What is Surface Mount (SMT) Assembly?

SMT is Surface Mount Technology, which is widely used for PCB Assembly. We are an experienced Surface Mount (SMT) Assembly Supplier, providing Turnkey PCB Assembly Services all over the world. We take pride in the High Quality PCB Assembly we build relied on a productions capacity of assembling over 25K SMDs per hour on the 8 high-precision SMT lines.

Our SMT electronics manufacturing service supports single and double sided assembly, and covers the complete spectrum of packages, including QFB, BGA, ?GBA, GBDA, CSP, Flip-Chip and 01005. We work with SMT Prototype PCB Assembly, Low Volume Assembly and High-Volume Assembly using the combination procedures of manual, automated THT and SMT assembly. Our technicians are highly trained PCB assembly experts who are committed to providing total customer satisfaction during each step of the production process. Work with our PCB assembly services, you can focus on your schematic and layout designs while we ensure your PCB boards are fabricated and assembled according to your design specifications.

In order to detect the joint soldering SMT quality, we employ a variety of verification and inspection methods, including repeated Visual Inspections, AOI (Automated Optical Inspection), 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.

SMT Soldering and Electronics Manufacturing Assembly

Electronics Manufacturing using surface-mount technology (SMT) simply means that electronic components are assembled with automated pick-and-place machines that place components on to the surface of a board (printed circuit board). SMT electronic assembly encompasses not only placing and soldering components to the PCB, but also the following main production steps:

  • Solder Paste PrintingApplying soldering paste, is one of the first steps in the SMT assembly process, and printed onto the pads with automated solder paste printer through a laser-cut SMT Stencil.
  • 3D SPI (Solder Paste Inspection)After solder paste printing, we need to inspect the solder paste joints quality. With 3D SPI machine, the 500MP CCD camera can take 3D pictures, which are used for defecting solder paste joints errors.
  • Component Placement and AssemblyThe electronic components packaged in trays, reels and tapes are uploaded to the feeders, then loaded into the SMT machine. Then the SMT machines pick the components from the feeders, and place them to related pads upon the CCD camera finding and checking the pre-programmed X,Y coordinates.
  • Component Reflow SolderingWhen components placement process completes, the PCBs bonded with unsoldered components will go through the well pre-profiling reflow oven for the components soldering. The PCBs with component soldered will be cooled at the end of the oven.
  • Visual & AOI InspectionVisual and AOI Inspection will be performed for the PCB assemblies after the reflow soldering for ensuring the PCB assembly quality, or to catch and correct a mistake.
  • 3D X-ray Inspection3D X-ray inspection will be performed to detect the position and size /shape of expected features for process optimization or presence /absence of unexpected /unintended objects or features for anomaly detection.

SMT Process

SMT Process Lead Free Assembly

Lead Free Assembly

Is your product lead-free (Pb-free)?
It should be.

And your lead-free product should be assembled in the factory of the Lead-free assembly manufacturer which has a comprehensive lead-free solder solution in every aspect of lead-free solder, including solder alloy selection, solder paste (Tin) evaluation, wave solder flux evaluation, process optimization, components evaluation, reliability, equipment evaluation, quality inspection and production costs.

We are the lead-free PCB assembly manufacturer and supplier. Forward your turnkey PCB assembly project to us, we give quick quote and manufacture the PCB assemblies with RoHS compliant.

Our Lead-Free Services

  • Lead Free Printed Circuit Boards
  • Lead Free SMT Assembly
  • Lead Free DIP Assembly
  • Lead Free Solder Paste
  • Lead Free Reflow Soldering
  • Lead Free Wave Soldering
  • Lead Free Materials

Our lead-free PCB assembly service uses special assembly procedures to assure compliance with Lead-free and RoHS directives. As a part of Lead-free assembly service, we

(1) provide support to you the transition of RoHS compliant printed circuit boards;

(2) assist to determine if the materials in your BOM meet lead free PCB manufacturing requirements;

(3) search lead-free electronic components for you and send you a BOM with appropriate components.

RoHS Compliance and Declaration

RoHS compliance means acting in full accordance with RoHS regulations. We declare and certify that all components and all homogeneous subcomponents manufactured by us are in compliance with the directive 2011/65/EC of the European Parliament and of the council of 8 June, 2011 on the restriction of the use of certain hazardous substances in electrical and electronic equipment (RoHS Directive), amended by Directive (EU) 2015/863. At the same time, we think the PCB assemblies manufactured by us are also compliant with China standards of the Administration on the Control of the Pollution caused by Electronic Information Products.

SMT Process Reflow Soldering

Reflow Soldering

  • 13 Temperature Control Zones
  • Maximum Board Size: 508mm x 610mm (20’’x24’’)
  • Minimum/Maximum Board Width: 50mm (2’’) / 457mm (18’’)
  • Heated Tunnel Length: 3556mm (140’’)’’
  • Accuracy of Temperature Control: +/-0.1°C
  • Cross-Belt Temperature Tolerance: +/-3.0°C
  • Temperature Range Standard: 25-350°C
  • Numbers of Cooling Zones Standard: 3

Reflow consists of a few individual processes, which are required to ensure that the PCB boards are brought up to the correct temperature for reflow soldering without applying any unacceptable levels of thermal shock. Only with correct profiling the temperature of the reflow tunnel or chamber, we then move the PCBs to the oven to ensure that the resulting solder paste are of the highest quality. The 4 stages normally used are as following:

Preheat: The PCB boards need to be brought steadily up to the required temperature. If the rate is too high, then the PCB boards or the components may be damaged by the thermal stress. Additionally, if the printed circuit board is brought to temperature too slowly then the PCB boards may not reach the required temperature, which will result that some components will be cool soldering. The temperature rise rate that is often used for infra-red reflow soldering is between 2 and 3°C per second, although rise down to 1°C per second may be used on some PCB assembly projects.

Thermal Soak: Having brought the PCB boards up to temperature it next enters what is often termed a thermal soak area. Here the card is maintained at temperature for 2 reasons. One is to ensure that any areas that are not adequately heated because of shadowing effects come up to the required temperature. The other is to remove the solder paste solvents or volatiles and to activate the flux.

Reflow: The reflow area is the area of the soldering process where the highest temperature is reached. It is here that the solder is caused to melt and create the required solder joints. The actual reflow process involves the flux reducing the surface tension at the junction of the metals to accomplish metallurgical bonding, allowing the individual solder paste spheres to combine and melt.

Cooling: The cooling for the PCB boards after reflow must be accomplished in a way that does not cause stress to the components. Proper cooling inhibits excess intermetallic formation or thermal shock to the components. Typical temperatures in the cooling zone range from 30-100°C. The temperature in this zone creates a relatively fast cooling rate and this is chosen to create a find grain structure in the solder to provide the most mechanically sound joint.

SMT Process Solder Paste Printing

Solder Paste Printing

One of the most important parts of the surface mount (SMT) assembly process is the application of solder paste onto the printed circuit board (PCB). The aim of solder paste printing is to accurate deposit the correct amount onto pads to be soldered. This is achieved by screen-printing the solder paste through a SMT Stencil. It is widely believed that this part of the process, if not controlled correctly, accounts for the majority of assembly defects. It is said that 60% to 90% of soldering defects are related to solder paste printing defects.

For becoming a leading turkey PCB manufacturing and assembly supplier, and for forming high quality solder paste, our PCB Assembly facility is equipped with Automated Solder Paste Printer (MPM® Momentum® Elite) from USA to fulfill the assembly manufacturing capabilities. The Elite is the top-performer of the Momentum series, boasting the highest throughput and shortest cycle times of all. Tighter performance tolerances mean higher repeatability with fewer defects. The Auto solder paste printer has the following features:

  • Applicable for all kinds of fine pitch ICs.
  • Solder paste height monitor
  • Alignment repeatability: ±12.5µm @ 6sigma, Cpk >2.
  • Printing precision: +/-20?m
  • Minimum Board Size: 50.8mm x 50.8mm (2’’x2’’)
  • Maximum Board Size: 609.6mm x 508mm (24’’x20’’)
  • Board Thickness: 0.2mm (0.008”) to 5.0mm (0.20”), up to 6.0 mm (0.24”) without top clamp foils.

* A dedicated work holder is required for boards with an X size greater than 20”.

Solder paste printed deposits are essential to forming defect-free solder joints, the electrical and physical connections between electronic components and the PCB assembly. The key parameters of an effective solder paste printing process of automated printing are as following:

  • Squeegee speed
  • Squeegee pressure
  • SMT Stencil separation speed
  • SMT Stencil cleaning
  • SMT Stencil and squeegee condition
  • PCB support strength
  • Print stroke
  • Type, storage and handling
  • Inspection

The printing stage of the assembly process is vitally important. If there are errors introduced at this stage there will be “knock on” effects throughout the process. But don’t worry, in our longstanding processing, our experienced technicians can handle the printing process perfectly, which can ensure the solder paste printing with high quality.


When it comes to PCB assembly, we import and use state-of-art equipment that allows the exact precision necessary for the entire assembly process, including solder paste printing, SPI (solder paste inspection), pick-and-place, AOI, X-ray, FAI (functional testing), FAI (first article inspection) and more. We provide a complete printed circuit board manufacturing and assembly services from free DFM of PCB design file to functional testing. Rely on us for the entire PCB manufacturing and assembly process. Our reliability is the best in electrical and electronic manufacturing industry, and our customer service is renowned in the fields, ranging from Medical, Automotive, Telecommunication, Semiconductor, UAV and Robotics.

2 SMT Assembly Lines

Equipment Name Model Component types Quantity
SMT JAPANYSM10+YSM10 SMT 01005 or larger .BGA 0.35mm pitch.pop(package on package). WLCSP 0.35mm pitch. Hard metric connectors Cabie & wire   line1
SMT JAPANYSM20R+YSM10(Line2) line2
Reflow Oven USA BTU10   1

Other Main Equipment

Equipment Model Quantity
 X-ray Fluorescence Spectrometer EDX 1800B (Skyray) 1 set
 2D X-Ray x|aminer (Phoenix) 1 set
SMT First Article Inspection FAI-600 1 set
BGA Rework Station 1 set

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PCB Assembly Requirement

No. Types Of Assembly File Format Component Footprint Component Package Testing Procedures Procedures Others
1 SMT ASSEMBLY Gerber RS-274X 0201,0402,0603... Reels Package Visual Inspection Lead-Free(Rohs) Custom Reflow Profile
2 SMT & THT Assembly BOM(.xls,.csv,.xlsx) BGA,QFN,QFP,PLCC Cut Tape Package X-Ray Inspection Leaded Solder Standard Reflow Profile
3 2 sided STM,THT Assembly Pick-N-Place/XY file SOIC,POP...Connectors Tube and Tray AOI,ICT(In-Circuit Test) Reflow Soldering Smallest Size:0.2"x0.2"
4 Mixed Assembly -- Small Pitch of 8 Mils Loose parts and bulk Functional Testing Wave Soldering Largest Size:15"x"20

PCB Assembly Applications

PCB Assembly Applications involve industrial

Applications involve industrial

PCB Assembly Applications New energy

New energy

PCB Assembly Applications Network and Computer

Network & Computer

PCB Assembly Applications Biomedical


PCB Assembly Applications Consumer electronics

Consumer electronics

PCB Assembly Applications Aerospace


PCB Assembly Applications Automotive


PCB Assembly Applications Telecommunications