Quelle est la différence entre SMD et NSMD ?

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Quelle est la différence entre SMD et NSMD ?

Les composants SMD et NSMD sont deux types de semi-conducteurs. Bien que leurs plots soient de taille similaire, les composants NSMD ont des dimensions plus petites. En revanche, les SMD peuvent être déplacés par le fer à souder, tandis qu'un composant à trou traversant peut être fixé mécaniquement avant la soudure.

Les tampons NSMD sont plus petits

Il existe plusieurs différences entre les pastilles NSMD et les pastilles SMD. Tout d'abord, le masque de soudure des pastilles NSMD est beaucoup plus petit. Cela permet au bord de la pastille de laisser un petit espace qui n'existe pas sur les pastilles SMD. La figure suivante montre une vue de dessus et une vue en coupe d'une pastille de type NSMD.

Les pastilles NSMD sont plus petites que les pastilles SMD et conviennent donc mieux aux cartes à haute densité. Ils laissent également plus d'espace entre les pastilles adjacentes et facilitent le routage des traces. C'est pourquoi les pastilles NSMD sont utilisées dans les puces BGA à haute densité. Cependant, les pastilles NSMD sont plus susceptibles d'être délaminées, mais les pratiques de fabrication standard devraient permettre d'éviter ce problème.

En plus d'être plus petits, les coussinets NSMD sont moins chers à fabriquer. Cela est dû au fait qu'ils sont fabriqués à partir de matériaux moins coûteux. Toutefois, cela ne signifie pas qu'ils sont de qualité inférieure. Le choix entre NSMD et SMD dépend de votre application. Par exemple, une carte comportant de grands pads nécessitera un masque de soudure dont l'ouverture est plus grande qu'une carte comportant de petits pads.

Lorsqu'il s'agit de fabriquer des composants BGA, il est essentiel de bien concevoir les pastilles. Les pastilles NSMD sont plus petites parce que les ouvertures du masque de soudure sont plus petites que le diamètre de la pastille de cuivre. Les pastilles NSMD présentent également un risque de bosse de soudure asymétrique, ce qui fait basculer le dispositif sur le circuit imprimé.

Les pastilles NSMD sont utilisées pour les diodes

Les pastilles NSMD sont un type de pastilles d'emballage de diodes qui diffèrent des pastilles SMD sur un point important : un espace est laissé entre le bord de la pastille et le masque de soudure. L'utilisation d'une pastille de type NSMD permet d'améliorer les connexions de soudure et d'obtenir des pastilles d'emballage avec des largeurs de trace plus importantes.

Les plages de soudure d'un circuit imprimé sont soit définies par un masque de soudure, soit non définies par un masque de soudure. La plage définie sans masque de soudure se caractérise par un espace entre le masque de soudure et la plage de contact circulaire. La soudure coule sur le dessus et les côtés de la plage de contact pour créer un joint de soudure de haute qualité.

Le diamètre d'une pastille NSMD est souvent inférieur à celui d'une pastille BGA. Cette taille réduite facilite le routage des traces. Cependant, les pastilles NSMD peuvent être plus sujettes à la délamination que les pastilles SMD. Par conséquent, il est nécessaire d'adhérer aux pratiques de fabrication standard afin de minimiser la possibilité de délamination de la pastille.

Lors du brasage de composants BGA, la conception de la pastille joue un rôle crucial. Une mauvaise plaquette peut entraîner une mauvaise aptitude à la fabrication et des heures coûteuses d'analyse des défaillances. Heureusement, il existe des lignes directrices simples pour la conception des pastilles. Avec un peu d'entraînement, vous pouvez fabriquer les bonnes pastilles NSMD pour vos composants BGA.

Les pastilles NSMD sont utilisées pour les transistors

Lorsque vous utilisez des pastilles NSMD pour les transistors, vous devez vous rappeler qu'une pastille NSMD est plus petite qu'une pastille SMD correspondante. Cette différence est due au fait que les pastilles NSMD ont une plus grande ouverture pour le masque de soudure. Cela permet d'obtenir une plus grande surface pour les joints de soudure, une plus grande largeur de trace et une plus grande flexibilité dans les trous de passage. Cependant, cette différence signifie également qu'une pastille NSMD est plus susceptible de se détacher pendant le processus de soudure.

Le diamètre d'une pastille de cuivre est un facteur clé pour définir la taille d'une pastille NSMD. Les pastilles NSMD sont environ 20% plus petites qu'une boule de soudure, ce qui permet un meilleur routage des traces. Cette réduction est nécessaire pour les puces BGA à haute densité. Cependant, une pastille NSMD est plus sujette à la délamination, mais les pratiques de fabrication standard devraient minimiser ce problème.

Les pastilles NSMD constituent une bonne option pour le soudage des transistors. Ces types de pastilles sont souvent utilisés dans des applications où les transistors doivent être soudés à travers un trou dans un substrat métallique. Le processus de soudure est ainsi plus facile et prend moins de temps. Cependant, l'inconvénient de l'utilisation d'une pastille NSMD est que vous ne pouvez pas obtenir le même niveau de contrôle sur le processus de soudure qu'avec une pastille SMD.

L'autre avantage majeur de l'utilisation des pastilles SMD est qu'elles peuvent être facilement fabriquées. Cette méthode est très populaire pour la fabrication de composants électroniques, car c'est le moyen le plus rentable de créer une carte de haute qualité. En outre, l'approche SMD est également un bon moyen de minimiser le nombre de variables impliquées dans votre conception.

Les défauts les plus courants des circuits imprimés et leurs solutions

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Les défauts les plus courants des circuits imprimés et leurs solutions

There are many problems with PCBs, but some of them are less obvious than others. These problems are called implementation failures and require specialized knowledge to diagnose. For example, Electrostatic discharge, Chemical leakage, Lifted pads, and component shifting are all possible causes of failure. To identify the failure modes, a PCB must be stress tested until it fails.

Décharge électrostatique

Electrostatic discharge (ESD) is a common problem in electronic circuits. It results from the wrong handling of electronic components or an excessive voltage level. In many cases, the resulting damage is latent or catastrophic. This problem can cause a PCB to malfunction partially or completely.

There are several ways to detect and repair electrostatic discharge. While some of these are visible and will affect the performance of the product, others will not. The first method is to inspect the device to determine if any component is affected. In some cases, a minuscule hole will appear on the circuit board.

Chemical leakage

Chemical leakage in PCBs can be a problem for many industries. Although the United States banned the production of PCBs in 1977, they are still found in the environment at very low levels. Environmental cycling is the primary source of ambient PCBs, and they are transported throughout ecosystems. Although these contaminants have low levels, they can have serious effects on humans and the environment.

In addition to their use in electronics, PCBs were also used in the construction of school buildings during the 1950s to 1970s. Many schools had PCB-containing caulk and fluorescent light fixtures. The problem with these products was that they leaked, causing contamination in other building materials and the soil. This caused widespread contamination, which is why they were banned.

Lifted pads

Lifted pads are caused by a number of causes, including excess heat and force during soldering. The result can be an unsatisfactory solder joint. These defects require re-soldering, and can lead to short circuit hazards. Other causes of lifted pads include pollutant contamination, poor cleaning, or insufficient flux. Lifted pads can affect the functioning of circuits and the appearance of the board.

Lifted pads occur most frequently on thin copper layers and boards that lack through-plating. Identifying the root cause of a lift is crucial for preventing further damage. In the case of single-sided circuit boards, the problem is often the result of improper wave soldering. The lift can be prevented by using extreme caution while handling PCBs and avoiding excessive force when handling components.

Component shifting

Component shifting is one of the most common defects encountered in PCB assembly. It can be caused by a number of factors, including the placement of components incorrectly. For example, a component placed in a way that is not oriented correctly may float, resulting in a realignment of the component.

In some cases, the cause of component shifting is due to mismatching of the parts to the pad geometry. This causes the component to move towards the thermal mass closest to it. Other causes include bent leads, improperly placed components, or oxidation. Fortunately, there are a number of solutions to component shifting. For instance, adhering to the correct reflow profile, reducing movement during the unreflowed assembly process, and using an aggressive flux can all help minimize component movement.

Soldering ball defects

Soldering ball defects are common in the SMT assembly process. They are essentially balls of solder that separate from the main body of the solder. To prevent them, you should adjust the mounting pressure on the chip mounter to a precise setting. This will prevent the solder paste from being squeezed out of the pad and increase the chance that the solder paste will be generated properly.

A good solder joint will be clean, symmetrical, and have a concave shape. On the other hand, a bad solder joint may be large and have a long stem. Another common defect is disturbed joints, which will have a flaky, distorted, or uneven appearance.

Thermal imaging

Thermal imaging is a powerful tool for quality control, speeding up PCB and component repairs. By identifying hot spots, thermal images can point out faulty components or areas that are using too much power. This information can help designers reduce power consumption and prolong battery life. Thermal imaging can also detect areas that have poor thermal management, requiring more cooling, larger heat sinks, or even redesign.

Thermal imaging for PCB defects can also help designers and engineers determine the cause of defects. When a test board fails to pass quality control tests, a thermal imager can reveal the problems. It can also show the differences in temperature between two different areas of a board, revealing how the two differ.

5 Factors Impacting Quality of SMT Soldering

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5 Factors Impacting Quality of SMT Soldering

Several factors impact the quality of SMT soldering. These include equipment state, Solder paste quality and Stability. Understanding these factors will help you improve your SMT soldering processes. The best way to improve the quality of SMT soldering is to implement improvements in every area.

Stabilité

In a manufacturing process where components are placed on a PCB, the stability of the solder joints is important to the performance of the circuit. However, in certain conditions, the soldering process can be unstable. In these conditions, lead-free SnAgCu soldering paste is used to reduce thermal stress on the substrate. This type of solder paste has an advantage over other materials: it can be used on various substrates and can be applied by dispensing the paste onto the device surface.

A good solder paste will be stable to a specified temperature. The best way to check the stability of your solder paste is to use a viscometer to measure its viscosity. A good paste should be between 160 Pa*S and 200 Pa*S.

Repeatability

During the soldering process, the flux is a key ingredient for the successful soldering process. If the flux is insufficient or there are too many impurities, the soldering process can fail. The best way to ensure the repeatability of SMTS soldering is to carefully prepare components and PCB pads before soldering. It is also important to properly maintain the temperature of the reflow and to avoid any movement of the assembly during reflow. Lastly, the alloy must be analysed for any contaminants.

While lead-free solders are recommended, leaded solder can be used in certain cases. However, it is important to note that leaded solder does not have the flux needed to make reliable joints. As a result, the soldering process is not repeatable.

Equipment state

Many factors affect the quality of SMT soldering. These factors include the design of PCB pads, the quality of the solder paste, and the state of equipment used for manufacturing. Each of these factors is fundamental for reflow soldering quality insurance. Moreover, they can also influence soldering defects. To improve soldering quality, it is essential to use excellent PCB pad designs.

In addition to the selection of components, the mounting precision is another factor affecting the quality of the solder joint. The equipment used for mounting must have high precision so that the components remain stable. In addition, the mounting angle should be correct to ensure that the polar device is correctly oriented. Also, the thickness of the component after mounting must be appropriate.

Solder paste quality

Soldering defects can be the result of a variety of factors. Often, these problems are caused by improper PCB design. Incorrect pad design can result in components that shift or tombstone-shape, as well as soldering defects. For this reason, the design of PCB pads should be carefully scrutinized to avoid these problems.

Temperature and humidity play a significant role in the quality of solder paste. An ideal temperature for application is around 20 degrees Celsius and the right humidity is between thirty to fifty percent. High moisture levels can cause balls to form, which affects the soldering process. Scraping blade speed and quality are also important factors that affect soldering. For optimal results, solder paste should be applied starting from the core and move towards the edges of the board.

Speed, scraper pressure, stencil descending speed, and stencil cleaning mode should all be optimized for maximum solder paste printing. Improper speed can result in uneven solder paste printing and may reduce production efficiency. Another critical parameter is stencil cleaning frequency. Too high or too low stencil cleaning speed can cause a buildup of tin, which can affect production efficiency.

PCB design

PCB design is a critical aspect of manufacturing quality. It involves the proper positioning of components on the board to ensure that they are mounted correctly. It should include enough clearance for mechanical fixing holes. Otherwise, the delicate components can be damaged. In addition, solder joints near the footprints of surface mount components may result in shorts. Hence, it is essential that the PCB design allows for the proper placement of both conventional and surface mount components.

In addition to the correct placement of components, the proper PCB design can also contribute to SMT soldering. According to HP statistics, about 70 to 80 percent of manufacturing faults are caused by defects in the PCB design. The factors that affect the design of the PCB include component layout, thermal pad design, component package types, and assembly method. The PCB design must also consider electromagnetic compatibility (EMC) points and via positions.

How High Thermal Conductivity PCB Material Will Solve the Heat Dissipation Problem

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How High Thermal Conductivity PCB Material Will Solve the Heat Dissipation Problem

PCBs, also known as printed circuit boards, are layered structures made of copper foils sandwiched between glass-epoxy layers. These layers serve as a mechanical and electrical support for components. The high-conductivity copper foils serve as the conductive circuit in the PCB, while the glass-epoxy layer serves as the non-conductive substrate.

High thermal conductivity pcb material

Thermal conductivity is the ability of a material to transfer heat away from a device. The lower the thermal conductivity, the less efficient the device is. High thermal conductivity materials can eliminate the need for vias and produce a more uniform temperature distribution. This also reduces the risk of localized volumetric expansion, which can lead to hotspots near high-current components.

A typical PCB for a personal computer might consist of two copper planes and two outer trace layers. Its thickness is about 70 um and its thermal conductivity is 17.4 W/mK. The result is that the typical PCB is not an efficient heat conductor.

Copper coins

Copper coins are small pieces of copper embedded into the PCB. They are placed under the component that produces the most heat. Their high thermal conductivity allows them to transfer heat away from the hot component to a heat sink. They can be made in different shapes and sizes to fit the desired areas and can be metalized to ensure a tight connection.

Glass-epoxy

The problem of heat dissipation is becoming more important in electronics. Excess heat can lead to underperformance and early failure. Currently, heat dissipation options are limited, particularly in the extreme environments. One of the solutions to this problem is the use of high-temperature glass epoxy PCB material, or HDI-PCB. This material is able to solve this problem by having a thermal conductivity over two hundred times better than FR4 composite.

The glass epoxy resin has excellent heat and flame resistance. It has a high glass transition temperature and high thermal conductivity. It can serve as an insulating layer and a heat dissipation layer. It can be made by impregnation or coating. The thermal conductivity of glass epoxy PCB will improve the performance and stability of electronic components.

Metal core PCBs

Metal core PCB manufacturers have introduced new board substrates that can withstand high temperatures. This allows them to selectively apply thicker copper layers that have higher thermal conductivity. This type of PCB enables better heat dissipation and can be used for fine circuit patterns and high-density chip packaging.

In addition to offering higher thermal conductivity, metal PCBs are also dimensionally stable. Aluminum metal core PCBs have a 2.5-3% size change when heated, making them ideal for high-power applications. Their low thermal expansion properties also make them suitable for high switching power. The most commonly used metal used for a metal core PCB is aluminum, which is cheap and recyclable. Its high thermal conductivity allows for a fast cooling process.

Another problem associated with heat dissipation is the risk of excessive heat. The heat generated by heat-generating components must be removed from the board, otherwise the PCB will not perform at its best. Fortunately, there are now new options to solve this problem. High thermal conductivity metal core PCBs are a new kind of thermal solution that can overcome these problems.

FR4 substrates

PCBs are layered structures made of copper foils and glass-reinforced polymers. They support and connect electronic components. The copper creates a conductive circuit within the PCB, while the glass-epoxy layer acts as a nonconductive substrate.

High-power components are best placed near the center of the PCB, rather than on the edges. This is because heat accumulates near the edges and scatters out. Also, heat from high-power components should be placed far away from sensitive devices, and the heat must be channeled away through the PCB.

High thermal conductivity PCB material is the best solution for heat dissipation, allowing for rapid transfer of heat and preventing heat accumulation. High-tech PCBs use copper base, aluminum, or ceramic as the substrate material. This will solve the heat dissipation issues and make the PCBs more durable.