Technical Library | 2020-03-09 10:50:17.0
A customer called the Helpline seeking advice for cleaning no-clean fluxes prior to applying a conformal coating. The customer's assemblies were manufactured with a no-clean rosin based solder paste (ROL0) and were cleaned with an isopropyl alcohol (IPA) wash. After cleaning, a white residue was sometimes found in areas with high paste concentrations and was interfering with the adhesion of the conformal coating (Figure 1). For conformal coatings to adhere properly, the printed circuit board (PCB) surface must be clean of fluxes and other residues. In addition, ionic contamination left by flux residues can lead to corrosion and dendrite growth, two common causes of electronic opens and shorts. Other residues can lead to unwanted impedance and physical interference with moving parts.
Technical Library | 1999-05-07 10:47:00.0
White residue remaining after cleaning circuit board assemblies can be caused by a variety of chemicals and reactions. Rosin and water-soluble fluxes, circuit board resins and epoxies, component materials and other contamination all contribute to this complex chemistry. This paper discusses many of the sources of the residues that seem to be an ever-increasing occurrence.
Technical Library | 2022-12-19 18:59:51.0
Material and Process Characterization studies can be used to quantify the harmful effects that might arise from solder flux and other process residues left on external surfaces after soldering. Residues present on an electronic assembly can cause unwanted electrochemical reactions leading to intermittent performance and total failure. Components with terminations that extend underneath the package can trap flux residue. These bottom terminated components are flush with the bottom of the device and can have small solderable terminations located along the perimeter sides of the package. The clearance between power and ground render high electrical forces, which can propagate electrochemical interactions when exposed to atmospheric moisture (harsh environments). The purpose of this research is to predict and understand the functional performance of residues present under single row QFN component packages. The objective of the research study is to develop and collect a set of guidelines for understanding the relationship between ionic contamination and electrical performance of a BTC component when exposed to atmospheric moisture and the trade-offs between electrical, ionic contamination levels, and cleanliness. Utilizing the knowledge gained from undertaking the testing of QFN components and associated DOE, the team will establish a reference Test Suite and Test Spec for cleanliness.
Technical Library | 2023-04-17 17:05:47.0
In an ideal world, manufacturing devices would work all of the time, however, every company receives customer returns for a variety of reasons. If these returned parts contributed to a fail, most companies will perform failure analysis (FA) on the returned parts to determine the root cause of the failure. Failure can occur for a multitude of reasons, for example: wear out, fatigue, design issues, manufacturing flaw or defect. This information is then used to improve the overall quality of the product and prevent reoccurrence. If no defect is found, it is possible that in fact the product has no defect. On the other hand, the defect could be elusive and the FA techniques insufficient to detect said deficiency. No-clean flux residues can cause intermittent or elusive, hard to find defects. In an attempt to understand the effects of no-clean flux residues from the secondary soldering and cleaning processes, a matrix of varying process and cleaning operation was investigated. Of special interest, traveling flux residues and entrapped residues were examined, as well as localized and batch cleaning processes. Various techniques were employed to test the remaining residues in order to assess their propensity to cause a latent failure. These techniques include Surface Insulation Resistance1 (SIR) testing at 40⁰C/90% RH, 5 VDC bias along with C32 testing and Ion Exchange Chromatography (IC). These techniques facilitate the assessment of the capillary effect the tight spacing these component structures have when flux residues are present. It is expected that dendritic shorting and measurable current leakage will occur, indicating a failing SIR test. However, since the residue resides under the discrete components, there will be no visual evidence of dendritic growth or metal migration.
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COT specializes in high quality SMT nozzles and consumables for pick and place machines. We provide special engineering design service of custom nozzles for those unique and odd components.
2481 Hilton Drive
Gainesville, GA USA
Phone: (770) 538-0411
