TY - THES

T1 - Characterization of the viscoelastic material properties of FR-4 materials

AU - Zach, Daniel

N1 - embargoed until 19-02-2029

PY - 2024

Y1 - 2024

N2 - Printed circuit boards (PCBs) are crucial in the packaging of electronic devices, providing structural support and electrical connectivity. The demand for smaller, lighter devices has led to the use of multilayer boards (MLBs) made from FR-4 materials, known for their excellent properties. However, harsh environmental conditions pose challenges, and thermally induced stresses impact the reliability of MLBs. This master's thesis focuses on determining the viscoelastic behavior of FR-4 materials, by the use of reliable and time-efficient methods. The specific aim is to characterize the viscoelastic properties of two different FR-4 resin materials, emphasizing accelerated creep characterization. A test methodology based on thermo-mechanical tests and short-term creep tests, coupled with polymer-physical extrapolation principles, was established. Experimental approaches included dynamic mechanical analysis (DMA) at various frequencies and temperatures, constructing time-dependent master curves according to the time-temperature superposition principle. Additionally, short-term tensile creep tests at different temperatures and load levels were conducted using digital image correlation (DIC), constructing creep modulus master curves up to 1000 hours following the stepped-stress method (SSM). For a reproducible and user-independent evaluation of the DMA results, special evaluation programs using the Python programming language were developed, which enable the automated generation of master curves for the viscoelastic property functions. The comparison between experiments provides detailed insights into the reliability of each test method, ensuring a meaningful characterization of viscoelastic behavior over a wide range of loading times. Particularly, the developed test and evaluation method based on temperature and frequency dependent DMA measurements was shown to be a useful tool for the efficient generation of creep modulus master curves. The additional determination of basic material properties, such as glass transition temperature (Tg), coefficient of thermal expansion (CTE), and mechanical short-term properties provided a comprehensive characterization of application relevant properties for the two FR 4 resins investigated. The developed test method, combined with automated evaluation routines, offers a time-efficient approach to estimate long-term viscoelastic behavior, supporting efficient material selection and product development.

AB - Printed circuit boards (PCBs) are crucial in the packaging of electronic devices, providing structural support and electrical connectivity. The demand for smaller, lighter devices has led to the use of multilayer boards (MLBs) made from FR-4 materials, known for their excellent properties. However, harsh environmental conditions pose challenges, and thermally induced stresses impact the reliability of MLBs. This master's thesis focuses on determining the viscoelastic behavior of FR-4 materials, by the use of reliable and time-efficient methods. The specific aim is to characterize the viscoelastic properties of two different FR-4 resin materials, emphasizing accelerated creep characterization. A test methodology based on thermo-mechanical tests and short-term creep tests, coupled with polymer-physical extrapolation principles, was established. Experimental approaches included dynamic mechanical analysis (DMA) at various frequencies and temperatures, constructing time-dependent master curves according to the time-temperature superposition principle. Additionally, short-term tensile creep tests at different temperatures and load levels were conducted using digital image correlation (DIC), constructing creep modulus master curves up to 1000 hours following the stepped-stress method (SSM). For a reproducible and user-independent evaluation of the DMA results, special evaluation programs using the Python programming language were developed, which enable the automated generation of master curves for the viscoelastic property functions. The comparison between experiments provides detailed insights into the reliability of each test method, ensuring a meaningful characterization of viscoelastic behavior over a wide range of loading times. Particularly, the developed test and evaluation method based on temperature and frequency dependent DMA measurements was shown to be a useful tool for the efficient generation of creep modulus master curves. The additional determination of basic material properties, such as glass transition temperature (Tg), coefficient of thermal expansion (CTE), and mechanical short-term properties provided a comprehensive characterization of application relevant properties for the two FR 4 resins investigated. The developed test method, combined with automated evaluation routines, offers a time-efficient approach to estimate long-term viscoelastic behavior, supporting efficient material selection and product development.

KW - FR4-Materialien

KW - Epoxidharze

KW - Viskoelastizität

KW - Zeit-Temperatur Superpositionsprinzip

KW - Beschleunigte Kriechversuche

KW - SSM

KW - FR4-Materials

KW - Epoxy Resin

KW - Viscoelasticity

KW - Time-Temperature Superposition Principle

KW - Accelerated creep test

KW - SSM

U2 - 10.34901/mul.pub.2024.092

DO - 10.34901/mul.pub.2024.092

M3 - Master's Thesis

ER -