated polyamic acid salt 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.

5. The mold-clearing material containing microencapsulated polyamic acid salt according to claim 1, characterized in that, The microencapsulated polyamic acid salt includes a first microcapsule and a second microcapsule in a ratio of 1:(2~3), and the melting point of the wall material of the first microcapsule is lower than that of the wall material of the second microcapsule.

6. The mold-clearing material containing microencapsulated polyamic acid salt according to claim 1, characterized in that, The wall material of the first microcapsule is polyethylene wax, and the wall material of the second microcapsule is polylactic acid.

7. The mold-clearing material containing microencapsulated polyamic acid salt according to claim 4, characterized in that, The diamine is one or more of 4,4'-diaminodiphenyl ether, m-phenylenediamine, and p-phenylenediamine; the diacid is one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and 4,4'-oxobisphthalic anhydride.

8. The mold-clearing material containing microencapsulated polyamic acid salt according to claim 1, characterized in that, The reinforcing agent is silica.

9. The mold-clearing material containing microencapsulated polyamic acid salt according to claim 1, characterized in that, The surfactant is one or more of the following: fluorinated surfactant, organosilicon surfactant, and nonionic surfactant.

10. A method for preparing a mold-clearing material containing microencapsulated polyamic acid salt as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. According to the weight parts, the rubber matrix material and the reinforcing agent are mixed in the first stage to obtain the masterbatch. The first stage mixing conditions are 80~100℃ for 10~20min. S2. The masterbatch is mixed with microencapsulated polyamic acid salt and surfactant in a second stage of low-temperature mixing to obtain a uniform rubber compound. The second stage mixing conditions are 60~80℃ for 5~15min. S3. The rubber material is shaped and sliced ​​to obtain the mold clearing material.

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