ZMS Blog

 ^{Substrate Material}

 ^{Thicker, usually over 0.2mm}

 ^{Signal Integrity}

 ^{Suitable for high-speed and high-frequency signals}

 ^{Affected by bending, high-frequency signals may be slightly worse}

 ^{Impedance Control}

 ^{Much more stable}

 ^{Affected by bending, require specific designs.}

 ^{Heat dissipation}

 ^{Better becuase cooper foil and thicker substrate material}

 ^{Poor because limited by thin substrate}

 ^{Installation way}

 ^{Fix by screw or slot on housing}

 ^Connectors

 ^{Space Utilization}

 ^{Low, limited by the rigid shape}

 ^{High, flexible in 3D structure.}

 ^{Vibration resistance}

 ^{Normal, solder points easy to  Crack}

 ^{Superior, Flexible material helps Shock Absorption}

 ^{Manufacturing Cost}

 ^{Lower, Mature technology, cheaper material cost.}

 ^{Higher, special material, complicated technology}

 ^{Design Difficulty}

 ^{Easy, standard stackup technology}

 ^{Harder, Need to consider bending and lamination issue.}

 ^{Repair difficulty}

 ^{Easier, solder points fixed}

 ^{Harder, Need to be careful for the flexible material, much more easy was damaged.}

 ^{Classic Applications}

 ^{Computer mainboard, power board, LED lighting}

 ^{Mobile phone folder display, camera modules, wearable devices.}

 ^{Application Environment}

 ^{Fixed structure devices, high heat dissipation products.}

 ^{Dynamic bending, light and compact scene}

 ^Features

 ^{Good Tempreture Resistance, able to work long time in environment over 250℃, short time in 400℃;}

^{Excellent Mechanical strength, Chemical resistance and dimensional stability; Good high frequency performance: Dielectric constant about 3.4~3.5, Dissipation Factor 0.002~0.003;}

 ^{Lower manufacturing cost, Good flexibility and bending resistance;}  

^{Poor temperature resistance (long time working tempreture only at 80-150℃)；}

^{DK about ~3.3， DF about ~0.013 (high frequency loss is large)}

 ^{PEN(Ethylene Naphthalate): Performance between PI and PET, tempreture resistance reach 150℃, belong to middle end flexible PCB.}  

 ^{LCP(Liquid Crystal Polymer) : Ultra-low Df ~0.002, Applying to Millimeter wave high frequency.}

 ^{Disadvantages}

 ^{Manufacturing Cost high, Slightly hygroscopic, Moisture-proof treatment is required.}

 ^{Not resistant to high temperature welding, susceptible to acid and alkali corrosion}

 ^Application

 ^{Aerospace, 5G high-frequency circuits, automotive electronics}

 ^{Consumer Electronics such as keyboards film, low-tech display connection cables, etc.}

 ^{5G Antenna}

  ^Features

 ^{Flexible, low cost, with moderate adhesive strength. Temperature resistance is average (long-term 120-150 degrees Celsius).}

 ^{High temperature resistant, capable of long-term operation at 180°C, with high bonding strength. The adhesive layer is relatively thin, suitable for high-density design.}

 ^{Process: Copper foil is directly deposited on PI substrate (e.g., through sputtering or electroplating processes).}

^{Ultra-thin (total thickness can be less than 25 microns), high-temperature resistant, and excellent high-frequency performance (no adhesive layer dielectric loss).}

^{No issues with adhesive layer aging, ensuring high reliability.}

 ^{Disadvantages}

 ^{Susceptible to aging at high temperatures, with a thick adhesive layer that affects high-frequency signals.}

 ^{Fragile, repeated bending easily leads to cracking}

 ^{Manufacturing Cost higher}

 ^Application

 ^{Consumer electronics}

 ^{Rigid-Flex PCB}

 ^{High-frequency high-speed (servers, radar), ultra-thin foldable screen smartphones}

^Techniques

^{Formed by physical rolling followed by annealing treatment}

^{Formed by electrochemical deposition}

^{Improved electrolytic copper, enhanced for better ductility through special processes (approaching rolled copper).}

^Features

^{Dense crystalline structure with excellent flexibility, capable of withstanding over 100,000 bends, low surface roughness, suitable for fine line etching.}  

^{Low cost, higher electrical conductivity (pure copper 99.9%). Surface roughness (requires roughening treatment to enhance adhesion).}

^{Disadvantages}

^{High cost, slightly lower conductivity than electrolytic copper.}

^{Highly brittle, prone to breaking with repeated bending (approximately 10,000 bend cycles).} 

^Application

^{Ideal for high-reliability flexible circuits such as medical devices and wearable electronics.}

^{Static or low-frequency FPCs (such as LED strips)}

^{To balance cost and performance, for mid-to-high-end consumer electronics}

 ^Functions

 ^{Insulation protection: covers exposed copper wiring to prevent oxidation, short circuits, or chemical corrosion.}

^{Mechanical protection: reduces damage to circuits from external friction or bending.}

^{Impedance control: adjusts through dielectric thickness to assist with high-frequency signal impedance matching.}

 ^{Local rigidity support: Increases hardness in specific areas of the FPC (such as connectors, soldering positions) to prevent deformation during insertion, removal, or soldering.}

^{Heat dissipation assistance: Metal stiffeners (such as aluminum sheets) can help with heat conduction.}

^{Thickness compensation: Balances the height difference between the FPC and the connector to ensure stable assembly.}

 ^{Key Specs}

 ^{Thickness: Typically 12.5 to 50 microns (PI cover layer) plus adhesive layer (15 to 25 microns). Temperature resistance: PI cover film > PET cover film > soldermask. Flexibility: PET > PI > soldermask.}

 ^{Design considerations: thickness matching, stiffeners must match the connector tolerance}

 ^{Bonding method: thermoset adhesive or epoxy adhesive, both with high bonding strength and heat resistance}

 ^{Pressure-sensitive adhesive (PSA), can be reworked but has poor long-term reliability}

 ^{Stress control: edges of the reinforcement plate should be chamfered or designed with a gradient to avoid stress concentration that could cause breakage}

 ^{PI Coverlayer}       (Refer below picture)

 ^{Polyimide film + acrylic/epoxy adhesive}

 ^{High temperature resistant (above 260°C), good flexibility, high cost}

 ^{High-frequency, high-temperature environments (5G, automotive)}

 ^{PET coverlayer}

 ^{Polyester film + acrylic adhesive}

 ^{Low cost, poor thermal stability (80~105℃), excellent flexibility}

 ^{Consumer electronics (keyboards, displays)}

 ^{Photoresist solder mask ink}

 ^{Liquid photopolymer resin (UV curing)}

 ^{Can be precisely patterned (lithographic exposure), with a thickness of approximately 10-20 micrometers, but has poor bendability.}

 ^{High-precision circuits such as smartphone cameras}

 ^{Adhesive-free overcoat}

 ^{Pure PI film (bonded by laser or plasma treatment)}

 ^{Ultra-thin (≤12μm), adhesive-free dielectric loss, suitable for high frequency}

 ^{Millimeter-wave radar, satellite communication}

 ^{PI Stiffener}

 ^{Made of the same material as the FPC substrate, with a thermal expansion coefficient that matches, and controllable flexibility (thickness 0.1~0.3mm)}

 ^{Laser cutting, bonding and pressing}

 ^{Flexible area transition (e.g., foldable screen hinge)}

 ^{FR4 Stiffener}

 ^{Epoxy glass fiber board, with high rigidity and low cost, but with significant thickness (0.2~1.0mm)}

 ^{Drilling + gold plating, screw fixation}

 ^{Connectors are fixed, typically used in industrial equipment}

 ^{Stainless/Aluminum Stiffener}

 ^{Metallic rigidity, excellent thermal dissipation performance, but note that insulation treatment is required (e.g., applying Kapton tape), and protection against electromagnetic interference (EMI) is necessary.}

 ^{Stamping forming, adhesive bonding}

 ^{Vehicle-mounted camera module, LED heat dissipation}

 ^{PC(Polycarbonate)}

 ^{Transparent, impact-resistant, but with poor heat resistance (~120°C)}

 ^{Ultrasonic welding}

 ^{Display module backlight area}

^{Core Functions}

^{Insulated protective circuits}

^{Offering partial rigid strength}

^{Material Features}

^{Flexible film / soldermask}

^{Rigid material (PI/FR4/Metal)}

^{Process Technique}

^{Lamination or UV solidation}

^{Punching, laser cutting or adhesive}

^{Main Position}

^{Except solderpads, PI is Covering the whole circuit board.}

^{Only place for connector, soldering area and specific area of PCB.}