Influence of Flux and Related Factors on Intermetallic Layer Growth within SAC305 Solder Joints.

Flux contained in solder paste significantly affects the process of solder joint creation during reflow soldering, including the creation of an intermetallic layer (IML). This work investigates the dependence of intermetallic layer thickness on ROL0/ROL1 flux classification, glossy or matt solder mask, and OSP/HASL/ENIG soldering pad surface finish. Two original SAC305 solder pastes differing only in the used flux were chosen for the experiment. The influence of multiple reflows was also observed. The intermetallic layer thicknesses were obtained by the image analysis of micro-section images. The flux type proved to have a significant impact on the intermetallic layer thickness. The solder paste with ROL1 caused an increase in IML thickness by up to 40% in comparison to an identical paste with ROL0 flux. Furthermore, doubling the roughness of the solder mask has increased the resulting IML thickness by 37% at HASL surface finish and by an average of 22%.

Improving the Electrical Contact Performance for Amorphous Wire Magnetic Sensor by Employing MEMS Process.

This paper presents a novel fabrication method for amorphous alloy wire giant magneto-impedance (GMI) magnetic sensor based on micro electro mechanical systems (MEMS) technology. In this process, negative SU-8 thick photoresist was proposed as the solder mask due to its excellent properties, such as good stability, mechanical properties, etc. The low melting temperature solder paste was used for the electrical connections with the amorphous alloy wire and the electrode pads. Compared with the conventional welding fabrication methods, the proposed micro electro mechanical systems (MEMS) process in this paper showed the advantages of good impedance consistency, and can be fabricated at a low temperature of 150 °C. The amorphous alloy wire magnetic sensor made by the conventional method and by the micro electro mechanical systems (MEMS) process were tested and compared, respectively. The minimum resistance value of the magnetic sensor made by the conventional welding method is 19.8 Ω and the maximum is 28.1 Ω. The variance of the resistance is 7.559 Ω². The minimum resistance value of the magnetic sensor made by micro electro mechanical systems (MEMS) process is 20.1 Ω and the maximum is 20.5 Ω. The variance of the resistance is 0.029 Ω². The test results show that the impedance consistency by micro electro mechanical systems (MEMS) process is better than that of the conventional method. The sensor sensitivity is around 150 mV/Oe and the nonlinearity is less than 0.92% F.S.

Determination of Elemental Content in Solder Mask Samples Used in Printed Circuit Boards Using Different Spectroanalytical Techniques.

Solder masks are essential materials used in the manufacture of printed circuit boards (PCB). This material protects PCBs against several types of damage and performance failure. In this study, the capabilities of laser-induced breakdown spectroscopy (LIBS) were investigated for the direct analysis of solder masks typically commercialized for homemade PCB production, and inductively coupled plasma-optical emission spectrometry (ICP-OES) was used to obtain a chemical profile for the target analytes Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Sb, Sn, and Zn. Inductively coupled plasma-mass spectrometry (ICP-MS) was also employed for the determination of potentially toxic elements, such as As, Cd, Cr, Pb, and Hg. In addition to the qualitative information that may be useful for obtaining the spectral profile related to the raw materials present in solder masks formulations, LIBS was also applied for major elements (Al, Ba, Cu, Fe, Mg, and Zn) determination, but due to the low sensitivity, the obtained results were only semi-quantitative for Ba. Regarding Cd, Cr, Hg, and Pb, the samples analyzed were following the restriction of hazardous substances (RoHS) directive of the European Union.