Technical Articles

Through its team of researchers and process engineers, ZESTRON’s application experiments and findings are consistently published within our electronic manufacturing community through white papers, case studies and technical articles.

The following overview presents the latest technical articles and technical papers:

 - Cleaning processes / Cleaning agent technologies

• Keep Your Cleaning Processes Separated
  The shift toward high-reliability applications has put increasing demands on cleaning processes to ensure that the high-reliability remains after the product leaves the assembly facility. One of the main factors is that up until now, traditional production lines have largely relied on no-clean assemblies. However, field experience has shown that long-term reliability of no-cleans cannot be guaranteed
  Published in USTech, July 2011
  
  
• Go Greener in Your Cleaner
  Over the past 20 years, the common notion in the electronics manufacturing industry has been that alkalinity is a must to remove flux residues. Recently introduced pH-neutral defluxing agents are designed to do a superior cleaning job, but also protect extremely sensitive materials and meet stricter rinse water disposal regulations.
  Published in SMT Magazine
  
  
• Reliable Cleaning with Proper Coating: Cleaning Process Benefits for EADS
  Coatings and varnishes on electronic assemblies must adhere perfectly to ensure optimal functionality, even under extremely adverse conditions. Therefore, the highest requirements must be met with regard to the surface cleanliness of assemblies.
  Published in Mil/Aero online publication
  
  
• How Low Can You Go: Under Component Cleaning
  Nobody wants to see field failures due to electrochemical migration.  Preventing this class of failures used to be relatively easy – simply use a water soluble flux and clean the board after soldering.  Unfortunately, this solution no longer holds true, and can sometimes cause more problems than it prevents.
  Technical article published in Circuits Assembly
  
  
• Benchmark Study: pH-Neutral vs. Alkaline Cleaning Agents
  With the emergence of pH-neutral defluxing technologies in early 2009, pH-neutral formulations promised to set a new standard for material compatibility, while proving valuable to those who worked toward environmentally sound processes. As a result, potential users are very interested in assessing the differences between alkaline cleaning agents and the newer pH-neutral products, with regard to both, cleaning performance and material compatibility.
  One area of particular interest is the cleaning agent impact on sensitive metals. Material compatibility issues between sensitive metals and cleaning solution arise when corrosion, i.e. the electrochemical deterioration of a metal due to the reaction with its environment, takes place. To prevent corrosion caused by the very cleaning solution that is meant to safeguard the assembly from corroding in-field and potentially fail, inhibitors come into play.
  Technical paper presented at SMTAI 2010
  
  
• Limitations of DI-Water
  DI-water alone has a limited to no ability to solubilize non-ionic residues on the board surface. This technical study complements on the authors’ initial in-house findings , by comparing the latter to actual production conditioned assemblies. The lead engineering team at Northrop Grumman designed a very comprehensive blind study with numerous flux formulations to determine removability with DI-water against various chemistry supported systems. The findings revealed significant experimental data, which sheds much needed light on this emerging industry challenge. They include but are not limited to data related to:
  • respective chemical solvency
  • wettability
  • reactivity
  • fluid mechanical aspects
  Technical paper presented at APEX 2010 
  
  
• Contamination, Cleaning, Challenges and the Environment
  The removal of contamination encompasses the entire
  electronics manufacturing floor. Over a decade ago, the
  emergence of no-clean flux technologies seemingly
  spelled the end of “precision cleaning.” Ironically, exactly the
  opposite became true. The cleaning market has converted to
  cleaning at a pace not seen in prior years.
  Published in USTech Magazine
  
  
• Limitations of DI-water Processes:Why Switch From Pure DI-Water to Chemistry
  While most cleaning applications in the North American market rely on cleaning with DI-water only, for removing OA fluxes in first place, recent market studies show that water has reached its limitations in cleaning performance while favoring usage of aqueous processes.The term aqueous implies the use of aqueous-based chemistries with active ingredients and are usually diluted with DI-water. The nature of these active ingredients in the aqueous chemistries varies between manufacturer and his R&D knowledge.
  Technical paper presented at SMTAI 2009
  
  
• What's Wrong With IPA - Understanding Limits to Common Cleaners
  IPA-water is limited as a cleaner and should not be a standard for analyitcal extraction tests. A generally well understood unit for the "cleaning power" of a solvent is the Kauri-Butanol value (Kb-value, ASTM D1133). The result of this test is an index, usually reffered to as the "Kb-value". The higher the Kb-value, the more active the cleaning agent. Mild cleaners have low scores in the tens and fifties; powerful cleaners like the old chlorinated solvents have ratings in the low hundreds. Not surprisingly, the value for IPA is below 50.
  Published in Circuits Assembly Magazine, September 2009
  
  
• Astronautics - Successful DOE for a Military Application
  Conventional inline cleaning is giving way to specialized spray-in-air inline cleaners for certain applications that have stringent environmental and MIL reliability requirements. A typical example of this change has taken place at Astronautics Corporation, a manufacturer of military and commercial electronics in Milwaukee, Wisconsin. The company has successfully chosen FAST® Technology based ATRON® AC 205 in a spray-in-air inline cleaner. 
  Published in US-Tech Magazine, July 2009     
  
  
• Thermal Residue Finger Printing
  Experience indicates that softer residues are easier to clean than hard residues. What makes a residue hard is inherent in its make-up and history. The thermal history of a flux residue is important. The number of solder reflow cycles, the peak temperature, time after reflow and duration of the heating and cooling cycle will influence the hardness and thus, the cleanability of the residue.
  Technical paper presented at APEX 2009
  
  
• Fluid Flow Mechanics: Key to Low Standoff Cleaning
  This study was designed to investigate the impact of mechanical vs. chemical energy contributions during the removal of contamination under 1-2 mil standoff components. To validate the results obtained, extensive studies were conducted, specifically prepared test assemblies, iterative experimentation, as well as new mechanical innovations that might help users in the future. The authors included experimental data to address fluid flow mechanics, temperature and solvent concentration-related effects.
  Technical paper presented at APEX 2008
  
  
• Fluid Flow Mechanics: New Advances in Low Standoff Cleaning
  The increased complexity of components in the electronics industry results in a continuous decrease in standoff spacing between the components and the substrate’s surface. At the same time, the requirements for the product reliability and life expectation are continuously increasing, especially in the case of RF Technology. This in turn makes cleaning mandatory and the question arises as to which cleaning process can provide the required cleanliness levels under narrow capillary spaces.
  Technical Paper presented at SMTAI 2008
  
  
• Cleaning High-power Electronics
  To prevent malfunctions in high-power electronics, flux residues must be removed from flip chip components prior to subsequent processes. As a result, integrating a suitable cleaning application into the manufacturing process of flip chip components is often required. Solvent-based applications have re-emerged, and with that an overall process solution is necessary.
  Published in Advanced Packaging, May/June 2008
  
  
• Fluid Flow Mechanics: A New Definiton of Low Standoff Cleaning
  The emergence of smaller components is placing significantly more strain on all cleaning requirements. Chip components are currently placing the highest demand on removability as gaps are being reduced to less than 1 MIL. Therefore, cleaning underneath those gaps has gained a new definition.
  Technical Paper presented at SMTAI 2007
  
  
• Eutectic & Lead-free Defluxing in One Process
  Lead-free soldering has brought about several changes.
  The examination of the cleaning process for lead-free has raised a critical question: Can an exisiting chemistry-based cleaning process be used to clean both eutectic and lead-free alloys in the same equipment? A study was conducted to address this question, providing users with valid technical data to better assess associated risks when using one cleaning agent for both eutectic and lead-free products.
  Published in SMT Magazine, May 2007
  
  
• Stencil and PCB Cleaning in a Single Process
  As the demand for cleaning increases, some essential rules remain the same. For example, do not combine too many different cleaning processes into one machine using the same cleaning product.
  As the North American electronics market shifts to high-reliability manufacturing, the demand for cleaning processes is increasing. One reason is that traditional production-manufacturing lines relied on no-clean assemblies, which now are becoming less reliable. Flux residues are known to change the capacitance of through-connection contact areas, affecting the signal integrity of high-density integrated and high-frequency circuits. Furthermore, inert no-clean resin layers, when exposed to climatic conditions, form dendrites.
  Published in SMT Magazine, September 2007
  
  
• Improved printing by understanding wipe cleaning
  This case study was completed by Sanmina-SCI and illustrates how the quality of the printing process was improved by installing a new stencil underside cleaning process. The qualification for a new cleaning process was triggered by one of their key customers. The new requirements demanded a significant reduction of the number of solder balls per board. Additionally the cleaning agent had to demonstrate full compatibility with the MPM printer as well as the solder paste. As a result, IPA was replaced by a modern cleaning agent. The article presents the qualification method as well as the achieved benefits.
  Published in Global SMT & Packaging, July 2006
  
  
• Fast & Cost Effective Coating Tests
  Coating tests are required during development to avoid the expensive redesign of assemblies at a later point in time. Until now test methods have been time consuming and expensive. The authors investigated a fast cost effective test method, which puts conformal coating to the ultimate test.
  Published in OnBoard, November 2005
  
  
• No transition problems are to be expected
  By mid-2006, the RoHS (Reduction of Hazardous Substances) directive is expected to go into effect in Europe and will probably be adopted in other regions. Key in this legislative measure is the ban of large variety of heavy metals and other toxic materials in electronics products. As a result, the application of lead in solder paste will also no longer be permissible with very few exceptions. One significant question is: to which degree does the transition from SnPb alloy to the next materials change the board cleaning process?
  Published in EPP Europe, March 2004
  
  
• Cleaning Underneath 4 Mil Standoffs
  The miniaturizing process has not reached its physical limits in the electronics industry. The increase in component complexity results in a continuous decrease in standoff spacing between the components and the substrate’s surface. This article looks at mechanical agitation cleaning systems for best cleaning results.
  Published in Global SMT & Packaging, July 2003
  
  
• High-Performance Assemblers Slip Back
  For manufacturers of high-performance electronics, the trend has been to clean the assemblies. This article compares the technological and cost-related aspects of no-clean and clean manufacturing.
  Published in EPP Europe, November 2003
  
  
• True costs of In-Line Cleaning
  The only true method of analyzing a cleaning process is to use a systems approach, which analyzes the cleaning process with regard to its four main aspects: Substrate being cleaned, contamination being removed, cleaning agent used and cleaning equipment being used.
  Published in EP & P, April 2003
  
  
• Cleaning Solder Frames: Solving a Costly Problem
  ATRON® SP 200 is an aqueous-alkaline cleaning agent specially developed for the removal of crusted flux residues from solder frames and condensation traps
  Published in EPP Europe, August 2002
  
  
• Stencil Cleaning
  A cleaning agent capable of removing excess solder paste, adhesives and flux residues in an automatic stencil process was developed through the described process.
  Published in SMT Magazine, May 2001

- Climatic reliability

• Cleaning Eutectic and Lead-free in one Process
  Lead-free soldering has brought has brought about several changes. This article determines if manufacturers can use existing chemistry based cleaning processes to clean eutectic and lead-free alloys in the same equipment.
  Published in SMT Magazine
  
  
• In-field Assembly failures – Expensive and Avoidable?
  The interaction of cleaning with protective coating, together with peak-point analysis, all contribute to the fulfillment of long-term reliability requirements.
  Published in SMT Magazine, January 2003
  
  
• Lead-free and No Clean: A contradiction of Terms?
  Studies in the climatic reliability of various lead-free pastes reveal an increasing threat at ambient conditions to the long-term reliability of lead-free solder joints. This article highlights the potential quality problems that can be detected and avoided.
  Published in SMT Magazine, October 2002
  
  
• Preventing Contamination-caused Assembly Failure
  Suitable cleaning methods with effective monitoring of all processes can stem the ride of residue-induced board malfunctions.
  Published in SMT Magazine, March 2002 
  
  
• Humidity and Pollution Effects in Electronic Equipment
  The use if electronic components and sensors in humid atmosphere is on the increase. A typical example is the use in cars. This paper describes the failure mechanisms of electrochemical migration and leakage currents by corrosion.
  Published: Cees Publication “Climatic and Atmospheric Pollution. Effects on Materials and Equipment”