The influence of a soldering manner on thermal properties of LED modules

Abstract

Purpose This paper aims to present the results of the influence of a manner of soldering light emitting diodes (LEDs) to the metal core printed circuit board on thermal parameters of the module LED containing these diodes. Design/methodology/approach Using the authors’ elaborated measuring method and the dedicated measurement set-up, transient thermal impedances of LED modules, mounted using different soldering processes and mounted to the heat-sink with different values of the moment of force, are measured. The obtained results of measurements are discussed. Findings It was shown experimentally that the manner of soldering could strongly influence efficiency of dissipation of heat generated in the module. The best thermal properties were obtained for soldering using vapour phase technology with vacuum and paste LFS-216LT. It was also proved that the moment of force used while mounting the considered modules on the heat-sink can result in a change of the value of thermal resistance of this module exceeding even 12 per cent. Research limitations/implications The investigations were performed for five LED modules operating at one, arbitrarily selected value of power dissipated in these modules mounted on the heat-sink of arbitrarily selected dimensions. Practical implications The obtained results of measurements could be usable for designers of mounting processes of power LED modules. Originality/value This paper presents the results of investigations of thermal properties of LED modules, in which different techniques of soldering are used. It was shown experimentally that the manner of soldering could strongly influence efficiency of dissipation of heat generated in the module. It was also proved that the moment of force used while mounting the considered modules on the heat-sink is important.

Modelling thermal properties of large LED modules

“…The obtained results of calculations were compared with the results of measurements. The measurements were carried out by the indirect electrical method described in the authors' previous papers [6,19]. Calculations and measurements were performed for different manners of power dissipation in the module.…”

“…The PCB comprised an aluminum-core base layer, a thin thermally conductive dielectric layer and a copper-circuit layer of thicknesses 1.5 mm, 0.100 and 0.035 mm respectively. The modules were soldered using two different techniques: convection reflow and vapor phase reflow in vacuum [6,7,[24][25][26][27]. Alpha Metals OM340 solder paste of InnLotTM type was used for the LEDs assembly [28].…”

“…Nowadays, large LED modules, whose area exceeds even 100 cm 2 , are also offered. In these modules diodes are situated in parallel to the axis of the LED module [6,7]. LED modules can accept different shapes and they can be situated on the Metal Core Printed Circuit Board (MCPCB) base with different thicknesses of the aluminum-layer.…”

Influence of a Thermal Pad on Selected Parameters of Power LEDs

“…The thermal resistance between the p-n junction of a power LED and the ambient is used to describe the total influence of all components included in the heat flow path, e.g., the package of the device, the printed circuit board (PCB), and the heatsink, on the heat transfer efficiency [4,16]. Thus, the manner of assembly of a power LED can influence its thermal properties and, consequently, electric and optical properties of this device [17,18].…”

“…Additionally, in references [21,22], it is shown that an increase in the semiconductor device internal temperature causes a visible decrease of its lifetime. Besides, the parameters of mounting process [17,23] and the area of soldering pads [14] also influence the device thermal. Manufacturers of power LEDs are continuously improving the quality of packages for these devices, which are characterized by lower and lower values of junction-to-case thermal resistance R thj-c .…”