Ni/Cu电极MLCC烧端工艺的研究

通过对烧端工艺的详细研究,给出了最佳工艺参数:烧端温度为850～880℃,保温10min;用N2/O2混合气,在排胶段保持φ(O2)为300×10–6,在高温烧结段采用φ(O2)为10×10–6;600℃以下的升温速率控制在30～40℃/min,600℃以上的升温速率控制在50～60℃/min。在上述工艺条件下,选用合适的链式连续炉,可以得到端头性能良好的MLCC产品。     

Ni/Cu电极MLCC烧成工艺的研究

通过各项工艺对比实验,研究了烧成工艺参数对成品性能的影响。给出了最佳工艺参数:烧结温度为1280～1300℃,保温2h,用N2/H2/H2O的混合气控制P(O2)为10–8～10–10MPa,回火温度900～1100℃,保温2～5h,回火气氛氧含量(5～50)×10–6;1000℃以上的升降温速率控制在2～4℃/min。在此工艺条件下,选用合适的烧炉,可以得到性能合格的Ni/Cu电极MLCC。     

回焊炉内氧气体积分数对焊接可靠性的影响

SMT(表面贴装技术)回焊炉工作时,炉中氧气体积分数的差异很大,从100×10–6至10000×10–6不等,在已验证氧气体积分数[(O2)]超过4000×10–6会造成产品不良的前提下,针对500×10–6,1000×10–6,3000×10–6以及4000×10–6这四种不同的氧气体积分数,分别对回焊炉焊接的铜片上的锡焊点进行润湿角、EDS分析,对组装印制电路板(PCBA)上的锡焊点进行X射线、推力、通孔填充量等测试。结果显示,(O2)在4000×10–6以下,元件的焊接可靠性并无明显差异。选择(O2)=4000×10–6可降低回焊炉的氮气用量,节约成本。     

MLCC端电极Sn镀层的焊接失效分析

针对多层陶瓷电容器(MLCC)端电极Sn镀层的可焊性失效问题,运用SEM和能谱仪对Sn镀层进行微观结构和成分分析,找出了失效的主要原因,并提出了改进意见。在对MLCC三层端电极中的底层Ag端浆的烧渗过程中,由于烧渗工艺不合理,Ag浆中出现玻璃料物质的溢出,造成电镀Sn时Sn层不连续、不致密,以至MLCC端电极的可焊性变差。通过设计合理的烧渗银温度曲线可较好地解决MLCC端电极Sn镀层的焊接失效问题。     

大容量MLCC的工艺设计

采用四层端电极(Ni/Cu/Ni/Sn)结构设计,底层为Ni,电镀Cu/Ni/Sn的工艺方法,制作了大容量MLCC。研究了四层结构和三层结构(Cu/Ni/Sn)对电容量等基本电性能、可靠性和内应力的影响。结果表明:制作1206规格10μFMLCC,C为9.86～10.46μF、tanδ为(360～390)×10–4、绝缘电阻≥1.5×108Ω、耐电压值为175～205V,四层结构与三层结构电性能相当。可靠性测试中,四层结构抗机械和热冲击能力提高了20%,且有利于瓷体内应力释放。     

影响直流高压MLCC表面放电的因素

通过悬浮内电极排布、加大端头间距、使用自制专用表面整理剂对高压MLCC表面彻底清洁等工艺措施,对高压MLCC表面放电现象有很大改善,并显著提高了其耐电压性能。采用单悬浮电极排布、3.2mm端头间距,并用自制专用表面整理剂处理,制作1808规格、容量100pF、工作电压3000V的NP0特性MLCC产品,在6000V下没有表面放电现象,击穿电压在10000V以上。     

有机实芯电阻器失效机理研究及工艺改进

本文探讨了国产军用有机实芯电阻器经耐焊接热试验和引出端强度试验后阻值漂移失效机理,弄清了失效原因。采取改变引线端头尺寸、控制填料的粒度和均匀性等一系列切实有效的工艺改进措施,提高了产品的性能,使产品的引出端强度和耐焊接热性能迟到了美国军用标准MIL-R-11F的要求。     

电源用MLCC的新型设计

电源用MLCC在出现漏电击穿后会出现烧机的严重后果,针对该问题,介绍一种新型电源用MLCC的设计方法,采用该设计后,MLCC的耐电压与可靠性有一定改善,并且能够有效的规避烧机问题。     

多层陶瓷电容器端电极可靠性的显微研究

多层陶瓷电容器(MLCC)端电极在实际使用过程中,其电性能会随着时间发生不同程度的偏离,可焊性、耐焊接热等可靠性降低.针对多层陶瓷电容器端电极锡镀层在焊接过程中发生焊接失效问题,利用扫描电子显微镜(SEM)分析了正常样品和可焊性变差样品锡镀层的微观结构,并运用X线能谱(EDS)仪对问题样品进行成分分析.其结果表明,可焊性变差样晶端电极表面锡镀层出现了因氧化产生的异常区域,并通过后期的可焊性实验验证了分析结果,找出了端电极焊接失效的原因,并提出应对端电极氧化问题的改进措施.     

BSTO移相器材料结构与温度特性的研究

为了改进BSTO/MgO系铁电移相材料的电学性能,研究了在同等掺杂条件下,调节Ba1–xSrxTiO3中各成分的配比,即改变x的取值对材料结构及温度特性的影响。实验表明:当x=0.45时,BSTO/MgO系统在10kHz下,εr=84.45;tanδ=3.4×10–3;可调率为11.01%(5kV/mm)。3.5GHz下,εr=87.01,tanδ=4×10–3,并具有相对较好的温度稳定性,在–20~+40℃下αεr=–0.482×10–2/℃,可调率温度系数为–0.836×10–2/℃。     

柠檬酸盐对阳极箔形成速度与比电容的影响

为了提高铝电解电容器用高压阳极箔形成速度与比电容,将水合处理后的腐蚀箔在95℃、2 g/L柠檬酸钠去离子水溶液中浸泡5 min,在530 V电压化成时,形成时间缩短约2 min,化成箔比电容由0.556×10–6 F.cm–2提高至0.584×10–6 F.cm–2,阳极氧化铝膜的结构与性能得到改善。     

高纯铝光箔化学成分对直流电侵蚀的影响

以Fe、Si、Cu含量不同的四种铝光箔进行直流电侵蚀对比实验,研究了高纯铝光箔中化学成分对其作为电容器用铝箔侵蚀过程产生的影响。通过对侵蚀样品的SEM表面观察、腐蚀形貌定量分析,对光箔中化学成分与样品效果进行了分析讨论。结果表明,Cu能增强表面蚀孔的产生,Cu含量相对较低的(25×10–6)光箔侵蚀后适用于制作中压铝电解电容器;Cu含量相对较高的[(50～60)×10–6]光箔侵蚀后适用于制作高压铝电解电容器。     

Chemical Amplification of a Triphenylene Molecular Electron Beam Resist

Molecular resists, such as triphenylene derivatives, are small carbon rich molecules, and thus give the potential for higher lithographic resolution and etch durability, and lower line width roughness than traditional polymeric compounds. Their main limitation to date has been poor sensitivity. A new triphenylene derivative molecular resist, with pendant epoxy groups to aid chemically amplified crosslinking, was synthesized and characterized. The sensitivity of the negative tone, pure triphenylene derivative when exposed to an electron beam with energy 20 keV was ～ 6 × 10^–4 C cm^–2, which increased substantially to ～ 1.5 × 10^–5 C cm^–2 after chemical amplification (CA) using a cationic photoinitiator. This was further improved, by the addition of a second triphenylene derivative, to ～ 7 × 10^–6 C cm^–2. The chemically amplified resist demonstrated a high etch durability comparable with the novolac resist SAL 601. Patterns with a minimum feature size of ～ 40 nm were realized in the resist with a 30 keV electron beam.     

废旧锌锰电池制备Cu掺杂Mn-Zn铁氧体

以硝酸溶解废旧碱性锌锰电池所得的溶液为原料,以酒石酸为凝胶剂,采用sol-gel法制备出一系列Cu掺杂Mn-Zn铁氧体(Mn0.6–x/2Zn0.4–x/2CuxFe2O4,x=0.1,0.2,0.3和0.4)。经XRD、VSM测试,结果表明:Cu掺杂不仅没有改变Mn-Zn铁氧体的相结构,而且有利于尖晶石结构的形成;Cu掺杂后Mn-Zn铁氧体的Ms、Mr和Hc的变化趋势,都是先增大后减小,最适宜的掺杂量x为0.1。此时,Ms为2.66×105A/m,Mr为5.73×104A/m,Hc为1.6/π×104A/m。     

A 220 mV robust read-decoupled partial feedback cutting based low-leakage 9T SRAM for Internet of Things (IoT) applications

In this work, a 9T subthreshold SRAM cell is proposed with the reduced leakage power and improved stability against the PVT variations. The proposed cell employs the read decoupling to improve the read stability, and the partial feedback cutting approach to control the leakage power with improved read/write ability. The incorporated stacking effect further improves the leakage power. The simulated leakage power for the proposed cell is 0.61×, 0.49×, 0.80× and 0.55×, while the read static noise margin (RSNM) is 2.5×, 1×, 1.05× and 0.96×, write static noise margin (WSNM) 0 is 1.5×, 1.8×, 1.68× and 1.9× and WSNM 1 is 0.95×, 1.2×, 1.05×, and 1.2× at 0.4 V when compared with the conventional 6T and state of arts (single ended 6T, PPN based 10T and data aware write assist (DAWA) 12T SRAM architectures) respectively. The minimum supply voltage at which this cell can successfully operate is 220 mV. A 4 Kb memory array has also been simulated using proposed cell and it consumes 0.63×, 0.67× and 0.63× less energy than 6T during read, write 1 and write 0 operations respectively for supply voltage of 0.3 V.     

FIR数字滤波在MEMS加速度计中的应用

简要分析了MEMS加速度计应用模型中的噪声来源,介绍了FIR数字低通滤波器的设计方法,并用FPGA实现的FIR滤波器对MEMS加速度计的输出信号进行了实时滤波处理。通过对滤波前后时、频域信号的比较,可以看出采用FIR数字低通滤波器能有效抑制加速度计输出信号中的高频噪声、提高加速度计的测量精度。实验结果表明,滤波前噪声信号标准偏差为1.53×10-5V,经FIR数字低通滤波后的噪声信号标准偏差降低为5.4×10-6V,加速度计的分辨率由126μg提高到42μg。     

Sn-0.3Ag-0.7Cu-xBi低银无铅钎料的润湿性

以Bi为添加剂对低银型Sn-0.3Ag-0.7Cu无铅钎料进行改性,应用SAT—5100型润湿平衡仪对Sn-0.3Ag-0.7Cu-xBi(x=0,1,3和4.5)钎料的润湿性能作了对比分析。结果表明:适量Bi元素的加入可以改善Sn-0.3Ag-0.7Cu钎料合金的润湿性能,且在240℃下Sn-0.3Ag-0.7Cu-3.0Bi无铅钎料具有最佳的润湿性能,在250℃其润湿力达到最大值3.2×10–3N/cm。     

Temperature and current-density distributions in flip-chip solder joints with Cu traces

Three-dimensional simulation was performed to investigate the temperature and current density distribution in flip-chip solder joints with Cu traces during current stressing. It was found that the Cu traces can reduce the Joule heating effect significantly at high stressing currents. When the solder joints were stressed by 0.6 A, the average temperature increases in solder bumps with the Al traces was 26.7°C, and it was deceased to 18.7°C for the solder joint with the Cu traces. Hot spots exist in the solder near the entrance points of the Al or Cu traces. The temperature increases in the hot spot were 29.3°C and 20.6°C, for solder joints with the Al traces and Cu traces, respectively. As for current density distribution, the maximum current density inside the solder decreased slightly from 1.66×10⁵ A/cm² to 1.46×10⁵ A/cm² when the Al traces were replaced by the Cu traces. The solder joints with the Cu traces exhibited lower Joule heating and current crowding effects than those with the Al traces, which was mainly attributed to the lower electrical conductivity of the Cu traces. Therefore, the solder joints with the Cu traces are expected to have better electromigration resistance.