助焊剂和镶嵌温度对嵌入式NbTi超导线材表面及性能的影响

Effect of flux and soldering temperature on the surface morphology and properties of WIC NbTi superconducting wire

摘要:

嵌入式NbTi超导线是将小铜超比的NbTi/Cu超导线材经过去油和助焊后,在高温锡液中嵌入U型铜槽中,从而获得大铜超比的NbTi/Cu超导线材。研究了超声波去油温度和乳化剂浓度对对超声波清洗后U型铜槽线表面质量的影响。研究表明,温度为50℃、乳化剂浓度为5%的去油溶液可有效去除U型铜槽线表面的油污和灰尘；进一步研究了不同浓度的前处理助焊剂“氯化亚锡+硝酸+异丙醇”对助焊后U型铜槽线表面状态的影响。研究表明,硝酸助焊后,表面粗糙度很差；氯化亚锡助焊后铜槽线表面粗糙度极低,无法进行热镀锡；而“300g/L氯化亚锡+15%硝酸+3%异丙醇”助焊清洗工艺配方的助焊效果最好。在优化出去油和助焊清洗工艺参数基础之上,采用不同锡液温度(360~500)℃进行镶嵌实验,并采用目测和扫描电镜来表征镶嵌线材表面质量。实验结果表明,锡液温度过低,线材表面镀锡不均匀,呈淡红色；锡液温度过高,线材表面易产生锡瘤；当锡液温度范围为(400~440)℃时,线材表面质量较好,无锡瘤、黑点、毛刺、露铜等表面缺陷,同时可以满足线材结合力和剩余电阻比的性能要求。

Abstract:

Wire in channel (WIC) NbTi superconducting wire is to let NbTi core wire with small copper ratio embedded into a u-shaped copper channel in high-temperature Tin bath, so as to obtain a NbTi/Cu superconducting wire with a large copper ratio. Results show that emulsifier with the temperature of 50 ℃ and the concentration of 5% can effectively remove the oil and dirt on the surface of Cu channel; Furthermore, the effects of different concentrations of flux "stannous chloride + nitric acid + isopropyl alcohol" on the surface state of core wire and Cu channel. Results show that the surface roughness is very poor after nitric acid fluxing; The surface roughness of the Cu channel is very low after SnCl₂ fluxing, which is very bad to Tinning coating. And "300g/L stannous chloride +15% nitric acid +3% isopropyl alcohol" flux has the best welding effect. Based on the degreasing experiment and fluxing experiment, soldering experiments under different temperature (360 ~ 500 ℃) were conducted. Results show that the surface of wire is not uniform and reveals pink when the soldering temperature is low. When the temperature is too high, the surface of wire is easy to produce tin-lump. When the soldering temperature is ranging from 400 to 440 ℃, wire surface quality is good, without any tin-lump, black spots, burrs, and other surface defects. At the same time, wire bonding force between core wire and Cu channel and residual resistance ratio. can meet the requirements.