ICP-AES测定镍基焊料中的磷

通过酸溶解试验、基体共存元素干扰实验等,建立了ICP-AES测定镍基焊料中高含量磷的分析方法.样品加标回收率为100.5%-101.0%,相对标准偏差小于0.80%.该方法简便、快速、准确可靠.     

Rheological characterization of a solder paste for surface mount applications

Solder pastes used in surface mount soldering techniques (SMT) are very complex suspensions containing high volumes of metallic powder in a carrier fluid. The rheological complexity results largely from the carrier fluid itself, which is a suspension of colloidal particles. In this work, we have characterized the rheological properties of a typical carrier fluid and its solder paste containing 64 vol.% metallic powder. A six-blade vane geometry was used to avoid wall slip and sample fracture. All measurements were carried out following pre-shearing and rest time in order to obtain reproducible results. Steady shear experiments showed that the solder paste was highly shear-thinning and thixotropic. In oscillatory shear, the linear viscoelastic domain was found to be very narrow for both the suspending fluid and the paste. Frequency sweep tests in the linear domain revealed a gel-like structure with a nearly constant G′ for the suspending fluid and a slightly increasing G′ for the solder paste. From creep experiments, a yield stress of about 40 Pa was determined for the suspending fluid at temperatures between 25 and 40°C, and of 100 Pa at 4°C. A much larger yield stress, 480 Pa, was determined for the solder paste at 25°C.     

高温超导无绝缘线圈励磁电压特性研究

本文通过实验研究了焊锡浸渍、励磁电流PI控制、励磁速率以及励磁幅值对高温超导无绝缘线圈励磁电压特性的影响。实验结果表明:高温超导无绝缘线圈励磁电压具有时延特性,焊锡浸渍、励磁电流PI控制分别会增大和减小时延特性,而励磁速率和励磁幅值不会影响时延特性;励磁电压幅值随励磁速率增大而增大;焊锡浸渍可降低励磁电压幅值,而励磁电流控制对励磁电压幅值影响不明显。     

Detection of micro solder balls using active thermography and probabilistic neural network

Micro solder ball/bump has been widely used in electronic packaging. It has been challenging to inspect these structures as the solder balls/bumps are often embedded between the component and substrates, especially in flip-chip packaging. In this paper, a detection method for micro solder ball/bump based on the active thermography and the probabilistic neural network is investigated. A VH680 infrared imager is used to capture the thermal image of the test vehicle, SFA10 packages. The temperature curves are processed using moving average technique to remove the peak noise. And the principal component analysis (PCA) is adopted to reconstruct the thermal images. The missed solder balls can be recognized explicitly in the second principal component image. Probabilistic neural network (PNN) is then established to identify the defective bump intelligently. The hot spots corresponding to the solder balls are segmented from the PCA reconstructed image, and statistic parameters are calculated. To characterize the thermal properties of solder bump quantitatively, three representative features are selected and used as the input vector in PNN clustering. The results show that the actual outputs and the expected outputs are consistent in identification of the missed solder balls, and all the bumps were recognized accurately, which demonstrates the viability of the PNN in effective defect inspection in high-density microelectronic packaging.     

Defects inspection of the solder bumps using self reference technology in active thermography

With the decrease of solder bumps in dimension and pitch, defects inspection of the solder bumps become more difficult. A nondestructive detection system based on the active thermography has been developed for solder bumps inspection. However, heating non-uniformities and emissivity differences may impede the defects recognition. In this paper, we propose a method using a self reference technology based on a source distribution image (SDI) to eliminate the influence of unevenness in emissivity values and heating power distribution. Three thermograms captured right after the heat pulse are averaged to create the SDI. Then the SDI is subtracted from the original thermograms, and we get the thermal contrast images, in which eight points on the edge of each hot spot are selected as the feature points for the corresponding bump. Thermal difference between the feature points and the central point are adopted to quantify the thermal behaviors of the solder bumps, by which the missing bump is distinguished from the reference bumps. The results show that it is effective using the method to eliminate the impacts of emissivity unevenness and heating non-uniformities on defects identification in the active infrared test.     

YBCO带材低熔点焊接接头研究进展

以YBa_(2)Cu_(3)O_(7)(YBCO)带材为代表的二代高温超导带材被广泛应用于各类超导装备中,由于YBCO超导带材生产长度的限制,其接头技术将在带材的实用化发展中起到至关重要的作用,其中低熔点焊料焊接接头技术由于其工艺简单且能够满足目前二代高温超导材料的应用需求,成为现阶段接头制备的主流技术.本文基于YBCO基本属性,结合目前国内外的YBCO带材生产现状,系统全面地调研了低熔点焊料焊接接头技术的制作工艺及其性能的影响因素,明确了低熔点焊料焊接接头的关键影响因素,梳理了二代高温超导带材接头的焊接工艺流程,为二代高温超导带材接头的制备提供参考。     

Solder with discontinuous melting point in semiconductor laser arrays and stacks

High power semiconductor laser arrays must be mounted in the epitaxy-side down configuration for good heat transfer and so require a well-controlled solder. Selection of solder is very important in semiconductor laser arrays and stacks. Usually, the solder consists of two layers. The outer layer prevents In from oxidation. A new type of solder with several layers of Au between the two layers of In was made, which constitutes of multi-layer of W/Ni/Au/In/Cu. In packaging, the Au layer in the solder does not melt. Quick temperature decrease can avoid expansion of the solder. The solder cannot oxidize during packaging.     

The rheological properties of solder and solar pastes and the effect on stencil printing

Solar and solder pastes are widely used in the electronics industry. Solder paste is the principal joining medium in the assembly of surface mount components, whilst solar paste is used in the manufacture of semiconductor solar cells in the photo-voltaic industry. The stencil printing of both solder and solar pastes is a very important and critical stage in the assembly process. With miniaturisation of components, this is likely to continue. The challenge in stencil printing at such dimensions is in achieving repeatable deposition of both solar and solder pastes from print to print. To meet this challenge requires an understanding of the flow behaviour of both solar and solder pastes. The rheological properties of solar and solder pastes have been evaluated through three different types of experiments. Existing models were applied to compare their rheological behaviour under these schemes. One striking difference was that solar paste showed a higher viscosity than solder paste. Both solar and solder pastes were found to be non-Newtonian materials, showing a decrease in viscosity with increasing shear rates. In this paper we investigate the rheological properties of both solder and solar paste under steady shear and creep-recovery tests. Received: 12 October 1999 Accepted: 11 July 2000     

不同前处理方法测定银锡焊料中3种重金属元素

选用银含量为3%、30%和70%的银锡焊料样品,分别经过三种不同前处理方法,采用硝酸、盐酸消解,应用电感耦合等离子体发射光谱法(ICP-OES)同时测定锡铅合金中镉、铅、汞3种重金属元素含量。实验研究了不同前处理方法对银锡合金中重金属测定的影响。实验表明消解实验中的共沉淀现象会对3种重金属元素的测定产生不利的影响,回收率不能满足要求;采用硝酸消解,过滤残渣经王水消解的方法,镉、铅、汞的7次测定重复性相对标准偏差在2.7%~5.5%、加标回收率在85.6%~103%,能够满足RoHS测试要求。     

Effects of micro-additions on structures and properties of rapidly solidified Sn-10% Sb alloy

Structure, electrical resistivity, hardness, internal friction and elastic modulus of Sn-10% Sb and Sn₈₉Sb₁₀M₁ (M₁ = Ag, Cu, Zn and Pb) alloys have been investigated. No obvious change on the electrical resistivity value was found at 293 °K of a Sn-10% Sb alloy by adding Zn and Cu, but extreme changes occurred after adding Ag and Pb. The elastic modulus, internal friction, hardness and thermal diffusivity values are greatly affected by adding the micro-additions to a Sn-10% Sb rapidly solidified alloy. It is also interesting to note that Ledbetter's theoretical values of μ/E are in good agreement with the experimental results. The rapidly solidified alloys Sn₉₀Sb₁₀ and Sn₈₉Sb₁₀Ag₁ have good properties as toxic-free lead solder alloys for high-temperature applications and good mechanical properties such as under the hood in the automobile and avionics systems. Also, the rapidly solidified alloys Sn₈₉Sb₁₀Zn₁, Sn₈₉Sb₁₀Cu₁ and Sn₈₉Sb₁₀Pb₁ have good properties as bearing materials.