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Isopropyl Alcohol Alcoho l T ypes • Ethanol – Fermented / yeas t – consumab le • “ the r oot cau se and soluti on to all of life' s p r obl ems ” – Homer Simps on • Methanol – Fe rment ed / wood – toxic • Ethanol + …

Solvents

• Usage on solvents split down the middle with yes or no

• A NO to solvent is often based on a negative experience that can be traced to:

• Negative effect on the print process following solvent application

• Poor solvent performance

• Application method used

• Mismatch of solvent to printing material

• Misunderstanding of what solvents do

• Most common solvent used is Isopropyl Alcohol – which now has its issues

• Chemistry companies, prior to 7 years ago, did not understand the printing process and its requirements

• Often what was being recommended to be applied to the printer is also used to clean boards or stencils in a

tank

• Requirements of the print process and new chemistries have improved performance in the printer and have a

targeted this application

Understanding the Cleaning Process for Automatic Stencil Printers

Isopropyl Alcohol

Alcohol Types

• Ethanol – Fermented / yeast – consumable

• “

the root cause and solution to all of life's problems

” – Homer Simpson

• Methanol – Fermented / wood – toxic

• Ethanol + Methanol = denatured alcohol

• Propanol – Fermented / bacterium (Clostridium Acetobutylicum) - feeds on cellulose – common name – Rubbing Alcohol

• Isopropyl - mixture of Propanol and ethyl methyl ether - secondary alcohol that uses a binder

Issues with Isopropyl

• Flash Point = 53 F (open cup) 55 F l (closed cup)

• Defined as a Class 1B flammable liquid ( same as Gasoline)

• Definition of a flammable liquid – flash point below 100 F

• National Fire association

• US Environmental Protection Agency (EPA)

• US Occupational Safety and Health Administration (OSHA)

• Previously Isopropyl was a match as it was the solvent of choice used in paste

• Newer paste designs use a solvent to increase stencil life – can react badly to Isopropyl

• Results in “clumping” of paste when combined with flux

• Less than 90% purity will leave residue on stencil that will result in poor transfer efficiency

Understanding the Cleaning Process for Automatic Stencil Printers

Solvent Checklist

• Chemical compatibility with the solder paste

• Dissolve the flux & free up the powder spheres

• No bad reaction with paste that affects paste viscosity

• Process compatibility

• Dry evenly and at a controlled rate

• No adverse paste reactions

• Leave no residue

• Equipment compatibility

• Does not attack valves, seals, pumps, reservoirs

• Safety & health

• Non-toxic, non-flammable, low- (or no-) odor

Understanding the Cleaning Process for Automatic Stencil Printers