Semi-flex PCBs

Overview of semi-flex technology

The semi-flex printed circuit board belongs to the 3D printed circuit board product group. This technology is suitable for double-sided and multilayer PCBs. The semiflexible design also offers significant cost advantages over classic rigid-flex PCBs and is ideally suited for static bending stress during assembly and installation.

Your advantages

  • Cost-effective 3D PCB technology
  • Printed circuit board samples produced in series quality
  • Increased reliability thanks to elimination of fragile connectors
  • Miniaturisation of assemblies
  • Reduction in processing steps for the further processing of assemblies
  • Cost savings and minimisation of errors through the replacement of plug and soldered connections
  • Optimised parts and logistics management
  • Reduced assembly and testing effort
Graphic of a semi-flex PCB stack

Cost-effective 3D PCB technology

Reduced assembly and testing effort

Miniaturisation of complex installation geometries

Detail view of a semiflexible printed circuit board

In addition to the appealing price and the good static bending load during assembly and installation, semi-flex PCBs are characterized by the following parameters:

  • Bending radius of at least 3 mm (semi-flex2 - rigid-flex technology) and at least 5 mm (semi-flex1 - deep-milled)
  • Maximum bending angle of 180°

The manufacturing process for a semi-flex PCB is simple and based on the production process of a standard rigid FR4 PCB. A flexible cover layer is then applied over the desired bending area, instead of the standard solder mask ink. At the end of the manufacturing process the area below this flexible cover layer is deep-milled. This means that the thickness of the PCB in the bending area is reduced until the material can be easily bent.

Comparison of 3D PCB technologies

Materials Polyimide / FR4
Number of layers 2-10
PCB thickness 0.6 – 3.2 mm
Final copper 18, 35, 70 µm
Conductor structures Depending on final copper according to design compass
Minimum drilling diameter 0.20 mm
Solder masks See general technical specifications
Surfaces See general technical specifications
Contour production Milling Scoring / breakaway tabs
Bending radii ≥ 5 mm
Bending angle ≤ 180°

The values specified represent the maximum performance spectrum andmay be restricted in certain combinations.

Solder resist masks 

  • Photosensitive solder mask systems
  • UV solder mask system: Screen printing
  • Colours: green, red, blue, glossy black, matt black, white, yellow, 
  • Flexlack: green

Surfaces

  • Chemical nickel/gold
  • Chemical tin
  • Electroplated nickel/gold
  • HAL or HAL lead-free 
  • OSP 
  • others on request

Additional printing  

  • Identification/assembly 
  • Hole filler/through hole filler 
  • Peelable solder mask  
  • Heatsink 
  • Carbon

Edge plating  

The end faces of the PCB contour can be plated in order to improve the EMC protection of a PCB, make electrical contact with the housing of the module or meet increased cleanliness requirements.

Edge plating

Milled plated through holes 

It is possible to produce application-specific components with so-called milled plated through holes. Due to the possibility of contact on the front side, the resulting PCBs can be soldered as components to another board (interposer).

Milled plated through holes

Contour machining

Contour production: milling and scoring

Asymmetrical with a Cu layer in the flex area (deep-milled) 

Graphic of an asymmetrical semi-flex PCB stack with one Cu layer

Asymmetrical with two Cu layers in the flex area (deep-milled) 

Graphic of an asymmetrical semi-flex PCB stack with two Cu layers

Asymmetrical with one Cu layer in the flex area (SF technology)

Grafik eines asymmetrischen Semiflex- Leiterplatten-Aufbaus mit zwei Cu-Lagen (SF-Technologie)

Contact partner

Georgi Georgiev
Project Engineer
Phone +49 3721 266-204
georgi.georgiev@ksg-pcb.com

Martin Leeb
Technical Order Processing
Phone +43 2985 2141-573
martin.leeb@ksg-pcb.com