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Unlock Expert FPC Design Techniques with These Critical Guidelines! Explore professional strategies for outline planning, precision drilling, circuit optimization, and solder mask implementation to produce durable, high-performance flexible circuitry.
Dive into fundamental Flexible Printed Circuit design principles in Part 1 of our technical series. Discover key engineering considerations for developing compact, cost-efficient FPCs with enhanced reliability – essential knowledge for modern electronics designers.
Outline and Drilling Specifications
1 Maintain a minimum clearance of 0.5mm between through-holes and the board edge. For spacing below this threshold, replace standard holes with U-shaped slots (integrating the aperture into the panel outline).
2 Via-to-Solder Mask Clearance Requirements. Maintain a minimum 0.2mm clearance between vias and solder mask apertures. Insufficient spacing risks copper exposure at via barrels during fabrication.
3 Via-in-pad configurations must be avoided in Flexible Printed Circuits (FPCs) due to incompatibility with resin-free fabrication. The absence of resin plugging capability in FPC substrates creates unsealed conductive pathways, increasing risks of solder wicking and joint contamination during reflow processes.
Circuit Design Guidelines
1 Solid Copper Oxidation Mitigation: Continuous copper planes in FPC designs risk oxidation from entrapped air during thermocompression lamination. Prevent this by using copper grids or adding solder mask openings on large copper areas.
2 Avoid isolated pads: Dual-side overlapping pads on 25μm FPC cores risk delamination. Add copper anchors at pad corners and stagger upper/lower pads to strengthen adhesion.
3 Connector pads risk delamination. Implement pressure pad designs.
4 Avoid large exposed copper zones to prevent lamination wrinkles.
5 FPC employs coverlay as solder mask. Pre-die-cut coverlay before lamination. Maintain 0.2mm pad-trace clearance. Solder mask bridges ≥0.5mm width. For <0.5mm pad spacing, M2PCB defaults to trace exposure.
6 Low-density flex traces risk corner tearing; add edge tear-stop bars or rear copper mesh.
7 Use 45° copper grids for signal integrity. Standard trace/space: 0.2mm/0.2mm.
What should be paid attention to when designing FPC?
1 Plated contacts: Laser cutting induces carbonization, risking micro-shorts. Inset contacts 0.2mm.
2 Soldered contacts: Avoid linear via arrays near pads to prevent stress fractures.
3 Coverlay alignment: Offset solder openings ≥0.3mm from contacts to prevent fractures.
4 Solder mask overlap: Extend contacts 0.3mm beyond pads for compression bonding.
5 Mask relief design: Maintain 0.3mm mask overhang at contacts for trace integrity.
6 Non-hollow boards: Reverse contacts require transition vias and auxiliary pads.
7 Coverlay limitations: Avoid copper fills under IC pads – causes mask spread and reflow shorts.
8 Contact isolation: Keep plated contacts electrically isolated to prevent unintended copper exposure.
9 Tolerance specs: Default ±0.1mm. ±0.05mm requires order specification.
