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JingHongYi PCB (HK) Co., Limited

Surface Mount (SMT) Assembly
Surface Mount Assembly SERVICES

SMT Assembly Services  | JHYPCB

Surface Mount Assembly, Surface-mount technology, also called SMT Assembly -- Components are mounted by placing them directly onto the PCB's surface. SMT was developed to reduce manufacturing costs and also to make more efficient use of PCB space. As a result of the introduction of surface mount technology it is now possible to build highly complex electronic circuits into smaller and smaller assemblies with good repeatability due to the higher level of automation.

SMT provides excellent space utilization, and a very high degree of circuit reliability. Surface Mount Technology remains one of the most economical technologies for many applications.

JHYPCB is an experienced SMT assembly house, providing solutions for Complete PCB Assembly to many clients across a multitude of industries. We have been assembling SMT designs for 8 years now, and we take pride in the High Quality PCB Assembly we perform. Our employees are highly trained PCB experts, We have the capabilities to assemble SMT prototype PCB in small production runs with manual and/or automated SMT production processes, including single- or double-sided component insertions.

Our production facilities can assemble the following SMT types:

  • Ball Grid Array (BGA)
  • Ultra-Fine Ball Grid Array (uBGA)
  • Quad Flat Pack No-Lead (QFN)
  • Quad Flat Package (QFP)
  • Small Outline Integrated Circuit (SOIC)
  • Plastic Leaded Chip Carrier (PLCC)
  • Package-On-Package (PoP)
  • Small Chip Packages (pitch of 0.2 mm)

and various other small chip packages that have a Pitch of 0.2mm (8 mils) or larger. Through Hole Parts are also no problem. For passive parts, we can work with chip packages as small as 0201, and we offer a selection of Free Passive Parts from our stock for our Full Turnkey PCB Assembly clients.

We Work with Your Design in Mind

We Work with Your Design in Mind

Our PCB Assembly Process is carefully matched to your design and your specific constraints, so you can rest assured that your SMT parts will be soldered flawlessly every time. We will review the SMT PCB assembly design you submit during our free DFM Checking stage, and we might make some suggestions, but you are always in complete control of the project. We will happily work with your engineers in order to produce exactly the SMT assemblies you need. We thoroughly review and follow the reflow surface mount soldering requirements of each individual SMD component for each assembly job we undertake. We have a very high yield as we implement precise control of the Reflow Soldering process.

In order to detect the joint soldering SMT quality, we employ a variety of verification and inspection methods, including repeated Visual Inspections, Automated Optical Inspection (AOI), and X-Ray Inspection. For leadless parts such as QFN, DFN and BGA packages, there is no way to perform a direct visual inspection. By using 3D X-ray inspection, many of the issues with SMT soldering can be detected - this is very important for BGA Assemblies.

We're happy to work with you on your project and offer whatever help we can, regardless of where you are in the design process. We can provide DFM advice from the earliest stages of your design. Once your project advances, we'll give you quick turnaround times for prototypes and maximum flexibility for your production runs.

SMT Assembly Advantages

SMT Assembly Advantages | JHYPCB

The main advantages of SMT over the older through-hole technique are:

  • Smaller components.

  • Much higher component density (components per unit area) and many more connections per component.

  • Components can be placed on both sides of the circuit board.

  • Higher density of connections because holes do not block routing space on inner layers, nor on back-side layers if components are mounted on only one side of the PCB.

  • Small errors in component placement are corrected automatically as the surface tension of molten solder pulls components into alignment with solder pads. (On the other hand, through-hole components cannot be slightly misaligned, because once the leads are through the holes, the components are fully aligned and cannot move laterally out of alignment.)

  • Better mechanical performance under shock and vibration conditions (partly due to lower mass, and partly due to less cantilevering)

  • Lower resistance and inductance at the connection; consequently, fewer unwanted RF signal effects and better and more predictable high-frequency performance.

  • Better EMC performance (lower radiated emissions) due to the smaller radiation loop area (because of the smaller package) and the lesser lead inductance.

  • Fewer holes need to be drilled. (Drilling PCBs is time-consuming and expensive.)

  • Lower initial cost and time of setting up for mass production, using automated equipment.

  • Simpler and faster automated assembly. Some placement machines are capable of placing more than 136,000 components per hour.

  • Many SMT parts cost less than equivalent through-hole parts.

  • A surface mount package is favored where a low profile package is required or the space available to mount the package is limited. As electronic devices become more complex and available space is reduced, the desirability of a surface mount package increases. Concurrently, as the device complexity increases, the heat generated by operation increases. If the heat is not removed, the temperature of the device rises shortening the operational life. It is therefore highly desirable to develop surface mount packages having high thermal conductivity.

SMT Assembly Disadvantages

SMT Assembly Disadvantages

  • SMT is unsuitable for large, high-power, or high-voltage parts, for example in power circuitry.[citation needed] It is common to combine SMT and through-hole construction, with transformers, heat-sinked power semiconductors, physically large capacitors, fuses, connectors, and so on mounted on one side of the PCB through holes.

  • SMT is unsuitable as the sole attachment method for components that are subject to frequent mechanical stress, such as connectors that are used to interface with external devices that are frequently attached and detached.

  • SMDs' solder connections may be damaged by potting compounds going through thermal cycling.

  • Manual prototype assembly or component-level repair is more difficult and requires skilled operators and more expensive tools, due to the small sizes and lead spacings of many SMDs. Handling of small SMT components can be difficult, requiring tweezers, unlike nearly all through-hole components. Whereas through-hole components will stay in place (under gravitational force) once inserted and can be mechanically secured prior to soldering by bending out two leads on the solder side of the board, SMDs are easily moved out of place by a touch of a soldering iron. Without expert skill, when manually soldering or desoldering a component, it is easy to accidentally reflow the solder of an adjacent SMT component and unintentionally displace it, something that is almost impossible to do with through-hole components.

  • Many types of SMT component packages cannot be installed in sockets, which provide for easy installation or exchange of components to modify a circuit and easy replacement of failed components. (Virtually all through-hole components can be socketed.)

  • SMDs cannot be used directly with plug-in breadboards (a quick snap-and-play prototyping tool), requiring either a custom PCB for every prototype or the mounting of the SMD upon a pin-leaded carrier. For prototyping around a specific SMD component, a less-expensive breakout board may be used. Additionally, stripboard style protoboards can be used, some of which include pads for standard sized SMD components. For prototyping, "dead bug" breadboarding can be used.

  • Solder joint dimensions in SMT quickly become much smaller as advances are made toward ultra-fine pitch technology. The reliability of solder joints becomes more of a concern, as less and less solder is allowed for each joint. Voiding is a fault commonly associated with solder joints, especially when reflowing a solder paste in the SMT application. The presence of voids can deteriorate the joint strength and eventually lead to joint failure.

  • SMDs, usually being smaller than equivalent through-hole components, have less surface area for marking, requiring marked part ID codes or component values to be more cryptic and smaller, often requiring magnification to be read, whereas a larger through-hole component could be read and identified by the unaided eye. This is a disadvantage for prototyping, repair, or rework, and possibly for production set-up.

Surface Mount Assembly Process - How does SMT electronics assembly work?

Surface Mount Assembly Process

The surface mount assembly process starts during the design phase when the many different components are selected and the PCB is designed using a software package such as Orcad or Cadstar (others are available).

It is important to realise that the process starts at this stage as this is the best time to incorporate as many design features as possible that will make production straight forward and head-ache free. Quite often circuits are taken from the schematic design phase to PCB layout with the main considerations being the functionality, which of course is very important, but design for manufacture (DFM) should ideally be incorporated.

Once the PCB design has been finalised and components selected the next phase is to send the PCB data away to a PCB manufacturing company and components bought in the most suitable way to facilitate automation. The PCB panel design should be considered and specification created to ensure that the format that the PCB's are received is as expected and suitable for the machines to be used.

Components are available packaged in many different ways such as on reels, in tubes or in trays. Most are available on reels which is preferred but sometimes due to Minimum Order Quantities (MOQ's)' components are quite often supplied in tubes or in short strips of tape. Both of these packaging types can be used but do need appropriate feeder types. Components supplied loose in bags should be avoided if possible as can lead to hand placements or the need for special feeding plates.

  • Machine programming - Gerber / CAD to Centroid / Placement / XY file

Having received the PCB panels and components the next step is to setup the various machines used with the manufacturing process. Machines such as the placement machine and AOI (Automated Optical Inspection) will require a program to be created which is best generated from CAD data but quite often this isn't available. Gerber data is almost always available as this is the data required for the bare PCB to be manufactured. If Gerber data is the only data available then the creation of the centroid / placement / XY file can be very time consuming and so Surface Mount Process offer the service to generate this file.

  • Solder Paste Printing

The first machine to setup in the manufacturing process is the solder paste printer which is designed to apply solder paste using a stencil and squeegees to the appropriate pads on the PCB. This is the most widely used method for applying solder paste but jet printing is becoming more popular, especially in the sub-contract sector as there is no need for stencils and modifications are easier to make.

Solder Paste Printing

Keeping control of this process is critical as any printing defects, if undetected, will lead to defects further down the line. With assemblies becoming more complex the design of the stencil is key and care must be taken to ensure a repeatable and stable process.

  • Solder Paste Inspection (SPI)

Most solder paste printing machines have the option of including automatic inspection but, depending on the size of the PCB, this process can be time consuming and so a separate machine can often be preferred. The inspection systems within solder paste printers use 2D technology whereas the dedicated SPI machines use 3D technology to enable a more thorough inspection including solder paste volume per pad and not just print area.

Solder Paste Inspection (SPI)

  • Component Placement

Once the printed PCB has been confirmed to have the correct amount of solder paste applied it moves into the next part of the manufacturing process which is component placement. Each component is picked from its packaging using either a vacuum or gripper nozzle, checked by the vision system and placed in the programed location at high speed.

Component Placement

There is a large variety of machines available for this process and it depends greatly on the business to what type of machine is selected. For example if the business is focused around large build quantities then the placement rate will be important however if the focus is small batch/high mix then flexibility will be more important.

  • Pre-Reflow Automated Optical Inspection (AOI)

Following the component placement process it is important to verify that no mistakes have been made and that all parts have been correctly placed before reflow soldering. The best way of doing this is by using an AOI machine to make checks such as component presence, type/value and polarity.

Pre-Reflow Automated Optical Inspection (AOI)

  • First Article Inspection (FAI)

One of the many challenges for sub-contract manufacturers is the verification of the first assembly to the customers information or first article inspection (FAI) as can be very time consuming. This is a very important step in the process as any errors, if undetected, can lead to high volumes of rework.

  • Reflow Soldering

Once all component placements have been checked the PCB assembly moves into the reflow soldering machine where all the electrical solder connections are formed between the components and PCB by heating the assembly to a sufficient temperature. This would appear to be one of the less complicated parts of the assembly processes but the correct reflow profile is key to ensure acceptable solder joints without damaging the parts or assembly due to excessive heat.

Reflow Soldering

When using lead-free solder a carefully profiled assembly is even more important as the required reflow temperature can often be very close to many components maximum rated temperature.

Post-Reflow Automated Optical Inspection (AOI)

The last part of the surface mount assembly process is to again check that no mistakes have been made by using an AOI machine to check solder joint quality.


With the introduction of 3D technology this process has become more reliable as with 2D inspection there tended to be high levels of false calls due to interpreting a 2D image. 3D inspection has allowed more accurate measurements to be taken and provide a more stable inspection process.

One of the newest features on the inspection machines is that they can be networked together to allow instant feedback to the preceding machine to enable automatic adjustments to be made. For example the AOI machine can be connected to the placement machine so that component placement positions can be adjusted and the SPI machine can be connected to the printer to allow adjustments to be made to the alignment of PCB to stencil.


An Increase in Efficiency and Productivity

It`s a shocking statistic to read that within the electronics industry many surface mount operations, particularly within the sub-contract manufacturing sector, run as low as 20% efficient.

There are many reasons that contribute to this figure but it fundamentally means that only 20% of the capital investment is being utilized. Financially speaking, this will lead to a higher cost of ownership and a slower return on investment. For the customer, it can cause longer lead times for their product and therefore the business will not be as competitive in the market place.

With production efficiencies at this level there will be many knock-on effects that will have an impact on the business such as larger batch sizes, more parts in stock, more assemblies in WIP (work in progress) and slower reaction times to customer change requirements.

With all this in mind there is a strong incentive to improve efficiency while maintaining quality.

SMT Assembly Capabilities

SMT Assembly Capabilities

  • Automatic surface mount assembly capabilities for accurate placement
  • Full layout capabilities to customer's print
  • Fine pitch and BGA placement capabilities
  • Manufacturing capabilities from prototype quantities through production volume
  • Wide range of base materials available including glass epoxy, ceramic, alumina (96% AL2O3), Aluminum nitrate (AIN), and flex
  • Assembled, inspected, and tested to MIL-STD and IPC specifications
  • Single or double-sided assemblies
  • Electrical and environmental testing available
  • Full turn key available
  • RoHs assembly available
  • Selection of conformal coatings available

What is the difference between SMT and SMD?


SMT stands for Surface Mount Technology, the entire technology of mounting and soldering surface mount components onto a printed circuit board or PCB. The actual process is summarised below:


Firstly, a PCB stencil is aligned on the surface of the boards and solder paste is applied using a squeegee to ensure the pads are coated with a uniform and controlled amount of solder paste.

Secondly, via a pick and place machine or hand placement, the components are mounted onto the boards in their respective locations. The wet solder paste will act as a temporary adhesive but it is still important to ensure that the boards are moved gently to prevent misalignment.

Thirdly, the boards are passed through a reflow oven which subjects the boards to infrared radiation, melting the solder paste and forming solder joints.

Then the boards are passed through an AOI machine, or Automatic Optic Inspection machine which runs a number of quality checks on the boards visually, such as component alignment and checking for solder bridges. The boards then proceed to further testing.

In the 1980s, SMT production technology became increasingly more refined and as a result, is widely used in mass production. As costs were reduced and technical performance enhanced, more advanced but economical equipment became available. Surface mount technology has numerous advantages, not limited to reducing the volume of devices, such as improved performance, greater functionality and lower costs. As such, SMT brought with it a new generation of electronic assembly technology, which is widely applied in applications from aviation, communications, automotive and medical electronics, down to household appliances and other fields.

What is SMD?

SMD is short for surface-mount device. It is an abbreviation for surface mount devices, a device assembled using surface mount components and technology.There is a wide range of SMD component packages available on the market and come in many shapes and sizes. In the early stages, SMD were soldered manually by hand. Then the first batch of pick and place machines could only handle a few simple components. The more complex and smaller components still needed to be placed manually.

Not long before the introduction of surface mount components over 20 years ago, a new era was born. From simple resistors to complex ICs, almost every through hole component now has an SMT equivalent.

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