Rheometers are used to determine the viscosity by measuring the stress at a known shear-rate or measuring the shear rate at a known stress.  There are two types of torsional rheometers: Controlled strain (most common) Controlled stress In the case of the strain controlled rotational rheometer, a typical configuration is shown in the following figure: In this ... [Click to Continue...]

The rheological properties of polymers used in electronic packaging applications spans a wide range of fluid types and viscosity ranges.  In the uncured state, many adhesives, coatings, mold compounds, and underfills have interesting rheological behavior.  Many of these types of materials are highly filled to achieve the desired mechanical properties such as low coefficient of ... [Click to Continue...]

I will start this post with a short personal story about how I got into electronic packaging and specifically, rheology in electronic packaging.  When I was a fourth year graduate student at Northwestern I started looking for a job at the typical places an industrial polymer rheologist might consider, like Dow, DuPont, GE Plastics and others.  My thesis advisor, Prof. William ... [Click to Continue...]

Figure 1.  Build-up material roadmap (source: Ajinomoto Fine-Techno Co. Inc.) The last post described the chemistry and types of build-up films typically used in the electronic packaging industry.  We also touched on the build-up material roadmap which showed the various complex packaging substrates that are enabled using build-up film technology as shown in Figure 1.  ... [Click to Continue...]