Okafor P.U et al. Int. Journal of Engineering Research and Application www.ijera.com ISSN : 2248-9622, Vol. 3, Issue 5, Sep-Oct 2013, pp.818-829 www.ijera.com 818 | Page Investigation of Printing Performance of Solder Paste at Different Temperatures Okafor P.U and Eneh I.I Department of Electrical/Electronic Engineering Enugu State University of Science and Technology Nigeria Abstract The properties of solder paste are immensely affected by temperature variations and humidity. Apparently, temperature plays a vital role in achieving reliability in print performance and good quality. The printing performance of the solder paste at different temperatures was investigated using two types of lead-free solder paste. Three temperatures were investigated under three different time intervals. Issues to be considered are the solder paste deposit defects associated with the pre-printing temperatures. Keywords: Surface Mount Technology, Printed Circuit Board Assembly, Slump test, Reflow Soldering, Solder Paste. I. Introduction As the trend toward miniaturization and compact product continues, the assembling process of the electronic component or surface mount devices (SMDs) becomes more complex and there is a need for some form of automation (Lau et al. 1996). The automated process of assembling the electronic component or surface mount devices is known as Surface Mount Technology (SMT) by means of using solder paste as interconnecting material to provide electrical, thermal and mechanical function (Huang et al, 2002, and Nguty et al, 2001). Majority of the components used on a printed circuit board assembly (PCBA) are based on surface mount technology (SMT) being assembled using solder paste printing (SPP) and then fixed by the reflow soldering (RS) process (Lau and Yeung 1996). There are three major challenges in the fine pitch stencil printing process. These challenges are the solder paste formulation, the stencil manufacturing process and the optimisation of the process parameters in stencil printing Stencil printing account for a great percentage of defects in surface mount technology. A major course of these defects is the solder paste behaviour during stencil printing, which is greatly affected by temperature. As a result, it is necessary to carry out an intensive study on the effects of temperature on solder paste with respect to its printing performance (Durairaj et al, 2002). II. Experimental design 2.1 Test materials Two commercially available lead-free solder pastes P1 (LF318) and P2 (LF328) prepared from fluxes F1 and F2 were used. The solder particles for all the paste samples are made of the same tin-silver- copper alloy with a melting point of 217˚C. Both P1 and P2 have a percentage metal loading of 88.5%. P1 is a Type 3 solder paste and P2 is Type 4. The flux medium makes up for 11.5% of the solder paste weight. The flux medium contains a stable resin system and slow evaporating solvents with minimal odour. The formulation meets the requirements of the Telcordia (formerly known as Bellcore) GR-78-CORE and ANSI/J-STD-004 for a type ROL0 classification. The two lead-free solder pastes LF318 and LF328 used in this experiment were separated into nine different jars respectively, making it eighteen jars in a whole. Each jar contained one hundred grams of lead-free solder paste. This separation was to allow for the number of experiments that was carried out in the study. For quick and easy identification, LF318 was named P1 and LF328 was named P2. The temperatures under investigation were 15˚C, 25˚C, and 35˚C. As shown in table 1 below, two solder pastes P1 and P2 were stored at each of these temperatures for 24hours, 48hours, and 72hours respectively, making it nine experiments for each solder paste. Table 1: Storage parameters for P1 and P2 at the thermal chamber. Solder paste Temperature (˚C) Storage time (minutes) Storage time (minutes) Storage time (minutes) P1 15(˚C) 1440 2880 4320 P2 15(˚C) 1440 2880 4320 P1 25(˚C) 1440 2880 4320 P2 25(˚C) 1440 2880 4320 P1 35(˚C) 1440 2880 4320 P2 35(˚C) 1440 2880 4320 III. Process parameters The printing parameters used for the experiment are outlined in table 2. Previous work reported by Marks et al (2007) was used as a benchmark. RESEARCH ARTICLE OPEN ACCESS