This study evaluated three step stencil technologies - chemically etched, laser welded, and micro-machined - to determine their effectiveness in applying different volumes of solder paste. Measurements found that etched steps were deeper than nominal values, while welded and machined steps were closer to targets. Across all technologies, solder paste volumes were higher closer to step edges (10-20 mils) than further away (30-50 mils), indicating squeegee difficulty. A fluoropolymer nano-coating slightly increased volumes. Overall, the technologies were viable for step stencils, but further investigation is needed to differentiate their performance.
THE INFLUENCE OF MICROSTRUCTURE IN THE HOMOGENEITY OF HARDNESS STANDARD BLOCKSTito Livio M. Cardoso
The paper presents results of studies microhardness standard commercial blocks, indicating that a strict control of grain size is required in its manufacture punctual to avoid uncertainties in the measurements for calibration of durometers
descrição da publicação: Simposio Brasileiro de Estruturologia
data da publicação: 1998
Prediction of Draw Ratio in Deep Drawing through Software Simulationsirjes
Deep drawing process is one of the most commonly used Metal Forming Process within the
industrial field. Different analytical, numerical, empirical and experimental methods have been developed in
order to analyze it. In this paper deep drawing process with varying punch and die geometries are analysed. This
work reports on the stages of finite element analysis (FEA) and simulations of a Deep drawing process. The
obtained result allows to find optimum draw ratios in deep drawing.
THE INFLUENCE OF MICROSTRUCTURE IN THE HOMOGENEITY OF HARDNESS STANDARD BLOCKSTito Livio M. Cardoso
The paper presents results of studies microhardness standard commercial blocks, indicating that a strict control of grain size is required in its manufacture punctual to avoid uncertainties in the measurements for calibration of durometers
descrição da publicação: Simposio Brasileiro de Estruturologia
data da publicação: 1998
Prediction of Draw Ratio in Deep Drawing through Software Simulationsirjes
Deep drawing process is one of the most commonly used Metal Forming Process within the
industrial field. Different analytical, numerical, empirical and experimental methods have been developed in
order to analyze it. In this paper deep drawing process with varying punch and die geometries are analysed. This
work reports on the stages of finite element analysis (FEA) and simulations of a Deep drawing process. The
obtained result allows to find optimum draw ratios in deep drawing.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
The objective of any rework process is to duplicate as closely as possible the original manufacturing
process while not disturbing neighboring components while still meeting the original specifications and
assembly criteria of the PCB .
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
The objective of any rework process is to duplicate as closely as possible the original manufacturing
process while not disturbing neighboring components while still meeting the original specifications and
assembly criteria of the PCB .
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
Parametric Analysis and Optimization of Turning Operation by Using Taguchi Ap...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
This paper will present a rigorous method for evaluating the performance and economic benefits of solder paste stencil nano-coatings. Criterion such as underside cleaning, bridging, transfer efficiency across SARs, solder paste deposit geometry, post-print cleaning, and abrasion resistance of the coating, will all be considered and weighted. Performance of currently available coatings will be compared. A discussion of the economic impact on current and future SMT design will be included.
INCREASING THE TRANSISTOR COUNT BY CONSTRUCTING A TWO-LAYER CRYSTAL SQUARE ON...ijcsit
According to the Moore’s law, the number of transistor should be doubled every 18 to 24 months. The main
factors of increasing the number of transistor are: a density and a die size. Each of them has a serious physical limitation; the first one “density” may be reached “Zero” after few years, which causes limitation
in performance and speed of a microprocessor, the second one “die size” cannot be increased every 2
years, it must be fixed for several years, otherwise it will affect the economical side. This article aims to
increase the number of transistors, which increase the performance and the speed of the microprocessor
without or with a little bit increasing the die size, by constructing a two-layer crystal square for transistors,
which allows increasing the number of transistors two additional times. By applying the new approach the
number of transistors in a single chip will be approximately doubled every 24 months according to Moore’s
Law without changing rapidly the size of a chip (length and width), only the height of a chip must be
changed for putting the two layers.
Design & Development of Injection Mold Using Flow Analysis and Higher End Des...paperpublications3
Abstract: In past Mold Design process was time taking as well as hectic. At first Drawing board, then 2D software’s were used after which patterns were made. But in this case the results were not considerable most of the times. Thus the design to market time increased immensely and also project cost required was on a higher side.
Due to the technological advancement the process of Mold Design has fastened and also the results are considerable. With the help of 3D software we can create Parametric Design, Which are editable. Also we can look at number of possibilities for designing a mold. Most importantly the process of Drawing Creation for Mold Design becomes very easy. In a 3D software Visualization of our design is easy possible. Thus our project aims at the awareness of developments of the new age technology of 3D CAD/Mold Wizard for Mold Design.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Quality defects in TMT Bars, Possible causes and Potential Solutions.PrashantGoswami42
Maintaining high-quality standards in the production of TMT bars is crucial for ensuring structural integrity in construction. Addressing common defects through careful monitoring, standardized processes, and advanced technology can significantly improve the quality of TMT bars. Continuous training and adherence to quality control measures will also play a pivotal role in minimizing these defects.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
1. Step Stencil Technologies and Their Effect on the SMT Printing Process
Greg Smith
FCT Assembly
Greeley, CO, USA
gsmith@fctassembly.com
Tony Lentz
FCT Assembly
Greeley, CO, USA
tlentz@fctassembly.com
Bill Kunkle
Metal Etching Technology (MET)
Lumberton, NJ, USA
wkunkle@metstencil.com
ABSTRACT
It is a common fact that the print process is one of the most
critical elements in SMT production and many of today’s
assemblies include both miniature components such as
0201’s, Micro-BGA’s, LGA’s and QFN’s as well as large
components such as large connectors on the same assembly.
Printing the proper volume of paste on these assemblies is
not always possible by adjusting the apertures on single
level stencils. As a result, manufacturers are finding that
“Step Stencils” allow them to apply the correct amount of
paste to different components on the same assembly with
excellent first pass yields.
The intent of this study is to evaluate three step stencil
technologies and measure their effectiveness in applying
different volumes of paste on the same board during the
printing process. The step technologies to be evaluated are
chemically etched, laser welded and micro-machined. The
step down areas for each technology will be physically
measured for accuracy. At a given squeegee speed and
pressure, the distance from step edge to nearest aperture will
be varied. Also solder paste volume in step down areas for
each technology will be measured. Finally, the addition of a
Fluoro Polymer Nano-Coating will be applied to the contact
side of the stencil and in the aperture walls. Solder paste
volumes will be measured and compared to the uncoated
step technologies.
This paper summarizes the results of this study with respect
to the variables tested. Stencil design recommendations will
be made with the intent of eliminating defects in the solder
paste printing process when applying different volumes of
paste with step stencil technologies. As component
miniaturization continues and larger components remain,
advancements in step technologies by stencil manufacturers
continue to improve.
Keywords: SMT stencil, stencil design, step stencils, laser
welded steps, etched steps, machined steps, solder paste
printing, aperture clogging.
INTRODUCTION
Components such as Quad Flat No Lead (QFN’s), Land
Grid Array (LGA’s), Micro Ball Grid Array (Micro
BGA’s), 0201’s and even 01005’s continue to push
manufacturers to use thinner stencil foils to apply the correct
volume of paste onto their boards, but larger components
such as edge connectors still require larger paste volumes.
Step stencils have been used to accomplish this for many
years. Historically, the primary method for producing these
step stencils has been using a photochemical etching
process. Recently, new methods of manufacturing step
stencils have emerged including both laser welding and
micro-machining.
Photochemical etching is an established process and has
been around for decades. It is a subtractive process and is
very similar to the process used to etch Printed Wiring
Boards (PWBs). The stainless steel stencil foil is coated
with a photo-resist, imaged using a photographic process
and developed leaving the resist to protect any areas that
will not be reduced in thickness or etched. The foil is
placed into an etching machine where chemical etchant is
sprayed onto the stencil which dissolves the stainless steel
foil until the correct thickness is achieved. Once the desired
stencil thickness is achieved, the photo resist is removed.
The depth of the etched or stepped areas using this process
is dependent on the time that the stencil is exposed to the
etching chemistry. The chemical etching process is shown
below (Figure 1).
2. Figure 1: Chemical Etching Process to Create a Step
Stencil.
The laser welding process takes stencil foils of different
thicknesses and welds them together. There is no chemical
etching involved, only laser cutting and laser welding. The
step openings are cut out of the first stencil. The
corresponding step areas are cut out of a second stencil foil
of the desired thickness. The step pieces are placed into the
openings of the first stencil. Then the pieces are laser
welded into place. The thickness of the step area is
determined by the thickness of the steel used. The laser
welding process is shown below (Figure 2).
Figure 2: The Laser Welding Process to Create a Step
Stencil.
The micro-machining process is a subtractive process
similar to the etching process, but no chemicals are used.
The micro-machining process uses a very specialized
computer numerical controlled (CNC) milling machine to
remove very small amounts of material at a time. The
micro-machining process is shown below (Figure 3)
Figure 3: The Micro-Machining Process to Create a Step
Stencil.
These three processes for creating step stencils result in
different textures within the stepped area. The textures of
the step stencils are shown below (Figure 4).
Figure 4: Textures of Step Areas for the Three Step
Technologies.
EXPERIMENTAL METHODOLOGY
A step stencil design was created with step down pockets of
varying thicknesses. The base stencil thickness was 4.0
mils (101.6 microns) and the step down pockets were 3.5
mils (88.9 microns), 3.0 mils (76.2 microns), 2.5 mils (63.5
microns), and 2.0 mils (50.8 microns) thick. Each step area
was 1 inch square (25.4 mm) and the step design is shown
below (Figure 5).
Figure 5: Step Down Pocket Design.
The thicknesses of each step pocket were measured using a
FARO arm device. The measurements for each step
technology were compared and contrasted.
An aperture pattern was created for the following
components: 03015 Metric, 01005, 0.3 mm BGA, 0.4 mm
BGA, and 0.5 mm pitch QFNs. Apertures for each
component were cut at varying distances from the step
edges; 10, 20, 30, 40, and 50 mils. The intention was to
determine how close solder paste could be printed to the
step edge for each step stencil technology. Apertures were
also cut into the center of each step area for comparison.
The aperture layout is shown below (Figure 6)
3. Figure 6: Step Stencil Aperture Design.
Each stencil was made with two sets of steps and apertures.
One set of steps and apertures were coated with a Fluoro-
Polymer Nano (FPN) coating (Figure 7).
Figure 7: Step Stencil Contact Side with FPN Nano-
Coating.
The effects of the FPN coating were compared to the
uncoated part of the stencil on printing of solder paste.
A 10 print study was run on each step stencil using a
popular no clean, SAC305 Type 4 solder paste. The circuit
boards used were bare copper clad material 0.062” (1.57
mm) thick. The printer used was a DEK Horizon 02i. The
printer parameters are shown below (Table 1).
Table 1: Solder Paste Printer Parameters.
Parameter Value
Squeegee Length 300 mm
Squeegee Pressure 0.18 kg/cm (5.4 kg)
Squeegee Speed 30 mm/sec
Squeegee Angle 60 degrees
Separation Speed 1.0 mm/sec
Cleaning Cycle W/V/D every print
Cleaning Solvent Isopropanol (IPA)
Solder Paste NC SAC305 T4
The solder paste volumes were measured using a solder
paste inspection system (SPI). The solder paste volume data
was analyzed using statistical analysis software and the
results are presented in this paper.
RESULTS
Step Stencil Thickness Measurements
Measurements were taken in each step area for each
technology. The 3.5 mil step area was not included due to
issues with the measurement data. Thickness measurement
data is shown below (Table 2).
Table 2: Step Down Thicknesses for Each Step Stencil.
Step
Thickness
(mils)
Step
Depth
(mils)
Etched –
Depth /
STDev
(mils)
Welded -
Depth /
STDev
(mils)
Machined
- Depth /
STDev
(mils)
2.0 2.0 2.36 / 0.11 2.08 / 0.19 2.01 / 0.17
2.5 1.5 1.69 / 0.16 1.60 / 0.18 1.25 / 0.15
3.0 1.0 1.15 / 0.19 0.97 / 0.18 1.08 / 0.17
In general, the chemical etching process created deeper step
downs than the nominal value, and the welding and
machining processes created steps that are closer to the
target depth. The standard deviations of step depth are an
indication of flatness or roughness in the step areas. The
chemical etching process produces a surface that is rougher
than the original surface (Figure 4). The welding process
involves fixturing a stencil blank into the step area and the
blank may not sit perfectly flat as it is welded. The
machining process leaves striations on the surface as the
cutting tool removes material. Overall, the standard
deviations are very similar for each technology.
Solder Paste Printing Data – Etched Stencil
The solder paste volume box plots for the 3.0 mil, 2.5 mil,
and 2.0 mil thick etched steps are shown below (Figures 8,
9, and 10 respectively). These are broken out by distance
from step edge, aperture size and nano-coating.
Figure 8: Solder Paste Volumes for the 3.0 mil Etched
Step.
4. Figure 9: Solder Paste Volumes for the 2.5 mil Etched
Step.
Figure 10: Solder Paste Volumes for the 2.0 mil Etched
Step.
In general, the larger apertures which are 9.8 x 35.4 mils in
size give higher printed solder paste volumes. The smaller
aperture sizes show some differences in solder paste
volume. Tukey-Kramer Honest Significant Difference
(HSD) testing shows that most of these variations are
statistically similar. This means that there is very little
difference in printed solder paste volume from 10 to 50 mils
from the step edge. There is one exception to this (Figure
11).
Connecting Letters Report
Level Mean
10 A 839.52500
20 A 823.35000
40 A B 798.30000
30 A B 796.65000
50 B 776.22500
Figure 11: Tukey-Kramer HSD Analysis for the FPN
Coated, Etched 3.0 mil Step and the 9.8 x 35.4 Aperture.
The printed solder paste volume is higher for the 10 and 20
mil distances than the 50 mil distance. This indicates that
the squeegee is not able to conform into the step pocket and
squeegee the paste cleanly away from the surface. The
same Tukey HSD analysis is true for the uncoated version
of this step and aperture size.
Figure 12: Etched 3.0 mil Step After 1 Print
It is easy to see solder paste residue left near the step wall
after printing. This seems to correspond to higher printed
paste volumes.
Solder Paste Printing Data – Welded Stencil
The solder paste volume box plots for the 3.0 mil, 2.5 mil,
and 2.0 mil thick welded steps are shown below (Figures 13,
14, and 15). These are broken out by distance from step
edge, aperture size and nano-coating.
Figure 13: Solder Paste Volumes for the 3.0 mil Welded
Step.
Figure 14: Solder Paste Volumes for the 2.5 mil Welded
Step.
5. Figure 15: Solder Paste Volumes for the 2.0 mil Welded
Step.
The printed solder paste volume did not vary much from 10
mils to 50 mils away from the step edge regardless of
welded step thickness. This is very similar to the results
seen with the etched steps. Tukey-Kramer HSD testing
shows some interesting results (Figure 16).
Connecting Letters Report
Level Mean
10 A 1015.3250
20 A B 988.8000
30 A B C 954.1750
40 B C 916.4750
50 C 891.8500
Figure 16: Tukey-Kramer HSD Analysis for the Uncoated,
Welded 2.5 mil Step and the 9.8 x 35.4 Aperture.
In this case, the printed solder paste volume at the 10 mil
distance is significantly higher than the 40 and 50 mil
distances. The printed solder paste volume is significantly
higher at the 20 mil distance than then 50 mil distance.
Again this indicates that the squeegee could not conform
down into the step to remove all of the solder paste from the
surface of the stencil during printing. This was also true for
the FPN coated version of the 3.0 mil welded step and the
same aperture size.
Solder Paste Printing Data – Machined Stencil
The solder paste volume box plots for the 3.0 mil, 2.5 mil,
and 2.0 mil thick machined steps are shown below (Figures
17, 18, and 19). These are broken out by distance from step
edge, aperture size and nano-coating.
Figure 17: Solder Paste Volumes for the 3.0 mil Machined
Step.
Figure 18: Solder Paste Volumes for the 2.5 mil Machined
Step.
Figure 19: Solder Paste Volumes for the 2.0 mil Machined
Step.
The printed solder paste volume did not vary much from 10
mils to 50 mils away from the step edge regardless of
machined step thickness. This is very similar to the results
seen with the etched and welded steps. Tukey-Kramer HSD
testing shows some significant differences in the results
(Figure 20).
Connecting Letters Report
Level Mean
10 A 116.82500
20 A 113.92500
6. Level Mean
40 B 104.20000
30 B 103.72500
50 B 101.42500
Figure 20: Tukey-Kramer HSD Analysis for the Uncoated,
Machined 2.0 mil Step and the 8 x 9 Aperture.
This Tukey HSD analysis shows that the printed solder
paste volume is significantly higher at the 10 and 20 mil
distances than the 30, 40, and 50 mil distances. This is also
true for the 9.8 x 35.4 mil aperture with 2.0 mil and 2.5 mil
machined step thicknesses.
CONCLUSIONS
Chemical etching, laser welding, and micro-machining are
each valid methods of producing step stencils. Each process
produces different step surfaces.
Regardless of the technology used to produce the step,
solder paste volumes for the QFN apertures tend to be
higher 10 to 20 mils from the step edge than 30 to 50 mils
away. These increased solder paste volumes could lead to
shorts with aperture designs for the tested QFN component
designs. It would be possible to place apertures this size 30
mils from the step edge and obtain an acceptable solderpaste
volume. The smaller 8, 8x9, and 10 mil apertures gave
statistically similar solder paste volumes from 10 to 50 mils
away from the step edge. Although further investigation is
needed, the data shows that small aperture components can
be placed as close as 10 mils from the step edge and still
obtain acceptable print volumes.
The FPN coating showed a slight increase in volume across
all apertures measured. When printing these small
apertures, it is recommended to apply a FPN coating.
It is apparent that these step stencil technologies bear further
investigation in order to differentiate between them.
FUTURE WORK
Testing is ongoing with these three step stencil
technologies. Solder paste volumes at the center of the step
area will be compared to volumes near the step edge. The
solder paste volumes from a single level stencil of the same
thickness as the step down area will be compared and
contrasted to the volumes in the step etched stencils. The
printed solder paste volume from apertures oriented
horizontal to the squeegee will be compared to apertures
oriented vertical to the squeegee within step areas.
Squeegee pressure and speed will be varied and the effects
on solder paste volume will be studied. Finally, we plan to
increase the number of boards printed to obtain a larger set
of data to expand on these findings.
ACKNOWLEDGEMENTS
We appreciate the support of MET for providing the welded
step stencils for this investigation. We also appreciate the
support of Fine Line Stencil who provided the etched and
machined step stencils and the nano-coating.
REFERENCES
None