White Papers

Check the box next to each paper you want to download. You may download as many papers as you wish. After selecting papers and completing the contact information form on this page, the paper(s) will be e-mailed to you at the e-mail address you provide.

Papers about Cleaning

• Ionic Cleanliness Testing Research of Printed Wiring Boards for Purposes of Process Control

  by Mike Bixenman D.B.A., Steve Stach, Dr. Ning-Cheng Lee

  Ionic Cleanliness testing machines are designed to determine the total ionic content extractable from the printed wiring board for purposes of process control. The conductivity of the extract solution is measured and the results are expressed as sodium chloride equivalence per unit area. The problem with this method is two fold: 1.) Many of today’s low residue flux and lead-free flux residues are not soluble in the extract solution. 2.) Contamination of concern is with site specific components, from which contamination does not correlate to the area of concern. The purpose of this study is to research low residue and lead-free flux structures, identify solvent compositions that will dissolve these residue types, and offer options for performing both bulk and site specific ionic cleanliness testing methods.

  lead-free, Cleaning, flux residue, flux, soldering, solder, solder paste, SMT

  [Permanent Link to this Paper]

  Posted on 1 Jan 2009

• Lead-Free Flux Technology and Influence on Cleaning

  by Dr. Ning-Cheng Lee

  Lead-free flux technology for electronic industry is mainly driven by high soldering temperature, high alloy surface tension, miniaturization, air soldering due to low cost consideration, and environmental concern. Accordingly, the flux features desired included high thermal stability, high resistance against burn-off, high oxidation resistance, high oxygen barrier capability, low surface tension, high fluxing capacity, slow wetting, low moisture pickup, high hot viscosity, and halogen-free. For each of the feature listed above, corresponding desired chemical structures can be deduced, and the impact of those structure on flux residue cleanability can be speculated. Overall, lead-free flux technology results in a greater difficulty in cleaning. Cleaner with a better matching solvency for the residue as well as a higher cleaning temperature or agitation are needed. Alkaline and polar cleaner are often needed to deal with the larger quantity of fluxing products. Reactive cleaner is also desired to address the side reaction products such as crosslinked residue.

  lead-free, flux, flux residue, solder, soldering, cleaner, Cleaning, SMT

  [Permanent Link to this Paper]

  Posted on 1 Jan 2009

• New Developments in High Performance Solder Products for Power Die Assemblies

  by G. Wilson, Mike Fenner, Andy C. Mackie PhD

  The use of special purpose solder pastes in power die attach is well-established offering low voiding and reliable bonding in volume manufacturing. However these materials are designed around high lead alloys and applied by dispensing. IGBT circuits are made by printing high tin alloys to multiple die sites, placing die and reflowing in a process more similar to conventional PCB or hybrid thick film assembly. This paper describes how the opportunity was taken to make use of the latest developments in Pb-free SMT flux technology and re- optimize them to the different requirements of IGBT die attach.

  We rehearse the attributes and requirements of IGBT circuitry and then go on to show how a high performance Pb-Free solder paste has been developed to meet the requirements of large power die attachment (LDA) in IGBT module manufacturing processes. The paste has excellent print and handling characteristics and routinely returns less than 0.5% voiding under large die over a wide range of vacuum reflow conditions. The flux vehicle chemistry offers ease of cleaning to be compatible with the next stage processes of wire bonding & circuit encapsulation.

  Cleaning, wire bonding, void free, die attach, IGBT, solder paste

  [Permanent Link to this Paper]

  Posted on 8 Mar 2010

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