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.
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 18.104.22.168).
First published in the 2012 IPC APEX EXPO technical conference proceedings.
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