Technical Library | 2009-07-15 12:14:31.0
The increasing demand for smaller & smaller portable electrical devices is leading to the increasing usage of extremely small components in the SMT assembly lines. With the introduction of 01005 packages in mass production, all the different stages of the line are facing new challenges: from board design, through component placement to reflow process. Each stage introduces some specific types of defect which are considered impossible to repair due to the small size of the package. AOI has become an essential tool to enable good yield in the assembly of 01005.
Technical Library | 2018-07-18 16:28:26.0
Reduction of first pass defects in the SMT assembly process minimizes cost, assembly time and improves reliability. These three areas, cost, delivery and reliability determine manufacturing yields and are key in maintaining a successful and profitable assembly process. It is commonly accepted that the solder paste printing process causes the highest percentage of yield challenges in the SMT assembly process. As form factor continues to get smaller, the challenge to obtain 100% yield becomes more difficult.This paper will identify defects affecting SMT yields in the printing process and discuss their Root Cause. Outer layer copper weight and surface treatment will also be addressed as to their effect on printability. Experiments using leadless and emerging components will be studied and root cause analysis will be presented
Technical Library | 2018-03-15 07:23:35.0
The SMT assembly process is continuously challenged by the factors which enhance circuit board performance and limit productivity. The pick and place and reflow systems reflect these driven issues by adding more and more controls to their systems, but the fact is one of the age old processes continues to operate within the same rules since the dawn of the SMT assembly world: The SMT screen printing. (...)This paper showcases a new stencil process that was discovered by reverting to the basics:understanding the reason for each stencil material process, focusing on detailed finishes and a disciplined aperture design process, maintaining original designs, and making the correctly designed apertures to control the paste deposition. The test results drove us to focus the efforts on the aperture walls In this paper we will demonstrate with lab tests SMT process results howthe improved paste release results in improved SMT print process performance and its positive impact on SPI yields and EOL performance.
Technical Library | 2011-06-29 14:44:52.0
High yields in the stencil printing process are essential to a profitable SMT assembly operation. But as circuit complexity continues to increase, so do the challenges of maintaining a successful solder paste deposition process. To help assemblers address
Technical Library | 2008-03-03 19:43:53.0
Solder pastes are key materials in surface mount technology (SMT) for assembly of printed circuit boards (PCBs). Introduction of lead-free has placed new demands on materials and processes in SMT, requiring materials and process engineers to adopt to lead free whilst ensuring process yields stay at the highest possible levels. Key is the solder paste, a material of great complexity involving engineering sciences, metallurgy, chemistry and physics. This article helps those working with solder pastes improve their understanding of this key material.
Technical Library | 2014-08-19 15:39:13.0
Understanding warpage of package attach locations on PCBs under reflow temperature conditions is critical in surface mount technology. A new industry standard, IPC 9641, addresses this topic directly for the first time as an international standard.This paper begins by summarizing the sections of the IPC 9641 standard, including, measurement equipment selection, test setup and methodology, and accuracy verification. The paper goes further to discuss practical implementation of the IPC 9641 standards. Key advantages and disadvantages between available warpage measurement methods are highlighted. Choosing the correct measurement technique depends on requirements for warpage resolution, data density, measurement volume, and data correlation. From industry experience, best practice recommendations are made on warpage management of PCB land areas, covering how to setup, run, analyze, and report on local area PCB warpage.The release of IPC 9641 shows that flatness over temperature of the package land area on the PCB is critical to the SMT industry. Furthermore, compatibility of shapes between attaching surfaces in SMT, like a package and PCB, will be critical to product yield and quality in years to come.
Technical Library | 2023-06-12 19:18:24.0
As any new technology emerges, increasing levels of refinement are required to facilitate the mainstream implementation and continual improvement processes. In the case of lead-free processing, the initial hurdles of alloy and chemistry selection are cleared on the first level, providing a base process. The understanding gained from early work on the base process leads to the next level of refinement in optimizing the primary factors that influence yield. These factors may include thermal profiles, PWB surface finishes, component metallization, solder mask selection or stencil design.
Technical Library | 2023-06-12 19:46:10.0
Solder paste printing is understood to be the leading contributor of defects in the electronics assembly process. Because yield accounts for such a large percentage of the margin, the greatest opportunity to improve profitability in the assembly of most electronics can be gained by reducing or eliminating solder defects. This article examines process adjustments made through stencil design that correct a misalignment situation between the PCB and stencil, leading to a 43% reduction in assembly defects. Examples of each are found in Table 1.
Technical Library | 2013-11-21 12:01:11.0
Previous experimentation on a highly miniaturized and densely populated SMT assembly revealed the optimum stencil alloy and flux-repellent coating for its stencil printing process. Production implementation of the materials that were identified in the study resulted in approximately 5% print yield improvement across all assemblies throughout the operation, validating the results of the initial tests. A new set of studies was launched to focus on the materials themselves, with the purpose of optimizing their performance on the assembly line (...) Results of the prior tests are reviewed, and the new test vehicle, experimental setup and results are presented and discussed.
Technical Library | 2023-06-12 19:00:21.0
The SMT print process is now very mature and well understood. However as consumers continually push for new electronic products, with increased functionality and smaller form factor, the boundaries of the whole assembly process are continually being challenged. Miniaturisation raises a number of issues for the stencil printing process. How small can we print? What are the tightest pitches? Can we print small deposits next too large for high mix technology assemblies? How closely can we place components for high density products? ...And then on top of this, how can we satisfy some of the cost pressures through the whole supply chain and improve yield in the production process! Today we are operating close to the limits of the stencil printing process. The area ratio rule (the relationship between stencil aperture opening and aperture surface area) fundamentally dictates what can and cannot be achieved in a print process. For next generation components and assembly processes these established rules need to be broken! New stencil printing techniques are becoming available which address some of these challenges. Active squeegees have been shown to push area ratio limits to new boundaries, permitting printing for next generation 0.3CSP technology. Results also indicate there are potential yield benefits for today's leading edge components as well. Stencil coatings are also showing promise. In tests performed to date it is becoming apparent that certain coatings can provide higher yield processing by extending the number of prints that can be performed in-between stencil cleans during a print process. Preliminary test results relating to the stencil coating technology and how they impact miniaturisation and high yield processing will be presented.
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