insure the same quality a customer has been accustomed to with a Sn63Pb37 process is achieved. The reflow,wave soldering
and hand assembly processes must all be optimized carefully to insure good joint formation as per the appropriate class of
electronics with new solder alloys and often new fluxes.
The selection of soldering materials and fluxes are important as to insure high quality solder joints with lead-free solders
which tend to wet slower than leaded solders but also the process equipment must be lead-free process compatible.
Components must be lead-free and able to meet the thermal requirements of the process but also the MSL (moisture
sensitivity limits) must be observed. Board finish must be lead-free and the PCB must be able to sustain higher process
temperature cycles with no physical damage but also good solderability to enable subsequent soldering at the wave or hand
assembly.
Tin-silver-copper has received much publicity in recent years as the lead-free solder of choice. The IPC Solder Value Product
Council as the preferred option endorsed Sn96.5Ag3.0Cu0.5 (SAC305) for SMT assembly and most assemblers have
transitioned to this alloy for their solder paste requirements. The SAC305 alloy due to its 3.0% content of silver is expensive
when compared to traditional leaded process for this reason many contract manufacturers and PCBA assemblers are opting
for less costly options such as tin-copper based solders for wave,selective,hand-soldering,dip tinning operations.
In recent years tin-copper based solders with a variety of elemental additives have emerged which improve the overall
properties and performance of tin-copper solders. Tin-copper solder without the incremental additions of certain elements is
rarely used but the addition of nickel or nickel and bismuth as found for example in K100 and K100LD respectively do offer
improvements in wetting,joint cosmetics and in some cases solder joint reliability.
In this conversion SAC305 was used for the reflow process,tin-copper-nickel based solder K100 was used in the wave
soldering operation and it was also used in solder wire form for hand assembly. This paper is a summary of the experience at
a medium sized assembler in achieving the customer driven mandate to go lead-free and the maintenance of production yields
and quality using both tin-silver-copper and tin-copper in the assembly of high end printer boards. Over 120,000 builds were
achieved with a 99.6% first pass yield for the overall soldering process.

Solving "Fine Pitch" Metric Pitch BGA routing is becoming increasingly challenging for PCB design layout. There are solutions but they are very hard to find. This presentation will cover common solutions for routing Metric Pitch and Fine Pitch BGA components.

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As the entire electronic manufacturing industry braced for the July 1,2006 deadline,it has been reevaluating the entire production process. Likewise,the precision cleaning industry must also prepare for the impending deadline as lead-free solder paste formulations will increase cleaning demands. When implementing lead-free solder pastes,users’ assemblies have to be reflowed at higher temperatures,thus intensively baking-in flux residues. To improve the flow of solder at higher reflow temperatures,lead-free pastes contain increased activator content in return impacting the potential risk of corrosion. Furthermore,lead-free pastes also have increased rosin content to achieve low void rates increasing the amount of residues to be removed. Finally,several studies by the authors have determined that silver,a commonly used alloy in lead-free solder pastes,has a tendency to form dendrites. To prepare for the new cleaning demands,the precision cleaning industry must ask itself what changes to existing processes are necessary to meet the new cleaning demands. In fact,more than 15 years ago,non-ozone depleting legislation forced radical changes—changes that mirror the one presented by WEEE / RoHS now. A large number of users have previously used DI water-based cleaning processes,in which water-soluble eutectic products were cleaned. With the onset of lead-free alloys,the authors have experienced an increased demand for cleaning water-soluble lead-free products,as some residues have become water insoluble (due to lead-free soldering process specification). As a result,modifications to the current DI-water processes are necessary,and will involve chemically assisted cleaning. These new users as well as current users are now confronted with more questions,especially whether additional hardware is necessary,or whether processes need to be separated. Current legislation restricts the level of lead in lead-free assemblies to exceed 0.1% by weight. This limitation was adopted in December 2004,and also included other heavy metals such as Cadmium (0.01%),Mercury (0.1%),hexa-valent chromium (0.1%). Such stringent limitation requires tight process controls,including verification of RoHS and WEEE conformance for the cleaning process. This DOE study was therefore initiated,and begins to shine light on the potential risks associated with cleaning lead-free and eutectic assemblies in a single process also known as mixed cleaning process. An initial customer bath sample analysis was conducted to determine the levels of lead and other heavy metals commonly found in eutectic processes using MPC®-based products. It was found that lead and tin were present in various amounts. Tin and lead is a commonly known redox-pair with sufficient redox potential to facilitate the reduction of lead on lead-free assemblies. The authors decided to study this phenomenon in more detail and include the ionic contamination pathway as well. As a result this study was able to address the two most probable pathways to the incorporation of lead into lead-free assemblies

There is a growing problem in the industry with no-clean flux technology and the after effects it can have on reliability. If the
fluxes are not fully complexed (not fully heat activated) there can be a number of failure mechanisms attributed directly to
the flux. There is a tendency for the flux to become entrapped under low standoff parts and parts with very tight spacing if
you have dirty incoming bare boards or components. The problem then becomes how to clean and recover the product to
acceptable functioning hardware after time has passed. The flux becomes harder and harder to remove but the partially heat
activated flux residue does not become less moisture absorbing over time.
In this presentation we will show the effectiveness and timing issues on cleaning hardware that has been assembled with a
no-clean flux that has a corrosive contamination problem. Potential issues include: high chloride residues from bare boards
(HASL),partially activated flux residues,and localized cleaning that has created a trapped surface residue causing corrosive
or leakage problems. This recovery plan outlines the material and hardware assessment for water intolerant or material
compatibility issues. Mission critical hardware contaminated by process and assembly chemicals can be cleaned effectively
when using a combination of cleaning energies,such as,low pressure,high volume,saponified chemical wash followed by a
steam cleaning and DI water rinsing. We will show that a no-clean flux can be cleaned and the product brought back to levels
of acceptable functioning hardware.

The complexity of the electronic assembly manufacturing environment increases with the miniaturization,low standoff components,and solder alloy advancements. Past history suggests that the cleaning fluid must be closely matched to the cleaning machine. The problem is that low standoff components and many new flux compositions for Pb-free are more difficult to clean. To achieve clean circuit assemblies,existing cleaning processes must operate using a narrow process window that stresses current production requirements. Extensive research and development of new engineered cleaning fluid and mechanical impingement innovations open the cleaning process window. The purpose of this designed experiment is to show video evidence of cleaning performance improvements when optimizing the cleaning and mechanical impingement variables. Using the optimal process conditions,the SMTA Saber board will be run through the cleaning process,using four different Pb-free solder pastes from leading vendors. The boards will be sent out for ion chromatography and SIR testing per IPC guidelines. The findings will be reported.

Low-pressure plasmas have been used for many years to surface clean and functionalize substrates prior to downstream
converting operations; therefore,the benefits of plasma treatment are well recognized: reduced degradation of surface
morphology,higher treatment (dyne) levels,elimination of backside treatment,and extended life of treatment over time.
However,the complexity,slow speed and high cost of these contained vacuum plasma systems made them impractical for all
but the most esoteric applications. Now a system has been developed that allows plasmas to be sustained at atmospheric
pressure in a way that permits the surface cleaning of PCB substrates on a continuous web handling system similar to a
corona treating system. The atmospheric plasma process allows treatment using a broad range of reactive gases and has been
successfully tested on various metals,films,papers,foams,and powders. Further,depending upon the cleaning requirement
and type of material,roll-to-roll processing speeds in excess of current PCB vacuum processing speeds can be achieved. The
particular solution of significant importance to the circuit board fabrication industry described in this paper and provided by
atmospheric plasma systems is removing the residues of contaminants from sensitive surfaces without damaging them to
increase yields. The application of atmospheric plasma technology to PCB manufacturing and its critical parameters will be
presented because of its potential increase in processing speed in sheet and roll-to-roll orientations.