Welding technology plays an extremely important role in the assembly of electronic products. General welding is divided into two categories: one is mainly applied to the welding of through-hole plug-type electronic components and printed boards - wave soldering, the so-called wave soldering (wavesoldering) is to melt the solder, the electric The pump or electromagnetic pump sprays the solder wave peaks required by the design to allow the printed boards pre-equipped with electronic components to pass through the solder peaks to achieve the mechanical and electrical connection between the component terminals or the leads and the PCB pads. Brazing; the other is mainly used for surface-mount components and printed board reflow soldering (reflowsoldering), also known as reflow soldering, the so-called reflow is re-melted by pre-distribution to the PCB pad The paste solder on the solder paste realizes the soldering of the surface-mount components or the mechanical and electrical connection between the leads and the printed circuit board pad, thereby realizing the circuit function with certain reliability. With the large-scale use of surface mount components in electronic products, reflow soldering technology has become a major process technology in surface mount technology. Its main process features are: the surface of the metal to be welded is cleaned (removed oxide) with a flux to make it have good wettability to the solder; the molten solder is supplied to moisten the metal surface; and the intermetallic compound is formed between the solder and the weld metal In addition, micro-welding can be realized.
Reflow soldering is a group or point-by-point soldering process in which a proper amount and appropriate form of solder are applied to the soldered area (pad) of the PCB in advance, and then the surface mounted components are placed and the solder is reflowed by the external heat source to meet the soldering requirements. Reflow soldering has the following features compared to wave soldering:
1. Reflow does not require the components to be directly immersed in the molten solder as in wave soldering, so the thermal shock to the components is small;
2. Reflow solder is only applied to the desired area, which greatly saves the use of solder.
3, reflow can control the amount of solder to discharge, to avoid bridging and other defects;
4. When the component placement position deviates by a certain amount, due to the surface tension of the molten solder, as long as the solder is applied in the correct position, the reflow soldering can automatically correct this minor deviation during welding, so that the component is fixed in the correct position;
5, can use local heating heat source, which can be on the same substrate with a different reflow soldering process welding;
6. Impurities are generally not mixed in the solder, and the solder composition can be properly maintained when solder paste is used for reflow soldering.
Reflow soldering technology is classified according to heating methods: vapor phase reflow, infrared reflow, infrared hot air reflow, laser reflow, hot air reflow and tool heating reflow.
Reflow principle and temperature curve:
The principle of reflow soldering is analyzed from the temperature curve (see Figure 1): When the PCB enters the elevated temperature zone (drying zone), the solvent and gas in the solder paste evaporate. At the same time, the flux in the solder paste wets the pads and the components. Head and pins, solder paste softened, slumped, covering the pad, the pad, component pins and oxygen isolation; PCB into the insulation area, so that PCB and components are fully warmed up, in case the PCB suddenly Into the welding zone heating up too fast and damage the PCB and components; When the PCB into the welding area, the temperature rises quickly so that the solder paste to a molten state, the liquid solder on the PCB pad, component terminals and pins wetting, diffusion, Diffuse or reflow mixed to form the solder joints; PCB into the cooling area, the solder joints to solidify, complete the entire reflow.
The temperature curve is the key to ensure the welding quality. The temperature rise slope and peak temperature of the actual temperature curve and solder paste temperature curve should be basically the same. The temperature rise rate before 160°C is controlled at 1°C/s to 2°C/s. If the temperature ramp rate is too fast, on the one hand, the components and the PCB are heated too quickly, which can easily damage the components and cause PCB distortion. On the other hand, The solvent in the solder paste evaporates too quickly, which can easily spill metal components and create solder balls. The peak temperature is generally set to be about 20°C to 40°C higher than the melting temperature of the solder paste (for example, Sn63/Pb37 solder paste has a melting point of 183°C and the peak temperature should be set at about 205°C to 230°C), and the reflow time For 10s to 60s, low peak temperature or short (re)flow time will result in insufficient welding. In severe cases, the solder paste will not melt; the peak temperature is too high or the (re)flow time will be longer, resulting in oxidation of the metal powder. Affect the quality of welding, and even damage the components and PCB.
According to the reflow temperature curve and the principle of reflow, the current reflow soldering machine on the market is generally a simple four-zone reflow soldering machine, as well as a large reflow soldering machine in the temperature range of six, eight, or even twelve, and the reflow soldering type QHL320A. The machine adopts 20 sections of programmable temperature control, which is equivalent to a 20-zone reflow soldering machine. This subdivides the reflow temperature curve, and thus the temperature control is more accurate, and the ideal reflow temperature curve is further fitted to achieve perfect welding.
How to ensure a good welding quality? QHL320A reflow soldering machine in addition to control in full compliance with the reflow temperature curve, but also allows users to truly understand the principle of reflow soldering. The QHL320A reflow soldering machine has the function of a large-size transparent window. The user can control the entire welding process through the transparent window. At the same time, the solder paste can be observed during the entire welding process, easily discovering problems in the welding process, through the parameters. Adjustments are improved to ensure good welding quality. At the same time, QHL320A reflow soldering machine is a small desktop reflow soldering machine. It adopts full static welding, which effectively prevents the tiny vibration generated by the crawler type transmission of the large-scale multi-temperature zone reflow soldering machine. This vibration may melt the solder paste in the soldering zone. Under the impact of the tiny pitch IC (such as pitch ≤ 0.5mm) and components (such as 0603, 0402 and 0201, etc.) welding, resulting in component drift, solder beads, solder bridges and other welding defects, and full static welding is completely Avoid the above possible defects.
Set back (re)flow soldering temperature curve basis:
1. Set according to the temperature profile using solder paste. Solder pastes with different metal contents have different temperature profiles. The temperature profile of the specific product should be set according to the temperature profile provided by the solder paste manufacturer.
2, according to the PCB material, thickness, whether the multilayer board, size, etc.;
3ã€According to the density of surface mounting board mounted components, the size of components, and whether there are special components such as BGA, CSP, etc.
4, according to the specific circumstances of the equipment, such as: the length of the heating zone, the heating source material, back (re)flow furnace structure and heat conduction and other factors set.
Hot air reflow soldering machine and infrared reflow soldering machine are very different: infrared reflow soldering machine is mainly radiation conduction, its advantages are high thermal efficiency, high temperature steepness, double-sided soldering PCB easy to control the temperature, its disadvantages Because the temperature is not uniform, the temperature of the device is different due to the color, material, and size of the device on the same PCB. In order to achieve the soldering temperature of the bulk components of the solder joint around the dark color device, the soldering temperature must be increased. Hot air reflow soldering machine is mainly convection conduction, its advantages are uniform temperature, good welding quality; the disadvantage is that the temperature difference between the upper and lower PCB and the temperature gradient along the length direction of the welding furnace is not easy to control.
With the advantages of hot air reflow and infrared reflow soldering and the technology and advantages of large reflow soldering machines, China Aviation Industry Group No. 1 Beijing Qingyun Innovation Technology Development Co., Ltd. has launched the QHL320A-SMT compact combination of infrared heating and forced hot air circulation. Precision bench reflow machine. Combining the company's powerful military aviation technology capabilities, eight years of professional research, development and production process experience, independent research and development and production of small and complete SMT mounting and welding equipment suitable for R&D, small and medium batch production of various types of enterprises and research institutes: SMT small precision tabletop reflow soldering machine series (â—QHL320 classic type â—QHL320A enhanced type â—QHL360 lead-free type), tracked online reflow machine, manual screen printing station, anti-static vacuum suction pen, precision IC placement table, component rack, etc. . Another BGA positioning placement system, semi-automatic placement machine, high-precision silk screen, semi-automatic dispensing machine, temperature tester, electronic insulation box (for the use of solder paste), magnifying glass and other auxiliary equipment.
Reflow soldering is a group or point-by-point soldering process in which a proper amount and appropriate form of solder are applied to the soldered area (pad) of the PCB in advance, and then the surface mounted components are placed and the solder is reflowed by the external heat source to meet the soldering requirements. Reflow soldering has the following features compared to wave soldering:
1. Reflow does not require the components to be directly immersed in the molten solder as in wave soldering, so the thermal shock to the components is small;
2. Reflow solder is only applied to the desired area, which greatly saves the use of solder.
3, reflow can control the amount of solder to discharge, to avoid bridging and other defects;
4. When the component placement position deviates by a certain amount, due to the surface tension of the molten solder, as long as the solder is applied in the correct position, the reflow soldering can automatically correct this minor deviation during welding, so that the component is fixed in the correct position;
5, can use local heating heat source, which can be on the same substrate with a different reflow soldering process welding;
6. Impurities are generally not mixed in the solder, and the solder composition can be properly maintained when solder paste is used for reflow soldering.
Reflow soldering technology is classified according to heating methods: vapor phase reflow, infrared reflow, infrared hot air reflow, laser reflow, hot air reflow and tool heating reflow.
Reflow principle and temperature curve:
The principle of reflow soldering is analyzed from the temperature curve (see Figure 1): When the PCB enters the elevated temperature zone (drying zone), the solvent and gas in the solder paste evaporate. At the same time, the flux in the solder paste wets the pads and the components. Head and pins, solder paste softened, slumped, covering the pad, the pad, component pins and oxygen isolation; PCB into the insulation area, so that PCB and components are fully warmed up, in case the PCB suddenly Into the welding zone heating up too fast and damage the PCB and components; When the PCB into the welding area, the temperature rises quickly so that the solder paste to a molten state, the liquid solder on the PCB pad, component terminals and pins wetting, diffusion, Diffuse or reflow mixed to form the solder joints; PCB into the cooling area, the solder joints to solidify, complete the entire reflow.
The temperature curve is the key to ensure the welding quality. The temperature rise slope and peak temperature of the actual temperature curve and solder paste temperature curve should be basically the same. The temperature rise rate before 160°C is controlled at 1°C/s to 2°C/s. If the temperature ramp rate is too fast, on the one hand, the components and the PCB are heated too quickly, which can easily damage the components and cause PCB distortion. On the other hand, The solvent in the solder paste evaporates too quickly, which can easily spill metal components and create solder balls. The peak temperature is generally set to be about 20°C to 40°C higher than the melting temperature of the solder paste (for example, Sn63/Pb37 solder paste has a melting point of 183°C and the peak temperature should be set at about 205°C to 230°C), and the reflow time For 10s to 60s, low peak temperature or short (re)flow time will result in insufficient welding. In severe cases, the solder paste will not melt; the peak temperature is too high or the (re)flow time will be longer, resulting in oxidation of the metal powder. Affect the quality of welding, and even damage the components and PCB.
According to the reflow temperature curve and the principle of reflow, the current reflow soldering machine on the market is generally a simple four-zone reflow soldering machine, as well as a large reflow soldering machine in the temperature range of six, eight, or even twelve, and the reflow soldering type QHL320A. The machine adopts 20 sections of programmable temperature control, which is equivalent to a 20-zone reflow soldering machine. This subdivides the reflow temperature curve, and thus the temperature control is more accurate, and the ideal reflow temperature curve is further fitted to achieve perfect welding.
How to ensure a good welding quality? QHL320A reflow soldering machine in addition to control in full compliance with the reflow temperature curve, but also allows users to truly understand the principle of reflow soldering. The QHL320A reflow soldering machine has the function of a large-size transparent window. The user can control the entire welding process through the transparent window. At the same time, the solder paste can be observed during the entire welding process, easily discovering problems in the welding process, through the parameters. Adjustments are improved to ensure good welding quality. At the same time, QHL320A reflow soldering machine is a small desktop reflow soldering machine. It adopts full static welding, which effectively prevents the tiny vibration generated by the crawler type transmission of the large-scale multi-temperature zone reflow soldering machine. This vibration may melt the solder paste in the soldering zone. Under the impact of the tiny pitch IC (such as pitch ≤ 0.5mm) and components (such as 0603, 0402 and 0201, etc.) welding, resulting in component drift, solder beads, solder bridges and other welding defects, and full static welding is completely Avoid the above possible defects.
Set back (re)flow soldering temperature curve basis:
1. Set according to the temperature profile using solder paste. Solder pastes with different metal contents have different temperature profiles. The temperature profile of the specific product should be set according to the temperature profile provided by the solder paste manufacturer.
2, according to the PCB material, thickness, whether the multilayer board, size, etc.;
3ã€According to the density of surface mounting board mounted components, the size of components, and whether there are special components such as BGA, CSP, etc.
4, according to the specific circumstances of the equipment, such as: the length of the heating zone, the heating source material, back (re)flow furnace structure and heat conduction and other factors set.
Hot air reflow soldering machine and infrared reflow soldering machine are very different: infrared reflow soldering machine is mainly radiation conduction, its advantages are high thermal efficiency, high temperature steepness, double-sided soldering PCB easy to control the temperature, its disadvantages Because the temperature is not uniform, the temperature of the device is different due to the color, material, and size of the device on the same PCB. In order to achieve the soldering temperature of the bulk components of the solder joint around the dark color device, the soldering temperature must be increased. Hot air reflow soldering machine is mainly convection conduction, its advantages are uniform temperature, good welding quality; the disadvantage is that the temperature difference between the upper and lower PCB and the temperature gradient along the length direction of the welding furnace is not easy to control.
With the advantages of hot air reflow and infrared reflow soldering and the technology and advantages of large reflow soldering machines, China Aviation Industry Group No. 1 Beijing Qingyun Innovation Technology Development Co., Ltd. has launched the QHL320A-SMT compact combination of infrared heating and forced hot air circulation. Precision bench reflow machine. Combining the company's powerful military aviation technology capabilities, eight years of professional research, development and production process experience, independent research and development and production of small and complete SMT mounting and welding equipment suitable for R&D, small and medium batch production of various types of enterprises and research institutes: SMT small precision tabletop reflow soldering machine series (â—QHL320 classic type â—QHL320A enhanced type â—QHL360 lead-free type), tracked online reflow machine, manual screen printing station, anti-static vacuum suction pen, precision IC placement table, component rack, etc. . Another BGA positioning placement system, semi-automatic placement machine, high-precision silk screen, semi-automatic dispensing machine, temperature tester, electronic insulation box (for the use of solder paste), magnifying glass and other auxiliary equipment.
Paper cord,
Product description:
Twisted Paper Cord is use of high-quality pure wood pulp paper production, into a single round, commonly used specifications: diameter 1.0mm-5.5mm between
Twisted Paper Cord Finished shape:
1, according to the length of the customer cut into a strip or processed into Paper Bag handle;
2, rewinding into a coil-like (conventional standards: 3mm 5000 m / roll, 3.5-4mm, 3500 m / volume), can also be adjusted according to customer requirements for each volume of rice, for automatic bag machine, hand-cranked machine use.
Paper Rope,Colorful Twisted Paper Cor,Thick Twisted Paper Cord,Brown Color Twisted Paper Rope
DongGuan FeiYang Packaging Machinery Equipment Co., Ltd , https://www.feiyang-machinerys.com