Novel Silicone Hotmelt Solutions for Electronic Components

Ryosuke Yamazaki, K. Ozaki, Toru Imaizumi, Hidenori Matsuhima, Masayuki Hayashi, S. Yamamoto, Yoshito Ushio
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On the other hand, readily available silicone adhesives or encapsulants are mostly curable liquid or paste forms. Organic counterparts such as epoxy or acrylic materials offer “hotmelt” products to cover specific market needs in transfer molding (cylindrical tablet) or large area encapsulation (film/sheet). While the market demand for curable silicone hotmelt products is emerging, only a few such products have been realized thus far (this unmet demand is the second market need we investigated). Our recent study on silicone hotmelt has shown that thermal stress management is feasible even with silicone compositions producing relatively “hard” cured monolith; silicone hotmelt enables an extreme ratio of the raw materials, which is impossible by typical curable liquid compositions. In this presentation, we will introduce novel silicone hotmelt solutions to meet emerging urgent technological requirements such as ease of handling, thermal stability or reliability against thermal stress. The first solution is heat curable silicone hotmelt cylindrical tablet for transfer molding. This aims to achieve similar handling/property to epoxy molding compound (EMC) tablet with superior thermal stability. Silicone hotmelt technology combined with novel compounding technology enabled extreme hardness and CTE of the cured piece; it provides a tensile modulus of 8 GPa and a CTE of as low as 11 ppm/°C, which are comparable to typical EMC. It has been confirmed that molded piece with a PCB board did not show any warpage, indicating matched CTEs in a molded body. Furthermore, the prototype showed no significant degeneration in mechanical and adhesive properties up to 1000-hour exposure to 250°C. In conjunction with optimized melt/flow performance of the prototype, this can be a novel solution for electronics encapsulant applications requiring extreme thermal stability. The second solution is heat curable silicone hotmelt film for large area encapsulation or adhesion. Large area molding is an emerging trend in electronics to achieve higher production output. Utilizing curable liquid products in this application is cumbersome because it requires dam material for precise control of the layer thickness. Furthermore, CTE mismatch between silicone and the substrate becomes a serious issue because of the relatively large thermal stress coming from the large area size. On the other hand, material providing a modulus in GPa range (such as the aforementioned cylindrical tablet material) cannot be applied to flexible devices. To meet these needs, novel silicone hotmelt film prototypes have been developed. Cured monolith from this prototype provides a tensile modulus of 10–100 MPa and a CTE of 220 ppm/°C. While the CTE is high, the designed rheological property enabled excellent stress relaxation capability to minimize the thermal stress in a molded body. No warpage has been observed when molded onto an 8-inch wafer. Controlled modulus of the cured piece bestowed flexibility and low surface tackiness at the same time. The melt/flow performance was optimized for vacuum lamination with excellent gap-filling capability. Furthermore, this prototype exhibited excellent adhesion capability to various substrates including fluoro-based materials and precious metals such as gold. Unique features realized by this silicone hotmelt film are expected to meet emerging market needs in materials for large area encapsulation or adhesion. General trends in electronics include miniaturization of devices and simplification of the production process. As devices become smaller and thinner, encapsulant or adhesive is likely to be exposed to harsher conditions, i.e. higher temperature or stronger light. In light of these trends, silicone is becoming more and more suitable, but current usage of conventional silicone products is limited because of its low modulus and product form (liquid or paste). 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引用次数: 1

Abstract

Silicone materials are well recognized for their excellent photo/thermal stability, owing to which they are often used as adhesives or encapsulants in electronics applications. However, silicone materials can also present a challenge due to their high Coefficient of Thermal Expansion (CTE) which can generate thermal stress because of CTE mismatching with the substrate. While a “soft” silicone compensates for CTE mismatch through deformation during thermal stress in a device setting, this mismatch limits the use of “hard” silicone products in the market (this limitation was the first market need we addressed in our study). On the other hand, readily available silicone adhesives or encapsulants are mostly curable liquid or paste forms. Organic counterparts such as epoxy or acrylic materials offer “hotmelt” products to cover specific market needs in transfer molding (cylindrical tablet) or large area encapsulation (film/sheet). While the market demand for curable silicone hotmelt products is emerging, only a few such products have been realized thus far (this unmet demand is the second market need we investigated). Our recent study on silicone hotmelt has shown that thermal stress management is feasible even with silicone compositions producing relatively “hard” cured monolith; silicone hotmelt enables an extreme ratio of the raw materials, which is impossible by typical curable liquid compositions. In this presentation, we will introduce novel silicone hotmelt solutions to meet emerging urgent technological requirements such as ease of handling, thermal stability or reliability against thermal stress. The first solution is heat curable silicone hotmelt cylindrical tablet for transfer molding. This aims to achieve similar handling/property to epoxy molding compound (EMC) tablet with superior thermal stability. Silicone hotmelt technology combined with novel compounding technology enabled extreme hardness and CTE of the cured piece; it provides a tensile modulus of 8 GPa and a CTE of as low as 11 ppm/°C, which are comparable to typical EMC. It has been confirmed that molded piece with a PCB board did not show any warpage, indicating matched CTEs in a molded body. Furthermore, the prototype showed no significant degeneration in mechanical and adhesive properties up to 1000-hour exposure to 250°C. In conjunction with optimized melt/flow performance of the prototype, this can be a novel solution for electronics encapsulant applications requiring extreme thermal stability. The second solution is heat curable silicone hotmelt film for large area encapsulation or adhesion. Large area molding is an emerging trend in electronics to achieve higher production output. Utilizing curable liquid products in this application is cumbersome because it requires dam material for precise control of the layer thickness. Furthermore, CTE mismatch between silicone and the substrate becomes a serious issue because of the relatively large thermal stress coming from the large area size. On the other hand, material providing a modulus in GPa range (such as the aforementioned cylindrical tablet material) cannot be applied to flexible devices. To meet these needs, novel silicone hotmelt film prototypes have been developed. Cured monolith from this prototype provides a tensile modulus of 10–100 MPa and a CTE of 220 ppm/°C. While the CTE is high, the designed rheological property enabled excellent stress relaxation capability to minimize the thermal stress in a molded body. No warpage has been observed when molded onto an 8-inch wafer. Controlled modulus of the cured piece bestowed flexibility and low surface tackiness at the same time. The melt/flow performance was optimized for vacuum lamination with excellent gap-filling capability. Furthermore, this prototype exhibited excellent adhesion capability to various substrates including fluoro-based materials and precious metals such as gold. Unique features realized by this silicone hotmelt film are expected to meet emerging market needs in materials for large area encapsulation or adhesion. General trends in electronics include miniaturization of devices and simplification of the production process. As devices become smaller and thinner, encapsulant or adhesive is likely to be exposed to harsher conditions, i.e. higher temperature or stronger light. In light of these trends, silicone is becoming more and more suitable, but current usage of conventional silicone products is limited because of its low modulus and product form (liquid or paste). The novel technologies described in this presentation will break some of these barriers and open a door to utilize silicone in applications where it has never been used before.
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新型电子元件硅热熔胶解决方案
硅酮材料以其优异的光/热稳定性而闻名,因此它们经常被用作电子应用中的粘合剂或密封剂。然而,由于硅树脂材料的高热膨胀系数(CTE)可能会由于CTE与衬底不匹配而产生热应力,因此也会带来挑战。虽然“软”硅酮通过在设备设置中热应力期间的变形来补偿CTE错配,但这种错配限制了“硬”硅酮产品在市场上的使用(这一限制是我们在研究中解决的第一个市场需求)。另一方面,容易获得的硅酮粘合剂或密封剂大多是可固化的液体或糊状形式。有机对应物,如环氧树脂或丙烯酸材料提供“热熔”产品,以满足转移成型(圆柱形片剂)或大面积封装(薄膜/片材)的特定市场需求。虽然市场对可固化有机硅热熔胶产品的需求正在出现,但迄今为止只有少数此类产品已经实现(这一未满足的需求是我们调查的第二个市场需求)。我们最近对有机硅热熔胶的研究表明,即使有机硅成分产生相对“硬”固化的整体,热应力管理也是可行的;有机硅热熔胶可以实现原料的极端比例,这是典型的可固化液体组合物不可能实现的。在本次演讲中,我们将介绍新的有机硅热熔胶解决方案,以满足新兴的紧急技术要求,如易于处理,热稳定性或抗热应力的可靠性。第一种解决方案是热固化硅胶热熔圆柱片,用于传递成型。其目的是实现类似的处理/性能环氧成型化合物(EMC)片剂具有优越的热稳定性。有机硅热熔胶技术与新型复合技术相结合,使固化件具有极高的硬度和CTE;它提供8 GPa的拉伸模量和低至11 ppm/°C的CTE,可与典型的EMC相媲美。经确认,与PCB板配套的模塑件没有出现翘曲现象,说明模塑体中有匹配的cte。此外,该原型在250°C下暴露1000小时后,机械和粘合性能没有明显退化。结合原型的优化熔融/流动性能,这可以成为需要极端热稳定性的电子密封剂应用的新颖解决方案。第二种解决方案是热固化有机硅热熔膜,用于大面积封装或粘合。大面积成型是电子领域实现更高产量的新兴趋势。在这种应用中使用可固化的液体产品是麻烦的,因为它需要精确控制层厚度的大坝材料。此外,硅树脂与衬底之间的CTE不匹配成为一个严重的问题,因为来自大面积尺寸的相对较大的热应力。另一方面,提供GPa范围内模量的材料(如上述圆柱形片剂材料)不能应用于柔性器件。为了满足这些需求,新型有机硅热熔膜原型已经开发出来。该原型固化单体的拉伸模量为10-100 MPa, CTE为220 ppm/°C。虽然CTE很高,但设计的流变特性使其具有优异的应力松弛能力,可以最大限度地减少模体中的热应力。在8英寸晶圆上成型时没有观察到翘曲。控制固化件的模量,同时具有柔韧性和低表面粘性。对真空复合材料的熔体/流动性能进行了优化,具有良好的空隙填充能力。此外,该原型对各种基材(包括氟基材料和贵金属,如金)表现出优异的粘附能力。这种有机硅热熔膜实现的独特功能有望满足新兴市场对大面积封装或粘合材料的需求。电子产品的总体趋势包括设备的小型化和生产过程的简化。随着设备变得更小更薄,封装剂或粘合剂可能会暴露在更恶劣的条件下,即更高的温度或更强的光。鉴于这些趋势,硅胶变得越来越合适,但由于其低模量和产品形式(液体或糊状),目前常规硅胶产品的使用受到限制。本报告中描述的新技术将打破这些障碍,并打开一扇门,使硅胶在以前从未使用过的应用中得到利用。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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