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Flex PCB Parameters refer to the key specifications that define the design, performance, and manufacturing requirements of flexible printed circuit boards (Flex PCBs). These parameters ensure the board meets mechanical, electrical, and environmental demands.
What the Key Parameters of Flex PCB?
1 Material Type:
- Common base materials: Polyimide (most popular for flexibility and heat resistance), PET, or PEN.
- Adhesive vs. adhesiveless constructions (affects thickness and flexibility).
2 Layer Count:
The layer count is typically established during the design phase, enabling direct selection of the required layers according to your specific design requirements.
- Single-layer, double-layer, or multi-layer configurations.
3 Board Thickness:
Total thickness (including substrate, copper, coverlay, etc.), typically ranging from 0.1 mm to 0.3 mm.
- Copper thickness choices for single-sided boards: 18µm (0.5 oz) and 35µm (1 oz).
- Copper thickness choices for double-sided boards: 12um (0.33oz), 18um (0.5oz), 35um (1oz)
4 Minimum Trace Width and Spacing
Narrower trace widths and spacing correspond to increased manufacturing complexity. Standard guidelines advise using 3/3 mil (0.003″) or larger dimensions. While M2PCB’s technical capability extends to approximately 2/2 mil, and strongly recommend designers refrain from approaching this threshold in their layouts.
5 Minimum Via and Pad
The via’s annular ring (outer diameter) should exceed the inner diameter by a minimum of 0.2mm, though it’s recommended to maintain a clearance of 0.25mm or greater.
From a manufacturing perspective, smaller vias tend to increase production costs. Standard recommended dimensions are: 0.3mm drill hole (inner diameter) with 0.55mm finished outer diameter.
6 Coverlay/Overlay:
FPC solder masks are available in yellow, black, and white. Yellow is the recommended option, as it serves as a versatile choice for general applications, including most flexible ribbon cables. Black variants are typically employed in premium applications or scenarios requiring light-blocking properties, such as automotive electronics, smartphones, and LED display panels.
White solder masks feature an extra white coating layer and are primarily utilized in reflective environments, such as lighting systems, LED backlit displays, and medical/aesthetic devices.
7 Solder Mask Layer
Flexible printed circuits (FPCs) employ a coverlay as their solder resist layer, with two primary via treatment methods:
- Via Opening: Exposing the via barrel for electrical testing or post-assembly modifications.
- Via Tenting: Fully encapsulating vias to prevent contamination and improve mechanical stability.
8 The Minimum Solder Mask Bridge Width
A minimum solder mask bridge width of 0.5mm must be maintained between conductive features. This requires a minimum pad-to-pad clearance of ≥0.5mm to preserve mask integrity.
9 Stiffeners:
When making flexible circuits, we use five key strengthening materials you’ll typically see:
Heat-resistant plastic film (PI), commonly for gold finger products.
FR4 is mostly to keep FPCs from moving around while do assembly.
Metal plates are ideal for attaching chips. Heads up though: the steel’s tiny magnetic pull can interfere with sensitive stuff like Hall sensors, so maybe avoid it for those cases.
3M Strong double-sided sticky tape.
Electromagnetic shielding film, keeps signals clean.
10 Flex pcb Array
Fabrication panels must not exceed 240mm x 600mm in dimensions. If you need a larger size, please negotiate with us for production.
Getting your FPC specs right is critical for balancing performance, durability, and cost. Start by choosing materials that match your needs – heat-resistant polyimide (PI) for high-stress environments or budget-friendly PET for simple bends. Keep thickness in check: too thin risks tearing, too thick limits flexibility. Always respect the bend radius to avoid cracks during installation. Whether it’s a foldable phone surviving daily flips or a pacemaker flexing with heartbeats, the right specs keep your FPC reliable without breaking the bank.
