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

Volume 7, Issue 9 (October 2010)

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ISSN: 1546-962X
CODEN: JAIOAD
Published Online: 2 September 2010
Page Count: 12

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

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,

(Received 17 February 2010; accepted 31 July 2010)

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.

Keywords:
solder pastes, lead-free, stretched exponential model, flux, rheology, time-dependent behaviors

Paper ID: JAI103043
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

		SEDL / Journals / Journal of ASTM International (JAI) / Citation Page Volume 7, Issue 9 (October 2010) Click here to download this paper now for $25 PDF (2.0M) View License Agreement ISSN: 1546-962X CODEN: JAIOAD Published Online: 2 September 2010 Page Count: 12 Empirical Modeling of the Time-Dependent Structural Build-up of Lead-Free Solder Pastes Used in the Electronics Assembly Applications 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, (Received 17 February 2010; accepted 31 July 2010) 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. Keywords: solder pastes, lead-free, stretched exponential model, flux, rheology, time-dependent behaviors Paper ID: JAI103043 DOI: 10.1520/JAI103043 ASTM International is a member of CrossRef. 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