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What's The Waste?

#5275

What's The Waste? | 19 February, 2001

Please take us through the options for processing the "waste" liquid that is loaded with solder, adhesives, and what not as a result of cleaning stencils and mis-printed boards. What are the costs for equipment, material disposal, and other items of these various approaches?

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#5284

What's The Waste? | 20 February, 2001

Hello Dave,

Before I get into waste management, I must first stress the importance of checking with your local regulating agencies. Every area can be and usually is different. California regulations differ from Ohio and Ohio�s are different than Munich, etc. There is no one answer to resolve every scenario.

Your question deserves considerable attention. In fact, there was a previous OnBoard Forum last June by Lee H. Goldberg who presented an entire book on the subject, Green Electronics/Green Bottom Line. Although his book doesn�t touch specifically on Stencil Cleaner waste management, I feel the subject is diverse enough to require a book to explain the variables. I�ll try not to write a book here and eliminate half of the information by simply saying that solvents are bad! Solvent waste streams are always problematic and raise a red flag in the eyes of the EPA, AQMD and OSHA.

Now, with that out of the way, I can only share my experiences of what I have seen done with the waste stream and what I feel is the best ways to manage the waste.

I like the way you are thinking. So many users evaluate the cleaning machine first. Then, after installation, the question of waste streams comes as a complete surprise (usually a shock). Believe it or not, I have seen users buy and install a cleaning machine and then begin to evaluate chemistries only to find the chemistry that best fit their needs didn�t work well in the machine they purchased. I advise a person to look at the chemistry first. The chemistry is the most important element of any cleaning process and the main factor in creating the waste stream and usually dictates how to treat it. The cleaning machine only determines the Initial capital cost, the footprint, the ability to deliver the chemistry into fine-pitch areas, user interface, potential to damage the stencil (high pressure sprays can bend delicate land mass area, heat, etc), and ease of maintenance. The chemistry will determine the reaction with the contaminant, cleaning ability, environmental impact, user health and safety (risk of fire, explosion, cancer, fetal disorders, etc.), operational cost, presence of odors, cleaning cycle time, ability to clean different solder pastes (flexibility), requirements for heat (stencil damage, energy use, vapor generation), maintenance requirements, special storage and transportation requirements and waste management protocol.

I can only be specific about Smart Sonic�s aqueous waste stream because I know what�s in the Smart Sonic waste. The Smart Sonic 440-R SMT Detergent is a proprietary formulation just as other competitive chemistries are proprietary. Since I don�t know the ingredients of other chemistries, it would not be appropriate for me to suggest waste management protocols for the treatment of their waste. However, I can speak in generalities and make some suggestions and outline some precautionary measures by using the Smart Sonic waste stream as a standard. The Smart Sonic Stencil Cleaning Process has been certified by the EPA and AQMD and replicated over 700 times worldwide. By comparing other processes to the Smart Sonic process should provide some direction and tools for judgment.

The Smart Sonic waste stream, like other aqueous stencil cleaner waste streams is comprised of three components: the solder paste, the cleaning chemistry and water. Management of solid solder paste waste is already established because there is waste solder generated in other operations, i.e. empty solder paste jars and tubes, expired solder paste, dross, etc. The liquid waste is the difficult waste to manage because of the large volume, solid lead and ionized lead content (and potential �dual Hazard� rating if combined with solvents or hazardous ingredients found in some aqueous chemistries).

The Smart Sonic liquid waste can be filtered by conventional ion exchange or reverse osmosis filtration like other aqueous stencil cleaner wastewater. However, when filtering a liquid waste, there is always an effluent left for drain disposal. Most users do not want to discharge anything to drain because of the potential liabilities. EPA regulations state that if there is a lead contamination of the drain system within 50 miles of your facility and the origin of the contamination cannot be established, everyone processing lead waste and discharging to drain will share in the clean-up cost. So, even if your wastewater was lead-free, you could be held responsible for correcting your neighbor�s mess ($$$).

Smart Sonic�s 440-R SMT Detergent contains no hazardous ingredients, VOCs or solvents. So, instead of having to filter the waste by expensive filtration processes, the Smart Sonic wastewater qualifies for routine liquid evaporation. About once every two or three weeks, the liquid waste is transferred from the stencil cleaner into a standard evaporator. The non-hazardous liquid is evaporated to atmosphere, reducing everything to the original solid solder paste. The waste solder paste can be recycled in a dross process or dehydrated in an oven and melted into a wave solder pot. Some users just put it back into the empty paste jars since the empty jars are already considered hazardous waste.

The only waste from the process is small amounts of detergent residue (usually 8 � 9 lbs. every two to three months and much less when cleaning water washable solder paste). Detergent has a high BTU value and qualifies as industrial fuel and can be incinerated in many parts of the world. Otherwise, the amounts are so small, it can usually be added to an existing similar hazardous waste stream without incident.

Evaporation is a big advantage over filtration in that the evaporation equipment is often less expensive than ion exchange or a reverse osmosis filter systems and the user is removed from the liability selection pool because nothing is discharged to drain. Evaporators start at about $6000 vs. $10000 for appropriate filtration systems. The cost of operation is also low because the evaporator is normally on for only 10 - 15 hours per month.

Some users make the mistake of assuming that all aqueous waste qualifies for evaporation technology. However, many aqueous cleaning chemistries contain hazardous ingredients or VOCs that may not be evaporated to atmosphere. Even chemistries that are CAS Certified may contain up to 50 gm/L of VOCs. Again, check with your local regulating authorities before they check with you and illustrate what the cost of waste mismanagement can be.

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