Taking a Journey through the JLCPCB Factory: Witnessing Every Step of the PCB Manufacturing Process

The manufacturing process of printed circuit boards (PCBs) involves a series of intricate steps and advanced techniques. Companies like JLCPCB employ state-of-the-art technology and stringent quality control measures to ensure the production of high-quality PCBs.

In this article, Robert Feranec, a Slovak Hardware Design Engineer and founder of FEDEVEL Academy, takes us on a tour of the JLCPCB factory and explains each stage of the PCB manufacturing process, from cutting raw materials to assembling and shipping the boards.

By gaining a deeper understanding of this intricate process, you'll gain valuable insights into how to create high-quality PCBs.

The Initial Stages

At the beginning of the PCB manufacturing process, the raw material is cut into panels of standardized sizes. The edges of the panels are smoothed and rounded to ensure uniformity. The panels are then thoroughly cleaned to remove dust particles and other contaminants. This cleaning process is particularly important for four-layer PCB construction. Specialized clean rooms with controlled airflow are used to maintain a particle-free environment.

Next, a photosensitive film is applied to the raw PCB material. The film turns yellow and is placed on a holder before being exposed. Using UV light or a similar method, the PCB layout is exposed through the protective film, revealing the desired circuitry pattern. After exposure, the photosensitive layer is developed, making the circuitry visible through a glass window. The PCB is then etched to remove the copper not covered by the photosensitive film, leaving behind the desired copper pattern. The remaining photosensitive layer is stripped away, exposing the copper traces and pads.

Advanced Processes

Once the initial stages are complete, the PCB goes through a series of advanced processes. First, an automated optical inspection (AOI) is performed to scan the PCB for potential defects or issues. This helps identify any problems that need further inspection or repairs. The copper surface is treated to make it rougher, enhancing adhesion. Prepreg, an insulation material, is applied between layers to facilitate better bonding with the roughened copper surface.

Copper foil is then added to the top and bottom layers of the PCB, with prepreg between these copper layers. The PCBs are placed in an oven room for baking, which bonds the layers together. After baking, the large panels are cut into standard-sized panels, and each panel is given a unique identification (ID). An aluminum plate is placed on top of the PCB to assist in heat dissipation and improve drilling accuracy.

Drilling is a critical step in the PCB manufacturing process. Holes are drilled according to specifications using multiple drilling machines simultaneously. The drilled holes are then plated using electroless and electroplating processes to deposit copper and thicken the copper layer. Photosensitive film is applied to the top and bottom layers, and the PCB is flipped to expose the bottom layer for drawing tracks and circuitry on the photosensitive film. After development, a negative layer is created on the top and bottom layers to protect the vias and holes during etching. A thin layer of tin is applied to further protect the vias and holes.

Final Stages

The PCB manufacturing and PCB assembly process involves several crucial stages. After the PCBs are fabricated, the photosensitive layer is removed from the top and bottom layers, revealing the tin-covered copper traces. The tin layer is then removed, leaving behind the desired copper traces. An automated optical inspection (AOI) is performed to ensure the quality of the PCBs, verifying correct component placement. Optional electrical testing can also be conducted to verify functionality and detect any early issues.

Next, a solder mask color is applied to protect the copper traces while exposing the areas for component placement. The solder mask is exposed using UV light, creating openings for precise component placement. After exposure, the solder mask is developed to finalize the mask openings, and the PCBs are thoroughly washed for a clean surface. A silkscreen, featuring white text and symbols, is added to identify component placements and markings.

PCB Assembly

Moving on to the PCB assembly process, the PCBs are placed inside a box, holder, or feeder and transferred to a machine that applies solder paste. The PCBs then move to the assembly machine, where all the small components are accurately placed on the board in real-time. Larger components, such as the ESP32 module, are placed using a second machine.

Once the components are placed, the boards undergo an inspection process to verify correct component placement within the solder paste. The boards then enter an oven, where the solder paste is heated to securely attach all components. After the oven cycle, a manual check is performed to address any assembly issues that may have arisen. If the PCB includes through-hole components, additional steps, such as placement, cutting of leads, and bending if required, are undertaken.

Following the assembly process, wave soldering may be employed to enhance the soldering of through-hole components. Flux is applied, and the PCB is subjected to a wave soldering machine, soldering the components from the bottom. In some cases, a conformal coating may be applied to protect the board from water or humidity.

Finally, the PCBs are cleaned to remove any residues from the manufacturing process and undergo the necessary packing process for safe delivery to customers.

Conclusion

The journey through the JLCPCB factory offers valuable insights into the precise process of PCB manufacturing. From material cutting to final inspection, each step ensures the production of high-quality PCBs. Raw materials are cut into panels and cleaned before applying a photosensitive film for circuitry. Advanced processes like AOI and surface treatment address defects. Layer bonding, drilling, and plating ensure structural integrity, while solder mask and silkscreen layers protect traces. Thorough testing guarantees functionality and adherence to specifications.

JLCPCB utilizes advanced technology, stringent quality control, and a skilled workforce to produce reliable PCBs. Their commitment to continuous improvement and industry standards is evident throughout the manufacturing process. Witnessing this journey provides a deeper appreciation for the complexity involved in PCB manufacturing. JLCPCB's dedication to delivering high-quality PCBs solidifies their reputation as a trusted manufacturer.