Inversion for Multi-Parameter Depth-Profiles: Thermal Conductivity and Thermal Impedance

1999 ◽  
pp. 619-626
Author(s):  
M.H Xu ◽  
J. C. Cheng ◽  
S.Y Zhang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Impedance ◽  
Depth Profiles

Analysis of the Tikhonov regularization to retrieve thermal conductivity depth-profiles from infrared thermography data

2010 ◽  
Vol 108 (6) ◽  
pp. 064905 ◽  
Author(s):  
Estibaliz Apiñaniz ◽  
Arantza Mendioroz ◽  
Agustín Salazar ◽  
Ricardo Celorrio
Keyword(s):  
Thermal Conductivity ◽  
Infrared Thermography ◽  
Tikhonov Regularization ◽  
Depth Profiles

scholarly journals The Influence of Soldering Profile on the Thermal Parameters of Insulated Gate Bipolar Transistors (IGBTs)

2021 ◽  
Vol 11 (12) ◽  
pp. 5583
Author(s):  
Adrian Pietruszka ◽  
Paweł Górecki ◽  
Sebastian Wroński ◽  
Balázs Illés ◽  
Agata Skwarek
Keyword(s):  
Thermal Conductivity ◽  
Solder Joint ◽  
Bipolar Transistors ◽  
Thermal Parameters ◽  
Temperature Profiles ◽  
Insulated Gate Bipolar Transistors ◽  
Thermal Impedance ◽  
Soldering Process ◽  
Hot Air ◽  
Soldering Technology

The effect of solder joint fabrication on the thermal properties of IGBTs soldered onto glass-epoxy substrate (FR4) was investigated. Glass-epoxy substrates with a thickness of 1.50 mm, covered with a 35 μm thick Cu layer, were used. A surface finish was prepared from a hot air leveling (HAL) Sn99Cu0.7Ag0.3 layer with a thickness of 1 ÷ 40 μm. IGBT transistors NGB8207BN were soldered with SACX0307 (Sn99Ag0.3Cu0.7) paste. The samples were soldered in different soldering ovens and at different temperature profiles. The thermal impedance Zth(t) and thermal resistance Rthof the samples were measured. Microstructural and voids analyses were performed. It was found that the differences for different samples reached 15% and 20% for Zth(t) and Rth, respectively. Although the ratio of the gas voids in the solder joints varied between 3% and 30%, no correlation between the void ratios and Rth increase was found. In the case of the different soldering technologies, the microstructure of the solder joint showed significant differences in the thickness of the intermetallic compounds (IMC) layer; these differences correlated well with the time above liquidus during the soldering process. The thermal parameters of IGBTs could be changed due to the increased thermal conductivity of the IMC layer as compared to the thermal conductivity of the solder bulk. Our research highlighted the importance of the soldering technology used and the thermal profile in the case of the assembly of IGBT components.

Photothermal estimation of thermal conductivity depth profiles in steel

1997 ◽  
Vol 29 (2) ◽  
pp. 165-169
Author(s):  
Ton Thi Ngoc Lan ◽  
Heinz-Günter Walther ◽  
Do Tran Son
Keyword(s):  
Thermal Conductivity ◽  
Depth Profiles

AlGaN Microwave Power HFETs on Insulating SiC Substrates

1999 ◽  
Vol 572 ◽  
Author(s):  
Gerry Sullivan ◽  
Ed Gertner ◽  
Richard Pittman ◽  
Mary Chen ◽  
Richard Pierson ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Total Power ◽  
Thermal Impedance ◽  
Rf Power ◽  
Power Performance ◽  
Large Area ◽  
High Power Microwave ◽  
Sapphire Substrates ◽  
Pulsed Measurements ◽  
Power Microwave

ABSTRACTAIGaN HFETs are attractive devices for high power microwave applications. Sapphire, which is the typical substrate for AlGaN epitaxy, has a very poor thermal conductivity, and the power performance of AlGaN HFETs fabricated on sapphire substrates is severely limited due to this large thermal impedance. We report on HFETs fabricated on high thermal conductivity electrically insulating SiC substrates. Excellent RF power performance for large area devices is demonstrated. On-wafer CW measurements at 10 GHz of a 320 micron wide FET resulted in an RF power density of 2.8 Watts/mm, and measurements of a 1280 micron wide FET resulted in a total power of 2.3 Watts. On-wafer pulsed measurements, at 8 GHz, of a 1280 micron wide FET resulted in a total power of 3.9 Watts. Design of a hybrid microwave amplifier will be discussed.

Formulation of Percolating Thermal Underfill by Sequential Convective Gap Filling

2011 ◽  
Vol 2011 (DPC) ◽  
pp. 001621-001648 ◽  
Author(s):  
T. Brunschwiler ◽  
J. Goicochea ◽  
H. Wolf ◽  
C. Kuemin ◽  
B. Michel
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Heat Dissipation ◽  
High Viscosity ◽  
Thermal Impedance ◽  
Gap Filling ◽  
Carrier Fluid ◽  
Filling Time ◽  
Small Pore ◽  
The Matrix

In 3D chip stacks, heat dissipation through wiring layers and the bonding interface contributes to the total temperature gradient. The effective thermal impedance of micro solder-ball arrays filled with a poorly-conducting silica underfill can be as high as 30 K*mm2/W, three times the value of a thermal grease interface. Efforts to improve the underfill conductivity to 5 W/(m*K) are underway, which would translate into in a significant interface-resistance reduction. To achieve thermal conductivities >1 W/(m*K), alumina particles were introduced in capillary underfills at particle loadings above the percolation threshold, but at these loading levels the high viscosity of the resulting underfill no longer permits capillary filling. We propose a novel sequential gap-filling method. Particles are suspended in a carrier fluid at a low concentration (0.1 vol%). Using forced convection, the suspension is injected into the cavity formed between the IC dies by the C4 array. A filter element at the cavity outlet triggers particle accumulation in the cavity. The particles form a percolation network with an effective thermal conductivity of >1 W/(m*K). Next an evaporation step removes the carrier fluid, and the exposed pores between the particles are refilled with a particle-free adhesive using capillary forces. Finally, the matrix is cured at 65 °C. 10x10 mm2 standard and micro-C4 cavities (>30 μm) can be completely filled in 2 min at 0.2 bar, resulting in a homogeneous volumetric fill of 36%. Percolation was identified by SEM inspection. For the micro-C4 arrays filler particles of < 10 μm were used. Uniform particle filling is precluded because of the longer filling time due to the small pore sizes. Particle trapping sites are introduced to form local stacks that provide an additional drainage network to guarantee acceptable filling times. Effective thermal-conductivity values of the percolating thermal underfill method proposed here are reported.

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