SZFitech

 I. Core Definition and Unit System of Solder Paste Viscosity Solder paste viscosity is a key indicator of its internal friction, which directly affects printing performance and solder quality.Common units include: Pa-s (Pascal seconds): International System of Units, 1 Pa-s = 1000 mPa-s. kcp (thousand centipoise): the industry commonly used units, 1 kcp = 1000 mPa-s = 1Pa.S, IPC standard 60-140 kcp corresponds to 60-140 Pa-s. cp (centipoise): 1 cp = 10 mPa-s for low viscosity scenarios. Standard range differences: General standard: 150-250 mPa-s (for general printing). IPC Standard: IPC-TM-650 specifies viscosity of 200-300 Pa-s at 25°C. Wide range: 20-300 Pa-s (covers different process requirements). II. the test method and equipment selection Test methods need to be selected according to the accuracy requirements and scenarios: Rotational Viscometer Method (Mainstream) Principle: Calculate viscosity by measuring rotational resistance to simulate printing shear ra...

 Soldering mobile phone motherboards requires the selection of solder paste suitable for high-density, fine solder joints, and the following are key factors and recommendations: 1. Type of solder paste Lead-free solder paste: Comply with environmental regulations (such as RoHS), commonly used alloy SAC305 (tin 96.5% / silver 3% / copper 0.5%), melting point of about 217-219 ℃.Suitable for modern mobile phone motherboards, but note that higher reflow temperatures may affect heat sensitive components. Leaded solder paste: e.g. Sn63/Pb37 (Sn63%/Pb37%), lower melting point (183°C), easier to control the soldering process, but subject to environmental constraints, usually used for non-export products or specific scenarios. 2. Alloy composition SAC series (e.g. SAC305, SAC307): high mechanical strength, good fatigue resistance, suitable for precision packages such as BGA. Bismuth-containing alloys (e.g. Sn42/Bi58): lower melting point (138°C), but more brittle, may be used ...

 The widely used solder paste brands in China include both internationally renowned brands and excellent local manufacturers.The following is a classification of common brands and their characteristics: I. International Brands Senju (Senju Metals, Japan) Known for high reliability and stability, widely used in consumer electronics, communication equipment. Mainly halogen-free, low void rate solder paste, suitable for precision BGA/CSP packaging. Alpha (Alpha, USA) Once the electronic materials division of the UK's Cookson Group, Alpha was later acquired by McDermott and became part of McDermott Alpha, a leading global supplier of soldering materials. Its products cover lead-free and low-temperature solder pastes for high-precision SMT processes and automotive electronics. Indium (Indium-Tech, USA) Focusing on the high-end market, it provides customised solder paste solutions, such as high thermal conductivity and high temperature resistant products. Widely used in...

 As an important metal powder material, tin powder, by virtue of its unique physicochemical properties, shows a wide range of application value in a number of industrial fields.The following is a detailed description from both physical characteristics and application areas: I. Physical Characteristics of Tin Powder Appearance and form Tin powder is usually presented as grey or silver-white powder with metallic luster, soft texture and ductility.It has a variety of particle forms, including spherical, irregular shapes, etc., with a wide range of particle size distribution (e.g., 150μm, 77μm, 45μm, 15μm, 6μm, etc.), and the different particle sizes directly affect its application performance. Physical Properties Melting point and boiling point: The melting point of tin powder is about 231.9°C, and the boiling point is as high as 2270°C to 2507°C, which indicates that it has high thermal stability. Density: The relative density is 7.28 to 7.31, which is a high-densit...

 Detailed analysis of Non Wet Open (NWO) and suggestions for improvement I.the definition and typical characteristics Non Wet Open (NWO) refers to the PCB (Printed Circuit Board), BGA (Ball Grid Array) pads do not achieve a good wet open solder joints.Typical characteristics of its slicing diagram for all or part of the PCB pads on the lack of solder wetting, as shown in Figure 1-1 (not attached here, but a clear description). 图 1-1 无润湿开焊焊点切片图 II. Causes BGA warpage causes solder paste to pull up Formation stage: No wetting open solder joints usually begin to form in the temperature rise stage of reflow soldering (160 ~ 190 ℃). Formation mechanism: As shown in Figure 1-2, BGA warpage occurs, the solder paste will be brought to the BGA solder ball, due to the separation of the solder paste and pads, resulting in the formation of good solder joints. Figure 1-2 Mechanism of non-wetted open solder joint formation Other conditions that lead to open solder joints Sold...