Technical Library | 2019-10-10 00:26:28.0
Voids are a plague to our electronics and must be eliminated! Over the last few years we have studied voiding in solder joints and published three technical papers on methods to "Fill the Void." This paper is part four of this series. The focus of this work is to mitigate voids for via in pad circuit board designs. Via holes in Quad Flat No-Lead (QFN) thermal pads create voiding issues. Gasses can come out of via holes and rise into the solder joint creating voids. Solder can also flow down into the via holes creating gaps in the solder joint. One method of preventing this is via plugging. Via holes can be plugged, capped, or left open. These via plugging options were compared and contrasted to each other with respect to voiding. Another method of minimizing voiding is through solder paste stencil design. Solder paste can be printed around the via holes with gas escape routes. This prevents gasses from via holes from being trapped in the solder joint. Several stencil designs were tested and voiding performance compared and contrasted. In many cases voiding will be reduced only if a combination of mitigation strategies are used. Recommendations for combinations of via hole plugging and stencil design are given. The aim of this paper is to help the reader to "Fill the Void."
Technical Library | 2021-11-17 18:53:50.0
The demand for product miniaturization, especially in the handheld device area, continues to challenge the board assembly industry. The desire to incorporate more functionality while making the product smaller continues to push board design to its limit. It is not uncommon to find boards with castle-like components right next to miniature components. This type of board poses a special challenge to the board assemblers as it requires a wide range of paste volume to satisfy both small and large components. One way to address the printing challenge is to use creative stencil design to meet the solder paste requirement for both large and small components. ... The most important attribute of a stencil is its release characteristic. In other words, how well the paste releases from the aperture. The paste release, in turn, depends on the surface characteristics of the aperture wall and stencil foil. The recent introduction of new technology, nano-coating for both stencil and squeegee blades, has drawn the attention of many researchers. As the name implies, nano-coated stencils and blades are made by a conventional method such as laser-cut or electroformed then coated with nano-functional material to alter the surface characteristics. This study will evaluate nano-coated stencils for passive component printing, including 01005.
Technical Library | 2013-06-20 14:33:12.0
With today's consumer technologies driving the need for denser and more compact devices, the assembly process for surface mounted devices has becoming increasingly more difficult. With the mixture of components requiring a broader range of print deposition volume, various techniques are in use in an attempt to ensure consistent and appropriate paste volume is achieved. Some of these techniques include step etching a stencil locally on a targeted device, promoting electroformed smooth wall nickel stencils, through to laser cutting newer grade stencil materials. This paper focuses on the relevant attributes that affect the properties of solder paste release and introduces the effects of surface free energy with respect to key elements that make up the stencil printing process.
Technical Library | 2017-04-13 16:14:27.0
The drive to reduced size and increased functionality is a constant in the world of electronic devices. In order to achieve these goals, the industry has responded with ever-smaller devices and the equipment capable of handling these devices. The evolution of BGA packages and leadless devices is pushing existing technologies to the limit of current assembly techniques and materials.As smaller components make their way into the mainstream PCB assembly market, PCB assemblers are reaching the limits of Type 3 solder paste, which is currently in use by most manufacturers.The goal of this study is to determine the impact on solder volume deposition between Type 3, Type 4 and Type 5 SAC305 alloy powder in combination with stainless steel laser cut, electroformed and the emerging laser cut nano-coated stencils. Leadless QFN and μBGA components will be the focus of the test utilizing optimized aperture designs.
Technical Library | 2017-11-03 13:39:06.0
If someone were to ask what the most important part of their favorite electronic device is, they are likely to point to the printed circuit board (PCB) responsible for making the device work before moving on to other components. From large motherboards to tiny chips, most of the technology that retail consumers take for granted comes down to a properly installed and calibrated PCB.
Technical Library | 2007-12-06 11:37:15.0
Over the past 30 years we have learned that lead has negative affects on the health of humans and seen strong legislation remove it from gasoline and paints. More recently, governments in Europe and Asia have set deadlines to remove lead from consumer electronic devices that use printed circuit boards. Currently, the ban is not being applied to high reliability applications such as military or medical devices, but we all know that will come someday soon. Likewise many believe that lead free solder is coming to wafer bump reflow and are beginning to make the transition.
Technical Library | 2020-03-19 00:23:15.0
In this study, the question was how to perform statistically reliable robust- ness tests for the non-contact drop-on-demand printing of functional fluids, such as solder paste and conductive adhesives. The goal of this study was to develop a general method for hypothesis testing when robustness tests are performed. The main problem was to determine if there was a statistical difference between two means or proportions of jet printing devices. In this study, an example of jetting quality variation was used when comparing two jet printing ejector types that differ slightly in design. We wanted to understand if the difference in ejector design can impact jetting quality by performing robustness tests. and thus answer the question, "Can jetting differences be seen between ejector design 1 and design 2"?
Technical Library | 2010-05-06 18:46:29.0
Stencil printing technology has come a long way since the early 80’s when SMT process gained importance in the electronics packaging industry. In those early days, components were fairly large, making the board design and printing process relatively simple. The current trend in product miniaturization has led to smaller and more complex board designs. This has resulted into designs with maximum area utilization of the board space. It is not uncommon, especially for hand held devices, to find components only a few millimeters from the edge of the board. The board clamping systems used in the printing process have become a significant area of concern based on the current board design trend.
Technical Library | 2016-03-17 19:09:46.0
The rapid growth of electronic devices across the globe is driving manufacturers to enhance high-speed mass production techniques in the PCB assembly arena. As manufacturers drive to reduce costs while maximizing production by expanding facilities, updating automation equipment, or implementing lean six sigma techniques, the potential to build scrap product or rework printed circuit boards increases dramatically.Manufacturers have two general paths to reduce the costs of high-speed printed circuit board assembly production. The first path is to reduce cost by focusing on high quality printing and mounting. The other, increasingly popular option is to utilize low-cost materials. In either case, the baseline must provide a consistent high-speed solder paste printing method, which considers the fill, snap-off, and cleaning processes.Building on our expertise and testing, this paper will highlight the two trains of thought with specific focus on how low-cost materials affect print performance. It will also explore technologies, which can help provide stable, high-speed screen printing.
Technical Library | 2016-08-18 15:38:09.0
The Selective Reflow Rework Process is an approach to improving the high volume rework process, increasing process capabilities and process repeatability by using a standard reflow oven of 12 zones, pick and place machinery, semi-automated printing gear and Solder Paste Inspection (SPI) implementations. This approach was able to reduce the amount of rework equipment by more than half. Our human resource requirements (indirect and direct labor) were cut by more than 50% and our rolled throughput yield increased from 68.9% to 84.14%. The Selective Reflow Rework Process is less reliant upon operators and has become a repeatable, stable rework process.
