Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190397
S. Stoyanov, C. Bailey, R. Waite, C.A. Hicks, T. Golding
Infrared (IR) detector chips and read-out integrated circuits (ROICs) are assembled most commonly through flip-chip bonding technologies and using indium solder interconnects. The resulting 3D stacked die structure is called Focal Plane Array (FPA). This paper details the development of analytical and finite element models of the FPA assembly for both reflow and thermo-compression bonding processes. The models are used to assess the process requirements and feasibility in relation to the IR sensor characteristics and bonding equipment placement accuracy. The results show that high-density ultra-fine pitch FPAs may be feasible to assemble only with thermo-compression bonding technology, and that this will still require very high precision placement machinery with chip alignment accuracy in the order of 1 μm or better. Quality of the formed indium joints and the resulting stand-off height are found to be very sensitive to the alignment of the IR detector chip onto the ROIC. Reflow bonding process is feasible only if the pitch of the pixel array matrix is above certain size. In this instance, the presented model of the chip motion during reflow can be used to predict if self-alignment of the assembled chips occurs.The thermo-mechanical behavior of the FPA under cryogenic temperature cycling load is also presented in the paper. Thermal fatigue damage of indium joints is found to be lower with higher resolution, smaller pitch size pixel array structures despite the larger land size of the detector chip. With detector chip thickness typically <10 μm, the warpage of the FPA is shown to be insensitive to the size of the pixel array.
{"title":"Modelling Indium Interconnects for Ultra Fine-Pitch Focal Plane Arrays","authors":"S. Stoyanov, C. Bailey, R. Waite, C.A. Hicks, T. Golding","doi":"10.1109/ITherm45881.2020.9190397","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190397","url":null,"abstract":"Infrared (IR) detector chips and read-out integrated circuits (ROICs) are assembled most commonly through flip-chip bonding technologies and using indium solder interconnects. The resulting 3D stacked die structure is called Focal Plane Array (FPA). This paper details the development of analytical and finite element models of the FPA assembly for both reflow and thermo-compression bonding processes. The models are used to assess the process requirements and feasibility in relation to the IR sensor characteristics and bonding equipment placement accuracy. The results show that high-density ultra-fine pitch FPAs may be feasible to assemble only with thermo-compression bonding technology, and that this will still require very high precision placement machinery with chip alignment accuracy in the order of 1 μm or better. Quality of the formed indium joints and the resulting stand-off height are found to be very sensitive to the alignment of the IR detector chip onto the ROIC. Reflow bonding process is feasible only if the pitch of the pixel array matrix is above certain size. In this instance, the presented model of the chip motion during reflow can be used to predict if self-alignment of the assembled chips occurs.The thermo-mechanical behavior of the FPA under cryogenic temperature cycling load is also presented in the paper. Thermal fatigue damage of indium joints is found to be lower with higher resolution, smaller pitch size pixel array structures despite the larger land size of the detector chip. With detector chip thickness typically <10 μm, the warpage of the FPA is shown to be insensitive to the size of the pixel array.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122163786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190600
Chun-Pei Chen, Yaxiong Chen, G. Subbarayan, Hung-Yun Lin, S. Gurrum
Metal line ratcheting and passivation cracking in Back End of Line (BEOL) structures are significant reliability concerns for molded packages that are in very wide spread use at the present time. When metal lines plastically deform due to ratcheting, the passivation overcoat accumulates stress at the corner upon temperature cycling and is eventually susceptible to fracture. Since packaging materials’ interaction with the die is the cause of the failure, the problem is inherently multi-scale in nature requiring bridging from package dimension to BEOL length scale. In the present paper, the mechanistic cause for the stress accumulation is elucidated. Furthermore, a global-local modeling strategy is applied to model the passivation crack initiation and growth. A global model with coarse mesh was built of the package. The local region around the interconnect metal line in the die was modeled using boundary conditions extracted from the global model. A novel load decomposition technique is developed to identify the loading mode that best correlates with the experimentally observed fracture. It is shown that shear is the dominant loading mode inducing the die cracks. Furthermore, it is demonstrated that the thermal expansion mismatch between the mold compound as well as the lead frame with the silicon die induces the shear load on the BEOL structure. Owing to the fact that mold compound is applied at a temperature that is higher than that seen during thermal cycling, the direction of the induced shear load is constant regardless of whether the package is heated or cooled. As the metal plastically yields during every temperature cycle, the plastic deformation ratchets, or, accumulates in the same direction over the course of the thermal cycling test. The yielding of metal line results in stiffness reduction, leading to steady accumulation of stress in the passivation corner, causing it to fracture eventually.
{"title":"A Mechanistic Model for Plastic Metal Line Ratcheting Induced BEOL Cracks in Molded Packages","authors":"Chun-Pei Chen, Yaxiong Chen, G. Subbarayan, Hung-Yun Lin, S. Gurrum","doi":"10.1109/ITherm45881.2020.9190600","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190600","url":null,"abstract":"Metal line ratcheting and passivation cracking in Back End of Line (BEOL) structures are significant reliability concerns for molded packages that are in very wide spread use at the present time. When metal lines plastically deform due to ratcheting, the passivation overcoat accumulates stress at the corner upon temperature cycling and is eventually susceptible to fracture. Since packaging materials’ interaction with the die is the cause of the failure, the problem is inherently multi-scale in nature requiring bridging from package dimension to BEOL length scale. In the present paper, the mechanistic cause for the stress accumulation is elucidated. Furthermore, a global-local modeling strategy is applied to model the passivation crack initiation and growth. A global model with coarse mesh was built of the package. The local region around the interconnect metal line in the die was modeled using boundary conditions extracted from the global model. A novel load decomposition technique is developed to identify the loading mode that best correlates with the experimentally observed fracture. It is shown that shear is the dominant loading mode inducing the die cracks. Furthermore, it is demonstrated that the thermal expansion mismatch between the mold compound as well as the lead frame with the silicon die induces the shear load on the BEOL structure. Owing to the fact that mold compound is applied at a temperature that is higher than that seen during thermal cycling, the direction of the induced shear load is constant regardless of whether the package is heated or cooled. As the metal plastically yields during every temperature cycle, the plastic deformation ratchets, or, accumulates in the same direction over the course of the thermal cycling test. The yielding of metal line results in stiffness reduction, leading to steady accumulation of stress in the passivation corner, causing it to fracture eventually.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129838689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190293
M. A. Hoque, Mohammad Ashraful Haq, M. Chowdhury, J. Suhling, P. Lall
Fatigue of solder joints is considered to be one of the major methods of failure in electronic packages. Every electronic assembly is made up of different parts with varying thermal expansion coefficients (CTE). Many applications subject such assemblies to fluctuating temperature conditions. Mismatches in the CTE values of the components of the electronic assembly bring about a cyclic loading on the solder joints. Prolonged cyclic loading subsequently leads to the fatigue failure of these solder joints, thus resulting in the failure of the whole electronic package.The main focus of this investigation was to study the damage accumulated in bulk lead free solder alloys by analyzing the stress-strain behavior and the corresponding constitutive properties in SAC-Bi-Ni-Sb lead free solder (Innolot) subjected to fatigue testing. Circular cross- sectioned solder specimens were reflowed, and these samples were then mechanically cycled. The cyclic stress-strain curves obtained were studied to observe the degradation of hysteresis loop properties (peak stress, hysteresis loop area and plastic strain range) with cycling. In addition, samples with various durations of prior cycling were subjected to tensile and creep testing to determine the effect that mechanical cycling has on the modulus of elasticity, ultimate tensile strength, and creep strain rate of the material. The measured data were compared to the results from previous studies conducted on SAC305 and SAC+Bi (SAC_Q) lead free alloys.
{"title":"Cyclic Stress-Strain and Constitutive Behaviors of SAC-Bi-Ni-Sb Solder Alloys During Fatigue Testing","authors":"M. A. Hoque, Mohammad Ashraful Haq, M. Chowdhury, J. Suhling, P. Lall","doi":"10.1109/ITherm45881.2020.9190293","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190293","url":null,"abstract":"Fatigue of solder joints is considered to be one of the major methods of failure in electronic packages. Every electronic assembly is made up of different parts with varying thermal expansion coefficients (CTE). Many applications subject such assemblies to fluctuating temperature conditions. Mismatches in the CTE values of the components of the electronic assembly bring about a cyclic loading on the solder joints. Prolonged cyclic loading subsequently leads to the fatigue failure of these solder joints, thus resulting in the failure of the whole electronic package.The main focus of this investigation was to study the damage accumulated in bulk lead free solder alloys by analyzing the stress-strain behavior and the corresponding constitutive properties in SAC-Bi-Ni-Sb lead free solder (Innolot) subjected to fatigue testing. Circular cross- sectioned solder specimens were reflowed, and these samples were then mechanically cycled. The cyclic stress-strain curves obtained were studied to observe the degradation of hysteresis loop properties (peak stress, hysteresis loop area and plastic strain range) with cycling. In addition, samples with various durations of prior cycling were subjected to tensile and creep testing to determine the effect that mechanical cycling has on the modulus of elasticity, ultimate tensile strength, and creep strain rate of the material. The measured data were compared to the results from previous studies conducted on SAC305 and SAC+Bi (SAC_Q) lead free alloys.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123998337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190239
D. Deisenroth, M. Ohadi, A. Bar-Cohen
Two-phase embedded cooling has great potential for meeting the increasing thermal management needs of high-heat flux electronics. The use of manifold-microchannels further enhances the effectiveness of embedded cooling while maintaining low pressure drop and pumping power. Previous research has shown that thermodynamic quality drives the thermo-fluid phenomena in the channel, including the prevailing flow regime, the transition to dryout, and the local heat transfer coefficients. The flow phenomena are also strongly dependent on the properties of the working fluid. The current study investigates the performance of FC-72 and R245fa in an enlarged visualization manifold-microchannel, referred to as a "microgap" channel.
{"title":"Heat Transfer and Two-Phase Flow Regimes in Manifolded Microgaps: Performance Comparison Between R245fa and FC-72","authors":"D. Deisenroth, M. Ohadi, A. Bar-Cohen","doi":"10.1109/ITherm45881.2020.9190239","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190239","url":null,"abstract":"Two-phase embedded cooling has great potential for meeting the increasing thermal management needs of high-heat flux electronics. The use of manifold-microchannels further enhances the effectiveness of embedded cooling while maintaining low pressure drop and pumping power. Previous research has shown that thermodynamic quality drives the thermo-fluid phenomena in the channel, including the prevailing flow regime, the transition to dryout, and the local heat transfer coefficients. The flow phenomena are also strongly dependent on the properties of the working fluid. The current study investigates the performance of FC-72 and R245fa in an enlarged visualization manifold-microchannel, referred to as a \"microgap\" channel.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123373149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190467
P. Parida, K. Marston, Kevin P. Drummond, L. Campbell, Yuji Saito, Thanh-Long Phan, Xiao Ping Wu, V. Wuttijumnong
High density microprocessor packages are being deployed to achieve system performance improvements. However, the non-uniform heat dissipation characteristics of such packages has led to renewed interest in vapor chambers and heat pipes for heat spreading and transport. In this paper an approach to model the thermo-hydrodynamic performance of vapor chambers for cooling of microprocessor packages is presented. Model validation against data available in literature showed a very good agreement. The validated model was then used to study the performance sensitivity to vapor chamber design and operational parameters such as wick thickness, wick type, evaporator side heat input and condenser side heat extraction.
{"title":"Thermal Modeling of Vapor Chamber Heat Spreaders and Model Validation","authors":"P. Parida, K. Marston, Kevin P. Drummond, L. Campbell, Yuji Saito, Thanh-Long Phan, Xiao Ping Wu, V. Wuttijumnong","doi":"10.1109/ITherm45881.2020.9190467","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190467","url":null,"abstract":"High density microprocessor packages are being deployed to achieve system performance improvements. However, the non-uniform heat dissipation characteristics of such packages has led to renewed interest in vapor chambers and heat pipes for heat spreading and transport. In this paper an approach to model the thermo-hydrodynamic performance of vapor chambers for cooling of microprocessor packages is presented. Model validation against data available in literature showed a very good agreement. The validated model was then used to study the performance sensitivity to vapor chamber design and operational parameters such as wick thickness, wick type, evaporator side heat input and condenser side heat extraction.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121521470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190341
V. Bissuel, E. Monier-Vinard, Quentin Dupuis, O. Daniel, N. Laraqi, J. Bauzin
The thermal modeling of electronic components is more and more crucial to prevent ageing phenomena when the component temperatures exceed their operating limits.At board level, the analysis of their mutual thermal interactions is done using multi-port RC networks as thermal models. Those compact models are usually extracted from a full physical representation of the component and its thermal behavior for a set of boundary conditions. Unfortunately, that fine description of the device requires a set of information about the package that is often not available.To complete the missing thermal properties, transient measurements of the junction-to-case behavior proved to be very useful. Using step function responses, a set of network identification by deconvolution of RC thermal model was conducted using iterative methods such as Bayesian ones.As a main result, a practical procedure is proposed that allows a direct extraction from discrete time constant spectrum of a very low-stage RC thermal model in the form of Foster ladder. The derived RC model demonstrates a high agreement with experimental data. The comparison is done on a set of devices mounted on a test vehicle.Further, the network identification procedure is conducted on the detailed numerical model of each device for calibration prospect. That calibration procedure of unidirectional responses permits to fix model discrepancies with the aim of creating relevant Boundary-Condition-Independent multipath RC networks.
{"title":"Application of Stochastic Deconvolution Methods to improve the Identification of Complex BCI Multi-port Thermal RC Networks","authors":"V. Bissuel, E. Monier-Vinard, Quentin Dupuis, O. Daniel, N. Laraqi, J. Bauzin","doi":"10.1109/ITherm45881.2020.9190341","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190341","url":null,"abstract":"The thermal modeling of electronic components is more and more crucial to prevent ageing phenomena when the component temperatures exceed their operating limits.At board level, the analysis of their mutual thermal interactions is done using multi-port RC networks as thermal models. Those compact models are usually extracted from a full physical representation of the component and its thermal behavior for a set of boundary conditions. Unfortunately, that fine description of the device requires a set of information about the package that is often not available.To complete the missing thermal properties, transient measurements of the junction-to-case behavior proved to be very useful. Using step function responses, a set of network identification by deconvolution of RC thermal model was conducted using iterative methods such as Bayesian ones.As a main result, a practical procedure is proposed that allows a direct extraction from discrete time constant spectrum of a very low-stage RC thermal model in the form of Foster ladder. The derived RC model demonstrates a high agreement with experimental data. The comparison is done on a set of devices mounted on a test vehicle.Further, the network identification procedure is conducted on the detailed numerical model of each device for calibration prospect. That calibration procedure of unidirectional responses permits to fix model discrepancies with the aim of creating relevant Boundary-Condition-Independent multipath RC networks.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114842974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190945
J. Yoo, Yunhyeok Im, Heeseok Lee, Youngsang Cho, Taekeun An, Hoi-Jin Lee, Youngmin Shin
Recently, the power density has been increasing due to the high bandwidth of 5G mobile devices and it leads to temperature rise. Increased temperature reduces lifetime by quality deterioration and degrade performance with thermal throttling. Therefore, thermal design is more important to increase lifetime and performance in limited environment. Typically, thermal analysis is conducted one by one for concerning parameter, but it cannot give us insight systematically because sensitive analysis for single parameter is not enough to get globally optimal solution.In this paper, we present transient thermal sensitivity approach (TTSA) to see the effect of design parameter on total thermal resistance for packages synthetically. As an example, Single Chip Package (SCP) and Package on Package (POP) is used, and chip thickness, thermal conductivity of Epoxy Modeling Compound (EMC) and Thermal Interface Material (TIM) was varied as a design parameter. Our simulation results show that chip level thermal solution is dominant for both POP and SCP. In case of SCP, package and set level thermal solution is effective when operating time is long enough for heat to arrive at package and set structure. With TTSA, package thermal designer can obtain the direction of package design directly.
{"title":"Impact of Chip, Package, and Set Design on Transient Temperature in Mobile Application","authors":"J. Yoo, Yunhyeok Im, Heeseok Lee, Youngsang Cho, Taekeun An, Hoi-Jin Lee, Youngmin Shin","doi":"10.1109/ITherm45881.2020.9190945","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190945","url":null,"abstract":"Recently, the power density has been increasing due to the high bandwidth of 5G mobile devices and it leads to temperature rise. Increased temperature reduces lifetime by quality deterioration and degrade performance with thermal throttling. Therefore, thermal design is more important to increase lifetime and performance in limited environment. Typically, thermal analysis is conducted one by one for concerning parameter, but it cannot give us insight systematically because sensitive analysis for single parameter is not enough to get globally optimal solution.In this paper, we present transient thermal sensitivity approach (TTSA) to see the effect of design parameter on total thermal resistance for packages synthetically. As an example, Single Chip Package (SCP) and Package on Package (POP) is used, and chip thickness, thermal conductivity of Epoxy Modeling Compound (EMC) and Thermal Interface Material (TIM) was varied as a design parameter. Our simulation results show that chip level thermal solution is dominant for both POP and SCP. In case of SCP, package and set level thermal solution is effective when operating time is long enough for heat to arrive at package and set structure. With TTSA, package thermal designer can obtain the direction of package design directly.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127773448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190947
Chung-Kuei Wang, Mei-Ling Wu
The major problem with quad flat no-lead package (QFN) packages is the delamination between the copper lead-frame and the molding compound (MC) due to relatively weak adhesion. The copper lead frame has excellent electrical and thermal conductivity. However, moisture penetration not only reduces the adhesion between the interfaces of the two materials, but also adversely affects the conductivity of Cu. Interface stratification is attributed to different material properties such as mismatch of coefficient of moisture expansion (CME), surface treatment of the mold pad, thermal strain, vapor pressure at high temperatures, and reduced interface strength due to moisture and temperature effects.The work presented in this paper focused on moisture, thermal and vapor pressure effects on the lead-frame and molding compound in the QFN during the precondition test and reflow process. The causes of delamination were examined both experimentally and via simulations. In an electronic package, the main failure effect stems from molding compound. To accurately simulate the moisture distribution in QFN, in this work, the moisture mechanism pertaining to material properties was investigated. This investigation focused on the MC and epoxy coefficient of moisture expansion and vapor pressure, and the parameters obtained by experimental study were incorporated into a simulation model to verify the fit between the experimental and the simulation findings. The electronic components employed in this work are standard for moisture sensitive testing, according to JEDEC J-STD-020D. To measure the specimen weight gain and geometric size, electronic balance and microscope were used, and these values were obtained under moisture sensitive level 1, level 2 and level 3 in order to establish the moisture desorption rate of the QFN package. And also according to the different degree of oxidation on the leadframe, the surface analysis of the material is carried out by environmental scanning electron microscope (ESEM) to understand the element distribution and interfacial strength. In addition, finite element analysis (FEA) was performed to analyze the stress, warpage and delamination in QFN packages. In this research will discuss the coupling forces of moisture, thermal stress and vapor pressure under MSL-3 and Reflow, and discuss the interface strength under different reliability test stages. To verify the accuracy of simulation modeling, the delamination site was observed and was aligned with the simulation results by applying scan acoustic tomography (SAT). Finally, the reliability of QFN was enhanced by investigating the moisture behavior of the materials co mprising the QFN.
{"title":"Simulation and Analysis of Quad Flat No-lead Package (QFN) under Moisture, and Thermal Stress","authors":"Chung-Kuei Wang, Mei-Ling Wu","doi":"10.1109/ITherm45881.2020.9190947","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190947","url":null,"abstract":"The major problem with quad flat no-lead package (QFN) packages is the delamination between the copper lead-frame and the molding compound (MC) due to relatively weak adhesion. The copper lead frame has excellent electrical and thermal conductivity. However, moisture penetration not only reduces the adhesion between the interfaces of the two materials, but also adversely affects the conductivity of Cu. Interface stratification is attributed to different material properties such as mismatch of coefficient of moisture expansion (CME), surface treatment of the mold pad, thermal strain, vapor pressure at high temperatures, and reduced interface strength due to moisture and temperature effects.The work presented in this paper focused on moisture, thermal and vapor pressure effects on the lead-frame and molding compound in the QFN during the precondition test and reflow process. The causes of delamination were examined both experimentally and via simulations. In an electronic package, the main failure effect stems from molding compound. To accurately simulate the moisture distribution in QFN, in this work, the moisture mechanism pertaining to material properties was investigated. This investigation focused on the MC and epoxy coefficient of moisture expansion and vapor pressure, and the parameters obtained by experimental study were incorporated into a simulation model to verify the fit between the experimental and the simulation findings. The electronic components employed in this work are standard for moisture sensitive testing, according to JEDEC J-STD-020D. To measure the specimen weight gain and geometric size, electronic balance and microscope were used, and these values were obtained under moisture sensitive level 1, level 2 and level 3 in order to establish the moisture desorption rate of the QFN package. And also according to the different degree of oxidation on the leadframe, the surface analysis of the material is carried out by environmental scanning electron microscope (ESEM) to understand the element distribution and interfacial strength. In addition, finite element analysis (FEA) was performed to analyze the stress, warpage and delamination in QFN packages. In this research will discuss the coupling forces of moisture, thermal stress and vapor pressure under MSL-3 and Reflow, and discuss the interface strength under different reliability test stages. To verify the accuracy of simulation modeling, the delamination site was observed and was aligned with the simulation results by applying scan acoustic tomography (SAT). Finally, the reliability of QFN was enhanced by investigating the moisture behavior of the materials co mprising the QFN.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"371 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115967189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190295
Qingbao Ren, Huiyu Yu, Yuanyang Liu, Zhenyu Wang
As an appropriate cooling solution for high heat flux device, the micro pin fin architecture can significantly enhance the fluidic uniformity and the nucleate boiling occurring inside the flow boiling cold plate. In this paper, three types balanced shunt micro pin fins (triangular, hexagonal, and circular) cold plates were fabricated by silicon processes. The fluidic spreading and the boiling states (bubble flow, slug flow, and annular flow) inside the Si-Glass cold plates could be distinguishably observed through the high-speed camera. The relationship between the local two-phase heat transfer coefficient inside the cold plate and the phenomenon of bubble states was investigated. As the results, the cusp regions of the triangular micro pin fins could promote the flow and mixing of the coolant to eliminate the slug flow. The triangular micro pin fins cold plate therefore had the best heat transfer characteristics and pressure drop performance. In addition, the Si-Si cold plate (40 mm 40 mm 1.3 mm) could satisfy 500 W total heat dissipation under 1000 W/cm2 local (4 25 mm2) heat flux density. The heat transfer coefficient of Si-Si cold plate was approximately 1.3 times higher than Si-Glass one.
{"title":"The Investigation of the Silicon Fabricated Balanced Shunt Micro Pin Fins Cold Plate for High Heat Flux Devices","authors":"Qingbao Ren, Huiyu Yu, Yuanyang Liu, Zhenyu Wang","doi":"10.1109/ITherm45881.2020.9190295","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190295","url":null,"abstract":"As an appropriate cooling solution for high heat flux device, the micro pin fin architecture can significantly enhance the fluidic uniformity and the nucleate boiling occurring inside the flow boiling cold plate. In this paper, three types balanced shunt micro pin fins (triangular, hexagonal, and circular) cold plates were fabricated by silicon processes. The fluidic spreading and the boiling states (bubble flow, slug flow, and annular flow) inside the Si-Glass cold plates could be distinguishably observed through the high-speed camera. The relationship between the local two-phase heat transfer coefficient inside the cold plate and the phenomenon of bubble states was investigated. As the results, the cusp regions of the triangular micro pin fins could promote the flow and mixing of the coolant to eliminate the slug flow. The triangular micro pin fins cold plate therefore had the best heat transfer characteristics and pressure drop performance. In addition, the Si-Si cold plate (40 mm 40 mm 1.3 mm) could satisfy 500 W total heat dissipation under 1000 W/cm2 local (4 25 mm2) heat flux density. The heat transfer coefficient of Si-Si cold plate was approximately 1.3 times higher than Si-Glass one.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134117536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190606
A. Bain, Ethan Languri, J. Davidson, D. Kerns, L. Costa
Dielectric oils serve as the primary means of cooling in electric power utility operations. However, beyond the recent advancements in improving the electrically insulating properties, relatively little has been done to optimize the thermal properties of these fluids for their application. Nanoparticle-based fluid suspensions show interesting potential for innovation in enhancing the cooling abilities of dielectric oils. In this study, the convective heat transfer capabilities of a dielectric transformer oil modified with functionalized nanodiamond were studied in a horizontal tube heat exchanger. The behavior was studied in the laminar flow regime. The pressure drop along the same heated test section was also measured. The thermophysical properties of the fluid, such as thermal conductivity, viscosity, and specific heat capacity were studied extensively as a function of the temperature so that their contribution to the enhancement of the effective heat transfer coefficient could be accounted for. The expected values for the Nusselt number as a function of the Reynolds and Prandtl numbers are reported in comparison to the experimental results. Any anomalous convective heat transfer performance beyond the expected could point to other mechanisms in the enhancement process, such as kinematic modification of the flow field due to the presence of nanoparticles, which can direct the efforts of future studies.
{"title":"Experimental Evaluation of Dielectric Oil Functionalized Nanodiamond Suspension Under Laminar Flow Regime","authors":"A. Bain, Ethan Languri, J. Davidson, D. Kerns, L. Costa","doi":"10.1109/ITherm45881.2020.9190606","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190606","url":null,"abstract":"Dielectric oils serve as the primary means of cooling in electric power utility operations. However, beyond the recent advancements in improving the electrically insulating properties, relatively little has been done to optimize the thermal properties of these fluids for their application. Nanoparticle-based fluid suspensions show interesting potential for innovation in enhancing the cooling abilities of dielectric oils. In this study, the convective heat transfer capabilities of a dielectric transformer oil modified with functionalized nanodiamond were studied in a horizontal tube heat exchanger. The behavior was studied in the laminar flow regime. The pressure drop along the same heated test section was also measured. The thermophysical properties of the fluid, such as thermal conductivity, viscosity, and specific heat capacity were studied extensively as a function of the temperature so that their contribution to the enhancement of the effective heat transfer coefficient could be accounted for. The expected values for the Nusselt number as a function of the Reynolds and Prandtl numbers are reported in comparison to the experimental results. Any anomalous convective heat transfer performance beyond the expected could point to other mechanisms in the enhancement process, such as kinematic modification of the flow field due to the presence of nanoparticles, which can direct the efforts of future studies.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"280 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134376947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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