基于改性环氧树脂各向异性导电胶的研究

STUDY ON ANISIOTROPIC CONDUCTIVE ADHSIVE BASED ON MODIFIED EXPOXY RESIN

薛伟

11849284

硕士

材料工程领域工程

田颜清

2020-05-29

2020-07-20

哈尔滨工业大学

深圳

随着电子器件越来越小型化、高精密化和高性能化，传统的锡焊焊接技术已无法满足微电子封装的要求。各向异性导电胶作为新型电子封装粘接材料应时而生。与传统的锡焊材料相比，各向异性导电胶有着环境友好、粘接间距小、操作工艺简单和加工温度低等不可替代的优势。但目前市售的各向异性导电胶仍存在诸多问题，如：无法长期稳定存储、环氧树脂耐冲击性差、以及高温或高湿环境下的长期稳定性差。因此高性能各向异性导电胶的研制对电子封装技术乃至整个电子器件行业的发展至关重要。基于上述存在的问题，本论文对目前的各向异性导电胶进行了改进，以得到力学性能和导电性均良好的各向异性导电胶。主要研究内容有：（1）对环氧树脂的韧性改进以增加其力学性能：环氧树脂作为各向异性导电胶主要的粘接基体一般表现出较脆的性质和较低的韧性。两亲性嵌段共聚物能在环氧树脂基体中自组装成不同形貌的微结构，这些微结构能在环氧树脂受到冲击和外力作用时吸收能量从而达到增加环氧树脂韧性的目的。本文通过用不同长度的聚乙二醇单甲醚(PEO，Mw = 200, 500, 1000，2000, 4000)与端羧基丁腈橡胶(CTBN)接枝，然后用于改性环氧树脂。研究发现 PEO 分子量大于500 时嵌段共聚物才能在环氧树脂中有效地自组装；PEO 分子量在 2000 时，对环氧树脂的增韧效果最佳。PEO-b-CTBN 虽然可以增加环氧树脂的韧性，但CTBN 大幅降低环氧树脂的粘接性能，无法应用于导电胶改性。因此选用分子量为 4000 的聚乙二醇制备出 PS-b-PEO-b-PS 三嵌段高分子，这样高分子里分配到每个 PS 链上的 PEO 为 2000；之后选用分子量为 2000 的聚乙二醇单甲醚通过自由基活性聚合制备出 PEO-b-PS-b-PMMA 三嵌段高分子。用它们对环氧树脂进行改性，从断裂韧性结果来看它们对环氧树脂都有较好的增韧效果。（2）改变导电粒子的粒径以增加其导电性和粘接性：导电粒子是 ACF 的核心材料,导电粒子的粒径不但影响 ACF 的导电性能，还会影响 ACF 的粘接性。我们通过一步法和种子溶胀法合成出不同粒径的聚合物微球，通过化学镀的方法在聚合物微球表面镀镍。用不同粒径的导电粒子分别制成各向异性导电胶，测试对应的 ACF 的导电性和粘接性。研究表明导电粒子过大、过小都无法成为综合性能优异的 ACF。通过研究发现导电粒子粒径为 5 m 时，ACF 的 多项性能表现优异。

Electronic packaging technology has become more and mor e essential in electronic device industry. Isotropic conductive adhesives (ICA) and anisotropic conductive adhesives (ACA or ACF if the ACAs are in the format of films) play important roles in electronic packaging technology. For ACAs, currently there are still many problems to be solved, such as: long-term stablility in storage, limited impact resistance of epoxy resins, and poor stability under high temperature or high humidity environments. This dissertation studied the epoxy resins and conductive particles to improve the performance of ACAs.This dissertation will include the following contents: (1) The improvement of the toughness of epoxy resins: The most important bonding matrix of epoxy resin as ACA is relatively brittle with low toughness. Amphiphilic block copolymers can self-assemble into different morphologies in the epoxy matrix with microstructures. These microstructures can absorb energy when the epoxy resin is impacted to result in the increase of toughness of the epoxy resins. By grafting polyethylene glycol (PEO) blocks with different lengths onto carboxyl-terminated nitrile rubber (CTBN), new block copolymers of PEO-b-CTBNs were obtained. It was found that the self-assembly effect of these block copolymers in epoxy resins can only be achieved when the molecular weight of PEO is greater than 500. Block copolymers of PEO-b-PS-b PMMA and PS-b-PEO-b-PS were prepared by using a PEO with a molecular weight of 2000. These block copolymers were used to improve the toughness of epoxy resins and to achieve good results.(2) Improvement of the synthesis of conductive particles: The conductive particles are critical for the conductive adhesives, since they not only affect the conductive properties, but also affects the adhesiveness. Polymer microspheres with different particle sizes were synthesized by one-step method and seed method. And the surfaces of the polymer microspheres were plated with Ni by electroless plating. ACAs were prepared by using conductive particles with different diameters, and their corresponding conductivities and adhesion properties were tested. Studies have shown that conductive particles that are too large or too small are not suitable for achieving excellent performance of ACAS. The optimized diameters of the conductive particles are about 5 m.

各向异性导电胶 两亲性嵌段共聚物 环氧树脂 导电微球

anisotropic conductive adhesives amphiphilic block copolymers epoxy resins polymer microspheres

中文

联合培养

南方科技大学

薛伟. 基于改性环氧树脂各向异性导电胶的研究[D]. 深圳. 哈尔滨工业大学,2020.