SZFitech

It is well known that the development of electronic technology has put forward higher requirements for solder density and miniaturization of solder joints. As the volume of solder joints decreases, the openings of stencils used for solder paste printing must become smaller. As the size of the steel mesh opening is adjusted, the volume of solder paste on the solder pad will change, resulting in the solder joints evolving into different shapes during the reflow process. Cracks will form between the components and PCB due to the different coefficients of thermal expansion during thermal cycling. However, the fatigue life of solder joints can be improved by optimizing the shape of the solder paste after reflow. Experiment Design In order to understand what solder joint shapes can achieve higher fatigue life of solder joints, Ha et al. used a specific thickness of stencil to print solder paste on resistors R1005 and R0402. By calculating the solder shape corresponding to the s...

 Copper is commonly used as the pad material in the packaging process. To avoid copper oxidation and improve the solderability of copper pads, various surface treatment methods are used to coat metal layers on copper pads. Common surface treatment processes include OSP, electroless nickel immersion gold (ENIG), etc. The ENIG is performed by electroless nickel plating on the copper pads. The nickel-plated pads are then immersed in gold water to achieve gold plating through the displacement reaction. The gold layer can protect the nickel layer from oxidation. The ENIG process has the risk of the black pad. The reason causing the black pad is that the atomic radius of nickel is smaller than that of gold, resulting in rough surface grains after gold plating. The gold plating solution will penetrate the nickel layer where an interfacial reaction occurs and corrode the nickel layer. The corroded nickel atoms will continue to oxidize and generate nickel oxide with poor solde...

 The traditional solder flux is formulated with rosin or epoxy resin as the base material, mixing with an active agent, thixotropic agent, solvent, and other substances. At present, two major factions of no-clean solder paste and water-soluble solder paste have been derived based on flux compositions. No-clean solder paste, as the name suggests, produces a tiny amount of residue after soldering and is unnecessary to clean. Although no-clean solder paste has less activity, it can still meet most consumer electronics soldering needs. Currently, no-clean solder paste is adopted by the majority of companies because of its good stability and simple use process. However, some solders require higher flux activity, and the residue level is unacceptable, which needs to be removed by using cleaning agents. Features of Water-Soluble Solder Paste The water-soluble solder paste is still made by mixing alloy solder powder and flux but using water-soluble flux components. Water-solub...

 PCB surface treatment is to cover the PCB surface with a protective layer to prevent copper oxidation, corrosion and to improve solderability, reliability and aesthetics. there are various PCB surface treatment processes, such as tin spraying, gold sinking, silver sinking, etc., of which OSP is an environmentally friendly process that meets the requirements of the RoHS directive. What is OSP? OSP is the abbreviation for Organic Solderability Preservatives, also known as bare copper, Entek. simply put, OSP is an organic skin film that grows chemically on a clean bare copper surface. This film is resistant to oxidation, thermal shock and humidity and protects the copper surface from further rusting (oxidation or sulphidation etc.) in the normal environment; however, in the subsequent high soldering temperatures, the film must be easily and quickly removed by the flux so that the exposed clean copper surface can be immediately bonded to the molten solder in a very short...

 In the reflow soldering process, for μBGA and CSP packaged chips with dense feet (pitch ≤ 0.5mm), there is a risk of higher incidence of cold soldering due to the hidden nature of the soldering site and the difficulty of heat transfer to the solder ball solder joint site. Under the same peak temperature and reflow time conditions, the heat gained by the μBGA, CSP solder ball solder joints is significantly insufficient compared to other components with good solder joint exposure in hot air. This makes it difficult for the temperature of some μBGA, CSP bottom solder balls to reach the wetting temperature, which leads to the cold soldering problem. Figure 1. CSP (chip-scale packaging) reflow soldering heat transfer pathway Cold soldering is a phenomenon caused by the fact that the minimum required wetting temperature between the solder and the base metal is not reached during soldering, or localised wetting occurs, but the metallurgical reaction is incomplete. Cold solde...

 With the development of semiconductor technology, there is a trend towards miniaturization of electronic devices in electronic packaging, so the reliability of solder joints has become increasingly important. When the size of the solder joint decreases and the soldering temperature increases, the growth rate of interface IMCs is fast. Due to the excessive growth of brittle IMCs, the anti-drop, shear, and thermal cycling performance of solder joints will decrease. Sn42Bi58 solder paste is a eutectic solder paste that can be applied in low-temperature soldering (low thermal shock) environments and can provide good yield strength and creep resistance. Epoxy flux However, due to the tendency of Sn42Bi58 solder paste to accumulate Bi and reduce the reliability of solder joints, it is necessary to adopt a method to improve the strength of solder joints. Li et al. proposed adding curable epoxy resin to the Sn42Bi58 solder paste system to prepare resin-reinforced composite s...

 ENIG (Electroless Nickel Immersion Gold) is a widely used process for PCB surface treatment, also known as immersion gold or electroless nickel gold. The gold layer of ENIG is thinner and less dense than that of electroless gold plated boards. Generally, the thickness of the nickel layer is required to be 3-5 μm, and the thickness of the gold layer is 0.05-0.15 μm (usually controlled in the range of 0.07-0.1 μm). When it is necessary to carry out the soldering process on the surface of the ENIG, it is necessary to increase the thickness of the nickel layer to 4-7 μm. ENIG treatment of the pad surface flat, in the close-pitch device printing and mounting process has a good use of results. The gold layer has good conductivity and wear resistance and can be used directly as a contact surface. In addition, the gold layer also has the ability to resist oxidation and corrosion, and can effectively protect the underlying nickel layer from oxidation, so as to maintain good s...

 The traditional solder flux is formulated with rosin or epoxy resin as the base material, mixing with an active agent, thixotropic agent, solvent, and other substances. At present, two major factions of no-clean solder paste and water-soluble solder paste have been derived based on flux compositions. No-clean solder paste, as the name suggests, produces a tiny amount of residue after soldering and is unnecessary to clean. Although no-clean solder paste has less activity, it can still meet most consumer electronics soldering needs. Currently, no-clean solder paste is adopted by the majority of companies because of its good stability and simple use process. However, some solders require higher flux activity, and the residue level is unacceptable, which needs to be removed by using cleaning agents. Features of Water-Soluble Solder Paste The water-soluble solder paste is still made by mixing alloy solder powder and flux but using water-soluble flux components. Water-solub...

 The flip chip assembly process typically includes soldering, flux residue removal and underfill. As chips continue to miniaturize, the gap between the flip chip and the substrate decreases, making it increasingly difficult to remove flux residue. This inevitably leads to an increase in cleaning costs or affects the efficiency and reliability of underfill. Although no-clean processes using no-clean fluxes are commercially available, compatibility between residues left by no-clean fluxes and underfill chemistries remains a major issue. Poor compatibility typically results in impeded capillary bottom fill flow or bottom fill delamination. Epoxy flux is a new type of flux for flip chip packaging, its main components are resin (epoxy resin, acrylic resin, etc.), organic acid activator, thixotropic agent and solvent. In the reflow soldering process its organic components cured into a layer of epoxy resin glue, attached to the solder joints around, play a role in strengthe...

 After decades of development, surface mount technology (SMT) has become increasingly mature. It is well known that the number and density of components on an electronic device have increased dramatically compared with the past. If manual mounting is still massively used, the efficiency of assembling components on PCBs is slow, and the accuracy is compromised. Therefore, personnel in the industry developed SMT placement machines. The working efficiency of the placement machine is much faster than manual work. One placement machine can complete the assembly of tens of thousands of components per hour. It can be said that SMT placement machines have become essential equipment for SMT manufacturers. Introduction of the SMT placement machines SMT placement machines have always been a hot topic in the industry. From the observation, mainstream manufacturers use the pick-and-place machine and collect-and-place machine. These two types of placement machines are very similar,...

 The application of power device products has expanded to a considerable number of industries, such as automotive, aerospace, and military industries. Power devices need to be able to adapt to higher operating temperatures (>250°C), which significantly increases the demand for equipment materials. Transient liquid phase (TLP) bonding is considered a reliable technique for preparing high-temperature solder joints, which allows soldering at relatively low temperatures while generating higher soldering remelting temperatures. However, TLP bonding takes a long time to completely consume low melting point metals and requires several hours of annealing to form stable solder joints. 1. Micro-sized Cu particles Liu et al. deposited Sn layers on Cu particles. The average diameter of Cu particles is 6.2μm. The average thickness of Sn coating was about 0.5μm. The Cu particles were then made into a paste consisting of 85wt% particles and 15wt% terpene alcohol solvent. The Cu-C...

 Mini LED is a new type of display technology that uses 50-200 micron LED chips as backlight or pixel units, achieving excellent display effects such as high brightness, high contrast and high colour gamut, etc. The chip package process of Mini LED mainly adopts flip-flop package, whereby the LED chip is inverted on a carrier board and solidified and electrically connected by solder paste or solder adhesive. This process not only eliminates the step of gold wire bonding, but also improves the heat dissipation performance and reliability of the chip. Due to the small size of Mini LED chips, the requirements for solder paste solder are higher, including particle size, melting point, wettability, void rate and residue. Currently on the market commonly used Mini LED packaging solder paste solder is mainly divided into two types: medium temperature solder and low temperature solder. Medium temperature solder refers to the melting point between 200-250 degrees Celsius lead...