In the modern electronics industry, miniaturized products are essential for some applications such as wearable electronics devices, medical applications, and space applications. Hence comes the polyimide PCB, which has recently made its reputation because of its versatility and multifunctional use cases. Even though FR4 PCBs are a more popular option for conventional applications, numerous electronics manufacturers are growing their interest in polyimide PCB for specific applications.
What exactly is polyimide PCB?
There are some great resources from PCB experts in the industry to be found online. Polyimide material is a thermoset polymer with high melt viscosity that needs high pressure to mold. Polyimide is a polymer produced by curing or irreversible hardening processes. Hence polyimide PCB can not be melted again, in other words, polyimide PCB is resistant to warping. Polyimide materials are considered stronger and more unyielding than other similar materials. However, this does not make polyimide flexible or safe from bent, it takes more force to distort it.
It is significant to understand the chemistry behind polyimide. It is made of two distinct words: poly and imide. Poly linked to polymers and imide is a functional group composed of two acyls related to nitrogen. Imides have considerable solubility since they are known to be very polar. It can also be thermosetting as imide oligomers are crosslinked into a three-dimensional network.
What types of Polyimide PCBs are manufactured?
Just like ceramic and metal PCB, polyimide PCBs come in multiple types. This classification is made when you determine the type of material used in the synthesis of the polyimide or amide polymer. Polyimide PCBs come in various types.
Second Generation Polyimide (Pure Polyimide)
These are the simplest kind of second generation which deprive of any additional features like brominated flame retardants. Make no mistake, the lack of this feature has modified the capabilities of these PCBs in a positive way; the absence of flame retardants ensures stability along with a certain level of flexibility. This property makes it ideal for various types of electrical and communication devices. This type of polyimide is also called polyimide flex PCB(FPCB) because of its flexibility.
Even though polyimide flex PCB is one of the oldest among all polyimide PCB types, it is ideal for certain applications because of its endurance against the thermally unstable environment.
Third Generation Polyimide
This is a more advanced version of flex polyimide PCB. Moreover, it consists of additives that improve its flammability resistance. This property makes such PCBs best suitable for electronic devices for stopping fires that accidentally started, such as fire alarms.
This third-generation Polyimide PCB does not have the thermal stability of pure polyimide, which is a major disadvantage. On the contrary, manufacturing such PCBs is quite easy, as their production is propelled faster.
Low-flow polyimides do not have the flexibility of the standard PCBs and are called rigid polyimide PCB. This rigidity is required when PCB stiffness and strength are crucial, especially in harsh environments. Where traditional flexible PCBs fail, low-flow polyimides withstand many challenging situations.
This polyimide is considered similar to multilayer PCBs as it contains many filler elements. 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.
What are the physical attributes of Polyimide PCBs?
Resistance against heat:
Polyimide PCB shows immense thermal stability in a wide range of temperatures. It has durability up to 260° C. Such high thermal stability is because of their high thermal expansion, which allows them to withstand high temperatures during the manufacturing and rework process.
High Chemical resistance:
Since polyimide PCBs have increased durability from various chemicals, they are ideal for applications with higher chemical exposure. It also makes them resistant to corrosion from any chemical reactions.
High Tensile strength:
Polyimide PCBs show high resistance to warping as they are very robust materials with higher crawl resistance. Hence polyimide PCB is best suitable for applications that need higher durability in harsh environments.
Even though polyimide PCBs are robust, they are flexible as well. This combination of higher tensile strength and flexibility makes them superior to conventional PCBs.
Because of polyimide PCBs’ strong resistance against harsh temperatures and chemical conditions, Thermal, physical, or chemical stress has no major effects on them. Hence, polyimide PCBs are ideal for applications in nuclear plants, the military, or aerospace.
What are the best-suited application fields for polyimide PCBs?
Aerospace and military applications:
PCBs accommodated in aerospace and military devices need to endure harsh environments. Space travel exposes devices and PCB to high temperatures and radiation. Polyimide PCB with their longevity and resistance to chemical and thermal conduction make sure that desired operation is not interrupted in adverse conditions.
Nuclear plants are required to have redundant communication and monitoring systems in case of accidents. Such a system needs to be robust for harsh conditions. Polyimide PCB is well suited to fill up those requirements.
Medical supplication has some specific requirements such as longevity and flexibility. Polyimide PCB is ideal for it. Polyimide PCBs assure high and efficient performance when it comes to implants, prosthetics, and other medical devices.
Moreover, many medical electronic devices are used in adverse conditions and need to be prone to failure. It should be light weighted and show endurance from interference. Polyimide PCB ticks all these boxes.
Out of all these applications, automotive is the most challenging because of the presence of various mechanical forces. They are required to be operational in most cold and hot weather conditions. On top of that it demands long-lasting and efficient performance. Only polyimide PCB is the answer to all these challenges.
Supercomputers are designed to carry the most complex task and are required to run for longer times in one go. They are also subjected to high temperatures because of heavy usage. Higher thermal stability and rigidity of polyimide PCBs contribute to the higher performance of such supercomputers.
The growing desire for multilayer FPCBs and demand for rigid-flex FPCBs are growing more and more recently, which will keep on rising in the global FPCB market. As demand for modernized medical, automotive, and electronic devices increases, FPCB will become a more and more popular option among engineers.