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    What is Polyimide in High Frequency PCB?      
   

1.Definition and function of Polyimide

 
  PCB Prototypes
 
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Polyimide is a high-performance polymer material primarily used to fabricate the flexible circuit layers of flexible PCBs or as the base material for the "flexible sections" in rigid-flex PCBs. In Rigid-Flex PCBs, polyimide is commonly employed as the substrate for the flexible circuit portions due to its flexibility and high-temperature resistance, which meet the demands of complex wiring and dynamic bending applications.

 

   
         
    2.Key Properties of Polyimide    
   

2.1 High-Temperature Resistance:

Can operate stably in environments ranging from 200–400°C, with certain grades capable of withstanding even higher temperatures.

 

2.2 Chemical Resistance:

Exhibits strong resistance to acids, alkalis, organic solvents, and other corrosive substances.

 

2.3 Exceptional Mechanical Performance:

Combines high flexibility, wear resistance, and tensile strength.

 

2.4 Excellent Electrical Insulation:

Low dielectric constant makes it suitable for high-frequency circuit applications.

   
         
   

3.Applications of Polyimide

   
   

3.1 Electronics Industry:

Used as the base material for flexible printed circuits (FPCs) in smartphones, wearables, and other applications requiring flexible circuitry; also utilized in copper-clad laminates, insulating layers, and adhesives.

 

3.2 Aerospace:

Manufactures high-temperature-resistant components, insulating materials, and composite structures.

 

3.3 Other Fields:

Widely applied in automotive, medical devices, and semiconductor packaging (e.g., high-temperature tapes, coating materials).

   
         
    4. Merits of R-F777 Polyimide and S1000-2M FR-4 PCB    
   

When it comes to Polyimide, we have to mention Rigid Flex PCB. Let's take the 14-Layer R-F777 Polyimide and S1000- 2M FR-4 PCB as an example to conduct an advantage analysis.

 

4.1 Outstanding High-Temperature Resistance

This PCB material incorporates Polyimide, and the Tg value of the board material reaches 170. This demonstrates its ability to maintain stable performance in high-temperature environments, fulfilling the demands of application scenarios requiring high heat resistance.

 

4.2 Rigid-Flex Design Advantages

With a board thickness combining a 2.0mm rigid part and a 0.21mm flexible part (Rigid-Flex PCB), it balances rigid support and flexible bending properties. This makes it suitable for complex electronic devices with strict requirements for spatial layout and structural flexibility.

 

4.3 Superior Surface Finishing

Using the Immersion Gold surface finish, the gold thickness reaches 0.03μm (minimum), and the nickel thickness is 24μm. These parameters effectively enhance the electrical conductivity, corrosion resistance, and soldering reliability of electrical connections.

 

4.4 Compliant Flame-Retardant Performance

With a flammability rating of 94-V0, it meets the stringent fire-safety requirements for electronic devices, reducing fire risks during operation.

 

4.5 Robust Reliability Verification

It has passed the Thermal Shock Test (-25℃±125, 1,000 cycles) and Thermal Stress Test (300±5, 10 seconds, 3 cycles, with no delamination or blistering). These results prove its structural stability under extreme temperature fluctuations and strong durability.

   
         
   

4-1. 14-Layer R-F777 Polyimide and S1000- 2M FR-4 PCB

   
       
         
   

4-2. Detailed Technical Parameter Table

   
   

Size of Flex-Rigid PCB

238mm x 42mm=1 PCS

Number of Layers

14

Board Type

Rigid-Flex PCB

Board Thickness

2.0mm -Rigid, 0.21mm - flex

Board Material

FR-4 / Polyimide 3mil

Board Material Supplier

Shengyi / Panasonic

Tg Value of Board Material

 170

PTH Cu thickness

20 µm

Inner Iayer Cu thicknes

18 µm

Surface Cu thickness

35 µm

Coverlay Colour

Yellow coverlay / Green solder mask

Number of Coverlay

2

Thickness of Coverlay

25 µm

Stiffener Material

N/A

Stiffener Thickness

N/A

Type of Silkscreen Ink

IJR-4000 MW300

Supplier of Silkscreen

TAIYO

Color of Silkscreen

White

Number of Silkscreen

1

Peeling test of Coverlay

No peelable

Legend Adhesion

3M 90 No peeling after Min. 3 times test

Surface Finish

Immersion Gold

Thickness of Surface Finish

Au: 0.03µm(Min.); Ni 2-4µm

RoHS Required

Yes

Famability

94-V0

Thermal Shock Test

Pass, -25±125, 1000 cycles.

Thermal Stress

Pass, 300±5,10 seconds, 3 cycles. No delamination, no blistering.

Function

100% Pass electrical test

Workmanship

Compliance with IPC-A-600H & IPC-6013C Class 3

Impedance Control

Required impedance, Ohm

Layer

Reference layer

 

 

 

 

 

Single ended impedance (Z0) 40±10%

TOP

IN1

 

 

IN3

IN2/IN4

 

 

IN6

IN5/IN7

 

 

IN8

IN7/IN9

 

 

IN10

IN9/IN11

 

 

BOT

IN12

 

Single ended impedance (Z0) 50±10%

TOP

IN1

 

 

IN3

IN2/IN4

 

 

IN6

IN5/IN7

 

 

IN8

IN7/IN9

 

 

BOT

IN12

 

Single ended impedance (Z0) 50±10%

IN6 (flex part)

IN7 (flex part)

 

Differential impedance (Zdiff) 80±10%

TOP

IN1

 

 

IN3

IN2/IN4

 

 

IN8

IN7/IN9

 

 

IN10

IN9/IN11

 

Differential impedance (Zdiff) 100±10%

TOP

IN1

 

 

IN3

IN2/IN4

 

 

IN6

IN5/IN7

 

 

BOT

IN12

 

Differential impedance (Zdiff) 100±10%

IN6 (flex part)

IN7 (flex part)

   
         
    5. Recap    
   

Polyimide is not just a simple material choice; it is the key to breaking through the performance bottlenecks of high-frequency PCBs. With its molecular-level precision structure, it reduces signal distortion to the minimum, turning the dream of high-speed transmission into reality.

 

   
         
   

Founded in 2003, Shenzhen Bicheng Electronics Technology Co., Ltd is an established high frequency PCB supplier and exporter in Shenzhen, China, serving customers worldwide.

 

We are devoted to delivering high-frequency PCB products and solutions of the highest quality, along with customized service. Feel free to consult and contant at any time !

 

Visit https://www.bicheng-enterprise.com to learn more.

Unlock its full potential by contacting Vicky at v.xie@bichengpcb.com.

   
         
         
         
       
       
           
   
 
                                     
       
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