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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

HEAT TRANSFER IN PCB MANUFACTURING

Get access (open in a dialog) DOI: 10.1615/IHTC16.kn.000020
393 pages

要約

The optimal placement of electronic components on a Printed Circuit Board (PCB) requires satisfying multiple conflicting design objectives as most of the components have different power dissipation, operating temperature, types of material and dimension. Also, the margin of solder joints and the pitch dimensions in an electronic component is continuously scaled down as a future trend.
These challenges lead to more complex thermal responses, mostly during the soldering process. Reflow soldering is one of the most widespread soldering technologies used in the electronic industry. It is a method of attaching surface components to a PCB with solder paste. The goal of the reflow process is to melt the solder and heat the adjoining surfaces, without overheating and damaging the electrical components. Improvements in the heat transfer performance require the identification of heat transfer mechanisms within the structure, the design parameters and the models to predict heat transfer performance at the boards.
The three common principles of conduction, convection and radiation all occur in PCB manufacturing processes. The latter two apply directly to surface layers of the board as well as the surface mounted components. The limitations in the heat dissipation depend on the amount of mounted components, their size and their distribution in the PCB. Thus, large heat sources should not be placed in close proximity to sensitive components as they may raise the operating temperature to a critical level; and, when placing several components in a row, natural convection flow can create turbulent wakes and increases heat transfer. The conduction mechanism is mostly affected by the materials, the thickness and the number of layers of the PCB, as well as the characteristics of the surface mounted components.
Computational Fluid Dynamics (CFD) techniques can be used to accurately predict the actual behaviour of the PCB and its components when it moves along the reflow oven. The modelling can extend through all steps of the manufacturing process, from the paste deposition to the meniscus formation during the reflow phase. Models are multi component and multiphase to capture the interface solid-liquid-gas. It is possible to analyse the process variables, eliminating potential thermal aspects that could be responsible to damage the PCB and their components. These tools allow using the simulation process measurements to create a model that can predict the temperature at any point within the domain, analyse the heat dissipation in the PCB and their components over a specific time cycle.