This paper discusses some of the new challenges
associated with MSD Control in PCB assembly
plants and offers a solution to reduce manufacturing
costs and improve quality by automating this critical
aspect of quality control.
The Final assembly and packaging area experiences similar integration issues as the Printed Wiring Board –
PWB manufacturing industry. Communications between production equipment is based on different standards
and many vendors have released their own proprietary specifications. This situation entails considerable
integration costs.
Most of the equipment suppliers in final assembly and packaging have implemented information systems using
proprietary specifications. Some of the Original Electronics Manufactures (OEM) and Electronics
Manufacturing Service companies (EMS) request SECS/GEM interfaces. However,SECS/GEM is not always
suitable,especially in those cases when the equipment has moderate functionality. The final assembly and
packaging area is calling for an explicit and scalable solution.
The development of an IPC-2546 section dedicated to final assembly and packaging will improve the
information flow integration. Leading suppliers drive,by consensus,the development of this sectional standard.
In addition,control issues (related to IPC 2556) were kept in mind from the very beginning of discussions.
CAMX(+) standards are developed based on the PWB manufacturing needs. In case of final assembly and
packaging the environment and conceptual design differs from PWB. New levels of abstraction are needed. A
representative case for these differences is the transportation system using pallets (containers). In addition the
route of the product is not typically straightforward,but branching is a common situation creating extra needs
for the controls.
A test environment was built up in order to develop,test and illustrate these standards. The environment uses a
pallet-based transportation system for interconnecting manual workstations and robotized cells.
The tests indicate the applicability of CAMX standards in final assembly and packaging area. When a common
language is used,the Plug & Assemble ideology is achieved providing lower costs. Production equipment users
are able to select the best-in-class machines and integrate them into multi-vendor systems. Finally,the use of
same messaging format provides a homogenous environment from equipment through the enterprise to B2B.
All manufacturers in the printed circuit board (PCB) industry have experienced lack of reliability,maintenance,and
performance problems with their machines. These challenges decrease manufacturing productivity and increase
costs. Addressing these manufacturing challenges requires the right process information to be available to the
engineering team. Currently,managers and process engineers either have insufficient or no data to measure the
impact of these issues in order to make improvements. It is essential for the industry to use the adopted equipment
communication standards that provide the basic framework to gather the data necessary to dramatically improve
equipment utilization.
The industry has been using the Semiconductor Equipment Communication Standard/Generic Model for
Communications and Control of SEMI Equipment (SECS/GEM) standards that allow manufacturers to gather data
directly from the equipment. Several factories that have used SECS/GEM have published their remarkable process
improvements. Experience demonstrates that SECS/GEM is most reliable when equipment suppliers use robust
software products created by third party developers to implement the interface and provide it as a standard feature.
IPC is defining new communication standards for retrieving information from the equipment based on Extensible
Markup Language (XML),a common and popular communication language. The new standards promise facilitated
access to process information in order to increase equipment efficiency and reduce costs.
Equipment suppliers are already required to support the SECS/GEM standard for certain customers. Today,machine
suppliers are on the verge of also supporting the IPC XML standards as manufacturers adopt the new standards.
Suppliers and factories should avoid developing non-standard protocols to implement equipment communication
interfaces and instead use the existing standards as a baseline and implement special messages to fulfill any
additional requirements.
The IPC 2501 Web Service Definition for the exchange of XML data provides an XML middleware integration
environment that enables the deployment of IPC Computer Aided Manufacturing using XML (CAMX) -based
standards. A performance test was run in an actual production facility to determine the applicability of an XML
web-native message broker utilizing XML,HTTP,SOAP,and MIME attachments for transporting large
volumes of data. Performance tests on the Georgia Tech developed IPC 2501 test bed prototype determined the
maximum throughput and maximum number of clients and subscribers to data from in-circuit testers.
Configuration and administration requirements of the message broker in the factory environment are reviewed
from the perspective of process engineers and supervisory shop floor personnel. Finally,the web services
impact on faster and more flexible shop floor equipment integration is summarized based on the Motorola
factory experience.
Yield and defect levels in the manufacturing of high-complexity and high-reliability Printed Circuit Board
Assemblies (PCBAs) are extremely sensitive to variations in the process,component quality and workmanship. Any
deviation from expected targets needs to be investigated,not only after the identification of the manufacturing issue,
but also proactively before the issue becomes more pronounced. Traditional control tools such as yield tracking
and/or Statistical Process Control (SPC) capture deviations in the overall defect levels but they have no knowledge
what specific types of defects to monitor. In addition,the discontinuous nature of production build schedules and
fluctuating product volumes in the high-mix and low-volume electronics manufacturing domains can render SPC
ineffective. This research proposes a new methodology that interprets and analyzes defect and yield data to detect
“maverick lots”. These defect clusters are delineated from large volumes of production data in a high-complexity
PCBA facility that contains accurate information mixed indistinguishably with “noisy” data. For this approach,
historical information from prior analysis is used to distinguish deviations and trends from the current data. This
procedure is generic in nature and could be simultaneously executed automatically at several appraisal points on the
manufacturing line. This methodology has been used effectively in the Endicott Interconnect In-Circuit Test process
and has identified shifts in our Complex Assembly processes that may have gone undetected using other techniques.
Numerous studies and anecdotal data suggest that most SMT assembly lines are not optimized. This situation is true
whether one looks at the individual processes,such as stencil printing or placement,or the entire SMT assembly line
as a whole. This lack of optimization causes significant losses in profits. Most managers and process engineers are
aware of this general situation,but feel overwhelmed with deciding how to address the concern.
In light of this need,we have developed an Excel® based software program. This program asks the user a series of
questions. The answers to the questions are then analyzed by the program. The output is an assessment of the users
SMT Process and a recommended approach to developing a continuous improvement plan. The assessment ranks
the user in categories that relate to specific processes,such as reflow or printing and suggests areas of improvement.
More importantly,the assessment determines the competitiveness of the assembler’s entire SMT process and offers
constructive criticism. SMT “systems” topics such as statistical process control (SPC),designed experiments (DOE),
and design for manufacturability (DFM) are included in the assessment.
The entire assessment process takes most assemblers less than one hour and the results can be invaluable in
developing an effective continuous improvement process.
The software will be given free to interested readers. Contact the authors for copies of the software and an
instruction guide.
Wave soldering fluxes are currently used in hand soldering operations as a matter of course and with little
regard for flux deposition amounts. This use has led to the investigation of fluxes used in hand soldering
applications and the effect on long term reliability of manufactured assemblies. The work presented here
explores the reliability impact that fully,partially and entrapped wave flux residues from hand soldering repair
operations can have on electronic assemblies. Standard IPC Surface Insulation Resistance (SIR) testing and
testing with a different environmental condition of 40°C at 88% R.H. were performed to determine reliability.
During hand soldering operations,liquid flux can become entrapped under nearby components or flooded onto
areas of the assembly that may not be heated. The results of SIR testing show that if fluxes are used properly in
controlled amounts there is no associated reliability impact. However,some fluxes if applied in excessive
amounts or entrapped were shown to cause reliability failures. In particular these problems occurred with noclean
tacky soldering flux (TSF),rosin activated (RA) and no-clean,low solids fluxes. During hand soldering
operations flux deposition should be carefully controlled to reduce the potential for entrapped and excessive
flux residues that can lead to long term reliability problems.
Surface Mount Rework systems have evolved into sophisticated thermal processing tools with the ability to
accurately mimic original reflow oven profiles at a localized rework site. Features such as automated profile
generation allow the user to quickly define workable profiles for a wide variety of applications. However,many of
today’s applications demand more carefully crafted profiles than can be achieved using traditional methods.
Sensitive components such as optical devices,connectors,and certain package types,to name a few,have specific
requirements and limitations that go far beyond the typical solder joint time-temperature profile. Elevated
temperatures of lead free processes further amplify thermal management issues.
Rules Based Thermal Profiling allows automated profile generation with a combination of parameters that that are
set to meet each situation. Multiple criteria may be specified and prioritized to yield the most reliable process for
reworking sensitive components and assemblies.
SMT rework machines are vital tools to many production engineers. They can be used to correct process errors and
repair test failures. They can also be used to service and upgrade products returned from the field.
Rework machines come in many forms – from the basic hot air type to complex laser and infrared heating units.
Whichever form they take,they have a common task - to deliver focused heat for the removal,replacement or
repositioning of SMT electronic components.
This paper discusses the need to control these systems on a daily basis. It addresses current methods and will offer
some alternatives and improvements. Finally,it suggests a statistical regime that will ensure machines are operating
in a controlled manner.
Current circuit board designs,particularly those in telecommunications,are so densely populated that they do not
provide enough clearance between SMT components and through-hole components to allow assemblers to use
traditional soldering methods. Clearances of less than 0.5mm (0.020”) are typical in these designs. To provide
assemblers with robust,repeatable selective soldering processes,equipment manufacturers have been challenged not
only to miniaturize the traditional flux-preheat-wave process,but also to add sophisticated positioning,motion
control,and optical recognition systems. This paper describes the many selective soldering challenges encountered
by assemblers,the current state of the art in automated selective soldering,and the future of this technology.