This study is focused on using different assembly options such as dip fluxing,flux jetting and reflow encapsulate for 200-
250um pitch lead-free (SnAgCu) flip chips on FR4 substrates. The impact of different PCB surface finishes (OSP and
ENIG),was investigated from an assembly perspective. Different underfill materials including an acid anhydrate based
material and two non-acid anhydrate based materials were evaluated for compatibility with the flux and lead-free solder
bumps and process. A reflow encapsulate designed for lead-free soldering is also studied from an assembly point of view.

In this paper,a comprehensive review is provided on the optimization of soldering processes (including reflow,wave
soldering,and rework),for different component types,different PCB sizes and finishes,and in different soldering
atmospheres (air and nitrogen). The impact of key process parameters on the process yield is discussed in comparison with
the Sn-Pb soldering process,and methodologies for optimizing the lead-free soldering processes are outlined. Component
compatibility issues are also discussed.

Conductive inks and polymers based on metals were originally envisaged for quick repairs to Printed Circuit Boards (PCBs)
and semiconductor chips. Increasingly these materials are being used to replace traditional copper circuitry. Modern PCB
production suffers from high capital expenditure in process set-up and ever growing environmental and legislative
constraints,which can be replaced with quick,affordable and environmentally friendly polymer based manufacturing. New
chemistry and imaging techniques have led to the development of an increasing variety of means to deposit and pattern these
materials. Substrates include glass and FR4 as well as flexible materials such as nylon,polyester and Kapton. Conducting
inks and polymers include those based on Carbon,Silver,Copper and Gold. The resulting combination of polymer and
substrate leads to a large number of solutions for interconnects and circuitry on surfaces as diverse as battleship hulls,mobile
phone casings and clothing. In the example of a mobile phone it is possible to connect chips to packages to PCBs to displays
to batteries to antennae on the casing of the object itself using a single polymer material. Many of the subsystems such as the
PCB and the antennae can also be made from a conducting polymer deposited and patterned on the casing. The natural
extension of this is to use flexible substrates and turn the casing into a 2D sheet and thus manufacture a mobile phone that
can be rolled up. By way of example the manufacturing process for a polymer antennae within a mobile phone case is
demonstrated using silver-based ink.

Manufacturers of electronic devices,from home audio equipment to automotive keyless entry systems,are increasingly
seeking a reliable,cost effective method for uniquely identifying and tracking products through the manufacturing cycle,
sales distribution and after-sale warranty verification. An autonomous,automated tracking system requires that a permanent,
machine-readable code be applied to an internal printed circuit board to uniquely identify each product. The code must be
durable enough to survive manufacturing processes including wave solder and board cleaning,must not affect circuit
performance,and must store information in the small space available on real-estate conscious printed circuit boards.
The 2D matrix code provides a means to store alphanumeric character strings in very small areas of the printed circuit board.
Laser marking technology provides a method for permanently applying 2D matrix codes to most commonly used board
substrates and conformal coatings. The high-resolution and high-accuracy of beam-steered laser marking systems provides
the means to create well-defined codes for high-reliability reading regardless of code size. Laser marking also provides a
fully computer-controlled marking process for easy implementation into an automated product tracking system.
The operating principles of beam-steered laser marking systems utilizing both CO2 (carbon-dioxide) and Nd:YAG
(neodymium:yttrium aluminum garnet) lasers will be discussed in terms of compatibility with substrate materials,marking
performance,cost of acquisition and operation,maintenance,and integration with computerized product tracking systems.
Subjects will include the data capacity of 2D matrix codes (Figure 1) and their corresponding sizes with the marking
capability of laser systems. Installation in SMEMA-compliant manufacturing lines while maintaining a laser safe
environment will be discussed. Samples of overall productivity will be presented for several board marking scenarios
including single board and multi-up board configurations.

Microvoids are tiny voids in solder joints and differ from the more well known solder joint voiding in their individual size
and location. The microvoids discussed herein are described as an abundance of small voids at or near the interface of a
PCBA solder joint. In the most severe cases of voiding,a solder joint my fail physically and electrically. Each void reduces
the cross-sectional area of the solder joint; at some point the remaining solder is insufficient to meet functional demands.
While information related to these tiny interfacial voids has existed in industry literature for several years,the use of recently
available X-ray analytical equipment has raised the level of microvoid observation (See Figure 1). It is not known if
microvoiding is responsible for previously failed assemblies to which no root cause failure mode had been assigned. Unlike
“Black Pad” interfacial fractures related to Electroless Nickel Immersion Gold,microvoiding has not been directly related to
a galvanic effect of PCB circuit design. This provides hope that the phenomenon may be more easily prevented,even on the
most difficult designs.

In this study,the DIG process (Direct Immersion Gold),is investigated. DIG is a process in which gold is plated directly on
copper as a surface finish for printed circuit board and package applications. By examining the deposition reaction of the
electroless flash gold plating bath,it was confirmed that,copper does not co-deposit with gold and also that the main driving
force for deposition is an autocatalytic reaction. In addition the effects of the copper surface roughness and deposition time
on the deposit and solderability characteristics were examined. It was determined that copper surface roughness affects solder
spread-ability,and that solder joint characteristics were excellent when the film thickness is within the range of 30 to 80 nm.
Furthermore,good wire bonding characteristics were confirmed from deposits plated by a neutral pH,autocatalytic type
heavy electroless gold plating bath,atop the flash gold.

In order to get excellent signal Integrity,half PTH holes will be a new trend in high frequency backpanel designing.
Backdrilling is necessary for this application. This paper explores the application range,technology tickler,technology
method and reliability testing of backdrilling for backpanels.

PTFE-FR4 hybrid laminated multi-layer PCB technology is being applied more and more widely. This technology requires blind via fabrication in a PTFE core. This paper gives a picture of the manufacturing process for multi-layer PCBs with PTFE
focusing on material specifications of anti-overflow and surface treatment techniques,thereby addresses the feasibility of this
technology.

In the past the use of filling pastes in PCB production was largely limited to via hole fillers. These materials with a solids
content of 100% are still successfully employed today to close via holes and thus ensure their proper sealing for vacuum
adaptation during incircuit testing. Furthermore,they are used to avoid the deposition of flux residues that may create critical
microclimates in the holes and/or under components. However,there is only limited use for these products in newer fields of
pcb manufacturing.
The latest filling materials (also referred to as plugging pastes) are largely used in Sequential Build-Up technology. Due to
their specific properties,these materials enable the manufacturing of buried and blind via holes.
Thick film fillers are of growing importance in case of extremely high copper build-up (also termed 400 µm technology) in
order to allow a leveling of the traces before a solder mask can be applied.
All of the discussed materials belong to the electrically non-conductive type.

Factory simulation has been used extensively to optimize and reduce costs across many manufacturing disciplines.
Unfortunately,general purpose factory simulators do not effectively model the special needs of electronic assembly. For
example,the wide variations in rework time on different boards can create a significant bottleneck for the boards with low
first pass yield. This bottleneck delays product shipment,and results in higher costs and lower customer satisfaction. Since
time differences due to variations in first pass yield are not effectively modeled by general discrete event based
manufacturing simulators,this problem will not be caught if that is the only simulator used.
This paper presents a comprehensive approach to manufacturing simulation that includes detailed analysis of the boards to be
built coupled with a general manufacturing simulator to accurately predict the time,cost,and throughput for board assembly.