After the implementation of the ban on chlorofluorocarbons (CFC) in 1987, no-clean fluxes emerged in the marketplace.  Most commercial manufacturers converted their assembly processes to no-clean, but the high reliability industry (military, aerospace, medical, etc.) continued to remove the flux residues from their assemblies. 

In the early days of batch defluxing equipment, the technology more closely resembled household dishwashers than industrial defluxing machines.  After the CFC ban and subsequent decline of commercial defluxing, manufacturers of inline defluxing equipment focused on the high reliability market.  

Inline defluxing systems, while capable of removing flux residues, were large, loud, expensive, and consumed high quantities of electricity, water, and chemicals.  These were not significant issues with commercial assemblers given the high volumes of commercial products produced.  There are several reasons why batch technology has caught up to other cleaning technology for high reliability devices, including cleanliness, dryness, Statistical Process Control (SPC), environmental footprint, and throughput. 

Cleanliness: Batch format defluxing systems do not rely on a fixed conveyor speed setting to determine the amount of wash, rinse, or dry time an assembly requires.  Each process is independently controlled.  For example, long washes may be combined with short dry times allowing unique cleaning profiles to be developed for a particular batch of assemblies.  Batch machines are also uniquely capable of providing real-time cleanliness testing.  Aqueous Technologies calls this technology “Predictive Cleanliness”.  Because each process cycle is not interdependent on another, Aqueous Technologies developed a technology that allows the rinse water to be collected and subjected to ionic testing in real time. The real time cleanliness analysis allows the machine to expand or contract the cycle time in order to meet the user’s cleanliness requirement.  Predictive cleanliness is highly desirable for high reliability assemblies, which tend to be more costly than commercial products.  By knowing how clean the boards will be before the end of the defluxing process, post clean cleanliness testing becomes more predictable while producing drastically lower failure rates.

Dryness:  Drying is often the most overlooked segment of a defluxing process.  Because the drying time is independently controlled, assemblies may be subjected to the actual time required to eliminate all moisture, both from the assembly’s surface, below components, and in between layers.  Most batch format machines provide a rapid bake-out process, combining convection and radiant heat technology rather than a mechanical removal of moisture.  For example, a batch process allows a user to single out the drying process requirements from the rest of the defluxing parameters, ensuring that the specific drying temperature and time are achieved for thorough drying.

Statistical Process Control (SPC):  SPC is a required element of any high reliability assembly process.  Common SPC mandates can be found in all quality standards. Because each process element is independently controlled, each process step and result can be individually recorded for statistical analysis.  This becomes more evident as more and more companies are subjected to strict process audits.

Environmental Footprint:  This is an area where batch processes provide an advantage.  Batch defluxing systems require about thirty gallons (114 liters) of water every hour.  Inline processes, for example, may require as much as three hundred gallons (1135 liters) of water per hour. With batch defluxing technology requiring only one tenth of the water and disposal requirement of inline, as well as a fraction of the electrical current, it is logical that batch technology is less environmentally intrusive than most inline processes.

Throughput: The new high-yield batch technology preserves all of the advantages associated with batch processes, while providing throughput rates equal to or better than an inline alternative.  The “digitalization” of medical, military, flight and other high reliability products have created a higher demand for higher volume defluxing systems.  Increasing expectations of reliability and rising concerns over liability has significantly increased the use of defluxing technology equipped with the highest degrees of process control including real-time cleanliness testing.

For more information related to this article, or to schedule a demonstration of the Trident series batch defluxer from Aqueous Technologies located at the EMPF, contact Ken Friedman, 610-362-1200 x 279 or via email at kfriedman@aciusa.org.