PS carrier tape with intermediate layer barrier structure and preparation method thereof

Abstract

This invention discloses a PS carrier tape with an intermediate barrier structure and its preparation method, belonging to the field of electronic packaging materials technology. The PS carrier tape includes an upper surface layer, an intermediate layer, and a lower surface layer. The upper and lower surface layers are antistatic black material layers containing small molecule additives, and the intermediate layer is a modified polystyrene layer containing dispersed nanosheet barrier materials and nucleating agents. This invention introduces nanosheet barrier materials and nucleating agents into the intermediate layer, utilizing their synergistic effect to form a barrier effect and dense crystalline regions, effectively inhibiting the migration of small molecule additives from the upper and lower surface layers to the die opening, thus reducing die opening material accumulation at the source. Compared with existing technologies, this invention significantly reduces the surface defect density of the carrier tape and the quality of die opening material accumulation, while maintaining or improving tensile strength and antistatic properties, greatly extending the downtime cleaning cycle, improving production efficiency and product yield, and is suitable for surface mount packaging of high-end electronic components.

Description

Technical Field

[0001] This application relates to the field of electronic packaging materials, and more specifically, it relates to a PS carrier tape with an intermediate barrier structure and a method for preparing the same. Background Technology

[0002] In surface mount technology (SMT) production of electronic products, polystyrene (PS) carrier tape is a key encapsulation material used to carry and protect precision electronic components such as chips, resistors, and capacitors, enabling automated placement through its vias. Currently, high-performance PS carrier tapes are generally produced using a three-layer co-extrusion process: the middle layer is a white polystyrene (PS) substrate, while the top and bottom layers are black special materials with antistatic properties. The black material typically contains polystyrene resin, carbon black, antistatic agents, lubricants, antioxidants, and other small-molecule additives, as well as elastomers to improve toughness.

[0003] However, a long-standing technical challenge in the sheet extrusion process of this technology is the easy accumulation of material at the extrusion die. This accumulation mainly originates from small-molecule additives (such as lubricants and antistatic agents) in the black material formulation or from low-molecular-weight substances produced by resin decomposition at high processing temperatures. These substances gradually migrate to the surface during processing and then volatilize, condense, and accumulate at the die. Once this accumulation detaches and adheres to the sheet surface, it directly leads to appearance defects such as black spots and bumps in the final carrier tape product, and may cause uneven thickness or localized performance defects, severely affecting product yield and the accuracy and reliability of subsequent SMT assembly. This problem forces the production line to frequently stop to clean the die, which not only reduces production efficiency and increases production costs but also becomes a key bottleneck restricting the quality and stability of high-end carrier tape products.

[0004] To alleviate the problem of material buildup at the die orifice, existing technologies typically employ two approaches: one is to optimize extrusion process parameters, but this method offers limited improvement and has a narrow process window; the other is to add fluoropolymer processing aids, such as PPA, to the raw material, utilizing its spreadability on the die surface to reduce precipitate adhesion. However, the PPA approach is costly and carries potential environmental controversies. More importantly, existing solutions focus on reducing adhesion or adjusting processes "after material buildup occurs," failing to fundamentally inhibit the migration of small-molecule additives from the black material towards the die orifice. Therefore, developing a novel PS carrier tape capable of effectively blocking small-molecule migration from within the material structure, thereby significantly reducing die buildup at the source, has become a pressing technical problem in this field. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a PS carrier tape with an intermediate layer barrier structure and its preparation method.

[0006] This application provides the following technical solution:

[0007] In a first aspect, this application provides a PS carrier tape with an intermediate barrier structure, comprising an upper surface layer, an intermediate layer and a lower surface layer, wherein the upper surface layer and the lower surface layer are antistatic black material layers containing small molecule additives;

[0008] The intermediate layer is a modified polystyrene layer, in which nanosheet barrier material and nucleating agent are dispersed. Based on the total mass of the modified polystyrene layer, the mass fraction of the nanosheet barrier material is 1-10 wt%, and the mass fraction of the nucleating agent is 0.1-1 wt%.

[0009] Furthermore, the aforementioned nanosheet barrier material is selected from at least one of organically modified montmorillonite, two-dimensional layered double hydroxides, and graphene oxide.

[0010] Furthermore, the aforementioned nanosheet barrier material is organically modified montmorillonite, with a sheet thickness of 1-5 nm and an aspect ratio greater than 200.

[0011] Furthermore, the above-mentioned nucleating agent is a sorbitol-based nucleating agent or an organophosphate-based nucleating agent.

[0012] Dispersing nucleating agents in modified polystyrene layers serves two purposes. First, during melt co-extrusion, some nucleating agents migrate to the upper and lower surfaces, inducing the elastomers in the antistatic black layer to form fine and dense microcrystalline regions, reducing the solubility of soft polymers in small molecule additives, and inhibiting the migration of small molecules to the die orifice from the source. Second, the nucleating agents act as dispersion promoters for organically modified montmorillonite in the intermediate layer, promoting the uniform dispersion of montmorillonite in the matrix resin in a peeled state through intercalation expansion and interfacial bridging, thereby maximizing its barrier effect and adsorption anchoring capacity.

[0013] Furthermore, the aforementioned antistatic black layer comprises polystyrene resin, elastomer, carbon black, and lubricant.

[0014] Furthermore, based on the total mass of the antistatic black material layer, the polystyrene resin is 100 parts by mass, the elastomer is 14-16 parts by mass, the carbon black is 24-28 parts by mass, and the lubricant is 1.2-1.8 parts by mass.

[0015] Secondly, this application provides a method for preparing the above-mentioned PS carrier tape with an intermediate layer barrier structure, comprising:

[0016] Nanosheet barrier material, nucleating agent and polystyrene resin are mixed, melt blended and extruded granulated to obtain intermediate layer modified masterbatch;

[0017] Polystyrene resin, elastomer, carbon black, and lubricant are mixed and used as upper and lower surface layer raw materials. After melt blending and extrusion granulation, upper surface layer masterbatch and lower surface layer masterbatch are obtained respectively.

[0018] The intermediate layer modified masterbatch is used as the intermediate layer raw material. It is co-extruded with the upper and lower surface layer masterbatches using a three-layer co-extrusion casting process to form a three-layer composite structure of upper, middle and lower surface layers. After cooling and shaping, the three-layer co-extruded PS carrier tape is obtained.

[0019] Furthermore, in the process of preparing the intermediate layer modified masterbatch, the extrusion temperature is 180-220℃ and the screw speed is 250-350 rpm.

[0020] Furthermore, in the above three-layer co-extrusion casting process, the temperature of the middle layer extruder is set to 170-215℃, and the temperature of the upper and lower surface layer extruders is set to 160-220℃.

[0021] Preferably, the feeding section temperature of the upper and lower surface extruders is 155-165℃, the compression section temperature is 185-195℃, the metering section temperature is 205-215℃, and the die head temperature is 215-225℃; the feeding section temperature of the intermediate layer is 165-175℃, the compression section temperature is 195-205℃, the metering section temperature is 210-220℃, and the die head temperature is 210-230℃.

[0022] Furthermore, in the above three-layer co-extrusion casting process, the traction speed is 8-12 m / min and the cooling roller temperature is 35-45℃.

[0023] In summary, this application has the following beneficial effects:

[0024] This invention provides a PS carrier tape with an intermediate barrier structure and its preparation method. Addressing long-standing technical problems in existing technologies, such as die accumulation, frequent downtime, and surface defects caused by the migration of small molecule additives in the black layer, this invention achieves the following beneficial effects by constructing a technical solution with a specific intermediate barrier structure:

[0025] 1. This invention simultaneously introduces a nanosheet-like barrier material and a nucleating agent into the intermediate layer of polystyrene. The nanosheet-like barrier material, through its high aspect ratio sheet structure, creates a "barrier effect," significantly extending the migration path of small molecule additives, while simultaneously utilizing its surface polar groups to adsorb and anchor them. The nucleating agent, on the other hand, increases the crystallinity of the intermediate layer of polystyrene, forming dense crystalline regions, further compressing the migration channels of small molecules. Through the synergistic effect of these two mechanisms, the migration of small molecule additives to the die opening is fundamentally blocked, solving the problem of material accumulation.

[0026] 2. Because this invention fundamentally suppresses the migration of small molecules and the formation of material buildup at the die opening, the risks of appearance defects such as black spots and bumps caused by material buildup and adhesion, as well as uneven thickness and local performance defects, are eliminated. The surface defect density of the carrier tape of this invention is significantly reduced, and the surface cleanliness of the product is greatly improved, ensuring the uniformity of the carrier tape dimensions and the flatness of the surface. This ensures the pick-up accuracy and placement reliability of electronic components during the SMT assembly process, making it particularly suitable for high-end electronic components with stringent packaging environment requirements.

[0027] 3. By suppressing the generation of material accumulation at the die opening, this invention extends the die opening cleaning cycle from several hours to several days in the prior art, significantly reducing unplanned downtime caused by cleaning accumulated material, and significantly improving the effective operating rate of the equipment and output per unit time; at the same time, the scrap rate caused by surface defects is reduced, reducing the waste of raw materials and energy.

[0028] 4. While modifying the intermediate layer, this invention does not change the basic formulation of the upper and lower surface layers, thus ensuring the core performance of the carrier tape. The upper and lower surface layers are still antistatic black material layers containing carbon black; at the same time, the nanosheet barrier material plays a nano-reinforcing role in the intermediate layer, ensuring the structural stability of the carrier tape during forming, winding, and use. Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the precipitation principle of the modified PS carrier tape and the unmodified PS carrier tape provided in this application. Detailed Implementation

[0030] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Specific conditions not specified in the examples shall be carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0031] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0032] Example 1

[0033] This embodiment provides a three-layer co-extruded PS carrier tape with an intermediate barrier structure, the structure of which includes an upper surface layer, an intermediate layer and a lower surface layer, wherein the upper surface layer and the lower surface layer are antistatic black material layers, and the intermediate layer is a modified polystyrene layer.

[0034] The three-layer co-extruded PS carrier tape is prepared by the following process:

[0035] 1. Raw material preparation

[0036] (1) Antistatic black material layer:

[0037] Prepare the following raw materials by mass fraction: 100 parts polystyrene resin, 8 parts styrene-ethylene-butene-styrene block copolymer, 6 parts linear low-density polyethylene, 26 parts carbon black, 1.5 parts EBS wax, 0.3 parts antioxidant 1010, and 0.3 parts antioxidant 168. Mix the above components evenly in a high-speed mixer to obtain upper and lower surface layer raw materials. Then, add the obtained mixed raw materials to a twin-screw extruder for melt blending, extrusion granulation, and obtain upper and lower surface layer masterbatches for later use.

[0038] Styrene-ethylene-butene-styrene block copolymer (SEBS) and linear low-density polyethylene (LLDPE) are used as elastomers; EBS wax is used as a lubricant.

[0039] (2) Intermediate layer modified masterbatch:

[0040] The materials were prepared according to the following mass fractions: 94.7% polystyrene resin, 5% organically modified montmorillonite (OMMT), and 0.3% sorbitol nucleating agent. The organically modified montmorillonite had a sheet thickness of approximately 1 nm and an aspect ratio of approximately 300, and was purchased from Nanocor. The sorbitol nucleating agent was purchased from Milliken.

[0041] OMMT, nucleating agent, and polystyrene resin were premixed in a high-speed mixer according to the above proportions. The mixture was then added to a twin-screw extruder for melt blending, extrusion, and granulation. The extrusion temperature was 180-220℃ (controlled in stages from the feeding section to the die head), and the screw speed was 300 rpm. After cooling and pelletizing, the intermediate layer modified masterbatch was obtained for later use.

[0042] 2. Three-layer co-extrusion molding

[0043] PS carrier tape was prepared using a three-layer co-extrusion casting unit with a die width of 600 mm. Pre-made upper, middle, and lower surface masterbatches were added to their respective extruders. After melt plasticization, they were combined within the die through a three-layer co-extrusion distributor, forming a three-layer composite structure of upper, middle, and lower surface layers. The tape was then cast onto a cooling roller at 40°C with a traction speed of 10 m / min. After cooling and setting, the tape was wound up.

[0044] The feeding section of the upper and lower surface extruders has a temperature of 160℃, the compression section has a temperature of 190℃, the metering section has a temperature of 210℃, and the die head has a temperature of 220℃; the feeding section of the middle layer has a temperature of 170℃, the compression section has a temperature of 200℃, the metering section has a temperature of 215℃, and the die head has a temperature of 220℃.

[0045] The total thickness of the resulting PS carrier tape is 0.3 mm, of which the thickness of the upper layer is 0.05 mm, the thickness of the middle layer is 0.2 mm, and the thickness of the lower layer is 0.05 mm.

[0046] Example 2

[0047] The difference between this embodiment and Embodiment 1 lies in the composition of the intermediate layer masterbatch:

[0048] The materials were prepared according to the following mass fractions: 89.8% polystyrene resin, 10% organically modified montmorillonite (OMMT), and 0.2% sorbitol nucleating agent. The organically modified montmorillonite had a sheet thickness of approximately 1 nm and an aspect ratio of approximately 300, and was purchased from Nanocor. The sorbitol nucleating agent was purchased from Milliken.

[0049] Example 3

[0050] The difference between this embodiment and Embodiment 1 lies in the composition of the intermediate layer masterbatch:

[0051] The materials were prepared according to the following mass fractions: 98% polystyrene resin, 1% organically modified montmorillonite (OMMT), and 1% sorbitol nucleating agent. The organically modified montmorillonite had a sheet thickness of approximately 1 nm and an aspect ratio of approximately 300, and was purchased from Nanocor. The sorbitol nucleating agent was purchased from Milliken.

[0052] Example 4

[0053] The difference between this embodiment and Embodiment 1 lies in the composition of the intermediate layer masterbatch: an equal amount of two-dimensional layered double hydroxide is used as a nanosheet barrier material to replace the organically modified montmorillonite.

[0054] Example 5

[0055] The difference between this embodiment and Embodiment 1 lies in the composition of the intermediate layer masterbatch: an equal amount of graphene oxide is used as a nanosheet barrier material to replace the organically modified montmorillonite.

[0056] Example 6

[0057] The difference between this embodiment and Embodiment 1 lies in the process parameters of the three-layer co-extrusion molding, specifically:

[0058] The feeding section temperature of the upper and lower surface extruders is 155℃, the compression section temperature is 185℃, the metering section temperature is 205℃, and the die head temperature is 215℃; the feeding section temperature of the intermediate layer is 165℃, the compression section temperature is 195℃, the metering section temperature is 210℃, and the die head temperature is 215℃.

[0059] The cooling roller temperature is 35℃, the traction speed is 12 m / min, and the roll is wound up after cooling and shaping.

[0060] Example 7

[0061] The difference between this embodiment and Embodiment 1 lies in the process parameters of the three-layer co-extrusion molding, specifically:

[0062] The feeding section temperature of the upper and lower surface extruders is 165℃, the compression section temperature is 195℃, the metering section temperature is 215℃, and the die head temperature is 225℃; the feeding section temperature of the intermediate layer is 175℃, the compression section temperature is 205℃, the metering section temperature is 220℃, and the die head temperature is 230℃.

[0063] The cooling roller temperature is 45℃, the traction speed is 8 m / min, and the roll is wound up after cooling and shaping.

[0064] Comparative Example 1

[0065] The difference between this comparative example and Example 1 is that the intermediate layer is pure polystyrene resin without any modifiers, and the PS carrier tape is obtained through the same three-layer co-extrusion process.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 1 is that the intermediate layer does not contain a nucleating agent, and its specific composition is: 95 wt% polystyrene resin and 5 wt% organic modified montmorillonite.

[0068] Comparative Example 3

[0069] The difference between this comparative example and Example 1 is that the intermediate layer does not contain nano-barrier materials. The specific composition is: 99.7 wt% polystyrene resin and 0.3 wt% sorbitol nucleating agent.

[0070] Performance testing

[0071] Performance tests were conducted on the PS carrier tapes prepared in the examples and comparative examples.

[0072] I. Testing Methods

[0073] 1. Surface defect density: After placing the carrier tape in a constant temperature and humidity chamber (23℃, 50% RH) for 24 h, surface defects (including black spots, bumps, scratches, etc.) within a length of 100 m were continuously detected using a surface inspection instrument from Dr. Schenk GmbH, Germany. The number of defects was counted, and the defect density (defects / m²) was calculated. Each sample was measured 3 times, and the average value was taken.

[0074] 2. Material accumulation at the die opening: After 8 hours of continuous production, stop the machine and observe the material accumulation in the die opening area. Weigh the mass (mg) of the precipitate scraped off at the die opening using a precision balance.

[0075] 3. Tensile strength: determined according to GB / T 1040.3 standard.

[0076] 4. Surface resistivity: Measured according to GB / T 1410 standard.

[0077] II. Test Results

[0078] As shown in Table 1

[0079] Table 1.

[0080]

[0081] As can be seen from Table 1:

[0082] Comparative Example 1 is a pure PS interlayer, representing existing technology. In comparison, the embodiments of the present invention significantly reduce the material buildup at the die opening while maintaining the surface resistivity to meet electronic packaging requirements, proving that the present invention solves the material buildup problem caused by small molecule migration at its source; the surface defect density also decreases significantly, proving that reducing material buildup directly improves the cleanliness of the carrier tape surface; the tensile strength is maintained or even slightly improved, proving that the nanosheet barrier material plays a reinforcing role while performing its barrier function.

[0083] Comparative Example 2 contained only nanosheet barrier material without nucleating agent, and Comparative Example 3 contained only nucleating agent without nanosheet barrier material. Test results showed that while their build-up quality and surface defect density were better than those of the pure PS interlayer (Comparative Example 1), they were still significantly worse than the example containing both. More importantly, the performance of the examples was far superior to the simple sum of Comparative Examples 2 and 3, fully demonstrating a synergistic effect of "1+1>2" between the nanosheet barrier material and the nucleating agent—the nanosheets construct a physical barrier and adsorb small molecules, while the nucleating agent compresses the free volume to form a dense crystalline region. The two work together to form a three-dimensional dual barrier mechanism, which is something that those skilled in the art could not reasonably expect from the prior art.

[0084] Examples 2 and 3, which adjusted the amounts of nanosheet barrier material and nucleating agent within the content range defined in the claims, both achieved excellent barrier effects, proving that the numerical range defined in the claims is reasonable and optimal, ensuring both the realization of the technical effect and providing sufficient adjustment space for actual production. Examples 4 and 5, which replaced organically modified montmorillonite with two-dimensional layered double hydroxides or graphene oxide, both achieved technical effects comparable to those of organically modified montmorillonite, proving that the technical solution of the present invention is universal and does not depend on a specific type of nanosheet barrier material; those skilled in the art can flexibly choose according to actual needs. Examples 6 and 7, which adjusted the extrusion temperature, traction speed, and cooling roller temperature within the process parameter range defined in the claims, yielded products with properties essentially the same as those in the examples, proving that the technical solution of the present invention has good process robustness, can stably achieve excellent results within a wide process window, and possesses good industrial applicability.

[0085] In summary, this invention achieves the following outstanding substantive features and significant progress compared to existing technologies: First, it breaks through technological bias by introducing a combination of "nanoplate barrier material" and "nucleating agent" into the intermediate layer of PS carrier tape for the first time, fundamentally solving the problem of small molecule migration at the material structure level and opening up a completely new technical path; Second, comparative verification proves that there is a significant synergistic effect between the two, rather than a simple additive effect; Third, while maintaining antistatic and mechanical properties, the two major industry pain points of die accumulation and surface defects are solved simultaneously, achieving a comprehensive improvement with multiple benefits; Fourth, the excellent results achieved by various nanomaterials and a wide process window prove that the technical solution of this invention has universality and industrial applicability.

[0086] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A PS carrier tape with an intermediate layer barrier structure, characterized in that, It includes an upper surface layer, a middle layer and a lower surface layer, wherein the upper surface layer and the lower surface layer are antistatic black material layers containing small molecule additives; The intermediate layer is a modified polystyrene layer, in which nanosheet barrier material and nucleating agent are dispersed. Based on the total mass of the modified polystyrene layer, the mass fraction of the nanosheet barrier material is 1-10 wt%, and the mass fraction of the nucleating agent is 0.1-1 wt%.

2. The PS carrier tape with an intermediate layer barrier structure according to claim 1, characterized in that, The nanosheet barrier material is selected from at least one of organically modified montmorillonite, two-dimensional layered double hydroxide, and graphene oxide.

3. The PS carrier tape with an intermediate barrier structure according to claim 2, characterized in that, The nanosheet barrier material is organically modified montmorillonite, with a sheet thickness of 1-5 nm and an aspect ratio greater than 200.

4. The PS carrier tape with an intermediate layer barrier structure according to claim 1, characterized in that, The nucleating agent is a sorbitol-based nucleating agent or an organophosphate nucleating agent.

5. The PS carrier tape with an intermediate barrier structure according to claim 1, characterized in that, The antistatic black layer comprises polystyrene resin, elastomer, carbon black, and lubricant.

6. The PS carrier tape with an intermediate layer barrier structure according to claim 5, characterized in that, Based on the total mass of the antistatic black material layer, the polystyrene resin is 100 parts by mass, the elastomer is 14-16 parts by mass, the carbon black is 24-28 parts by mass, and the lubricant is 1.2-1.8 parts by mass.

7. A method for preparing a PS carrier tape with an intermediate layer barrier structure as described in any one of claims 1-6, characterized in that, It includes: Nanosheet barrier material, nucleating agent and polystyrene resin are mixed, melt blended and extruded granulated to obtain intermediate layer modified masterbatch; Polystyrene resin, elastomer, carbon black, and lubricant are mixed and used as upper and lower surface layer raw materials. After melt blending and extrusion granulation, upper surface layer masterbatch and lower surface layer masterbatch are obtained respectively. The intermediate layer modified masterbatch is used as the intermediate layer raw material. It is co-extruded with the upper and lower surface layer masterbatches using a three-layer co-extrusion casting process to form a three-layer composite structure of upper, middle and lower surface layers. After cooling and shaping, the three-layer co-extruded PS carrier tape is obtained.

8. The method for preparing a PS carrier tape with an intermediate barrier structure according to claim 7, characterized in that, During the preparation of the intermediate layer modified masterbatch, the extrusion temperature is 180-220℃ and the screw speed is 250-350 rpm.

9. The method for preparing a PS carrier tape with an intermediate layer barrier structure according to claim 7, characterized in that, In the three-layer co-extrusion casting process, the temperature of the middle layer extruder is set to 165-225℃, and the temperature of the upper and lower surface layer extruders is set to 155-225℃.

10. The method for preparing a PS carrier tape with an intermediate barrier structure according to claim 9, characterized in that, In the three-layer co-extrusion casting process, the traction speed is 8-12 m / min and the cooling roller temperature is 35-45℃.

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