Volume 7, Issue 9 (October 2010)

    Empirical Modeling of the Time-Dependent Structural Build-up of Lead-Free Solder Pastes Used in the Electronics Assembly Applications

    (Received 17 February 2010; accepted 31 July 2010)

    Published Online: 2010

    CODEN: JAIOAD

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    Abstract

    Solder paste is the primary bonding material used in the assembly of surface mount devices in electronics industries. It generally has a flocculated structure, which may break-down on shearing and slowly rebuild at rest. The proper characterization of the time-dependent rheological behaviors of solder pastes is crucial for establishing the relationships between the pastes’ structure and flow behavior and for correlating the physical parameters with paste printing performance. In this paper, we present a novel method that has been developed for characterizing the time-dependent and non-Newtonian rheological behavior of solder pastes and flux mediums as a function of shear rates. The objective of the study reported in this paper was to investigate the thixotropic build-up behavior of solder paste and flux mediums. The stretched exponential model has been used to model the structural changes during the build-up process and to correlate model parameters with the paste printing process. As expected, for solder paste samples, the rate of structural recovery was found dependent on the applied shear rate. The model parameters, such as equilibrium viscosity and characteristic time, have been correlated with the shear-thinning and slumping behaviors of solder paste during the stencil printing process.


    Author Information:

    Mallik, S.
    Electronic Manufacturing Engineering Research Group, Medway School of Engineering, Univ. of Greenwich at Medway, Kent,

    Ekere, N. N.
    Electronic Manufacturing Engineering Research Group, Medway School of Engineering, Univ. of Greenwich at Medway, Kent,

    Bhatti, R.
    Electronic Manufacturing Engineering Research Group, Medway School of Engineering, Univ. of Greenwich at Medway, Kent,


    Stock #: JAI103043

    ISSN: 1546-962X

    DOI: 10.1520/JAI103043

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    Author
    Title Empirical Modeling of the Time-Dependent Structural Build-up of Lead-Free Solder Pastes Used in the Electronics Assembly Applications
    Symposium , 0000-00-00
    Committee F01