|Ask the Experts|
May 28, 2012
Flux Aging Study
What parameters would you look at when doing astudy on aging of liquid flux?
|Expert Panel Responses|
For most cases, themost measurable difference over time is acid number. This is particularlyrelevant for low-solids, no-clean fluxes. Most fluxes have a shelf lifeof 1 to 3 years, and the main driver of the shelf life measurement is the factthat the acid number of the flux declines over time. That decline in acidnumber can result in poorer soldering performance during wave soldering. As long as thecontainer is sealed, specific gravity should stay fairly constant over time. Some fluxes can alsodemonstrate a change in color over time; these changes are generally notimpactful to performance, so the user should not be alarmed by this if it occurs.Acid number is really the best measurement to measure the consistency ofthe flux over time.
General Manager - Electronic Assembly Americas
The typical parameters are acid number, density, solids percentand solderability testing using a wetting balance to determine the Force versus Time curvein original and aged flux. These are normally done to determine shelf life of fluxes at themanufacturing level. Other tests are colorchange and turbidity, these may be impacted by age and exposure to light.
Senior Market Development Engineer
Refer to J-STD-004. This is the industrystandard for requirements for soldering fluxes, and has a lot of information oncertification, shelf life info, and re-certification methods for fluxes. Thestandard also lists all of the appropriate test methods within IPC-TM-650,which is a free download from the IPC's web site at http://ipc.org/ContentPage.aspx?pageid=Test-Methods.
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