What is Teflon PCB?
Teflon PCB, or PTFE PCB, is a high-frequency PCB using polytetrafluoroethylene (PTFE) as its PCB substrate. Teflon PCBs transmit signals of 5GHz and higher frequencies. Teflon is the brand name that the Dupont Corporation uses for its PTFE materials, and it is so well-known that people use Teflon PCB to refer to PTFE substrate PCBs used for microwave and RF applications.
PTFE is white solid at room temperatures, and its melting point is 327℃. Its chemical formula is (C₂F₄)n. PTFE has good resistance to chemicals, electricity, high/low temperatures (-190~260℃), atmospheric aging. And it has the minimum coefficient of friction in plastics. The applications of PTFE include but are not limited to PCB laminates.
Teflon PCB laminates are not pure PTFE but PTFE-based composites, because PTFE is lubricating and uneasy for copper layers to bond, and its stiffness and thermal resistance need reinforcing. Ceramics, glass fiber, glass, or woven glass are added to PTFE to reinforce the Teflon PCB substrate.
Properties of Teflon PCB
A Teflon PCB board has great mechanical, thermal, and electrical properties. This board is used in applications demanding high frequency and high temperature. Below are some of the properties of this printed circuit board;
Great chemical resistance: This material has the ability to withstand chemicals. When exposed to chemicals, oils, and grease, its original properties don’t alter. PTFE boards can be used in a chemical reagent environment.
Low temperature resistance: Teflon PCB material features great mechanical toughness. Even in cases where the temperature reduces to -196 degrees Celsius, it can still maintain 5 percent elongation.
Weather resistance: This is one of the best properties of this material. Teflon PCB can withstand any weather condition. This makes them durable and reliable.
Low dissipation factor: Teflon PCB board offers a low dissipation factor which makes it a good insulator system. This material is ideal for high-performance and high-quality electronic systems. It is ideal in applications like radar systems and radio frequency.
Non-stick: This material is non-adhesive and non-stick. PTFE is a combination of carbon atoms with fluorine atoms attached to every carbon atom. These strong bonds make this material to be unreactive.
Low water absorption: PTFE PCBs can be used in humid environments since they feature low water absorption. This means that this board can withstand moisture.
Exceptional electrical properties: PCB Teflon features low dielectric loss and dielectric constant over a high frequency. This material offers volume resistivity and high breakdown voltage. Its dielectric constant is measured at 2.0.
Teflon PCB Manufacturing
For the production of Teflon circuit boards, extreme attention and carefulness are required. Teflon PCB manufacturers understand that this material is different from FR4 PCB material. For the production of Teflon boards, the following should be considered;
Surface preparation: A substrate’s surface is always prepared for layer formation, marking, and metallization. The manufacturer needs to pay attention to the type of equipment utilized for the preparation of the surface.
For example, things like bristles, scrubbers, and composite brushes should be avoided during the preparation of the surface. These things can disturb the soft laminate. Sodium etchants or plasma gas recycling is used for the preparation of the PTFE surface.
Copper plating: Special care is needed when copper plating ceramic with high dielectric materials. Pure PTFE materials have a high Z-axis coefficient of thermal expansion. Therefore, it is important to utilize plated copper on through-hole walls.
This plated copper must feature high tensile strength. This helps to minimize the chances of pad lifts and barrel cracks.
Solder mask: You must apply the solder mask within 12 hours of etching the material. A Teflon PCB manufacturer must ensure it processes the etched surface via a standard PTFE cycle. You can also clean residual moisture by baking the PTFE laminates before applying a solder mask.
Drilling: This is a new procedure ideal for drilling PTFE substrates covered with copper. Drilling must be utilized with a high chip load. This removes fibers and PTFE tailing. In most cases, PCB fabricators prefer ceramic-filled laminates since they can drill them easily.
Handling and storage: PTFE laminates need extra care since they are soft. This makes them vulnerable to tearing or gouging. It is advisable they are stored at room temperature. They shouldn’t be exposed to sunlight to avoid surface oxidation and contamination.
Lamination: Teflon substrates don’t require oxide pretreatment. PCB fabricators laminate PTFE and copper films at high pressures without bonding films or pre-pegs. Sometimes, PTFE PCB manufacturers use bonding films or prepreg of a very low melting point to minimize the processing temperatures. PTFE-FR4 laminates are ideal in some applications, but they need oxide pretreatment.