A dual stage model of anomalous moisture diffusion and desorption in epoxy mold compounds

Abstract

Absorption and desorption tests were conducted on five distinct commercial epoxy mold compounds (EMCs) used in electronic packaging. For absorption, the samples were subjected to 85°C /85% relative humidity and 60°C /85% relative humidity soaking. Desorption conditions were above glass transition temperature at 140°C and 160°C. A dual stage model is developed in this paper for both absorption and desorption processes. Both stages in moisture absorption and desorption, i.e., Fickian diffusion and relaxation process, are described mathematically using a combination of Fickian terms. The models generated reasonable results for the diffusive properties and displayed outstanding experimental fits. All five compounds have shown strong non-Fickian diffusion behaviors, which were further demonstrated by experiments with different thicknesses. For absorption, results show Fickian diffusion is significantly faster than non-Fickian diffusion. Saturated moisture concentration associated with Fickian-stage diffusion is independent of temperature if it is below glass transition temperature. Sample thickness played a major role in diffusive behavior in the second stage where non-Fickian diffusion occurs. For desorption, higher temperature corresponds to less percentage of the permanent residual moisture content. At 160°C, 90% of the initial moisture for all samples could be diffused out within 24 hours, following a modified Fickian diffusion process. The dual stage model developed in this paper provides a foundation for modeling anomalous moisture diffusion behavior using commercial finite elemental method software.

Finite element modeling of anomalous moisture diffusion with dual stage model

“…The experimental results of moisture absorption for epoxy mold compounds (EMCs) at 85C/85%RH, followed by desorption at the same temperature (85C/0%RH) show that moisture absorption experiences twostage diffusion, and the non-Fickian diffusion is nonreversible at the same temperature, at least for a period of 2 weeks. However, higher temperature from 100C to 260C allows more bound water removed, and experimental data also show reasonable fit following Fickian diffusion model in reflow process [4,5].…”

“…A dual-stage diffusion model in terms of Fickian parameters for both stages, has been developed recently by one of the authors [4,11]. This paper will report the finite element implementations of this model with commercial finite element software.…”

Diffusion of polar and non-polar molecules in a polymer membrane

“…Качественно такая зависимость показывает, что нестационарный режим, при котором создаются кон-центрационные профили в мембране, будет протекать тем больше, чем меньше будет D [8,9].…”

“…С другой стороны, различия между эксперимен-тальными кривыми сорбции и десорбции показывают отличие кинетики процесса от Фиковской диффузии, когда коэффициент диффузии зависит от концентра-ции [9].…”

Thermomechanical and hygroelastic properties of an epoxy system under humid and cold-warm cycling conditions

“…Epoxy-based materials are utilized in many engineered structures, ranging from large civil infrastructures [1] to microelectronics [2] because they offer strong mechanical properties along with thermal and chemical stability. An important field of application is the one of carbone/epoxy composites that exhibit adaptability during the design [3] and high-level integration during the manufacturing process [4].…”