A flex circuit must fit its electrical route and its installed shape. Review the flexible stackup, copper, protective layers, stiffeners and bend zones together, and identify whether the circuit is formed once or moves in service.
Read each value together with its board type and review conditions.
Published limits apply to their stated board type. Layer count, copper weight and minimum geometry require a combined engineering review.
These values apply to flex PCB and do not inherit the rigid-board copper or layer limits.
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| Parameter | Published capability | Applies to | Review conditions |
|---|---|---|---|
| Maximum layers | 8L | Flex construction | Layer arrangement and intended bending behavior |
| Board thickness | 0.1–0.5mm | Flexible construction | Define the flex thickness separately from stiffened locations |
| Inner / outer finished copper | 2oz / 2oz | Flex copper layers | Copper type, geometry and bend zone |
| Inner trace / space | 3/3mil | Inner flex pattern | Copper thickness and local density |
| Outer trace / space | 3.5/4mil | Outer flex pattern | Copper, protective layer and pad openings |
| Mechanical / laser drilling | 0.1mm / 0.1mm | Respective flex drilling processes | Hole type, processed depth and layer span |
| Mechanical aspect ratio | 10:1 | Flex mechanical drilling | Confirm actual diameter and processed thickness |
Show the finished circuit outline and all stiffened regions on the same controlled drawing.
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| Parameter | Published capability | Applies to | Review conditions |
|---|---|---|---|
| Process panel | 500 × 1200mm | Flex process panel | Manufacturing margins and material format |
| Finished board range | 5 × 10mm minimum; 9.8 × 19.8inch maximum | Individual flex outline | Handling, panelization and protection |
| Contour tolerance | ±0.05mm | Flex outline | Datum scheme and critical connector features |
| Protection entries | Green solder mask; black, yellow and white PI | Options listed for flex | Confirm protective construction, openings and adhesive details |
| Mask clearance / dam | 3mil / 8mil | Flex solder mask | Check the selected mask or PI construction separately |
| Legend width / height | 4mil / 23mil | Flex legend | Color, protected area and readability |
The sheet gives thickness-based design references. They are inputs to review, not a fatigue-life guarantee or an automatic approval for every stackup.
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| Parameter | Published capability | Applies to | Review conditions |
|---|---|---|---|
| Single-sided reference radius | 3–6 × board thickness | Flex reference construction | Copper, protection, bend direction and installed geometry |
| Double-sided reference radius | 6–10 × board thickness | Flex reference construction | Layer arrangement and bend-zone features |
| Multilayer reference radius | 10–15 × board thickness | Flex multilayer reference | Layer count and any bonded/unbonded regions |
| Dynamic bending reference radius | 20–40 × board thickness | Motion in service | Required cycle life, stroke, speed and environment must be supplied |
| Strain fillet width | 1.5 ±0.5mm | Flex transition detail | Confirm the actual transition and drawing requirement |
A flat fabrication file cannot fully communicate the installed circuit.
These examples describe individual structures in our project reference material. They do not establish a general maximum or guarantee the same combination for a new design.
The project reference records 8-layer flex, 3/3.5mil, 0.8mm and green flex solder mask. The 0.8mm entry is specific to that recorded structure; it does not replace the general 0.1–0.5mm range or establish bend performance.
Individual engineering example; the combination is reviewed for each project.
Describe the mechanical function as carefully as the net routing.
Send fabrication data, the flex stackup, copper requirements, finished outline, protective-layer openings and stiffener drawings. Include the installed shape and separate static forming from repeated motion.
For controlled impedance, supply the target, nets, reference layer and acceptance requirement. The flex table lists single-ended and differential tolerance as ±5Ω at targets ≤50Ω and ±10% above 50Ω; the agreed stackup and test method still need review.
Include the drawing revision and acceptance requirements. The engineering review confirms the manufacturable combination before quotation.
Layer count alone does not define motion capability. Provide the flexible thickness, construction, bend radius and required motion duty for review.
Specify the flexible construction and each local stiffener separately. A finished thickness at a connector cannot be assumed to describe the moving flex area.
That thickness belongs to the documented example. It is not a revision of the general 0.1–0.5mm flex range, and a similar construction needs individual review.
Add the motion and installation drawing, bend radius, direction and required duty to the fabrication package, stackup and stiffener definition.