Surface Mount Technology Assembly Research Articles

Defect patterns study of pick-and-place machine using automated optical inspection data

PurposeThis paper aims to study the component pick-and-place (P&P) defect patterns for different root causes based on automated optical inspection data and develop a root cause identification model using machine learning.Design/methodology/approachThis study conducts experiments to simulate the P&P machine errors including nozzle size and nozzle pick-up position. The component placement qualities with different errors are inspected. This study uses various machine learning methods to develop a root cause identification model based on the inspection result.FindingsThe experimental results revealed that the wrong nozzle size could increase the mean and the standard deviation of component placement offset and the probability of component drop during the transfer process. Moreover, nozzle pick-up position can affect the rotated component placement offset. These root causes of defects can be traced back using machine learning methods.Practical implicationsThis study provides operators in surface mount technology assembly lines to understand the P&P machine error symptoms. The developed model can trace back the root causes of defects automatically in real line production.Originality/valueThe findings are expected to lead the regular preventive maintenance to data-driven predictive and reactive maintenance.

Analysis of Defects Generated by the Reflow Soldering in SMT (Surface Mount Technology) Assembly Applying the Six Sigma Method

The Six Sigma method using the DMAIC methodology is being applied for analyzing the reflow soldering process in an SMT assembly line. The Define phase (D) and Measure phase (M) were concluded, the Analysis (A) phase is being implemented, and the Improve (I) and Control (C) phases will be the next ones. Defects generated during the reflow process were classified and measured both on assembled memory modules and on virgin laminates that were passed through the oven during the reflow of these modules. Spots of solder and flux were found on the edge connector of the modules and also on the surface of the virgin laminates. It was found that these defects are generated inside the reflow oven, indicating that the oven is contaminated. Two solder pastes were analyzed and consequently, two temperature profiles were used. The amount of defects generated by the oven was found to be independent on the temperature profile. On the other hand the amount of defects depends on the solder paste that is used. The FMEA (Failure Mode and Effect Analysis) was also accomplished. As a result, the main failure modes of the reflow process were determined, namely, the heating rate, the soak temperature, the conveyor velocity, the reflow temperature, the reflow time, and the cooling rate.

SMT assembly effects on organic substrate lifetime reduction

PurposeThe purpose of this study is that the effects of surface mount technology (SMT) assembly process on the product lifetime of fine-pitch printed circuit boards (PCBs) were investigated under biased highly accelerated stress testing (HAST).Design/methodology/approachSMT assembly from a semiconductor SMT assembly process was replicated to test PCBs under the same conditions as SMT-assembled PCBs. The median lives µ and standard deviation s of the test PCBs were calculated from the log-normal distribution. The failure analysis of current leakages was conducted by the focused ion beam, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Using the inverse power law and modified Peck-H’s relationship, the PCB lives at accelerated (by SMT assembly stress) and user conditions were calculated.FindingsThe failure analysis demonstrated that SiO2 and BaSO4 fillers added for stiffening organic materials promote current leakage failure. Therefore, the hydrophobicity of these fillers is believed to be necessary to suppress the current leakage failure under biased HAST. The inverse power law model indicates that the acceleration life model with SMT assembly stress can be given as follows: L(V) = 271.9(S)−0.5031. From modified Peck-H’s relationship, after the third SMT assembly, the time required to attain 0.96 per cent failures at 35°C/60 per cent RH/1.9 V and 130°C/85 per cent RH/3.5 V are 129 y and 69.5 h, respectively. The biased HAST at 130°C/85 per cent/3.5 V after the third SMT assembly for 69.5 h on 238 samples could be recommended as an early quality-monitoring procedure.Research limitations/implicationsIn the future, the failure modes in an early stage of a bathtub should be analyzed and the life prediction model should be studied accordingly.Originality/valueThrough this study, the lifetime prediction model and early quality-monitoring procedure for organic substrates because of SMT assembly stress were obtained.

Real-Time Stencil Printing Optimization Using a Hybrid Multi-Layer Online Sequential Extreme Learning and Evolutionary Search Approach

This article aims to develop a dynamic optimization model performing real-time control of a stencil printing process (SPP) by maintaining the optimal printer parameter settings. In a surface mount technology (SMT) assembly line, stencil printing is a major process that affects the yield of printed circuit boards (PCBs). During printing, environmental changes may induce the PCB’s printing results to deviate from initial optimal outcomes. To consistently improve the system performance, a real-time adaptation of the printer settings is an effective and cost-efficient approach. This research proposes a hybrid online optimization model by using online learning to predict real-time SPP volumes and an evolutionary search (ES) technique to determine the optimal settings. The prediction model investigates the printing volumes’ transfer efficiency (TE) in averages and standard deviations (SDs) with relevant features. From the model selection of the online-based learning, the multi-layer online sequential extreme learning machine (MOSELM) shows outstanding prediction performance with $R^{2}$ values of 97% for volume averages and 81% for SDs. From the real implicational results, the system achieves a $C_{pk}=2.8$ , outperforming other advanced models. The proposed framework exhibits a good balance between accuracy and retraining efficiency, promising effective SMT assembly dynamic control.

Dynamic Predictive Modeling of Solder Paste Volume with Real Time Memory Update in a Stencil Printing Process

This research aims to develop a dynamic prediction model to assist real-time decision making of a stencil printing process by maintaining high prediction accuracy of the printing process. In a Surface Mount Technology (SMT) assembly line, the stencil printing process (SPP) accounts for more than 50% of the defectiveness of printed circuit boards (PCBs). During the printing process, environmental changes such as humidity or wear of blades may induce the PCBs printing results to deviate from the target volume. Thus, real-time adjustment of the printer settings (e.g., printing parameters, clean cycles, etc.) based on prediction of printing volumes is critical to maintain a high printing performance. However, research has been limited in real time SPP control, which is partially due to the difficulties in predicting the paste volumes with high accuracy and time efficiency. To tackle the challenges, this research proposes novel online learning models for real-time SPP status prediction. The prediction model is implemented by selecting advanced online learning models to estimate the printing volumes in averages and standard deviations (SDs) considering different pad sizes with different clean ages, directions, printer parameters, etc. The model performances are evaluated in Root Mean Square Error (RMS E), R2, etc. From comparison, the Support Vector Regressor (SVR) shows outstanding prediction performance with R2 values of 92% and 81% for volume averages and SDs. This research emphasizes the potential of using online learning as a preliminary process for effective real-scenario SMT assembly dynamic control.

Statistical Analysis for Component Shift in Pick and Place Process of Surface Mount Technology

The placed electronic component can shift on the wet solder paste in pick and place (P&P) process of surface mount technology (SMT). It does not usually attract much attention, because the shift is considered to be negligibly small and the following self-alignment effect in the solder paste reflow soldering process could also make it up. However, with the decreasing size of the electronic components and the increasing demand for the low defective rate of PCB, the component shift in P&P process is becoming more and more important in quality control of SMT industries. Though a few papers are related to the component shift in P&P process, there is no earlier research using the data from the real production line. In this paper, we study two basic and important issues: the behavior of the component shift in P&P process and the contributing factors to it. Several statistical methods are used to explore the behavior component shift based on the data from a complete state-of-the-art SMT assembly line. Main effects and regression analysis are implemented to pinpoint the contributing factors. In order to investigate the issues comprehensively, six types of electronic components and multiple potential factors are considered in this work, e.g., solder paste properties (position, volume, area, height), designed position of the component, placement pressure. The results indicate that component shift cannot be ignored. Also, the position of solder paste, designed position of component and component type are the top three most important factors to study the component shifts in P&P process.

Prediction of Component Shifts in Pick and Place Process of Surface Mount Technology Using Support Vector Regression

In pick and place (P&P) process of surface mount technology (SMT) the placed component can shift from its ideal (or designed) position on the wet solder paste. The solder paste with some fluid properties could slump and the unbalance between different sides of solder paste can lead to other forces on the components as well. Though the shifts are usually considered to be negligible and can be made up to some extent by the following self-alignment during the process of soldering reflow, it should be attracted attention as its importance for addressing the quality of the printed circuit board (PCB) in SMT. To minimize or control the component shifts, whose relationship with the characteristics of the solder paste (e.g., offset, volume) should be studied initially. In this paper, we design a comprehensive experiment and collect the data from a state-of-the-art SMT assembly line. Then we use support vector regression (SVR) model to predict the component shifts based on different situations of solder paste and placement settings. Also, two kernel functions, linear (SVR-Linear) and radial basis function (SVR-RBF), are employed. The achieved results indicate that the component shift in P&P process is significant, and the SVR model is highly qualified for the forecast of the component shifts. Particularly, the SVR-RBF model outperforms the SVR-Linear model considering the prediction error.

Effect of the surface mounting technology assembly based on lean production: A case study

Effect of the surface mounting technology assembly based on lean production: A case study

Solder-Joint Reliability of a Radar Processor for Semi-Autonomous Driving Applications

Abstract Radar is currently employed in automotive applications to provide the range, angle, and velocity of objects using RF waves (77GHz). This paper outlines solder joint reliability of a specific micro-processor that processes data received from a SRR (short range radar operating from 0.2 to 30 meters). It is a powerful digital signal processing accelerator, which targets safety applications that require a high Automotive Safety Integrity Level (ASIL-B). The paper explores the package design and construction, SMT (surface mount technology) assembly, and board level reliability testing of various BGA pad surface finish and solder ball alloy materials on a 0.65 mm pitch, 10 × 10 mm body 141 MAPBGA (mold array process-ball grid array) package. The package configurations include two BGA pad surface finishes (Ni/Au and OSP [organic solderability protectant]) and three solder alloys (SnAg, SAC405, and SAC-Bi [a Bi containing SAC derivative]). Solder joint reliability analysis was performed through AATS (air-to-air thermal shock) between 40°C and +125°C and JEDEC Drop Testing at 1500G's. Thermal shock was extended until at least 75% of the populations failed, which was well past the points needed to qualify the packages for the intended end-use applications. The evaluations of the micro-processor indicate that the MAPBGA package can meet the ASIL-B specification requirements with optimized combinations of BGA pad surface finish and solder alloy. The focus of this paper was to determine the baseline solder-joint thermal shock and JEDEC drop performance with varied BGA pad surface finish and solder ball alloy materials.

Influence of Secondary Impact on Printed Wiring Assemblies—Part II: Competing Failure Modes in Surface Mount Components

Portable electronic devices are commonly exposed to shock and impact loading due to accidental drops. After external impact, internal collisions (termed “secondary impacts” in this study) between vibrating adjacent subassemblies of a product may occur if design guidelines fail to prevent such events. Secondary impacts can result in short acceleration pulses with much higher amplitudes and higher frequencies than those in conventional board-level drop tests. Thus, such pulses are likely to excite the high-frequency resonances of printed wiring boards (PWBs) (including through-thickness “breathing” modes) and also of miniature structures in assembled surface mount technology (SMT) components. Such resonant effects have a strong potential to damage the component, and therefore should be avoided. When the resonant frequency of a miniature structure (e.g., elements of an SMT microelectromechanical system (MEMS) component) in an SMT assembly is close to a natural frequency of the PWB, an amplified response is expected in the miniature structure. Components which are regarded as reliable under conventional qualification test methods may still pose a failure risk when secondary impact is considered. This paper is the second part of a two-part series exploring the effect of secondary impacts in a printed wiring assembly (PWA). The first paper is this series focused on the breathing mode of vibration generated in a PWB under secondary impact, and this paper focuses on analyzing the effect of such breathing modes on typical failure modes with different resonant frequencies in SMT applications. The results demonstrate distinctly different sensitivity of each failure mode to the impacts.

Board-Level Thermal Cycling and Drop-Test Reliability of Large, Ultrathin Glass BGA Packages for Smart Mobile Applications

Glass substrates are emerging as a key alternative to silicon and conventional organic substrates for high-density and high-performance systems due to their outstanding dimensional stability, enabling sub-5- $\mu \text{m}$ lithographic design rules, excellent electrical performance, and unique mechanical properties, key in achieving board-level reliability at body sizes larger than $15\times15$ mm2. This paper describes the first demonstration of the board-level reliability of such large, ultrathin glass ball grid array (BGA) packages directly mounted onto a system board, considering both their thermal cycling and drop-test performances. To investigate board-level reliability, glass BGA packages, $18.5\times18.5$ mm2 in body size and 100 $\mu \text{m}$ in thickness, were first designed and fabricated with a daisy-chain pattern. The glass test vehicles were fabricated at panel level, and then BGA balled by ball drop process with SAC105 solder balls, 250 $\mu \text{m}$ in diameter at 400- $\mu \text{m}$ pitch. After singulation, the glass packages were mounted onto printed circuit boards using standard surface mount technology assembly processes, and then subjected to reliability testing through thermal cycling and drop tests following JEDEC reliability standards. The effect of the coefficient of thermal expansion (CTE) of glass was evaluated by investigating low- and high-CTE glass substrates, with the CTEs of 3.8 and 9.8 ppm/°C, respectively. While all glass packages passed 1000 thermal cycles at −40/125 °C as predicted by thermomechanical modeling using the Engelmaier–Wild model, the fatigue life of high-CTE samples exceeded 5000 thermal cycles. In addition, 28/30 drop-test samples passed the required 40 and 200 drops on corner and inner circuits, respectively, with no clear effect of the glass CTE. The predominant failure modes were systematically identified for both reliability tests.

Novel Adaptive Sliding Mode Control with Nonlinear Disturbance Observer for SMT Assembly Machine

This paper presents a novel adaptive sliding mode control based on nonlinear sliding surface with disturbance observer (ANSMC-DOB) for precision trajectory tracking control of a surface mount technology (SMT) assembly machine. A two-degree-of-freedom model with time-varying parameter uncertainties and disturbances is built to describe the first axial mode of the pick-place actuation axis of the machine. According to the principle of variable damping ratio coefficient which makes the system have a nonovershoot transient response and a short settling time in the second-order system, the nonlinear sliding surface is designed for the sliding mode control (SMC). Since the upper bound value of the disturbances is unknown, the adaptive gain estimation is applied to replace the switching gain in the SMC. In order to settle the problem of SMC unrobust to the mismatched parameter uncertainties and disturbances, the nonlinear disturbance observer is introduced to estimate the mismatched disturbances and form the novel controller of ANSMC-DOB. The stability of sliding surfaces and control laws are verified by the Lyapunov functions. The simulation research and comparative experiments are conducted to verify the improvement of positioning accuracy and robustness by the proposed ANSMC-DOB in the SMT assembly machine.

Materials and soldering challenges in lead-free Package-on-Package (PoP) technology

Purpose– The purpose of this paper is to present challenges met during package-on-package (PoP) technology implementation in real surface-mount technology assembly processes.Design/methodology/approach– The properties and behavior of different combinations of soldering materials, PoP components and soldering profiles were investigated, both in the laboratory and during production trials. The purpose of such an approach was identification of existing problems and challenges in lead-free PoP systems assembly as well as checking which soldering material designed to PoP is more suitable for this technology.Findings– Technological trials are needed to select adequate soldering materials for PoP systems assembly, as laboratory tests of materials alone were not sufficient. The challenges of PoP technology were associated with the equipment utilized, the soldering materials, operational parameters and the soldering profile used for assembly. The localization of defects in PoP systems is very difficult and, in many cases, destructive methods have to be used on solder joints for the assessment and confirmation of failures.Originality/value– This paper shows main materials and soldering challenges in lead-free PoP technology. In particular, the problem related with selection of soldering materials and soldering profiles for PoP was presented. Moreover, the issues that have to be taken into consideration during the planning of a PoP system assembly procedure are presented.

Effect of reflow soldering profile on intermetallic compound formation

Reflow soldering in a nitrogen atmosphere is a common process in surface mount technology assembly since it can increase solder joint reliability. The present study investigated the effect of different reflow soldering atmospheres, either air or nitrogen, on intermetallic compound IMC formation and growth. Several techniques of materials characterisation including optical, image analysis, scanning electron microscopy and energy dispersive X-ray analysis were used to characterise the intermetallics. Besides, the effects of cooling rate and isothermal ageing were also studied. In summary, reflowing under nitrogen atmosphere had better effect on IMC formation and growth compared to reflowing under air. Besides, the cooling rate of solder during reflow also appears to have an effect on the final structure of the solder joint, and controlling the growth behaviour of the IMC during subsequent isothermal ageing. However, further research can be carried out to determine the solder joint's strength produced by both reflow soldering profiles.

Effect of Reflow Profile on Intermetallic Compound Formation

Reflow soldering in a nitrogen atmosphere is a common process consideration in surface mount technology assembly. This is because the use of nitrogen in reflow equipment may benefit the process as well as the quality of the end product, where it can increase the reliability of the solder joint. So far, many papers have reported effects of cooling speed, type of solder pastes and solder fluxes on the reliability of lead-free solder joints. While the effects of reflow conditions on intermetallic compound (IMC) formation at the solder joint such as the atmosphere during the reflow process are still unclear. The present study investigated thoroughly the effect of different reflow soldering atmosphere, which is air and nitrogen on IMC formation and growth. Several techniques of materials characterization including optical, image analysis, scanning electron microscopy and energy dispersive X-ray analysis will be used to characterise the intermetallics in terms of composition, thickness and morphology. In addition, the effects of cooling rate and isothermal aging were also studied for the solder alloy Sn–4Ag–0.5Cu on electroless nickel/immersion gold (ENIG) surface finish. From the study, it was found that reflowing under nitrogen atmosphere had better effect on IMC formation and growth compared to reflowing under air. Besides, the cooling rate of solder during reflow also appears to have a significant effect on the final structure of the solder joint, and controlling the growth behaviour of the IMC during subsequent isothermal aging.

A study of SnAgCu solder paste transfer efficiency and effects of optimal reflow profile on solder deposits

The reliability of solder joints in electronic products are greatly enhanced by good stencil printing and quality reflow soldering. The stencil printing process is widely used in Surface Mount Technology (SMT) to deposit solder paste on the substrate and is a critical step in SMT assembly as it has been widely claimed that up to 50% of the defects found in the assembly of printed circuit boards (PCBs) are attributed to stencil printing. Solder paste release from stencil during printing is a key factor which affects the quality of solder prints. Thus, the efficient transfer of paste from stencil through aperture to pad is a fundamental concern in SMT production process. The recent trends on further miniaturisation of electronic products have introduced more process challenges in the SMT assembly. The assembly of surface mount packages such as flip chips, chip scale packages and fine pitch ball grid arrays are challenging the current stencil printing and reflow profiling capabilities. The effective mounting of these miniaturised packages requires good transfer efficiency of solder paste through small stencil aperture. As further electronic product miniaturisation culminates in progressive use of decreasing stencil aperture sizes, the in-depth understanding of the dependency of transfer efficiency of solder paste on diminishing stencil aperture areas has become vital to improving solder joint reliability. This study investigates the transfer efficiency of type 3, 96.5Sn3.0Ag0.5Cu solder paste through linearly decreasing rectangular stencil aperture sizes typically used in PCB assembly. In addition, the research examines the effects of optimal reflow profile (ORP) on the solder deposit volumes. The results from the study show a power law relationship between actual solder deposit volume (SDV) and aperture cavity. The observed effect of ORP on actual SDVs was a 46% volume change which was fairly constant across the pad geometries. Our study shows that the transfer efficiency of solder paste decreases with decreasing stencil aperture size. A novel mathematical model η T = 100 e - | V A - V C | ∗ | V A - V C + D m + e 10 - 5 D m - 1 | for V C ⩾ 0 is proposed for computing the transfer efficiency of solder paste through rectangular stencil aperture sizes.

A heuristic model and software development for SMT line balancing: a case study

Printed circuit board assembly (PCBA) is the major portion of manufacturing processes of electronic manufacturing services (EMS) industry, where surface mounting technology (SMT) has become the primary assembly method. Two series-connected SMT placement machines in a SMT assembly line are often the bottlenecks due to the unevenly distributed workloads. This paper studies the line balancing of the SMT assembly line focusing on the workload distribution between the two placement machines. A heuristic approach is proposed to reduce the workload difference of the two machines without increasing the total machine setup time. A software, which can be used as an effective automation tool for a company, is then developed based on the heuristic model. This will increase the quality of the service that the company provides to its customers.

A Minimum-Jerk Speed-Planning Algorithm for Coordinated Planning and Control of Automated Assembly Manufacturing

We previously proposed a general algorithm for coordinating the motions among multiple machines in a shared assembly environment based on a constant-speed motion model. In this paper, we extend this work to a minimum-jerk polynomial motion model and describe a new speed-planning algorithm to plan automated assembly machines' motions. Machines are planned sequentially, based on their priorities, by mapping the motions of higher-priority machines into forbidden regions in two-dimensional space-time graphs. Collision-free minimum-jerk motions are then planned between the forbidden regions in the graphs. The new speed-planning algorithm is evaluated on a dual-robot surface-mount technology assembly machine in which both robots share a common workspace. Note to Practitioners-Automated assembly processes, especially surface-mount technology manufacturing, require a high degree of precision when placing certain components. This motivated us to find a way of maintaining good positional accuracy by planning smooth motions for the machines that perform these tasks. Since many of these machines have two or more robots, their motions must also be coordinated. We developed an algorithm that combines coordinated motion concepts with a minimum-jerk motion model that can solve these problems. The algorithm plans segmented paths for the robots and then sequentially plans their speeds to prevent collisions between them. The planned speeds ensure position, velocity, and acceleration continuity between path segments. The smooth motions resulting from this method enable high-accuracy component placement. The tradeoff for this improvement is increased cycle time compared to other speed-planning methods

A Novel Anisotropic Conductive Adhesive for Lead-Free Surface Mount Electronics Packaging

Abstract The electronics industry, in recent years, has been focusing primarily on product miniaturization and lead-free assembly. The need for product miniaturization is due to the continuous demand for portable electronic products that are multifunctional, yet smaller, faster, cheaper, and lighter. This is forcing the industry to design and assemble products with miniature passive and active devices. These devices typically have fine pitch footprints that provide a very small surface area for attachment. The solder attach technique relies primarily on the formation of intermetallics between the mating metallic surfaces. With a reduction in the surface area of the pads, the ratio of intermetallic to solder is very high once the solder joint is formed. This could result in unreliable solder joints, due to the brittle nature of intermetallics. In addition, the need to eliminate lead-based materials as a means of interconnection has renewed the industry’s interest in exploring other means of assembling surface mount devices reliably. The use of a novel anisotropic conductive adhesive (ACA) as a means for assembling surface mount devices, the ACA’s performance characteristics, and preliminary research findings are discussed in this paper. Typically, ACAs require the application of pressure during the curing process to establish the electrical connection. The novel ACA uses a magnetic field to align the particles in the Z-axis direction and eliminates the need for pressure during curing. The formation of conductive columns within the polymer matrix provides a very high insulation resistance between adjacent conductors. The novel ACA also enables mass curing of the adhesive, eliminating the need for sequential assembly. The novel ACA was found to be very effective in providing the interconnection for surface mount technology (SMT) passives and leaded, bumped, or bumpless integrated circuit packages. The requirement for precise stencil printing was eliminated, as the application of magnetic field aligned the conductive columns in the Z-axis direction eliminating any lateral conductivity. The ability to mass cure the adhesive while applying the magnetic field reduced the assembly time considerably. Placement accuracy was still found to be very critical. Shear testing of adhesive joints after thermal aging showed significance past 500 h and after temperature–humidity aging showed significance within the first 100 h. I–V characteristics of the daisy chained ball grid array devices assembled with and without bumps revealed considerable difference in the breakdown current. The correlation between initial contact resistance of the daisy chain and the final breakdown current was also determined. Preliminary experiments and findings, discussed in this paper, show the viability of the ACA for mixed SMT assembly. Further experimentations will include in situ contact resistance measurements during thermal aging, temperature–humidity aging, drop testing and thermal shock.

Optimization of Component Placement Scheduling for SMT Assemblies

The surface mounting of electronic component is the major manufacturing technology for the electronic products in the last decade. The surface mounting technology (SMT) is an assembly process that assembles the surface mountable component (SMC) and the printed circuit board (PCB) together. The SMT mounter is an automatic assembly machine that processes the SMT assemblies in terms of the optical positioning and robotic handling. The SMT assembly consists of calibrating printed circuit board (PCB); vacuuming components form feeder stations; compensating the orientation of the vacuumed surface mountable component (SMC); and finally placing SMC chips on the PCB. In order to increase the throughput, the synchronous batch vacuuming of SMC components is designed. In addition, different types of component feeding and mixing in each batch increase the difficulties of finding the best component mounting sequence. In this paper, the optimal component placement scheduler is desired to perform higher assembly performance and to reduce the cycle time. The proposed optimal component placement scheduler is developed based on the rule based heuristic search approach. In addition, to evaluate the cycle time of each heuristic search, the route oriented Petri nets (ROPN) based SMT assembly models are constructed. The optimal component placement scheduler can be further determined in terms of evaluating the ROPN SMT assembly models. Finally, the practical test PCB board data is discussed in this paper.