Surface mount technology is a part of the electronic assembly that deals with the mounting of electronic components to the surface of a PCB. Electronic components mounted this way are called surface-mounted devices (SMD).

Link to Hayawin

SMT was developed to minimize manufacturing costs while making efficient use of board space. The introduction of surface mount technology has enabled manufacturers to fabricate smaller size complex circuit boards. There are various advantages and disadvantages of surface mount technology which we will discuss over the course of this article.

The advent of surface mount technology

Surface-mount technology was developed in the s and was broadly used in the s. By the s, they were used in most of the high-end PCB assemblies. Conventional electronic components were redesigned to include metal tabs or end caps that could be attached directly to the board surface. This replaced typical wire leads which needed to pass through drilled holes. SMT led to much smaller components and enabled component placement on both sides of the board. Surface mounting enables a higher degree of automation minimizing labor costs and expanding production rates that results in the development advanced of boards.

Salient features of SMT and through-hole technology

SMT allows electrical components to be mounted on the board surface without any drilling. Most electronic applications prefer to use surface mount components since they are compact and may be installed on either side of a printed circuit. They are suitable for applications with higher routing densities. These components have smaller leads or no leads at all and are smaller than through-hole components.

The process involved in SMT assembly is:

• Apply solder paste to the fabricated circuit board using stencils. Solder paste is made up of flux and tin particles.
• Attach the surface mount components.
• Use a reflow method for soldering.

In through-hole technology, the component leads are inserted into the drilled holes on the board. These leads are then soldered to pads on the opposite side using wave soldering or re-flow soldering tools. Since through-hole mounting offers strong mechanical bonds, it is highly reliable. However, drilling PCBs during production tends to increase manufacturing costs. Also, through-hole technology limits the routing area for signal traces below the top layer of multi-layer PCBs.

Major differences between through-hole technology and surface mount technology

• SMT frees up the limitation on board space posed by the through-hole mounting manufacturing process.
• Through-hole components involve higher manufacturing costs than SMT components.
• You require advanced design and production skills for using SMT when compared to through-hole technology.
• SMT components can have a higher pin count as compared to through-hole components.
• Unlike through-hole technology, SMT enables assembly automation which is suitable for high production volumes at lower costs when compared to through-hole production.

• SMT components are more compact leading to higher component density as compared to through-hole mounting.
• While surface mount leads to lower production costs, capital investment for machinery is higher than needed for through-hole technology.
• Through-hole mounting is better suited to the production of large and bulky components that are subjected to periodic mechanical stresses or even high-voltage and high-power parts.
• SMT makes it easier to achieve higher circuit speeds because of its reduced size and fewer holes.

Factors to consider before choosing SMT or through-hole technology

• Stability of the component when exposed to external stress
• Ease of thermal management/ heat dissipation
• Availability of the part and its alternative
• Cost-effectiveness of assembly
• High performance and life-span of the package
• Facilitate rework in case of board failure

Advantages of surface mount technology

SMT has many advantages over conventional through-hole technology:

• Surface mount technology supports microelectronics by allowing more components to be placed closer together on the board. This leads to designs that are more lightweight and compact.
• The process for SMT production setup is faster when compared to through-hole technology. This is because components are mounted using solder paste instead of drilled holes. It saves time and labor-intensive work.

• Components can be placed on both sides of the circuit board along with a higher component density with more connections possible per component.
• Due to the compact size of the package, higher-density traces can be accommodated on the same layer.
• The surface tension of molten solder pulls components into alignment with solder pads, which automatically corrects minor placement problems.
• Compared to through holes, these do not expand in size during the operation. Hence you can reduce the inter-packaging space.
• Electromagnetic compatibility is easily achievable in SMT boards because of their compact package and lower lead inductance.
• SMT enables lower resistance and inductance at the connection. It mitigates the undesired effects of RF signals and provides better high-frequency performance.
• More parts can fit on the board easily due to their compactness, resulting in shorter signal paths. This enhances signal integrity.
• The heat dissipated is also lesser than through-hole components.
• SMT reduces board and material handling costs.
• Enables you to have a controlled manufacturing process. This especially opted for high-volume PCB production.

Ensure the manufacturability of your circuit design using the Better DFM tool.

Disadvantages of surface mount technology

Even though SMT has several advantages, the technology also comes with it certain disadvantages:

• When you subject components to mechanical stress, it is not reliable to use surface mounting as the sole method of attachment to the PCB. This is because you need to use component connectors to interface with external devices that are periodically removed and re-attached.
• Solder connections for SMDs might be damaged through thermal cycles during operations.
• You would need highly skilled or expert-level operators and expensive tools for component-level repair and manual prototype assembly. This is because of the smaller sizes and lead spaces.
• Most SMT component packages can't be installed in sockets that enable easy installation and replacement of failed components.
• You use less solder for solder joints in SMT, therefore the reliability of solder joints becomes a concern. Void formation might lead to solder joint failures here.
• SMDs are typically smaller than through-hole components leaving lesser surface area for marking part IDs and component values. This makes identifying components a challenge during prototyping and repairing the PCB.
• The solder can melt when exposed to intense heat. Therefore, SMT cannot be implemented in electrical load circuits with high heat dissipation.
• PCBs that use this technology requires more installation costs. This is because most of the SMT equipment such as the hot air rework station, pick and place machine, solder paste screen printer, and reflow oven are expensive.

• Miniaturization and a variety of solder joints can make the procedure and inspection more difficult.
• Due to compact size, there is an increased chance of solder overflow that can result in short circuits and solder bridge.

Design for Testing Handbook

7 Chapters - 28 Pages - 45 Minute Read

What's Inside:

• PCB testing strategies
• Guidelines to design and place a test point for FPT
• Directives to make your board ICT compatible
• Benefits and drawbacks of various testing methods
• Defects that you can identify through board testing

Download Now

When to use surface mount technology?

The majority of products manufactured at this time utilize surface mount technology. But SMT is not suitable in all cases. Consider SMT considered if:

• You need to accommodate a high density of components.
• The need is for a compact or small product.
• Your final product needs to be sleek and light despite component density.
• The requirement specifies the high-speed/frequency functioning of the device.
• You need to produce large quantities with automated technology.
• Your product should produce very little noise (if any at all).

Guidelines for SMT component placement

Here are some recommendations for SMD placement to maintain good signal and power integrity for your board.

• Keep the components as near as possible to minimize the routing distance.
• Adhere to the signal path as per the schematic while placing the components.
• Never place the components in the return path of sensitive signals. This leads to signal integrity issues.
• For high-speed devices, place the bypass capacitors closer to their power pins. This will reduce parasitic inductance.
• Arrange the SMD together for power supply circuits. This will help you to provide shorter routing and reduce the inductance in the connections.
• Try to keep SMT components on one side of the board to reduce costs associated with stencils and assembly.
• Maintain the minimal spacing between the test points and SMT components as specified by your manufacturer. This spacing may vary depending on the component's height.

To facilitate the assembly process ensure that all component names, polarities, orientations, and placements are marked properly in the assembly drawing. The footprints present in the drawings should match with the actual parts. Consult your manufacturer for their kitting guideline if you are considering consigned assembly. Prepare your BOM accordingly.

Soldering techniques employed in SMT

Solder reflow and wave soldering are widely used to mount components onto the board. Depending on the nature of the components, the designer can choose one of these methods for surface mounting technology.

Wave soldering: Since the solder will flow through the holes to form a connection, wave soldering is mostly used for through-hole components. You can use wave soldering for most of the surface-mount components also.

Solder reflow: This process is generally preferred in SMT. Here, the solder on one pin melts and reflows faster than the other. The only disadvantage is that it causes a tombstoning effect, where the component peels away from the non-melted pad. This effect is common for surface mount components like resistors, capacitors, and inductors.

Surface mount device packages

SMD packages come in a broad range of shapes and sizes as given below:

Common passive discrete components: These components are mostly resistors and capacitors and are a part of most electronic devices available today. Given below are SMD package details for capacitors and resistors.

Transistors: The common type of packages for transistors are as follows:

• SOT-23 (Small Outline Transistor) with dimensions 3 x 1.75 x 1.3mm
• SOT-223 (Small Outline Transistor) with dimensions 6.7 x 3.7 x 1.8Mmm

Integrated Circuit (IC) packages

Integrated Circuit packages come in a wide range as given below:

• Small Outline Integrated Circuit (SOIC)

Small Outline Package (SOP)

TSOP (Thin Small Outline Package)  is thinner than SOIC

• Quad Flat Pack (QFP)

Quad flat packs are generic square, flat IC packages.

• Ball Grid Array (BGA)

BGA packages include an arrangement of solder balls on the chip underside in the place of pins. The ball spacing typically is 1.27, 0.8, 0.5, 0.4, and 0.35mm

• Plastic Leaded Chip Carrier

The chip is enclosed in a plastic mold. It can either be square or rectangular in shape.

Measurement of SMD size

Surface mount component standards are specified by the Joint Electron Device Engineering Council (JEDEC) Solid State Technology Association (JEDEC.org). JEDEC is an independent semiconductor engineering trade organization and standardization body that has its headquarters in Arlington, Virginia, United States.

You can measure SMD size in inches in the Imperial system and millimeters in the Metric system. For the imperial components, the dimensions are 0.02 x 0.01 inches. For the metric components 0.2 x 0.1 mm.

Understanding the advantages and disadvantages of surface mount technology is essential to comprehend its role in the electronics industry. This will always help in optimizing your design and assembly skills. Follow the guidelines listed in this article to completely benefit from the SMT process for component placement. Please comment below if you have any queries on employing surface mount technology for your design. We will be happy to help you.

PCB manufacturing has several steps, including loading and unloading boards on the assembly line, which is crucial. PCB loaders and unloaders are automated machines designed to handle these processes efficiently and accurately. Using the right equipment can significantly improve productivity, quality, and safety in PCB assembly.

PCB loaders take raw PCBs and move them into position for population and soldering. This includes transferring boards from storage onto the assembly line conveyor. PCB unloaders then remove finished boards off the line once assembly is complete. Loaders and unloaders may handle boards individually or in panels, stacks, or magazines depending on the design.

There are several types of PCB loaders and unloaders available to suit different production needs. Selecting the right equipment is key to maximizing process efficiency.

Benefits of Using PCB Loaders and Unloaders

Automated PCB loaders and unloaders offer considerable benefits over manual loading/unloading:

If you are looking for more details, kindly visit Smt Pcb Loader.

Increased Efficiency

Automated systems load and unload boards much faster than human operators. This saves significant labor time and allows higher throughput with fewer bottlenecks.

Improved Accuracy

Automated loading and unloading minimizes human handling errors. Machines place boards precisely for consistent positioning during assembly. This improves quality.

Reduced Risk of Damage

Manual loading/unloading has a higher risk of damaging fragile PCB components and solder joints. Automated systems are more reliable and gentle on boards.

Increased Productivity

By reducing cycle times, improving accuracy, and minimizing defects, PCB loaders/unloaders boost production productivity and yields. This leads to higher profits.

Types of PCB Loaders and Unloaders

There are several categories of PCB loaders/unloaders designed for different needs:

Product Description

SMT pcb loader machine Description:

Our SMT PCB Loader Machine, equipped with advanced features to streamline your PCB assembly process. This equipment boasts a Mitsubishi PLC program control system, ensuring precise and reliable performance for your production needs.

The user-friendly interface is designed with a full-color touch screen man-machine interface control panel, allowing for intuitive operation and easy access to various settings and functions. With automatic, manual, and PASS three working modes, this machine offers versatility and flexibility to adapt to different production requirements.

Constructed with utmost durability in mind, our SMT PCB Loader Machine is made from high-quality 2MM steel plate. The CNC bending process, along with laser cutting technology, ensures precise shaping and accurate dimensions. The carbon dioxide shielded welding technique guarantees a strong and firm structure, eliminating the risk of deformation during operation.

Specifications of SMT Loader

Model 810-SL(Loader) / 810-SU(Unloader) Machine size(mm) L650*W880*H PCB size(mm) Min:L50*W50   Max:L400*W350 Level height 900+/-20 PCB direction Left to right Cycling time The cycle of a single plate is about 6 seconds Maximum board capacity 250MM stack height Thickness of circuit board Min0.6~Max2mm Type of belt Green round non-slip belt Direction of transfer From Left to Right or Right to Left(Option) Power suppy AC220V/50Hz/100W Ari supply 4~6Kg/cm2

Key Features of Pcb Loader Machine:

Mitsubishi PLC program control for precise and reliable operation.
Full-color touch screen man-machine interface control panel for intuitive operation.
Automatic, manual, and PASS three working modes for increased flexibility.
Standard (SMEMA) online signal compatibility for seamless integration with other equipment.
Constructed with 2MM steel plate for exceptional durability and resistance to deformation.
CNC bending and laser cutting for precise shaping and accurate dimensions.
Carbon dioxide shielded welding for a strong and firm structure.
Beauty, safety protection, and a firm structure for a superior user experience.

Application cases

The Function of SMT Loader

The role of SMT loader

SMT PCB loader is a kind of production equipment needed in SMT production line. Its main function is to put the unattached PCB board in the SMT plate mounting machine and automatically feed the board to the suction plate machine. Then the suction plate machine will automatically place the PCB onto the track of the stencil printing machine and upload it to the stencil printing machine for solder paste brushing operation.

Detailed operation process of PCB loader

I. preparation

1. Turn on the power supply and turn on the power switch;

2. Adjust the width of guide rail until it is the same as the width of PCB board to be produced.

II. Set the number of plate feeding steps and the position of plate outlet point (under manual condition and the lifting platform is in the lower limit position)

1. Step Setting: press the button to select Pitch 1/2/3/4;

2, out of the board adjustment;

3. Manually adjust the push rod in the middle of the PCB to be produced;

4. Confirm that the machine can send the board smoothly (the position of the first piece of board);

5. Press the automatic button (to switch to automatic);

6. Press the return key (the lifting platform will automatically descend to the lower limit and then return to the first exit point);

7. Automatic state.

III. Feeding

1. Adjust the anti-static material rack to the same width as the PCB board to be produced, load it into the PCB board and put it into the bearing platform on the upper board;
2. Press the automatic key in the board operation panel;

IV. safe operation requirements

1. Please pay attention to whether the working voltage and air pressure are correct when starting the machine;

2. During automatic operation, it is recommended not to use the other keys unless the emergency button is pressed in an emergency state;

3. Staff are forbidden to lean on or depend on the machine;

4. When lifting the car, do not put your hands around the material frame;

5. pay attention to adjust the plate spacing of the feeding frame, wide easy to lead to drop the plate, tight easy to lead to the card plate;

6. pay attention to adjust the width of the conveyor belt, wide easy to lead to drop the plate, tight easy to lead to card.

Contact us to discuss your requirements of SMT PCB Conveyor. Our experienced sales team can help you identify the options that best suit your needs.