Mechanical properties of molding compounds (MCs) under different moisture conditions and in a wide temperature range

In this work, fracture toughness and flexural properties including flexural modulus, flexural stress/strain of 2 molding compounds GMC-1 and GMC-2 were investigated in a temperature range from -60°C to 260°C, whereby three-point-bending method was applied to all tests. To observe the moisture effect on those mechanical properties, specimens were soaked under 85°C/85%RH conditions for 168 hours following the moisture reflow standards (for moisture tests) or baked for at least 24 hours (for dry tests) before tests. The obtained results are then compared with each other. It is seen that at high temperature, rupture stress of the 2 MCs at 85°C/85% RH condition could be 40%-50% lower than those at dry conditions. The remarkable reduction of material strength will largely promote the failure in the packages considering that modulus change does not change significantly the stress level. It is also found that using the material data for GMC-1 provided by vendor could underestimate maximum Von Mises stress by around 15% at high temperature. Similarly, fracture toughness decreases greatly with temperature and moisture content. At 260°C, maximum Von Mises stress could be reduced by 40% due to the moisture take-up change from dry to wet (MSL1).