Cleaning FAQs

Equipment

What equipment should I have for cleaning?

That depends on the cleaning chemistry you plan to use and the throughput of your shop. Basically, you can put cleaning equipment in three categories: hand cleaning; batch cleaning; and in-line cleaning. Of these three, in-line produces the best, most consistent cleaning. Batch cleaning is better than hand cleaning, but suffers from variability in cleaning. Batch cleaning can either be something like a batch degreaser, which uses a one-rack-at-a-time approach, or a batch cleaner, like an industrial dishwasher. Hand cleaning is most often the localized application of a cleaning solvent, such as isopropanol, with scrubbing (e.g. with a toothbrush). We don’t recommend hand cleaning because it spreads any flux residue, infecting larger portions of the board. This is especially true of no-clean fluxes. What kind of cleaning you do also depends upon your capital investment budget and the reliability level of your hardware.

What does “micrograms of NaCl equivalence per square inch” mean?

Most bulk ionic contamination (BIC) testers, such as an Omegameter or Ionograph, measure the total electrical conductivity (or inversely, resistivity) of the extract solution. The NaCl equivalence refers to the amount or concentration of sodium chloride (salt) needed to produce a solution of the same conductivity. It has nothing to do with the amount of elemental sodium or chloride found in the test solution. NaCl equivalence is a factor used to compare the results from one ionic tester to another.

Chemistry Selection

What cleaning media should I use?

That depends on the soils you need to remove and the hardware susceptibilities involved. Our preferred cleaning method for any flux is saponified cleaning in deionized water. The saponifier used, and the amount used, depends on the cleaning challenges present. A 3-5 % solution of Enviro Gold 816/18.54A (EnviroSense Tel# 408-213-2291) is good for most materials. A 7-10 % solution may be needed for heavier flux loads. In our opinion, aqueous cleaning is superior to semi-aqueous cleaning and gives all the benefits without the drawbacks of semi-aqueous cleaning. Solvent cleaning often does not have the mechanical action of the aqueous cleaning sprays and; therefore, is not as efficient. Solvent cleaning should only be used, in our opinion, where the hardware is completely intolerant of water.

Evaluation

How should I evaluate which cleaner is best for me?

Basically, ion chromatography is the best method. You want to characterize the residues present and determine how much residue is left after the candidate cleaning process. In such an evaluation, you should include uncleaned samples to show the residue level before any cleaning, so you have an idea of the efficiency of the cleaning process. We also recommend that you include a known good, or baseline, process for comparison.