XDCPCBA
                                                                                                                                       SMT assembly  

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XDCPCBA is a professional PCB assembly company. We provide PCB manufacturing and assembly services. Advanced testing equipment is our commitment to product quality.​​​​​​​

SMT assembly process

XDCPCBA
  • Solder Paste Printing
    Use a precision stencil and scraper to apply solder paste to the pads on the surface of the PCB. Solder paste is composed of solder and flux, which has fluidity and can melt and form solder joints when heated.
  • Component Placement
    Use a placement machine for automated placement of components, taking components from the tape and accurately placing them on the solder paste coating. The purpose is to accurately place surface mount components on the solder paste coating on the PCB.
  • Reflow Soldering
    The assembled PCB is sent to the reflow oven, where the temperature gradually rises, and the solder in the solder paste melts and forms a good solder connection with the pads of the PCB.
  • Reflow Oven
    Reflow oven usually has multiple temperature zones, including preheating zone, heating zone, soldering zone and cooling zone, the purpose of which is to melt the solder paste, form solder joints, and firmly connect components to PCB.
  • Inspection

    Automated Optical Inspection (AOI)：Automated optical inspection equipment is used to inspect welding quality, identify whether the solder joints are good and whether the components are placed correctly. Ensure that all components are soldered correctly and check for defects

  • X-ray inspection
    For components that are difficult to observe directly, such as BGA (ball grid array), X-rays are used to check the welding conditions. Combined with manual inspection, it ensures that there are no problems such as missing solder joints and wrong solder joints.
  • Electrical Testing

    ICT (In-Circuit Testing): Apply test signals to the circuit board to detect the connection and function of components. FCT (Functional Testing): Test the overall function of the PCB by simulating the actual working state.

  • Final Assembly & Packaging
    If necessary, manual insertion (for through-hole components), coating (such as waterproof protective coating) or packaging (such as sealed packaging) can also be performed. Qualified PCBs are packaged and prepared for final processing and shipment.

Advantages of PCB SMT Process

Advantages of XDCPCBA SMT assembly service

High precision and high reliability
Advanced patch and welding equipment ensures high-precision assembly, suitable for complex electronic products.
Strict quality control system ensures product stability and reliability.

Fast delivery
The optimized production process and automated equipment are used to significantly shorten the production cycle and meet customers' requirements for fast delivery.

All-round support
Provide a complete solution from PCB manufacturing, component procurement, SMT assembly to testing to simplify customer supply chain management.
The engineering team provides technical support at any time to quickly solve problems in design and manufacturing.

Flexibility and customization
XDCPCBA can provide suitable solutions for both small batches of complex customization requirements and large batches of efficient production.

Cost optimization
Provide cost-effective assembly services to help customers reduce overall costs by optimizing material utilization and process flow.

Application Areas

Consumer Electronics
PCBA application in consumer electronics
medical field
PCBA application in the medical field
物联网IOT
PCBA application in the field of Internet of Things
Automotive electronics
PCBA application in automotive electronics
Communication equipment
PCBA is used in communication equipment
Instruments and meters
PCBA is used in instruments and meters

SMT Assembly FAQ

  • What is the production cycle of SMT assembly and how to optimize it?

    Answer: The production cycle depends on the order size, design complexity and material supply. Prototype production generally takes 3-7 days, and mass production may take 2-4 weeks.
    Optimization methods:
    1. Simplify BOM: Reduce the number of component types and reduce the complexity of material management during the design phase.
    2. Prepare materials in advance: Ensure timely supply of key components to avoid production delays due to material shortages.
    3. Parallel operations: Separate and perform PCB manufacturing, solder paste printing, patch and welding processes simultaneously.
    4. Equipment maintenance: Regularly calibrate patch machines and reflow equipment to reduce downtime.
    5. DFM analysis: Conduct manufacturing feasibility assessment during the design phase and optimize the design to reduce production problems.

  • What are the requirements for PCB design for SMT assembly?

    Answer: PCB design directly affects the efficiency and quality of SMT assembly. The following factors should be considered in the design:
    1. Pad design: Ensure that the pad size and component pins are fully matched to avoid soldering defects caused by too large or too small.
    2. Spacing: High-density design requires sufficient component spacing to avoid bridging.
    3. Fiducial Marks: Add reference points on the PCB to facilitate the alignment of the placement machine.
    4. Thermal design: Especially for QFN and BGA, heat dissipation pads or thermal conductive vias need to be designed.
    5. Electrical test points: Leave test points in the PCB design for subsequent ICT testing and functional testing.

  • How to avoid common defects such as cold solder joints and offsets in SMT assembly?

    answer: Common defects and solutions
    1. Cold solder joints: The solder joints are not fully formed, which may be due to insufficient solder paste or insufficient reflow soldering temperature.
    Solution: Optimize the amount of solder paste and temperature curve to ensure that the solder joints are fully formed.
     
    2. Component offset: The mounting position deviation may be caused by insufficient precision of the placement machine or PCB vibration.
    Solution: Regularly calibrate the placement machine and use a placement head with appropriate adsorption force.
     
    3. Bridging (short circuit): Excessive solder paste or improper pad design may cause short circuits between pins.
    Solution: Optimize the solder paste printing process and increase the pin spacing (if the design allows).
     
    4. Solder joint cracks: Solder joints cool too fast or solder quality is poor.
    Solution: Optimize the reflow cooling stage and select high-quality solder.

  • What are BGA, QFN, QFP and other packages, and what are the special requirements for their SMT assembly?

    Answer: 1. BGA (Ball Grid Array): The pins are distributed at the bottom of the component in a spherical form, which is suitable for high-density connection. X-Ray inspection equipment is required to check invisible solder joints.
     
    2. QFN (Quad Flat No-lead): Pinless package, the soldering point is at the bottom edge of the component, and the heat dissipation performance is better. Special attention should be paid to pad design and thermal welding.
     
    3. QFP (Quad Flat Package): A flat package with pins on four sides, suitable for medium-density applications, and requires high welding accuracy.
    Special requirements:
    Accurate solder paste printing and mounting position control.
    Appropriate reflow soldering temperature curve to ensure solder joint quality.
    Ensure that the pad layout and component pins match during the design phase.

  • What is PCB SMT assembly, and how is it different from traditional THT (through-hole assembly)?

    Answer: PCB SMT assembly (Surface Mount Technology) is a miniaturized and efficient assembly technology that directly mounts components on the surface of a PCB.
     
    SMT features: Components do not need pins to pass through the PCB, they only need to be mounted on the surface and fixed by reflow soldering. Suitable for miniaturization and high-density circuits.
    THT features: The pins of the components need to pass through the PCB and be soldered on the other side, which is more suitable for scenarios with large-size components and high mechanical strength requirements.
    Compared with THT, SMT has higher assembly efficiency, smaller footprint and lower cost, but has higher requirements for component size and design accuracy.
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