The last post introduced the concept of using fumed silica as a rheology modifier to tailor the dispensing of many types of adhesives used in electronic applications.  In the image in the top right in the figure above shows a die attach adhesives dispensed on a PBGA substrate.  After dispensing, the adhesives retain the “snowflake” or “asterisk” dispensing pattern.  The ... [Click to Continue...]

The last post described how to measure the viscosity-shear rate relationship using either a cone-and-plate or a parallel plate rheometer using a shear rate sweep.  An example is shown above.  This post covers how the viscosity profile influences the dispensing process and provides a short introduction to viscosity modifiers used to control the shear thinning and yield ... [Click to Continue...]

The last post described some of the potential pitfalls of the controlled stress measurements.  Controlled stress measurements are good if you require a precise yield point measurement.  An example would be if you were designing the yield point for a particular dispensing application.  The point-to-point creep test would allow the yield point to be measured accurately.  If on ... [Click to Continue...]

The last post described the controlled stress experiment.  In the image above, a stress was applied to the sample and the deformation as a function of time (strain-rate) was measured at steady state.  There are two measurement modes for controlled stress curves: Manual: a series of creep measurements (which was used above) Automatic: Flow or viscometry mode in a ... [Click to Continue...]