SZFitech

 Void is the presence of air bubble in a solder joint, which affects the mechanical strength, thermal conductivity and electrical properties of the solder joint. Under the same PCB and device conditions, some soldering materials are prone to void formation, while some solder pastes exhibit excellent properties for controlling solder joint void. Flux changes during the soldering process is a very complex process involving a variety of physical and chemical changes, the flux formula determines the soldering effect and characteristics. During the welding process, the flux removes metal oxides from the weld end surface to generate water and gasification to form void; the organic acids in the flux esterify to generate water and gasification to form void; and the organic matter in the flux cracks to form void. Basic reaction principle (a) welding process flux to remove the weld end face metal oxide layer, generating metal salts and water. 2RCOOH+SnO=(RCOO)2Sn+H2O↑ 2HBr+CuO=CuB...

 Wave soldering, sometimes found at the top of the components and pins or solder joints with icicle or stalactite-like solder, this phenomenon is called pull tip, as shown in Figure. Pull-tip occurs mainly at the end of the copper-clad circuit of a PCB. This can be caused if the liquid solder on the PCB is obstructed from falling when the PCB passes through a wave. In high-voltage and high-frequency circuits, this defect can be very harmful and requires special attention. Causes of pull-tip formation Poor solderability of the substrate, oxides or contaminants on the pads; The quality, dosage or application method of the flux is not suitable to wet the surface of the solder joint and remove oxides; The preheating temperature is too low or the preheating time is too short, making the component pins or printed boards absorb too much heat, affecting the fluidity and wettability of the solder; Low solder purity and excessive impurity content; Clamping speed is not suitable, th...

  With the BGA, CSP package devices to dense pitch, miniaturisation of the direction of development, the widespread application of lead-free processes to the electronic assembly process has brought new challenges. Pillow-head effect are BGA, CSP device reflow soldering is unique to a defective form. As shown in the figure, the solder ball and the solder between the solder is not completely fused, but like a pillow on a nest or a pile. This defect often occurs in the reflow soldering of BGA and CSP devices, and is more obvious in lead-free processes.   Figure 1. Pillow head effect. Pillow-head effect is not easily detected because there is often a partial connection between the solder ball and the solder. So the circuit may be able to pass functional testing, optical inspection and ICT testing. However, since the solder is not really fused and mixed with each other, the solder joints are not strong and may lead to failures in subsequent processes or in use. For example, af...

  The Immersion Deposition Tin process is a plating-free process for depositing tin on copper surfaces. It works by using copper and tin in an acid solution where the active tin is higher than copper, so that the pad copper foil reacts with the tin ions in the sink and the tin is oxidised and a uniform layer of tin is formed.   Displacement reaction equation for the Immersion Deposition Tin process   Cu（s）+ Sn2+（aq）→ Cu2+（aq）+ Sn（s） Where Cu stands for copper, Sn for tin, s for solid and aq for aqueous solution. In the reaction, the ions of copper are replaced by those of tin, forming a solid layer of tin.   Comparison with tin spraying (hot air levelling) process: The spray tin process involves spraying molten tin powder onto the surface of the substrate through a high pressure nozzle. The thickness and uniformity of the tin layer is not as good as the sink tin process and therefore may be less suitable for applications where high solder reliability is required...

  Flux is an indispensable substance in the soldering process, its role is to remove the oxides of the soldered parts, increase the wettability of the soldered joints, and improve the quality and reliability of soldering. Flux is divided into organic flux and inorganic flux, according to whether the need to clean, can be divided into washable flux and no-clean flux. Figure 1. Mechanism of flux action No-clean flux is a special type of flux that is characterized by the fact that it does not need to be cleaned with water or solvent after soldering and can be left directly on the circuit board. The advantage of no-clean flux is that it saves the time and cost of cleaning, reduces environmental pollution and improves productivity. So, is it necessary to clean no-clean flux? The answer is: it depends. Although the residue of no-clean flux has a low impact on the performance of the board, it does not mean that it is completely harmless. Residues of no-clean flux still contain a certain a...

  Applying ultrasonic treatment during the soldering process is a novel auxiliary method. By analyzing the morphology of the solder joint after soldering, it can be found that the application of ultrasonic assistance can affect the morphology of the intermetallic compound (IMC) layer at the interface of the solder joint, and the changes in IMC will have different effects on the mechanical properties of the solder joint. 1. Ultrasonic-assisted soldering experiment 1.1 Materials Hu et al. used 10mm×50mm×2mm pure copper sheet and 10mm×10 mm×2mm pure copper sheet for the test. The sample was placed in a steel mold and subjected to ultrasonic treatment using an ultrasonic probe. To ensure a constant time for ultrasonic energy to propagate into the solder, the distance between the ultrasonic probe of each sample and the solder was the same. Therefore, the ultrasonic probe was fixed above the mold positioning groove. Figure 1. Ultrasonic treatment of samples.     1.2 Soldering p...