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The purpose of this paper is to suggest an analysis methodology for the stencil printing process and to obtain proper design parameters that guarantee the successful filling using suggested finite element analyses.

Filling performance of solder paste in the stencil printing process is highly dependent on material properties such as viscosity and surface tension together with process parameters such as squeegee angle and squeegee speed. In order to investigate the effects of process parameters on the filling performance, the pressure built‐up under the squeegee and the filling procedure of the solder paste into an aperture were analysed. Due to the limitations of the computational memory and time, the analysis domain was simplified. The pressure development under the squeegee was investigated for various values of squeegee angle and speed; then, the filling behaviour with the pressure boundary condition was analysed for only one aperture. Finally, the two analysis results were integrated to obtain the successful filling condition. In this analysis method, process parameters that guarantee filling performance were decided on.

It was shown that higher squeezing pressure develops as the squeegee angle decreases and the squeegee speed increases. The filling performance, however, improves as the squeegee angle and the squeegee speed decrease. This is because the pressure duration time decreases as the squeegee speed increases.

This study suggests a new design approach to obtain proper process design parameters for successful filling of solder paste into an aperture. The direct analysis of filling with squeegee movement is impossible due to limitations of computer memory and computation time. To overcome these limitations, a two steps analysis approach is proposed and can be effectively applied in the design of stencil screen printing.

The basic parameters of screen printing are discussed, and an analytical model of the screen printing process is introduced. The ink roll in front of the squeegee is treated as a pump generating, close to the squeegee edge, high hydrostatic pressure which injects ink into the screen meshes. The shearing of the ink, the mechanics of screen snap‐off and the ink transfer taking place behind the squeegee are also analysed.

This paper examines the rôle that the squeegee plays in the solder paste printing process. Although the printing of solder paste is only one stage of many in the surface mount assembly process, it is crucial to deposit the correct amounts of solder paste cleanly onto the substrate. The amount of solder paste deposited affects the reliability and strength of the reflowed solder joint. Surface mount component lead pitches are continually being reduced due to the requirements of packing more and more components into a given space on the PCB, and this necessitates a proper understanding of the printing process and in particular of the squeegee which plays an important part in determining paste heights and the occurrence of defects. The paper outlines a model which predicts scooping and skipping in the stencil printing of solder pastes used in the reflow soldering of surface mounted devices. The model is based on the forces acting on the squeegee blade, which determines the paste flow pattern ahead of the squeegee, and on the stencil aperture geometry. The paper also examines the interactions between the paste properties and squeegee material properties. These interactions produce printing defects such as scooping, skipping and wet bridging. Results of an experimental comparison of different types of squeegee blade used in the stencil printing of solder pastes for reflow soldering in SMT, as well as the experimental results for squeegee deformation into stencil apertures, were used for validating the model. The empirically enhanced model which results takes into account the force on the squeegee due to solder paste flow and some of the non‐Newtonian properties of the solder paste. The main utility of the proposed model is the control of solder paste printing quality.

The objective of this investigation is the derivation of a mathematical model that describes the pressure characteristics of paste during the stencil printing process. This model is intended to generalise a qualitative understanding of these effects using squeegees that can be curved but otherwise are standard in design.

This is an analytical treatment of the paste behaviour from the foundations of continuity of fluid flow and shear stresses that are imparted by the squeegee blade movement.

An equation is obtained that profiles the pressure generated by the squeegee movement which, for the case of a linear squeegee, shows very good agreement with predicted pressure profiles using experimental data.

This model provides a theoretical framework for a better understanding of how to overcome the failure modes inherent in stencil printing, such as over‐ or under‐filled stencil cavities.

This is a generalisation of a previously developed mesh printing model. It goes beyond flat squeegee designs to describe the printing process when the blade and stencil are in contact. In addition, it encompasses non‐Newtonian fluid behaviour.

The purpose of this paper is to present a detailed overview of the current stencil printing process for microelectronic packaging.

This paper gives a thorough review of stencil printing for electronic packaging including the current state of the art.

This article explains the different stencil technologies and printing materials. It then examines the various factors that determine the outcome of a successful printing process, including printing parameters, materials, apparatus and squeegees. Relevant technical innovations in the art of stencil printing for microelectronics packaging are examined as each part of the printing process is explained.

Stencil printing is currently the cheapest and highest throughput technique to create the mechanical and electrically conductive connections between substrates, bare die, packaged chips and discrete components. As a result, this process is used extensively in the electronic packaging industry and therefore such a review paper should be of interest to a large selection of the electronics interconnect and assembly community.

The use of fine‐pitch SMD devices has increased the need for accurate and consistent solder paste deposits for reflow soldering. Continued miniaturisation in PCB and SMD lead sizes is presenting the user, paste supplier and print equipment manufacturer with paste printing challenges. Most of these challenges are user‐driven, and are generally met by enhancing associated print equipment and solder paste materials. Recent developments in fine‐particle pastes, water‐soluble and no‐clean pastes are among the improvements in materials. Vision‐assisted stencil aperture and PCB pad alignment, the use of metal squeegees and new stencil fabrication methods are among the latest developments on the equipment side. Printing tests have shown that there is a physical limit for the solder paste printing process, which is defined partly by the nature of the stencil fabrication process, the physical forces and the stencil's ability to meter a precise volume of paste. The challenge as SMD lead sizes decrease is to improve the printing process to match component lead sizes. There is a fear that we are now operating at the very limits of the solder paste printing process. To meet future component developments, there is a need to develop alternative printing processes for solder reflow.

This paper aims to establish the predictive equations of height, area and volume of printed solder paste during solder paste stencil printing (SPSP) process in surface mount technology (SMT) to better understand the effect of process parameters on the printing quality.

An experiment plan is proposed based on the response surface method (RSM). Experiments with 30 different combinations of process parameters are performed using a solder paste printer. After printing, the volume, area and height of the printed SAC105 solder paste are measured by a solder paste inspection machine. Using RSM, the predictive equations associated with the printing parameters and the printing quality of the solder paste are formed.

The optimal printing parameters are 175.08 N printing pressure, 250 mm/s printing speed, 0.1 mm snap-off height and 15.7 mm/s stencil snap-off speed if the target height of solder paste is 100 µm. As the target printing area of solder paste is 1.1 mm × 1.3 mm, the optimized values of the printing parameters are 140.29 N, 100.52 mm/s, 0.63 mm and 20.25 mm/s. When both the target printing height and area are optimized together, the optimal values for the four parameters are 86.67 N, 225.76 mm/s, 0.15 mm and 1.82 mm/s.

A simple RSM-based experimental method is proposed to formulate the predictive polynomial equations for height, area and volume of printed solder paste in terms of important SPSP parameters. The predictive equation model can be applied to the actual SPSP process, allowing engineers to quickly predict the best printing parameters during parameter setting to improve production efficiency and quality.

Experimental design has proved to be a useful statistical tool in reducing process variation. The technique has been applied to a wide range of processes, including electronics assembly and soldering processes. For effective SMT assembly the screen printing of solder paste requires tight process control, especially as pad geometries become ever smaller. However, printing of solder paste is a rather complex process which is affected by machine, material, environmental and human factors, which make it difficult to characterise effectively. This paper examines the practical application of experimental design to solder paste printing for SMT and also the results from a number of experiments carried out on a semi‐automatic ‘clamshell’ type screen printer. The experimentation concentrates on the important printer and squeegee parameters and their effect on paste deposition, with measured solder paste height and ‘measle’ diagrams used as process outputs. The usefulness of the experimental results in determining the best printer settings, as well as the problems encountered during the experimentation, are highlighted.

This research aims to study the stencil printing process of the quad flat package (QFP) component with a pin pitch of 0.4 mm. After the optimization of the printing process, the desired inspection specification is determined to reduce the expected total process loss.

Static Taguchi parametric design is applied while considering the noise factors possibly affecting the printing quality in the production environment. The Taguchi quality loss function model is then proposed to evaluate the two types of inspection strategies.

The optimal parameter-level treatment for the solder paste printing process includes a squeegee pressure of 11 kg, a stencil snap-off of 0.14 mm, a cleaning frequency of the stencil once per printing and using an air gun after stencil wiping. The optimal upper and lower specification limits are 119.8 µm and 110.3 µm, respectively.

Noise factors in the production environment are considered to determine the optimal printing process. For specific components, the specification is established as a basis for subsequent processes or reworks.

‘Fine Pitch’ and ‘High speed printing’ are relative terms but many solder paste users see capability in meeting these two requirements as their major goals for process improvements. Not surprisingly, solder paste rheology governs both, and this paper describes how the complex relationship between resins and solvent can lead to solder pastes with optimised performance. Work on the physical behaviour of resin solutions and how this relates to solder paste rheology is reported. These results are related to user experience on volume production processes.