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Solder Pallet Maintenance?

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#50887

Solder Pallet Maintenance? | 28 June, 2007

Just wondering how many companies who have implemented a solder pallet maintenance program to remove flux, etc.

What is the life span of pallets? How often do you clean? What do you clean with?

Thanks rm

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#50888

Solder Pallet Maintenance? | 28 June, 2007

Permali is the manufacturer of Durostone pallet materials and they recommend the following methods:

http://www.permali.com/pallets/PDF/Tech21.pdf

http://www.permali.com/pallets/papers.htm

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#50984

Solder Pallet Maintenance? | 11 July, 2007

We have received several e-mails and phone calls regarding the Permali recommendation of cleaning Durostone pallets so I thought I would address these questions on the forum for everyone's benefit.

Q: Can 440-R SMT Detergent be used for manual cleaning of pallets? A: Yes, while ultrasonics is the preferred and most efficient mechanical scrubbing action, manual cleaning and spray-under-immersion using 440-R SMT Detergent is also safe and effective.

Q: What are the differences between ultrasonic �Frequency� and �Power Density�? A: The lower the ultrasonic frequency, the more powerful the scrubbing action. Common ultrasonic cleaning frequencies range from 20 kHz up to around 68 kHz (frequencies above 68 kHz are available, but rare and very costly). Using the analogy of manual cleaning with a scrub brush, the ultrasonic �frequency� is similar to the type of brush used. Using a 20 kHz frequency would be like using a �wire� brush. Using a 68 kHz frequency would be like using a tooth brush. Most stencil cleaners use a frequency of 40 kHz and modulate or �sweep� the frequency +/- two kHz to eliminate standing waves or �hot spots� in the cleaning bath.

Ultrasonic �Power Density� is the amount of electrical energy introduced into the cleaning bath via the ultrasonic generator and measured as watts / liter of wash solution. Most all ultrasonic stencil cleaners utilize 40 kHz frequency. However, the power densities used vary widely from one manufacturer to another. This is usually a reflection of the cleaning chemistries used. An inefficient cleaning chemistry will require harder scrubbing i.e., a higher Power Density. Permali recommends a power density of less than 15 watts / liter for cleaning pallets. The IPC and EMPF lab recommend power densities of around 10 watts per liter for cleaning populated misprinted PCBs. (http://www.smartsonic.com/news.html page down to fourth article.) The Power Density is similar to the amount of energy exerted on the scrub brush. High Power Density (above 15 watts per liter) is like scrubbing hard with both hands on the brush. Lower Power Density (less than 15 watts per liter) is like using two fingers on the scrub brush.

The highest frequency and lowest power density required to achieve the desired cleaning results is ideal - for cleaning pallets that would be 40 kHz at 10 - 15 watts / liter power density.

Q: Can the same stencil cleaner be used for cleaning pallets, stencils and misprinted PCBs? A: Yes. However, the post-solder flux residue from pallets is a different contaminant than cleaning solder paste from stencils and misprints. Pallet-cleaning will require water temperatures too warm for the safe cleaning of stencils (stencils are heat-sensitive). Most Smart Sonic users that clean both pallets and stencils will clean stencils and misprints at ambient temperature and then batch clean pallets weekly at elevated temperatures. Be certain to note the Power Density as 15 watts / liter may be safe for cleaning pallets, but may be too harsh for cleaning misprinted PCBs

Regards, Bill Schreiber Smart Sonic Corporation bill@SmartSonic.com

Tel: 1-818-610-7900 http://www.SmartSonic.com

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