Surface Mount Technology, or SMT has emerged as a game-changer in the electronics industry, offering numerous advantages over traditional through-hole technology. See more about this technology on this page here.
Components are mounted directly onto the surface of the printed circuit board or PCB, and there is no need for bulky leads or holes to accommodate them, allowing for more compact and lightweight designs, making it ideal for portable devices such as smartphones and tablets.
SMT allows for automated assembly techniques that can improve efficiency during the manufacturing process, such as pick-and-place machines, which can quickly and accurately position components on PCBs. Companies are now able to have faster production times and meet the demands of their customers when necessary.
Higher frequency benefits are also due to the reduction of the parasitic effects of the other components. Better thermal performance was also recognized because the smaller components made for better thermal management and heat dissipation. It essentially reduced the instances of failures from happening because of too much vibration. Increased density opens up opportunities for advanced functionality within smaller form factors.
Components Used in SMT: Metal Film Resistors
Resistors are shaped rectangularly, and they are metalized at either end where the electrode bases exist and fired so they will be held in place. The metal film resistors are then deposited as a thin material, and it will be trimmed with a YIG laser afterwards.
Two types are generally used when construction, and the thicker ones are made by a paste based on ruthenium dioxide or a similar material. High-purity alumina substrate serves as the flat base, and the method is different from the method of depositing the films in axial resistors or round cores. Resistance values are obtained by the trimming and paste composition.
Thinner ones have protectors like tin-lead that are solderable terminations or glass passivation. The adhesion layer in the form of silver and the nicker underplating are dipped in coating, and the materials used are essential when it comes to the soldering of the terminals to prevent leaching.
R-packs are used as replacements of discrete resistors, and they save placement time and area. They are often based on the small outline integrated circuits, but they can vary in wattage and dimensions. Surface mount capacitors for the SMT are ideal for high-frequency applications because of the absence of leads. They are used for frequency controls and decoupling applications for aerospace, automotive, and military equipment.
More about the Materials
Resistors made of metal films are one of the more popular materials out there because they offer superior performance. The resistive elements on non-conducting bodies can be common in axial types, and they work in the same principle as the metal layers.
They are made to have a very high tolerance because the length, width, and thickness are all controlled. Long-term stability can be expected of them, and the metal ensures that they are not going to rapidly downgrade. Because of their advantages, they are preferred by the experts in the industry compared to metal oxide.
Utilizations may apply to low-noise analog signals, filters, and bridge circuits, know that these are not meant to be used for something that can expose them to surge transients. Helical cuts are common with them, and the construction is done by vacuum deposits. The thicker the metals, the more it’s going to provide stability.
Expect that the mix of deposits may include NiCr or nickel chromium, tantalum nitride, gold with platinum, and others, depending on the application. See the post about tantalum nitride at this link: https://iopscience.iop.org/article/10.1143/JJAP.10.248. Incorporation is next after the metals are pressed together, and the trimmings can be achieved with lasers. Adding markings may also be part of the process because the coating may consist of resin where various layers are baked on them.
Benefits to Know About
Metal films offer several benefits and have a wide range of applications in various electronic devices. With their high precision and stability, they can provide consistent resistance values over time, ensuring accurate performance in electronic circuits.
High-end audio equipment requires the careful selection of the resistors to minimize distortion or noises in the signal paths. Thin films are homogeneous in their structures, and the tantalum nitride, nickel-chromium, and silicon chromium act as resistive materials on the ceramic substrate. A layer of thickness can vary from 10 to 500 angstroms, and some of the noises can be the result of surface imperfection, occlusions, and non-uniform depositions.
The lowest noises were observed in those with foil, wire-wound, and bulk metal around them, but with this option, these varieties can chop the signal peaks and affect audio quality. Foil resistors are more structured with chemical etches to counteract this, but industries still prefer the metal film types that exhibit low voltage coefficient characteristics, reducing the impact of voltage variations on their resistance values. This feature makes them suitable for precise voltage references or measurement circuits.
Selecting the Right Ones for your Project
Many options might be available in the market, so it’s important to consider certain factors that will ensure optimal performance and reliability. Determining the required resistance value for your application is a good starting point because these materials come in various resistance values, ranging from a few ohms to several megaohms. It is essential to choose one with the correct rating that matches your circuit requirements.
Consider the power rating, which is an indication of the amount of electricity the resistor can handle without overheating or getting damaged. Make sure to select one with an adequate value or higher than what your circuit requires to avoid any potential issues and damages.
Tolerance is another factor for consideration, and this refers to how closely the actual resistance value of the material aligns with its specified nominal value. Sometimes, the higher tolerance will mean a huge percentage of manufacturing errors, but it will still depend on the amount of engineering involved and the environmental parameters that were followed.