Flexible Printed Circuits (FPCs), also known as flexible circuit boards, differ significantly from rigid printed circuit boards in their PCBA assembly process. Due to their soft and pliable nature, FPCs require special handling during SMT (Surface Mount Technology) processes such as printing, placement, and reflow soldering. Without a suitable carrier board, it is challenging to secure and transport the FPC properly, making standard SMT operations difficult.
**1. FPC Pretreatment**
FPCs are typically not vacuum-sealed at the factory and are prone to absorbing moisture from the air during storage and transportation. Before SMT, they must be pre-baked to remove moisture gradually. If not done, the absorbed moisture can vaporize rapidly during reflow, causing delamination, blistering, or other defects. The typical pre-baking conditions are 4–8 hours at 80–100°C, with higher temperatures (up to 125°C) used only when necessary. It's essential to test the FPC first to ensure it can withstand the baking temperature. After baking, the FPC should show no discoloration, deformation, or lifting. It must pass IPQC sampling tests before being sent for SMT.
**2. Special Carrier Board Production**
To ensure proper alignment and stability during SMT, a custom carrier board is manufactured based on the FPC’s CAD file. This carrier board includes precise positioning holes that match the FPC’s design, ensuring flatness during printing and placement. Since FPCs may have varying thicknesses due to design or reinforcement, the carrier must be carefully processed and polished to maintain flatness. Common materials for carrier boards include synthetic stone, aluminum, silicone, and high-temperature resistant steel plates.
**3. SMT Process for FPC**
Using a standard carrier board, the FPC is fixed using either single-sided or double-sided tape. For better handling, some carriers use spring-loaded pins that allow the FPC to be placed directly without additional adhesives. The FPC must be fixed securely to avoid shifting during printing and placement.
**a. FPC Fixing**
The FPC is placed on the carrier board and secured using tape. Care must be taken to avoid warping or misalignment. Single-sided tape is often used for its ease of removal after reflow, while double-sided tape requires careful selection to prevent residue or damage.
**b. Solder Paste Printing**
Solder paste is applied using a polyurethane scraper (80–90 Shore hardness) to accommodate the uneven surface of the FPC. A precision optical system is recommended for accurate printing, as FPCs are not as flat as rigid PCBs. The station must remain clean to avoid contamination of gold fingers or plated buttons.
**c. Component Placement**
Components are placed using medium or high-speed placement machines. The FPC’s slight unevenness requires precise nozzle height and pressure settings. The machine should have BAD MARK identification to handle non-standard boards efficiently.
**d. Reflow Soldering**
A forced hot convection infrared reflow oven is preferred to ensure even heating and reduce defects. If single-sided tape is used, the FPC may deform during heating, leading to poor solder joints. Temperature curve testing is critical, with test samples placed on both sides of the carrier to simulate real production conditions.
**4. Inspection and Testing**
After reflow, the FPC is cooled using a fan to prevent thermal shock. Operators must wear insulated gloves when handling hot carriers. Visual inspection under a 5x magnifier checks for issues like residual glue, discoloration, or tin beads. AOI may not be reliable due to the uneven surface, so ICT or FCT tests are usually used instead.
**5. Sub-Board and Packaging**
If needed, FPCs are separated using a custom stamping die to avoid damage. Proper packaging with anti-static materials and spacing is crucial to prevent damage during transport.
**6. PCBA Production Equipment**
Key equipment for PCBA manufacturing includes solder paste printers, component placement machines, reflow ovens, AOI systems, wave soldering machines, and cleaning systems. Each plays a vital role in ensuring quality and efficiency throughout the production process.
**7. External Processing Requirements**
When outsourcing PCBA production, strict adherence to BOM (Bill of Materials), anti-static protocols, component orientation, soldering standards, and packaging guidelines is essential. All components must be handled with care to prevent static damage and ensure consistent quality.
By following these detailed procedures, manufacturers can achieve high-quality FPC assembly with minimal defects, ensuring reliable performance in flexible electronics applications.
Yuhai company develop and produce various plate & block sizes, electrode and metallisation configurations.This range is fabricated from 33 available Piezoelectric Material formulations for the applications of high power, sensitivity, stability needs.
Features
- Eectrode type on request
- Evaporated and chemically deposited metallisation's available
- Shear vibration plate available on request
- Thickness frequency tuning available on request
- Wide choice of PZT formulations.
Applications include
· • 1-3 Composites material available on request
· • Megasonic cleaning
· • NDT transducers
· • Pressure sensors
· • Ultrasonic sensors
• Linear ultrasonic motors
• Low frequency hydrophones
Yuhai's piezoelectric block has been utilized continuously in low frequency hydrophones in more than 30 years.
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Plates |
Length: 1-200mm |
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Width: 1-200mm |
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Thickness: 0.2-25mm |
Piezoelectric Plate,Piezo Plate,Pzt Plate,Piezo Ceramic Plate
Zibo Yuhai Electronic Ceramic Co., Ltd. , https://www.yhpiezo.com