White Papers

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Papers about no-clean flux

• No-Clean Flux Residue and Underfill Compatibility Effects on Electrical Reliability

  by Eric Bastow

  No-clean soldering processes dominate the commercial electronics manufacturing world. With the explosion of growth in handheld electronics devices, manufacturers have been forced to look for ways to reinforce their assemblies against the inevitable bumps and drops that their products experience in the field. One method of reinforcement has been the utilization of underfills to “glue” certain surface mount devices (SMDs) to the PCB. This provides additional mechanical strength over and above the soldered connections. Bumped SMDs attached to the PCB with a no-clean soldering process offer the unavoidable scenario of the underfill coming in contact with a flux residue. This may or may not create a reliability issue. No-clean solder paste flux chemistries can vary. Some have halogens and others do not. Some have standard residues and others have residues optimized for pin probing. There are also a number of underfill chemistries on the market. Furthermore, underfill curing conditions vary depending on whether the SMDs are exposed on the surface of the PCB or underneath an RF shield. This paper will discuss an experiment designed to measure the electrical reliability of various combinations of underfill and no-clean flux residues, as measured with J-STD-004B SIR (IPC-TM-650 2.6.3.7).

  Apex 2012, solder paste, no-clean flux, flux residue

  [Permanent Link to this Paper]

  Posted on 1 Mar 2012

• The Effects of Flux Residues on Electrical Reliability

  by Eric Bastow

  With the predominance of no-clean soldering processes and ever decreasing component standoff, the industry has had to consider the reliability of, what may be, partially activated or "gooey" flux residues under component bodies. Similarly, questions have also risen about the reliability of flux residues resulting from the reflow of no-clean solder pastes that are "entrapped" under RF shields or "cans", where escape of the volatile ingredients of the flux is greatly hindered. In this paper, discussion will be made regarding an experiment designed to mimic the aforementioned conditions and how these conditions affected the SIR performance of the no-clean flux residues. A variety of no-clean solder paste flux residues will be discussed, including a halogen-containing, Pb-free solder paste flux; a halogen-free, Pb-free solder paste flux; a halogen-free, Pb-free solder paste flux with a residue optimized for pin probing; and a halogen-free SnPb solder paste flux.

  Apex 2011, solder paste, pb-free, halogen-free, no-clean flux, flux residue

  [Permanent Link to this Paper]

  Posted on 11 Apr 2011

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