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.

The recent need to develop lead-free electrical and electronic products has resulted in an increased demand to characterize
solder joint integrity. Many standards exist to evaluate the long term reliability of electronic components or the quality of an
assembly process. However no standards apply to custom printed circuit board assemblies. For example,the IPC-9701
standard and the use of evaluation boards are intended at evaluating processes as opposed to products. We have devised a
methodology,combining inspection,the application of thermal and mechanical fatigue to stress the solder joints and the
devices,and cross-section analysis to evaluate the quality of the solder joints,plated through-holes,and board manufacturing.
This test,which we have named MAJIC (MuAnalysis Joint Integrity Characterization),has been applied to printed circuit
boards of various finishes that have been assembled using leaded or unleaded solder pastes and using both leaded and
unleaded components in various combinations.
The MAJIC methodology provides a vehicle to qualify an assembly process or to evaluate a supplier. With the addition of
predetermined quantitative criteria,it could become a standard for the qualification of custom printed circuit board
assemblies. This paper will demonstrate the wealth of information and reliability risks that have been exposed using this
methodology on several products.

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As the electronics industry prepares to meet the requirements of the European Community’s RoHS directive on lead in electrical and electronic equipment an issue about which concern is frequently expressed is the apparently inferior wetting performance of lead-free solders. The general observation is that lead-free solders are slower to wet and then do not spread far beyond the area of direct contact. There is also much discussion of the relative merits of various lead-free solders in terms of their wetting time,which is usually reported as the time from first contact of the sample with molten solder to the time at which the net force on the sample is zero. However,the performance of some lead-free solders in this wetting balance test has been found not to correlate with their practical performance in soldering processes; an alloy with what appears to be
inferior performance in the wetting balance test performs better in actual production soldering than an alloy that had a better result in the wetting balance test. In the work reported in this paper the data that emerges from a wetting balance test was studied in detail. It was found that the result of the wetting balance test could be correlated with the performance of the alloy in production soldering only if the force vs time plot is analysed in terms of five distinct stages with the performance of the alloy as a solder correlating best with time taken for the force to increase from its maximum negative value to zero and then
to the maximum wetting force.

Lead-free wave soldering requires tighter process control than soldering with lead based alloys. A key area of the machine that impacts the ability to solder lead-free alloys without defects is the flux system. A large variety of fluxers are available for use with lead-free soldering - each having advantages and disadvantages. This paper compares the more popular flux systems in terms of through hole penetration,coverage accuracy,cost level,maintainability,and chemical compatibility. Ultrasonic,air atomization,and jet type flux systems are discussed and test data presented for each system.

The process challenges of lead-free wave soldering often require the use of new flux chemistries when compared with the relatively tolerant tin-lead wave soldering process. In some cases,the fluxes used in tin-lead soldering work well in lead-free assembly. In other cases,however,the complexity of the assemblies dictate more active,heat-sustainable products formulated specifically for lead-free applications.
This paper reviews the J-STD-004 and how it is used in flux categorization and selection. It also discusses the major types of flux formulations available,and the design,process and reliability implications of using each type. The purpose of the paper is to help the reader make an informed choice when selecting wave solder fluxes for lead-free processing.