Arlon polyimide is an electrical insulating polymer film applied to the surface of PCBs. Polyimide films are essential in high-reliability electronic assemblies. They have low dielectric attenuation and excellent dielectric strength. In addition, the polyimide provides a protective coating against moisture, abrasion, and extraneous materials.
Arlon Polyimide is a pressed film with strong electromagnetic properties. As a result, we can paint it on most substrates. For example, we can apply it to the surface of printed circuit boards (PCBs) as an electrically insulating film topcoat. Then we apply it in a conductive coating through roll-to-roll printing processes.
Arlon Polyimide offers thermal stability and excellent moisture resistance, ideal for high-temperature applications. In addition, the material has low dielectric attenuation and excellent dielectric strength. It can withstand temperatures up to. As a result, polyimide has many advantages over other electrically insulating materials. Some of them include manufacturing cost, performance, and environmental impact.
1) Moisture protection
Many types of polyimides have excellent resistance to moisture absorption or adsorption. For example, Arlon polyimide can help produce high-reliability electronic devices. It can withstand moisture from human skin, hand oils, rain, and snow. In addition, Arlon polymer prevents moisture and helps avoid corona effects on the contacts. It also reduces the shortening of circuit life.
2) Corrosion resistance
The Arlon polymer has excellent resistance to a wide range of chemicals. It is also applicable in many industrial processes which are corrosive to metals.
3) Electrical insulation
The Arlon polymer has a very low loss factor (near zero) in its dielectric regime. This permits very high-speed avalanches in properly designed circuits. As a result, it keeps the transmission of electromagnetic signals at acceptable levels.
4) Thermal stability
The Arlon polymer is resistant to many high temperatures and accelerated aging processes. In addition, we maintain its insulative properties up to the maximum temperature of 200 °C (Tg = 350 °C) in air.
5) Mechanical and abrasion resistance
The polyimide offers physical stability and protection of the circuit board and electrical insulation. It also provides a moisture-resistant seal on the board. In addition, the Arlon polyimide has excellent abrasion resistance. Finally, it helps protect the printed circuit edge connectors against wear during insertion and removal. A good example is in computer servers.
An Arlon polymer film can help as a pressure-seal device. The film acts as a barrier within a gas chamber and produces positive pressure. It eliminates the need for gaskets and other sealing devices.
7) Surface smoothness and appearance
The Arlon polymer provides electrical insulation, yet it is also very smooth on the surface of the circuit board. As a result, it has a very low coefficient of friction with plastics, enabling high-speed operation in integrated circuits (ICs). In addition, the film is very easy to apply because it adheres to the surface easily.
We apply Arlon material to PCBs by vacuum deposition or immersion.
The complex nature of polyimides means that there are many variants and manufacturer sources. In addition, the electrical, thermal, physical, and mechanical properties vary widely. However, it depends on the manufacturing process. These variations make it highly desirable to know the source of a polyimide film. In addition, it provides details of its properties and potential use in an assembly or system.
a) Cold Supply Chain:
The cold supply chain is the most typical. We refer to it in standards used by certification organizations such as Rayming PCB & Assembly, UL, CSA, or VDE. This indicates how the material should behave in use. For example, we should manufacture the film using a process specified in the standard. You should not deviate from it without due consideration of the consequences. Manufacturers that provide films to the standard will indicate this with a specification number such as X5R or Y5V.
b) Electrical Insulation, Conduction, and EMI Shielding
Polyimide films are helpful in a wide spectrum of applications. While the standard method of specifying thermal and electrical properties is by using the dielectric constant, this may not be sufficient as a specification. Other key electrical considerations include:
1) Electrical breakdown voltage – The film must withstand the transverse AC and DC voltages applied to it when used in an assembly.
2) DC resistance – This indicates the resistivity of the polyimide. It is essential for many applications. This affects current conduction, heating capability, and self-heating on exposure to high AC voltages, circuit inductance, etc.
c) Mechanical Fastening:
The mechanical fastening of the film to a PCB may be through solderability or pressure adhesive. Pressure adhesives sometimes help to seal sensitive components in industrial assemblies. However, they will exhibit different properties than the adhesive used for a surface mount component that we would not expose in the same manner.
d) Press Pads
Press pads help ensure good electrical and mechanical contact between two surfaces in many applications. These pads may help to block off components, prevent them from moving, or may need to be flexible. In addition, it allows the relative position of the components to change. Polyimide films are available with properties that make them suitable for press pads. These include:
1) Friction – Manufacturers will specify a value in Shore A (with a range indicated). It indicates the coefficient of friction between the polyimide and the material pressed against it. In most cases, it is typically plastic. The lower this number is, the smoother and less resistant to motion the polyimide film will be when pressing two objects together.
2) Pressure Sensitivity – The material will be sensitive to pressure, and so the manufacturers will specify a pressure value at which the film deforms. This can be a force applied to a specific area of the film or an overall material thickness value. Manufacturers often also specify a force required to move an object pressed against the film.
3) Press Pad Size – When manufacturing press pads, you need to account for several issues when selecting a polyimide film:
• Firmness – A good press pad will display sufficient rigidity to not deform under load from any moving parts or electrical contacts.
e) Thermal Solutions:
Polyimide films are suitable for applications that need thermal isolation and cross-linking of two dissimilar materials. Typically they help in the following types of applications:
Heat transfer devices such as wafer driers, chiller heads, and condensers
Electrical interconnect boards
Heat sinks and radiators
f) Vacuum Bagging:
Polyimide films are often vacuum-bagged at the factory. This helps to maintain their mechanical properties during production.
g) Sheets and Rods:
Polyimide film is also available in a sheet or rod form suitable for use as an adhesive on PCBs, circuit boards, and other surfaces.
Arlon electronic materials meet the highest standards and are suitable for most applications. They meet all the requirements necessary to be certified and used in electronic devices, appliances, and industrial equipment. The number of manufacturers providing Arlon materials increases with suppliers worldwide. They include many new ones appearing on the market in recent years. Polyimide is a highly promising material for many applications due to its wide range of properties and versatility.
A polyimide film can also consist of polyamic acid (PA) or polyamic polyamide (PAPA). The long chains of PA satisfy the chemical requirements of the polymerization reaction. First, two equivalents of ammonia plus one acetylene equivalent react with a maximum of four ethylene glycol in the presence of a catalyst to produce the imides. We then polymerize it with water in the presence of an acid catalyst.