Introduction
The flexible printed circuit assembly is a meticulous and complex process that demands precision at every stage. From material preparation to quality inspection, each step plays a crucial role in ensuring the final product meets the highest standards. In this detailed guide, we will explore the essential processes involved in FPC manufacturing, highlighting the techniques that guarantee the quality and reliability of these vital components in modern electronic devices.
1. Material Preparation
The manufacturing process of Flexible Printed Circuits (FPC) begins with the preparation of materials. Key materials include flexible substrates, conductive materials, and insulating layers. These materials, often supplied in rolls, are first adjusted to the required width or slit into smaller sections using slitting or sheeting machines to match the dimensions needed for various products.
2. Punching and Drilling
Due to the flexible and low-yield strength nature of FPC materials, punching and drilling can lead to issues like burrs and material melting. To address this, manufacturers typically use high-precision mechanical drilling machines with effective chip removal capabilities, ensuring clean and accurate holes.
3. Desmearing and Copper Plating
For double-sided, multi-layer, or rigid-flex boards requiring metallization, a series of post-drilling processes are necessary. These include plasma treatment, chemical desmearing, electroless copper deposition, and electrolytic copper plating, which create a uniform metallic coating on the hole walls.
4. Image Transfer (Subtractive Process)
After metallization, the next step is image transfer. This process involves using dry film and exposure development to transfer the circuit pattern from a photo mask onto the flexible circuit board. The dry film is favored by most manufacturers due to its high tolerance for process variations and contaminants.
5. Etching and Stripping
Following image transfer, etching is performed to remove unwanted oxides and copper, creating the desired circuit patterns. Stripping involves removing the dry film used in image transfer with a stripping solution, followed by washing and drying the board to complete the process.
6. Application of Protective Film
Once etching and stripping are complete, a protective film is applied to safeguard the circuit board. This film is selectively applied to cover the required areas while leaving the assembly areas exposed.
7. Lamination
In the lamination stage, the prepared materials—reinforcement layers, cover films, circuit layers, and adhesives—are pre-stacked in a cleanroom environment. These layers are then bonded together under high temperature and pressure to form a cohesive unit.
8. Surface Treatment (Gold Plating)
After lamination, surface treatment such as nickel-gold plating is often performed to enhance the product's reliability. This treatment improves the FPC's resistance to acidic and alkaline environments and enhances its solderability.
9. Marking and Text Application
Text and symbol markings are silk-screened onto the board to facilitate subsequent identification and assembly of the product.
10. Electrical Testing
Upon completion of all processing steps, the flexible circuit board undergoes electrical testing using probes to detect any issues like open circuits or short circuits, ensuring the reliability of the product.
11. Auxiliary Material Assembly
After electrical testing, auxiliary materials such as adhesive tapes, steel sheets, and FP4 are attached to the circuit board using automated equipment, guided by optical alignment methods.
12. Forming Stage
In the final stage, the large working board is cut or laser ablated into the dimensions specified by the customer, using dies or laser tools.
13. Final Quality Inspection (FQC Check)
The finished FPCs are subjected to a comprehensive quality inspection according to customer requirements and industry standards. This step is critical in identifying and removing defective products, ensuring that only the highest quality FPCs reach the market.
Conclusion
The flexible printed circuit assembly process is intricate and demands attention to detail at every stage. From material preparation to final quality inspection, each step is crucial in ensuring the reliability and performance of the final product. The complexity and precision required in this process underscore the significance of FPCs in today's electronic devices. The Gekunflex brand remains committed to excellence, ensuring that every FPC we produce meets the highest industry standards.
