Polyimide PCB has recently made a reputation for itself in the industry due to its versatility and multipurpose application, but FR4 boards continue to dominate the traditional PCB market. It’s not unexpected that numerous firms are interested in polyimide PCB. However, what exactly is a polyimide PCB?
To put it simply, these boards are constructed of plastics that have exceptional temperature endurance and strength. However, manufacturing necessitates using a variety of materials, which influences its type and use.
In this article, we will learn the true definition of polyimide PCB and its types, applications, and differences from traditional FR4 printed circuit boards. But first, what exactly is a polyimide?
What is polyimide?
To fully comprehend what a polyimide is, its chemistry must first be understood. An imide is a functional group composed of two acyl groups linked to nitrogen. Imides are very polar and so have considerable solubility in polar fluids.
Polyimides are synthesized in two phases from dianhydrides and diamines. In the second stage, a polyamic acid created in the first stage is imidized using either a chemical dehydrating agent or heat to generate the polyimide.
Polyimides are thermoplastic materials with a high melt viscosity that require high pressure to mold. KAPTON® films and SKYBOND® molding resins are two examples.
Polyimides can also be thermosetting, which means imide oligomers are crosslinked into a three-dimensional network. PETI® and PMR-15® matrix resins for advanced composites are examples of thermoset polyimides.
Thermoset Polymers
A thermoset polymer is a polyimide (a polymer obtained by irreversibly hardening processes, curing, or simply stating it cannot be melted again). This prevents it from distorting.
Polyimides are slightly more unyielding than other similar materials due to their strength. This isn’t to say they aren’t flexible or can’t be bent; it just takes a little more effort.
Physical Attributes of Polyimides
The color varies depending on the chemical structure, polymerization technique, and monomers. They may be vividly colored if made from highly purified aromatic dianhydrides. M- and p-phenylenediamine, when distilled or sublimed, generate colorless crystals that melt in solution or when exposed to air. Polyimides come in both translucent and opaque varieties.
Chemical Properties of Polyimides
Most substances, including halogenated solvents, alcohols, and hydrocarbons, are resistant to polyimides. They have high creep resistance, which refers to a material’s tendency to slowly distort over time when exposed to high amounts of stress. They can replace high-performance materials like metals in structural applications due to their strength. They also maintain their stability in changing frequencies, temperatures, humidity, and other environmental factors. Here are some of the essential chemical characteristics:
Dielectric
Polyimides are dielectric materials, meaning they conduct electricity poorly or not. High-temperature dielectrics are essential in developing complicated power and electronics systems that must work in harsh environments.
Flexible
Polyimide composites improve the suppleness of the material. Because the material is extremely flexible, it is used to make flexible and rigid-flex (a combination of flexible and stiff boards) printed circuit boards.
Tensile Strength
Despite their flexibility, polyimide materials are highly robust and resistant to crawling. They also resist warping over time. As a result, they’re a great fit for applications that require a lot of physical strength.
Thermal Stability
When subjected to a range of temperatures, polyimides remain stable. They can operate at temperatures as high as 260 degrees Celsius. They’re also good thermal conductors, allowing them to endure heat damage during production or maintenance.
Chemical Resistance
Polyimides are vital in applications that require exposure to harsh chemicals because they are chemically stable and can withstand a wide range of corrosive substances.
Durability
PCBs made of polyimide can withstand a lot of physical stress. Despite changes in physical and climatic conditions, they keep their shape.
As a result, they can be utilized in dangerous environments as well as for field repairs.
Polyimide Applications
Polyimides have several advantages that make them suitable for a variety of applications in the industrial, aerospace, and electronics sectors.
- Polyimides are used to produce flexible printed circuits and semiconductors in a variety of ways. They can be used as micronized circuitry support film or as high-temperature adhesives.
- They are utilized as an insulating layer in electronic cable manufacture and varnishes and wire enamels for electric motors.
- Polyimide composites can replace traditional materials in aerospace, such as metals in engine parts and inorganic insulation in hulls and fuselages.
- Polyimide fibers are woven into protective gear for firefighters and hot gas filtration bags in power plants and cement kilns to catch particulates in severe processing settings.
- Polyimide foams are used in aircraft and marine vessels for lightweight acoustic and thermal insulation.
What Is Polyimide PCB?
To grasp the true meaning of polyimide PCB, you must first understand the term “polyimide.”
Polyimide comprises two sub-words: ‘poly,’ which usually refers to polymers, and ‘imide,’ which refers to advanced imide monomers. They form a polymer group that is quite varied.
Furthermore, either a natural or synthetic technique creates the polymer group. For the time being, ignore natural polymers and concentrate on synthetic Polyimides. Polyimide PCBs are made from these polyimides.
Synthetic polyimide is made from various compounds with imide structures and is used to make PCBs. Polymerizing is the term we use to describe this industrial process. PCBs are then made from these polyimides.
Types Of Polyimide PCBs
PCBs made of polyimide can withstand a lot of physical stress. Despite changes in physical and climatic conditions, they keep their shape. As a result, they can be used in hostile settings and for field repairs.
Pure Polyimide
This is the most basic PCB, with no extra features like brominated flame retardants. While most materials are “lacking,” pure polyimide has been described as “lacking.” It is exceptionally sturdy due to the lack of flame retardants while remaining flexible enough to be used in various electrical and communication devices. Because of its helpful flexibility, polyimide is also referred to as polyimide flex PCB.
Pure polyimides are the most common polyimide PCB type while being the oldest. It is made feasible by the great resistance to temperature fluctuation and thermal stability in harsh conditions.
Third-Generation Polyimide.
It’s a more modern variant of pure polyimides. It also contains additional ingredients that make it more flammability resistant. The flammability resistance is critical since it aids in the prevention of electrical fires.
The 3rd generation polyimide, on the other hand, lacks the heat stability of pure polyamides, which could be a disadvantage. It is, on the contrary, simple to construct, allowing the production line to move more quickly than any other polyimide flexible PCB.
As a result, the 3rd generation of polyimide can be produced in large quantities, a significant advantage.
Filled Polyimide
Because it contains many filler elements, this polyimide is similar to multilayer PCBs. The extra filler helps to reduce resin shrinkage.
Resin shrinkage resistance is crucial because shrinkage causes many printed circuit boards to become fragile and split during the drilling and curing processes. The filled polyimide’s shrinkage resistance also aids in its long-term use.
Low-Flow Polyimide
Low-flow polyimides do not have the same flexibility as standard PCBs. As a result, it’s also known as the rigid polyimide PCB.
When PCBs require stiffness to stay robust throughout tough conditions, the low-flow PCB’s rigidity comes in handy. When standard flexible PCBs fail, low-flow polyimides step forward to help solve the problem.
Advantages of Polyimide PCB
Because polyimide PCBs are a unique form of the printed circuit board, they are only employed in rare circumstances. So knowing when to use the polyimide PCB and when not to would be beneficial. When one or more of the following properties are required, use polyimide PCBs:
High Flexibility
PCBs have guaranteed stability and flexibility, one of the most significant advantages of employing polyimide. Furthermore, when these two characteristics are combined, regular polymers outperform regular polyimides in most PCB applications.
Chemical Reaction Resistant
The majority of polyimides are chemically robust. As a result, when exposed to harsh chemical conditions, they show little or no corrosion. As a result, you’ll be able to run your machine freely if it’s exposed to chemicals.
Heat Resistant
Polyimides are extremely heat resistant and can be employed in various climates and conditions. They may work at temperatures as high as 260 degrees Celsius, which is usually not pleasant. They have a very high thermal expansion. It permits them to withstand heat-related damage during the manufacturing and maintenance processes.
High Chemical Resistance
Polyimides’ chemical stability allows them to withstand a wide spectrum of corrosive substances without degrading. This is particularly significant in activities involving chemical contact.
Excellent Durability
Polyimide PCBs can endure physical force in addition to chemical and heat resistance. Furthermore, physical and temperature elements do not affect their shape, making them ideal for operations that require harsh environments and quick maintenance. Polyimides also have great electrical properties, making them suitable for PCB foundations.
Versatile Usage of Polyimide PCB
Polyimide rigid PCBs and polyimide flexible PCBs are widely employed in various sectors. The following are some of the most common applications for polyimide printed circuit boards:
Computer and Laptops
The components in today’s laptops and computers are subjected to high-temperature increases due to heavy use. As a result, the thermal conductivity of polyimide PCBs is advantageous for laptops and PCs.
The flexibility and rigidity of these circuit boards also contribute to the computers’ overall durability.
Automotive Electronics
Out of all electronic components, automotive electronics confront the most challenging conditions. They must perform in extreme cold and heat and with constant shaking of many components.
Naturally, these automobile components necessitate a long-lasting PCB, which only polyimide can provide.
Military and Aerospace
Electronics utilized in the military and aerospace industries are likewise exposed to harsh environments. Explosions and space adventures are two examples. Even though Polyimide PCBs are not transparent, their longevity and resistance to chemical and thermal conduction help to ensure that operations are not disrupted under adverse conditions.
Furthermore, the tensile strength of PCBs improves the safety of the related personnel and other machine components.
Medical Industry
In comparison to other businesses, most medical electronics have specific requirements. Polyimides are also appropriate for treatments and diagnosis processes such as implants, prosthetics, and sophisticated imaging because they require high and efficient applications. Polyimide PCB lamination processes are a good fit for such applications in this situation.
Furthermore, because these medical electronics are used in harsh conditions, they are prone to failure. They must also be light and unaffected by signal interference. As a result, polyimide PCB is the only viable solution.
What are the differences between PCB and FR4 materials?
When comparing PCB and FR4 materials, it’s important to remember that FR4 does not refer to a specific material. Instead, FR4 refers to a material grade and is used as a PCB substrate. FR4 relates to a flame-resistant material developed by the National Electrical Manufacturers Association (NEMA). As a result, whenever you read FR4, it simply signifies that the material has passed all of the UL94V-0 compliance tests.
FR4 grade materials are made from laminated fiberglass, unlike polyimide PCB, which is made from synthetic polyimide. Melting raw glass components and converting them to Fiber yarn filaments constitutes the production of FR4 grade materials.
Manufacturers then braided everything together and treated it with an accoupling chemical and glue to help it stick. After the adhesive process is complete, the board is coated with copper foil, and the end product is used to produce PCB materials.
FR4 circuit boards are very sturdy due to the epoxy glass resin and laminated copper utilized in their manufacture. This explains why PCBs are more flexible than FR4 materials. Compared to FR4, polyimide PCB materials are also more robust and lightweight.
When comparing the heat and chemical resistance of FR4 with polyimide PCBs, the latter always comes out on top. On the other hand, Polyimide PCBs are more expensive than FR4s, owing to their longevity and extensive use. As a result, the equation is balanced.
Conclusion
Polyimide PCBs can be used in a wide range of applications. It is, in fact, due to its qualities. In addition, the FR4 material is a viable choice. However, you must choose the best option that best suits your board’s needs.
For more details on Polyimide, contact us at ICRFQ, we manufacture the best electrical PCB together with other electrical components in China.
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