Assembly Capabilities

**PCB Assembly Process at FeSS Technology Limited**  

At FeSS Technology Limited, we take pride in delivering efficient, high-quality turnkey PCB assembly services. Our commitment to excellence is reflected in our robust Quality Management systems and advanced process control strategies, ensuring every PCB order is executed flawlessly from the first attempt. To achieve the fastest turnaround times without compromising quality, we continuously refine our processes and optimize each step for maximum efficiency.

This article provides a comprehensive, step-by-step overview of our standard turnkey PCB assembly process, highlighting key stages that may be of particular interest to our clients. While this serves as a general guide, we invite you to explore our detailed DFM (Design for Manufacturing) and DFA (Design for Assembly) Guidelines for deeper insights into FeSS’s capabilities.

Understanding our assembly process is crucial for maximizing project efficiency. The number of steps involved varies depending on the project’s complexity, as illustrated in the flowchart below. Each stage is briefly explained in the following sections. For simplicity, some intermediate steps (e.g., individual inspections after each stage) are not shown. By familiarizing yourself with our process, you can design PCBs that streamline production, reduce costs, and accelerate delivery timelines.

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**DFM/DFA Verification**  

Upon receiving a turnkey order, our production team initiates a thorough DFM/DFA verification process. This includes cross-checking design documents (e.g., BoM, Gerber files, Centroid data), validating part spacing, footprint accuracy, and orientation markings. The goal is to minimize design-related errors, safeguarding our clients from costly rework and delays.

Within 24-48 hours of order submission, clients can expect an email from our production team. If any discrepancies are identified, our dedicated project coordinator will contact you directly with a detailed report and proposed solutions. Timely responses are essential to avoid workflow interruptions.

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**PCB Fabrication**  

After DFM/DFA approval, the order moves to the PCB fabrication stage. Here, bare PCBs are manufactured through processes such as material lamination, drilling, copper deposition, and etching. A solder paste stencil is also created during this phase. The boards are then coated with solder mask and surface finish, followed by silkscreen printing. Electrical testing is conducted against the client’s Netlist file to ensure 100% compliance with design specifications. Finally, tab routing or V-scoring defines the board profile for easy separation post-assembly.

While this is a simplified overview, PCB fabrication is a highly intricate process. For a detailed discussion of FeSS’s fabrication capabilities, please refer to our DFM Guidelines.

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**Incoming Material Inspection**  

Our Parts Procurement and Incoming Quality Control (IQC) teams work in tandem to ensure all materials are ready for assembly when the bare PCBs are completed. Upon arrival, components undergo rigorous inspection, including operational testing, date code verification, and entry into our advanced material management system. This system enforces strict FIFO (First-In-First-Out) protocols, ensuring only high-quality, traceable parts are used in assembly.

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**SMT Solder Paste Printing**  

The assembly process begins with solder paste application. A stainless-steel stencil, created during fabrication, is aligned over the bare PCB, exposing only the pads for surface-mount components. A precision applicator deposits solder paste onto the pads, followed by a thorough QC inspection to ensure proper coverage and alignment. For double-sided boards, this process is repeated for each side.

FeSS uses SAC305 solder paste, a lead-free alloy (96.5% tin, 3% silver, 0.5% copper) compliant with RoHS, REACH, and JEIDA standards.

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**Automated Component Placement**  

Post solder paste application, boards are transferred to our state-of-the-art Pick & Place machines. Using the Centroid file, components are placed with pinpoint accuracy. After placement, boards undergo another inspection to verify alignment before soldering.

For double-sided SMT boards, placement is performed separately for each side. Projects requiring wave soldering due to a high number of through-hole components also utilize automated placement.

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**Reflow Soldering**  

Reflow soldering is the industry standard for PCB assembly, offering greater flexibility in layout design compared to wave or manual soldering. At FeSS, we use nitrogen-assisted reflow ovens with closed-loop thermal control to achieve precise temperature profiles. For double-sided boards, an adhesive is applied to secure components during the second reflow cycle.

Our standard reflow profile:  

- Preheat: 60 seconds to 150°C  

- Soak: 120 seconds from 150°C to 165°C  

- Reflow: Peak temperature of 245°C for 20 seconds  

- Cooling: 4°C per second to room temperature  

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**X-Ray Inspection**  

Boards with BGA, QFN, or other leadless packages undergo X-Ray inspection. This non-destructive testing method provides detailed images of solder joints, enabling quantitative analysis and defect detection (e.g., insufficient paste, misalignment, or reflow issues).

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**Wave Soldering**  

While less common today, wave soldering remains essential for boards with high proportions of through-hole components or large connectors. FeSS’s process engineering team conducts a thorough design analysis before wave soldering to identify and address potential challenges.

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**Manual Soldering**  

For components unsuitable for reflow or wave soldering, FeSS employs a team of IPC-certified manual soldering specialists. They handle tasks such as through-hole connectors and delicate components, adhering to IPC-A-610 Class 3 standards.

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**Final Inspection**  

Every board undergoes a comprehensive final inspection, including visual checks and Automated Optical Inspection (AOI). Additional testing services, such as Functional Circuit Testing (FCT) and In-Circuit Testing (ICT), are available upon request.

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**Your Trusted PCB Assembly Partner**  

Since our founding, FeSS Technology Limited has been a leader in PCB assembly, serving clients across industries with precision and reliability. Our ISO-certified processes, combined with cutting-edge technology and a commitment to customer satisfaction, ensure your projects are executed to the highest standards. Contact us today to discuss your PCB assembly needs and experience the FeSS difference.

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