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51.
无铅化电子组装中无铅焊料的高熔点、低润湿性给实际生产带来了很大挑战。为了改善润湿性,可适当提高焊接温度,但由于PCB及元件的工艺温度限制,导致了焊接工艺温度窗口变窄。氮气保护可以改善无铅焊料润湿性、防止氧化、提高焊接品质,更重要的是可以降低焊接峰值温度,扩大焊接工艺温度窗口。 相似文献
52.
《Ceramics International》2023,49(19):31152-31162
There is still a problem of low energy storage density in dielectric capacitors which is a core component of power systems. For the improvement of the energy storage density, the linear dielectric material CaTiO3 (CT) was introduced in Na0.5Bi0.5TiO3 (NBT) ceramics in this paper. By modifying the A site, a new relaxor ferroelectric ceramic was successfully synthesized and attained a recoverable density (Wrec) of 2.34 J/cm3 at x = 0.18. Moreover, the preparation process was optimized in this paper. Through the viscous polymer process (VPP) route, the energy density (WA) of 82NBT-18CTVPP ceramic further reaches 6.45 J/cm3 at 340 kV/cm, with efficiency (η) up to 75% and a Wrec of 4.82 J/cm3. At the same time, the change of Wrec is small at temperature (30–150 °C) and frequency (1 Hz–300 Hz), which demonstrates its excellent stability. The discharge power density reaches about 180 MW/cm3 and the discharge time is 0.117 μs, which indicates its excellent pulse discharge performance. The results show that 82NBT-18CT lead-free relaxation ferroelectric material is expected to become ideal for high-energy storage applications. 相似文献
53.
The influence of the Bi content on the fillet-lifting phenomenon in Sn-3Ag-Bi alloys was investigated. The peculiar composition
dependence on the fillet-lifting exists in Sn-3Ag-xBi alloys. With fillet-lifting, they are 3–20%Bi. Without fillet-lifting,
they are 0–1%Bi, 30%Bi, and above. This is related to the alloy solidification characteristics, in particular, the amount
of latent heat release near the final solidification temperature (solidus temperature) during solidification. Fillet-lifting
is likely to occur in the alloy with a latent heat released which is insufficient for alleviation of the temperature gradient
in the solder joint. A new predictable index for the occurrence of fillet-lifting is proposed as the fillet-lifting resistant
index (FRI) that correlates well with the fillet-lifting occurrence rate. The fillet-lifting does not occur when a solder
alloy has a FRI of 0.75 and above. The magnitude of the solidification temperature range (T) does not necessarily correlate
with the fillet-lifting, because there are some alloys without fillet-lifting in spite of their having a wide T. There is
also little correlation between the fillet-lifting and the formation of a Bi concentration at the solder/Cu land interface,
previously thought to cause fillet-lifting. The Bi concentration at the solder/Cu land interface may occur as a consequence
of the Sn consumption by the intermetallic compound formation with the Cu dissolving into the molten solder and existing at
the interface rather than the solidification segregation. 相似文献
54.
The effect of triethanolamine (TEA) and heliotropin (HT) on the cathodic polarization of weakly acidic baths and the properties of Sn-Ag-Cu alloy electrodeposits were investigated. Lead-free Sn-Ag-Cu solder alloy were electrodeposited in weakly acidic baths (pH 5.5) containing Sn(CH3SO3)2, AgI, Cu(CH3SO3)2, K4P2O7, KI, hydroquinone, TEA, HT and methylsulfonic acid (MSA). The cathodic polarization of baths and the properties of electrodeposits were evaluated by Liner sweep voltammetry (LSV), scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results indicate that HT is a main brightening agent that increases the cathodic polarization of baths and refines the grains of electrodeposits; TEA is a complexing agent for copper ions and a brightening promoter that decreases the cathodic polarization of baths and densifies the electrodeposits. The bright, compact, and smooth Sn-Ag-Cu alloy electrodeposits contain 88-95 wt% tin, 5-10 wt% silver and 0.5-2 wt% copper. Organic compounds used in the baths neither adsorb on the electrodeposits surfaces nor are included in the electrodeposits. It can be therefore concluded that the use of both TEA and HT is better than that of them either in the process of electroplating bright Sn-Ag-Cu alloy. 相似文献
55.
Low-cycle fatigue (LCF) behavior of a lead-free Sn-3.5Ag-0.5Cu solder alloy was investigated at various combinations of strain
ratio (R = −1, 0, and 0.5) and tensile hold time (0, 10, and 100 sec). Results showed that the LCF life of the given solder,
at each given combination of testing conditions, could be individually described by a Coffin-Manson relationship. An increase
of strain ratio from R=−1 to 0 and to 0.5 would cause a significant reduction of LCF life due to a mean strain effect instead
of mean stress effect. LCF life was also markedly reduced when the hold time at tensile peak strain was increased from 0 to
100 sec, as a result of additional creep damage generated during LCF loading. With consideration of the effects of strain
ratio and tensile hold time, a unified LCF lifetime model was proposed and did an excellent job in describing the LCF lives
for all given testing conditions. 相似文献
56.
Effect of rare earth element addition on the microstructure of Sn-Ag-Cu solder joint 总被引:6,自引:0,他引:6
Bo Li Yaowu Shi Yongping Lei Fu Guo Zhidong Xia Bin Zong 《Journal of Electronic Materials》2005,34(3):217-224
The effects of minimal rare earth (RE) element additions on the microstructure of Sn-Ag-Cu solder joint, especially the intermetallic
compounds (IMCs), were investigated. The range of RE content in Sn-Ag-Cu alloys varied from 0 wt.% to 0.25 wt.%. Experimental
results showed that IMCs could be dramatically repressed with the appropriate addition of RE, resulting in a fine microstructure.
However, there existed an effective range for the RE addition. The best RE content was found to be 0.1 wt.% in the current
study. In addition to the typical morphology of Ag3Sn and Cu6Sn5 IMCs, other types of IMCs that have irregular morphology and uncertain constituents were also observed. The IMCs with large
plate shape mainly contained Ag and Sn, but the content of Ag was much lower than that of Ag3Sn. The cross sections of Cu6Sn5 IMCs whiskers showed various morphologies. Furthermore, some eutectic-like structures, including lamellar-, rod-, and needle-like
phases, were observed. The morphology of eutectic-like structure was related to the RE content in solder alloys. When the
content of RE is 0.1 wt.%, the needle-like phase was dominant, while the lamellar structure prevailed when the RE content
was 0.05 wt.% or 0.25 wt.%. It is suggested that the morphology change of the eutectic-like structure directly affects the
creep properties of the solder joint. 相似文献
57.
Encapsulation of lead-free Sn/Zn/Bi solder alloy particles by coating with wax powder for improving oxidation resistance 总被引:2,自引:0,他引:2
Tomohiro Iwasaki Jeong Hwan Kim Shohei Mizuhashi Munetake Satoh 《Journal of Electronic Materials》2005,34(5):647-654
An encapsulation treatment of lead-free Sn/Zn/Bi solder powder was investigated for improving the oxidation resistance. Sn-8mass%Zn-3mass%Bi
alloy particles were coated with a wax (12-hydroxystearic acid) powder by means of a dry mechanical treatment method using
a ball mill. In order to determine the optimum operating conditions of the ball mill in the wax-coating treatments, the compressive
energy required for deforming a single Sn/Zn/Bi alloy particle was measured with an unconfined compression tester and the
mechanical energy applied to the alloy particles in the ball mill was estimated using the results of the compression test.
The optimum operating conditions were determined based on both the applied energy and the flowability of solder pastes, and
the wax-coated alloy particles maintaining the spherical shape were obtained under the conditions. The wettability test and
the solder balling test for the solder pastes containing the wax-coated alloy particles stored at room temperature in air
were carried out to evaluate the oxidation resistance performance. The wax-coated alloy particles had an excellent wettability
compared with the original alloy particles, and the oxidation resistance of the Sn/Zn/Bi solder powder was improved by the
encapsulation treatment. 相似文献
58.
Minna Arra Dongkai Shangguan Erro Ristolainen Toivo Lepistö 《Journal of Electronic Materials》2002,31(11):1130-1138
Solder balling in Sn/Ag/Cu solder pastes was studied in this work. Three different solder pastes, several different reflow
profiles and conditions, and two stencil thicknesses were used in the investigation. During the first phase, called the verification
phase, the solder pastes were checked to ensure they met the minimum requirements. In the process-screening phase, the reflow
profile was varied. Results show that besides flux chemistry, reflow atmosphere plays the major role in solder balling. The
average number of solder balls with the best paste was one fifth of that with the worst paste. Furthermore, with all the pastes,
the number of solder balls dropped close to zero when nitrogen atmosphere was used. Another finding during the reflow process
screening was the influence of the stencil thickness on the solder-balling result. With a thinner stencil, two of the pastes
exhibited significant solder balling. This is assumed to be caused by the different ability of fluxes to withstand oxidation
during the preheating in the reflow process. In the last phase, the effect of the solder-paste particle size on solder balling
was studied more closely. The flux chemistry was kept unchanged, and the solder particle size was varied between type 3 and
type 4. The results show that, with type 4 paste, significantly more solder balls are formed compared to type 3 paste. It
was also confirmed that, regarding the reflow profile, the ramp-up rate from 150°C to 217°C and the reflow atmosphere were
the most significant factors that determine the solder-ball formation for both types of paste. 相似文献
59.
无铅波峰焊接工艺是常见组装焊接工艺之一,其中焊接空洞是较严重的问题。焊接空洞的存在是电子学产品的潜在隐患,影响产线补板效率,增加生产成本。以实际生产过程中混装电路板过波峰焊时遇到的通孔焊接空洞现象进行分析,主要从印制板制程工艺与波峰焊工艺参数这两方面提出解决方案。 相似文献
60.
介绍了SMT技术,并重点介绍了铝电解电容器SMT无铅工艺技术.为满足欧盟关于电子电气设备中限制使用某些有害物质和报废指令(即WEEE和ROHS指令),通过一个案例分析了铝电解电容在无铅生产中遇到的问题和解决办法. 相似文献