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Mechanical properties of thin-film polymers often dictate the mechanical integrity and performance of microelectronic assemblies. For example, excessive interfacial stress between the polymer and signal via induced by thermal mismatch will lead to delamination of the interface or via cracking. This type of problem becomes more aggravated as dimensions of assemblies continue to shrink. In order to define the optimal design variables and process windows, the mechanical properties of polymer thin films throughout the complete process cycle must be carefully characterized. This paper will first review the experimental techniques commonly adopted in the mechanical measurements of thin-film polymers. Then, it will focus on the most difficult part of the mechanical characterization which is along the out-of-plane (Z) direction. Experimental set-up using the capacitance gauge will be introduced. Critical mechanical properties of polymers will be discussed. For the purpose of illustration, two polymers are chosen as examples. A BPDA-PDA polyimide is used to demonstrate mechanical characterization before melting whereas a PTFE-SiO2 composite is chosen to demonstrate the rheological characterization after melting. Before melting, mechanical behaviors such as the stress-strain curve, creep, relaxation, coefficient of thermal expansion, strain-rate dependence, and temperature dependence are discussed. After melting, the rheological behavior and the effect of aspect ratio measured by a squeezing flow experiment are addressed. Constitutive descriptions are proposed. The functional dependency between stress (pressure), strain (displacement), time, and temperature are characterized. A comparison between the numerical simulations and the experimental measurements is also presented.

Strain controlled fatigue tests have been performed on two types of heavily filled epoxy corrosion protection coating sprayed onto a 6 mm steel substrate. Fatigue cycling was performed at R ratios of 0 and-1. The two coatings differed in their formulation and the major differences in mechanical performance were in their static strain to first crack development and their fracture toughness, where Coating A was significantly tougher than coating B. During strain cycling coating crack development was monitored using optical observations and surface replicas. It was found that in both coatings surface crack development began soon after the onset of cycling and proceeded via growth of surface channelling cracks and multiple initiation of new cracks. Detailed studies were made of crack development morphology and its relation to coating type and to the applied strain range. A definition of coating life as the first appearance of a 2 mm surface crack length was used. This represented the end of the life where the coating protected the substrate. Before this life was achieved, crack growth rates of single cracks were invariant with crack length. After this point further crack growth, multiple cracking and crack to crack interactions took place. Cracking in this region could be characterised with a new total crack length parameter shown to be strongly dependent on applied strain range.