SMT Solder Joints Research Articles

PADS: Predictive Anomaly Detection for SMT Solder Joints Using Novel Features From SPI and Pre-AOI Data

PADS: Predictive Anomaly Detection for SMT Solder Joints Using Novel Features From SPI and Pre-AOI Data

Study on the Conversion Method of Three-Dimensional Shape Prediction Model of BGA Solder Joints

In the study of three-dimensional shape prediction of SMT solder joints, the software Surface Evolver has been widely applied as a quick and accurate effective tool for the prediction of solder joints shape. But the model it builds is not able to be directly imported into any finite element analysis software like ANSYS, and even after the import it still needs a lot of time to mend the import model. For this issue, to predict of the solder joints shape of ball grid array (BGA), the implement programs of three conversion methods of point-line-area method, axisymmetric method and infinitesimal method are given. By comparison, axisymmetric method and infinitesimal method are more suitable for the shape conversion of BGA solder joints.

Fatigue of SMT solder joint including torsional curvature and chip location optimization

The objective is to find whether fatigue of the solder joint or the location of the chip is related to the curvature and torsional curvature when SMT solder joints are under vibration or shock condition. However, the torsional curvature is always omitted. In this paper the relationship of curvature and torsional curvature is argued, and it is found that the quantity of the curvature is closer to that of the torsional curvature and shows that omitting the torsional curvature is not accurate. Also, the fatigue of the solder joint including torsional curvature is obtained. One kind of SMT printed circuit board (PCB) used in aviation and spaceflight has been obtained to test its modes. According to the modal results, the location of the SMT assembly is not very suitable and the reliability of SMT solder joints will decrease, which will make an unreasonable catastrophe appear. Meanwhile, the location optimization including curvature and torsional curvature is considered and four areas are obtained in the PCB to locate the chip for increasing the fatigue of solder joints. In this paper the results obtained by assuming the PCB is simply supported in its four boundary. The other fixed condition will be calculated using a similar method.

Astronautic PBGA (plastic ball grid array) solder joints’ reliability: under successive-high acceleration shock condition

Along with the development of the astronautic industry, more and more SMT solder joints have been used in missile, rocket and other important equipments where the environment of astronautic equipments is more serious and complex than that in normal conditions. In this present paper, reliability of a kind of astronautic PBGA256 assembly sample is considered under the successive-high acceleration shock condition. During the test, the thickness of InterMetal Compounds (IMCs) is considered and calculated by an equation to compare with each other. It is found that the growth rate of the phase of Cu6Sn5/Cu3Sn and Ag3Sn is larger that other phases. So in the finial micrographs the phase of Cu6Sn5/Cu3Sn and Ag3Sn is easy to observed. After 3 hours’ successive-high acceleration (7g) shock, although the sample PBGA solder joints are still in good condition and have no obvious crack by SEM, in the micrograph of the solder joint there are some special phenomena that is not the same as that in normal condition or thermal fatigue load.

Low cost scaleable parallel image processing system

The design and application of a DSP-based Parallel Image Processing system is presented. A scaleable system based around a TMS320C40 DSP Master–Slave architecture is shown to be a suitable vehicle for industrial inspection problems. Custom vision bus and parallel communication channels are used to pass data between local and shared memory in the image processing system. The target application of SMT solder bond inspection required the fast processing of 2-D FFTs. Analysis of the system's suitability to this task is presented followed by actual results from a three-processor system. The target inspection rate of 100 SMT solder joints per second can be met.

K-0318 三次元境界要素法によるSMTはんだ接合体平衡形状決定の基礎的研究(S02-3 境界要素法とその周辺技術(3))(S02 境界要素法とその周辺技術)

K-0318 三次元境界要素法によるSMTはんだ接合体平衡形状決定の基礎的研究(S02-3 境界要素法とその周辺技術(3))(S02 境界要素法とその周辺技術)

An alternative approach for the analysis of intermetallic compounds in SMT solder joints

In a properly wetted joining system, with tin/lead solder as the filler and copper as the base metals, a layer of intermetallic compounds is usually found at the interface of these two metals. This layer, mainly copper and tin, has profound effects on the joint’s properties and reliability. Optical microscopy or scanning electron microscopy micrographs are traditionally used for analysing the type and thickness of these compounds. An alternative analytical approach is presented. By using scanning electron microscopy in conjunction with energy‐dispersive X‐ray analysis, the elemental constituents across the interface can be plotted. More detailed and precise information about the compound distribution can thus be deduced. The studies reported concentrate on infra‐red reflowed joints. Unlike conventional wave‐soldered joints, only Cu6Sn5 was found in these. The growth of intermetallic compounds at different aging temperatures, and with solder paste exposed to atmosphere for different times, was also studied.

Growth kinetic studies of Cu–Sn intermetallic compound and its effect on shear strength of LCCC SMT solder joints

Growth kinetics of interfacial Cu–Sn intermetallic (IMC) layer and its effect on the shear strength on practical LCCC surface mount solder joints were studied for isothermal aging at 70, 120, 155 and 170°C. Only normal Cu 6Sn 5 ( η-phase) intermetallic was found in the interfacial IMC layer of as-soldered solder joint, whereas the duplex structure of both η-phase and ε-phase Cu 3Sn existed in all annealed joints. The growth kinetics of the overall interfacial IMC layer can simply be described by classical kinetic theory for solid-state diffusional growth with an activation energy of 1.09 eV and interdiffusion coefficient of 1.61×10 −4 m 2 s −1. The relatively higher activation energy, as compared with that found for bi-metallic couple of eutectic Sn–Pb solder on copper, is attributed to the dissolution of Ni from the component metallization into the bulk Sn–Pb solder. In addition, the shear fractures in all the solder joints investigated are shown to be ductile in nature and confined in the bulk solder rather than through the interfacial IMC layer. A linear reduction in shear joint strength was observed with an increase in intermetallic layer thickness up to ∼5.6 μm. Such a reduction in joint strength is due to a continuous removal of Sn from the bulk solder for the growth of interfacial IMC layer and flattening of the solder/IMC layer during isothermal aging of the solder joint.

The influence of dwell time on reliability of SMT solder joints under thermal cycling

The influence of dwell time on mechanical behaviour and fatigue life of SMT solder joints under thermal cycling has been investigated. The dwell time has two effects on the mechanical behaviour of SMT solder joints under thermal cycling: first, in the dwell time of high-temperature part, the stress in SMT solder joints will notably relax, and secondly, as the dwell time increase, the stress in solder joints in the low-temperature part of thermal cycling increases. With the increase of dwell time, the life of SMT solder joints under thermal cycling exponentially decreases.

Life Prediction of SMT Solder Joints under Thermal Cycling

In this paper, a formula for life prediction of SMT solder joints under thermal cycling has been established on a damage model. The major failure mechanisms such as fatigue, creep and atmospheric oxidation have been considered in the formula. The experimental verification shows that the life formula established in this paper coincides with the experimental results.

A dislocation model of shear fatigue damage and life prediction of SMT solder joints under thermal cycling : Jihuo Huanget al. IEEE Transactions on Components, Hybrids, and Manufacturing Technology, 15 (4), 553 (1992)

A dislocation model of shear fatigue damage and life prediction of SMT solder joints under thermal cycling : Jihuo Huanget al. IEEE Transactions on Components, Hybrids, and Manufacturing Technology, 15 (4), 553 (1992)

The Influence of Metal Plating of Chip Carriers on Reliability of SMT Solder Joints under Thermal Cycling

An experimental set‐up and a simulated ceramic chip carrier to study SMT solder joint reliability under thermal cycling have been developed. The influence of metal plating of the chip carrier on the reliability of the SMT solder joints under thermal cycling has been studied statistically.

A dislocation model of shear fatigue damage and life prediction of SMT solder joints under thermal cycles

In this paper, a damage model of low-cycle shear fatigue has been developed in the dislocation theory. On the basis of this model, a formula including the factors of thermal cycle temperature, dwell time and atmospheric oxidation has been established to predict the life of SMT solder joints under thermal cycles, and this has been verified by experiments on the specimens of true SMT assemblies. The results show that the life formula established in this paper coincides with the experimental results.

Cycle Life Prediction for SMT Solder Joints on TCE‐Mismatched Substrates

A method for the prediction of solder joint cycle life in surface‐mount assemblies is presented, based on the conversion of plastic solder shear strain into cycle life by means of an equation derived by Engelmaier. The paper introduces a different analytical procedure for the determination of solder joint shear strain. Shear strain is normally calculated from temperature and TCE differentials between package and interconnect board without consideration of elastic deformations. The suggested method derives average plastic shear strain of the solder joint at maximum temperature excursion from finite‐element analysis of a simple model consisting of an interconnect board, a solder joint and a package. All materials in the model have linear (elastic) properties, except solder which has non‐linear (elastic/plastic) characteristics. The solder stress/strain curve is described to the finite‐element programme with temperature‐dependent bilinear approximations. The solder joint is modelled as a single finite element so that only one value is computed for the plastic shear strain in the solder joint. This value represents the average shear strain which is converted into solder joint cycle life. The cycle life predictions with the finite‐element method are confirmed by cycling results obtained on actual hardware. The described method can serve as a design tool in the optimisation of surface‐mount assemblies. The procedure can help to define accelerated temperature cycling conditions.