Experimental and numerical investigation of 3D gas flow temperature field in infrared heating reflow oven with circulating fan A.M. Najib a,b , M.Z. Abdullah a , C.Y. Khor a,⇑ , A.A. Saad a a Advance Packaging and SMT Unit, School of Mechanical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia b Advance Mechatronic Laboratory, Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia article info Article history: Received 8 September 2014 Received in revised form 22 March 2015 Accepted 23 March 2015 Available online 10 April 2015 Keywords: Desktop lead-free reflow oven CFD Forced-air convection IR heating abstract This study presents the experimental and numerical analysis of the thermal process for laboratory scale desktop lead-free reflow oven and discusses a 3D CFD model of radiation heating with forced-air convec- tion from circulating stainless steel fan. The experiments were carried out to determine the temperature boundary condition of infrared heating element. In addition, the RPM of the rotating fan was measured using HT50 tachometers. To validate the spatial temperature of the oven, a set of industrial standard thermocouples was employed in various positions. The device was accessed throughout all stages of tem- perature reflow profile. The profile setting of the oven is in accordance to standard JSTD-020D. The desk- top reflow oven was then numerically simulated using the computational model and the advanced user- defined functions (UDFs) were developed to model the thermal profile. The study reveals the temperature distribution of the desktop reflow oven is dependent on the air circulation in the oven at various posi- tions. The temperature contour and air circulation in the oven chamber were demonstrated in the numerical simulation. The experimental and simulation results are useful for further improvement of temperature uniformity within the oven chamber for a convective IR heating reflow oven. The tempera- ture results show a satisfactory agreement with both experiment and simulation. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Reflow oven is widely used in the microelectronics industry to assemble surface mount components (SMCs) and devices (SMDs) onto the printed circuit board (PCB). Prior to the reflow soldering process, the solder paste is printed on the copper pad which cov- ered by surface finishes (e.g. ENIG, Imm Ag, Imm Sn, etc.). Then, the automated placement machine deposits the SMCs on the solder paste. After that, the PCB passes through different zones (i.e., pre- heating, soaking, soldering and cooling) in the reflow oven. Typically, two types of the reflow oven have been used based on the scale and the application. Multiple zones reflow oven is com- monly used in the industry for the mass production of the assem- bly process. On the contrary, the desktop reflow oven is appropriate for low-volume production and research purpose. In general, the PCB inside the desktop reflow oven is static at its loca- tion, whereas the PCB inside the reflow oven with multiple zones is carried by conveyor throughout different stages. The most com- monly used reflow ovens today were forced convection, infrared (IR) and the combination of two [1]. The IR reflow oven can be clas- sified by heating principle of the device. Reflow oven with medium and long wave required additional air convection for temperature field distribution within the oven space. The airflow can circulate either a forced or natural manner. Forced air circulation is usually implemented using a fan or jet impingement system. The air circulation introduced in an infrared oven is to ensure uniform temperature distribution within the space. The characteristics of the reflow oven depend on the oven design (e.g., multiple sections or single chamber), the heating device and airflow control (e.g., fan or jet impingement system). The understandings of the reflow oven are significant to the pro- cess control in the reflow soldering process. Reflow soldering pro- file may influence the microstructure of the solder joint, such as thickness of intermetallic compound (IMC) [2]. High peak reflow temperature and longer time above the liquidus temperature con- tribute to the increase of the IMC layer. The solder joint with a thick layer of IMC is prone to failure during the thermal cycle [3]. Besides, it degrades the mechanical properties and leads to brittle failure mode [4,5]. The homogeneity and efficiency of the reflow oven have the crucial impact on the solder joint reliability. The inhomogeneous temperature distribution in the reflow oven may http://dx.doi.org/10.1016/j.ijheatmasstransfer.2015.03.075 0017-9310/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +60 195637283; fax: +60 4 594 1025. E-mail addresses: cykhor_1985@hotmail.com, mecykhor@usm.my (C.Y. Khor). International Journal of Heat and Mass Transfer 87 (2015) 49–58 Contents lists available at ScienceDirect International Journal of Heat and Mass Transfer journal homepage: www.elsevier.com/locate/ijhmt