Papers about flux residue
by Mike Bixenman D.B.A., Steve Stach, Dr. Ning-Cheng Lee
Ionic Cleanliness testing machines are designed to determine the total ionic content extractable from the printed wiring board for purposes of process control. The conductivity of the extract solution is measured and the results are expressed as sodium chloride equivalence per unit area. The problem with this method is two fold: 1.) Many of today’s low residue flux and lead-free flux residues are not soluble in the extract solution. 2.) Contamination of concern is with site specific components, from which contamination does not correlate to the area of concern. The purpose of this study is to research low residue and lead-free flux structures, identify solvent compositions that will dissolve these residue types, and offer options for performing both bulk and site specific ionic cleanliness testing methods.
lead-free, Cleaning, flux residue, flux, soldering, solder, solder paste, SMT
[Permanent Link to this Paper ]
Posted on 1 Jan 2009
by Dr. Ning-Cheng Lee
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Lead-Free Flux Technology and Influence on Cleaning
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Lead-free flux technology for electronic industry is mainly driven by high soldering temperature, high alloy surface tension, miniaturization, air soldering due to low cost consideration, and environmental concern. Accordingly, the flux features desired included high thermal stability, high resistance against burn-off, high oxidation resistance, high oxygen barrier capability, low surface tension, high fluxing capacity, slow wetting, low moisture pickup, high hot viscosity, and halogen-free. For each of the feature listed above, corresponding desired chemical structures can be deduced, and the impact of those structure on flux residue cleanability can be speculated. Overall, lead-free flux technology results in a greater difficulty in cleaning. Cleaner with a better matching solvency for the residue as well as a higher cleaning temperature or agitation are needed. Alkaline and polar cleaner are often needed to deal with the larger quantity of fluxing products. Reactive cleaner is also desired to address the side reaction products such as crosslinked residue.
lead-free, flux, flux residue, solder, soldering, cleaner, Cleaning, SMT
[Permanent Link to this Paper ]
Posted on 1 Jan 2009
by Eric Bastow
No-clean soldering processes dominate the commercial electronics manufacturing world. With the explosion of growth in handheld electronics devices, manufacturers have been forced to look for ways to reinforce their assemblies against the inevitable bumps and drops that their products experience in the field. One method of reinforcement has been the utilization of underfills to “glue” certain surface mount devices (SMDs) to the PCB. This provides additional mechanical strength over and above the soldered connections. Bumped SMDs attached to the PCB with a no-clean soldering process offer the unavoidable scenario of the underfill coming in contact with a flux residue. This may or may not create a reliability issue. No-clean solder paste flux chemistries can vary. Some have halogens and others do not. Some have standard residues and others have residues optimized for pin probing. There are also a number of underfill chemistries on the market. Furthermore, underfill curing conditions vary depending on whether the SMDs are exposed on the surface of the PCB or underneath an RF shield. This paper will discuss an experiment designed to measure the electrical reliability of various combinations of underfill and no-clean flux residues, as measured with J-STD-004B SIR (IPC-TM-650 2.6.3.7).
Apex 2012, solder paste, no-clean flux, flux residue
[Permanent Link to this Paper ]
Posted on 1 Mar 2012
by Dr. Ning-Cheng Lee , Paul A. Jaeger, Manchao Xiao
The probe-testability of no-clean solder paste flux residue at in-circuit-test is determined mainly by the residue amount, residue location, and residue hardness. The testability increases with decreasing amount of residue, decreasing amount of top-side flux spread, and increasing amount of bottom-side flux spread. The residue amount, top-side flux spread, and bottom-side flux spread affect primarily pad probing, pad probing, and pin-tip probing, respectively. Inert reflow atmosphere helps probe penetration. Higher metal load effectively reduces the flux spreading. Among all, the soft residue approach appears to be most promising in providing successful probe contact.
lead-free, pb-free, no-clean, flux residue, solder paste, testability, probe
[Permanent Link to this Paper ]
Posted on 1 Jan 2009
by Eric Bastow
With the predominance of no-clean soldering processes and ever decreasing component standoff, the industry has had to consider the reliability of, what may be, partially activated or "gooey" flux residues under component bodies. Similarly, questions have also risen about the reliability of flux residues resulting from the reflow of no-clean solder pastes that are "entrapped" under RF shields or "cans", where escape of the volatile ingredients of the flux is greatly hindered. In this paper, discussion will be made regarding an experiment designed to mimic the aforementioned conditions and how these conditions affected the SIR performance of the no-clean flux residues. A variety of no-clean solder paste flux residues will be discussed, including a halogen-containing, Pb-free solder paste flux; a halogen-free, Pb-free solder paste flux; a halogen-free, Pb-free solder paste flux with a residue optimized for pin probing; and a halogen-free SnPb solder paste flux.
Apex 2011, solder paste, pb-free, halogen-free, no-clean flux, flux residue
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Posted on 11 Apr 2011
