Rigid Flex PCB is a type of circuit board that integrates both flexible and rigid sections. Its design differs significantly from that of purely flexible or rigid boards.
1. Design requirements for the flexible zone:
1) Employ tear shapes between thick and thin lines to prevent abrupt expansion or contraction.
2) Use rounded corners to avoid sharp angles.
2. When the electrical requirements are met, the pad size should be maximized. The transition line between the bonding pad and the conductor should avoid sharp angles and maintain a smooth curve. The independent bonding pad should include a pad toe to enhance support.
3. Dimensional stability: Maximize the use of copper in the design and incorporate as many solid copper areas as possible in the waste regions.
4. Design of covering film window:
1) Include manual alignment holes to improve alignment accuracy.
2) The window design should account for the range of glue flow. Generally, the window opening should be larger than initially designed, with the specific size provided by ME according to design standards.
3) For small and densely packed window openings, consider using special mold designs such as rotary punches or skip punches.
5. Design of rigid deflection transition zone:
1) Ensure a smooth transition of the line, with the line direction perpendicular to the bending direction.
2) Distribute the conductor evenly throughout the bending area.
3) Maximize the wire width across the entire bending area. Avoid using PTH design, Coverlay, and No Flow PP design in the transition area.
6. Design of flexible area with air gap requirements:
1) No through holes should be present in the bending area.
2) Protective copper wire should be added on up to two sides of the line. If space is insufficient, protective copper wire can be added to the inner R corner of the bending area.
3) Design the line connection as an arc.
4) Increase the bending area as much as possible without affecting assembly.
7. Other:
Avoid sharing tool holes on the flexible board, such as punch holes, ET, SMT positioning holes, etc.
FPCs are widely used in electronic products, but due to their low mechanical strength and susceptibility to cracking, they often require reinforcement to improve durability. The types of FPC reinforcement include:
1) PI reinforcement: Tolerance can be controlled within ±0.03mm, offering high precision and temperature resistance (130°C – 280°C). Available thicknesses: 0.075mm, 0.1mm, 0.125mm, 0.15mm, 0.175mm, 0.2mm, 0.225mm, 0.25mm.
2) Steel sheet reinforcement: Requires manual assembly, which is more complex and costly. Available thicknesses: 0.1mm, 0.2mm.
3) FR4 reinforcement: For thicknesses less than 0.1mm, tolerance can be controlled within ±0.05mm. For thicknesses greater than 1.0mm, tolerance is ±0.1mm. Available thicknesses: 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 1.6mm.
FPC flexible PCB reinforcement has its advantages and disadvantages. PI reinforcement offers minimal tolerance but is not very rigid. FR4 provides a thicker and more rigid choice but with larger tolerance variations. Steel sheet reinforcement is hard and stable but can be difficult to rework after manual assembly.
1. Design requirements for the flexible zone:
1) Employ tear shapes between thick and thin lines to prevent abrupt expansion or contraction.
2) Use rounded corners to avoid sharp angles.
2. When the electrical requirements are met, the pad size should be maximized. The transition line between the bonding pad and the conductor should avoid sharp angles and maintain a smooth curve. The independent bonding pad should include a pad toe to enhance support.
3. Dimensional stability: Maximize the use of copper in the design and incorporate as many solid copper areas as possible in the waste regions.
4. Design of covering film window:
1) Include manual alignment holes to improve alignment accuracy.
2) The window design should account for the range of glue flow. Generally, the window opening should be larger than initially designed, with the specific size provided by ME according to design standards.
3) For small and densely packed window openings, consider using special mold designs such as rotary punches or skip punches.
5. Design of rigid deflection transition zone:
1) Ensure a smooth transition of the line, with the line direction perpendicular to the bending direction.
2) Distribute the conductor evenly throughout the bending area.
3) Maximize the wire width across the entire bending area. Avoid using PTH design, Coverlay, and No Flow PP design in the transition area.
6. Design of flexible area with air gap requirements:
1) No through holes should be present in the bending area.
2) Protective copper wire should be added on up to two sides of the line. If space is insufficient, protective copper wire can be added to the inner R corner of the bending area.
3) Design the line connection as an arc.
4) Increase the bending area as much as possible without affecting assembly.
7. Other:
Avoid sharing tool holes on the flexible board, such as punch holes, ET, SMT positioning holes, etc.
FPCs are widely used in electronic products, but due to their low mechanical strength and susceptibility to cracking, they often require reinforcement to improve durability. The types of FPC reinforcement include:
1) PI reinforcement: Tolerance can be controlled within ±0.03mm, offering high precision and temperature resistance (130°C – 280°C). Available thicknesses: 0.075mm, 0.1mm, 0.125mm, 0.15mm, 0.175mm, 0.2mm, 0.225mm, 0.25mm.
2) Steel sheet reinforcement: Requires manual assembly, which is more complex and costly. Available thicknesses: 0.1mm, 0.2mm.
3) FR4 reinforcement: For thicknesses less than 0.1mm, tolerance can be controlled within ±0.05mm. For thicknesses greater than 1.0mm, tolerance is ±0.1mm. Available thicknesses: 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 1.6mm.
FPC flexible PCB reinforcement has its advantages and disadvantages. PI reinforcement offers minimal tolerance but is not very rigid. FR4 provides a thicker and more rigid choice but with larger tolerance variations. Steel sheet reinforcement is hard and stable but can be difficult to rework after manual assembly.
