Investigation of thermal conductivity of PCB (original) (raw)
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INVESTIGATION OF THE EFFECTIVE THERMAL CONDUCTIVITY OF PCB
The investigation deals with the numerical solution of the 3D heat conduction equatioin and study variation of the effective conductivity of PCB with different component size. Cases with and without a copper layer on the component side and different PCB thicknesses were investigated. It was shown that the effective thermal conductivity of a PCB with/without a copper layer on the component side would be larger/smaller than the values given by the onedimensional effective thermal conductivity model if the components mounted on the PCB were smaller than the PCB itself. The difference was more pronounced for smaller components. Correlations were obtained for the effective thermal conductivity of PCBs.
Evaluation of Effective Thermal Conductivity in PCB
PCB is made of composite materials. PCB consists of a sheet of insulating material, small holes are provided on this sheet for accommodating different components of the circuit to be assembled. A piece of base material on which components are mounted, an insulating material along with the bonding material covered with copper foil gives copper cladded laminates. A laminates is essentially a stack of lamina oriented in different directions, the term layup refers to the composition of laminate. Thermal analyzer are usually posed with the job of predicting the temperatures along and across the plane of PCB(thickness) to understand better effect of thermal gradients and stagnation of heat. The main requirement here is to determine the effective orthotropic physical properties of a copper cladded laminate (PCBs). The use of the " effective " implies properties of the entire laminate i.e. to evaluate effective thermal conductivity, density and specific heat of PCBs, but the in this paper its discussed only to evaluate the effective thermal conductivity.
A modeling methodology for thermal analysis of the PCB structure
Microelectronics Journal
Thermal analysis of the PCB structure Analytical solution FVM Numerical solution Analysis of multi-terminal tracks Joule heating and heat spreading in tracks Thermal conduction through vias a b s t r a c t A modeling methodology is proposed for the thermal analysis of the PCB structure based on integrating both the FVM-based numerical solution and the Fourier-series-based analytical solution of temperature. The heat spreading through tracks and the vertical heat transfer through vias are taken into account in a numerical way and regarded as the additional thermal boundary conditions of insulating layers, which are assumed to be homogeneous from an analytical point of view. A methodology based on the vertex-centered Cartesian-grid Finite Volume Method is also proposed for the electric analysis of PCB tracks in order to take into account the temperature-dependent Joule heating effect, thus the current carrying capacity of tracks can be estimated as well. The necessary and sufficient condition for solving electric distributions in multi-terminal tracks is discussed, described and verified through both the analysis of the equivalent resistor network in a multiterminal track and the mathematical analysis of a matrix equation, which correlates terminal currents with terminal electric potentials. In addition, the method for analyzing the multilayer structure is also discussed. A thermal solver was developed in MATLAB based on the methodology. Several layouts were modeled in the solver and COMSOL to test the validity of the methodology and to investigate the influence factors of the solution. Based on the analysis and comparisons, mesh density and the number of eigenvalues are the main influence factors. The vertical and horizontal heat transfer contributions of vias were also investigated by modeling the footprint layout of a power mosfet in order to test the modeling assumptions. Finally, the consistency between the modeling results and the reference results was found. Both the advantages and disadvantages of the methodology are discussed throughout the analysis.
Experimental characterization of board conduction sheets
[1993 Proceedings] Ninth Annual IEEE Semiconductor Thermal Measurement and Management Symposium
A series of experiments is described in which the impact of circuit board thermal conductivity on the thermal performance of air-cooled electronic component arrays is assessed. In the tests, simulated low profile, surface mount components in the form of small copper pieces with heat dissipating thick film resistors are employed. From 1 to 5 of these components are mounted in stan-square pitch arrays onto rhree different circuit board samplesstandard glass epoxy (k=0.26 W/m°K), three-layer (metal-glass epoxy-metal) board of moderate effective conductivity (k=1.14 W/m°K) and a three-layer high conductivity sample (k=35.9 W/m°K). These configurations were tested under both forced and ~hlral convection conditions. Profiles of board temperature were acquired using simultaneous thermocouple measurements. The data are analyzed to ascertain the sensitivity of maximum board and component temperatures as well as the relative importance of the various heat transfer paths as a function of board conductivity. The data extremes show that while convection accounts for approximately 80% of the component heat removal in forced air-cooling on the glass epoxy board, conduction to the board can carry nearly all (96%) of the heat load in natural convection cooling on a highly metalized board. The data are used to develop a composite measure of component thermal footprint as a function of cooling mode and board conductivity. These resdts show that the use of moderate conductivity boards increases the effective heat transfer area of a component by a factor of 3 or more. The utility of linear superposition in this "conjugate" heat transfer application is also discussed. NOMENCLATURE A,exposed area of a component (top and four sides) bffdimensionless measure of effective thermal footprint Ceffeffective thermal conductivity of a multi-layer board DIPdual in-line package Gr-Grashof Number (component length as reference) hocomponent convective heat transfer coefficient without kthermal conductivity Qcondheat dissipation rate due to component to board Qconvheat dissipation rate due to convective cooling of Qradheat dissipation rate due to radiative transfer from board conduction conduction component surface component 0-7003-0863-8l93/53.00 01993 IEEE 127 Kaveh Azar AT&T Bell Laboratories North Andover, M A 01845 1600 osgood Street Qtotaltotal component heat dissipation Re-Reynolds Number (component length as length scale) SOTsmall outline transistor Tccomponent temperature Tc,estestimate of component temperature using &ff Tcentercomponent temperature measured at thick film Tedge,icomponent temperature measured on copper T,enclosure ambient (mixed mean) resistor surface near edge i
Thermal Characterisation of Insulating Layers in Metal Core PCB
2021
This paper provides a steady-state thermal characterisation of advanced insulating layers for isotropic electroconductive adhesive based Metal Core Printed Circuit Boards. Thermal measurements were conducted using the Thermal Transient Tester to analyse the properties of layers applied onto two different base materials-aluminium and copper. For each base material, four types of insulating layers were characterised. Size of the specimen plate for both base materials was selected as 100mm x 20mm x 1mm. The isotropic electroconductive adhesive was applied onto insulating layers to ensure electrical connection between seven SMD heat-generating components. These components are mounted in the identical distance to each other. The thermal characterisation of power SMD components and the assembling process based on isotropic electroconductive adhesive were evaluated. Application of advanced insulating layer was analysed to assess the thermal performance of complete MCPCB structure. It has been shown that the lowest thermal resistance of the aluminium based insulating layers is 21.1K/W, whereas the lowest thermal resistance of the copper based insulating layer is 15.5K/W.
Sensitivity of embedded component temperature to PCB structure and heat transfer coefficient
IEE Proceedings - Circuits, Devices and Systems, 2003
The sensitivity of embedded component temperature to the location of an embedded copper ground plane is investigated using computer simulation. The results show that the presence of a copper ground plane in close proximity to a component layer improves the potential packing density of components within the layer. Furthermore, placing a copper ground plane between two signal layers can reduce thennal interaction between components in the two layers by a factor of up IO. The layer density within a multilayer PCB is therefore improved, which again leads to a higher packing density of components. Using the results generated by the simulation, the authors then proceed to investigate the sensitivity of embedded resistor temperature to resistor size under different conditions of surface heat transfer. The results show that large embedded resistors are more sensitive to surface heat transfer than smaller ones and that small components are more effectively cooled by placing embedded copper ground planes in close proximity to them.
The Influence of Pad Thermal Diffusivity over Heat Transfer into the PCBs Structure
World Academy of Science, Engineering and Technology, International Journal of Electrical, Computer, Energetic, Electronic and Communication Engineering, 2013
The Pads have unique values of thermophysical properties (THP) having important contribution over heat transfer into the PCB structure. Materials with high thermal diffusivity (TD) rapidly adjust their temperature to that of their surroundings, because the HT is quick in compare to their volumetric heat capacity (VHC). In the paper is presenting the diffusivity tests (ASTM E1461 flash method) for PCBs with different core materials. In the experiments, the multilayer structure of PCBA was taken into consideration, an equivalent property referring to each of experimental structure be practically measured. Concerning to entire structure, the THP emphasize the major contribution of substrate in establishing of reflow soldering process (RSP) heat transfer necessities. This conclusion offer practical solution for heat transfer time constant calculation as function of thickness and substrate material diffusivity with an acceptable error estimation. Keywords—heat transfer time constant, pac...
20th International Workshop on Thermal Investigations of ICs and Systems, 2014
Electronic components are continuously getting smaller. They embed more and more powered functions which exacerbate the temperature rise in component/board interconnect areas. Their design optimization is henceforth mandatory to control the temperature excess and to preserve component reliability. To allow the electronic designer to early analyze the limits of their power dissipation, an analytical model of a multi-layered electronic board was established with the purpose to assess the validity of conventional board modeling approaches. For decades, a vast majority of authors have been promoting a homogenous single layer model that lumped the layers of the board using effective orthotropic thermal properties. The work presents the thermal behavior comparison between a detailed multi-layer representation and its deducted equivalent lumped model for an extensive set of variable parameters, such as effective thermal conductivities calculation models or source size. The results highlight the fact that the conventional practices for Printed Circuit Board modeling can dramatically underestimate source temperatures when their size is very small.
Transactions of The Japan Institute of Electronics Packaging, 2017
Recently, the thermal design on the circuit board becomes more difficult with the miniaturization and high density of electronic devices. Among them, heat dissipation of small components is a problem. The components, such as power semiconductors that are primarily anticipated to produce much heat, are provided with heat dissipation measures such as dedicated heatsinks. Thus thermal control is relatively easy. With small chip components, such as surface mount type chip resistors (hereinafter referred to chip resistor), heat dissipation measures are often not adequately taken because they are used in large numbers on a circuit and each of them produces only a small amount of heat (a few hundred mW to several W). However, even when the amount of heat is small, there are many cases where pattern design must be reviewed because of unexpected temperature rise during actual circuit operation due to the high density of heat flux from chip components. When using small chip components, the pattern design is important to achieve sufficient heat dissipation because the temperature rise of the component varies greatly with the heat dissipation condition of the surface-mounted pattern. However, the specific guidelines or design rules for that purpose are not always available. Designing the board pattern is part of the work for the circuit and board designers. And the circuit designers who mainly had to deal with electrical design in the past are now required to perform thermal design as well. However, thermal design has been done mainly by mechanical designers, and many circuit designers are not experts in thermal design. For this reason, establishing simpler and clearer method for pattern design is under urgent necessity.
Thermal analysis by electrical resistivity measurement
Journal of thermal analysis and calorimetry, 2001
Thermal analysis in the form of electrical resistivity measurement is reviewed. It is useful for studying phase transitions and electrical conduction mechanisms. The resistivity can be the volume resistivity or the contact resistivity, as illustrated for the case of continuous carbon fiber polymer-matrix composites.