【作者】 王丽；

【导师】 吴铭方； 王凤江；

【作者基本信息】 江苏科技大学 ， 材料工程， 2015， 硕士

【摘要】 SnAgCu305(SAC305)无铅钎料由于具有良好的润湿性、可焊性、物理及机械性能等,现在被广泛使用于电子制造行业以代替传统的Sn-Pb焊料,但是,国内无铅锡膏的性能及研发要远远落后于国外同类产品。同时,随着电子产品向小型化发展,焊点的尺寸逐渐减小,这就导致由跌落、振动引起的可靠性问题逐渐被提上了日程。然而,SAC305焊膏的抗跌落、振动可靠性并不是特别突出,同样需要开发具有更高可靠性的无铅焊膏。本论文通过优化助焊剂配方来制得性能较好的助焊剂,与合金粉按一定比例制成焊膏,并通过添加微量合金元素以提高产品的性能。本论文用旋转流变仪对焊膏进行粘度、触变系数测试,用ATV共晶回流炉对BGA焊点进行真空和空气条件下的焊接,用PTR-1102微焊点强度测试仪对焊点进行剪切性能测试,用金相显微镜观察焊点显微组织,用扫描电子显微镜对焊点微观组织以及断口形貌进行观察。本论文得到的主要结论如下:(1)助焊剂配方:成膜剂由30wt.%日本荒川KE604和15wt.%DMER-145二聚松香复配组成;触变剂由5wt.%氢化蓖麻油和5wt.%乙撑双硬脂酸酰胺(EBS)组成;根据TGA测试结果及抗冷坍塌性能为依据,选用溶剂成分为18wt.%己醚、10wt.%丁醚和10wt.%戊二醇;以TGA测试结果、溶解性、铺展面积、和腐蚀性为依据,选择1.6wt.%己二酸、1.4wt.%丁二酸和2wt.%戊二酸三种有机酸复配,再以PH值和残留率确定二乙醇胺的加入量为1wt.%;缓蚀剂的总量为0.8wt.%,8-羟基喹啉和苯并三氮唑质量比为1:1复配;抗氧化剂选用0.1wt.%的对苯二酚,除臭剂选用0.1wt.%的薄荷;(2)研制出的助焊剂为奶黄色的流动性较好的粘稠膏体,稳定性较好,PH值介于5.5与6.0之间,接近6.0,不含卤素,腐蚀性较小,不挥发物含量为34.79%。与国外同类焊膏对比,所研制的焊膏都具有合适的粘度、触变系数和抗冷热坍塌性,可以满足细间距印刷,同时焊料球测试合格;(3)为了提高焊膏的抗跌落性能,在SAC体系内加入微量合金元素Zn并制作成焊膏。自制的SAC305焊膏、加Zn的自制焊膏和成熟的商用焊膏相比,三者的铺展率分别为88.20%、86.30%和89.80%,均具有良好润湿性。金相和SEM显示,加入Zn之后,金属间化合物(IMC)层厚度小且生长较规律,IMC颗粒变小。剪切实验说明,真空条件下回流比空气中回流得到的焊点强度大,且加入Zn之后,剪切强度增强,这些和焊点的组织紧密相连,焊点的断裂模式都为韧性断裂。更多还原

【Abstract】 Sn-3.0Ag-0.5Cu Pb-free solder(SAC305) has been widely used to replace toxic Sn-37 Pb solder in electronic industry due to its better wettability, solderability, physical and mechanical properties than other Pb-free solders, but the properties and development on domestic Pb-free solder paste is now unacceptable to use. On the other hand, with the minimize size on electronic products, the size on solder joint is also smaller, which makes a more important reliability on the drop and vibration performances of SAC305. In this thesis, we developed a new solder paste for SAC305 by mixing the soldering flux with optimized compositions and SAC305 solder alloy powder without or with minor Zn addition. The viscosity and thixotropic properties of solder paste was tested with rotary thermometer. The reflow soldering of solder paste was finished in ATV eutectic reflowing oven under air or vacuum condition. The shear strength on solder joints was tested with PTR-1103 shear tester. The microstructure and fracture surface were observed with optical microscope and JSM6480 scanning electronic microscope(SEM). The main collusions are listed as flowing:(1)An optimized composition on soldering flux was finished. It includes the film former comprising 30 wt.% ARAKAWA KE-604 rosin and 15 wt.% dimerized rosin DMER-145, the thixotropic agent comprising 5wt.% Hydrogenated castor oil(HCO) and 5wt.% Ethylene bis(EBS), the solvent decided with TGA results comprising of 18 wt.% Hexyl ether, 10 wt.% buthyl ether and 10 wt.% pentanediol, the activators decided from their solubility, wettability and corrosion resistance comprising organic acids mixed with 1.6wt.% adipic acid, 1.4wt.% succinic acid and 2wt.% glutaric acid, and further comprising an amine selected as 1wt.% diethanolamine, the corrosion resistor comprising 0.4wt.% 1,2,3- Benzotriazole and 0.4wt.% 8-Hydroxyquinoline, the anti-oxidation agent with 0.1wt.% Hydroquinone and finally the deodorant with 0.1wt.% menthol.(2)The above no-clean soldering flux shows very good dispensability, solderability and wetting characteristic, also it showed very good paste stability. The PH is about 5.5 to 6.0. The content of un-evaporated substances in the flux is about 34.79%. Compared with international famous products, it provides an acceptable viscosity, thixotropic characteristic, slump testing results and solder ball testing.(3)To improve the drop reliability of solder paste, minor Zn was added into SAC to get the Zn-contained solder paste. Compared with the above vehicle and international famous product, their spreadability is 88.2%, 86.3% and 89.8%, respectively. The wettability of Zn-contained solder paste was not affected with the Zn addition. Optical and SEM microstructure showed that the thickness of intermetallic compound(IMC) at the interface in the solder joint was decreased, and the shear strength was increased with the Zn addition. The fracture mode was ductile crack.更多还原