iNEMI solder paste deposition project - First stage review optimizing solder paste printing for large and small components (original) (raw)
Related papers
As the density of board design increasing fast, the distance between the adjacent components becomes much smaller. When the miniature chip components and the fine pitch components which require smaller volumes of solder paste are close to the castle-like components, connectors with poor pin co-planarity and CCGAs which require more solder paste, only one single thickness stencil could not satisfy all of the components at the same printing process. At present, the step stencil is the cheapest and most popular solution, but the layout density could not increase more because of the keep-out distances. The objective of this iNEMI Solder Paste Deposition Project is to understand the major factors to step stencil printing quality and where are the limitations.
Optimization Of Solder Paste Printing Parameters Using Design Of Experiments (DOE)
2005
The solder paste printing process is an important process in the assembly of Surface Mount Technology (SMT) devices using the reflow soldering technique. There is a wide agreement in the industry that the paste printing process accounts for the majority of assembly defects. Experience with this process has shown that typically over 60% of all soldering defects are due to problems associated with the screening process. Therefore, operation and parameter setup of the stencil printing process are the key elements when trying to minimize defects. Parameters such as squeegee pressure, squeegee speed, stencil separation speed, snap-off and stencil cleaning interval are the most important factors in the process to achieve a better yield. This paper describes the experiment design approach for solder paste printing process. A factorial design technique has been used to study the effects of the solder paste printing process parameters. Sixteen experimental trial were carried out in the experiment with two levels for each factor. The output from the experiment is the solder paste height, and the data has been statistically analyzed by using Minitab Software. The Analysis of Variance (ANOVA) showed that the important factors for the solder paste height are squeegee pressure and snap-off with the optimal setting for printing speed, squeegee pressure, snap-off, squeegee separation, and cleaning interval. The experiment error between the predicted regression model and actual verification was found to be 1.61%. It is shown that by using DOE 18% improvement of the solder paste height can be achieved.
2016
Industry standards such as J-STD-005 and JIS Z 3284-1994 call for the use of viscosity measurement(s) as a quality assurance test method for solder paste. Almost all solder paste produced and sold use a viscosity range at a single shear rate as part of the pass fail criteria for shipment and customer acceptance respectively. As had been reported many times, an estimated 80% of the defects associated with the surface mount technology process involve defects created during the printing process. Viscosity at a single shear rate could predict a fatal flaw in the printability of a solder paste sample. However, false positive single shear rate viscosity readings are not unknown. Intuitively, solder paste is subjected to several shear rates during the printing process. A squeegee forcing paste into an aperture may be the highest, and most critical strain rate applied to solder paste during the process. Separation of the stencil from the printed circuit card may be the second most important...
IMAPSource Proceedings
System-in-Package (SiP) assembly has become a popular solution for the challenges of continued miniaturization in the semiconductor industry. The continued and expected growth of the semiconductor industry in the coming years is driving more advanced assembly methods within System-in-Package and advanced packaging in general, and more advanced semiconductor assembly materials are required to meet those challenges such as solder paste specifically designed for SiP assembly, with fine solder powder and specifically formulated flux vehicles. Fine feature solder paste printing as an assembly method continues to be a challenge for SiP assembly. Small stencil aperture designs have necessitated fine-powder solder pastes, with type 5, type 6, and type 7 being common, as well as there being a need for type 8 for future, more advanced designs. Additionally, as more components are being packed into a SiP, solder paste rheology becomes an important characteristic to consider. Printing transfer ...
The International Journal of Advanced Manufacturing Technology, 2019
The present study examines the effect of squeegee load, squeegee speed, and separation speed on the printing performance of lead-free solder paste, and solder printing was carried out to evaluate the effect of the filled volume of the solder paste during stencil printing. Application of pressure on the squeegee affects the filled volume of the solder paste in the stencil aperture, and the incorrect pressure setting could cause incomplete filling. Herein, an experiment was conducted on a printing machine employing surface mount technology. The solder paste used in the study was Sn/Ag/Cu (SAC305), and four components, namely, 0603, small outline transistor (SOT), 1210, and tantalum-D, were tested. The filled volume and height of the solder paste under different squeegee loads, squeegee speeds, and separation speeds were determined, and the solder volume was found to vary with the squeegee load and component type. Response surface method (RSM) optimization is conducted to obtain optimum filled volume and solder paste height and area during the printing process. The method showed squeegee load, squeegee speed, and separation speed have considerable effects on filled volume, solder paste height, and solder paste area.
Soldering & Surface Mount Technology, 2019
Purpose The purpose of this paper is to investigate and minimize the printing-related defects in the surface mount assembly (SMA) process. Design/methodology/approach This paper uses an experimental approach to explore process parameter and printing defects during the SMA process. Increasing printing performance, various practices of solder paste (Ag3.0/Cu0.5/Sn) storage and handling are suggested. Lopsided paste problem is studied by varying squeegee pressure and the results are presented. Unfilled pads problems are observed for ball grid array (BGA) and quad flat package (QFP) which is mitigated by proper force tuning. In this paper, a comparative study is conducted which evaluates the manifestation of printing offset due to low-grade stencil. The input/output (I/O) boards were oxidized when the relative humidity was maintained beyond 70 per cent for more than 8 h. This pad oxidation problem is overcome by proper printed circuit board (PCB) handling procedures. When the unoptimize...
Characterization of printed solder paste excess and bridge related defects
2008 2nd Electronics Systemintegration Technology Conference, 2008
Surface Mount Technology (SMT) involves the printing of solder paste on to printed circuit board (PCB) interconnection pads prior to component placement and reflow soldering. This paper focuses on the solder paste deposition process. With an approximated cause ratio of 50-70% of post assembly defects, solder paste deposition represents the most significant cause initiator of the three sub-processes. Paradigmatic cause models, and associated design rules and effects data are extrapolated from academic and industrial literature and formulated into physical models that identify and integrate the process into three discrete solder paste deposition events-i.e. (i) stencil / PCB alignment, (ii) print stroke / aperture filling and (iii) stencil separation / paste transfer. The project's industrial partners are producers of safety-critical products and have recognised the in-service reliability benefits of electro-mechanical interface elimination when multiple smaller circuit designs are assimilated into one larger Printed Circuit Assembly (PCA). However, increased solder paste deposition related defect rates have been reported with larger PCAs and therefore, print process physical models need to account for size related phenomena.
Size Matters-The Effects of Solder Powder Size on Solder Paste Performance
2019
Solder powder size is a popular topic in the electronics industry due to the continuing trend of miniaturization of electronics. The question commonly asked is “when should we switch from Type 3 to a smaller solder powder?” Solder powder size is usually chosen based on the printing requirements for the solder paste. It is common practice to use IPC Type 4 or 5 solder powders for stencil designs that include area ratios below the recommended IPC limit of 0.66. The effects of solder powder size on printability of solder paste have been well documented. The size of the solder powder affects the performance of the solder paste in other ways. Shelf life, stencil life, reflow performance, voiding behavior, and reactivity / stability are all affected by solder powder size. Testing was conducted to measure each of these solder paste performance attributes for IPC Type 3, Type 4, Type 5 and Type 6 SAC305 solder powders in both water soluble and no clean solder pastes. The performance data fo...
Flow processes in solder paste during stencil printing for SMT assembly
Journal of Materials Science: Materials in Electronics, 1995
Solder paste is used for reflow soldering of Surface Mount Devices (SMDs). In this paper we discuss how the various stages of the stencil printing cycle affect the rheological properties of the solder paste. First the heat generated in the paste roll is examined to see what effect it has on solder paste rheology, then we analyse in detail the process of paste withdrawal from a metal mask stencil and discuss those properties of solder paste that lead to a good print in terms of the size and shape of the solder paste particles, and their packing. In order to do this, we review some of the experiments and phenomena that have been shown to occur in dense suspensions, and see what aspects of that work are applicable to solder paste printing.
Microelectronic Engineering, 2011
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.