Surface mount technology (SMT) definition refers to a manufacturing technique where electronic components are directly applied to the surface of a printed circuit board (PCB). This method enables automated production to conduct a more extensive assembly, resulting in the creation of a fully functional circuit board.Any electronic element installed in this manner is identified as a surface-mounted component (SMD). In opposition to conventional manufacturing techniques, SMT removes the necessity for elements to be placed through apertures; rather, elements are attached to the board via the process of reflow soldering.
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Initially termed Planar Mounting, IBM pioneered the development and application of SMT in the s for constructing small-scale computers. It subsequently replaced the prior Through-Hole Technology. However, it gained substantial traction only in when surface-mounted components achieved a 10% market share. By the year , the predominant technology utilized in advanced printed circuit assemblies (PCAs) comprised surface-mount devices, commonly known as SMDs.
SMT components feature petite tabs where solder is applied to affix SMDs to the PCBs surface.
During the period of Through-Hole Technology, components were introduced by threading through lead holes that were drilled into PCBs. These holes were dimensioned to precisely fit each component before the soldering process. SMT streamlines the assembly process by circumventing the hole-drilling step; SMDs are swiftly sorted and attached to the PCBs surface with minimal or no lead holes, thereby significantly expediting device assembly.
The process of assembling SMT can be demanding and time-intensive when performed manually, considering the precision needed to attain top-notch surface mount assembly (SMA).Consequently, for improved efficiency, automated assembly machines are predominantly employed in SMT manufacturing, particularly in large-scale production.
surface mount technology components are notably more compact than through-hole components, contributing to the fabrication of sleek and aesthetically pleasing electronic devices suitable for contemporary times. Consequently, SMT finds application in nearly every electronic device today, spanning toys, kitchen appliances, laptops, and smartphones.
Acronym Definition SMA Surface-Mount Assembly A construction or module assembled utilizing SMT. SMC Surface-Mount Components Elements explicitly crafted for utilization in SMT. SMD Surface-Mount Devices Incorporates active, passive, and electromechanical components well-suited for surface mount technology (SMT). SME Surface-Mount Equipment Machinery employed in the Surface Mount Technology (SMT) procedure. SMP Surface Mount Packages Denotes the diverse casing configurations of Surface-Mount Devices (SMD). SMT Surface-Mount Technology The procedure and technique of assembling and mounting electronic technology onto printed circuit boards (PCBs).Surface mount components exhibit distinctions from their leaded counterparts. Rather than being engineered for interconnecting two points, SMT components are crafted for placement on a board and subsequent soldering.
The leads of SMT components do not traverse holes in the board, deviating from the anticipated configuration of traditional leaded components. Different package designs are customized for diverse component types. In a broad classification, these packaging styles can be divided into three main groups: passive components, transistors and diodes, and integrated circuits.The subsequent overview delves into these three classifications of SMT components:
Resistors, Capacitors, and Inductors:
SMT counterparts of resistors, capacitors, and inductors are characterized by compact, planar packages. These components are designed without protruding leads, contributing to a more streamlined and space-efficient arrangement on the Printed Circuit Board (PCB).
1.Small Signal Transistors and Diodes:
SMT iterations of small signal transistors and diodes come in various package styles, including SOT-23 and SOD-323. These packages are meticulously designed to accommodate the diminutive size of these semiconductor devices while enabling convenient surface mounting.
2.Power Transistors and Diodes:
For applications requiring higher power, prevalent SMT packages such as DPAK and TO-252 are employed. These packages are formulated to dissipate heat efficiently while maintaining a compact footprint.
Quad Flat Packages (QFP), Ball Grid Arrays (BGA), and Chip-on-Board (COB):
ICs in SMT are frequently housed in planar packages like QFP or BGA, offering a high pin count within a petite form factor. COB entails directly affixing a semiconductor die to the PCB, conserving space, and facilitating a low-profile design.
In summary, the diverse package styles of SMT components cater to the specific requirements of distinct electronic elements, offering advantages in terms of space efficiency, automated assembly, and adaptability to contemporary design prerequisites.
In summary, the diverse package styles of SMT components cater to the specific requirements of distinct electronic elements, offering advantages in terms of space efficiency, automated assembly, and adaptability to contemporary design prerequisites.
In the initial phase, SMCs are chosen, and the PCB is designed. The board typically features flat copper pads, often plated with silver, tin-lead, or gold and lacking holesreferred to as solder pads. These solder pads provide support for the pins of various components, such as transistors and chips.
Another vital tool is the stencil, utilized to set a fixed position for the ensuing step of the process (solder paste printing), aligning with the predetermined positions of solder pads on the PCB.All materials to be utilized in the manufacturing process, including these, must undergo a thorough inspection for any defects.
This stage holds crucial significance within the Surface Mount Technology (SMT) process. Here, a printer is employed to administer solder paste utilizing a prepared stencil and a squeegee (a cleaning tool in printing) at an angle ranging from 45° to 60°. Solder paste, a putty-like amalgamation of powdered metal solder and adhesive flux, is applied. The flux functions as a temporary adhesive, securing surface mount components in position and simultaneously purifying soldering surfaces from impurities and oxidation.
The solder paste is specifically utilized to establish connections between the Surface Mount Components (SMCs) and the solder pads on the Printed Circuit Board (PCB). Ensuring that each pad receives the correct quantity of paste is imperative. Neglecting to perform this task may lead to ineffective connections when the solder undergoes liquefaction in the reflow oven. In the domain of electronic production, a reflow oven is an electronic heating apparatus employed in Surface Mount Technology (SMT) for attaching electronic components to printed circuit boards (PCBs).
Following the solder paste printing stage, surface mount technology machines, specifically pick-and-place machines, come into play for the precise positioning of components on the PCB. Utilizing either a vacuum or a gripper nozzle, each component is extracted from its packaging, and the placement machine accurately situates it according to its designated location. The PCB advances along a conveyor belt, and these swift and precise machines, capable of placing up to 80,000 individual components per hour, affix electronic components onto it.
Precision is paramount in this process, as any inaccuracies in component placement, once soldered, can incur significant costs and time-consuming rework.
Subsequent to the placement of Surface Mount Components (SMCs), the PCB proceeds to the reflow soldering oven, traversing through various zones to undergo the soldering process:
Preheat Zone: Serving as the initial zone, this section gradually raises the temperature of the board and attached components simultaneously. The temperature ascends at a rate of 1.0-2.0 per second until reaching 140-160.
Soak Zone: In this zone, the board is maintained at a temperature between 140 and 160 for 60-90 seconds.
Reflow Zone:The boards subsequently progress through a region where the temperature rises at a rate of 1.0-2.0 per second, ultimately reaching a peak within the range of 210-230. This specific melting point enables the amalgamation of the tin within the solder paste, effectively connecting the leads of the component to the pads on the PCB.Concurrently, the surface tension of the molten solder keeps the components securely in place.
Cooling Zone: Serving as the concluding section, this zone ensures that the solder solidifies upon exiting the heating zone, preventing joint defects.
For double-sided printed circuit boards, these procedures might be reiterated, utilizing either solder paste or adhesive to anchor the Surface Mount Components (SMCs) in place.
Following the soldering process, the circuit board undergoes thorough cleaning and meticulous inspection for any imperfections. In the event of any identified flaws, necessary repairs are carried out before the final product is placed in storage.
Multiple methods are utilized to inspect Surface Mount Technology (SMT), including magnification tools, Automated Optical Inspection (AOI), flying probe testing, X-ray inspection, and various others.Machine-based methods are favored over manual inspection, ensuring rapid and precise results instead of relying on human observation.
SMT:Components are affixed directly onto the surface of the PCB through the utilization of petite, flat leads or direct soldering onto pads present on the PCB.
Through-Hole: Components possess wire leads that traverse openings in the PCB and are soldered on the reverse side.
SMT: Components in SMT are generally smaller and lighter, enabling higher component density and smaller PCBs.
Through-Hole: Through-Hole components are typically larger, and the holes required for their leads can limit available PCB space.
SMT: SMT assembly is highly automated, utilizing pick-and-place machines for precise component positioning and reflow ovens for soldering.
Through-Hole: Assembly can be manual or automated. Components are inserted into holes, and soldering is typically done through wave soldering or manual methods.
SMT: SMT components are soldered directly to the PCB surface, providing good mechanical strength and vibration resistance.
Through-Hole: Through-Hole components gain mechanical strength from leads passing through the PCB, but the reliance on leads may make them more susceptible to mechanical stress.
SMT: Generally more cost-effective for high-volume production due to automation and smaller component size.
Through-Hole: May be more time-consuming and expensive, especially for large and complex boards, often involving manual labor.
SMT: Offers greater design flexibility, particularly suitable for compact, high-density designs.
Through-Hole: Preferred for designs prioritizing robustness and repairability, or for components not available in SMT packages.
SMT: Reworking SMT components can be more challenging due to the smaller size and densely populated boards.
Through-Hole: Through-Hole components are generally easier to rework and repair.
SMT: Widely adopted in modern electronics manufacturing, especially for high-volume production and miniaturized devices.
Through-Hole: Still used in specific applications, especially where reliability and repairability are critical, or for specialized components.
In contemporary electronics manufacturing, a combination of both SMT and Through-Hole technologies, known as mixed-technology assembly, is often utilized to optimize the benefits of each approach for different components on a single PCB.
Characteristic Through-Hole Surface Mount Finish Type Non-planar HASL most common Planar finish (ENIG, Immersion Silver, OSP) Lead Insertion Method Hole required Components mount to surface pads, no hole Assembly Configuration Rare 2-sided assembly Common 2-sided assembly Lead Spacing Typically 0.100 or greater 0. spacing (0. common) Assembly Method Manual assembly Automated assembly Soldering Manual or automated Typically automated Stencil Requirement Not required Required unless small lot, simple PCB Vias in Pads Not possible Possible Laminate Temperature Standard temperature (130C Tg) High-temperature (170C Tg) Test Points Through-hole Through-hole or SMT Component and Circuit Density Lower density Greatly increased density PCB Footprint Larger Minimal Rework Complexity Relatively simple Some rework more involved Warp and Twist Tolerance Moderate tolerable More critical for assembly Fiducial Pads Requirement Not required Required for automated pick-and-place equipmentIn the world of electronic manufacturing, Surface Mount Technology (SMT) has its pros and cons. On the positive side, it allows for automated assembly, boosting efficiency and reducing labor costs. However, the downside includes challenges in rework and repair due to the small size of SMT components. Lets delve into surface mount technology advantages and disadvantages in electronic production.
SMT is well-suited for advanced technologies such as miniaturization, high-frequency applications, and the integration of complex electronic functionalities.
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Featured content:Its important to note that the choice between SMT and other assembly technologies depends on the specific requirements of the application and the desired balance between size, performance, and ease of manufacturing. Many modern electronic devices use a combination of SMT and Through-Hole technologies in a mixed-technology approach to leverage their respective advantages.
Placement of components in Surface Mount Technology (SMT) is a pivotal stage in the electronic manufacturing process, and accuracy in positioning is imperative for the operational effectiveness and dependability of the end product.Here are some guidelines for SMT component placement, aligning with surface mount technology principles and practice:
By adhering to these guidelines, manufacturers can enhance the accuracy, reliability, and efficiency of the Surface Mount Technology component placement process in electronic manufacturing.
Surface Mount Technology (SMT) is an electronic manufacturing technique where electronic components, encompassing SMT elements, are affixed directly onto the surface of a printed circuit board (PCB). This is in contrast to through-hole technology, where components have leads inserted into holes in the PCB. SMT allows for smaller components and a more automated manufacturing process.
SMT components are mounted onto a PCB during the assembly process using a pick-and-place machine. This automated machine precisely picks up SMT components and places them onto designated locations on the PCB according to the assembly design. This approach is effective, facilitating increased component density and reduced overall dimensions of PCBs.
Reflow ovens play a crucial role in the Surface Mount Technology (SMT) process, specifically in reflow soldering. Following the placement of SMT components on the PCB, the assembly undergoes a reflow oven process. The oven elevates the temperature of the PCB, inducing the liquefaction of the solder paste and the formation of solder joints connecting the components to the PCB. This ensures secure and reliable electrical connections.
Automated Optical Inspection (AOI) is a quality control process in electronic manufacturing, particularly in Surface Mount Technology (SMT). AOI systems use cameras and image processing to inspect solder joints, component placement, and other aspects of the PCB assembly. This technology helps identify defects or anomalies, ensuring that the SMT assemblies meet the required quality standards.
Surface Mount Technology (SMT) provides numerous benefits in comparison to through-hole technology, such as the utilization of smaller components, increased component density, and a manufacturing process that is more automated. SMT enables the production of smaller and lighter electronic devices, improved signal integrity, and increased efficiency in the overall manufacturing process. The transition to SMT has been a significant advancement in electronic manufacturing.
Surface mount technology equipment commonly used in soldering and surface mount technology (SMT) includes soldering irons, reflow ovens, solder paste dispensers, and pick-and-place machines. These tools are essential for the precise placement and soldering of surface mount components onto PCBs. Soldering irons are utilized for manual soldering tasks, while reflow ovens play a crucial role in the automated reflow soldering process, ensuring a controlled environment for melting solder paste and forming reliable connections. Solder paste dispensers are responsible for accurately applying solder paste to PCBs before component placement, and pick-and-place machines automate the precise positioning of components on the board, enhancing efficiency and accuracy in the SMT assembly process.
In conclusion, Surface Mount Technology (SMT) stands as a driving force in the realm of electronic manufacturing, reshaping the landscape of modern devices with its precision and efficiency. The ability to seamlessly integrate components onto printed circuit boards has not only enhanced the performance of electronic devices but has also fostered innovation across industries.
At JHDPCB, we recognize the pivotal role that SMT plays in the development of cutting-edge technology. With a commitment to excellence and state-of-the-art facilities, we pride ourselves on offering superior PCB manufacturing services, including advanced SMT capabilities. At JHDPCB, our team is committed to delivering customized solutions that adhere to the most stringent industry benchmarks. Whether in the domains of consumer electronics, telecommunications, or beyond, our expertise ensures that your PCB requirements are met with precision and reliability. Trust in JHDPCB for quality SMT services, as we continue to be a trusted partner in transforming electronic designs into reality.
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In surface-mount technology (SMT) processes, humidity control is essential to prevent electrostatic discharge (ESD) damage and problems with static electricity or dry air. Among all the methods to control humidity, the Dry Fog* Humidification system from IKEUCHI is the only one able to achieve all seven of these benefits.
*A fog formed out of ultrafine water droplets, each measuring 10 μm or less in diameter, which are created by specialized spray nozzles, to instantly evaporate into the air or bounce off any object instead of bursting on impact.
1. Preventing ESD damage
2. Reducing pick-and-place errors
3. Maintaining consistent solder print quality
4. Reducing airborne particles
5. Significant reduction in operating costs
6. Reducing cooling costs
7. Less sick leave
In this article ESD damage and pick-and-place errors will be discussed, as mentioned in the table of contents under 1 and 2.
When a human body charged with static electricity comes into contact with a conductor, static electricity is discharged and an electric current flows. It only takes a fraction of the possible electricity a human body can discharge to destroy the circuitry or damage the inside of these sensitive components. This is called electrostatic discharge damage or ESD damage.
In recent years, as electronic devices have become smaller and smaller and are equipped with more advanced features, their electronic components are also becoming smaller and smaller. The size of chip resistors and multilayer ceramic chip capacitors mounted on smartphone circuit boards is mainly (0.4 x 0.2 mm), but with the introduction of the (0.25 x 0.125 mm) size in , further miniaturization is expected.
However, as the size of the components decreases, the withstand voltage of the components is also reduced, making them more susceptible to damage. This requires that SMT processes which handle these components, including ICs, take more active precautions.
A first and basic measure is wearing a grounding wrist strap and connecting it to the proper grounding equipment, this will release any electrostatic immediately and protect the components from ESD damage.
In addition, an ionizer (static eliminator) can be used to remove the static charge built up on products or equipment. However, the ionizer is not a perfect solution to prevent ESD damage, since it needs to be installed wherever static electricity is generated, requiring sufficient space for installation.
It is the prevention of static electricity through air humidification that complements the measures taken with ionizers.
IKEUCHIs industrial Dry Fog Humidification System raises the humidity to an appropriate level creating a way for the electrostatic to dissipate making the entire work environment, not just certain areas, less susceptible to electrostatic charge.
Since humidification with Dry Fog helps moisture to directly dissolve into the air, it effectively increases humidity without wetting products, machines, or floors, and prevents static electricity itself from being generated. The system is equipped with a humidity controller that enables automated operation to maintain a uniform humidity level even in large spaces.
The graph below shows the number of in-process defects and humidity levels for each month in a one year period at an IC memory manufacturer prior to installing our humidification system. It indicates that most of the defects occurred during the dry season from November to March.
The installation of the humidification system successfully prevented static electricity from being generated due to low humidity in wintertime and greatly reduced the number of the defects caused by the elecrostatic discharge (ESD).
Electronic components for SMT processes are typically supplied on packaging tape rolled into reels which are set in the feeder section of the mounting machine. The packaging tape consists of a carrier tape with pockets to carry the components to the mounter head, and a cover tape that seals the components into the pockets.
Surface mounting is a process in which multiple nozzles located on the mounting machine pick up the components out of the carrier tape pockets and place them in their predetermined positions on a printed circuit board.
During this process, the feeder peels off the cover tape to expose the components as the carrier tape moves forward and the head with the nozzle moves into position to pick up the components. However, the static electricity generated by the removal of the cover tape can cause components to stick to the tape or pop out of the pocket, resulting in a pickup error due to the missing component.
While unmounted components will be detected in a following inspection, it causes additional work and inspections, which means that a pick-and-place error directly affects productivity.
The graph below shows the relation between the number of pick-and-place errors and the humidity in a surface mount facility, recorded every day for a month. The scale on the left shows the relative humidity level and it clearly indicates that on the days the humidity falls below 40% there is a drastically higher rate of pick-and-place errors. In other words, with appropriate humidity control productivity can be increased by preventing ESD damage and pick-and-place errors.
Controlling humidity in SMT processes provides seven benefits. Among all the methods to control humidity, the Dry Fog Humidification system from IKEUCHI is the only one able to achieve all of these benefits.
1. Preventing ESD damage
2. Reducing pick-and-place errors
3. Maintaining consistent solder print quality
4. Reducing airborne particles
5. Significant reduction in operating costs
6. Reducing cooling costs
7. Less sick leave
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