In this paper, a fast moisture sensitivity level (MSL) qualification method and a fast moisture characterization method are discussed. The fast moisture characterization uses a stepwise method to obtain more reliable and more material moisture properties. The established relationships for moisture diffusion coefficients and moisture saturation levels with respect to the temperature and relative humidity can be used to predict moisture properties in the MSL range. Fast moisture sensitivity level qualification is accomplished with the aid of simulation combined with the characterized moisture diffusion properties. Moisture absorption processes at different conditions are simulated using a 3D model at conditions according to the moisture sensitivity test levels. Simulation of weight change at different condition and simulation of local moisture concentration are performed and compared between different conditions. Simulations show that at 696 h preconditioning time at 30°C/60%RH for MSL level 2a can be decreased to 42 h at 85°C/85%RH. Time required for package reliability and moisture sensitivity analysis is largely shortened.@en

Interface delamination is one of the most important issues in the microelectronic packaging industry. Silver filled die attach is a typical adhesive used between the die and copper die pad for its improved heat dissipation capacity. Delamination between die attach and die pad will severely impact the heat conduction and result in product failure. In order to predict this delamination, interface properties should be characterized. Tri-material, copper-die attach-EMC, samples are made according to the package processes. A four point bending test system is established in order to perform delamination tests at different temperatures using a universal tester Zwick/Roell Z005. In addition, a Keyence optical system is mounted to capture a series of pictures during the delamination processes. This will provide the delamination geometry information needed for determining the interface properties. Four point bending tests have been performed at room temperature, 40, 60, 85, and 150ºC respectively. In addition pre conditioning sample are also tested at room temperature and 85ºC respectively after 48 hours pre conditioned at 85ºC/85%RH. . Experiments show that the ¿critical delamination load¿ decreases steadily with temperature increasing. Experiments also show moisture has no effects on the ¿critical delamination load¿ compared with the dry samples tested at the same temperatures. This means that moisture has no effects on the interface toughness between copper and die attach. To quantify the interface properties, numerical simulations of the four point bending test have been performed by using a finite element model comprising cohesive zone elements which will describe the transient delamination process during the four point bending tests. Correspondently, the interface toughness decreases from 26.5J/m2 at room temperature to 1.9J/m2 at 150ºC as calculated from the cohesive zone element model. These results show that temperature has a large effect on the interface toughness. By means of an extensive model parameter sensitivity study, combined with the measured delamination length in horizontal direction along the copperdie attach interface at room temperature critical opening value has been determined.@en

Moisture induced failures in the plastic encapsulated packages are one of the most important failure mechanisms in microelectronics. These failures are driven by the mismatch between different material properties, such as CTA, CME (Coefficient of Moisture induced Expansion) and degradation of interface strength caused by moisture absorption of polymer materials. Therefore, it is critical to know how much moisture exists in packaging materials, the moisture distribution in the package and hygro-mechanical effects on the package. In this paper moisture diffusion, moisture distribution and hygro-mechanical effects are simulated at the following conditions: 85°C/85%RH, 60°C/60%RH and 85°C/dry, 60°C/dry using 2D SiP (System in Package) finite element model.@en

In this paper we determined the water uptake of a die attach and a molding compound. The two types of polymer which were selected are a die attach filled with silver particles and an epoxy molding compound filled with silica particles. The water absorption is carried out in an adjustable thermal and humidity chamber, SGA-100, at different temperatures and humidity levels. Moisture absorption equilibrium of test data were obtained by experiment. The moisture absorption equilibrium prediction equation was modeled by using the extrapolated experimental data. Diffusion coefficients at different temperature were obtained from the moisture absorption experiments.@en

Moisture induced failure in plastic encapsulated packages is one of the most important failure mechanisms in microelectronics. This failure is driven by the mismatch between different material properties such as CTE, CME (Coefficient of Moisture induced Expansion) caused by moisture absorption in plastic packaging materials. Therefore, it is important to know moisture effects on mechanical properties of plastic packaging materials, especially CME. Moisture induced expansion can be calculated using epsilon = beta times C, here epsilon is the strain, beta is the CME and C is the moisture concentration. Traditionally using the combined TGA (Thermal Gravimetric Analyzer) technique, the CME of plastic packaging materials is characterized. TGA is used to measure the weight change and TMA is used to measure the length change. By combining both the TMA and TGA measurements, the CME can be determined. This method is often used in industry and it is observed that the CME value is often overestimated. In order to get precise CME values a high precision DMA (Dynamic Mechanical Analyzer) is used to measure the length change of a sample while a humidity generator is used to regulate the relative humidity. Therefore, temperature and relative humidity are controlled in the DMA chamber and can be used to measure the length change under different relative humidity conditions. CME values measured by the DMA plus humidity method are much lower than that of the TGA/TMA method. In order to find out which method is more reliable, a third experiment was done. A bi-material sample is created to verify our measured CME value. TDM equipment (oven + camera system to detect vertical displacement of the sample) is used to measure the warpage of the bi-material sample. Using our measured CME value, finite element model simulation result shows that the hygro-mechanical warpage of the model fits well with TDM test result.@en

Four types of polymer which were selected are EPNI180 and EPNI180 filled with 40%, 50% and 65% fused silica. The moisture absorption is carried out in an adjustable thermal and humidity chamber at different temperature and humidity. The diffusion coefficients at different conditions were obtained through the early stage moisture absorption tests. The moisture absorption was revealed to show the Fickian type of diffusion for four types of samples. In addition the most important issue, the relation between moisture content and filler content is discussed and is revealed. Using this relation, we can expect moisture content in the sample with different moisture contents under different temperature and relative humidity conditions. Another issue, the relation between the viscoelasticity and filler content, is revealed. We find that the filler has a great effect on the viscoelasticity. The storage modulus is increased 30% by adding 65wt% fused silica.@en

Generally, the viscoelastic properties of packaging materials used in the simulation models are obtained from the materials after postcuring. However these properties were observed to change during humidity conditioning and the thermal cycling. Two kinds of packaging materials are tested, one is molding compound and another is underfill. All samples are cured according to the curing procedure, postcured at 180ºC. Before the test, first the samples are pre-dried at 125ºC for 24 hours and then preconditioned at 60ºC/60%RH for 40 hours. Secondly, one reflow at 260ºC. Finally, all samples are subjected to thermal cycling. Thermal cycling temperature range is from -65ºC to 150ºC and every cycle is finished in 30 minutes. For the DMA test, a TA instrument Q800 is used. Test results show the glass modulus, rubber modulus and glass transition temperature increase with the number of thermal cycles. This change in materials after humidity and thermal treatment is here referred to as aging. The finite element software Marc is used to simulate the internal change of stress and displacement. The simulation result shows that the total warpage has increased a little at the corner of passive die, which is where the critical cracks and crazes were found in our qualification tests. And the Von Mises stresses increase after thermal cycling.@en

For the purpose of rapidly identifying the functional weak points of SiP products and defining appropriate design rules, a new methodology is proposed to achieve fast reliability qualification.@en

One type of polymer EPN1180 is slected for the hygroscopic swelling tests and the sample is made in the thickness of 30 mumeter. Coefficient of thermal expansion is tested by using DMA Q800 and coefficient of moisture expansion is tested by using DMA Q800 jointed with a humidity generator. Three conditions temperature, 50 degrees C, 60 degrees C and 70 degrees C, and different relative humidity with 20RH% steps are used for the tests and moisture induced expansion is characterized. The characterized equation can be used to expect the moisture-induced expansion at temperature between 0 degrees C and 100 degrees C, at relative humidity between 0RH% and 100RH% for this epoxy. This new method is convenient than that of the old method and easily is used to characterize other polymers. In addition hygroscopic effect on the viscoelasticity is tested and characterized. The storage modulus is linear decreased with the increase of relative humidity at certain temperature.@en

Time to market is becoming one of the most important factors because of the fierce market competition. However, traditional reliability and interface toughness characterization tests take a very long time. For example, moisture sensitivity level assessment (MSL 1) will take 168 hours pre conditioning at 85C/85%RH and tradition thermal cycling takes even longer time. The long preconditioning times are chosen to ensure that also the thicker section of a package are completely saturated. Thinner packages, however, are already saturated after one to two days. In this study, we therefore investigated whether it would be possible to speed up the qualification process by shortening the preconditioning time. We focus in particular on the interface toughness. From our four point bending test and analysis, it is found that temperature has great effects on the interface toughness and moisture also has small effects on the interface toughness. In order to do the fast qualification test, thermal shock cycling tests combined with moisture absorption are performed. Experiments show that moisture can speed up the delamination.@en

The use of the non-hermetic material for electronic packaging does raise a potential concern, i.e. moisture induced interfacial delamination and pop corning during reflow. Therefore, it is very important we can correctly model the moisture absorption property. In this study, moisture absorption and desorption properties of three kinds of package materials were investigated. Moisture absorption equilibrium weight gain and diffusion coefficient at different temperature and different humidity are characterized. Moisture absorption processes are simulated using a 3D model at conditions according to the moisture sensitivity test levels. Finally moisture absorption is verified by our research carrier.@en