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Flex and Rigid-Flex PCBs

PCBs with the ultimate versatility

A Flex PCB will have flexibility over the entire circuit. A Rigid-Flex circuit will consist of one or more rigid PCBs each connected by a Flex. Designers will often consider this technology when the have a limited space to house the circuits. Flex and Rigid-Flex can fit a product rather than the size of the product having to be designed to fit the circuits.

The main advantages include:

  • High product reliability
    Polyimide is the main substrate used and it aids the thermal stability of the circuits. A Rigid-Flex will not need traditional PCB connectors added at assembly to link boards. This will reduce assembly errors and remove and possibility of failure from the connectors themselves.
  • Reduced packaging space
    3D packing geometry often means rigid PCBs boards will not fit. The ability of thin Flex Circuits to bend and fold means they can be made to fit in the smallest of available spaces.
  • Weight reduction
    Rigid FR4 boards with conventional connectors can be too heavy for many applications; for instance, a wearable item or a product that needs to be carried. For these applications a Flex made from Polyimides will offer substantial weight saving.
  • Lower product costs
    These boards will fit in small packaging spaces making overall product costs lower. Less connectors also reduce costs as does a lower assembly time at box build.
  • Shock and vibration resistant
    The flexibility of these boards makes them very shock resistant and therefore ideal for high-stress environments.
  • Repeated Flex - Dynamic Flex Flex
    A standard Polyimide Flex is designed to flex at install and servicing. When a board needs to be repeatedly flexed such as in a robot, printer, or laptop a ‘Dynamic Flex’ option can be specified.
Rigid Flex PCB Animation
Flex (FPC) PCBs

Flex PCBs (FCB)(FPC)

Flex (FPC) PCBs
Flex (FPC) PCBs
Flexible Printed Circuit PCBs

Engineers will often call a Flex circuit different things. Terms such as Flexible Printed Circuits, Flex PCBs, Flex Circuits, FPC (Flexible Printed Circuit) are used. The copper conductor circuit is encapsulated by a thin insulating Polyimide film. One of the advantages of Polyimides is they have high temperature resistance which can aid assembly and the final product environment. Flex circuits can be constructed as single sided, double sided or multi-layered and manufactured as a connector or designed for use with components. Rigid stiffeners can be included.

Flexible Printed Circuit (FPC) - Capabilities
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Item Sample (Order Area <3m2) Batch (Order Area ≥3m2)
Main Materials    
Insulation Layer CVL, Ink CVL, Ink
Colour of coverlay Yellow, Black, White Yellow, Black, White
Colour of ink Yellow, Green Yellow, Green
Dielectric layer 0.012mm-0.1mm 0.025-0.1mm
Additional Materials    
FR-4 Stiffener 0.1-3.2mm 0.1-3.2mm
PI Stiffener 0.075-0.225mm 0.075-0.225mm
Steel reinforcement 0.2-0.6mm 0.2-0.4mm
Other Materials 3M tape, snap dome, electromagnetic shielding, lid-off film, micro-sticking film 3M tape, snap dome, electromagnetic shielding, lid-off film, micro-sticking film
     
Structure 1+n+1 ; 1+1+n+1+1 ; 2+n+2 (needs review) 1+n+1 ; 1+1+n+1+1 ; 2+n+2 (needs review)
F+R (needs review), cu+F+cu (needs review), R+F+R+F+R (needs review), R+F+R R+F+R
Layers ≤14L ≤8L
Board Thickness 0.06-0.35mm 0.1-0.35mm
Tolerance of Board Thickness Flexible Area 0.03mm;PI Stiffener Area 0.05mm;FR-4 Stiffener Area 0.1mm Flexible Area 0.03mm;PI Stiffener Area 0.05mm;FR-4 Stiffener Area 0.1mm
Min single unit Size PCB Size: 5mm*15mm-310mm*510mm PCB Size:5mm*15mm-310mm*510mm
Copper Thickness Outer layer 2oz, Inner layer 2oz Outer layer 1oz, Inner layer 1oz
Outline Breakaway Tab, Single PCB Breakaway Tab, Single PCB
Surface Treatment HASL, HASL lead free (single-side FPC only), ENIG, OSP (no-stiffener only) ENIG

Rigid Flex

Rigid Flex
Rigid Flex Hybrid Board
Flex Board and Rigid Circuit

A Rigid-Flex PCB consists of a Flex board connected to a Rigid PCB. They are hybrid circuits and can be a Flex with an FR4 stiffener or two or more separate rigid FR4 boards connected with Flex circuits.
These circuits offer the best of both flexible circuits and rigid boards combined in one PCB.

Rigid-Flex boards are often considered by designers to be the ultimate solution for making use of available packaging space. They will have lower component and assembly costs so can reduce the overall cost of the final product.

Rigid Flex Printed Circuit - Capabilities
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Item Sample (Order Area <3m2) Batch (Order Area ≥3m2)
Material    
Tg170 S1000-2M, IT180A S1000-2M, IT180A
Hi-Tg FR4 (halogen-free) S1165 S1165
Hi-speed material: needs review needs review
Structure 1+n+1 ; 1+1+n+1+1 ; 2+n+2 (needs review)  
F+R (needs review), cu+F+cu (needs review), R+F+R+F+R (needs review), R+F+R R+F+R
Layer ≤18L ≤16L
Board Thickness   0.5-3.2mm 0.5-3.2mm
Copper Thickness   Outer layer 2oz, Inner layer 2oz Outer layer 2oz , Inner layer 2oz
       
Outline      
Processes Rigid Area Single PCB; V-Cut; Breakaway Tab; Breakaway Tab+Stamp Holes; Breakaway Tab+V-Cut; Breakaway Tab+V-Cut+Stamp Holes Single PCB;V-Cut; Breakaway Tab; Breakaway Tab+Stamp Holes; Breakaway Tab+V-Cut; Breakaway Tab+V-Cut+Stamp Holes
Flexible Area Breakaway Tab, Single PCB Breakaway Tab, Single PCB
Tolerance of Size Rigid Area 0.1mm 0.15mm
Flexible Area 0.05mm 0.1mm
       
Drilling      
Drill bit(min) for mechanical drill 0.15(Board Thk≤1.2mm)-6.2mm 0.2-6.2mm
       
The gap between hole wall for different webs (CAF): IPC standard 12mil 12mil
Military standard 16mil 16mil
Hole to trace distance (after compensation) for one lamination 4L-5.5mil; 6L-6.5mil; 8L-7mil; 10L-8mil; 12-18L-10mil 4L-6mil; 6L-7mil; 8L-8mil; 10L-10mil; 12-18L-12mil
       
Surface treatment HASL, HASL lead free, ENIG, Immersion Tin (needs review), Immersion Silver (needs review), OSP, HASL+Gold Finger (needs review), ENIG+Gold Finger, ENEPIG OSP+Gold, Finger (needs review), ENIG+OSP (needs review) HASL, HASL lead free, ENIG, Immersion Tin (needs review), Immersion Silver (needs review), OSP, HASL+Gold Finger(needs review), ENIG+Gold Finger, ENEPIG, OSP+Gold, Finger (needs review), ENIG+OSP (needs review)
Solder Mask Colour Green, Yellow, Black, Blue, Red, White, Matt Green, Matt Black Green, Yellow, Black, Blue, Red, White, Matt Green, Matt Black
Silkscreen Colour White, Yellow, Black White, Yellow, Black