Kraft Paper for PCB – Superior Insulation & Stability
High-temperature resistant saturated kraft paper for PCB is mainly made from softwood pulp and produced under controlled temperature and humidity using a urea-based process. Through resin impregnation, surface coating, and fiber modification, it achieves excellent heat resistance. Compared with regular kraft paper, its production process and material formulation are more precise, allowing the paper to maintain stable performance even after 1,000 hours at 150 °C. Tested with constant-temperature ovens, tensile testers, and tear-strength instruments, this paper withstands temperatures of 220–230 °C and finds wide applications in PCB processing, thermal insulation, and high-pressure lamination under demanding conditions.
PCB Kraft Paper: Core Role – Insulation & Circuit Stability
What is PCB?
PCB (Printed Circuit Board) acts as the “carrier of electronic components,” with copper traces etched on an insulating substrate that actively connect chips, resistors, capacitors, and other components. As a result, it forms the backbone of electronic devices. Consequently, PCBs appear in a wide range of applications, including smartphones, computers, home appliances, automotive electronics, and more.
The Core Role of Kraft Paper in PCB: Electrical Insulation “Safety Barrier”
In PCB production, kraft paper mainly functions as interlayer insulation and edge protection. Its key strength lies in its excellent insulation performance, which delivers three main benefits:
- Preventing Short Circuits: It effectively isolates copper traces at different potentials, stopping leakage currents and protecting the device’s operation.
- Mechanical Protection: During lamination, kraft paper cushions the layers, reducing friction between copper foil and substrate and improving PCB yield.
- Heat Dissipation: Its natural fiber porosity helps dissipate localized heat during operation, preventing accelerated aging of components and extending PCB lifespan.
Why Insulation Performance is Critical for PCB Kraft Paper
- PCB circuits typically operate at 5–220 V. Poor insulation can cause leakage or dielectric breakdown.
- Low insulation resistance → current leakage, device malfunction.
- High dielectric loss → excessive heat, reducing PCB lifespan.
- High-quality PCB kraft paper offers insulation resistance of 10¹²–10¹⁴ Ω (dry conditions) and dielectric loss ≤0.05, fully meeting PCB insulation requirements and eliminating safety risks.
PCB Kraft Paper: Applications – Insulation Layers & Buffer Pads
PCB Interlayer Insulation
Kraft paper for PCB does more than just support the board itself; it actively fulfills multiple critical roles in electronic insulation. Thanks to its reliable insulation and flexible processing, it serves as a foundational material in electronic component production. For example, in multilayer PCB manufacturing—such as 2-layer or 4-layer boards—manufacturers place kraft paper between copper layers. This placement not only ensures excellent insulation to prevent interlayer short circuits but also takes advantage of its lightweight design (e.g., 80 g/m²), which adds minimal thickness and supports the growing trend toward slimmer, lighter electronic devices.
Battery Packaging Insulation
PCB kraft paper functions as an insulating cushion for lithium-ion and button batteries, including those in phones or power banks. It not only provides reliable insulation but also offers high flexibility, allowing it to conform to curved battery shells without cracking. Additionally, because it is made from pure plant fibers, the material remains odorless and eco-friendly, fully meeting battery safety and environmental standards.
Electronic Component Insulation Pads
It also insulates small components like resistors, capacitors, and inductors from the PCB substrate. Its flexibility allows precise cutting into small sizes (e.g., 5×5 mm, 10×10 mm) without generating dust or waste, making assembly easier and more efficient while perfectly matching component specifications.
Specifications PCB Kraft Paper
| Specification | Parameter Range | Suitable Applications |
| Size | Sheets: A4 (210×297 mm), A3 (297×420 mm); Rolls: Width 1220 mm / 1530 mm, Length 500–1000 m | Sheets for small-batch PCB production; rolls for automated assembly lines |
| Basis Weight | 80 g/m², 100 g/m², 120 g/m², 150 g/m² | 80–100 g/m² for thin PCBs; 120–150 g/m² for thick PCBs |
| Color | Natural (brown-yellow, high fiber purity), White (bleached softwood pulp, for aesthetic requirements) | Natural is standard; white suits visible PCB insulation layers |
| Insulation Properties | Insulation resistance ≥10¹² Ω (23 °C, 50% RH); dielectric loss ≤0.05 (1 kHz); breakdown voltage ≥15 kV/mm | Meets insulation standards for consumer electronics and household PCBs |
Achieve Insulation & Stability: Materials & Process
Raw Materials: Choosing the Right Fibers to Ensure Insulation
High-purity softwood pulp forms the foundation of PCB kraft paper, minimizing impurities that could compromise insulation. Key requirements:
Why It Matters: Using recycled pulp or contaminated fibers can reduce insulation resistance by 50–70%, failing PCB insulation requirements.
Pulp Type: Mainly pine pulp (fiber purity ≥99.8%) and spruce pulp; 100% softwood, no hardwood added.
Selection Standards: Fibers must be free of oil, metal particles (e.g., iron filings, copper powder), with ash content ≤0.05%—impurities can drastically lower insulation resistance.
Production Process: Precise Control of Insulation Properties
PCB kraft paper undergoes a full process of purification → forming → drying → inspection to ensure stable insulation performance. Core equipment and parameters:
| Production Stage | Key Equipment | Process Parameters | Insulation Control Points |
|---|---|---|---|
| Pulp Purification | High-frequency de-impurifier, fiber screen | Impurity removal precision ≤0.1 mm, screening efficiency ≥99% | Removes metal/plastic particles to prevent conductive paths |
| Paper Forming | Long-wire paper machine (no metal contact) | Forming speed 280–350 m/min | Ensures uniform fiber distribution; prevents local impurity clusters that affect insulation |
| Pressing & Drying | Multi-roll press, low-temperature drying cylinder | Pressure 150–200 kPa, drying 90–100 °C | Low-temp drying avoids fiber brittleness, keeps fibers pure, prevents high-temp contamination |
| Insulation Testing | Insulation resistance tester, dielectric loss meter | Sample every 10 min, insulation resistance ≥10¹² Ω | Real-time monitoring; nonconforming sheets are immediately removed |
Quality Control: Dual Verification from Raw Material to Finished Product
Raw Material Inspection: Every batch of pulp is tested for insulation resistance (soaked ≥10¹¹ Ω). Nonconforming pulp is rejected.
Finished Product Sampling: For each roll of PCB kraft paper, 5 samples are tested for insulation resistance and dielectric loss. Only batches meeting the standards are released for shipment.
PCB Kraft Paper vs Traditional Materials: 5 Key Advantages
| Comparison Dimension | PCB Kraft Paper | Traditional Epoxy Board | Traditional Polyimide Film |
|---|---|---|---|
| Cost Efficiency | Low unit price (≈1.2–2 CNY/㎡), ~60% cheaper than epoxy board | High unit price (≈3–5 CNY/㎡) | Very high unit price (≈8–12 CNY/㎡), highest cost |
| Processing Convenience | Easy to cut and fold; suitable for manual or machine processing; dust-free | Brittle and hard; requires specialized cutting equipment; generates dust | Flexible but scratch-prone; processing requires anti-stick measures |
| Environmental Friendliness | 100% plant fibers; biodegradable (≤180 days) | Non-biodegradable; generates industrial waste | Hard to degrade; high recycling cost |
| Size Flexibility | Supports A4 sheets and rolls (width 1220–1530 mm); cutting with minimal waste | Standard sizes only (e.g., 300×400 mm); custom sizes costly | Mainly rolls; width limited (≤1000 mm) |
| Weight Adaptability | Lightweight (80 g/㎡ sheet weighs 80 g); reduces overall PCB weight | Heavy (1 mm thick sheet weighs 1.8 kg); increases equipment load | Thin (0.1 mm thick sheet weighs 120 g); light but costly |
Key Conclusion: PCB kraft paper delivers “compliant performance at optimal cost” in low-to-medium voltage PCB insulation scenarios (such as home appliance and consumer electronics PCBs), offering a cost-performance ratio far superior to traditional materials.
Choosing PCB Kraft Paper: Quality (Insulation) & Customization
- Stable Supply: With a daily production capacity of 300 tons, we maintain ample stock of standard specifications (A4 sheets, 1220mm rolls). For customized requirements—such as special grammage or widths—we can deliver within 7 days, effectively preventing “out-of-stock” situations during peak seasons.
- Transparent Testing: Every batch includes an Insulation Performance Test Report, showing raw data for insulation resistance, dielectric loss factor, and breakdown voltage. This traceability, linked directly to the production team and equipment, makes quality control clear and reliable.
- Compliance Assurance: Our products comply with EU RoHS and China GB/T 26125 environmental standards. As a result, they meet export requirements for electronic devices, for example, ensuring home appliance PCBs destined for Europe fully conform to RoHS regulations.
- Flexible Customization: We offer complete customization across grammage, size, and color. For instance, customers can request 150g/㎡ thick kraft paper for automotive electronics PCBs. In addition, our precise cutting process minimizes waste, further reducing material costs.