Technical Library | 2010-03-23 11:50:22.0
This document discuss how to design SMT stencil base on IPC-7525. Introduction: PCBA (Printed Circuit Board Assembly) is a segment of printed circuit board technology. This segment of printed circuit board industry is concentrated in assemble all the pieces of electronic industry to one piece before output them to market. This segment covers: interconnection technology, package design technology, system integration technology, board and system test technology
Technical Library | 2020-04-14 15:56:32.0
This paper will focus on the application requirements of solder printing small aperture designs, concentrating on 008004 (inch) / 0201 (metric) size components, and the results of a design of experiment printing these challenging apertures. As Moore's law continues to be applied to component miniaturization, the next installment of reduced packaging has arrived in the form of the 008004/0201 for resistors and capacitors. Component size roughly the size of a grain of sand presents specific challenges to the solder printing process. To address these challenges, each aspect of the printing process will need be examined. This includes essential machine requirements, including correct squeegee blades, tooling support, and calibrations, to meet the demanding specifications. The correct match and design of materials will be addressed, focusing on the stencil and substrate design along with solder paste and cleaning solvent requirements. A design of experiment will be reviewed that applies the machine and materials discussed, including the printer and Solder Paste Inspection (SPI) setup and the specific machine parameters used. The results of these DOE's will then be closely examined.
Technical Library | 2019-06-12 10:33:58.0
The success of ball grid array (BGA) placement on electronic assemblies is as much a matter of proper preparation and planning, as it is technique. In some designs, it is more appropriate to apply BGAs using a rework station that isolates the placement of the device, without subjecting the entire assembly to thermal reflow. This is especially beneficial in board constructions where the number of BGAs is limited, and the application of the solder paste is difficult, due to small pitch features that stretch the limitation of the stencil construction. Another application for rework stations, involves very large and thermally conductive BGAs, which will not uniformly reflow with other components on the assembly, and may require special process parameters for their proper placement. The most common use of BGA rework stations are for assemblies requiring BGA removal and replacements due to failures in the initial assembly stage.
Technical Library | 2019-05-29 23:10:30.0
There are times when a PCB prototype needs to be built quickly to test out a design. In such cases where it is known early on that there will be multiple iterations or that a "one and done" assembly will be made that there will be some SMT assemblers who choose to hand print solder paste onto the board using a "frameless" stencil. In such cases where hand printing is used, the consistency of the printing technique has typically been in question. Furthermore, the effectiveness of both the nanocoatings as well as the higher end stainless steel materials, which have been heretofore studied in controlled printing environments, will be evaluated for their impact on the hand printing process.The purpose of the study was to determine the effectiveness of select nanocoating materials as well as certain high end stainless steel stencil materials as they relate to the manual SMT printing process. A variety of nanocoatings were applied to SMT metal stencils and solder paste volume measurements were taken to compare the effectiveness.
Technical Library | 2023-07-25 16:50:02.0
Some of the new handheld communication devices offer real challenges to the paste printing process. Normally, there are very small devices like 01005 chip components as well as 0.3 mm pitch uBGA along with other devices that require higher deposits of solder paste. Surface mount connectors or RF shields with coplanarity issues fall into this category. Aperture sizes for the small devices require a stencil thickness in the 50 to 75 um (2-3 mils) range for effective paste transfer whereas the RF shield and SMT connector would like at least 150 um (6 mils) paste height. Spacing is too small to use normal step stencils. This paper will explore a different type of step stencil for this application; a "Two-Print Stencil Process" step stencil. Here is a brief description of a "Two-Print Stencil Process". A 50 to 75 um (2-3 mils) stencil is used to print solder paste for the 01005, 0.3 mm pitch uBGA and other fine pitch components. While this paste is still wet a second in-line stencil printer is used to print all other components using a second thicker stencil. This second stencil has relief pockets on the contact side of the stencil any paste was printed with the first stencil. Design guidelines for minimum keep-out distances between the relief step, the fine pitch apertures, and the RF Shields apertures as well relief pocket height clearance of the paste printed by the first print stencil will be provided.
Technical Library | 2014-03-13 15:25:01.0
A student competition paper at Budapest University of Technology And Economics, Department of Electronics Technology gives background, covers stencil design and discusses stencils intended for pin in paste application. The stencil applied for depositing the solder paste is a thin, 75–200 µm thick metal foil, on which apertures are formed according to the solder pads on the printed circuit board. Stencil printing provides a fast, mass solder paste deposition process; relatively expensive, appropriate and recommended for mass production.
Technical Library | 2007-12-13 17:03:02.0
Printer-hosted processes for solder ball placement are now widely used for package technologies ranging from BGAs using ball diameters above 750μm to the latest WL-CSPs demanding 250μm diameter. This broadening spectrum of applications brings more choices in terms of stencil design rules and production methodologies.
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 | 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 | 2023-06-12 18:52:18.0
This paper will review stencil design requirements for printing solder paste around and in through-hole pads / openings. There is much interest in this procedure since full implementation allows the placement of both through-hole components as well as SMD's and the subsequent reflow of both simultaneously. This in turn eliminates the need to wave solder or hand solder through-hole components.
