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Rigid-Flex Board

More Efficient Advanced Technology & Perfect Solution.

Advantages of Rigid-Flex Board
Nowadays, design is increasingly pursuing miniaturization, low cost and high speed of products, especially in the mobile device market , which usually involves high-density  electronic circuits. Using Rigid-Flex Boards will be an excellent choice for the peripheral devices connected through IO.  Seven major advantages brought by the design requirements of integrating flexible board materials and rigid board materials in the manufacturing process, combining  the 2 substrate materials with prepreg, and then achieving interlayer electrical connection of conductors through through-holes or blind/buried vias are as below:


3D assembly to reduce circuits
Better connection reliability
Reduce the number of components and parts
Better impedance consistency
Can design highly complex  stacking structure
Implement a more streamlined appearance design
Reduce size

A rigid-flex is a board that combines rigidity and flexibility, processing both the rigidity of rigid board and flexibility of flexible board.


Semi FPC


Capability Roadmap

Item Flex ‐ Rigid Regal Semi‐Flex
Figure cv124d cv28nu cv365f
Flexible Material Polyimide FR4 + Coverlay(Polyimide) FR4
Flexible thickness 0.025~0.1mm(Exclude copper) 0.05~0.1mm (Exclude copper) Remained Thickness: 0.25+/‐0.05mm(Dedicated Material: EM825(I))
Bending angle Max 180° Max 180° Max 180°(Flex layer≤2) Max 90°(Flex layer>2)
Flexural Endurance;IPC‐TM‐650,Method 2.4.3. <1000 cycle < 25 cycle NA
Bending Test; 1) Mandrel diam:6.25mm <10K cycle(Bending Angle:180°) <500 cycle(Bending Angle:180°) <10 cycle(Bending Angle:180°)
Application Flex to install & Dynamic(Single side) Flex to install Flex to install


Surface Finish Typical Value Supplier
OSP c1tha 0.2~0.6um;0.2~0.35um Enthone Shikoku chemical
ENIG c2hw6 Au:0.03~0.12um, Ni :2.5~5um ATO tech/Chuang Zhi
Selective ENIG c3893 Au:0.03~0.12um, Ni :2.5~5um ATO tech/Chuang Zhi
ENEPIG c4hiv Au : 0.05~0.125um, Pd : 0.05~0.125um,Ni :5~10um Chuang Zhi
Hard Gold c5mku Au:0.2~1.5um , Ni : min 2.5um Platec
Soft Gold c6kvi Au:0.15~0.5um , Ni : min 2.5um EEJA
Immersion Tin c7nhp Min: 1um Enthone / ATO tech
Immersion Silver c8mhn 0.15~0.45um Macdermid
HASL & Lead free HASL(OS) c9k8n 1~25um Nihon Superior

Au/Ni Type

● Gold plating can be divided into thin gold and thick gold according to thickness. Generally, gold below 4u”(0.41um) is called thin gold, while gold above 4u” is called thick gold. ENIG can only make thin gold, not thick gold. Only gold plating  can make both thin and thick gold. The maximum thickness of thick gold on flexible board can be over 40u”. Thick gold is mainly used in working environments with bonding or wear resistance requirements.

● Gold plating can be divided into soft gold and hard gold by type. Soft gold is ordinary pure gold, while hard gold is cobalt containing gold.  It’s precisely because cobalt is added that the hardness of the gold layer greatly increases exceeding 150HV to meet the wear resistance requirements.

Material Type Properties Supplier
Rigid Material Normal Loss DK>4.2, DF>0.02 NanYa / EMC / TUC / ITEQ / ShengYi / Isola / Doosan etc.
Middle Loss DK>4.1, DF:0.015~0.02 NanYa / EMC / TUC / ITEQ etc.
Low Loss DK:3.8~4.1, DF:0.008~0.015 EMC / NanYa / TUC / Isola / Panasonic etc.
Very Low Loss DK:3.0~3.8, DF:0.004~0.008 EMC / Panasonic / Rogers / TUC / Isola / ITEQ / NanYa etc.
Ultra Low Loss DK<3.0, DF<0.004 Rogers / TUC / ITEQ / Panasonic / Isola etc.
BT Color:White / Black MGC / Hitachi / NanYa / ShengYi etc.
Copper Foil Standard Roughness(RZ)=6.34um NanYa, KB, LCY
RTF Roughness(RZ)=3.08um NanYa, KB, LCY
VLP Roughness(RZ)=2.11um MITSUI, Circuit Foil
HVLP Roughness(RZ)=1.74um MITSUI, Circuit Foil

Material Type Normal DK/DF Low DK/DF
Properties Supplier Properties Supplier
Flex Material FCCL(With ED & RA) Normal Polyimide DK:3.0~3.3 DF:0.006~0.009 Thinflex / Panasonic / Taiflex Modified Polyimide DK:2.8~3.0 DF:0.003~0.007 Thinflex / Taiflex
Coverlay(Black/Yellow) Normal Adhesive DK:3.3~3.6 Df:0.01~0.018 Taiflex / Dupont Modified Adhesive DK:2.8~3.0 DF:0.003~0.006 Taiflex / Arisawa
Bond‐film(Thickness: 15/25/40 um) Normal Epoxy DK:3.6~4.0 DF:0.06 Taiflex / Dupont Modified Epoxy DK:2.4~2.8 DF:0.003~0.005 Taiflex / Arisawa
S/M Ink Solder mask;Color: Green / Blue / Black / White / Yellow / Red Normal Epoxy DK:4.1 DF:0.031 Taiyo / OTC / AMC Modified Epoxy DK:3.2 DF:0.014 Taiyo
Legend ink Screen Color: Black / White / Yellow Inkjet Color: White AMC
Other Materials IMS Insulated Metallic Substrates ( with Al or Cu ) EMC / Ventec
High Thermal Conductive 1.0 / 1.6 / 2.2 (W/M*K) ShengYi / Ventec
EMI Silver foil (SF‐PC6000‐U1 / SF‐PC8600‐C) Tatsuta


High Speed & High Frequency Material (Flexible)

DK Df Material Type
FCCL (Polyimide) 3.0~3.3 0.006~0.009 Panasonic R‐775 series;Thinflex A series;Thinflex W series;Taiflex 2up series
FCCL (Polyimide) 2.8~3.0 0.003~0.007 Thinflex LK series;Taiflex 2FPK series
FCCL (LCP) 2.8~3.0  0.002 Thinflex LC series;Panasonic R‐705T se;Taiflex 2CPK series
Coverlay 3.3~3.6 0.01~0.018 Dupont FR series; Taiflex FGA series; Taiflex FHB series;Taiflex FHK series
Coverlay 2.8~3.0 0.003~0.006 Arisawa C23 series;Taiflex FXU series
Bonding Sheet 3.6~4.0 0.06 Taiflex BT series;Dupont FR series
Bonding Sheet 2.4~2.8 0.003~0.005 Arisawa A23F series;Taiflex BHF series

Back Drill Technology

● Microstrip traces should have no vias, they must be probed from the trace side.
● Trace on the secondary side should be probed from the secondary side(The launch side should be on that side).
● The good design is that stripline traces should be probed from whichever side most reduces the via stub.
● The best results for stripline will be obtained by using short vias that are backdrilled.


Product Application: Automotive radar sensor

Product Details:
4 Layer PCB with hybrid material (Hydrocarbon + Standard FR4)
Stack up: 4L HDI / Asymmetric

High frequency material with Standard FR4 Lamination
Controlled depth drill


Product Application: Automotive radar sensor

Product Details:
4 Layer PCB with hybrid material (Hydrocarbon + Standard FR4)
Stack up: 4L HDI / Asymmetric

High frequency material with Standard FR4 Lamination
Controlled depth drill


Product Application:
Base station

Product Details:
30 Layers (Homogeneous material)
Stack up: High layer count / Symmetric

Registration for each layers
High aspect ratio of PTH
Critical lamination parameter


Product Application:

Product Details:
Stack up: 16 Layers Anylayer
IST Test: Condition:25‐190℃ Time:3 min, 190‐25℃ Time:2min, 1500 Cycles. Resistance change rate≤10%, Test method:IPC‐TM650‐2.6.26. Result: Pass.

Laminating more than 6 times
Laser vias accuracy


Product Application:

Product Details:
Stack up: Cavity
Material: Standard FR4

Using De‐cap technology on Rigid PCB
Registration between layers
Less squeeze out at the step area
Critical beveling process for the G/F


Product Application:
Camera Module / Notebook

Product Details:
Stack up: Cavity
Material: Standard FR4

Using De‐cap technology on Rigid PCB
Critical laser program and parameters in De‐cap process


Product Application:
Automotive lamps

Product Details:
Stack up: IMS / Heatsink
Material: Metal + Glue/Prepreg + PCB

Aluminum base and copper base (single layer)
Thermal conductivity
FR4+ Glue/Prepreg + Al lamination


Great Heat Dissipation

Product Details:
High speed material (Homogeneous)
Stack up: Embedded copper coin / Symmetric

Accuracy of coin dimension
Accuracy of lamination opening
Critical resin flow


Product Application:
Automotive / Industrial / Base station

Product Details:
Internal layer base copper 6OZ
External layer base copper 3OZ/6OZ Stack up:
6OZ copper weight in internal layer

6OZ copper gap filled fullly with epoxy
No drift in lamination processing


Product Application:
Smart phone / SD Card / SSD

Product Details:
Stack up: HDI / Anylayer
Material: Standard FR4

Very low profile/RTF Cu foil
Plating uniformity
High resolution dry film
LDI Exposure (Laser Direct Image)


Product Application:
Communication / SD Card / Optical Module

Product Details:
Stack up: HDI / Anylayer
Material: Standard FR4

None gap at the finger edge when PCB in the plating gold processing
Special resistant film


Product Application:

Product Details:
Stack up: Rigid‐Flex
With Eccobond at Rigid‐Flex transformation

Critical moving speed and depth for shaft
Critical air pressure parameter